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103 Cards in this Set
- Front
- Back
4 characteristics of force vectors |
-Magnitude -Line of action of force -Sense/direction -Point of force application |
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Centre of resistance (6) |
-Centre of mass/gravity of an object -Point at which if F is applied through, will cause translation -Usually about 1/2-1/3 from root to apex -Depends on root length and bone coverage -*Older--> further from the bracket (more difficult) -Type of both movement depends on perpendicular distance from line of action to C of R |
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Centre of rotation (5) |
-Any point about which an object rotates after F is applied to it -Can be diff locations on tooth -Depends on type of F, point of appl of F and resistance level -In translation, C of Rot at infinity -*Closer the tooth's movement is to translation, farther apart the C of Rot from the C of R (assumed to be at infinity) |
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Moment |
-Potential for rotation -Force x Distance (of the line perpendicular from the C of R to the line of action) |
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Couple (2) |
-2 Fs of equivalent magnitude w/ non-linear lines of action and opposite sense/direction
-If true, only produces pure rotation |
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Force to moment ratio (2) |
-Must produce a F at the bracket and counter moment to oppose the moment felt by the C of R (offsets issue that bracket isn't applied at the C of R) -Every tooth has ratio of how large the moment must be to ensure the C of R only feels a translation F thru itself, usually same distance btw C of R and location of slot on bracket |
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Types of tooth movement |
-Tipping (C of R at apex) -Torquing (C of R at incisal edge) -Translation (bodily movement) |
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Advantages of fixed appliances (3) |
-Wear compliance out of equation -*Pre-adjusted appliances; each tooth has built-in tip, torque and angulation -6 degrees of freedom (can customize point of application and drxn of Fs) |
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Why wire shape matters (4) |
-Changing torque requires filling bracket slot w/ rectangular (change location of apex) -Tipping w/ round wire (no apex location control) -Small space closure w/ round (tipping OK) -Large space close w/ rectangular (can't afford tip, want translation) |
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Auxilliaries |
Extend width of bracket for more correction (ex. rotation wedges, vertical slot brackets w/ rotation attachments) |
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Premise of pre-adjusted appliances (3) |
-Universality of tooth-type shapes and positions -Incorporation into appliance -Correction w/ unbent archwires |
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Edgewise appliance design features (3) |
-1st order bends (in-out), lab-ling/buc-ling & rotation corrections -2nd order bends (tip), m-d correction, make incisal edge parallel to the floor -3rd order bends (torque), torque correction, twist wire CCW |
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0.022 x 0.028 in slot adv (3) and disadv (1) |
Adv -incr wire selection -incr stability with thicker wires, orthognath surgery -desired 3rd order M/F ratios for improved torque correction Disadv: incr wire inventory |
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0.018 x 0.022 in slot adv (3) and disadv (1) |
(h x l) Adv -Decr wire inventory -Decr tx time -Incr wire flexibility Dsadv: 3rd order M/F ratios may not be produced |
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Roth vs. MBT (commonly use readjusted appliance prescriptions) |
Roth: values for overcorrection built-in for (a) settling of dentition after removal (b) no separate prescription for xo and non-xo (unlike Andrew's) -most popular -Same bracket design but diff values than Andrew's MBT: values based on tx philosophy of lighter ortho Fs -Thinner wires, lighter F's -More biological |
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Archwire cross-section classification (4) |
-Round -Square: when want torque & finishing -Rectangular: " -Bi-dimensional: rect in ant (bodily), round in post (x friction) |
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Archwire composition classification (5) |
-NiTi: do NOT use as phase 2 (flex gives poor control, bends not possible, higher friction, can't weld or solder) -Copper NiTi -SS: best retraction -TMA: best finishing -Fibre reinforced: white/tooth-coloured, don't have good understanding |
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Stress/strain curve |
-Ultimate tensile strength: max F the wire can deliver -NiTi wire: yield strength and UTS further apart than w/ SS -E= Young's modulus of elasticity -More vertical--> stiffer (i.e. SS>NiTi) |
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Range |
Distance wire will bend elastically before permanent deformation -Range = strength/stiffness |
