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BDS3 - CDS > Ortho > Flashcards

Ortho Flashcards

1
Q

what type of bone formation for maxilla and mandible

A

intramembranous ossification

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2
Q

what are the pre-existing cartilagenous skeletons of the face

A
  • primary cartilage- nasal capsule and meckels cartilage
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3
Q

base of skull formation vs vault

A
  • base of skull by endochondral ossification
  • vault by intramembrenous ossification
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4
Q

at birth what growth centres remain

A
  • between spehnoid and occipital bones
  • in the nasal septum
  • in mandible at birth condylar cartilage remains
  • symphaseal cartilage disappears shortly after birth
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5
Q

describe neo-natal face in comparison with adult skull

A
  • face is small compared to cranium
  • eyes are large
  • ears are low set
  • forehead upright and bulbous
  • nasal region vertically shallow and nasal floor close to inferior orbital rim
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6
Q

sites of facial growth

A
  • sutures
  • synchondroses
  • surface deposition
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7
Q

describe facial growth at sutures

A
  • sutures are specialised fibrous CT joints between intramembranous bone
  • osteogenic cells in centre of suture and peripheral of these cells provide new bone growth
  • growth occurs in response to growing structures separating the bone…development of brain etc
  • when facial growth complete sutures fuse and become inactive
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8
Q

describe facial growth at synchondroses

A
  • found in midline and are between ethmoid, spehnoid and occipital bones
  • cartilage based growth centre with growth occuring in both directions
  • bones either side of the synchondrosis are moved apart as growth takes place
  • new cartilage formed in centre of synchondrosis as cartilage at periphery transformed into bone
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9
Q

describe facial growth due to surface deposition

A
  • new bone deposited beneath periosteum and above cranial and facial bones
  • to maintain bone shape as they grow resorption is also taking place
  • known as remodelling
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10
Q

what is known as a drift

A

change in position of bone due to remodelling

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11
Q

desribe growth of cranial vault and ages of growth

A
  • expands in response to growing brain until 7 years
  • rate of growth greatest in first 3 years
  • growth occurs in 2 ways - at sutures and surface deposition
  • after neural growth forehead continues to grow to accomodate expanding air sinuses
  • when complete all sutures fuse
  • fontanelles close by 18 months
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12
Q

describe growth of cranial base and ages of growth

A
  • cranial base = frontal, ethmoid, spehenoid, temporal and occipital
  • growth occurs in 2 ways - endochondral ossification and surface remodelling
  • half growth completed by age 3
  • spehno-ethmoidal synchondrosis fuse age 7
  • spheno-occipital synchondrosis close around age 15 and fuse age 20
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13
Q

relevence of growth of cranial base in orthodontics

A
  • occurs between age 4 - 20
  • anterior cranial base relatively stable after 7 years so used as landmark for superimposition in cephalometric analysis
  • also used for angles to show maxilla and mandible relationship
  • small angle = more likely class III skeletal relationship
  • large angle = class II
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14
Q

describe direction of growth of maxilla and ages related to growth

A
  • grows downawards and forwards relative to the anterior cranial base
  • growth slows age 7
  • forward growth of maxillary complex creates space posteriorly for development of maxillary tuberosities and eruption of molar teeth
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15
Q

what comprises nasomaxillary complex

A
  • orbit
  • nasal cavity
  • upper jaw
  • zygomatic process
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16
Q

what type of growth occurs in nasomaxillary complex and where

A
  • sutural growth takes place at zygomatic and frontal bones and also at mid palatine suture (intramembrenous)
  • surface deposition eg deposition on lower border of hard palate and alveolar process + resoprtion of the floor of nasal cavity and floor of orbits
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17
Q

describe growth of the mandible
direction/type of growht/where it occurs

A
  • grows downwards and forwards
  • occurs at condylar cartilage
  • type of growth - surface remodelling
  • resoption mainly anteriorly and lingually
  • deposition poteriorly and laterally
  • results in increased heigh of ramus and increase in length of dental arch
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18
Q

differences in growth of maxilla and mandible

A
  • mandible increases in length by a substantial amount more - 20-26mm growth compared to 5-8mm growth in maxilla
  • maxilla growth slows age 7 compared to mandible growth accelerating during pubertal growth spurt
  • growth in mandible slows to adult level age 17 F age 19M vs age 12 maxilla
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19
Q

maxilla/mandible growth direction slowing and relative timings

A
  • growth in width slows first, then length and finally height
  • applies to both maxilla and mandible
  • for both jaws growth in width complete before pubertal spurt
  • growth in length slows around 15 F and 18 M
  • growth in height slows 18 F and 20s M
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20
Q

treatment utilising growth of mandible./maxilla will work best if

A
  • mandible - carried out during pubertal growth spurt
  • maxilla - early teenage years before circumaxillary sutures and palate have fused
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21
Q

impact of facial growth on orthodontic tx

A
  • growth can affect severity of malocclusion either improving or making it worse
  • growth can be utilised by orthodontics to facilitate tx
  • continued unfavourable growth patterns following orthodontics can result in relapse
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22
Q

orthodontic appliances used which utilise facial growth

A
  • functional appliances - reduce overjet
  • rapid maxillary expansion RME - widen palate
  • protraction headgear - treat class III early on
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23
Q

growth rotations and causes

A
  • due to an imbalance in the growth of the anterior and posterior face heights
  • forward rotation - when more growth posteriorly than anteriorly, short face, anticlockwise rotation
  • backwards rotation - when more growth anteriorly than posteriorly, long face, clockwise growth
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24
Q

indications for taking a lateral cephalogram

A
  • aid diagnosis of skeletal class or vertical discrepancy
  • treatment planning
  • progress monitoring
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25
Q

how to maintain reproducability of lateral cephalometry

A
  • frankfurt plane should be horizontal - high point of external auditory meatus with lower margin of orbit
  • teeth in retruded contact position
  • head kept steady by structure contacting soft tissues at the nasion and ear rods in external auditory meatus
  • set distance from cone and film
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26
Q

what to analyse on lateral cephalogram

A
  • relationship between jaws and cranial base
  • relationship between upper and lower jaw
  • position of teeth relative to the jaws
  • soft tissue profile
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27
Q

lateral ceph main reference landmarks

A
  • sella
  • nasion
  • a point - maximum concavity on anterior maxilla
  • b point - maximum concavity on anterior mandible
  • ANS and PNS - anterior/posterior nasal spine
  • pogonion - most anterior aspect of chin
  • menton
  • gonion
  • porion - part of frankfurt occlusal plane
  • orbitale
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28
Q

lateral cephalogram
what measures antero-posterior poisiton of maxillar and mandible relative to base of skull

A
  • SNA
  • SNB
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29
Q

lateral cephalogram
what measures position of mandible relative to maxilla

A
  • anteroposterior - ANB
  • vertical - MMPA or FMPA
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30
Q

lateral cephalogram
ANB angles and what that translates to

A
  • Class I 2-4 degrees
  • Class II mild 4-6
  • Class II severe > 8
  • Class III milld 0-2
  • Class III severe < -3
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31
Q

lateral cephalogram
what is RFA

A
  • ratio facial height
  • ratio of lower anterior face height to total face height
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32
Q

errors in cephalometry

A
  • radiographic projection errors - magnification or distortion
  • errors with measuring system
  • errors in landmark identification - quality of image etc
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33
Q

Reference lines

A
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34
Q
A
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35
Q
A
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36
Q

hard stainless steel wire made by

A
  • drawing the metal in a cold state through a series of dies of successively smaller diameter
  • called hard working - gives SS its spring properties
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37
Q

