Ortho Flashcards
(292 cards)
1
Q
what type of bone formation for maxilla and mandible
A
intramembranous ossification
2
Q
what are the pre-existing cartilagenous skeletons of the face
A
- primary cartilage- nasal capsule and meckels cartilage
3
Q
base of skull formation vs vault
A
- base of skull by endochondral ossification
- vault by intramembrenous ossification
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
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
6
Q
sites of facial growth
A
- sutures
- synchondroses
- surface deposition
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
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
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
10
Q
what is known as a drift
A
change in position of bone due to remodelling
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
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
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
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
15
Q
what comprises nasomaxillary complex
A
- orbit
- nasal cavity
- upper jaw
- zygomatic process
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
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
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
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
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
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
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
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
24
Q
indications for taking a lateral cephalogram
A
- aid diagnosis of skeletal class or vertical discrepancy
- treatment planning
- progress monitoring
25
how to maintain reproducability of lateral cephalometry
* 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
26
what to analyse on lateral cephalogram
* relationship between jaws and cranial base
* relationship between upper and lower jaw
* position of teeth relative to the jaws
* soft tissue profile
27
lateral ceph main reference landmarks
* 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
28
lateral cephalogram
what measures antero-posterior poisiton of maxillar and mandible relative to base of skull
* SNA
* SNB
29
lateral cephalogram
what measures position of mandible relative to maxilla
* anteroposterior - ANB
* vertical - MMPA or FMPA
30
lateral cephalogram
ANB angles and what that translates to
* Class I 2-4 degrees
* Class II mild 4-6
* Class II severe > 8
* Class III milld 0-2
* Class III severe < -3
31
lateral cephalogram
what is RFA
* ratio facial height
* ratio of lower anterior face height to total face height
32
errors in cephalometry
* radiographic projection errors - magnification or distortion
* errors with measuring system
* errors in landmark identification - quality of image etc
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Reference lines
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hard stainless steel wire made by
* drawing the metal in a cold state through a series of dies of successively smaller diameter
* called hard working - gives SS its spring properties
37
Bauschinger effect
* 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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fractures of stainless steel in orthodontics can occur when
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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type of stainless steel used in orthodontics
* 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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composition of orthodontic stainless steel
* 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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function of chromium in orthodontic stainless steel
* 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
42
function of nickel in orthodontic SS
* 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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function of titatium in orthodontic SS
* prevents precipitation of chromium carbides at grain boundaries when alloy heated
* carbon combines with titanium in preference to the chromium
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difference between austenite and martensite
* 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
45
what is I.O.T.N
* 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)
46
types of retainer
* conventional removable retainers
* thermoplastic retainers
* bonded retainers
47
equiptment for adams clasp construction
* study cast
* 0.7mm hard stainless steel wire
* no 64 pliers
* wire cutters
48
adams clasp function
* 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
49
advantages of the adams clasp
* 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
50
acronym for ortho URA design
* ARAB
* Active component
* Retentive
* Anchorage
* Baseplate
51
URA aim
description of what the appliance design is aiming to achieve
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URA ARAB
* 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
53
what is the active component used to retract canines URA
* 13 + 23 ; palatal finger springs + guards
* 0.5mm HSSW
54
retentive components of URA
* 16 + 16 ; adams clasp ; 0.7mm HSSW
* 11 + 21 ; southend clasp ; 0.7mm HSSW
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URA anchorage and baseplate prescription
* anchorage - moving only (insert number) teeth (tick)
* baseplate - self-cure PMMA
56
remodellig of bone controlled by
* periodontal ligaments or fibres
* PDL is collection of fibres surrounding root which act as a buffer against shock
57
baseplate modification URA if reducing overbite
* baseplate - self-cure PMMA
* flat anterior bite plane(FABP) ; overjet (OB) + 3mm
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type of tooth movement in removable orthodontics
tipping movement
59
removable orthodontics advantages
* 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
60
removable orthodontics disadvantages
* 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
61
adjustment of adams clasp
* 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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arrow heads for adams clasp checklist
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
63
checklist for bridge of adams clasp
1. bridge must stand clear of tooth at approx 45degrees to crown
2. should not protrude above occlusal surface
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other important checklists for adams clasp
(not including bridge/arrowheads)
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
65
why do we add OJ + 3mm to baseplate FABP
* to decrease risk of lower anteriors getting stuck behind FABP
66
what happens to teeth when FABP added to URA
* 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
67
names of retentive components URA and type of wire
