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200 Cards in this Set
- Front
- Back
In reference to the partially edentulous arch and accompanying framework shown---what is the Kennedy classification?
Class I, Modification 0 Class II, Modification 1 Class III, Modification 0 Class IV, Modification 0 Does this RPD have an axis of rotation? If so, where is it located? What class(s) of RPDs do not have an axis of rotation? |
The correct answer is 1
According to the Kennedy Classification, the partially edentulous arch shown is a Class I, Modification 0. There are bilateral posterior extension areas with no other modification (edentulous) space(s) present. All class I RPDs have an axis of rotation. To be very specific, the axis of rotation will pass through the rigid metal closest to the edentulous space that lies above the survey line (height of contour). If the design is correct and the laboratory and clinical procedures are carried out properly, the axis of rotation should pass through the most distal rests on each side. The axis of rotation for this case is indicated by the black line. Class I and Class II RPDs always have an axis of rotation. Class III RPDs never have an axis of rotation. Class IV RPDs seldom have an axis of rotation---some people consider that Class IV RPDs have an axis of rotation if all the incisors and both canines are missing, creating an "anterior extension" area. |
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The accompanying figure depicts the lingual surface on the lower anterior teeth of a patient who is currently wearing a bilateral distal extension removable partial denture that was fabricated 5 years ago. What do you think is the most likely cause for the tissue damage that has occurred on tooth #22?
The lower anterior teeth should have been plated and were not. The patient's oral hygiene is poor and tissue breakdown followed pocket formation on the distal of tooth #22. A rest preparation and rest should have been placed on tooth #22. A cast circumferential clasp was used on tooth #22----it should have been wrought wire. |
3
1 INCORRECT. Although plating may help to prevent this situation from occurring, definitive rest seats under the plating would still be required. 2 INCORRECT. Poor oral hygiene can contribute to tissue breakdown. However, this type of damage is caused by trauma from the downward movement of the RPD during function. 3 CORRECT. A rest preparation and rest are essential to proper functioning of the RPD. The damage shown in the illustration is primarily caused by movement of the RPD toward the tissues during function. Such damage would not have occurred if a good rest seat and rest were present. 4 INCORRECT. The type of clasp arm has nothing to do with tissue trauma of this type. |
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Your patient has teeth 20-29 remaining. You plan to use mesial rests and I-bars on both terminal abutments. Because there are lingual tori present, you will need to use linguoplating in the premolar areas. The illustration is a lingual view of teeth 27-29. The dotted line on #29 represents the height of contour (survey line). What should be the relationship of the superior border of the plating and the survey line?
The plating should extend above the survey line. The plating should end at or below the survey line. The plating must end exactly at the survey line. The plating must end below the survey line. |
3
The plating must end exactly at the survey line (height of contour). If the plating ends below the survey line, there will be a space between the superior edge of the plating and the tooth creating a food trap. In addition, the edge of the plating will stand away from the tooth and may be irritating to the tongue. If the plating ends above the survey line, it will pre-empt the mesial rest. The axis of rotation will pass through the plating instead of the rest. The I-bar will contact the tooth in front of this "new" axis of rotation and will engage the tooth when the extension base moves toward the residual ridge. Also, since the plating will act like a rest on an inclined plane, there will be the tendency to push the tooth toward the facial during function. The fact that the plating must end exactly on the survey line makes framework fabrication much more difficult for the laboratory technician. Therefore, whenever possible, avoid plating terminal abutments on distal extension RPDs. |
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In the maxillary class III RPD shown either a palatal strap or an anterior-posterior palatal strap major connector may be used. If an anterior-posterior strap design is to be considered, the opening between the anterior and posterior palatal straps should be at least _______ mm.
5 10 15 20 |
3
Although the exact space required is somewhat arbitrary, we generally feel that the opening should be at least 15 mm. If the opening is less than 15 mm, the benefit gained from uncovering the tissues may be offset by the increased "sensitivity" of the tongue to the multiple major connector borders. |
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Because there are no movable tissues on the palate, the borders of maxillary major connectors may be located farther from the gingival margins than those of mandibular major connectors.
True False |
True
Major connectors on the maxillary arch should be at least 6 mm from the gingival margin. On the mandibular arch, the proximity of movable tissues will not permit this amount of distance. In general, mandibular major connectors should be at least 3 mm from the gingival margin. |
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On the mandibular class III framework shown, circumferential clasps have been used on the canine, premolar, and molars. Which one of the following statements regarding the clasping is TRUE?
The retentive arms on the canine and premolar should be wrought wire while those on the molars should be cast. The lingual arms on the molars are frequently the retentive arms because there are often no usable facial undercuts. If the undercut on the second premolar is on the distofacial, the circumferential retentive arm would most likely be changed to I-bars. In order to ensure adequate retention, the tips of both the buccal and lingual arms on the molars should be placed in undercuts. |
2
Incorrect. All of the clasps should be cast. Since there is no functional movement of a class III RPD, there is no need for the stress-breaking effects of wrought wire clasps. Correct. Lower molars, particularly second or third molars, frequently have no facial undercuts. In addition, the normal drift of the teeth is to the lingual, accentuating lingual undercuts and minimizing facial undercuts. Incorrect. Modified T-bars would be the retainers of choice if the undercuts were on the distofacial. I-bars could be used but the tiny space between the I-bars and the denture base would create food traps and would make the plastic very difficult to finish properly. In addition, the I-bars would tend to be very short and inflexible. Incorrect. Only one arm of each clasp assembly should extend into an undercut (be retentive). The other arm must be rigid to provide bracing or reciprocation and thus cannot extend into an undercut and provide retention. |
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On the RPD framework shown, the rests on teeth numbers 20 and 28 are indirect retainers and function when the patient bites down on the distal extension area.
True False |
False
Although the rests on teeth numbers 21 and 28 are indirect retainers, they function when the extension base attempts to move away from the tissues (residual ridge)---not toward the residual ridge as would occur when the patient bites down. These rests are called indirect retainers because they increase the effectiveness of the direct retainers (clasps) when there is an attempt to dislodge the prosthesis. |
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Guide surface preparations should be completed before rest seat preparations.
True False |
True
The tooth structure removed during guide surface preparation will adversely affect the shape and contour of the rest seat preparation. Thus, the guide surfaces should be created BEFORE rest seats are prepared. |
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In the class II mandibular RPD shown to the right, the clasp on tooth #27 should be wrought wire BECAUSE the cingulum rest acts like a distal rest and the tip of the retentive arm is in front of the axis of rotation.
True False |
True
Both the statement and the reason are true. The rigid metal located above the survey line (height of contour) and closest to the edentulous space is that portion of the rest where it joins the guide plate/minor connector. The tip of the clasp lies in front of the axis of rotation and the clasp will be activated when the extension base moves toward the residual ridge. Thus, the clasp must be flexible to provide stress relief for the abutment. |
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When tripoding a cast, the vertical arm of the surveyor must be locked in position.
True False |
True
The purpose of tripoding is to allow re-orientation of the cast in the same position at a later date. Tripoding is based on the geometric principle that three points determine a plane. If the vertical arm of the surveyor moves during the tripoding process, the plane indicated by the marks would not be the same as that currently being used. |
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Referring to the maxillary class II RPD design shown to the right, which of the following statements is TRUE?
A short thick I-bar clasp could be used on tooth #6. A wrought wire circumferential clasp could be used on tooth #6. It is sometimes not necessary to use any clasp on tooth #6. 2 and 3 are both true |
4
Incorrect. Cast clasps should not be used anterior to the axis of rotation. Incorrect. #2 is a true statement but not the BEST answer. The most commonly used solution would be to use a WW clasp. The WW clasp would provide stress-relief through its increased flexibility: an important attribute in this case since the abutment tooth is in front of the axis of rotation. Incorrect. #3 is a true statement but not the BEST answer. If the patient is an experienced RPD wearer and retention is of minor importance, one might consider leaving the retentive arm off tooth #6. This would be more likely if esthetics were a major consideration. A good option might be to include the WW clasp initially and check the need for the clasp after delivery. This would be done by merely bending the clasp slightly away from the tooth and having the patient wear the prosthesis for a few days. If the patient managed the RPD without retention from the clasp, it could be cut off. Correct. #4 is the BEST answer. Both 2 and 3 are true statements. |
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The following statement refers to the drawing of the class I RPD to the right: The clasp arm on tooth #20 should be wrought wire BECAUSE functional forces cause tissueward movement of the denture base, the denture rotates around the rest (which is on the distal), and the clasp arm engages the tooth, tending to tilt it distally.
The statement and the reason are true AND related. The statement and the reason are true but are NOT related. The statement is true but the reason is false. Neither the statement nor the reason is true. |
1
The statements are both true and are related. The tip of the clasp arm would lie in front of the axis of rotation and the clasp would engage the tooth during functional movement of the extension base. Thus, the clasp needs to be flexible to provide stress relief to the abutment. |
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In the maxillary class I RPD shown at the right, the posterior border of the palatal plate major connector should be located
as far forward as is possible while maintaining enough width for strength approximately 20 mm behind the anterior border approximately 10 mm anterior to the fovea palatini at the posterior palatal seal area |
4
Incorrect. The palatal plate major connector is selected because it provides maximum support and denture style retention. Moving the posterior border forward negates both of these attributes. Incorrect. There is no such relationship between the anterior and posterior borders of a maxillary palatal plate major connector. Incorrect. One of the primary reasons a full palate is used is to create "denture style retention." Termination of the major connector 10 mm anterior to the fovea palatini would place the bead on the hard palate and a "seal" would be very difficult to achieve. Correct. The border should be placed in the posterior palatal seal area and should be beaded. One of the primary reasons a full palate is used is to create "denture style retention." To do so, a "seal" must be created at the posterior border by slightly depressing the soft tissues. |
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All components of a maxillary major connector should cross the palate at right angles to the midline and curves in the major connector should be located to one side of the midline.
True False |
True
Crossing the midline at right angles seems to create a situation which is less noticeable to the tongue. |
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In the case shown to the right, which is the most effective indirect retainer?
The rest on tooth #19. The rest on tooth #21. The rest on tooth #27. The rest on tooth #28. |
2
The rests on #19 and #28 are not indirect retainers. Rests on #21 and #27 are indirect retainers. The rest on #21 is further from a line connecting the tips of the retentive arms on theeth numbers 19 and 28 and is thus more effective than the rest on tooth #27. In reality, the rest on #27 could be omitted without appreciable loss of indirect retention. |
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What is the most significant problem with the rest shown on the mandibular canine to the right?
The rest should be wider inciso-gingivally. The rest should be located more toward the incisal edge. The rest should be thicker buccolingually. The rest should be located in a prepared rest seat. |
4
Rests must be placed in prepared rest seats. This is particularly important on anterior teeth where, without prepared rest seats, rests lie on inclined planes. Downward pressure on the rest will tend to push the abutment buccally. Note: the rest could be a little wider incisogingivally and it could also be a little thicker. However, these problems pale in comparison to the fact that there is no rest preparation. |
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In the RPD shown to the right, the guide surface - guide plate contacts on the distal surfaces of teeth numbers 20 and 29 determine a definite path of displacement/dislodgement.
True False |
False
The guide surface - guide plate contacts DO NOT determine a definite path of insertion in this case. If the minor connectors to the rests on the mesial occlusal surfaces of the premolars are in intimate contact with the abutments, they may help to ensure a definite path of insertion/dislodgement. However, it is safest to place the tips of the I-bar retentive arms just in front of the greatest mesiodistal curvature of the facial surface of the abutments. If the tips are placed at or behind the greatest mesiodistal curvature, it would be possible for the RPD to move slightly upward and backward allowing the retentive arms to escape the undercuts without flexing. Under these circumstances, the RPD would not exhibit retention. |
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The all plastic maxillary RPD should be avoided in all partial dentures except where the prosthesis is considered transitional and loss of the remaining teeth is imminent.
True False |
True
All plastic RPDs lack rigidity and tend to encourage plaque collection. Also, most lack adequate rests. They should only be used on a temporary basis or when the dentition is "terminal." |
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Tooth-supported RPDs require physiologic relief of the guide plates.
True False |
False
Because tooth-supported RPDs do not exhibit movement toward the tissues during function, physiologic relief is not necessary. Extension RPDs, on the other hand, do exhibit functional movement and do require physiologic relief. This is accomplished as follows: first coat the guide plates with chloroform and rouge or another disclosing medium, seat the framework in the mouth, and push toward the tissues over the extension areas; then relieve the guide plate with a fine textured stone. Repeat as necessary. It is very important that the guide plates do not bind against the abutments during functional movement --- otherwise they will pre-empt the planned mesial rests. |
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The superior border of a mandibular lingual bar major connector must be at least _____ mm below the gingival margins.