Bauschinger effect

A
  • if coil activated in same direction as previous bending - its elastic recovery is greater than if its deflected in the opposite direction
  • when coil bent in a wire- outer surface becomes more hard workened and has better spring properties than inner surface
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38
Q

fractures of stainless steel in orthodontics can occur when

A
  1. overworked - by excessive bending and straining at the same point creating extreme stresses at this area
  2. mechanical abrasion crushed or marked - wire damaged by burs or stones in finishing process or during fabrication of components
  3. fatigue - caused by repeated straining action eg continually strained to engage deep undercut with a adams clasp
  4. weld decay -intergranular corrosion by overheating SS causing chromium carbides to go to grain boundaries and oral fluids now have access to other metals resulting in GALVANIC ACTION which weakens area
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39
Q

type of stainless steel used in orthodontics

A
  • 18/8 austenitic stainless-steel alloy
  • allow cannot be heat hardened only hardened by cold working
  • corrosion resistent when cold worked
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40
Q

composition of orthodontic stainless steel

A
  • 72% iron - main consituent and when combined with carbon forms steel
  • 18% chromium
  • 8% nickel
  • 1.7% titanium
  • 0.3% carbon
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41
Q

function of chromium in orthodontic stainless steel

A
  • lowers content of carbon present
  • lowers the temperature at which martensite forms
  • chromium forms a passive oxide film over the surface of the metal that enables SS to be corrosion resistant
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42
Q

function of nickel in orthodontic SS

A
  • alongisde chromium assists in achieving austenitic strucutre at room temp - by lowering temp at which austenitic structure breaks down on cooling
  • improves corrosion resistence
  • increases strength
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43
Q

function of titatium in orthodontic SS

A
  • prevents precipitation of chromium carbides at grain boundaries when alloy heated
  • carbon combines with titanium in preference to the chromium
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44
Q

difference between austenite and martensite

A
  • austenite - perfect cube unit cell strucutre
  • martensite - cube structure distorted by interstitial carbon atoms - makes strucutre longer in one dimension and shorter in other two dimensions
  • distortions prevent atoms from sliding past one another in an organised fashion - causing increased hardness of material
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45
Q

what is I.O.T.N

A
  • index of orthodontic treatment need
  • attempts to rank malocclusion in terms of the significance of various occlusal traits
  • identifies individuals who would most benefit from orthodontic tx
  • two components - aesthetic component (AC) dental health component (DHC)
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46
Q

types of retainer

A
  • conventional removable retainers
  • thermoplastic retainers
  • bonded retainers
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47
Q

equiptment for adams clasp construction

A
  • study cast
  • 0.7mm hard stainless steel wire
  • no 64 pliers
  • wire cutters
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48
Q

adams clasp function

A
  • retentive component in orthodontic removable appliance
  • utilises mesial and distal undercuts of the buccal aspect of teeth
  • made to fit below undercuts to grip the teeth - resists displacement
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49
Q

advantages of the adams clasp

A
  • small, neat and unobstructive - takes up limited space in buccal sulcus/acrylic baseplate
  • can be used on almost any tooth - deciduous or permanent
  • highly retentive
  • bridge provides site for pt to remove appliance
  • springs or tubes can be soldered onto bridge of the clasp
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50
Q

acronym for ortho URA design

A
  • ARAB
  • Active component
  • Retentive
  • Anchorage
  • Baseplate
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51
Q

URA aim

A

description of what the appliance design is aiming to achieve

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52
Q

URA ARAB

A
  • A - the name of the component(s) that will be moving teeth with the application of FORCE
  • R - resistence to displacement forces
  • A - resistence to unwanted tooth movement
  • B - connects all the components together and provides anchorage & assists with retention
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53
Q

what is the active component used to retract canines URA

A
  • 13 + 23 ; palatal finger springs + guards
  • 0.5mm HSSW
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54
Q

retentive components of URA

A
  • 16 + 16 ; adams clasp ; 0.7mm HSSW
  • 11 + 21 ; southend clasp ; 0.7mm HSSW
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55
Q

URA anchorage and baseplate prescription

A
  • anchorage - moving only (insert number) teeth (tick)
  • baseplate - self-cure PMMA
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56
Q

remodellig of bone controlled by

A
  • periodontal ligaments or fibres
  • PDL is collection of fibres surrounding root which act as a buffer against shock
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57
Q

baseplate modification URA if reducing overbite

A
  • baseplate - self-cure PMMA
  • flat anterior bite plane(FABP) ; overjet (OB) + 3mm
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58
Q

type of tooth movement in removable orthodontics

A

tipping movement

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59
Q

removable orthodontics advantages

A
  • tipping of teeth
  • excellent anchorage
  • cheaper
  • shorter chairside time
  • OH easier to maintain
  • non-destructive to tooh surface
  • less specialist training required
  • easily adapted for overbite reduction
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60
Q

removable orthodontics disadvantages

A
  • less precise control of tooth movement
  • canbe easily removed by patient
  • generally only 1-2 teeth can be moved at one time
  • specialist technical staff required to construct
  • rotations very difficult to correct
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61
Q

adjustment of adams clasp

A
  • well constructed adams clasp should require little adjustment
  • occasionally adjustments may be required if clasp not correctly engaging tooth
  • always adjuist flyover BEFORE arrowheads
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62
Q

arrow heads for adams clasp checklist

A
  1. must engage mesial and distal undercuts - except when tooth rotated
  2. arrowheads are parallel
  3. arrowheads should be 45 degrees to toot surface
  4. must not touch adjacent teeth
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63
Q

checklist for bridge of adams clasp

A
  1. bridge must stand clear of tooth at approx 45degrees to crown
  2. should not protrude above occlusal surface
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64
Q

other important checklists for adams clasp
(not including bridge/arrowheads)

A
  1. flyover should fit closely over contact area - if no adjacent tooth should still cross above contact area
  2. clearance of 0.5-1mm between wire and tissue in the palate
  3. must be tags present at end of wire to supply additional mechanical retention within baseplate
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65
Q

why do we add OJ + 3mm to baseplate FABP

A
  • to decrease risk of lower anteriors getting stuck behind FABP
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66
Q

what happens to teeth when FABP added to URA

A
  • anterior incisors to not contct
  • lower incisors now contact with FABP
  • allows room for upper anteriors to eventually be retracted to decrease OJ and OB
  • created posterior open bite - and posterior teeth continue erupting to close and correct this
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67
Q

names of retentive components URA and type of wire

A
  • adams clasp ; 0.7mm HSSW (0.6mm on deciduous teeth)
  • southend clasp ; 0.7mm HSSW
  • labial bows ; 0.7mm HSSW
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68
Q

names of active components and type of wire
not buccally placed

A
  • finger springs + guard ; 0.5mm HSS
  • Z-spring (doubel cantilever) ; 0.5mm HSS
  • flapper spring ; 0.5mm HSS
  • T-spring ; 0.5mm HSS
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69
Q

names of active components and type of wire
buccally placed

A
  • buccal canine retractor ; 0.5mm HSS ; sheathed with 0.5mm internal diameter tubing
  • roberts retractor ; 0.5mm HSS ; sheathed with 0.5mm internal diameted tubing
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70
Q

type of wire for stops URA

A
  • 0.7mm HSS
  • flattened
  • pssive component
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71
Q

fitting a URA steps

A
  1. ensure pt details match details onappliance
  2. check appliance matches design
  3. inspect appliance for sharp edges/traumatic areas - run finger over all surfaces
  4. check integrity of wirework - damage or work-hardening
  5. insert appliance into pts mouth - look for areas of blanching/trauma
  6. check posterio retention
  7. check anterior retention
  8. activate appliance
  9. demonstrate to pt how to insert/remove - get pt to demonstrate
  10. book review in 4-6 weeks
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72
Q

what is used to retract buccally placed canines

A
  • 13 + 23 buccal canine retractors
  • 0.5mm HSSW + 0.5mm I.D tubing
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73
Q

