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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

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

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)

Moment

-Potential for rotation


-Force x Distance (of the line perpendicular from the C of R to the line of action)

Couple (2)

-2 Fs of equivalent magnitude w/ non-linear lines of action and opposite sense/direction

-If true, only produces pure rotation


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

Types of tooth movement

-Tipping (C of R at apex)


-Torquing (C of R at incisal edge)


-Translation (bodily movement)

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)

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)

Auxilliaries

Extend width of bracket for more correction (ex. rotation wedges, vertical slot brackets w/ rotation attachments)

Premise of pre-adjusted appliances (3)

-Universality of tooth-type shapes and positions


-Incorporation into appliance


-Correction w/ unbent archwires

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

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

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

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

Archwire cross-section classification (4)

-Round


-Square: when want torque & finishing


-Rectangular: "


-Bi-dimensional: rect in ant (bodily), round in post (x friction)

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

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)

-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)

Range

Distance wire will bend elastically before permanent deformation


-Range = strength/stiffness

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 

-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

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

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

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

NiTi wire (1 adv, 1 disadv)

-Adv: excellent springback and flex


-Disadv: not rigid, high friction





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

Thermoelasticity vs. pseudoelasticity

-Thermoelasticity: temp-induced phase transformation


-Pseudoelasticity: mechanically induced phase transformation

Stages of tx (3/4)

1a) Alignment


1b) Levelling


2) Space closure and molar relationship


3) Finishing to achieve root paralleling and ideal torque

Alignment (3)

-Low stiffness: low Fs on activation


-High strength: prevent permanent deformation


-Long working range: max activation

Levelling (2)

-Bite opening


-Torque control initiation

Space closure and molar relationship (5)

-High stiffness, good control


-Easily adjusted


-Low friction


-Can be welded or soldered


-Cost effective

Finishing (3)

-Beta-T: ideal stiffness, good bend, fill bracket slot completely


-SS: too stiff


-NiTi: not adjustable, poor torque

Dental aetiology of class I malocclusion (2)

-Crowding: discrepancy btw size of jaws and size of teeth, commonest manifestation


-Spacing

Types of crowding (3)

-Mild: 1-4mm


-Moderate: 5-9mm


-Severe: >9mm


...assuming normal inclination

Occult/hidden crowding

When space is needed to change inclination

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

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

Tx options for minor crowding (3)


-Proclination


-D tipping of Ms


-Interproximal reduction

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)

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

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

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

Severe crowding management (2)

-Xo almost always


-Little effect on lip position w/ xo

Extraction uses/benefits (4)

-Relief of crowding w/out excessive expansion


-Correct inclination


-Correct buccal segment relationship


-Preserve/improve facial harmony

XO's and lip position

Lips move 2/3 the distance that teeth are retracted, lots of variation

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

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

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

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

Retention for crowding management (4)

-Full time wear of removable appliance


-Maintain space closure


-1st 12mo, taper to nighttime wear


-Stop?

Spacing aetiologies (2)


-Tooth size discrepancy (Bolton)


-Congenital absence of teeth (3M, 2nd PM, ULI)

Tx options for spacing (3)

-Redistribute space (ex. w/ composite build-ups)


-Close space (canines amenable to disguise, have crowding, OJ increased)


-Open space

Spacing tx option depends on...(3)

-OJ


-Bilat or unilat


-Crowding

Retention of opening space management

If growth not stopped, implant placement not possib, need retainer w/ pontic

Closing space w/ canine modifications (5)

-Grinding tip/recontour


-Resto build-up


-Bracket position to extrude and lower gingival margin


-Bleaching


-Reducing width

Retention of closing space management

Bonded retainer to maintain closure and removable to maintain arch form

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

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

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

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)

-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)

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

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)

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

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

Success rate (3)

-80%


-Failure usually w/ compliance


-*Motivation

Functional appliance changes...(3)

-Skeletal


-Dentoalveolar


-Soft tissue

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

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

Soft tissue changes w/ func appl's

Changes to AP position of upper and lower jaw can result in improvements to soft tissue balance

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

Contraindications for functional appliances (7)

-Non-growing


-Unfavourable growth pattern


-Severe skeletal discrep (ANB>9)


-Incr vertical proportions


-Dental compensation


-Non-compliant


-Crowding

Fxn'l appl vs. xo + fixed appl (2)

-No difference


-Soft tissue changes occur in fxn'l that may not in xo and fixed

Retentive cmpnts in func appl (4)

-Adams clasps


-Circumferential "


-Southend "


-Ball-ended "

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

Classification of func appl's (4)

-Passive tooth borne


-Active tooth borne (no longer)


-Tissue borne


-Hybrid

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

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

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

Fabrication of FA's (3)

-Alginate w/ excellent vestibular ext


-Postured wax bite (in max protrusion or incrementally)


-Depends on pt comfort

Design of the func appl (3)

-Cmpnt approach


-Based on presenting maloccl


-Specific to pt needs

Fitting the func appl (2)

-Before inserting, tell pt what to expect (incr saliva, difficulty speaking, "weird" feeling)


-Motivate pt

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)

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) 

-Inner envelope: ortho alone (pretty ltd, no scope for changing tooth position)


-Mid: ortho + growth mod


-Outer: ortho + surg (5% pt's)

Good camouflage results (4)

-Normal soft tissue morpho


-Normal/slightly reduced vert proportions


-No/mild transverse prob's


-Mild to mod skeletal disharmony



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)

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)

Features of antero-post discrepancy class II (6)

-Convex-Retrusive chin
-Mentalis m strain
-Normal to obtuse naso-labial angle
-ANB > 9
-Dental compensation
-Convex

-Retrusive chin


-Mentalis m strain


-Normal to obtuse naso-labial angle


-ANB > 9


-Dental compensation

Features of antero-post discrepancy class III (7)

-Concave 
-Hypoplastic midface
-Prognathic md
-Combo
-Retrusive upper lip
-ANB > -1
-Dental compensation

-Concave


-Hypoplastic midface


-Prognathic md


-Combo


-Retrusive upper lip


-ANB > -1


-Dental compensation

Features of increased vertical dimension (6)

-Incr/steep FMPA
-Incr LAFH
-Vert Mx excess
-Long face syndrome
-Excessive gingival display
-Normal upper lip length

-Incr/steep FMPA


-Incr LAFH


-Vert Mx excess


-Long face syndrome


-Excessive gingival display


-Normal upper lip length

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)

-Short face syndrome


-Edentulous appearance


-Reduced LAFH


-Deep LM fold


-Reduced/flat FMPA (can only open a bit by ortho)

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)

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 move...

-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)

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 kits it can be opened at the site itself) 

-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)

Bimaxillary surgery (3)

-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)

Hierarchy of stability



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

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

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

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

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)

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

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)

Post-op issues (8)

-Pain


-Bleeding


-Swelling


-Infection


-Perm or temp paresthesia


-Poor blood supply to osteotomy sites


-TMJ prob's


-Post-surg relapse

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