1-2 2-3 3-4 4-5 |
3
3-4 mm is a minimum. Numerous studies have shown that placing the superior border of the major connector less than 3 mm away from the gingival margin leads to increased plaque collection and subsequent increased marginal inflammation. |
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For maxillary major connectors, except where plating is used, the border of the major connector should be at least ______ mm away from the gingival margin.
1 3 5 6 |
4
At least 6 mm can almost always be obtained since one does not have the space limitations created by the floor of the mouth---as in the mandibular arch. Depending on the anatomy of the arch and the width and strength requirement of the elements of the major connector, more than 6 mm can often be obtained. |
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For the anterior-posterior palatal strap maxillary major connector, the anterior, posterior, and lateral straps should be about ______ mm wide.
4-6 6-8 8-10 at least 10 |
2
6-8 mm allows for adequate strength while allowing for maximum tissue exposure both over the palate and in the area of the marginal gingiva. |
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The basic philosophy of dental treatment for a partially edentulous patient is to
preserve what remains and restore what is missing replace the missing teeth improve the path of insertion reshape rotated teeth |
1
Restoring what is missing is rather obvious. It should be equally obvious that the restoration will ultimately fail if what remains is not preserved. While answers 2, 3, and 4 play a role in RPD design and treatment, they don't represent a "philosophy" and are certainly secondary to "preservation and restoration." |
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It is best not to use a balanced occlusion when mandibular RPDs oppose maxillary complete dentures.
True False |
False
It is best to use balanced occlusion when a complete denture opposes a partially edentulous arch restored with a removable partial denture. |
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The function of the guide plate is to
help establish a definitive path of insertion/dislodgement. stabilize the RPD by controlling its horizontal position. provide contact with the adjacent tooth. all of the above |
4
Guide plates serve all the functions listed under 1, 2, and 3. Therefore, the best answer is 4 (all of the above). |
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What is the design error in the maxillary RPD framework shown to the right?
The anterior teeth should have been plated. An anterior-posterior palatal strap major connector should have been used. There should be a cast circumferential clasp on tooth #6. The posterior border of the major connector should cross the palate at right angles to the midline. |
4
Incorrect. There is no information given that would lead one to believe that the anterior teeth should be plated. In this particular case, plating the anterior teeth would definitely be the exception rather than the rule. Incorrect. In the situation shown, an A-P palatal strap would be difficult to design. The space between teeth 3 and 6 is much better suited to the use of a modified palatal plate---if it is done correctly. Incorrect. Tooth #6 lies bodily in front of the axis of rotation and a cast circumferential clasp should definitely NOT used. If a clasp is needed or desired, it should be wrought wire. Correct. For many people, the tongue would be sensitive to the lack of symmetry of the major connector in the area of the midline of the palate. It would be better if the posterior border crossed the midline at a right angle and then extended backward more or less parallel to the residual ridge. |
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What would be the best denture base connector when there is limited interocclusal space (<3 mm).
Open latticework Meshwork All metal base All plastic base |
3
The all-metal base would be very strong even with very limited thickness. In order for plastic to extend beneath either latticework or meshwork, the metal retentive network must be off the ridge by a millimeter or so. This would leave little space for plastic external to the network. There simply is not enough interocclusal space for adequate thickness of BOTH plastic and metal. The all plastic base would be very weak because of the limited thickness and is therefore not indicated. |
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The first consideration in developing occlusion is the evaluation and establishment of the correct position of the occlusal plane. This may be compromised by super-erupted and malposed teeth.
True False |
True
Partially edentulous arches often exhibit unusual occlusal planes due to malposed natural teeth. More often than not, the final occlusal plane is a compromise necessitated by super-eruption and drifting. |
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Your patient's partially edentulous arch is depicted in the illustration to the right. The missing teeth (with the exception of the third molars) were extracted three weeks ago. What would be the best denture base/replacement teeth combination in this instance?
Open latticework Metal bases with beads for attachment of processed tooth colored acrylic resin. An all metal base Tube teeth |
1
Because of the "green" residual ridges, open latticework is the best choice. Relining is easier after the tissues heal completely. In fact, the other choices all involve some type of metal base and relining after healing is almost impossible. |
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A wrought wire clasp is NOT used in which of the following situations?
On a terminal abutment of an extension RPD. As an embrasure clasp. On a tooth with an indirect retainer on it. Both 1 and 2 above. |
2
Incorrect. Wrought wire clasps are commonly used on terminal abutments for extension RPDs. Correct. Wrought wire clasps should not be used as embrasure clasps. It is difficult to bend the clasp accurately through the embrasure and the slightest nick in the wire or wear from occlusion will predispose the clasp to breakage in the area where it passes over the occlusal surfaces of the teeth. Incorrect. Wrought wire clasps are frequently used on teeth that have indirect retainers on them. A good example would be a class II modification 1 RPD where the anterior abutment on the tooth-supported side has a rest that acts as an indirect retainer. If this tooth also has a clasp on it, the clasp should be wrought wire because the tooth lies bodily in front of the axis of rotation. Incorrect. Answer 4 is incorrect because answer 3 is incorrect. |
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In designing a RPD framework for the partially edentulous arch to the right---if at all possible, circumferential clasps should be used on the numbers 28 and 30. They would be preferred to infrabulge retainers.
True False |
True
When only one tooth is missing on a tooth-supported RPD, infrabulge retainers should be avoided. The descending and ascending portions of the arms are so close together that they form food traps. |
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Determining areas for physiologic relief is accomplished by marking the framework intraorally. This process includes adjusting the casting to allow for functional movement on Class I and II RPDs to relieve stress on the terminal abutment teeth.
True False |
True
The statement is an accurate description of "physiologic adjustment." Class III and Class IV RPDs do not require physiologic adjustment since there is no movement of the prosthesis during function. |
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Reciprocation between bracing and retentive components requires
I-bars be used bracing components contact after retentive components correct timing of contact during seating and removal of the RPD both 2 and 3 |
3
Incorrect. The type of clasp (retentive arm) is not an important consideration in determining whether or not reciprocation occurs. Incorrect. For reciprocation to occur, retentive and bracing components must contact the teeth at the same time. Correct. For reciprocation to occur, retentive and bracing components must contact the teeth at the same time. As the retentive tips pass over the height of contour, the rigid opposing elements must maintain contact with the abutments. This issue of TIMING is critical in the concept of reciprocation. If the rigid elements only contact the teeth when the RPD is seated, they will function for bracing but not for reciprocation. Incorrect. Since #2 is incorrect, #4 is also incorrect. |
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Infrabulge clasps originate
above the height of contour below the height of contour above the 0.01" undercut above the occlusal surface of most premolars |
2
Incorrect. Clasps originating above the height of contour are suprabulge retainers, "supra" meaning above. Correct. "Infra" means below so infrabulge clasps originate below the height of contour and approach the undercut from a gingival direction. Incorrect. Infrabulge clasps approach the undercut from below---from a gingival direction. Also, by definition, supra or infrabulge categories are based on a relationship to the "bulge" or height of contour, not to the amount of undercut. Incorrect. An approach from above the occlusal surface would constitute "suprabulge". Such an approach is also impractical and nonsensical. |
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A modified palatal plate is used in maxillary class II cases and may or may not include lingual plating
True False |
True
Modified palatal plate major connectors are used in maxillary Class II RPDs. Plating is not common but can be used. |
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All of the following clasps are infrabulge clasps except?
I-bar Modified T-bar Roach clasp Akers clasp |
4
All the clasps mentioned except the Akers clasp approach the undercut from a gingival or infrabulge direction. "Akers" is the old name for a circumferential clasp which is, of course, a suprabulge clasp. |
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A clasp assembly should
have a retentive arm with adequate length and taper for flexibility have a retentive arm that terminates in an undercut have elements that considered together, provide 180 degree encirclement all of the above |
4
A clasp assembly should have all of the attributes described in 1, 2, and 3. |
|
The partial denture that will be completed on the framework shown to the right can do all of the following except
transfer stresses to the abutment teeth transfer stresses across the arch minimize supereruption of opposing teeth act as an orthodontic retainer for the lower incisor teeth. |
4
Incorrect. The statement is true. The RPD will transfer stresses to the abutment teeth through the rests, guide plates, major and minor connectors, and retentive arms. Incorrect. The statement is true. The RPD will transfer stresses across the arch through the rests, guide plates, major and minor connectors, and bracing and retentive arms. This is an important positive attribute because it is through this mechanism that stresses are dissipated throughout the arch rather than being concentrated in one area. Incorrect. The statement is true. The completed RPD (with denture teeth in the posterior edentulous areas) will help to minimize super-eruption of the opposing teeth. It should be pointed out, however, that super-eruption will not be totally prevented. As the plastic denture teeth wear, some super-eruption will take place. Correct. Although plating would prevent permanent tooth movement to the lingual, it will not prevent movement to the facial which is the normal direction of migration, particularly in the presence of periodontal disease. |
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Maxillary class II RPDs do not have an axis of rotation because no functional movement will occur over the hard midline suture of the palate.
True False |
False
Maxillary class II RPDs do have an axis of rotation. It is not affected by the midline suture. |
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In a Class III modification 1 RPD, the rests are usually placed
on the canines away from the modification space in the area of the opposing occlusal contact adjacent to the modification space. |
4
Incorrect. Although answer 1 is possible, it is not the BEST answer because the stem of the question does not specifiy that the canines are adjacent to the edentulous areas. Incorrect. In tooth-supported RPDs, rests are usually placed immediately adjacent to the edentulous space(s). Incorrect. Areas of opposing occlusal contacts should be avoided whenever possible. Correct. In tooth-supported RPDs, rests are usually placed immediately adjacent to the edentulous space(s). |
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A mandibular lingual bar major connector such as the one shown in the RPD to the right requires a minimum of _____mm of vertical height between the gingival margin and the floor of the mouth.
4 5 7 8 |
3
At least 3 mm is required for the space between the superior border of the major connector and the gingival margin and at least 4 mm is required for the vertical height of the lingual bar. 3 + 4 = 7 mm minimum. |
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The presence of mandibular lingual tori would indicate the need for
a metal base lingual plating tube teeth extra indirect retainers |
2
Incorrect. There is no relationship between the presence of tori and the selection of a metal base. Correct. The major connector cannot extend below the height of contour of the tori and consequently, there is seldom the 7 mm minimum vertical space needed for a lingual bar. Incorrect. There is no relationship between tori and the selection of tube teeth. Incorrect. It is certainly not the BEST answer. However, there is some logic for answer #4. Since the tissue over the tori is very thin and not tolerant to any vertical pressure, one could argue that additional indirect retainers could be used to safeguard against tissue trauma under the major connector. However, #2 is really the best answer. |
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The illustration to the right shows a framework for a mandibular class II RPD. The indirect retainer on tooth 21 functions when
the patient chews on something hard the patient chews on something soft the patient chews on something sticky the patient bites the bullet |
3
Incorrect. Indirect retainers DO NOT function when the patient bites down. It doesn't matter whether the substance is soft or hard. Incorrect. Same as #1 above. Correct. Indirect retainers come into play AFTER the patient bites down and then begins to open again. The sticky nature of the material attempts to pull the denture base away from the residual ridge. The indirect retainers prevent the RPD from simply rotating around a line connecting the tips of the direct retainers (clasps, retentive arms). They assist the direct retainers in resisting dislodgement of the prosthesis. Incorrect. Humor??? |
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An anterior-posterior palatal strap maxillary major connector has greater strength and rigidity than a horseshoe design.
True False |
True
The anterior-posterior palatal strap has greater strength and ridigidty because of its circular shape and because the metal straps lie in several different planes. |
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Your patient has the mandibular arch form shown to the right. A rest on which tooth would be the most effective indirect retainer?
20 21 22 27 |
4
Incorrect. A rest on #20 would be a primary rest, not an indirect retainer. Incorrect. Tooth #21 would often have a rest on it and this rest would function as an indirect retainer. However, it would not be the MOST EFFECTIVE indirect retainer. Incorrect. This tooth would seldom have a rest in the partially edentulous situation shown. Even if it did, it would not be the MOST EFFECTIVE indirect retainer. Correct. The rest on #27 would be a very effective indirect retainer because it lies furthest from a line connecting the tips of the direct retainers (clasps). |
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Your patient exhibits the mandibular class II modification 1 arch shown to the right. Tooth #30 is tilted mesiolinguallly and has very little tissue undercut on the lingual. What is the best clasp for this situation?