URA pt information and instructions

A
  1. appliance will feel big and bulky - normal get used to quickly
  2. may cause initial excess salivation - pass in 24 hours
  3. may inpinge speech for short period of time - practice reading aloud
  4. may cause inital discomfort or ache
  5. to be worn 24/7 including meal times and sleep
  6. remove after every meal and clean with soft brush
  7. remove during contact sports and keep in protective container
  8. avoid hard/sticky foods -may damage - caution with hot foods or drinks
  9. missing appts/non-compliance will increase tx length
  10. provide emergency contact details in case any problems arise
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74
Q

what can be added to URA to fix anterior cross bite

A
  • posterior bite plane
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75
Q

how does posterio bite plane work

A
  • creates anterior open bite
  • allows room for upper anterior tooth to be in correct position - tooth wont get caught by lower anteriors
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76
Q
A
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77
Q
A
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78
Q

components of adams clasp

A
  • bridge
  • arrowhead
  • flyover
  • leg
  • tag
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79
Q

what is active component used to reduce a on 11, 21, 12, 22

A
  • 21, 22, 11, 12 roberts retractor ; 0.5mm HSSW ; 0.5mm ID tubing
  • 13 and 23 mesial stops ; 0.7mm (flattened) HSSW
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80
Q

what is URA used to expand the upper arch

A
  • midline palatal screws
  • ideally 4 adams clasps (on 6s and 4s) for retention
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81
Q
A
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82
Q
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83
Q
A
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84
Q

what is orthodontics

A
  • specialty of dentistry
  • concerned with growth and development of teeth, faces and jaws
  • diagnoses, prevention and correction of dental and facial irregularities
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85
Q

tx for skeletal discrepancies
growing pt

A
  • growth modification technique to promote or restrict growth of either jaw
  • functional appliances
  • headgear
  • reverse pull facemask and RME - pulling maxilla forward, benificial age 10-12
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86
Q

tx for skeletal discrepancies
adults who have completed growth

A
  • orthognathis surgery
  • single jaw or bimaxillary process
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87
Q

what can modify jaw growth

A
  • functional appliances
  • twin block
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88
Q

cleft team

A
  • orthodontist
  • cleft team
  • ENT
  • speech therapy
  • maxfax surgeon
  • plastic surgeon
  • dental practitioner
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89
Q

growth and development issues

A
  • crowding
  • spacing
  • increased overjet
  • reverse overjey
  • hypodontia
  • supernumeraries
  • delayed dental development
  • anterior openbite
  • deep bite
  • ectopic teeth
  • anterior/posterior crossbites
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90
Q

orthodontic aids to diagnoses

A
  • study models
  • radiographs - OPG, lateral cephalogram
  • photographs
  • sensibility tests
  • cone beam CT scan
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91
Q

aims of orthodontic tx

A
  • stable
  • functional
  • aesthetic occlusion
  • prior to restorative work
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92
Q

types of appliances

A
  • removable - tip teeth, maintain space
  • functionals - modify jaw growth
  • fixed - 3D control of tooth position
  • aligners (invisalign)
  • headgear
  • temporary anchorage devices
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93
Q

benefits of orthodontic tx

A
  • improve function
  • improve dental health - make teeth more easy to clean
  • reduce risk of trauma
  • improve aesthetics
  • to facilitate other dental tx - rearrange spaces in hypodontia cases prior to bridges or implants
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94
Q

risks of orthodontic tx

A
  • decalcification
  • relapse
  • root resorption
  • pain, discomfort
  • soft tissue trauma
  • loss of tooth vitality
  • inhale or swallow components
  • candidal infections
  • failure to complete tx
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95
Q
A
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96
Q

aeitiology of malocclusion
general aetiological factors

A
  • skeletal - size shape and relative position of upper and lower jaws
  • muscular - form and function of the muscles that surround the teeth
  • dentoalveolar - size of the teeth in relation to the size of the jaws
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97
Q

components of the facial skeleton

A
  • maxillary base
  • mandibular base
  • maxillary and mandibular alveolar processes
  • maxillary complex is attached to anterior cranial base
  • mandible articulates with posterior cranial base
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98
Q

aeitiology of skeletal variation

A
  • genetic and environmental factors
  • strong hereditary component - class III is hereditary
  • environmental factors: masticatory muscles, mouth breathing, head posture
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99
Q

aeitiology of malocclusion
three planes of space

A
  • antero-posterior
  • vertical
  • transverse
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100
Q

antero-posterior relationship
class I cephalometries

A
  • SNA relates maxilla to anterior cranial base avg value 81degrees +/- 3
  • SNB relates mandible to anterior cranial base avg value 78 +/- 3
  • ANB relates mandible to maxillar avg value 3 +/- 2
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101
Q

aeitiology of malocclusion
class II overview and SNA/B/ANB angles

A
  • mandible placed posteriorly relative to maxilla
  • mandible too small (most commonly), maxilla too large or a combination of both
  • mandible normally sized but placed too far back = obtuse cranial base angle
  • teeth erupt into class 2 occlusion
  • SNA usually average but may be increased (large maxilla)
  • SNB ususally decreased
  • ANB> 5degrees
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102
Q

aeitiology of malocclusion
class III overview and SNA/B/ANB values

A
  • mandible placed anteriorly relative to maxilla
  • maxillar too small (most common), mandible too large or combintion of both
  • normally sized jaws but mandible positioned too far forward = acute cranial base angle
  • teeth erupt in class III occlusion
  • SNA decreased in maxillar deficient
  • SNB often average but may be increased if mandible prognathic
  • ANV<1 degrees or negative
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103
Q

aeitiology of malocclusion
dento-alveolar compensation

A
  • dento-alveolar structures may disguise underlying skeletal discrepancy
  • forces from lips, cheeks and tongue tend to incline teeth towards a position of soft tissue balance
  • example in class III occlusion proclined upper incisors amd retroclined lower incisors
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104
Q

facial heigh average clinical values

A
  • average ratio of LAFH to TAFH = 55%
  • lower anterior facial height = base of nose to inferior aspect of chin (soft tissue menton)
  • upper anterior facial height = brow ridge (glabella) to base of nose
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105
Q

aeitiology of malocclusion
vertical jaw relationship summary

A
  • frankfurt plane and mandibular plane normally meet at external occipital protruberance
  • averae value of frankfurt-mandibular plane angle FMPA = 27 degrees +/- 4
  • also takes into consideration facial height and LAFH to TAFH average value = 55%
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106
Q

vertical jaw relationship
long facial type

A
  • LAFH:TAFH proportion >55%
  • FMPA>31degrees
  • steep incline in mandibular plane
  • backward mandibular growth rotation
  • anterior open bite tendency
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107
Q

vertical jaw relationship
short facial type

A
  • LAFH:TAFH proportion <55%
  • FMPA<23degrees
  • tendency to parallelism of jaws
  • forward mandibular growth rotation
  • deep overbite tendency
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108
Q

aetiology of malocclusion
transverse plane types

A
  • arch width discrepancies
  • mandibular displacement
  • facial asymmetries
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109
Q

aetiology of malocclusion
arch width discrepancies

A
  • disproportion of maxillary and mandibular dental arches
  • causes unilateral or bilateral buccal segment cross bites
  • often exaggerated by antero-posterior discrepancies
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110
Q

aetiology of malocclusion
mandibular displacement

A
  • occurs where inter-arch width discrepancy causes upper and lower posterior teeth to meet cusp to cusp
  • mandible forced to deviate to one side to achieve ICP
  • possible association with TMD
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111
Q

aetiology of malocclusion
facial asymmetries

A
  • dental cause - displacement of normal mandible due to unilateral cross bite
  • true mandibular asymmetry:
  • -hemi-mandibular hyperplasia/elongation
  • -condylar hyperplasia
  • whole face may be affected by mild expressions of hemi-facial microsomia
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112
Q

arch size discrepancies
dento-alveolar disproportion

A
  • discrepancy between size of teeth and jaws
  • crowding caused by: small jaws and normally sized teeth or large teeth (macrodontia)
  • spacing caused by: large jaws and normally sized teeth or small teeth (microdontia)
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113
Q

aetiology of malocclusion

A
  • skeletal
  • dental - missing teeth etc
  • soft tissue - lip trap
  • other - habits
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114
Q

local causes of malocclusion

A
  • variation in tooth number
  • variation in tooth size or form
  • abnormalities of tooth position
  • local abnormalities of sofit tissues
  • local pathology
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115
Q

aetiology of malocclusion
variation in tooth number

A
  1. supernumerary teeth
  2. hypodontia
  3. retained primary teeth
  4. early loss of primary teeth
  5. unscheduled loss of permanent teeth
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116
Q

aetiology of malocclusion
supernumerary teeth

A
  • a tooth or tooth like entity which is additional to normal series
  • most common anterior maxilla
  • males>females
  • four types
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117
Q

