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59 Cards in this Set
- Front
- Back
Inherent problems of orthodontic banding 3
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- Teeth require separation which needs extra appointment and minor discomfort
- Bands require intermediate cementing medium regardless of how well they are contoured to tooth surface - Non-resin (Zinc Phosphate) cements are soluble in saliva and property can lead to cement wash out, demin, and caries |
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Definition of Direct Bonding
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Using acid etch and adhesive resins to apply orthodontic brackets and attachments directly to the teeth without need for circumferential metal bands
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Three types of bonding resins
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1) Unfilled: Bracket bond
2) Lightly filled: Up to 30% Inorganic fillers 3) Heavily filled: 60-70% fillers |
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Bonding products that require use of intermediate resin (Sealant)
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Need intermediate Resin (CUNB)
- Concise - Unique - Nuva Tach - Bondmor I and II Others do not need an intermediate resin |
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Metal bases for bonding
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Brackets
- Plastic: Polycarbonate - Metal: Stainless steel Base of metal brackets that contact bonding resins - Perforated - Multi-perforated - Foil mesh-backed - Undercut with holes or slots - Foil mesh-backed or undercut with holes are the base of choice |
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Difference in mechanism of adhesion between plastic and metal brackets
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Plastic
- Chemical reaction between polycarbonate bracket base and acrylic monomer - Base of bracket is treated with primer coating immediately prior to bonding - Primer composed to methyl methacrylate or acetone softens base of plastic bracket enabling a chemical reaction with resin to occur Metal brackets - Retained by mechanical interlocking of resin through perforations, mesh, or undercut areas of bracket base - No chemical bonding - No primer needed |
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Problems with plastic brackets 5
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- Stress cracking and fracture along lines of stress
- Flexible so will bend and soften - Easily wear due to friction from wires - Stain and discolor from tobacco, smoke, tea, coffee, and cosmetic products - Not all bonding materials are compatible with plastic brackets |
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Three principle steps in de-bonding protocol
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- Removal of bracket
- Removal of resin bulk - Restoration of pre-treatment characteristics of the tooth surface |
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Removal Modalities suggested for debonding
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Hand instruments
- Pliers - Knives - Scalers - Hand instruments cause ditching and chipping Rotary - Diamond burs - Stones - Finishing burs - Rubber wheels - Cups and Slurries - Rotary instruments cause grooving, ditching, and cratering - High speed rotary causes grooving and scalloping Ultrasonic instruments - Ultrasonic is slow and causes ditching and cratering |
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Know considerations involved in debonding
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- Type of resin used: Highly filled resins are more difficult to remove
- Removal modality, Chair time, Patient comfort - Restoration of enamel surface 1) Restore natural esthetics polishing 2) Remove gross and minute resin remnants 3) Restore enamel surface smoothness |
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Objectives in de-bonding protocol
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- Remove bracket with ligature cutter or bracket removing plier using a peel force
- Reduce resin down to natural tooth contour with air-cooled green medium Dedico rubber wheel - Polish enamel with fine pumpce slurry and rubber cup |
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Primary sites of plaque accumulation
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- Plaque will accumulate on bonding resins even with patients who have good oral hygiene
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Plaque accumulation on Resin Surfaces
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- Preferential wear of resin matrix exposes filler particles to produce a roughened surface
- Both lightly and heavily filled resins are predisposed to plaque formation without significant qualitative differences between them |
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Most common location for demineralization using direct bonding
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- Junction between bonding resin and enamel. Just peripheral and commonly gingival to bracket base
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Two factors related to plaque accumulation during direct bonding brackets
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Strict bonding protocol
- Use only enough material to cover base of bracket - Remove any excess resin around the periphery - Keep resin as far away from gingiva as possible Rigorous Home Care program - Brushing, Oral irrigation devices, Topical flouride by rinsing |
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Bracket of choice for Hygiene
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Mesh back has tendency to have less plaque accumulation than perforated base
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Advantage and Disadvantage of direct bonding techniques
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Advantage
- No separation - No subgingival placement of metal - No band material located interproximally to usurp arch space - No disfiguring decalcification beneath bands - More esthetic - Radiographs can be taken periodically Disadvantage - Higher failure rate on posterior teeth - Plastic brackets soften and discolor - Replacement of lost or broken brackets are pain - Demineralization and Caries are still problem - Use on lower incisors in deep bites are difficult - Resin material has short shelf life |
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Two main reasons to extract