Cast circumferential clasp utilizing a distolingual undercut Cast I-bar utilizing a mesiolingual undercut Cast ring clasp utilizing a mesiolingual undercut Wrought wire circumferential clasp utilizing a distolingual undercut. |
2
Incorrect. Due to the mesiolingual tilt of the tooth, it is unlikely that there will be a usable distolingual undercut. Correct. The mesiolingual I-bar will work very well. It must be on the mesiolingual corner of the tooth and it must emanate from the inferior border of the major connector so that it has adequate length to be flexible. Incorrect. This is not the best selection unless there is a severe tissue undercut that will cause the mesiolingual I-bar to stand out in the floor of the mouth and irritate the tongue. Incorrect. Due to the mesiolingual tilt of the tooth it is unlikely that there will be a usable distolingual undercut. In addition, there is no reason to use a WW clasp in this situation---no need for increased flexibility or stress-breaking. |
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Rigid metal retention is associated with
a dual path of insertion a class IV RPD the need for excellent esthetics all of the above |
4
Incorrect. The statement is true but is not the BEST ANSWER. The dual path of insertion allows rigid metal to be placed in an undercut. Incorrect. The statement is true but is not the BEST ANSWER. Rigid metal retention is not used exclusively in class IV RPDs but certainly is commonly used in such situations. Incorrect. The statement is true but is not the BEST ANSWER. Rigid metal retention eliminates the need for clasps on anterior teeth and produces excellent esthetics. This is the reason it is often used on class IV RPDs. Correct. 1, 2, and 3 are all true statements. |
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The palatal strap maxillary major connector is primarily used in short span maxillary class III modification 1 RPDs.
True False |
True
If the edenulous areas of maxillary class III RPDs are larger, one is more apt to select an anterior-posterior palatal strap. |
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Your patient has the class I arch shown to the right. The axis of rotation is most frequently determined by:
the placement (location) of the primary rests the type of clasp arms selected the placement of the minor connectors the placement of the indirect retainers |
1
Correct. The axis of rotation passes through the rigid metal that lies above the height of contour and closest to the edentulous space. This should be the rests, as all other rigid metal lies on inclined slopes. In the case shown, the axis of rotation would pass through the rests on teeth numbers 20 and 27. Incorrect. The axis of rotation is not determined by the type or location of the clasps. Incorrect. The location of the minor connectors has no relation to the axis of rotation. Incorrect. The axis of rotation passes through the PRIMARY rests and is important when the extension base moves toward the tissues. The indirect retainers function when the extension base moves away from the tissues and are not related to the location of the axis of rotation. |
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In maxillary RPDs, the bead line is approximately _______mm thick (deep).
4 3 2 1 |
4 (meaning 1mm)
Because the metal exhibits very little dimensional change in the casting process, the bead can be very light. Its primary purpose is to provide positive contact with the tissues so food does not get under the major connector. At the posterior border of a palatal plate major connector, it may also help provide denture style retention. |
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The C + 1 rule
Does not apply to class IV RPDs Does not apply to class III RPDs Gives a general rule for the number of clasps Both 1 and 3 |
4
Incorrect. Although answer 1 is a true statement, it is not the BEST answer. Incorrect. With very few exceptions, the C+1 rule does apply to class III RPDs. Incorrect. Although answer 3 is a true statement, it is not the BEST answer. Correct. Statements 1 and 3 are both correct. |
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Which of the following maxillary major connectors possesses the least strength and rigidity?
Anterior-posterior palatal strap Horse-shoe Palatal plate Modified palatal plate |
2
The horse-shoe maxillary major connector has the least strength and rigidity unless it is very bulky. For this reason, it is the least desirable of all the maxillary major connectors. |
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A cingulum rest is normallly placed between the middle and incisal thirds of the maxillary incisors in order to avoid occlusal interferences.
True False |
False
The statement is false. Rests on maxillary incisors generally need to be placed as far gingivally as possible to avoid the opposing occlusion. This is generally no further incisally than the junction of the gingival and middle thirds. |
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Your patient exhibits the mandibular class II modification 1 arch shown to the right. Tooth #30 is tilted mesiolingually, but has a very severe tissue undercut on the lingual. What is the best clasp for this situation?
Cast circumferential clasp utilizing a distolingual undercut. Cast I-bar utilizing a mesiolingual undercut. Cast ring clasp utilizing a mesiolingual undercut. Wrought wire circumferential clasp utilizing a distolingual undercut. |
3
Incorrect. Due to the mesiolingual tilt of the tooth, it is unlikely that there will be a usable distolingual undercut. Incorrect. The mesiolingual I-bar would be appropriate EXCEPT that there is a severe tissue undercut. In this instance, the I-bar would stand out in the floor of the mouth and would have significant potential for irritating the tongue. Correct. The ring clasp is the best selection because there is a severe tissue undercut that would cause a mesiolingual I-bar to stand out in the floor of the mouth and irritate the tongue. The buccal portion of the ring clasp must be heavy enough to be rigid and strong, and an auxiliary distal rest should be used. Incorrect. Due to the mesiolingual tilt of the tooth, it is unlikely that there will be a usable distolingual undercut. In addition, there is no reason to use a WW clasp in this situation. |
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All methods of measuring the vertical dimension of occlusion agree on one major principle: In physiologic functions (speaking and swallowing) the teeth should make contact.
True False |
False
The teeth will contact during swallowing as the mandible braces against the maxilla. However, the teeth should NOT contact during speech. If they do, the vertical dimension of occlusion is too great. |
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Malposed or super-erupted teeth may cause a discrepancy between centric relation and centric occlusion. Therefore, it is recommended that the opposing teeth not touch during the making of a centric relation record for mounting of diagnostic casts.
True False |
True
Contact of the natural teeth during making of a centric relation record is a common cause for error in the record. When the teeth contact, they may cause the mandible to deflect or move away from centric relation. |
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The purpose of the centric relation record is to record the exact position of the maxilla to the mandible in a protrusive relation.
True False |
False
The relation of the maxilla and the mandible in a protrusive position is a "protrusive record" not a "centric relation record." |
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If abutment teeth require crowns, the RPD design is prepared after the crowns are cemented.
True False |
False
The RPD design should be determined BEFORE the crowns are fabricated so that the appropriate rest seats and contours can be incorporated into the crowns. |
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Alginate impression materials have excellent dimensional stability over time and seldom lead to over extended vestibular extensions.
True False |
False
The statement is false on both counts. Alginate has poor dimensional stability over time and should be poured as soon as possible. Its consistency often leads to over-extenstions in the vestibules, especially if a stock tray is used. |
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Master casts for patients with lone-standing abutments should be poured in "Silky Rock" stone.
True False |
True
Lone-standing abutments are more likely to fracture when the impression is separated from the cast and the extra strength of "Silky Rock" or some other "improved" stone minimizes this problem. |
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The altered cast impression technique is often used on Class I and Class III RPDs.
True False |
False
The altered cast impression is used on class I and class II RPDs. Almost never on class III RPDs. |
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Your patient exhibits the partially edentulous mandibular arch shown to the right. The maxillary arch is to be restored with a complete denture. Teeth 20 and 29 will receive crowns. There are no contraindications to any type of clasping. Which of the following clasp assemblies would you use on 20 and 29.
Mesial rests and I-bars Mesial rests and modified T-bars Distal rests and WW circumferential clasps Distal rests and cast circumferential clasps. |
1
With our philosophy, the number one choice of clasp assemblies for extension RPDs is mesial rests and I-bar retentive arms---so that the clasps will RELEASE during functional movements of the extension bases. The appropriate rest seats and undercuts should be incorporated into the crowns. |
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Your patient exhibits the partially edentulous mandibular arch shown to the right. The maxillary arch is to be restored with a complete denture. Teeth 20 and 29 will receive crowns. There are very high labial frenal attachments on both sides. Which of the following clasp assemblies would you use on 20 and 29?
Mesial rests and I-bars Mesial rests and modified T-bars Distal rests and WW circumferential clasps Distal rests and cast circumferential clasps. |
3
Distal rests and WW clasps should be used since there is a contraindication to bar clasps---the high frenal attachments. The rest seats and appropriate mesiofacial undercuts must be incorporated into the crowns. |
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Your patient exhibits the partially edentulous mandibular arch shown to the right. The maxillary arch is to be restored with a complete denture. The undercuts on 20 and 29 are on the distal portion of the facial surface. There are no contraindications to either infrabulge or suprabulge retainers. Which of the following clasp assemblies would you use on 20 and 29?
Mesial rests and I-bars Mesial rests and modified T-bars Distal rests and WW circumferential clasps Distal rests and cast circumferential clasps |
2
The primary indication for modified T-bar infrabulge retainers occurs when the undercuts are adjacent to the edentulous area (on the distofacial in this case). One must be sure the vertical portion of the arm contacts the tooth in front of the greatest mesiodistal curvature. |
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Reciprocation of clasps is related to the timing of contact between the bracing and retentive clasp arms in order to prevent undue forces on the abutment teeth during seating and removal of the RPD.
True False |
True
In order to provide true reciprocation, the timing must be correct. The bracing arm must be in contact with the abutment as the retentive arm passes over the bulge and into the undercut. |
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Your patient has the partially edentulous arch shown to the right. The undercuts on 21 and 28 are on the mesiofacial surfaces. The most commonly used clasp assemblies on the premolars would be:
Distal rests and I-bars Distal rests and modified T-bars Distal rests and cast circumferential clasps Distal rests and WW circumferential clasps |
3
For tooth supported RPDs, whenever the undercut is in the appropriate area---opposite the point of origin of the clasp (away from the edentulous area)---a cast circumferential clasp is the retainer of choice. |
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Your patient has the partially edentulous arch shown to the right. The undercuts on 21 and 28 are on the distofacial surfaces. There are no contraindications to any types of clasps. Under these circumstances, the most commonly used clasp assemblies on the premolars would be:
Distal rests and I-bars Distal rests and modified T-bars Distal rests and cast circumferential clasps Distal rests and WW circumferential clasps |
2
The undercuts are in the appropriate location for modified T-bars. Either mesial or distal rests can be used since the RPD is tooth-supported and exhibits no functional movement. |
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Your patient has the partially edentulous arch shown to the right. The undercuts on 21 and 28 are on the mesiofacial surfaces and there are no contraindications to suprabulge or infrabulge retainers. The long range prognosis for the molars is poor but your patient does not want them extracted at this time. Several alterations in the usual design could be made to facilitate later conversion of the prosthesis to a class I RPD. One of them involves the clasp assemblies on the premolars. Your recommendation?
Distal rests and I-bars Distal rests and modified T-bars Distal rests and cast circumferential clasps Distal rests and WW circumferential clasps |
4
Incorrect. If the molars were lost, the I-bars would be cast clasps in front of the axis of rotation. It is possible that I-bars could be used but the rests should be changed to the mesial. Incorrect. The undercuts are not in the appropriate location for modified T-bars. In addition, if the molars were lost, the cast clasps would be in front of the axis of rotation. Incorrect. If the molars were lost, the tips of the cast circumferential clasps would be in front of the axis of rotation. Correct. If the molars were lost, the WW clasps would provide stress relief for the abutments (due to their flexibility) when the extension base moves toward the residual ridge. |
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Your patient has the partially edentulous arch form shown to the right. The molars have drifted mesially and lingually. With these factors in mind, rigid metal retention could be considered for use on the molars.
True False |
True
In this case, there are normally undercuts on the mesial surfaces of the molars---due to the drifting. If only partial blockout is done on the mesial surfaces of the molars during framework fabrication, the rigid metal of the guide plates will slide into the undercuts and then the anterior part of the RPD is rotated downward into position. Now the posterior portion of the RPD cannot be dislodged unless the clasps on the premolars release first allowing the anterior portion of the RPD to move upward and forward. |
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Which one of the following classes of RPDs NEVER has an axis of rotation?
Class I Class II Class III Class IV |
3
Incorrect. Class I RPDs always have an axis of rotation. Incorrect. Class II RPDs always have an axis of rotation. Correct. Class III RPDs never have an axis of rotation. Incorrect. Class IV RPDs usually do not have an axis of rotation but many people consider that if all the incisors and the canines are missing, the anterior edentulous area is so extensive that there is essentially an "anterior extension" and an accompanying axis of rotation. |
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What is the major problem with the RPD framework shown to the right?