four types of supernumerary teeth

A
  1. conical
  2. tuberculate
  3. supplemental
  4. odontome
118
Q

aetiology of malocclusion
conical supernumerary

A
  • small, peg shaped
  • close to midline - mesiodens
  • may erupt and require XLA
  • usually 1 or 2 in number
  • tend not to prevent eruption but may displace adjacent teeth - by deflecting path of eruption
119
Q

aetiology of malocclusion
tuberculate supernumerary

A
  • tend not to erupt
  • normally paired
  • barrell shaped
  • usually extracted to allow incisors to erupt
  • one of the main causes of failure of eruption of permanent upper incisors
120
Q

aetiology of malocclusion
supplemental supernumerary

A
  • extra teeth of normal morphology
  • most often upper laterals or lower incisors
  • can be 3rd premolars or 4th molars
  • often extract - decision based on form and position
121
Q

aetiology of malocclusion
odontome supernumerary

A
  • compound: discrete denticles - tooth like objects in a mass
  • compled: disorganised mass of dentine, pulp and enamel
122
Q

most common explanation for retention of upper incisors

A
  • tuberculate supernumerary
  • or trauma to deciduous incisors
123
Q

aetiology of malocclusion
hypodontia

A
  • developmental absence of one or more teeth
  • females>males
  • 4-6% population excluding 8s
  • commonly upper laterals and then second premolars
  • strong genetic component - passes down in families
  • microdontia also associated
124
Q

management of hypodontia - absent successor

A
  • either maintain primary tooth as long as possible
  • or extract deciduous tooth early to encourage space closure in crowded cases
  • early orthodontic referral for advice
125
Q

infra occluded primary molars

A
  • appears submerged
  • process where tooth fails to achieve or maintain its occlusal relationship with adjacent teeth
  • temporary ankylosis
  • percussion sound
  • common 1-9%
126
Q

aetiology of malocclusion
retained primary teeth - alarm bells if

A
  • a disruption in the sequency of eruption
  • alarm bells if:
  • difference of over 6 months between shedding of contralateral teeth
  • usually want to investigate with radiograph
127
Q

causes of retained primary teeth

A
  1. absent successor
  2. ectopic successor or dilacerated
  3. infra-occluded (ankylosed) primary molars - tooth looks submerged
  4. dentally delayed in terms of development
  5. pathology/supernumerary
128
Q

early loss of primary teeth causes

A
  • trauma - incisors most commonly affected
  • periapical pathology
  • caries
  • resorption by successor
129
Q

importance of early loss of primary teeth

A
  • incisors - very little impact, no compensating or balancing X needed
  • canines - unilateral loss in crowded arch can give centre-line shift, some mesial drift of buccal segments, consider balancing X
  • molars - more space loss with Es>Ds, more space loss in upper>lower, 6s drift mesially and steall 5 space
130
Q

early loss of primary teeth
localisation of crowding depends on

A
  • which tooth is X
  • when tooth is X
  • pts inherent crowding
  • early loss of Es lead to 6s closing gap - now 5s impacted
131
Q

balancing/compensating extractions

A
  • balancing extraction is extraction of tooth from the opposite side of the same arch - designed to minimise midline shift
  • compensating extraction is extraction of tooth from the opposing arch of the same side - designed to maintain occlusal relationship
132
Q

factors that influence impact of loss of 6s

A
  1. age at loss
  2. crowding
  3. malocclusion
133
Q

age at loss of 6s

A
  • upper arch - less important
  • lower arch:
  • of 7s erupted - often poor space closure
  • if too early - distal drift of 5s - particularly if E lost at same time as 6
134
Q

crowding effect on unscheduled loss of permanent teeth

A
  • upper arch - potential for rapid space loss
  • lower arch:
  • spaced arch - will have spaces
  • aligned arch - will have spaces
  • crowded - best results likely
135
Q

unscheduled loss of central incisor

A
  • effect depends on timing of loss
  • early will result in drift of adjacent teeth
  • late will result in long-term space
  • ideally maintain space - implant or simple denture
  • plan difinitive prosthesis
  • if lateral incisor drifts to fill space - re-open space for prosthesis or build up lateral to diguise as central
136
Q

aetiology of malocclusion
macrodontia

A
  • tooth/teeth larger tan average
  • localised or generalised
  • can cause crowding, asymmetry
    can be shaved down - although limit to this
  • more commonly XLA and replaced by prosthesis
137
Q

aetiology of malocclusion
microdontia

A
  • tooth/teeth smaller than average
  • localised or generalised
  • leads to spacing
  • linked to hypodontia
138
Q

aetiology of malocclusion
ectopic teeth

A
  • can be any teeth but mostly third molars, upper canines, first molars, upper centrals
  • transpositions
139
Q

aetiology of malocclusion
ectopic maxillary canines

A
  • 1-3% population
  • 80% palatal
  • check for palpable buccal canine bulge from 9 years onwards
  • long path of eruption
  • higher incidence in absent/peg shaped U laterals, class II div 2 incisor relationship
  • buccal canines more associated with crowding
140
Q

ectopic canines clinical assessment

A
  • visualisation/palpation of any obvious bumps of 3
  • inclination of 2
  • mobility of c or 2
  • colour of c or 2
141
Q

aetiology of malocclusion
abnormal tooth form types

A
  1. peg shaped laterals
  2. dens in dente - communication into pulp chamber
  3. gemination/fused teeth
  4. talon cusps
  5. dilaceration
  6. accessory cusps and ridges
142
Q

ectopic canines management options

A
  1. X of c to encourage improvement in position of 3 (interceptive)
  2. retain 3 and observe - accept its position
  3. surgical exposure and orthodontic alignment
  4. surgical X
143
Q

ectopic first molars cause/sign/management

A
  • can get stuck distal behind E
  • more commonly upper arch
  • reversible before age 8
  • caries risk
  • sign of crowding, mesial path of eruption, abnormal morphology of E
  • management:
  • separator between E and 6
  • attempt to distalise 6
  • extract E/wait for E to exfloliate (most common)
144
Q

ectopic upper central incisors causes

A
  • supernumerary - tuberculate, odontome
  • trauma to primary predecessor:
  • ankylosis of primary tooth
  • displacement of tooth germ
  • dilaceration of root
145
Q

aetiology of malocclusion
transpositions

A
  • interchange in the position of 2 teeth
  • classification - true or pseudo
  • most commonly upper canines and first premolar / lower canines and incisors
  • tx options: accept, XLA, correct
146
Q

aetiology of malocclusion
local abnormalities of soft tissues

A
  • digit sucking - proclined UI, retroclined LI, anterior open bite, unilateral posterior crossbite (due to narrow maxillary arch) - may cause mandibular displacement
  • labial frenum - low frenum attachment (tends to migrate up with development) may cause median diastema
147
Q

aetiology of malocclusion
local pathology

A
  • caries
  • cysts
  • tumours
148
Q

orthodontic assessment
why

A
  • determine if any malocclusion is present
  • identify any underlying causes
  • decide if tx is indicated - either refere or devise tx plan
149
Q

orthodontic assessment
ideal occlusion andrews 6 keys

A
  1. molar relationship: distal surface of disto-buccal cusp on upper 6 occludes with medisl surface of lower 7
  2. crown angulation (mesio-distal tip)
  3. crown inclination
  4. no rotations
  5. no spaces
  6. flat occlusal planes
150
Q

orthodontic assessment
normal occlusion definition

A
  • more commonly observed than ideal occlusion
  • minor deviations that do not constitute and aesthetic or functional problem
151
Q

orthodontic assessment
PMH contra-indications

A
  • allergy to nickel or latex
  • epilepsy/drugs: some drugs cause gingival hyperplasia
  • imaging: cannot have MRI scan with braces
152
Q

orthodontic assessment
habits

A
  • thumb sucking
  • lower lip sucking
  • tongue thrust
  • chewing finger nails
153
Q

orthodontic assessment
extraoral overview

A
  • skeletal bases
  • soft tissues
  • TMJ
154
Q

orthodontic assessment
vertical skeletal assessment

A
  • look at frankfort-mandibular plane angle (FMPA)
  • typically 27 degrees
  • finger along lower border of mandible or mandibular plane
  • finger/ruler alone frankfort horizontal plane
155
Q