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Resilience vs formability |
-R: A under stress/strain curve up to proportional limit -F: amnt of permanent bending a wire will tolerate until it fractures, area under between yield point and fracture point |
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As the CROSS-SECTION of a wire is altered...(3) ...ex. doubling the diameter |
-Range changes inversely proportional -Springiness changes as 4th power of func -Strength changes as a cubic function ... -Decrease range by factor of 2 -Decreased springiness by factor of 16 -Increased strength 8 times |
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As the LENGTH of the wire is altered...(3)...ex. doubling the length of a cantilever |
-Range affected as a square -Springiness as a cubic function -Strength inversely proportional ... -Strength reduced by 1/2 -Range incr 4 times -Springiness increases 8 times |
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SS wire (6) |
-V. rigid, good for closure, not for alignment -Rigidity improved w/: wire bending, loops, multistrand (20% stiffness and 2x range) -19:9 (Cr:Ni) -Adv: strength, low friction -Disadv: stiffness? -Uses: removable appls (springs, clasps, labial bow fixed apples); closing space, bodily movement |
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NiTi wire (1 adv, 1 disadv) |
-Adv: excellent springback and flex -Disadv: not rigid, high friction |
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Shape memory vs. superelasticity |
-Shape memory: undergoes deformation and returns to original shape w/ mech or therm stimulus -Superelasticity: mech or therm stress applied w/ no incr in strain -Clinically, initial arch wire would apply same F level irrespective of level of deflection -Need phase transformation for superelasticity |
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Thermoelasticity vs. pseudoelasticity |
-Thermoelasticity: temp-induced phase transformation -Pseudoelasticity: mechanically induced phase transformation |
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Stages of tx (3/4) |
1a) Alignment 1b) Levelling 2) Space closure and molar relationship 3) Finishing to achieve root paralleling and ideal torque |
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Alignment (3) |
-Low stiffness: low Fs on activation -High strength: prevent permanent deformation -Long working range: max activation |
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Levelling (2) |
-Bite opening -Torque control initiation |
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Space closure and molar relationship (5) |
-High stiffness, good control -Easily adjusted -Low friction -Can be welded or soldered -Cost effective |
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Finishing (3) |
-Beta-T: ideal stiffness, good bend, fill bracket slot completely -SS: too stiff -NiTi: not adjustable, poor torque |
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Dental aetiology of class I malocclusion (2) |
-Crowding: discrepancy btw size of jaws and size of teeth, commonest manifestation -Spacing |
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Types of crowding (3) |
-Mild: 1-4mm -Moderate: 5-9mm -Severe: >9mm ...assuming normal inclination |
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Occult/hidden crowding |
When space is needed to change inclination |
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Carey's vs. Howe's vs. Bolton's analysis |
C: tooth size and dental arch relationship in permanent H: tooth size and basal bone width relationship B: ration of tooth material in upper and lower arches |
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Considerations for crowding management (5) |
-Amnt of crowding (mm) -Inclination of teeth -Pt's overall maloccl and underlying skeletal relationship -Pt profile -Position, presence and px of other teeth |
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Tx options for minor crowding (3) |
-Proclination -D tipping of Ms -Interproximal reduction |
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Proclination of the lower incisors (2) |
(for mild crowding management) -Only if: sufficient perio support, soft tissues can tolerate it -Limit is 2mm (unstable and perio compromise if more) |
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Distal tipping of the molars (7) |
(for mild crowding management) -Headgear -Low to ave FMPA -12-14 hrs/d -~400g F -Can augment w/ daytime URA or fixed appliance -Not v. successful on lower arch -Lip bumper |
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Interproximal reduction (5) |
-Up to 1mm/contact pt in the B segments and 0.75/contact pt anteriorly -Rotary or handfiles -Triangular -Prevent lower anterior proclamation -Caution: sensitivity and root proximity |
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Moderate crowding management (5) |
-Xo or non-xo -Depends on hard and soft tissue characteristics -Need to plan incisor position based on soft tissue morphology -Stability and aesthetics -Decision v. impt in pt's @ extremes of incisor protrusion or retrusion |