Teeth numbers 21 and 28 should be plated. The plating on the lingual surfaces of the anterior teeth should cover the cinguli. Distal rests would be better than mesial rests on teeth numbers 21 and 28. Cast circumferential clasps are preferred with the mesial rests on teeth numbers 20 and 29. |
2
Incorrect. While teeth numbers 21 and 28 could be plated, there is nothing in the stem of the question indicating that this is necessary. Answer #1 is not the BEST answer. Correct. As shown, the plating ends at the tooth tissue junction---essentially in the sulcus. Plating must extend to the contacts interproximally and must cover the cinguli. When possible, rest seats should be prepared on the incisor teeth and must be prepared at least on the canines. Incorrect. Assuming the undercuts are appropriate for I-bars and there is no contraindication to infrabulge retainers, the mesial rest, I-bar, distal guide plate is the preferred clasp assembly. Simply changing the rests to the distal would place the I-bars (which are cast clasps) in front of the axis of rotation. Incorrect. Mesial rests, distal guide plates, and cast circumferential clasps compose the clasp assembly called the "RPA". This is not the recommended design because the rigid originating portion of the cast clasp often lies above the height of contour and acts like a rest on an inclined plane. |
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Which of the following could be reason(s) for choosing the double lingual bar major connector shown to the right?
Large interproximal spaces have resulted from periodontal surgery. The patient exhibits a high floor of the mouth. There is overlapping of the anterior teeth. Both a and b above. |
1
Correct. If there is the need to provide indirect retention from the anterior teeth but large interproximal spaces exist, the metal from the lingual plate could be visible and unsightly. In this case, a double lingual bar might be indicated. However, it is NOT a commonly used major connector. Incorrect. The inferior bar of the double lingual bar major connector must meet all the requirements for a conventional lingual bar. Consequently, the double lingual bar cannot be used when there is a high floor of the mouth. Incorrect. Overlapping anterior teeth pose the same problems for the upper bar of the double lingual bar connector as they pose for linguoplating. In either case, the teeth would need to be recontoured to eliminate spaces between the teeth and the connector. Incorrect. Since #2 is incorrect, #4 is incorrect. |
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When possible, plating on maxillary RPDs should be avoided due to the potential for interfering with speech and occlusion.
True False |
True
Plating on maxillary RPDs occasionally causes problems with speech and frequently interferes with normal occlusion of the maxillary and mandibular teeth. |
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The survey line (height of contour) of a full contour wax-up for a crown for an RPD abutment tooth can be visualized using
red wax zinc stearate powder border wax pressure indicating paste |
2
After the surface of the wax-up is lightly covered with zinc stearate, the analyzing rod is passed over the surface of the wax. The height of contour will appear darker than the surrounding powdered surface. |
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Your patient has only teeth numbers 20 through 29 remaining. You have tried in the framework and are border molding the extension areas in preparation for an altered cast impression. The distobuccal area is shaped by the?
Buccinator muscle Masseter muscle Internal pterygoid muscle Mylohyoid muscle |
2
Incorrect. The buccinator muscle is a relatively weak muscle and its fibers run anterior-posteriorly. It has very little if any effect on the shape of the distobuccal corner of the denture base. Correct. The masseter muscle is a powerful muscle whose fibers run more or less superiorly-inferiorly. Upon contraction, it pushes the buccinator muscle and other tissues into the distobuccal corner of the denture base. Incorrect. The internal pterygoid muscle has no effect on the distobuccal corner of the mandibular denture base. Incorrect. The mylohyoid muscle has no effect on the buccal aspect of the denture base. |
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Your patient has teeth numbers 20 through 29 remaining. The survey line and undercut (shaded area) for tooth #29 are as shown on the right. There is no contraindication to the use of an infrabulge clasps but there is a very solid contact in the mesial-occlsual fossa. What would be your choice for rest location and retentive arm?
Distal rest and cast circumferential clasp Distal rest and cast I-bar Mesial rest and cast I-bar Distal rest and WW circumferential clasp |
4
Incorrect. NO! NEVER! Incorrect. The I-bar would lie in front of the axis of rotation and is a cast clasp. It would not release during function and would have the potential to torque the tooth. Incorrect. Although the undercut is appropriate for an I-bar, a mesial rest cannot be used due to the occlusion and, if a distal rest is used, the cast I-bar would lie in front of the axis of rotation. Correct. Since the occlusion precludes the use of a mesial rest, the rest must be moved to the distal. Virtually any type of clasp will place the retentive tip in front of the axis of rotation and flexibility of the clasp is of paramount importance---thus, wrought wire. |
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(Image did not appear on website)
Your patient has teeth numbers 20 through 29 remaining. The survey line and undercut (shaded area) for tooth #29 are as shown on the right. There is no contraindication to the use of an infrabulge clasps and there are no occlusal problems affecting rest location. What would be the best choice for rest location and retentive arm? Mesial rest and I-bar Mesial rest and modified T-bar Mesial rest and WW circumferential clasp Distal rest and WW circumferential clasp |
2
Incorrect. The undercut is not appropriate for an I-bar. The I-bar must be placed just in front of the greatest mesiodistal curvature of the facial surface. In this case, most of the undercut is behind the greatest mesiodistal curvature of the facial surface. Correct. Most of the undercut is behind the greatest mesiodistal curvature of the facial surface and that is where the retentive tip should be placed. The vertical approach arm must be placed in front of the greatest mesiodistal curvature so that the clasp cannot simply move upward and backward without flexing. If this could happen, the clasp would not be retentive. Incorrect. A circumferential clasp cannot be used because the undercut is adjacent to the edentulous area (and on the same side of the tooth as the origin of the arm). Incorrect. Same reason as #3. |
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Your patient has teeth numbers 20 through 29 remaining. The survey line and undercut (shaded area) for tooth #29 are as shown on the right. There is no contraindication to the use of an infrabulge clasps. The opposing occlusion is provided by a complete denture. What would be your choice for rest location and retentive arm?
Mesial rest and I-bar Mesial rest and modified T-bar Mesial rest and cast circumferential clasp Distal rest and WW circumferential clasp |
1
Correct. A mesial rest and I-bar is the best choice. The I-bar lies at or behind the axis of rotation and would release during functional movement of the denture base. It is our #1 choice if the undercut is in the appropriate location, if an infrabulge clasp can be used, and if there is no contraindication to placement of a rest on the mesio-occlusal surface. Incorrect. Although a modified T-bar could work, it is not the first choice, especially when most of the undercut lies on the mesiofacial surface. Incorrect. This would be the "RPA" concept. The problem is that the originating portion of the clasp is rigid and would lie above the survey line. It would function like a rest on an inclined plane---not a good idea! Incorrect. Although a distal rest and WW circumferential clasp could work in this situation, it is not our first choice. We would rather have a clasp arm that releases during functional movement (downward, tissueward) movement of the denture base. |
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Your patient has only teeth numbers 20 through 29 remaining. You have tried in the framework and are border molding the extension areas in preparation for an altered cast impression. The distolingual border molding is shaped by the?
Masseter muscle Internal pterygoid muscle Superior constrictor muscle Mylohyoid muscle |
3
Incorrect. The masseter muscle has no effect on the contour of the lingual flange. Incorrect. The internal pterygoid muscle has no effect on the lingual denture flange. Correct. The superior constrictor muscle affects the most distal portion of the lingual flange. If you are overextended in this area, the patient's complaint will often be that he/she has a sore throat. Incorrect. The mylohyoid muscle affects the lingual flange but not at its most posterior (distal) aspect. |
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As a general rule, plating is indicated for the maxillary arch if there are less than three contiguous maxillary incisor teeth remaining.
True False |
True
The plating will provide cross arch stability and will also provide a mechanism for adding artificial teeth to the RPD should any of the remaining teeth be lost. Also, plating will close up small, one tooth openings in the framework. |
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All of the components listed below may be involved in the 180 degree encirclement rule EXCEPT
I-bar Minor connector Guide plate Open latticework |
4
Incorrect. An I-bar (or any type of retentive arm) can be one component that helps establish 180 degree encirclement of an abutment. Because retentive arms are flexible, they may not be quite as effective as some other components but they still contribute. Incorrect. Because of their location and their rigidity, minor connectors are very effective contributors to 180 degree encirclement. Incorrect. Because of their location and rigidity, guide plates are very effective contributors to 180 degree encirclement. Correct. Open latticework (or any type of denture base retentive element) has no relation to the 180 degree encirclement rule. |
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What is the correct relationship of the foot of an I-bar to the survey line (height of contour) on a terminal abutment for an extension RPD?
The foot should be entirely above the survey line. The foot should be partially above and partially below the survey line. The foot should be totally below the survey line. The relationship of the foot of the I-bar and the survey line is of no consequence. |
3
Incorrect. The foot cannot extend above the survey line or it will not release during functional movements of the extension base. Incorrect. Same reasoning as #1. Correct. The foot should be totally below the survey line so that it will release during functional movements of the extension base. Incorrect. It DOES make a difference. |
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The primary indication for and Oddo clasp occurs when an anterior abutment has excessive labial inclination so that the retainer (clasp) would be very close to the incisal edge.
True False |
True
The statement is true---the primary reason for using an Oddo hinge clasp is to improve esthetics by moving the clasp arm gingivally. Less frequently, Oddo hinge clasps may be used to prevent infrabulge arms from standing out in the vestibule. While Oddo clasps are more commonly used in the maxillary arch for esthetic reasons, they may be used in either arch to prevent infrabulge arms from standing out in the vestibule. |
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The purpose of the altered cast impression procedure is to obtain the maximum support possible from the edentulous areas of class I and class II RPDs.
True False |
True
The altered cast impression captures the tissues of the edentulous ridges in relation to the way the framework fits in the mouth (not on the cast). Hopefully, the two would be the same but that is not always the case. With an altered cast impression, one also tends to avoid the overextension that is prevalent with a cast made from an alginate impression in a stock tray. |
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When there are extensive edentulous areas present in both arches and no opposing teeth meet, we should establish the vertical dimension of occlusion prior to making a centric relation record.
True False |
True
It is always a good idea to establish the VDO before making a centric relation record. In theory, the VDO could be adjusted on the articulator after the casts are mounted if a face-bow transfer has been done. However, since the type of face-bow transer we do is "arbitrary" and since some inaccuracy is to be expected, it is best to make the centric relation record at the correct VDO whenever possible. |
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You are fabricating maxillary and mandibular RPDs for your patient. At the framework try-in appointment, both frameworks should initially be placed in the mouth to check for occlusal interferences.
True False |
False
The frameworks should be tried in one at a time. First, each should be checked for fit. Then the occlusion should be adjusted with each of the frameworks in place without the other. Finally, the occlusion is adjusted with both frameworks in place. |
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A protrusive record is made with the mandibular anterior teeth approximately 6 mm forward of centric relation (or with the mandibular and maxillary anterior teeth in an edge to edge relationship). This record is used to set the horizontal condylar guidance on the articulator.
True False |
True
After the protrusive record is made, the casts, prostheses, or record bases and the record are placed on the articulator. The horizontal guidance controls on each side are loosened and rotated until the record and teeth or keys fit together as accurately as possible. |
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The space that opens between the posterior teeth during anterior movement of the mandible is called Christensen's Phenomenon. This posterior separation is increased if the incisal guidance is increased.
True False |
True
The amount of posterior separation is affected by both the incisal guidance and the horizontal condylar guidance. The separation is increased as both IG and HCG increase---the effect of IG is greater anteriorly and the effect of HCG is greater posteriorly. |
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Before trying in a framework, you should inspect the master cast for damage and inspect the framework for sharp fins.
True False |
True
If the master cast has been damaged in the fitting of the framework to the cast, there is a high probability that the framework will not fit in the mouth. The areas of damage should be the first areas adjusted if the framework does not fit. Sharp fins are very prone to damaging the cast and thus also very suspect if the framework does not fit---but sometimes the damage to the cast caused by tiny fins is very difficult to see. |
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Your RPD framework fits the cast but does not fit in the mouth. One should assume that the impression for the cast was inaccurate and that a new impression will need to be made.
True False |
False
The impression and/or the cast may be inaccurate and thus be the cause of the problem. However, because of the time and cost involved in making the framework, all other possible causes should be eliminated before making a new impression. Scarring of the cast or sharp fins or protuberances on the framework might be correctable by analyzing the metal contacts with the teeth with some type of disclosing medium and relieving the metal. Inaccuracies from very minor tooth movement may also be corrected in this manner. If attempts to fit the framework to the mouth are unsuccessful, then one can assume that either the impression or the cast is inaccurate and the impression will need to be remade. |
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The fewer teeth that remain, the more like a denture the RPD becomes and the more likely the need for a custom impression tray.