orthodontic assessment
soft tissues overview

A
  • soft tissues can influence tooth position
  • lips: competent/incompetent; lower lip level; lower lip activity
  • tongue: position; habitual and swallowing
  • habits: thumb/digit sucking
  • speech: lisping
156
Q

orthodontic assessment
tongue position and swallowing pattern affects

A
  • tongue thrust on swallowing can be associated with anterior open bite (AOB)
  • can either be endogenous or adaptive tongue thrust
  • may cause relapse of AOB at the end of tx if endogenous
157
Q

occlusal features of thumb habit

A
  • proclination of upper incisors
  • retroclination of lower incisors
  • localised anterior open bite or incomplete OB
  • narrow upper arch +/- unilateral posterior crossbite
  • effects will be superimposed on existing skeletal pattern and incisor relationship
158
Q

orthodontic assessment
competent/incompetent lip/lip trap

A
  • competent: lips that meet at rest; relaxed mentalis muscle
  • incompetent: lips that do not meet at rest; relaxed mentalis muscle
  • lip trap: teeth rest on lip; may procline upper incisors; may lead to relapse of overjet if persists at end of tx
159
Q

orthodontic assessment
TMJ

A
  • path of closure
  • range of movement
  • pain
  • click from joint
  • deviation on opening
  • muscle tenderness
  • mandibular displacement: discrepancy in retruded contact position and inter-cuspal positon - displacement from RCP to ICP
160
Q

orthodontic assessment
intra-oral examination check

A
  • oral hygiene and periodontal health
  • count the teeth
  • teeth of poor prognosis
  • assess crowding/rotations/spacing
  • palpate for canines if not erupted
  • note teeth of abnormal shape/size
161
Q

orthodontic assessment
assessment of lower arch

A
  • degree of crowding: uncrowded, mild, moderate, severe
  • presence of rotations
  • inclination of canines: mesial, upright, distal
  • angulation of incisors to mandibular plane: uplight, proclines, retroclined
162
Q

orthodontic assessment
assessment of upper arch

A
  • degree of crowding: uncrowded, mild, moderate, severe
  • presence of rotations
  • inclination of canines: mesial, upright, distal
  • angulation of incisors to frankfort plane: upright, proclined, retroclined
163
Q

orthodontic assessment
teeth in occlusion assessment

A
  • can assess in RCP or ICP
  • incisor relationship (BSI definitions)
  • overjet
  • overbite
  • molar relationship (angles classification)
  • canine relationship
  • cross bites
  • centre lines
164
Q

BSI incisor relationship

A
  • British Standards Institute classification
  • class I: the lower incisal edges occlude with or lie immediately below the cingulum of the upper incisors
  • class II div 1: lower incisal edge occludes behind the cingulum of the upper central incisors and the upper incisors are proclined
  • class II div 2: lower incisal edge occludes behind the cingulum of the upper central incisors, and the upper incisors are retroclined (the lateral incisors may be proclined)
  • class III: lower incisal edge occludes in front of the cingulum of the upper incisors
165
Q

angles classification

A
  • classifies molar relationship
  • class I: maxillary first molar is slightly posteriorly positioned relative to the mandibular first molar
  • class II: maxillary first molar is inline with or anteriorly positioned relative to the mandibular first molar
  • class III: maxillary first molar is severely posteriorly positioned relative to the mandibular first molar
166
Q

orthodontic assessment
special investigations

A
  • radiographs: OPT; maxillary anterior occlusal; lateral cephalogram
  • vitality tests
  • study models
  • photographs
167
Q

orthodontic assessment
what to put on referral level

A
  • name, age, sex of pt
  • HPC, RMH, RDH
  • incisor relationship, sk base (AP, V, T)
  • teeth present/absent, OH, poor prognosis teeth
  • lower arch assessment
  • upper arch assessment
  • Oj, OB, centrelines, molar relationship, crossbites
  • IOTN score
168
Q

ortho tx planning
general principles

A
  • history
  • examination
  • diff diagnoses: list of probables
  • special tests: study models, radiographs, photos
  • diagnosis: description/index of orthodontic tx need
  • tx plan
  • treatment: accept/appliances
  • outcome: PAR index
169
Q

ortho tx planning
diagnosis description

A
  • description of the malocclusion: eg class II div 1 incisor relationship
  • determine the causes of the malocclusion:
  • small teeth= spacing
  • early loss of deciduous teeth = crowding
  • digitsucking = proclination and increased OJ
  • are the causes skeletal or dento-alveolar
170
Q

2 types of cephalometry

A
  • lateral cephalometry
  • PA cephalometry: shows transverse skeletal malocclusions; rare problems
171
Q

why is correct orthodontic diagnosis important

A
  • orthodontic appliances move teeth very well but only minimally can modify skeletal relationship
  • a severe skeletal discrepancy may require surgical intervention
  • careful planning essential to ensure we dont make mistakes
  • for example if anterior crossbite is dental= orthodontics
  • if anterior crossbite is skeletal = orthognathic surgery
172
Q

objectives or orthodontic tx

A
  • to produce an occlusion which is:
  • stable
  • functional
  • aesthetics
  • and potentially to facilitate other forms of dentistry (crowns, bridges etc)
173
Q

ortho tx planning
factors affecting tx plan

A
  • future growth changes
  • aetiology of malocclusion: try fix aetiology first
  • patients soft tissue profile
  • retention and stability
  • patients wishes
  • access to tx
  • compliance
  • space requirements
  • aims of tx
  • prognosis of individual teeth
174
Q

ortho tx planning
different aims of tx

A
  • full correction of malocclusion: class I incisor, canine and molar relationship, no rotations, spaces, flat occlusal plane (adrews 6 keys)
  • compromise treatment: correct certain aspects accepting others, may have to work within adverse skeletal pattern etc
175
Q

ortho tx planning
stages of tx planning

A
  1. plan around the lower arch - angulation of LLS (lower labial segment) is stable
  2. decide on tx in lower
  3. build upper arch around lower - aim for class I incisor and canine relationship
  4. decide on molar relationship - class I or full unit class II molar relationship, dont want class III
176
Q

ortho tx planning
types of crowding assessment

A
  • two ways of assessing crowding:
  • measure space available and space required
  • overlap technique
177
Q

ortho tx planning
types of crowding assessment

A
  • two ways of assessing crowding:
  • measure space available and space required
  • overlap technique
178
Q

crowding assessment
method 1: measuring space available and space required

A
  • A+B+C+D = arch length (space available)
  • mesial of 6 to distal of 2 + distal of 2 to midline (on both sides)
  • measure widthe of each individual tooth from 5-5 and add together = space required
  • subtract from one another = degree of crowding
179
Q

crowding assessment
method 2: overlap technique

A
  • measure how much teeth overlap
  • add them all together to get degree of crowding
180
Q

ortho tx planning
space required in lower arch general principles

A
  • mild (0-4mm):
  • 1-2mm : non X/stripping (metal sandpaper between teeth to take away some enamel)
  • moderate (4-8mm):
  • extract 5s if lower half
  • extract 4s if closer to 8mm
  • severe (8+mm): extract 4s
  • if lower arch extraction: extract in upper arch too
  • if lower arch extraction not required but upper spacing required either extract upper arch (MR class II) or distalise UBS (MR class I)
181
Q

ortho tx planning
if ALL soace from extractions will need to be used

A
  • need to reinforce anchorage
  • headgear use, transpalatal arch or temporary anchorage device (TAD)
  • to stop pts teeth moving forward
182
Q

ortho tx planning
retention phase

A

retainers needed to hold teeth in place after active movement

183
Q

ortho tx planning
tx options (BDS4 common q)

A
  1. accept malocclusions
  2. extractions only: for class I crowding cases
  3. URA
  4. functional appliances
  5. fixed appliances
  6. complex tx involving orthodontics and restorative tx or orthodontics and orthognathic surgery
184
Q

ortho tx planning
limitations of orthodontic tx

A
  • effects of tx almost purely dento-alveolar and tooth movement - little effect on skletal pattern
  • tooth movements limited by shape and size of alveolar process
  • teeth will only remain stable in position where there is equilibrium between forces of: soft tissues, occlusion and periodontal structures
185
Q

ortho tx planning
who will do tx

A
  • simple tx may be carried out by GDP: straighforward and can be managed by URA
  • complex tx: requires skill of a specialist practitioner or hospital specialist
186
Q

