Orthodontics Flashcards
growth & developmental disorders of jaws
- increased overjet (front teeth further forwards)
- deep overbite (vertical height between incisors decreased)
- anterior crossbite - lower tooth in front of uppers
- posterior crossbite - lower molars outside uppers
- retained deciduous teeth
- early loss of deciduous teeth
- ectopic teeth
- impacted first molars
- crowding
- spacing
- trauma
- anterior open bite - front teeth do not occlude
- lateral open bite - lateral teeth do not occlude
- reverse overjet - lowers in front of uppers
tx options in ortho (5)
- removeable appliances - used to tip teeth, open bites & maintain space
- functional appliances - used to modify jaw growth
- fixed appliances - 3D control of tooth position
- XLA of teeth - to reduce crowding
- orthognathic surgery - breaking jaw to modify skeletal relationships
what children are likely to have 2x risk of trauma to front teeth
those with >3mm overjet
benefits of ortho tx
- improved function
- improved appearance
- improved dental health (easier cleaning)
- reduce risk of trauma
- may allow for space rearrangement in hypodontia to allow for bridges or implants
risks of ortho tx
decalcification
relapse
root resorption
pain
soft tissue trauma
poor compliance
loss of tooth vitality
inhalation of small components
candida infection
andrew’s 6 keys of an ideal occlusion
- tight approximal contacts with no rotations
- class I incisors
- class I molars
- flat occlusal plane or slight curve of Spee
- long axis of teeth have slight mesial inclination except lower incisors
- crowns of canines back to molars have a lingual inclination
antero posterior skeletal assessment
class I = normal
class II = mandibular retrognathia
div 1 - upper incisors proclined
div 2 - upper incisors retroclined
class III = maxillary retrusion
how to assess AP skeletal class
- visually by looking at ptx profile with frankfort plane parallel to floor
- palpation of skeletal bases with frankfort plane parallel to floor
- using cephalometry to measure skeletal discrepancy
vertical assessment
measured using frankfort mandibular plane angle (FMPA) to test if angle between base of skull and mandible is correct:
frankfort plane is from poiron to orbitale & mandibular plane from menton to gonion & these lines should meet at the back of the head
transverse assessment
assessing symmetry of face - ignore the nose
assessing the lips
competency of lips is whether they come together at rest or not - if not they are incompetent
what is a lip trap
lower lip is trapped behind the upper incisors - this may procline the upper incisors in time & may indicate tx instability at end of tx
lower lip may also retrocline the lower incisors if it is very taught which indicates end of tx instability
tongue thrust
can be cause / effect of AOB
if already an OB tongue will have to thrust forwards to produce anterior oral seal on swallowing
less common = tongue thrust causing proclination of upper incisors leading to AOB; if only 7s are touching this usually indicates skeletal anomaly as opposed to one due to tongue thrust
what should an aesthetic smile show
- whole height of upper incisors
- only interproximal gingivae visible
- upper incisors not touching lower lip
- upper incisors running parallel to lower lip
- smile to at least the upper first premolars
thumb sucking
can lead to proclination of upper anteriors & retroclination of lower anteriors leading to a localised AOB or an incomplete open bite (this is where there is overlap of lowers & uppers but no contact between them) it can also cause narrowing of upper arch with a unilateral posterior crossbite
degrees of crowding
mild = 1-4mm
moderate = 4-8mm
severe = 8+mm
3 methods of assessing crowding
- examining space available against required
- using the overlap technique
- mixed dentition analysis
space required in lower & upper arch
upper arch = 22mm; canine = 8mm, premolars = 7mm
lower arch = 21mm; canine & premolars = 7mm
most commonly missing teeth
8s > 5s > upper 2s > lower 1s
tooth most commonly ectopic
uppers = 3
lowers = 5
this is because they are the last teeth to erupt in the arch
when teeth are in occlusion we look for
incisor classification
overjet
overbite
centre lines
molar relationship
canine relationship
crossbite
mandibular displacement
incisor class
class I - lower edges occlude with or lie immediately below cingulum of upper centrals
class II div 1 - lower edges lie posterior to cingulum of upper centrals which will be of average inclination or will be proclined
class II div 2 - lower edges lie posterior to cingulum of upper centrals but upper centrals in this care are retroclined so overjet may be minimal or increased
class III - lower edges lie anterior to cingulum of upper centrals so overjet will be reduced or reversed
overjet
horizontal distance between labial surface of tips of upper incisors and the surface of the lower incisors
average is 2-4mm
teeth should be in occlusion and ruler held parallel to occlusal plane, distance measured from greatest overjet on most prominent upper incisor
overbite
vertical overlap of incisor teeth