True False |
True
As fewer teeth remain, the edentulous areas become larger. In general, a stock tray will perform adequately in areas where teeth remain but relatively poorer in edentulous areas. This is one of the major reasons an altered cast impression is done. However, when the number of teeth is very few and the edentulous areas are very large, it is sometimes easier to make a custom tray and border mold before the impression is made. In this way, the altered cast procedure can usually be omitted. |
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Reason(s) for selecting a mandibular lingual plate major connector is/are?
The presence of lingual tori. Anticipated loss of one or more of the remaining teeth. A high lingual frenum. 1, 2, and 3 above |
4
Answers numbers 1, 2, and 3 are all very valid reasons for selecting a linguoplate major connector. |
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Your patient has teeth 20 through 29 remaining. Tooth #29 exhibits the tooth contours and undercut shown in the illustration to the right. Which of the clasp assemblies listed has the GREATEST DANGER of torquing the abutment during functional movements of the extension base?
Mesial rest and cast I-bar Distal rest and WW circumferential clasp RPA clasp assembly with a cast clasp All have about the same potential danger |
Incorrect. The I-bar should release and thus, should create little danger of torquing the abutment.
Incorrect. Since the WW arm is flexible, it provides some stress-breaking effect and the danger of torquing the abutment should be minimized. Correct. Even though the RPA clasp has a mesial rest, the originating portion of the circumferential clasp will lie above the height of contour and will act like a distal rest on an inclined plane. The tip of the cast arm will now lie in front of the axis of rotation. Incorrect. One of the other choices is much more potentially damaging to the abutment. |
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Which of the following clasps commonly utilize lingual undercuts?
Ring clasp Extended arm clasp Half and half clasp Both 1 and 3 |
4
Both the ring clasp and the half and half clasp use lingual undercuts almost exclusively. |
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Which of the abutments in the partially edentulous arch to the right has the greatest potential for utilization of a ring clasp?
#18 #21 #28 None of the abutments have any potential for the use of a ring clasp. |
1
Ring clasps are used almost exclusively on lower molars that have drifted mesially and lingually. We would generally prefer to use a mesiolingual I-bar but in cases where there is considerable undercut below the abutment, a ring clasp is just about the only alternative. |
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Metal denture bases are most commonly used over well-healed posterior ridges where vertical space is a problem.
True False |
True
The primary indication for metal bases is limited vertical space. However, the ridges should be well-healed because relining is almost impossible. |
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Referring to the partially edentulous arch shown to the right.
The guide plates on teeth 21 and 28 should curve buccolingually and extend lingually just short of the distolingual line angles. True False |
False
The guide plates should extend just beyond the distolingual line angles to provide 180 degree encirclement, bracing, and, in some cases, reciprocation. |
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A cingulum rest should be placed
between the occlusal and middle thirds of the incisor teeth. above the middle third of the incisor teeth. at the junction of the gingival and middle thirds of the incisor teeth. on the disto-incisal edges of the incisor teeth. |
3
Incorrect. Too high. It is difficult to prepare an adequate rest seat and the potential for torquing forces on the abutment teeth are increased. In the maxillary arch there would also be the increased potential for interference with the opposing occlusion. Incorrect. Too high. Same reasoning as for answer #1. Correct. This location places the rest seat and rest just above the cingulum but as low as possible so that potential torquing forces on the abutment are minimized. Incorrect. Totally nonsensical. |
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The external finish line is
the external junction of framework metal and denture base plastic. the external junction of framework metal and supporting tissues. the external junction of the framework metal and the natural teeth. the external junction of the natural teeth and the denture base plastic. |
1
By definition, the external finish line is the external junction of the framework metal and the denture base plastic. |
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As a general rule, a removable partial denture needs C+1 clasps where C=Kennedy classification number.
True False |
True
The "Wiebelt" rule for determining the number of clasps for a removable partial denture. [# of clasps = Kennedy classification + 1] |
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A "bead" line"
is used only on mandibular major connectors is a seal at the interface of framework metal and tissues should taper off as it approaches the marginal gingiva of the abutment teeth both 2 and 3 above |
4
Answer #1 is false. A "bead line" is used only on maxillary major connectors. Answers #2 and #3 are both true so answer #4 becomes the best answer. |
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(Second image does no appear on website)
Your patient has the partially edentulous arch shown in the illustration on the left. Tooth #28 has the survey line and undercut shown in the illustration on the right. There are no contraindications to any type of clasp or to any rest location. What would be your first choice for the clasp assembly on tooth #28? distal rest and cast circumferential clasp distal rest and WW circumferential clasp distal rest and I-bar clasp distal rest and modified T-bar clasp |
4
Incorrect. A circumferential clasp cannot be used when the undercut is located on the side of the tooth (distal in this case) where the clasp originates. Incorrect. A circumferential clasp cannot be used when the undercut is located on the side of the tooth (distal in this case) where the clasp originates. In addition, WW clasps are seldom used on tooth-borne RPDs. Incorrect. In order for an I-bar to be used, the undercut should be just forward of the greatest mesiodistal curvature of the facial surface. Correct. When the undercut is adjacent to the edentulous area, a modified T-bar is an excellent choice, assuming there are not contraindications to the use of an infrabulge clasp. |
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Your patient has the partially edentulous arch shown in the left illustration. Tooth #28 has the survey line and undercut shown in the illustration on the right. There are no contraindications to any type of clasp or to any rest location. What would be the most common choice for the clasp assembly on tooth #28?
distal rest and cast circumferential clasp distal rest and WW circumferential clasp distal rest and I-bar clasp distal rest and modified T-bar clasp |
1
Correct. The RPD is tooth-borne and thus exhibits no functional motion and the undercut is on the opposite side of the tooth from the point of origin of the clasp---a requirement for a circumferential clasp. Incorrect. Although the undercut is appropriate for a distal rest and WW circumferential clasp, there is really no need for WW since there is no functional movement of the prosthesis. #2 is not the best answer. Incorrect. Although a distal rest and I-bar would work, it is not the first choice clasp assembly unless esthetic demands dictate that the clasp be hidden. In this case, the I-bar might be better than a cast circumferential clasp. Not the best answer. Incorrect. Most of the undercut is on the mesiofacial surface, not the distofacial as would be appropriate for a modified T-bar. |
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The superior border of a mandibular lingual bar major connector should be
at least 3 mm from the tooth/tissue junction at least 2 mm from the tooth/tissue junction located at the tooth/tissue junction at least 3 mm above the tooth/tissue junction |
1
The superior border of a lingual bar should be at least 3 mm from the gingival margin---4 mm is preferred. |
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The internal finish line is
the butt joint between the metal and plastic on the tissue side of the edentulous area the butt joint between the metal and plastic on the outer surface of the RPD a type of posterior palatal seal a special type of bead line |
1
Answer #1 is correct by definition. Answer #2 defines the external finish line. Answers #3 and #4 are unrelated to the stem of the question. |
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A class I modification 0 RPD normally has how many clasps?
1 2 3 4 |
2
According to the C+1 rule......1+1 = 2 |
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Select a maxillary major connector for the large Class III modification 1 RPD shown to the right. The residual ridges are good and the abutment teeth are strong.
Palatal strap Modified palatal plate Horse-shoe Anterior-posterior palatal strap |
4
Incorrect. Although it could be used, there would be undesirable tissue coverage---especially since the ridges are good and the abutments strong. Incorrect. A modified palatal plate is used for maxillary class II RPDs. Incorrect. In general, a horse-shoe major connector is undesirable because it lacks rigidity unless quite bulky. It is only used to circumvent large inoperable tori or when the patient is a big-time gagger. Neither of these circumstances are mentioned in the question stem. Correct. These are perfect circumstances for an anterior-posterior palatal strap major connector. The tooth-borne areas are large, the abutments are strong, and the residual ridges are of good size and quality. |
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When an RPD is fully seated, the tips of the clasp arms should exert very light pressure against the abutment teeth.
True False |
False
When the RPD is fully seated, the tips of the clasp arms should exert NO pressure against the abutment teeth---they should be totally passive. |
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Your patient's partially edentulous arch form is shown in the left illustration. The clasp assembly for tooth #20 is illustrated on the right. When is the retentive arm activated?
When the patient bites down on the extension base. When there is an attempt to dislodge the RPD. When the extension base moves toward the tissues. It should never be activated. |
2
Incorrect. When the patient bites down on the extension base, the I-bar should RELEASE. It should only function when there is an attempt to dislodge the RPD, i.e. move it away from the basal seat. Correct. The retentive arm should be activated when dislodging forces attempt to unseat the RPD---movement away from the basal seat. Incorrect. The retentive arm should be activated when dislodging forces attempt to unseat the RPD---movement away from the basal seat. Incorrect. The retentive arm should be activated when dislodging forces attempt to unseat the RPD---movement away from the basal seat. |
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Guide plates for tooth-supported RPDs may extend above the height of contour while those on extension RPDs should not.
True False |
True
Since tooth-supported RPDs exhibit no functional movement, the guide plates may extend above the height of contour. Extension RPDs do exhibit functional movement around an axis of rotation. The axis should pass through the rest closest to the edentulous area. However, if the guide plates next to the edentulous areas extend above the height of contour, they will pre-empt the planned rests and act like rests on inclined planes. The retentive tips would now be in front of the axis of rotation and have the potential for torquing the teeth during functional movements of the extension bases. |
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Select a maxillary major connector for the large Class III modification 1 RPD shown to the right. The residual ridges are of medium quality but the third molar abutment teeth are weak.
A wide single palatal strap An anterior-posterior palatal strap A modified palatal plate A horse-shoe |
1
Correct. A wide palatal strap will add some palatal support to the RPD---a desirable characteristic considering that the abutments are weak. Incorrect. Because of the weak abutments, more palatal support is desirable and a wide palatal strap would be preferred. This is sometimes called a palatal plate because of its breadth. Other people prefer to restrict the term "palatal plate" for the connector used with large class I maxillary RPDs. Incorrect. A modified palatal plate is used for maxillary class II RPDs. Incorrect. In general, a horse-shoe major connector is undesirable because it lacks rigidity unless quite bulky. It is only used to circumvent large inoperable tori or when the patient is a big-time gagger. Neither of these circumstances are mentioned in the question stem. |
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Select a maxillary major connector for the Class III modification 1 RPD shown to the right. The residual ridges are of good quality and the first premolar and second molar abutment teeth are strong.
Anterior-posterior palatal strap Horse-shoe Modified palatal plate Palatal strap |
4
Incorrect. The breadth of the edentulous spaces are too small to use an A-P strap. The opening would almost surely be less than the minimum 15 mm required. Incorrect. In general, a horse-shoe major connector is undesirable because it lacks rigidity unless quite bulky. It is only used to circumvent large inoperable tori or when the patient is a big-time gagger. Neither of these circumstances are mentioned in the question stem. Incorrect. A modified palatal plate is used for maxillary class II RPDs. Correct. The A-P dimension is small, the residual ridges are good, and the abutments are strong---all indications for a palatal strap major connector. |
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Select a maxillary major connector for the Class III modification 1 arch shown to the right. The residual ridges are of good quality and the first premolar and third molar abutment teeth are strong. The patient relates a long history of gagging problems and, in fact, had major problems with the impressions for the study casts.