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- Provide space to align remaining teeth in presence of severe crowding
- To allow teeth to be moved to reduce protrusion or to hide class 2 or 3 problems |
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Extraction guidelines
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Less than 4mm discrepancy
- Exo rarely indicated - Only if there is severe incisor protrusion or vertical discrepancy 5-9mm discrepancy - Non exo or exo depending on both hard and soft tissue characteristics and how final position of incisors are controlled - Any of several teeth could be chosen - Non-exo treatment usually requires transverse expansion across molars and premolars 10mm or more - Exo almost always required - Four 1st premolars or upper premolars and mandibular laterals |
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Transverse Maxillary Deficiency corrections
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Best way to correct is to grow out of it - unlikely without treatment
Transverse Maxillary Deficiency - Rapid or slow expander - Induce new bone growth - Clinically evident because diastema forms |
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Class II corrections
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Class II general
- Modifications tend to be diminished or eliminated by subsequent growth - Alignment and Occlusion are similar in children who did not have early treatment and those who did - Chances of trauma to protruding upper incisors reduced by early tx - Signs of TMD reduced by early tx Short face class II - Mandible catch up with maxilla - Block eruption of incisors - Control eruption of Upper posterior teeth - Facilitate eruption of lower posterior teeth - Most effective with *Activator-Bionator type Class II with normal height - Equal success with two stage headgear or functional appliance in stage 1 or with one-stage tx during adolescence - Either headgear or any type of functional appliance is acceptable - Straight pull or high pull is preferred over cervical to reduce elongation of maxillary molars and control inclination of mandibular plane - Appliances that minimize tooth movement are preferred to maximize skeletal effects and minimize compensatory tooth movement Class II with long face: Skeletal open bite - Goal is to restrain vertical development and encourage anteroposterior mandibular growth while controlling tooth eruption in both jaws Hierarchy of effectiveness - High pull headgear to functional with bite blocks - Biteblocks on functional appliance - High-pull headgear to maxillary splint - High-pull headgear to molars |
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Class III problems corrections
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Horizontal-Vertical Maxillary Deficiency
- Headgear to compress or reverse(Forward-pull) headgear to stimulate growth - Mandibular excess adjusted via chin cup |
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Treatment planning of patients with multiple problems
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1) Disease control
- Caries control - Endodontics - Initial periodontics (No osseous) - Initial restorative (No case restoration) 2) Establishment of occlusion - Orthodontics - Orthognathics - Periodontal maintenance 3) Definitive Periodontics (Including osseous) 4) Definitive restorations - Cast restorations - Splints, Partial dentures |
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Treatment relating to Periodontics and Orthodontics
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- Perio must be under control to prevent irreversible damage to periodontium
- OHI is a must due to bracket plaque retention - Ortho changes soft tissue and bone contour Severe perio - Ortho forces kept to minimum due to reduced PDL area - Greater attachment loss so less supported root and center of resistance becomes closer to apex - Further force application from center of resistance results in greater tipping |
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When ortho treatment is initiated prior to elimination of inflammation
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More harm than good
- Uncontrolled recession - Excessive tipping - More advanced perio problems because plaque control is difficult 6 Months must be allowed for healing and resolution of inflammation before tooth movement |
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Factors that retard action of bone remodeling in adult patient
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- After several years, resorption results leaving less vertical bone height and buccal-lingual narrowing of alveolar process
- Cortical bone will respond to ortho but is slower due to reshaping of cortical bone comprises buccal and lingual plates |
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Stress vs Strain
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Stress - Internal distribution of load. Force per unit area
Strain - Internal distortion produced by the load. Deflection per unit length |
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Force and Deflection
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- Response to a force can be measured as the deflection produced by force aka bending or twisting
- Internal stress and strain can be calculated from force and deflection by considering area and length of beam |
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Three major properties of beam materials
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Strength: Three points
- Proportional limit: Point at which any permanent deformation is observed. aka Elastic limit - Yield strength: Point at which a deformation of 0.1% is observed - Ultimate tensile strength: Maximum load the wire can sustain. Stiffness or Springiness - Reciprocal properties - Proportional to slope of elastic portion of force-deflection curve - More horizontal the slope, the springier. More vertical is more stiff Range - Distance wire will bend before permanent deformation - If deflected beyond yield str, will not return to original str - Springback can be used and is measured along horizontal axis of force-deflection curve - Often times, orthodontic wires are deformed beyond their elastic limit **Strength = Stiffness x Range** |
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Resilience vs Formability
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Resilience - Area under stress-strain curve representing energy storage capacity. Combination of Strength and Springiness