* adams clasp ; 0.7mm HSSW (0.6mm on deciduous teeth)
* southend clasp ; 0.7mm HSSW
* labial bows ; 0.7mm HSSW
68
names of active components and type of wire
not buccally placed
* finger springs + guard ; 0.5mm HSS
* Z-spring (doubel cantilever) ; 0.5mm HSS
* flapper spring ; 0.5mm HSS
* T-spring ; 0.5mm HSS
69
names of active components and type of wire
buccally placed
* 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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type of wire for stops URA
* 0.7mm HSS
* flattened
* pssive component
71
fitting a URA steps
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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what is used to retract buccally placed canines
* 13 + 23 buccal canine retractors
* 0.5mm HSSW + 0.5mm I.D tubing
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URA pt information and instructions
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
74
what can be added to URA to fix anterior cross bite
* posterior bite plane
75
how does posterio bite plane work
* 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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components of adams clasp
* bridge
* arrowhead
* flyover
* leg
* tag
79
what is active component used to reduce a on 11, 21, 12, 22
* 21, 22, 11, 12 roberts retractor ; 0.5mm HSSW ; 0.5mm ID tubing
* 13 and 23 mesial stops ; 0.7mm (flattened) HSSW
80
what is URA used to expand the upper arch
* midline palatal screws
* ideally 4 adams clasps (on 6s and 4s) for retention
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what is orthodontics
* 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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tx for skeletal discrepancies
growing pt
* 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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tx for skeletal discrepancies
adults who have completed growth
* orthognathis surgery
* single jaw or bimaxillary process
87
what can modify jaw growth
* functional appliances
* twin block
88
cleft team
* orthodontist
* cleft team
* ENT
* speech therapy
* maxfax surgeon
* plastic surgeon
* dental practitioner
89
growth and development issues
* crowding
* spacing
* increased overjet
* reverse overjey
* hypodontia
* supernumeraries
* delayed dental development
* anterior openbite
* deep bite
* ectopic teeth
* anterior/posterior crossbites
90
orthodontic aids to diagnoses
* study models
* radiographs - OPG, lateral cephalogram
* photographs
* sensibility tests
* cone beam CT scan
91
aims of orthodontic tx
* stable
* functional
* aesthetic occlusion
* prior to restorative work
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types of appliances
* 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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benefits of orthodontic tx
* 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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risks of orthodontic tx
* 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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aeitiology of malocclusion
general aetiological factors
* 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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components of the facial skeleton
* 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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aeitiology of skeletal variation
* genetic and environmental factors
* strong hereditary component - class III is hereditary
* environmental factors: masticatory muscles, mouth breathing, head posture
99
aeitiology of malocclusion
three planes of space
* antero-posterior
* vertical
* transverse
100
antero-posterior relationship
class I cephalometries
* 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
101
aeitiology of malocclusion
class II overview and SNA/B/ANB angles
* 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
102
aeitiology of malocclusion
class III overview and SNA/B/ANB values
* 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
103
aeitiology of malocclusion
dento-alveolar compensation
* 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
104
facial heigh average clinical values
* 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
105
aeitiology of malocclusion
vertical jaw relationship summary
* 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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vertical jaw relationship
long facial type
* LAFH:TAFH proportion >55%
* FMPA>31degrees
* steep incline in mandibular plane
* backward mandibular growth rotation
* anterior open bite tendency
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vertical jaw relationship
short facial type
* LAFH:TAFH proportion <55%
* FMPA<23degrees
* tendency to parallelism of jaws
* forward mandibular growth rotation
* deep overbite tendency
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aetiology of malocclusion
transverse plane types
* arch width discrepancies
* mandibular displacement
* facial asymmetries
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aetiology of malocclusion
arch width discrepancies
* 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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aetiology of malocclusion
mandibular displacement
* 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
111
aetiology of malocclusion
facial asymmetries
* 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
112
arch size discrepancies
dento-alveolar disproportion
* 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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aetiology of malocclusion
* skeletal
* dental - missing teeth etc
* soft tissue - lip trap
* other - habits
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local causes of malocclusion
* 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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aetiology of malocclusion
variation in tooth number
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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aetiology of malocclusion
supernumerary teeth
* a tooth or tooth like entity which is additional to normal series
* most common anterior maxilla
* males>females
* four types
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four types of supernumerary teeth
1. conical
2. tuberculate
3. supplemental
4. odontome
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aetiology of malocclusion
conical supernumerary
* 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
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aetiology of malocclusion
tuberculate supernumerary
* 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
aetiology of malocclusion
supplemental supernumerary
* 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
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aetiology of malocclusion