Anterior-posterior palatal strap Horse-shoe Modified palatal palte Palatal strap |
2
Even though the horse-shoe major connector is not as rigid as other major connectors, it probably will suffice with good ridges and strong abutments. In this patient, the major problem will undoubtedly be gagging and the horse-shoe connector should be more favorable in this regard. |
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(Second picture did not appear on website)
Your patient has the partially edentulous arch shown in the left illustration. Tooth #28 has the survey line and undercut shown in the right drawing. An infrabulge clasp CAN NOT be used due to a very high frenal attachment immediately below the abutment. What would be your first choice for the clasp on tooth #28? A cast circumferential clasp A wrought wire circumferential clasp A cast circumferential embrasure clasp A wrought wire circumferential embrasure clasp |
3
Incorrect. A conventional circumferential clasp cannot be used when the undercut is adjacent to the origin of the clasp (in this case, the distal). Incorrect. Same reason as #1 and there is no reason to use WW since the RPD is totally tooth-borne. Correct. The cast clasp would emanate from a mesial minor connector, pass through the embrasure, cross the facial surface of the tooth and engage the distofacial undercut. Incorrect. Do not use WW through an embrasure. It is difficult to adapt to the occlusal surfaces of the teeth and may interfere with the opposing occlusion. In addition, the slightest nick or kink in the wire will ultimately lead to breakage. |
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If a mandibular RPD abutment must be crowned, the FPD impression should include
all the abutment teeth for the RPD a full arch impression the retromolar pads all of the above |
4
Incorrect. Although the answer is true, it is not the BEST answer. All of the abutment teeth should be included in the impression so that the best path of insertion/dislodgement for ALL abutments can be determined. Incorrect. Although the answer is true, it is not the BEST answer. A full arch impression is required to capture all of the abutments and the retromolar pads. Incorrect. Although the answer is true, it is not the BEST answer. The retromolar pads may be important in helping to establish the plane of occlusion. Although it is true that there would be many circumstances when the plane of occlusion would be entirely determined by the remaining natural teeth, there are also circumstances when the location of the retromolar pads would provide valuable information. Correct. 1, 2, and 3 are all true. |
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A tissue undercut may preclude the selection of
A suprabulge clasp An infrabulge clasp A half and half clasp A combination clasp |
2
Tissue undercuts contraindicate the use of infrabulge clasps because the clasps will stand out in the floor of the mouth or the vestibule and may be irritating to the tongue or lips/cheeks. The other choices for answers are all suprabulge clasps and tissue undercuts have no bearing on these clasps. |
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A combination clasp assembly generally has
a cast bracing arm a distal rest a wrought wire retentive arm all of the above |
4
Answers 1, 2, and 3 are all correct. Therefore, the best answer is #4, "all of the above." |
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Your patient's partially edentulous mandibular arch form is shown to the right. Which of the abutment teeth would be likely to have a combination clasp?
Not likely on any of the abutments #20 very likely; #29 less likely #29 very likely; #20 less likely #31 very likely; not likely on either #20 or #29 |
2
A combination clasp (WW retentive arm, cast bracing arm) is MOST likely on tooth #20 because it lies bodily in front of the axis of rotation. A combination clasp may also be indicated on #29 if the mesial rest, I-bar, distal guide plate clasp assembly cannot be used. |
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A modified T-bar on a terminal abutment for a Class I partially edentulous arch (such as the one shown)
is used with a distal rest is placed into a distobuccal undercut should have the vertical approach arm distal to the greatest mesio-distal curvature of the facial surface both 1 and 2 |
2
Incorrect. It is used with a MESIAL rest. Correct. The tip of the arm is placed in a distobuccal undercut. Incorrect. The vertical approach arm must be placed just to the MESIAL of the greatest mesiodistal curvature of the facial surface. This prevents the arm from releasing upward and backward without providing retention. Incorrect. Since #3 is incorrect, so is #4. |
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Which of the following should be considered in diagnosis for an RPD patient?
interarch space tissue undercuts occlusal contacts all of the above |
4
Answers 1, 2, and 3 are all true and therefore, #4 is the BEST answer. |
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For a removable partial denture abutment that must be crowned, more than the normal occlusal reduction will be required.
True False |
True
The extra reduction is required for the rest seat in the final restoration. |
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A lingual plate mandibular major connector may be selected because
the mandibular incisors are tilted lingually there are mandibular tori present there is a high lingual frenum all of the above |
4
Answers 1, 2, and 3 are all common reasons for selecting a linguoplate mandibular major connector. Therefore, the best answer is 4. |
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A master cast for a RPD should be blocked out and duplicated before
overlapped incisors are recontoured rest preparations are prepared the framework is waxed up all of the above |
3
Incorrect. Overlapped incisors should be recontoured BEFORE the final impression is made and the master cast poured. Incorrect. Rest seat preparations must be completed BEFORE the final impression is made and the master cast poured. Correct. The master cast is blocked out and duplicated---poured in refractory material. Then the framework is waxed up on the refractory cast. Incorrect. Since 1 and 2 are incorrect, 4 is also incorrect. |
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Rest placement on a terminal abutment of a Class I RPD depends on
the opposing occlusion the tilt of the abutment tissue undercuts all of the above |
4
Incorrect. It is a true statement but not the BEST answer. Deep interdigitation or tight contact in a particular fossa may negate its use as a rest area. Incorrect. It is a true statement but not the BEST answer. A tilted terminal abutment may dictate the use of a distal rest and WW clasp assembly because adequate physiologic relief of the guide plate is impossible and the guide plate will pre-empt a planned mesial rest. Incorrect. It is a true statement but not the BEST asnwer. Tissue underucts may negate the use of an infrabulge clasp and, in turn, cause a change in the location of the rest. Correct. 1, 2, and 3 are all true. |
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What is the problem (if any) with the design of the I-bar on tooth #28?
The I-bar should be placed in front of the greatest mesio-distal curvature, not behind it. The I-bar should be placed more distally, closer to the guide plate. The I-bar should extend above the survey line. There is no problem; the position of the I-bar is correct. |
1
Correct. In its current location, there is the possibility that the entire clasp assembly could move upward and backward, allowing the I-bar to escape the undercut without flexing. If this occurred, there would be no retention. Incorrect. It is already too far distal. It needs to be moved anteriorly just in front of the greatest mesiodistal curvature of the facial surface. Incorrect. The I-bar cannot extend above the survey line or it will not release during functional movements of the extension base. Incorrect. There IS a problem. The I-bar is positioned too far distally. |
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Your patient has the arch form shown to the right. You plan to use mesial rests and I-bars but will need to plate the premolars due to the tori. What should be the relationship of the superior border of the plating and the height of contour on the lingual surfaces of teeth numbers 20 and 29?
The plating must end below the height of contour. The plating must end at the height of contour. The plating must end above the height of contour. None of the above is correct. |
2
Incorrect. If the plating ends below the height of contour, there will be a space between the superior edge of the plating and the tooth---a food trap. Correct. The plating must end EXACTLY at the height of contour. Incorrect. If the plating ends above the height of contour, it will pre-empt the planned mesial rest. It will be a rest on an inclined plane (which is no good) and the I-bar will lie in front of the axis of rotation (which is also no good). Incorrect. |
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A general rule for clasping teeth which lie anterior to the axis of rotation (e.g. tooth #21 in the illustration to the right) in a Class II modification 1 RPD is:
Always use cast clasps Never use suprabulge clasps Use wrought wire clasps Use 0.030 inch undercut for stability |
3
Incorrect. NEVER use cast clasps for teeth which lie in front of the axis of rotation. Incorrect. Suprabulge clasps are almost always used in this instance. Correct. WW clasps, because of their flexibility, will tend to place less stress on the anterior abutment when the extension base exhibits functional movement (movement toward the residual ridge). Incorrect. 0.030 inch undercut is three times what is normally used. Even a wrought wire clasp into this amount of undercut would place significant stress on the abutment during functional movement of the extension base. |
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A general rule for rest placement on an abutment adjacent to an extension area is?
Place the rest on the occlusal surface on the opposite side of the tooth from the extension area. Place the rest on the occlusal surface adjacent to the extension area. Place rests on both the mesial and distal occlusal surfaces. Do not place a rest on this tooth. |
1
Correct. This is the general rule. It fits with our preferred clasp assembly of mesial rest, distal guide plate, and I-bar retentive arm. There are certainly many exceptions to the rule. You should know what they are and the reasons for their selection. Incorrect. This would not be your first choice and would not be the general rule. However, there are several exceptions to the general rule. Do you know what they are? Incorrect. There could be instances where rests are placed on both the mesial and distal occlusal surfaces but it would certainly not be the general rule. (An example where both would be used would be the 1/2 and 1/2 clasp). Incorrect. There might be occasions when a rest is not placed on the abutment next to an extension, but this is certainly NOT the general rule. |
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Low fusing metal is associated with which of the following procedures?
The altered cast impression. Physiological adjustment of the framework. The RPD remount cast. Making records for RPDs. |
3
Low fusing metal is used to make the remount cast. It is placed in the areas where natural teeth remain. |
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Physiologic adjustment of the framework
is usually done at delivery of the RPD. should be done at the framework try-in appointment. is usually done at the records appointment. may be omitted in the presence of strong abutments and good residual ridges. |
2
Incorrect. Physiologic adjustment is seldom done at the delivery appointment because the denture bases will prevent the exaggerated functional movement needed to adequately mark areas where the framework binds against the remaining natural teeth. Correct. At the framework try-in appointment, there are no record bases or denture bases to interfere with the exaggerated functional movement required to mark the areas of contact of rigid metal with the natural teeth. Incorrect. Physiologic adjustment is seldom done at the records appointment because the temporary bases will prevent the exaggerated functional movement needed to adquately mark areas where the framework binds against the remaining natural teeth. Incorrect. Physiologic adjustment of the framework should always be done for extension RPDs regardless of the strength of the abutments or quality of the residual ridges. |
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An exception to the C+1 rule for number of clasps is the Class II modification 0 case.
True False |
True
A class II modification 0 RPD generally has 2 clasps not 3. |
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Physiologic adjustment is related to
the axis of rotation adjustment of the framework to the teeth functional movement of the framework all of the above |
4
Incorrect. It is a true statement but not the BEST answer. Marking of the framework for physiologic relief occurs when one creates exaggerated movement of the RPD around the axis of rotation. Physiologic relief is only necessary on those RPDs that have an axis of rotation. Incorrect. It is a true statement but not the BEST answer. The purpose of physiologic adjustment is to adjust the framework to the teeth---to be sure the framework does not bind on the teeth during functional movements of the RPD. Incorrect. It a true statement but not the BEST answer. Functional movement of the framework is an integral part of physiologic relief. Correct. Since 1, 2, and 3 are correct, 4 is the BEST answer. |
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If physiologic adjustment of the framework is not done on a Class I modification 1 RPD, the clasps may not release in function.
True False |
True
If any rigid metal (particularly the guide plates) bind during functional movement of the RPD, this metal will pre-empt the mesial rest and act like a distal rest on an inclined plane. The I-bar will then engage the abutment during functional movement of the RPD--rather than release as it should. |
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The bracing arm of a circumferential clasp assembly must always lie at or above the height of contour.
True False |
True
The bracing arm must be rigid and therefore cannot extend below the height of contour. It could not flex to get into and out of the undercut. |
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Your patient has the partially edentulous arch shown to the right. What would be the best clasps for tooth number 20 and 29 if they were tilted mesially?
Mesial rests and cast I-bars Mesial rests and WW I-bars Distal rests and WW I-bars Distal rests and combination clasps |
4
Incorrect. Because the abutments tilt mesially, the distal guide plates will pre-empt the mesial rests and act like distal rests on inclined planes. Physiologic relief would create a space between the guide plates and the abutments. Thus, it is best to switch to disal rests. Once that decision is made, one must also change the type of retentive arms. Incorrect. With very few exceptions, WW I-bars should be avoided. It is difficult to position them properly, especially in relation to the soft tissues. They are also prone to accidental bending. The other problem here is that, because the abutments are tilted mesially, the guide plates will pre-empt the mesial rests. Thus, distal rests should be selected. Incorrect. Same reasoning as #3. Correct. Because the abutments tilt mesially, the distal guide plates would pre-empt the mesial rests and act like distal rests on inclined planes. Physiologic relief would create a space between the guide plates and the abutments. Thus, it is best to use distal rests. Once that decision is made, one must also change the type of retentive arms to WW circumferential clasps. Fortunately, when teeth are tilted mesially, there are almost always mesiofacial undercuts appropriate for WW circumferential retentive arms. |
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Your patient has the partially edentulous arch shown to the right. The premolars are tilted lingually and there are no facial undercuts. There are, however, undercuts on the lingual. What would be the best clasps for this situation?