Formability - Amount of permanent deformation that a wire can withstand before failing/breaking |
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Properties of an idea Ortho wire
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High strength
Low stiffness High range High formability Should be weldable or soderable and of reasonable cost |
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Precious Metal alloys
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- Gold is too soft but alloys with Pt, Pd, Co are useful
- Introduction of stainless steel made them obsolete - Only Crozat appliance is occasionally made of gold |
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Stainless steel and Cobalt-Chromium Alloys
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- Better strength and springiness with equivalent corrosion resistance compared to precious metals
- Rust resistance is due to high Chromium content - Elgiloy is supplied in a softer and more formable state and then hardened by heat treatment to increase strength - After heat treatment, softest Elgiloy is equivalent to regular stainless steel |
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Nickle Titanium Alloys
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- Shape memory and superelasticity due to phase transitions within NiTi alloy
- Martensite form at lower temps and Austenite at high temps - Remembers original shape after being deformed in Martensitic form. Restores to original shape when heated again A-NiTi - produces a hardly varying force, unloading curve differs from loading curve. Preferred material when long range of activation with relatively constant force is needed M-NiTi - Useful in later stages for flexible but larger stiffer wires |
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Beta Titanium
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- Highly desirable combination of Strength and Springiness with good formability
- Good for auxillary springs, intermediate wires, and finishing arch wires especially rectangular wires |
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Composite plastic arch wires
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- Possible to produce fibers with better strength and springiness than non-superelastic wires
- Pultrusion allows fabrication of round and rectangular wires - Possible ligature adapted around a wire and bracket to reduce friction - Tooth colored for esthetics - Shape difficult to change once manufacturing is complete |
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Hooke's Law and Ratios
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- Hooke's law defines elastic behavior of materials except SuperElastic A-NiTi
- Ratios are functions of both physica properties and geometric factors - Bending describes round wires completely but rectangular wires have torsional stresses - Ratios do not apply to linear portion of load-deflection curve and don't reflect wires stressed beyond their elastic limit |
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Effects of Diameter or Cross-Section
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Beam size increase
- Strength increases cubic - Springiness decreased fourth power - Range decreases proportionately Rectangular wires torsional, shear stress rather than bending stress is encountered Upper and lower limits of beam diameter related to strength establish wire sizes useful in orthodontics |
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Effects of Length
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When Cantilever beam length increases
- Strength decreases proportionally - Springiness increases cubic - Range increases squared - Springiness and Range are affected by length but torsional strength is not |
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Controlling ortho force by varying materials and size-shape
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Adequate strength
- Wire size must not deform permanently in use - Relatively large wire can be given desired spring qualities by increasing length - Length by doubling wire on itself or wind a helix Combination of two or more strands of small and springy wire - Multi-stranded wire depends on both the characteristics of individual wires and how tightly they been woven together Can carry out ortho treatment with series of wires of appx the same size. - NiTi, to TMA, to Steel. |
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Center of resistance
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- Object in free space: Same as center of mass
- Tooth root: Halfway between root apex and crest of alveolus |
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Moment
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Force acting at a distance when ling of action does not pass through center of resistance
- Causes translation and rotation of object |
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Couple
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Two forces equal and opposite in direction
- Results in pure moment since translatory effects cancels out - Couples will produce rotation and spin the object around its center of resistance |
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Center of Rotation
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Point around which rotation occurs when object is moved
- If a force and couple are applied, center of rotation can be controlled to any location - Application of force and a couple to crown is mechanism to get bodily movement of tooth or even greater movement of root than crown |
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How to decrease magnitude of force
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Apply it closer to center of resistance
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Anchorage and methods to control
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- Resistance to unwanted tooth movement
Methods to control 1) Reinforcement: - Extent to which anchorage should be reinforced depends on tooth movement desired - Typically involves as many teeth as possible in anchorage unit 2) Subdivision of desired movement - Pit resistance of a group of teeth against the movement of a single tooth 3) Tipping/Uprighting - Tip teeth and then upright them rather than bodily movement 4) Friction and Anchorage control strategies - Typical extraction situation in which to close extraction space 60% by retracting anterior teeth and 40% by forward movement of posterior teeth - Greater the strain on anchorage when brackets slide along an arch wire must be compensated by more conservative approaches to anchorage control |