odontome supernumerary
* compound: discrete denticles - tooth like objects in a mass
* compled: disorganised mass of dentine, pulp and enamel
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most common explanation for retention of upper incisors
* tuberculate supernumerary
* or trauma to deciduous incisors
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aetiology of malocclusion
hypodontia
* 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
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management of hypodontia - absent successor
* 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
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infra occluded primary molars
* appears submerged
* process where tooth fails to achieve or maintain its occlusal relationship with adjacent teeth
* temporary ankylosis
* percussion sound
* common 1-9%
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aetiology of malocclusion
retained primary teeth - alarm bells if
* 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
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causes of retained primary teeth
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
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early loss of primary teeth causes
* trauma - incisors most commonly affected
* periapical pathology
* caries
* resorption by successor
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importance of early loss of primary teeth
* 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
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early loss of primary teeth
localisation of crowding depends on
* which tooth is X
* when tooth is X
* pts inherent crowding
* early loss of Es lead to 6s closing gap - now 5s impacted
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balancing/compensating extractions
* 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
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factors that influence impact of loss of 6s
1. age at loss
2. crowding
3. malocclusion
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age at loss of 6s
* 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
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crowding effect on unscheduled loss of permanent teeth
* upper arch - potential for rapid space loss
* lower arch:
* spaced arch - will have spaces
* aligned arch - will have spaces
* crowded - best results likely
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unscheduled loss of central incisor
* 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
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aetiology of malocclusion
macrodontia
* 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
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aetiology of malocclusion
microdontia
* tooth/teeth smaller than average
* localised or generalised
* leads to spacing
* linked to hypodontia
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aetiology of malocclusion
ectopic teeth
* can be any teeth but mostly third molars, upper canines, first molars, upper centrals
* transpositions
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aetiology of malocclusion
ectopic maxillary canines
* 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
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ectopic canines clinical assessment
* visualisation/palpation of any obvious bumps of 3
* inclination of 2
* mobility of c or 2
* colour of c or 2
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aetiology of malocclusion
abnormal tooth form types
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
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ectopic canines management options
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
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ectopic first molars cause/sign/management
* 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
ectopic upper central incisors causes
* supernumerary - tuberculate, odontome
* trauma to primary predecessor:
* ankylosis of primary tooth
* displacement of tooth germ
* dilaceration of root
145
aetiology of malocclusion
transpositions
* 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
aetiology of malocclusion
local abnormalities of soft tissues
* 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
aetiology of malocclusion
local pathology
* caries
* cysts
* tumours
148
orthodontic assessment
why
* determine if any malocclusion is present
* identify any underlying causes
* decide if tx is indicated - either refere or devise tx plan
149
orthodontic assessment
ideal occlusion andrews 6 keys
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
orthodontic assessment
normal occlusion definition
* more commonly observed than ideal occlusion
* minor deviations that do not constitute and aesthetic or functional problem
151
orthodontic assessment
PMH contra-indications
* allergy to nickel or latex
* epilepsy/drugs: some drugs cause gingival hyperplasia
* imaging: cannot have MRI scan with braces
152
orthodontic assessment
habits
* thumb sucking
* lower lip sucking
* tongue thrust
* chewing finger nails
153
orthodontic assessment
extraoral overview
* skeletal bases
* soft tissues
* TMJ
154
orthodontic assessment
vertical skeletal assessment
* 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
orthodontic assessment
soft tissues overview
* 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
orthodontic assessment
tongue position and swallowing pattern affects
* 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
occlusal features of thumb habit
* 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
orthodontic assessment
competent/incompetent lip/lip trap
* 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
orthodontic assessment
TMJ
* 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
orthodontic assessment
intra-oral examination check
* 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
orthodontic assessment
assessment of lower arch
* 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
orthodontic assessment
assessment of upper arch
* 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
orthodontic assessment
teeth in occlusion assessment
* can assess in RCP or ICP
* incisor relationship (BSI definitions)
* overjet
* overbite
* molar relationship (angles classification)
* canine relationship
* cross bites
* centre lines
164
BSI incisor relationship
* 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
angles classification
* 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
orthodontic assessment
special investigations
* radiographs: OPT; maxillary anterior occlusal; lateral cephalogram
* vitality tests
* study models
* photographs
167
orthodontic assessment
what to put on referral level
* 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
ortho tx planning
general principles