URA active component to reduce OJ for 21, 22, 11, 12 and reduce OB

A
  • 22, 21, 11, 12; roberts retractor; 0.5mm HSSW + 0.5mm I.D tubing
  • stops : 13 + 23; mesial stops; 0.7mm flattened HSSW
187
Q

ortho lab stuff to know

A
  • 10 uses of ortho study casts
  • stainless steel elements and %
  • names of 3 types of pliers
  • advantages and disadvantages of URA
  • URA appliance design
  • retentive components name and thickness
  • sctive components name and thickness
  • adams clasp components
  • finger spring adjustment (uncoil)
188
Q

facial growth importance for orthodontics

A
  • predict changes
  • utilise growth to correct malocclusion
  • time orthodontics and surgery
  • understand development of facial anomelies
  • measure changes in growth and tx using cephalometry
189
Q

life in utero two phases

A
  1. embryonic 1-8 weeks
  2. foetal 8 weeks to term
  • all limbs and organs and face have formed within first 2 months - embryo has characteristic human form
  • environmental influences can cause cranio-facial abnormalities very early on in pregnancy
  • miscarriage incidence greatest during embryonic period
190
Q

neural crest cell migration

A
  • important in the development of the face
  • neural tube develops brain and spinal cord
  • begins to fuse at 4 weeks
  • spini bifida - if it doesnt fuse (will never fuse)
191
Q

what forms neural tube and development disorders at this stage

A
  • neural folds fuse to form neural tube at week 4
  • failure to fuse leads to spina bifida
  • neural tube develops into brain and spinal cord - failure to develop leads to anencephaly: serious birth defect in which a baby is born without parts of the brain and skull. It is a type of neural tube defect
192
Q

neural crest cell development

A
  • cells from ectoderm developed from folding of the neural plate
  • undergo migration within embryo and differentiate into many cell types: spinal ganglia, schwann cells, meninges of brain etc
  • ectomesenchyme derived from neural crest cells: bone and CT, dental tissues (pulp, dentine, dementum and PDL)
193
Q

describe early development of the face

A
  • occurs during first 8 weeks after fertilisation
  • most of face formed from migrating neural crest cells: either in fronto-nasal process or brancial arches
  • interference with migration can lead to severe facial deformities
  • environmental factors may lead to significant malformations during this early period
194
Q

defects of the face (particularly in midline) may be closely related to

A

defects of the anterior parts of the brain

195
Q

cleft formation

A
  • failure of fusion between various facial processes or between the palatine processes may lead to cleft formation
  • upper lip and anterior part of palate have different embryological origins from posterior palate - and they fuse at different times
  • cleft lip and alveolas can occur independently of cleft palate etc
  • cleft lip extends to incisive foramen
  • cleft palate from incisive foramen back
196
Q

when does extension and fusion of the facial processes occur

197
Q

foetal stage

A

8 weeks to term

198
Q

skull division

A
  • neurocranium: forms a protective case around the brain
  • viscerocranium: forms skeleton of the face
  • neurocranium can be devided into flat bones of the vault (intramembrenous ossification) and the endochondral elements of the base of the skull
199
Q

describe intramembrenous bone formation

A
  • flat bones
  • bone is deposited directly into primitive mesenchymal tissue
  • intramembrenous bones include vault of skull, maxilla and most of the mandible
  • needle like bone spicules form which radiate from primary ossification centres to the periphery
  • progressive bone formation results in the fusion of adjacent bony centres
200
Q

describe endochondral bone formation

A
  • long bones
  • bones are preceded by hyaline cartilage model - BV invade cartilage and then replace with bone
  • forms base of skull
  • several centres of ossification which eventuall fuse
201
Q

base of skull formation

A
  • series of cartilages forms base of skull
  • undergo endochondrial ossification from multiple centres
  • starting at basi-occiput at 10-12 weeks
  • at birth cartilagenous growth centres remain between sphenoid and occipital bones and in nasal septum
202
Q

vault of skull formation

A
  • intramembrenous ossification of vault commences at 12 weeks at several centres
  • fusion is incomplete at birth - widenings known as fontanelles - allow flexibility in the skull during birth
203
Q

fontanelle closure

A
  • anterior fontanelles closes about 2 years of age
  • posterior at about 1 year
204
Q

describe growth of vault

A
  • growth occurs at bibrous sutures in response to intracranial pressure
  • growth of skull continues until around 7 years old
  • some of the sutures remain open until adulthood
205
Q

embryonic facial cartilages

A
  • meckels cartilage
  • auditory capsule
  • cranial base
  • nasal capsule
  • sphenoid
206
Q

maxilla and mandible formation

A
  • form intramembranously
  • but develop adjacent to pre-existing cartilagenous skeletons:
  • nasal capsule and meckels cartilage (6 weeks)
207
Q

describe development of mandible

A
  • mandible develops at several units
  • all responding to different growth stimulae
  • condylar unit
  • angular unit
  • coronoid unit
  • alveolar unit
  • body of mandible forms in response to the inferior dental nerve
208
Q

mandible development units and growth stimulae

A
  • condylar unit - secondary cartilage formation - if condylar cartilage doesnt develop there is no condyle
  • angular unit forms in response to lateral pterygoid and masseter muscles
  • coronoid unit responds to temporalis muscle development
  • alveolar unit only forms if teeth are developing
  • body of mandible forms in response to inferior dental nerve
209
Q

three main sites of secondary cartilage formation in mandible and when the cartilage appears/disappears

A
  1. condylar cartilage
  2. coronoid cartilage
  3. symphyseal end of bony mandible
  • appears between 12 and 14 weeks I.U.L
  • coronoid cartilage disappears long before birth
  • symphyseal just after birth
  • growth continues at condylar cartilage until about 20 years of age
  • at birth mandible in two halves - midline symphysis fuses a few months after
210
Q

summary of prenatal face/skull growth

A
  • ossification of face and skull commences at about 7-8 weeks
  • vauls of skull formed intramembranously
  • base of skull by endochondral ossification
  • both maxilla and mandible develop intramembranously but are preceeded by a cartilagneous facial skeleton
  • meckels cartilage preedes the mandible and nasal capsule is the primary skeleton of the upper face
211
Q

primary abnormality definition

A
  • defect in structure of an organ./part of an organ
  • that can be traced back to an anomaly in its development
  • spina bifida
  • cleft lip
  • coronary heart disease
212
Q

secondary abnormality definition

A
  • interruption of the normal development of an organ
  • can be traced back to other influences
  • teratogenic agents (agent causing abnormality due to foetal exposure) - infection, chemical (thalidomide, lithium)
  • trauma: amniotic bands
213
Q

deformation and agenesia definitions

A
  • deformation: anomelies that occur due to outer mechanical effects on existing structures
  • agenesia: absence of an organ due to failed development during embryonic period
214
Q

sequence and syndrome definition

A
  • sequence: single factor results in numerous secondary effects (pierre-robin)
  • example of sequence: small mandible and cleft palate often happens in sequence
  • syndrome: group of anomelies that can be traced to a common origin (trisomy 21 in downs syndrome)
215
Q

facial syndromes causing maxillay hypoplasia

A
  • aperts syndrome
  • crouzons syndrome
  • downs syndrom
  • foetal alcohol syndrom
  • achondroplasia
  • cleft lip/palate
216
Q

facial syndromes causing mandibular problems

A
  • treacher collins syndrom
  • pierre-robin
  • sticklers syndrome
  • turners syndrome
  • hemifacial microsomia
217
Q

facial syndromes arising from early problems with facial development

A
  • 1-8 weeks
  • environmental - foetal alcohol syndrome
  • genetic
  • multifactorial: hemifacial microsomia, treachers collins, cleft lip and palate
218
Q

foetal alcohol syndrome cause/occurs on

A
  • cause is high maternal intake of alcohol
  • occurs on day 17 - mums may be unaware of pregnancy
  • eyelids short
  • small head
  • small jaw
  • low nasal bridge
  • short nose
  • flat midface
  • indistinct philtrum
219
Q