average overbite will have upper incisors overlap incisal 1/3 of crowns of lower incisors; if >50% covered it will be increased overbite but if <20% then a decreased overbite
if OB markedly incomplete where there is no vertical overlap this is AOB
molar relationship
class I - upper 1st permanent molar mesiopalatal cusp occluding with fossa of lower 1st permanent molar
class II - behind this
class III - in front
canine relationship
class I - upper permanent canine occluding embrasure between lower canine & 1st premolar
class II - upper permanent canine occluding whole tooth width further anteriorly and lies in embrasure between lower permanent canine & lower lateral incisor
class III - upper permanent canine occluding whole tooth width further posteriorly than normal and occludes in embrasure area between 1st & 2nd premolars
crossbite
can be bi or unilateral
often in unilateral there will be mandibular displacement which can affect TMJ
can be posterior or anterior & buccal or lingual
how do you assess crowding
measure space available and space required using study models and overlap technique
general principles of space required in lower arch
mild 0-4mm = non-ext (stripping) / XLA 5s
moderate 4-8mm = XLA 5s/4s
severe 8+mm = XLA 4s
if XLA in lower arch
yes - XLA in upper arch also
if not - XLA upper arch only or distalise UBS using headgear
writing ortho txp
- diagnosis
- problem list
- txp
- list successive stages stating tooth movements to be carried out & appliances to be used
- estimate length of tx
- if not possible to give detailed plan indicated when it will be reviewed i.e. following eruption of teeth
tx options
- accept malocclusion
- XLA only
- URA
- functional appliances
- fixed appliances
- complex tx involving ortho and restorative tx or ortho & orthognathic surgery
supernumerary teeth
additional to those in the normal series
commonly in anterior maxilla
M > F
4 types: conical, tuberculate, supplemental, odontome
hypodontia
developmental absence of 1 or more teeth
F > M
8s > upper 2s > 5s
retained primary teeth
suspicious when difference of 6mths between shedding of contra lateral tooth
often caused by absent successor, ectopic or dilacerated successor, primary molars being infra occluded
absent successor
tooth should be kept for as long as possible if it has a good prognosis or XLA as early as possible to encourage early space closure but early ortho referral should be sought for advice
common ectopic tooth
upper canine
infra occluded primary molars
primary molars may become occluded by its adjacent teeth if it fails to achieve or maintain its occlusal relationship with adjacent teeth
can cause temporary ankylosis and is defined by a specific percussion sound
management depends on whether there is a permanent successor present or not; if there it should be kept under review & should be XLA if contacts are going subgingival or root formation of its successor is near completion and if not there depending on crowding it should be either retained with an onlay or XLA for space management
balancing v compensating XLA
balancing - XLA tooth from opposite side of same arch to minimise midline shift
compensating - XLA from opposing quadrant to minimise occlusal interference so as to maintain occlusal relationship
when to balance / compensate
incisors - do not need to be balanced or compensated
canines - can give centreline shift in perm dentition if there is unilateral loss so balancing should be considered
molars - will be drift of 6s mesially is Ds and Es xla but not usually balanced; there will be more space loss in the upper teeth than the lower teeth
when should 6s be XLA
mandible - when bifurcation of 7s forming so when coming through they can close the gap being formed; if too early there will be poor space closure and if too late distal drift of 5s; only compensating for lower 6s
maxilla - timing doesn’t matter so much, 7s will become distally inclined there will not be as much space closure
where is primitive streak
adjacent to neural tube formation
neural tube
formed at end of week 3 from neural folds & failure to fuse causes spina bifida (linked to folic acid deficiency)
neural tube develops into brain & spinal cord
neural crest migration
during folding of neural plate, cells develop from ectoderm at edge of groove known as neural crest cells
undergo extensive migration in developing embryo & allows development into many different cell types
note - ectomesenchyme forms bone, CT, pulp, dentine, cementum but not enamel; ectoderm forms this
what happens if disturbance of neural crest cells
can lead to midline deficiency or median cleft syndrome
facial development
occurs in first 8wks after fertilisation
formed from migrating neural crest cells either from fronto-nasal process or pharyngeal arches
failure of fusion between various processes or between palatine processes may lead to cleft formation
upper lip & anterior palate also have different embryological origins from posterior palate so can fuse at different times so cleft lip (with alveolus) & cleft palate can occur separately or together
pharyngeal arches
formed at 4wks from migrating neural crest cells; these migrating neural crest cells also migrate to form frontonasal process; these pharyngeal arches will contain a cranial nerve i.e. 1st pharyngeal arch is CN V, 2nd pharyngeal arch starts to grow over 3rd & 4th pharyngeal arch which forms sinus cervicalis