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Factors related to successful therapy of midline diastema
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- Removal of causitive factor
- Whether the inherent tendency of periodontal or muscular tissues to regain their original shape can be overcome. Depends on balance of new tooth position and retention time - Fulfillment of all orthodontic treatment objectives including tooth position with optimal interdigitation and axial inclination |
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Types of appliances used to correct midline diastema
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Maxillary Hawley with Labial bow and Finger springs
- Crowns should only require a tipping movement to achieve space closure. Roots should be in proper axial position so teeth will be almost parallel or slightly distal to prevent space reopening - Need to control movement of each incisor independently - With a deep overbite, bite plane may be added to help open the bite before space closure - With excessive overjet, labial bow may be used for retraction and to prevent rotations or overlap of incisors Orthodontic bands or directly bonded attachments with Archwires and Elastics - Necessary to obtain bodily movement of crown and root to achieve proper axial inclination and post treatment stability - More than two teeth are involved to correct space problem - Rotational control is desired Free elastics around crowns of central incisors - Do NOT use this technique - Elastics can lodge in the gingival crevice without patient's knowledge and lead to eventual loss of tooth. Classic sign is extrusion of incisor without observable cause |
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Diastema retainer
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Removable
- Used where etiology has pathology - Removable Hawley with finger springs used in cases that does not require lengthy or permanent retention Fixed - Cemented orthodontic appliance, intra-coronal splinting or fixed bridgework - Used where etiology was abnormal labial frenum, heredity, severe rotations |
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Etiology of crossbite
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- Trauma with displacement
- Occlusal interferences - Periodontal conditions - Jaw shifts due to alterations in occlusion Habits - Poor eruption pattern(Ectopic) |
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Appliances to correct anterior and posterior crossbites in adult dentition
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Anterior sectional arch: Banding molars and bonding anterior four incisors. Mix of facial tipping and lingual root torque to bring maxillary incisors out of crossbite
Posterior: Cross elastic to tip teeth in opposite directions to correct occlusion. Causes some extrusion - If 1 arch has correct axial incline use cross Palatal Bar appliance. Acts as a point of attachment/anchorage to reposition mandibular molars. Contraindications is poor OH and molars can't be banded |
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Questions to ask about crossbite
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How long
Any attempt in the past to fix and was it successful Did this occur after an accident, dental treatment, anything? |
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Banding advantage vs disadvantage
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Advantage
- When heavy forces used - Where B-L attachments are used. Decreases risk of swallowing - Teeth with short crowns - Teeth incompatible with bonding Disadvantage - Extra appt - Discomfort - Require intermediate cementing medium - Subgingival placement - Non-resin cements soluble - Band width 2-4mm if full banded arch - Unesthetic |
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Debonding instruments
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Scaler - Some resin left, scratches in enamel. Simplest and quickest way for unfilled and light filled. Can use green rubber wheen for heavily filled
Stone - Deep grooves in enamel with some scratches Sandpaper discs - Pretty effective with some facets Rubber wheel - Light pressure most effective with minimal tooth damage Carbide finishing bur - Faster results but more enamel loss. Can use stainless steel bur for less enamel loss |
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Mouth rinse
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0.2% NaF 0.09%F weekly
0.05% NaF daily - Using lower concentration daily showed 50% caries reduction vs 20% weekly use |
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Etiology of diastemas
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Developmental
- Missing teeth - Supernumerary teeth - Impacted teeth Habits - Thumb suck - Tongue thrust - Can stop with bluegrass appliance Anatomy - Frenum - Bone loss - Root blunting causing poor crown to root ratio |
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Treatment of developmental diastemas
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Class 1 - Flared maxillary anteriors
- Use Hawley to tip teeth distally Class 2 - Flared max anterior due to skeletal etiology. - Cannot tip maxillary teeth distally if its mandibular retrognathia - Better corrected with twin block appliance - Close diastema with braces Class 3 - Occlusion with diastema - Can't retract maxillary anterior teeth - Use class 3 interceptive device - Protraction headgear and rapid palatal expander |
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Using ortho to upright adult teeth and examples
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Removable
- Used if one tooth requiring less than 20deg of uprighting - Appliance must have maximum tissue and tooth contact on all teeth that are not to be moved - Acrylic appliance with recurved helical finger spring: Gives maximum control but requires most skill. Can get up to 4mm movement - Split saddle space retainer: Effective but less control - Slingshot: Least control Fixed - Tooth tipped up to 60deg from vertical: Band desired tooth and 3 teeth mesial to it - If two teeth: band most distal tooth and use buccal tube - Tips molars upright with distal root as fulcrum: Get distal extrusion of teeth - Takes a few months |
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Most common cause of relapse for a diastema
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Inter-incisive soft tissues and their fibers
- Can do a circumferential suprac-crestal fiberotomy |