foetal alcohol syndrome features

A
  • microcephaly - small head
  • short palpebral fissure
  • short nose
  • long upper lip with deficient philtrum
  • small midface
  • small mandible
  • midl mental/learning difficulty
220
Q

hemifacial microsomia cause/features

A
  • multifactorial cause
  • fewer neural crest cells on one side
  • progressive facial asymmetry - as one side growth the other wont
  • unilateral mandibular and zygomatic arch hypoplasia
  • high arched palate
  • malformed pinna
  • normal intellect, deafness, cardiac and renal problems
  • happens at 4 weeks old when neural crest cells migrating
221
Q

treacher collins cause/features

A
  • mandibulofacial dysostosis
  • deformity of 1st and 2nd branchial arches (day 19-28)
  • slant palpebral fissure - eyes slant downwards
  • dip of lower lid outer third
  • hypoplastic or missing zygomatic arches
  • hypoplastic mandible
  • deformed pinna - conductive deafness
222
Q

cleft lip and palate epidemiology

A
  • 1:700 live births
  • 70% sporadic - no FH
  • cleft lip and palate/cleft lip males>females
  • cleft palate demales > males
223
Q

when do lips/palat fuse

A
  • lips: day 28-38 (4-5 weeks)
  • palate: day 42-55 (6-8 weeks)
224
Q

aetiology of cleft lip and/or palate
genetic

A
  • monozygotic twins
  • syndromes
  • familial fattern
  • 66% left
225
Q

aetiology of cleft lip and/or palate
environment

A
  • social deprivation
  • smoking
  • alcohol
  • anti-epileptics
  • multivitamins decrease likelihood 25%
226
Q

dental features of cleft lip and/or plalate

A
  • impacted teeth
  • crowding
  • hypodontia
  • supernumeraries
  • hypoplastic teeth
  • caries
227
Q

achondroplasia overview

A
  • problem with endochondrial ossification
  • defects in long bones (short limbs) = dwarfism
  • defects in base of skull
  • retrusive middle third of face - depressed nasal bridge
  • frontal bossing - unusually prominent forehead
228
Q

crouzons syndrome overview and dental features

A
  • also known as craniofacial dysostosis
  • premature closure of cranial sutures (fibrous joints) esp coronal and lamdoid
  • proptosis (shallow orbits), orbital dystopia (uneven orbits)
  • retusion and vertical shortening of midface
  • prominent nose
  • class III malocclusion
  • narrow spaced teeth
229
Q

crouzons syndrome tx

A
  • surgical intervention
  • distraction osteogenesis - break bones and gradually pull bones apart over time
230
Q

types of tooth movement

A
  • physiological: tooth eruption; mesial drift
  • orthodontic: from externally generated forces
231
Q

physiological bases of orthodontic tooth movement

A
  • if an external force is applied to a tooth - the tooth will move as the bone around it remodels
  • the bony remodelling is mediated by the periodontal ligament
  • if a tooth has no PDL or is ankylosed it will not move
  • cementum is much more resistant to resorption that bone - although some degree of root resorption after orthodontics should be expected
232
Q

theories for ortho tooth movement

A
  • differential pressure theory
  • mechano-chemical theory
233
Q

theories for ortho tooth movement
differential pressure theory

A
  • in areas of compression bone is resorbed
  • in areas of tension bone is deposited
  • when forces applied to crown –> PDL fibres move
234
Q

theories for ortho tooth movement
mechano-chemical theory

A
  • cell-mediated interactions take place
  • cell shape changes occur within PDL and adjacent alveolar bone - initiates signalling interactions between cells - eg production and release of cytokines
  • cytokines may cause target cells to release other mediators
  • mechanical loading = fluid movement, stretching and compression of fibres within the PDL
  • see flow chart diagram
235
Q

what controls differential pressure theory/mechano-chemical theory

A
  • osteoblasts!!
  • in areas of compression: osteoblasts bunch up and expose osteoid layer - giving osteoclasts access to resorb bone and send signals to osteoclasts (eg RANKL) to recruit and activate osteoclasts
  • in areas of tension: osteoblasts are flattened covering osteoid layer - preventing osteoclasts from accessing bone, osteoblasts secrete collagen and other proteins - forming organic matrix where they can secrete hydroxyapatite crystals which form new bone
236
Q

what regulates bone remodelling

A
  • osteoblasts release another protein osteoprotegerin (OPG) which prevents osteoclastic differentiation and suppresses their activity
  • balance between amount of RANKL produced and amount of OPG produced regulates bone remodelling
237
Q

types of tooth movement

A
  • tipping
  • bodily movement - crown and root move together
  • intrusion
  • extrusion
  • rotation
  • torque
238
Q

tipping/centre of rotation

A
  • 35-60 grams of force
  • centre of rotation moves apically
239
Q

physiology of tooth movement
functional appliances

A
  • mandible is postured away from its normal rest position
  • facial musculature is stretched which generates forces transmitted to the teeth and alveolus
  • there may be an effect on facial growth:
  • eg class II cases restrict maxillary growth; promote mandibular growth; remodel the glenoid fossa
240
Q

mode of action of functional appliances

A
  • 30% skeletal change: growth of mandible; restraint of maxilla
  • 70% dentoalveolar change: retroclination of upper teeth; proclination of lower teeth
  • mesial migration of lower teeth
  • distal migration of upper teeth
  • aim to decrease overjet
  • combination of the above ahieves class I
  • can cause lateral open bite so ask pt to then wear at night only
241
Q

bodily movement tooth movement

A
  • 150-200 grams of force
  • movement of tooth so that crown and root maintain same vertical axis
  • allows tooth to maintain normal PDL width and stability
242
Q

intrusion tooth movement

A
  • 10-20 grams of force
  • force in apical direction
  • pressure on supporting structures is evenly distributed
  • bone resorption necessary - particularly at apical area and at alveolar crest
243
Q

extrusion tooth movement

A
  • 35-60 grams of force
  • orthodontic tooth movement in coronal direction
  • tension induced in supporting structures
  • bone deposition necessary to maintain tooth support
244
Q

rotation tooth movement

A
  • 35-60 grams of force
  • use of centre of rotation
  • stretched elastic chain on one side and stretched elastic module on other
245
Q

physiology of tooth movement
light forces

A
  • hyperaemia (increased blood flow) within PDL
  • resorption of lamina dura from pressure side - increased osteoclast activity
  • desposition of osteoid on tension side - increased osteoblast activity
  • socket remodelling
    * periodontal fibres reorganise
  • gingival fibres remain distored*
  • SLOW tooth movement
246
Q

physiology of tooth movement
moderate force

A
  • occlusion of BV of PDL on pressure side
  • hyperaemia of BV of PDL on tension side
  • cell free areas (hylinisation) on pressure side
  • period of stasis
  • increased endosteal vascularity “undermining resorption”
  • increased osteoclastic activity pressure side
  • relatively rapid tooth movement with bone deposition on tension side - tooth may become slightly loose
  • healing of PDL - reorganisation and remodelling
247
Q

physiology of tooth movement
excessive force

A
  • necrosis and undermining resorption takes place
  • resulting in permanent changes
  • lateral root resorption (RR) - significant if greater than 1/3 root length lost
  • PDL necrosis
  • anchorage loss
  • possible loss of tooth vitality
248
Q

physiology of tooth movement
factors affecting the response to orthodontic force

A
  • magnitude; duration; age; anatomy
  • light forces allow slow continuous tooth movement
  • moderate/heavy force: rapid movement initilly then 10-14 days with little movement (undermining resorption occurs)
249
Q

factors affecting the response to orthodontic force
age of pt

A
  • can move teeth at any age
  • cell turnover smaller in older pts - teeth move slower
250
Q

factors affecting the response to orthodontic force
anatomy

A
  • no bone (wasting/cleft) : lack of bone volume means you cant close space orthodontically
  • soft tissues can influence movement
  • mid-palatal suture
251
Q

negatives of tooth movement

A
  • pain and mobility
  • pulpal changes
  • root resorption
  • loss of alveolar bone support
  • relapse
252
Q