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Severe crowding management (2) |
-Xo almost always -Little effect on lip position w/ xo |
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Extraction uses/benefits (4) |
-Relief of crowding w/out excessive expansion -Correct inclination -Correct buccal segment relationship -Preserve/improve facial harmony |
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XO's and lip position |
Lips move 2/3 the distance that teeth are retracted, lots of variation |
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Factors in the xo decision (9) |
-MHx -Tooth quality -Amnt of crowding -Site of crowding -Impacted/missing teeth -Occl features -Skeletal disharmonies -Anchorage requirements -Profile and soft tissue |
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XO's for class I malocclusions |
-U and L 1st PMs -U and L 2nd PMs Extracting symmetrically to preserve the class I molar relationship |
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Adv (3) and disadv (1) for 1st PM extraction |
Adv -Severe crowding localized to ant of arch -Preservation of M relationships -Reduced protrusive soft tissues Disadv: potential compromise of facial aesthetics |
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Adv (3) and disadv (1) of 2nd PM extraction |
Adv -Crowing less severe anteriorly -More post crowding -Maintain soft tissues Disadv: difficult to control anchorage i.e. if want to maintain M relationship |
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Retention for crowding management (4) |
-Full time wear of removable appliance -Maintain space closure -1st 12mo, taper to nighttime wear -Stop? |
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Spacing aetiologies (2) |
-Tooth size discrepancy (Bolton) -Congenital absence of teeth (3M, 2nd PM, ULI) |
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Tx options for spacing (3) |
-Redistribute space (ex. w/ composite build-ups) -Close space (canines amenable to disguise, have crowding, OJ increased) -Open space |
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Spacing tx option depends on...(3) |
-OJ -Bilat or unilat -Crowding |
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Retention of opening space management |
If growth not stopped, implant placement not possib, need retainer w/ pontic |
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Closing space w/ canine modifications (5) |
-Grinding tip/recontour -Resto build-up -Bracket position to extrude and lower gingival margin -Bleaching -Reducing width |
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Retention of closing space management |
Bonded retainer to maintain closure and removable to maintain arch form |
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Relationship btw ortho and growth modification (2) |
-Application of F to the teeth can be transmitted to other parts of dentofacial skeleton -Can alter pattern of growth, correcting skeletal discrepancies |
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Functional appliances (3) |
-Removable or fixed, alter Md posture -Soft tissue stretch alters m activity of craniofacial complex--> changes in dental and skeletal relationships -Allows full expression of genetic potential and encourages remodelling of glenoid fossa--> enhanced Md growth |
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Timing of tx w/ growth mod & func appl's (4) |
-Greater effect when undergoing or near pubertal growth spurt -Effect may be result of intrxn btw change of func due to appliance and release of growth hormone -Ideally at peak growth velocity -Favourable outcome as long as some residual growth |
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Scammond Growth Curves (4) |
-Rapid growth at birth -Stable phase -Rapid increase in pre-adolescent -Mx and Md growth similar to neural (Mx stops before, used to advantage esp w/ class II tx>class III) |
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Mx growth (7) |
-MX dev from intramembranous ossification (no cartilage precursors) -Growth by apposition at sutures and surface remodelling -Displaced down and fwd -Growth in response to soft tissue stretch -Transverse width est by 12yo -Lengh est by 14-5 in fem and 16-17 in m by add of bone to tuberosity -Vertical growth completed last |
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Md growth (6) |
-Result of apposition of new bone on posterior and ramus and resorption on ant -Growth at condyles in response to tissue stretch -Transverse dim est by 9yo -Length est by 16-17 in fem and 19 in m -Vert est by 17-18 in fem and early 20s for m -No scope for expansion in the Md once canines erupt (unlike Mx which is 2 parts that don't fuse til much later) |
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Predicting growth spurt (6) |
-Around 14yo in boys and 12yo in girls -Chronological age not a good predictor, individual variations -Pt can keep growth chart to keep track -Cervical vertebrae development: ideally stage 3, base more concave/rhomboidal & spacing is reduced -Is Pt as tall as parent? -Have they and when did they change shoe size/trouser length?; relationship btw growth of long bones and the Md |