Lingual I-bars Roach clasps Akers clasps Half and Half clasps |
4
Incorrect. Lingual I-bars can ONLY be used on lower molars. Incorrect. A Roach clasp is an infrabulge clasp that generally utilizes a facial undercut---like an I-bar or modified T-bar. This type of clasp cannot be used here because there are no facial undercuts---infrabulge clasps cannot be used on the lingual surfaces of premolars. Incorrect. An "Akers" clasp is a circumferential clasp. A conventional circumferential clasp cannot be used because there are no facial undercuts. Correct. The half and half clasp is appropriate for the circumstances described in the stem of the question. Because this type of clasp neither totally releases during function nor exhibits great flexibility, its use is reserved for those rare cases where almost no other options remain. |
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The external finish line on a maxillary Class I RPD originates from the lingual of the guide plate of the terminal abutment and ends
at the hamular notch. in the glenoid fossa. opposite the buccal pouch. opposite Stenson's duct. |
1
The finish line ends at the hamular notch. The other answers make no sense. |
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The open latticework on a maxillary class I RPD
covers the hamular notch. covers the tuberosity. does not cover the tuberosity. does not require substantial interach space. |
3
Incorrect. It does not extend back to the hamular notch. Incorrect. Interarch space limitations usually preclude extension over the tuberosity. Correct. Interarch space limitations usually preclude extension over the tuberosity. Incorrect. Open latticework does require substantial interarch space. That's the reason it does not usually extend backward to cover the tuberosity. |
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The partial denture design should be finalized prior to
any emergency treatment. any fixed prosthodontic treatment. preparation of rest seats. both 2 and 3 above. |
4
Incorrect. Emergency treatment can be done prior to the development of the RPD design. This is often simply a matter of getting the patient out of pain. Even under these circumstances, it is best if one has a general idea of the ultimate design---so that potentially useful teeth are not extracted. Incorrect. A true statement but not the BEST answer. Incorrect. A true statement but not the BEST answer. Correct. Answers 2 and 3 are correct so 4 is the BEST answer. Only emergency treatment should be done prior to development of the RPD design. |
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Your patient has the partially edentulous arch shown to the right. The root of #29 has been saved as an overdenture abutment.
True or False The presence of the overdenture abutment may change the axis of rotation but will not change the clasping considerations on tooth #28. True False |
False
The overdenture abutment may change the axis of rotation and in doing so would unquestionably affect the clasping of tooth #28. Therefore, the answer is false. |
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When placing the tripod marks on the diagnostic cast, the vertical arm of the surveyor
should have the analyzing rod in place. should be moved up or down to touch the tissues at widely separated areas. Both 1 and 2 are true Neither 1 nor 2 are true |
4
Incorrect. The lead should be in the vertical arm. Incorrect. The vertical arm must be locked in position so that the three marks will determine a plane that can be used to reorient the cast. Incorrect. #3 is incorrect since #1 and #2 are incorrect. Correct. Neither #1 nor #2 are correct. |
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The internal and external finish lines are
normally superimposed over each other. normally offset from each other to avoid weakness in the framework. normally designed and placed independently. none of the above statements are true. |
2
The finish lines must be offset. If they are superimposed over each other, substantial weakness in the framework is created and fracture in this area would be very likely. |
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In general, lingual plating should be supported
by the inclined surfaces of the mandibular incisors. with minor connectors. with bracing arms. with rests. |
4
Linguoplating should be supported by rests placed in rest seats (at least on the canines). Of course, the rests are under the plating and would not be visible when the RPD is in place. Without the rest seats and rests, the plating would lie totally on inclined planes and could, over time, move the teeth toward the facial. |
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A maxillary arch without three contiguous incisors (such as the one shown)
usually requires plating of the remaining incisor should not be plated should have a horse-shoe major connector both 1 and 3 above. |
1
Correct. As a general rule, if there are not three contiguous incisors present, the remaining incisor should be plated. Incorrect. See #1 above. Incorrect. A horse-shoe major connector is related to the presence of a torus or to gagging. It has nothing to do with the presence or absence of three contiguous incisors. Incorrect. Although #1 is correct, #3 is incorrect. Thus, #4 is incorrect. |
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The external finish line on the distal extension side of the mandibular Class II modification 1 RPD for the partially edentulous arch shown to the right
runs from the lingual frenum to the retromolar pad. runs from the lingual of the guide plate to the floor of the mouth. runs from the mesial of the guide plate to the retromolar pad. cannot be determined without more information. |
2
Incorrect. It simply makes no sense. Correct. The statement accurately describes the location of the external finish line. Incorrect. The finish line is located at the distal of the terminal abutment. It does not run posteriorly from that point. Incorrect. The external finish line is fairly standard in this situation and depends very little on any diagnostic information. |
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Wrought wire retentive arms are usually selected for distal extension RPDs when the tips of the arms lie behind the axis of rotation.
True False |
False
WW clasps are usually selected for distal extension RPDs when the retentive tips lie in front of the axis of rotation. |
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Occlusal rest preparations should be
spoon shaped at least 1/3 the buccolingual width of the occlusal surface at least one millimeter deep all of the above |
4
Incorrect. A true statement but not the BEST answer. Rest seat preparations should be rounded and "spoon-shaped". This is particularly important in extension RPDs where the prosthesis needs to be able to rotate around the rests during functional movement. Incorrect. A true statement but not the BEST answer. The width of the occlusal rest seat is at least 1/3 the total width of the occlusal surface but more often approaches 1/2 of the distance between the buccal and lingual cusp tips. Incorrect. A true statement but not the BEST answer. Rest seat preparations must be at least 1 mm deep. Correct. Since 1, 2, and 3 are all true, #4 is the BEST answer. |
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Guide plates for anterior teeth
should be kept to the labial for best esthetics. should be kept to the lingual for best esthetics. be thinned on the labial aspect. both 2 and 3 above. |
4
Incorrect. The metal should be cut back and thinned on the labial, not extended in the labial direction. Incorrect. The statement is true but #2 is not the BEST answer. The guide plate should be positioned as much as possible to the lingual to limit the visible metal on the finished prosthesis. Incorrect. The statement is true but #3 is not the BEST answer. The labial aspect of the guide plate should be thinned so that the artificial tooth or teeth can be shaped and positioned to avoid exposure of metal. Correct. Both 2 and 3 are true statements so 4 is the BEST answer. |
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An anterior-posterior palatal strap major connector is less rigid than a horse-shoe major connnector because it (the A-P strap) has less width.
The first statement is true but the reason is false. The first statement is false and the reason is also a false statement. The first statement is true and the reason is true. The first statement is false but the reason is a true statement. |
4
The anterior-posterior strap is more rigid than the horse-shoe connector unless the horse-shoe is made very bulky. The anterior-posterior strap has good rigidity in spite of the fact that it is very thin, due to the closed circle design and the fact that the metal lies in many different planes. |
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Your patient has the partially edentulous arch form shown. All of the abutments have good bone support. On which one of the abutments would you likely utilize a WW clasp?
#22 #29 #32 None of the above. |
4
WW clasps would not be used on any of the abutments unless the prognosis for the molars was poor and there was a plan to re-adapt the RPD when the molars were lost. That is not the situation described in the stem of the question. |
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Which of the following clasp assemblies utilize a primary rest and an auxiliary rest?
RPA clasp Ring clasp Infrabulge clasp Extended arm clasp |
2
A ring clasp has both a mesial primary rest and a distal auxiliary rest. It is used almost exclusively on mandibular mesiolingually tilted molar abutments. |
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In a circumferential clasp assembly, only one of the arms may extend into an undercut.
True False |
True
One arm, the retentive arm, extends into an undercut. The other arm, the bracing or reciprocating arm, must be rigid and therefore, cannot extend into an undercut. |
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Which of the following steps is done LAST?
Rest preparation Framework try-in Centric relation records Altered cast impression |
3
Incorrect. Of the steps listed, rest preparation is the first accomplished. Incorrect. Framework try-in must be completed before both the altered cast impression and records. Correct. Centric relation records are generally done after the framework has been tried in and the altered cast impression made and poured. Record bases are then added and the CR record is made using these bases. Incorrect. The altered cast impression is made before centric relation records are made. |
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Incisal rests
are generally more positive vertical stops than cingulum rests. may interfere with the opposing occlusion. should not be used on maxillary incisors. all of the above. |
4
Incorrect. The statement is true but not the BEST answer. Incisal rests on lower anteriors are generally used when the lingual slope of the teeth is so steep that adquate rest seats cannot be prepared. If the rest seats and rests "hook" over the incisal edges of the teeth, the rests will provide very positive vertical stops. Incorrect. The statement is true but not the BEST answer. Incisal rests certainly may interfere with the opposing occlusion. For this reason, the incisal rest seat must be deep enough that most or all of the rest will sit within the confines of the rest seat. Incorrect. The statement is true but not the BEST answer. Incisal rests should not be used on maxillary incisors because of esthetic considerations and because the minor connector between the major connector and the rest often interferes with the occlusion. Correct. #4 is the BEST answer because 1, 2, and 3 are all true statements. |
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Cast retentive arms are usually selected when the RPD is tooth supported or when the retentive tips release during functional movements of extension RPDs.
True False |
True
The statement accurately describes when cast retentive arms are usually selected. |
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Cleaning a removable partial denture in sodium hypochlorite may result in
increased caries activity increased periodontal problems corrosion of the metal of the framework 1 and 2 above |
3
Since sodium hypochlorite may cause corrosion of the metal of the RPD framework, it is not recommended for cleaning solutions for partial prostheses. |
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Which of the following clasp assemblies utilizes a lingual undercut and can be used on premolars for either extension or tooth-supported RPDs?
half and half clasp lingual I-bar lingual modified T-bar ring clasp |
1
Correct. Although certainly not a "first choice" retainer, half and half clasps are used to engage lingual undercuts and can be used on both extension and tooth-supported RPDs. Incorrect. Lingual I-bars are only used on lower molars. Incorrect. Lingual modified T-bars are seldom if ever used on any tooth. Incorrect. A ring clasp utilizes a lingual undercut but is only used on molars. |
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If a metal base is to be used
an altered cast impression should be made after framework try-in a stock tray should be used for the final impression a custom tray should be used for the final impression interocclusal records must be made after tooth selection |
3
Incorrect. An altered cast cannot be done because the metal base must be incorporated into the framework. Incorrect. A stock tray should not be used for the final impression as it is important to get an accurate, undistorted impression of the residual ridges and surrounding soft tissues. Correct. A custom tray should be used as it is important to get an accurate, undistorted impression of the residual ridges and surrounding soft tissues. The metal base will be incorporated into the framework. Incorrect. Interocclusal records would be made before tooth selection. The records could be made either before or after framework fabrication (usually after but if the interocclusal distance is very small and metal teeth are to be incorporated with the base, records would have to be made before the framework is fabricated). |
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When surveying to determine the height of contour of the abutments, the mark on the tooth must be made by the side of the lead marker.
True False |
True
The survey line must be made by the side of the lead marker. Otherwise there could and probably would be marks on the tooth that do not represent the height of contour. These would be very deceiving when formulating a design. |
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Clasps
help stabilize the RPD by controlling occlusal movement. help stabilize the RPD by controlling gingival movement. may also function as indirect retainers. prevent excessive biting forces on the abutments. |
1
Correct. The primary purpose of clasps is to resist movement of the RPD occlusally or away from the tissues and teeth---to resist dislodging forces. Incorrect. Gingival movement is prevented or controlled primarily by rests. Gingival movement may also be prevented to a very minor degree by the rigid portions of clasps but remember, these elements lie on inclined planes and cannot be the primary elements resisting gingival movement of the prosthesis. #2 is definitely not the BEST answer. Incorrect. Clasps do not function as indirect retainers. Rests and sometimes plating (supported by rests) serve this function. Incorrect. Clasps have nothing to do with preventing or controlling biting forces on the abutments---unless one made the rather remote argument that rigid portions of clasps help control horizontal components of biting forces. #4 is not the BEST answer. |
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Your patient exhibits the partially edentulous arch shown to the right. Tooth #29 is tilted mesially. The undercut is on the mesiofacial surface. What would be the best clasp assembly for this situation?