neo-natal face description

A
  • face is small compared to the cranium
  • eyes are large and ears are low set
  • forehead upright and bulbous - face appears broad
  • nasal region is vertically shallow
  • nasal floor close to inferior orbital rim
  • in aduly midface expands and nasal floor descends
253
Q

sites of facial growth

A
  • sutures
  • synchondroses
  • surface deposition
254
Q

what are sutures

A
  • specialised fibrous joints situatied between intramembrenous bone
  • each suture is band of CT which has osteogeniccells in centre and most peripheral of these cells provide new bone growth
255
Q

describe sutural bone growth

A
  • growth at sutures occurs in response to growing structures separating the bone
  • eg growth of calvarium in response to development of brain
  • where bones are pushed apart new bone forms in the suture
  • osteogenic cells in centre and most peripheral of these cells provides bone growth
  • suture growth occurs in areas of tension
  • when facial growth complete sutures fuse and become inactive
256
Q

what are synchondroses

A
  • cartilaginous joint found in the midline
  • exist between ethmoid, sphenoid and occipital bones
  • cartilage based growth centre with growth occuring in both directions
257
Q

describe growth at synchondroses

A
  • cartilage based growth centre with growth occuring in both directions
  • bones wither side of synchondroses are moved apart as growth takes place
  • new cartilage is formed in centre of a synchondroses
  • cartilage at the periphery is transformed into bone
258
Q

describe surface deposition growth

A
  • new bone is deposited beneath the perioseum over the surface of bone
  • both cranial and facial bones
  • in order for bones to maintain shape: as they grow resorption is also taking place
  • known as remodelling: process of depositio and resorption
  • the change in position of a bone due to remodelling is known as a “drift”
259
Q

describe growth of cranial vault and ages

A
  • growth occurs in two ways:
  • bone growth at sutures
  • surface deposition: external and internal surfaces are modelled through surface deposition and resorption to replace bones radially (radial expansion)
  • expands in response to growing brain until age 7
  • rate of growth greatest in first 3 years
260
Q

cranial vault growth after neural growth ceases

A
  • forehead continues to enlarge in response to expanding air sinuses (pneumatisation)
  • generally more pronounced in males
  • when facial growth is complete all the sutures fuse
261
Q

how many fontanelles present at birth

A
  • 6 fontanelles present at birth
  • exist where more than 2 bones meet
  • close by age 18 months
262
Q

describe growth at cranial base and ages

A
  • growth occurs in 2 ways: endochondral ossification (synchondrosis) & surface remodelling
  • half growth complete by age 3
  • spheno-ethmoidal synchondrosis fuse age 7
  • spheno-occipital synchondrosis close 13-15(F) and 15-17(M)
  • spheno-occipital synchondoris fuses at around 20 years
263
Q

what is relevance of growth of cranial base

A
  • occurs between ages 4-20 and causes overall increase in length of cranial base
  • anterior cranial base relatively stable after 7 years - used for superimposition in cephalometric analysis - allows orthodontist to assess skeletal changes due to growth/tx
264
Q

cranial base in ortho role

A
  • plays an important role in determeting how the maxilla and mandible relate to each other
  • shape/angle of cranial base affects the jaw relationship
  • maxilla articulates with anterior cranial base and mandible closely associated with posterior cranial base
  • small angle more likely class III skeletal relationship
  • large angle associated with class II skeletal pattern
265
Q

maxilla/nasomaxillary complex includes

A
  • orbits
  • nasal cavity
  • upper jaw
  • zygomatic process
266
Q

describe growth of maxilla/nasomaxillary complex

A
  • maxilla displaced downwards and forwards relative to anterior cranial base
  • growth tends to follow neural growth of brain and slows down approx age 7
  • forwards displacement of maxillary complex creates space for maxillary tuberosities and for eruption of molar teeth
  • sutural growth takes place at zygomatic and frontal bones and mid-palatine suture
  • surface deposition and resorption: deposition on lower border of hard palate and alveolar process; resorption on floor of nasal cavity and floor of orbits
267
Q

describe growth of the mandible

A
  • grows downwards and forwards
  • growth occurs at condylar cartilage
  • growth occurs by surface remodelling
  • reorption mainly anteriorly and lingually and deposition posteriorly and laterally
  • results in increased height of ramus and increase in length of dental arch - accomodates permanent teeth
268
Q

differences in growth of maxilla and mandible

A
  • in mandible increases in length by 26mm (M) / 20mm (F) and maxilla 8mm (M) and 5.5mm (F) between ages 4-20
  • in mandible growth accelerates during pubertal growth spurt - relevant to ortho tx planning
  • in maxillar growth very slow after 7 years old
  • in mandible growth slows to adult levels around 19 (M) / 17 (F) and in maxilllar at around 12
269
Q

timing of facial growth in maxilla and mandible

A
  • for both growth in width slows first, then length and finally height
  • for both jaws width complete before pubertal growth spurt
  • growth in length continues around puberty - in girls slows 14-15 years and boys 18 years
  • growth in height does not decline in girls 17-18 and boys early 20s
270
Q

tx which utilises growth best carried out when

A
  • tx which utilises growth of mandible: best if carried out during pubertal growth spurt
  • tx which utilises growth of maxilla: best before circumaxillary sutures and palate havef used ie early teenage years
271
Q

can we predict facial growth

A
  • not really with any degree of position
  • most clinicians will consider pt height in relation to chronilogical age to help determine whether pt has entered pubertal growth spurt
  • previous patterns of facial growth for an individual may be useful predictor for future growth
272
Q

recent views on control of growth

A
  • combination of genetic and environmental influences are involved
  • growth in one part of the skull influences another
  • primary cartilages of cranial base and nasal septum have intrinsic growth potential and extert genetic influence over growth
  • condylar caartilage (secondary) seems to act differently - possible mandible responds to changes in maxillary position - adaptive growth to maintain position of condyle in glenoid fossa and maintain occlusal relationship
273
Q

impact of facial growth on orthodontic tx

A
  • growth can affect severity of malocclusion - either improve or make worse
  • growth can be utilised to facilitate tx outcome: functional appliances; rapi maxillary expansion RME; OB reduction; protraction headgear
  • continues unfavourable growth patterns following tx can result in relapse
274
Q

growth rotations and affect on vertical relationship

A
  • growth rotation due to imbalance in growth of anterior and posterior face heights
  • forward rotations leads to short face: mandible rotates anticlockwise; more growth posteriorly than anteriorly; can lead to deep bite
  • backwards rotations leads to a long face: clockwise growth; can lead to anterior open bite
275
Q

aduolt facial growth summary

A
  • very variable
  • continues slowly throughout life
  • growth in length contunues into early 20s (M) and late teens (F)
  • tendency to increase overall length, and prominence of nose and chin (and forehead in men)
  • lips become thinner and more retrusive (soft tissue changes)
276
Q

measurement of facial growth changes

A
  • casts of the face
  • cephalometry
  • 3Dlaser scanning
  • 3D photogrammetry
277
Q

indications for taking lateral ceph

A
  • to aid diagnosis
  • tx planning: help clarify tooth movements to be achieved; orthodontics or orthognathic surgery; orthograthic planning
  • progress monitoring: fixed appliance tx; functional appliance tx; monitoring facial growth
  • research projects
278
Q

what can be analysed on lateral ceph

A
  • relationship between jaws and cranial base
  • relationship between upper and lower jaw
  • position of teeth relative to jaw
  • soft tissue profile
279
Q

eastman analysis

A
  • measures antero-posterior position of mandible and maxillar relative to base of skull: SNA; SNB
  • position of mandible relative to maxilla: ANB (anteroposterior); MMPA or FMPA (vertical)
  • angulation of teeth to maxilla and mandible: UIMxP; LIMnP
  • vertical facial proportions: LAFH/TAFH ratio
280
Q

potential errors in cephalometry

A
  • radiographic projection errors: magnification; distortion
  • errors within measuring system
  • errors in landmark identification: quality of image; landmark definition and location
281
Q

reference structures for superimposition in lateral ceph

A
  • anterior wall of sella tursica
  • middle cranial fossa
  • anterior surface of zygomatic process
  • anterior border of the chin
  • outline of the mandibular canal
  • inner cortical plate of mandibular symphysis

BDS3 - CDS (13 decks)

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