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Early vs. late mixed dentition? (3) |
-Evidence: both can be successful -Starting tx earlier means longer, needs cooperation, long lag phase btw functional comprehensive tx and fixed appl's -Maybe compelling reasons to start tx early |
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Success rate (3) |
-80% -Failure usually w/ compliance -*Motivation |
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Functional appliance changes...(3) |
-Skeletal -Dentoalveolar -Soft tissue |
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Skeletal changes w/ func appl's (5) |
-Condylar growth: 1-3mm -Fossa displacement, growth and adaptation: 3-5mm (mostly vertical) -Inr LAFH -Withhold down and fwd growth of Mx: 1-1.5mm ...modest |
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Dentoalveolar changes w/ func appl's (5) |
-Palatal tipping of upper incisors -Proclin of lower incisors -Differential eruption of lower post teeth (b/c md postured fwd) -Eruption guidance (changes to func occl plane) -Approx 70% correction ...a lot |
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Soft tissue changes w/ func appl's |
Changes to AP position of upper and lower jaw can result in improvements to soft tissue balance |
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Indications for functional appl's (9) |
-Growing -Class II div 1 and 2 maloccl -Mild to mod skeletal discrep (ANB<9) -Normal or reduced vertical proportions -Retrognathic facial type -Convex profile -Well-aligned arches -Minimal dental compensation -Cooperative |
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Contraindications for functional appliances (7) |
-Non-growing -Unfavourable growth pattern -Severe skeletal discrep (ANB>9) -Incr vertical proportions -Dental compensation -Non-compliant -Crowding |
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Fxn'l appl vs. xo + fixed appl (2) |
-No difference -Soft tissue changes occur in fxn'l that may not in xo and fixed |
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Retentive cmpnts in func appl (4) |
-Adams clasps -Circumferential " -Southend " -Ball-ended " |
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Active cmpnts in func appl (5) |
Induce the changes -Biteplanes--> differential eruption, non-eruption/intrusion, discussion, control VDO -Shields/screens: alteration in balance of tissues, remove P from lip for incisor proclin or remove p from cheeks to get transverse expansion -Expansion screws: prevent dev of x-bite when Md in postured position -Finger springs -Acrylic capping: minimizes proclin of lower incisors |
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Classification of func appl's (4) |
-Passive tooth borne -Active tooth borne (no longer) -Tissue borne -Hybrid |
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Passive tooth borne FA |
Soft tissue stretch and muscular activity produce tx effect -Removable: Bionator, Twin Block (most pop) -Fixed: Herbst (most skeletal effect of all) and MARA |
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Tissue borne FA (6) |
-Functional regulator -Doesn't contact teeth -Can use in primary dentition (II, expand apical base) -Mostly in vestibule -Buccal shields and lingual flange for soft tissue stretch -Hybrid useful in asymmetry |
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Postured bite in FA (4) |
KEY -All func appl's made with this -Displaces Md from habitat position -Md advanced for class II correction and incr in vertical dim beyond freeway space -Soft tissue stretch: causes F's to be directed to Md, Mx and dentition |
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Fabrication of FA's (3) |
-Alginate w/ excellent vestibular ext -Postured wax bite (in max protrusion or incrementally) -Depends on pt comfort |
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Design of the func appl (3) |
-Cmpnt approach -Based on presenting maloccl -Specific to pt needs |
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Fitting the func appl (2) |
-Before inserting, tell pt what to expect (incr saliva, difficulty speaking, "weird" feeling) -Motivate pt |
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Reviewing the func appl (6) |
-See pt approx 2 wks after delivering -Check retentive elements -Check sore spots -Evidence of wear (clean? dirty? fit?) -See every 6-8wks -Expect 1mm of change every 4wks -@ every list, record: OJ, OB, molar relationship, canine relationship, if there are lateral open bites (suspicious) |
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Envelope of discrepancy (3) |
-Inner envelope: ortho alone (pretty ltd, no scope for changing tooth position) -Mid: ortho + growth mod -Outer: ortho + surg (5% pt's) |
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Good camouflage results (4) |
-Normal soft tissue morpho -Normal/slightly reduced vert proportions -No/mild transverse prob's -Mild to mod skeletal disharmony |
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Poor camouflage results (4) |