Distal rest and cast circumferential clasp. Distal rest and WW circumferential clasp. Mesial rest and I-bar. Distal rest and I-bar. |
2
Incorrect. The tip of the clasp would lie in front of the axis of rotation and the cast clasp has minimal flexibility. Correct. You must use a distal rest because of the angulation of the tooth. Otherwise the guide plate will pre-empt the planned mesial rest and will act like a rest on an inclined plane. Attempts to physiologically relieve the guide plate would result in a space between the guide plate and the distal proximal surface of the tooth creating an unacceptable food trap. Once you have decided to use a distal rest, you must use a clasp with maximum flexibility (WW). Incorrect. Because of the tilt of the tooth, the distal guide plate will pre-empt the mesial rest and will act like a rest on an inclined plane. The I-bar would now be a cast clasp in front of the axis of rotation. Incorrect. The I-bar would be a cast clasp in front of the axis of rotation. |
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During biting, a maxillary Class I RPD will rotate around a line determined by the rigid metal above the survey line and closest to the extension areas. This line is called
Camper's line Frankfurt line Dual path line Axis of rotation |
4
Incorrect. Camper's line has nothing to do with RPD design. Incorrect. There is no such thing as Frankfort's line. Incorrect. There is no such term as "dual path line." Correct. If extension RPDs are properly designed, this line should pass through the most distal rests. To be sure this is true, one must be careful that there is no other rigid metal above the survey line that is closer to the edentulous segments. |
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The WORST clasp assembly for a terminal abutment on a mandibular class I RPD (such as #29 in the partially edentulous arch to the right) is
Mesial rest and I-bar Distal rest and cast circumferential clasp Mesial and distal rest and a 1/2 and 1/2 clasp Mesial rest and modified T-bar |
2
Incorrect. A mesial rest and an I-bar is the BEST choice. Correct. A distal rest and cast circumferential clasp has the greatest potential for torquing the abutment during functional movement of the extension base. Incorrect. Although the half and half clasp is not our first choice retainer, it is acceptable when lack of a facial undercut necessitates the use of a lingual undercut. Incorrect. A mesial rest and modified T-bar is an acceptable clasp assembly when the undercut is on the distofacial surface and when there is no contraindication to the use of a bar (infrabulge) clasp. |
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The guide surface preparation should be curved
mesio-distally bucco-lingually occluso-gingivally none of the above |
2
Incorrect. Guide surfaces (and guide plates) are seldom placed on the buccal or lingual surfaces---the only ones that could curve mesiodistally. Correct. Guide surfaces and guide plates should follow the natural buccolingual curvature of the tooth. Incorrect. Guide surface preparations and guide plates should be vertically parallel to the established path of insertion/dislodgement---not curved occluso-gingivally. Incorrect. |
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Fill in the blank
What are the indications for a linguoplate as a major connector for a mandibular RPD? |
The correct answer is
High floor of the mouth (<7 mm of vertical height) High lingual frenum Presence of lingual tori One or more missing incisors Periodontially involved incisors with possible loss in the future Lingually tilted mandibular anterior teeth |
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Fill in the blank.
Name four types of suprabulge clasps. |
The correct answer is
Circumferential Embrasure Ring Hairpin |
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Fill in the blank.
Your patient has teeth numbers 20 through 29 remaining. The illustration to the right shows the design for a modified T-bar retainer on tooth #29. The vertical line on the tooth represents the greatest mesiodistal curvature of the facial surface. Do you see any problems with the design? |
The correct answer is
The approach arm of the modified T-bar must be placed just to the mesial of the greatest mesio-distal curvature of the facial surface. Otherwise there is the possibility that the entire RPD could be displaced upward and backward without the retentive arm flexing. In this case, the RPD would exhibit no retention. |
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Fill in the blank
In the illustration shown to the right, what would be your first choice for a retainer (clasp) on tooth #6? |
The correct answer is
Wrought wire circumferential clasp |
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Fill in the blank
Your patient has the partially edentulous arch shown to the right. The molars have drifted mesially and lingually so that the only usable undercuts are on the mesiolingual. What clasps would you use on the molars if (1) there were no large tissue undercuts and (2) there were large tissue undercuts? |
The answer is
Part 1: mesiolingual I-bars Part 2: ring clasps with rigid facial portions and auxiliary distal rests |
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Fill in the blank
Which classes of mandibular RPDs require an altered cast impression? |
The correct answer is
Classes I and II |
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Fill in the blank
Important factors in determining the path of insertion/dislodgement are: |
The correct answer is
1. potential guide surfaces 2. undercuts for direct retention 3. hard and soft tissue interferences 4. esthetic considerations |
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Fill in the blank
Incisal rests should generally not be used on maxillary incisors. Why? |
The correct answer is
Poor esthetics and interferences with the opposing occlusion. |
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Fill in the blank
For tooth-supported RPDs, where are the primary rests normally placed? |
The correct answer is
In tooth-supported RPDs, primary rests are usually located on the tooth next to the edentulous space and on the portion of the occlusal surface immediately adjacent to the edentulous space---thus avoiding additional minor connectors and gingival coverage. |
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Fill in the blank
For extension RPDs, where are the primary rests usually placed? |
The correct answer is
On the tooth next to the edentulous space but on the portion of the occlusal surface away from the edentulous space. |
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Fill in the blank
What is/are the indications for the use of a maxillary palatal plate major connector which is composed partly of metal and partly of plastic? See example to the right. |
The correct answer is
Plastic in the posterior aspect of the major connector allows for post-insertion revision of the posterior palatal seal and for relining or rebasing over residual ridges that are still in the process of recontouring (healing). |
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Fill in the blank
What are the indications for the use of a maxillary horseshoe major connector? |
The correct answer is
A horse-shoe or U-shaped maxillary major connector is indicated when a large, inoperable torus extends posteriorly within 8 mm or less of the junction of the hard and soft palates or when the patient cannot tolerate contact of the prosthesis with the posterior portion of the palate---a gagger! |
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Fill in the blank
The total retention for a RPD is obtained from |
The correct answer is
1. denture style retention (adhesion, cohesion, interfacial surface tension) 2. frictional retention from guide surface/guide plate contacts 3. mechanical retention from clasps (direct retention) |
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Fill in the blank
What are the components of a clasp assembly? |
The correct answer is
1. one or two rests 2. a retentive arm 3. a bracing or reciprocating element 4. one or more minor connectors |
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Fill in the blank
An ideal clasp assembly should possess the following qualities: |
The correct answer is
1. support 2. bracing 3. reciprocation 4. 180 degree encirclement |
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SUPPORT for a RPD framework is provided by?
|
The correct answer is
Support is provided almost entirely by rests. Some support is furnished by other rigid metal located above the survey line (e.g. the rigid portions of retentive arms and bracing and reciprocating arms). However, these components usually lie on inclined surfaces and should never be expected to provide primary vertical support. In the maxillary arch, some support may also be provided by the major connector if it covers a significant portion of the hard palate. When considering the RPD as a whole, the denture bases also provide support, much more so in extension RPDs than tooth-supported RPDs. |
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Fill in the blank
Explain the difference between bracing and reciprocation. |
The answer is
Bracing and reciprocation are both provided by rigid portions of clasps, guide plates, and minor connectors. Under certain circumstances, linguoplating may also provide bracing and reciprocation. Bracing occurs when the RPD is fully seated. Bracing elements distribute horizontal forces across the arch. Reciprocation is dynamic and requires timing. The rigid elements must contact the abutment teeth as the retentive arms pass over the height of contour during insertion and removal of the prosthesis. |
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Fill in the blank
Factors important in the selection of a particular clasp design include? |
The correct answer is
1. tooth contour (location of undercut) 2. tissue contour 3. flexibility of the clasp arm 4. tooth coverage 5. esthetic requirements 6. the capacity for adjustment, maintenance, and replacement 7. the ability to provide stabilization (bracing) |
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Fill in the blank
What are indirect retainers and how do they function? |
The correct answer is
Indirect retainers are rests that are located anterior to the retentive arms on distal extension RPDs. They function when dislodging forces attempt to move the denture base away from the basal seat tissues. By preventing downward movement of the anterior portion of the RPD, the indirect retainers force the direct retainers (clasps) to activate when movement away from the basal seat is attempted. |
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Fill in the blank
______________________________ are mechanical retainers that originate from a point at or above the height of contour---usually from a rest, minor connector, or guide plate---and angle downward across the clinical crown where the tip is located in the prescribed undercut. |
The correct answer is
Suprabulge retainers |
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For a circumferential clasp, the undercut must be located
on the same side of the abutment as the point of origin. on the opposite side of the point of origin. |
2
on the opposite side |
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Fill in the blank
What is a combination clasp? |
The correct answer is
A combination clasp is a circumferential clasp assembly composed of a rest, a flexible wrought wire retentive arm, and a rigid cast reciprocating/bracing arm. |
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Fill in the blank
When is a combination clasp most commonly used? |
The correct answer is
The combination clasp is most commonly used for extension RPDs when 1. a tissue undercut below the terminal abutment precludes the use of a bar clasp 2. the mesial tilt of the terminal abutment would cause the guide plate to pre-empt the mesial rest in an I-bar clasp assembly 3. a retainer is placed on a tooth that lies bodily in front of the axis of rotation |
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Fill in the blank
What is the "RPA" clasp concept and what is the problem with the design? |
The correct answer is
The RPA concept has occasionally been recommended for distal extension RPDs and includes a distal guide plate, a mesial rest, and a circumferential retentive arm originating from the guide plate. Problem: If the originating portion of the arm lies above the height of contour, it will pre-empt the mesial rest and will act like a distal rest on an inclined plane. The retentive tip will now engage the undercut during functional movement of the extension base. |
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Fill in the blank
What is the name of the clasp assembly shown to the right? |
The correct answer is
The picture shows an embrasure clasp assembly (which is a type of circumferential or suprabulge clasp). |
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Fill in the blank
What is the most significant error in the design shown to the right. (Hint: the error is not particularly easy to see but it involves the major connector.) |
The correct answer is
The biggest problem with the design is that the major connector ends in the gingival sulcus of the anterior teeth. If the intent is to plate these teeth, the plating must cover the cinguli and extend interproximally up to the contact points. If plating is not desired, the border of the major connector must be at least 6 mm away from the gingival margins. |
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Fill in the blank
The illustration shown to the right was taken from an advertisement that appeared in one of the dental journals. It suggests that a bar bridge/splint in combination with a precision or semi-precision removable partial denture is appropriate treatment for "Geriatric Reconstruction." What do you think about this type of treatment? |
There are many problems with this type of treatment for a large percentage of geriatrics patients. First of all, many older patients simply do not have the manual dexterity to control the precise insertion and removal of this type of prosthesis. Secondly, the splinting of teeth means the only means of assuring adequate interproximal plaque control by use of floss threaders under the soldered contacts---also a very difficult task for people with marginal coordination and dexterity. In general, one could say that plaque control is more difficult for the geriatric population than for younger patients. Recurrent decay around crown margins is common among geriatric patients. Whenever possible, margins should be as accessible as possible---that is not the case with this type of restoration.
The rule of "KISS" (keep it simple stupid) may not have the best connotation but is true most of the time and certainly in relation to removable prostheses for geriatric patients. Make insertion and removal of the prosthesis as easy as possible. Avoid precision attachments and the like. Allow for repair of the underlying restorations and design the RPD so that teeth can be added to the prosthesis if natural teeth are lost. Don't do anything that will compromise oral hygiene. |
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Fill in the blank
The illustration to the right shows the tissue surface of a maxillary removable partial denture. The arrows point to the junction of the framework metal and the plastic denture base. What is this structure called? |
The correct answer is
Internal finish line |
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Fill in the blank
The illustration to the right shows a tooth-supported segment of a mandibular removable partial denture framework. The red arrow is pointing to the raised edge of metal where the framework and plastic denture base will meet. What is this structure called? |
The correct answer is
External finish line |
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Fill in the blank
The illustration to the right shows a maxillary class I RPD framework with an anterior-posterior palatal strap major connector. What is the minimum acceptable distance between the anterior and posterior straps (red arrow)? |
The correct answer is
15 mm. |
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Fill in the blank
What Kennedy classification is the RPD shown in the picture to the right? What is the name of this type of major connector? |
The correct answer is
Class II, modification 0 Modified palatal plate |
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Fill in the blank
What is the Kennedy classification of the maxillary RPD shown to the right? |
The correct answer is
Class III, modification 0 |
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Fill in the blank
What is the Kennedy classification of the maxillary RPD shown to the right? |
The correct answer is
Class III, modification 1. If tooth #14 had not been missing, it would have been a Class IV. However, no modification spaces are possible in a class IV RPD---any other edentulous area takes precedence in nomenclature. |
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Fill in the blank
The red arrows point to a "ridge" of metal on the framework where the framework and the denture base plastic will meet. What is this "ridge" called? |
The correct answer is
External finish line |
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Fill in the blank
The illustration to the right shows a tooth-borne segment of a mandibular RPD. There is an I-bar retainer on the molar abutment. What is unusual about this retainer? |
The correct answer is
Generally, lingual I-bars on lower molars should be placed at the mesiolingual corner of the abutment. This helps prevent the approach portion of the arm from standing out in the floor of the mouth and irritating the tongue. Will this arm work? Probably. There is very little tooth or tissue undercut so the arm may not stand out in the floor of the mouth even though it is positioned further posteriorly than would usually be desired. |
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Fill in the blank
The illustrations above show a very large maxillary RPD and a close-up of one of the retentive arms. What type of retentive arms have been used on this prosthesis? |
The correct answer is
Oddo hinge clasp |