* 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
ortho tx planning
diagnosis description
* 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
2 types of cephalometry
* lateral cephalometry
* PA cephalometry: shows transverse skeletal malocclusions; rare problems
171
why is correct orthodontic diagnosis important
* 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
objectives or orthodontic tx
* to produce an occlusion which is:
* stable
* functional
* aesthetics
* and potentially to facilitate other forms of dentistry (crowns, bridges etc)
173
ortho tx planning
factors affecting tx plan
* 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
ortho tx planning
different aims of tx
* 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
ortho tx planning
stages of tx planning
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
ortho tx planning
types of crowding assessment
* two ways of assessing crowding:
* measure space available and space required
* overlap technique
177
ortho tx planning
types of crowding assessment
* two ways of assessing crowding:
* measure space available and space required
* overlap technique
178
crowding assessment
method 1: measuring space available and space required
* 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
crowding assessment
method 2: overlap technique
* measure how much teeth overlap
* add them all together to get degree of crowding
180
ortho tx planning
space required in lower arch general principles
* 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
ortho tx planning
if ALL soace from extractions will need to be used
* need to reinforce anchorage
* headgear use, transpalatal arch or temporary anchorage device (TAD)
* to stop pts teeth moving forward
182
ortho tx planning
retention phase
retainers needed to hold teeth in place after active movement
183
ortho tx planning
tx options (BDS4 common q)
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
ortho tx planning
limitations of orthodontic tx
* 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
ortho tx planning
who will do tx
* 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
URA active component to reduce OJ for 21, 22, 11, 12 and reduce OB
* 22, 21, 11, 12; roberts retractor; 0.5mm HSSW + 0.5mm I.D tubing
* stops : 13 + 23; mesial stops; 0.7mm flattened HSSW
187
ortho lab stuff to know
* 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
facial growth importance for orthodontics
* 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
life in utero two phases
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
neural crest cell migration
* 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
what forms neural tube and development disorders at this stage
* 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
neural crest cell development
* 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
describe early development of the face
* 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
defects of the face (particularly in midline) may be closely related to
defects of the anterior parts of the brain
195
cleft formation
* 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
when does extension and fusion of the facial processes occur
weeks 5-7
197
foetal stage
8 weeks to term
198
skull division
* 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
describe intramembrenous bone formation
* 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
describe endochondral bone formation
* 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
base of skull formation
* 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
vault of skull formation
* 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
fontanelle closure
* anterior fontanelles closes about 2 years of age
* posterior at about 1 year
204
describe growth of vault
* 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
embryonic facial cartilages
* meckels cartilage
* auditory capsule
* cranial base
* nasal capsule
* sphenoid
206
maxilla and mandible formation
* form intramembranously
* but develop adjacent to pre-existing cartilagenous skeletons:
* nasal capsule and meckels cartilage (6 weeks)
207
describe development of mandible
* 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
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mandible development units and growth stimulae
* 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
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three main sites of secondary cartilage formation in mandible and when the cartilage appears/disappears
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
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summary of prenatal face/skull growth
* 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
primary abnormality definition
* 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
secondary abnormality definition
* 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
deformation and agenesia definitions
* 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
sequence and syndrome definition
* 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
facial syndromes causing maxillay hypoplasia
* aperts syndrome
* crouzons syndrome
* downs syndrom
* foetal alcohol syndrom
* achondroplasia
* cleft lip/palate
216
facial syndromes causing mandibular problems
* treacher collins syndrom
* pierre-robin
* sticklers syndrome
* turners syndrome
* hemifacial microsomia
217
facial syndromes arising from early problems with facial development
* 1-8 weeks
* environmental - foetal alcohol syndrome
* genetic
* multifactorial: hemifacial microsomia, treachers collins, cleft lip and palate
218
foetal alcohol syndrome cause/occurs on
* 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
foetal alcohol syndrome features
* microcephaly - small head
* short palpebral fissure
* short nose
* long upper lip with deficient philtrum
* small midface
* small mandible
* midl mental/learning difficulty
220
hemifacial microsomia cause/features
* 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
treacher collins cause/features
* 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
cleft lip and palate epidemiology
* 1:700 live births
* 70% sporadic - no FH
* cleft lip and palate/cleft lip males>females
* cleft palate demales > males
223
when do lips/palat fuse
* lips: day 28-38 (4-5 weeks)
* palate: day 42-55 (6-8 weeks)
224
aetiology of cleft lip and/or palate
genetic
* monozygotic twins
* syndromes
* familial fattern
* 66% left
225
aetiology of cleft lip and/or palate
environment
* social deprivation
* smoking
* alcohol
* anti-epileptics
* multivitamins decrease likelihood 25%
226
dental features of cleft lip and/or plalate
* impacted teeth
* crowding
* hypodontia
* supernumeraries
* hypoplastic teeth
* caries
227
achondroplasia overview
* 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
crouzons syndrome overview and dental features