-Signif facial asymm -*Exaggerated soft tissue morpho (determining factor) -Mod to severe vertical discrepancies -Mod to severe AP discrepancies (-3 < ANB < 9) |
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Indications for surgery (4) |
-Growth mod not an option -Soft tissues do not permit camouflage -Psycho-social considerations -Skele discrepancy beyond realm of ortho camouflage (antero-post, vertical, transverse) |
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Features of antero-post discrepancy class II (6) |
-Convex
-Retrusive chin -Mentalis m strain -Normal to obtuse naso-labial angle -ANB > 9 -Dental compensation |
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Features of antero-post discrepancy class III (7) |
-Concave -Hypoplastic midface -Prognathic md -Combo -Retrusive upper lip -ANB > -1 -Dental compensation |
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Features of increased vertical dimension (6) |
-Incr/steep FMPA -Incr LAFH -Vert Mx excess -Long face syndrome -Excessive gingival display -Normal upper lip length |
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Features of reduced vertical dimension (5) |
-Short face syndrome -Edentulous appearance -Reduced LAFH -Deep LM fold -Reduced/flat FMPA (can only open a bit by ortho) |
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Transverse discrepancies (5) |
-Facial asymm -Maybe underlying syndrome (ex. Treacher Collins, heme-facial macrosomia, trauma) -Canted occl plane -Crossbite extends to second molars -Exaggerated curve of Wilson (M's tipped B) |
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Md surgery, bilateral sagittal split osteotomy (BSSO) (4) |
-Intrao-oral cuts (advantage) -Versatile, posit to setback and adv Md -Good healing (good contact btw medullary bone btw segments) -Can correct class II, III (need some bone filling b/c won't match up afterwards) and with genioplasty (chin moved) for II (also, cuts below condyle level can keep condyle relation in glenoid fossa, maybe some parasthesia post-op) |
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Mx surgery, Le Fort osteotomy (5) |
-Mx advancement (ie. for class III) -Impaction (straight/differential) -Mx setback (for vert Mx excess (VME)) -Segmental -Surgically assisted rapid Mx expansion (RME) (cut thru Mx suture in adults, in kids it can be opened at the site itself) |
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Bimaxillary surgery (3)
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-Pt's w/ problems in both jaws -Surgical movements too great to do in one jaw -Improve stability (may not be stable to do movements all in one jaw) |
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Hierarchy of stability |
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Stages of management (5) |
-Planning -Pre-surg ortho (6-12mo) -Final surg planning (new pan, cep, face bow transfer, bite reg) -Orthognathic surgery -Postsurg ortho and retention |
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OG surg planning (3) |
-Timing: post-pubertal, esp class III w/ Md prognath and AOB (anterior open bite?), class II w/ deficient Md (earlier, further growth can help), serial lateral ceps to see if growth done -Photos, Pan, lateral ceph, PA ceph -Prediction tracing |
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Pre-Surg ortho purpose (3) |
-Decompensate teeth (primary objective of pre-surg ortho) -Arch coordination -Arch levelling -Centreline correction -Root positioning to allow for surgical cuts -XO of 3rd Ms 6mo before surg |
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Decompensation (5) |
-Normalize incline of ant segment -May req xo's -*Xo pattern is opposite to pattern for ortho camouflage (camouflage: class II--> xo U4s and L5s, class III--> xo L4s) -Elastics -Max's surgical correction |
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Final surgical planning (4) |
-New Pan to assess root positions (incision line) -New ceph to assess incline of teeth -New models to assess arch coordination -Facebow transfer for model surg (doing "surgery" on the model) and fabrication of surgical splints (splint for each stage, key for orienting) |
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Occlusal splint (4) |
-Made from casts on which model surgery was done -Splint defines surgical result -As thin as possib (<=2mm) -3-4 wks after surg |
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Stabilizing arch wires (2) |
-Once pre-surg goals met, full size SS arch wires placed before surgery (make sure they're completely passive) -Surgical hooks on arch wire (if need inter maxillary fixation) |
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Post-op issues (8)
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-Pain -Bleeding -Swelling -Infection -Perm or temp paresthesia -Poor blood supply to osteotomy sites -TMJ prob's -Post-surg relapse |
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Post-Surg phase (5) |
-Splint and stabilizing arch wires removed 2-4 wks post -Light wires placed, rectangular NiTi in upper and round steel in lower -Light elastics to settle occl, worn full time (even eating) -Try less than 6mo -Retention |