* 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
crouzons syndrome tx
* surgical intervention
* distraction osteogenesis - break bones and gradually pull bones apart over time
230
types of tooth movement
* physiological: tooth eruption; mesial drift
* orthodontic: from externally generated forces
231
physiological bases of orthodontic tooth movement
* 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
theories for ortho tooth movement
* differential pressure theory
* mechano-chemical theory
233
theories for ortho tooth movement
differential pressure theory
* in areas of compression bone is resorbed
* in areas of tension bone is deposited
* when forces applied to crown --> PDL fibres move
234
theories for ortho tooth movement
mechano-chemical theory
* 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
what controls differential pressure theory/mechano-chemical theory
* 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
what regulates bone remodelling
* 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
types of tooth movement
* tipping
* bodily movement - crown and root move together
* intrusion
* extrusion
* rotation
* torque
238
tipping/centre of rotation
* 35-60 grams of force
* centre of rotation moves apically
239
physiology of tooth movement
functional appliances
* 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
mode of action of functional appliances
* 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
bodily movement tooth movement
* 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
intrusion tooth movement
* 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
extrusion tooth movement
* 35-60 grams of force
* orthodontic tooth movement in coronal direction
* tension induced in supporting structures
* bone deposition necessary to maintain tooth support
244
rotation tooth movement
* 35-60 grams of force
* use of centre of rotation
* stretched elastic chain on one side and stretched elastic module on other
245
physiology of tooth movement
light forces
* 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
physiology of tooth movement
moderate force
* 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
physiology of tooth movement
excessive force
* 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
physiology of tooth movement
factors affecting the response to orthodontic force
* 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
factors affecting the response to orthodontic force
age of pt
* can move teeth at any age
* cell turnover smaller in older pts - teeth move slower
250
factors affecting the response to orthodontic force
anatomy
* no bone (wasting/cleft) : lack of bone volume means you cant close space orthodontically
* soft tissues can influence movement
* mid-palatal suture
251
negatives of tooth movement
* pain and mobility
* pulpal changes
* root resorption
* loss of alveolar bone support
* relapse
252
neo-natal face description
* 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
sites of facial growth
* sutures
* synchondroses
* surface deposition
254
what are sutures
* 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
describe sutural bone growth
* 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
what are synchondroses
* cartilaginous joint found in the midline
* exist between ethmoid, sphenoid and occipital bones
* cartilage based growth centre with growth occuring in both directions
257
describe growth at synchondroses
* 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
describe surface deposition growth
* 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
describe growth of cranial vault and ages
* 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
cranial vault growth after neural growth ceases
* 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
how many fontanelles present at birth
* 6 fontanelles present at birth
* exist where more than 2 bones meet
* close by age 18 months
262
describe growth at cranial base and ages
* 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
what is relevance of growth of cranial base
* 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
cranial base in ortho role
* 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
maxilla/nasomaxillary complex includes
* orbits
* nasal cavity
* upper jaw
* zygomatic process
266
describe growth of maxilla/nasomaxillary complex
* 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
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describe growth of the mandible
* 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
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differences in growth of maxilla and mandible
* 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
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timing of facial growth in maxilla and mandible
* 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
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tx which utilises growth best carried out when
* 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
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can we predict facial growth
* 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
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recent views on control of growth
* 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
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impact of facial growth on orthodontic tx
* 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
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growth rotations and affect on vertical relationship
* 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
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aduolt facial growth summary
* 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)
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measurement of facial growth changes
* casts of the face
* cephalometry
* 3Dlaser scanning
* 3D photogrammetry
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indications for taking lateral ceph
* 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
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what can be analysed on lateral ceph
* relationship between jaws and cranial base
* relationship between upper and lower jaw
* position of teeth relative to jaw
* soft tissue profile
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eastman analysis
* 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
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potential errors in cephalometry
* radiographic projection errors: magnification; distortion
* errors within measuring system
* errors in landmark identification: quality of image; landmark definition and location
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reference structures for superimposition in lateral ceph
* 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
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