facial processes then extend & fuse at wk 7
intramembranous bone formation
vault of skull, maxilla & most of mandible formed by intramembranous ossification; where bone is directly deposited into primitive mesenchymal tissue
endochondral ossification
base of skull & parts of mandible formed by endochondral bone formation; this is where a hyaline cartilage model is formed then ossified later, there will be several centres of ossification with active growing regions
summary of facial growth
- ossification of face & skull commence at 7-8wks
- neuro & viscerocranium form face
- vault of skull formed intramembranously
- base of skull formed by endochondral ossification
- both maxilla & mandible form intramembranously but are preceded by a cartilaginous facial skeleton
- meckel’s cartilage precedes mandible & nasal capsule is the primary skeleton of upper face
- if failure of fusion of maxillary process & nasal elevation this can lead to cleft lip and / or palate
primary abnormality
defect in structure of organ / part of organ which can be traced back to an anomaly in its development
secondary abnormality
interruption of normal development of an organ that can be traced back to other influences i.e. chemical or infection
remember that a congenital abnormality is not always inherited
post natal growth of maxilla
grows downwards and forwards and occurs at sutures between maxilla and skull
it will be displaced by growth of nasal cartilage & cranial base
surface deposition occurs posteriorly & resorption anteriorly & inferiorly
post natal growth of mandible
generally grows downwards & forwards and growth occurs at the condyle
surface resorption anteriorly & lingually, deposition posteriorly & laterally
timing of facial growth
- maxilla & mandible first grow in width, length then height
- growth in width of both jaws is completed before pubertal growth spurt; includes growth of both arches
- growth in length of both jaws continues throughout puberty; stops at 14-15 in girls & 18 in boys
- growth in height of jaws continues longest stopping at 17-18 in girls and early 20s in boys
uses of cephalograms
- gross inspection of anatomy & physiology
- assess dentoskeletal relationships
- assess soft tissue relationships to hard tissues
- prognosis & txp
- monitoring facial growth
- assess changes due to tx & growth
indications of cephalograms
- may aid diagnosis of skeletal classifications in marked AP discrepancies
- can be used to measure vertical discrepancies
- especially useful in class IIII malocclusions
- can be used pre tx & monitoring during tx to see progress being made; useful for both upper & lower fixed & functional appliances
- research
limitations of cephalograms
can be magnified or distorted leading to errors in landmark identification
could be errors within system of measurement causing problems too
deciduous dentition eruption
ABDCE - lowers before uppers
when to compensate / balance XLA in deciduous teeth
a’s & b’s - neither
c’s - must be balanced (opposite tooth same arch)
d’s - may cause small centreline shift but only balance if ptx going for GA for other reasons
e’s - tend not to balance e’s, there will be major space loss if 6 is unerupted especially in upper
upper canines
should be developing palatal & 90% will be palpable by 11yrs old
symmetrical mobile c’s can denote a correct eruption pattern
2 classifications of orofacial clefting
- cleft lip +/- palate - more common in males & east of scotland, lip occurs day 28-38 in utero
- cleft palate - more common in females & west of scotland, occurs day 42-55 in utero
care pathway for cleft patients
3mths - lip closure
6-12mths - palate closure
8-10yrs - alveolar bone graft
12-15yrs - definitive ortho
18-20yrs - surgery
class II div 1 malocclusion
increased OJ
why do we treat - risk of trauma signififcantly increased
4 main features:
1. skeletal pattern (AP, vertical, transverse)
2. soft tissues
3. dental factors
4. habits
tipping
only form of tooth movement possible for removeable appliances
force required = 1mm/mth
if movement over exerted then URA will just fall out
35-60g
bodily movement
movement of the whole tooth, tooth will slide along wire
force needed should not cause too much lasting damage with root resorption
150-200g
intrusion
pressure evenly distributed on supporting structures which will cause necessary bone resorption; especially noticeable at alveolar crest & apical area
too much force will tear rich blood supply at apex
10-20g
extrusion
tension induced along pdl producing bone deposition
if force > 35-60g then blood supply will tear
rotation
35-60g
apical root torque
causes movement of a root but keeps tooth in same position
form of tooth movement is inefficient as centre of rotation is a long way from end of the root
50-100g
functional appliances
will cause tooth movement; used to bring forward the mandible to correct class II occlusions
light force
under light force there will be hyperaemia (blood flow akin to mild trauma) within pdl, leads to appearance of osteoblasts & clasts. will be resorption of lamina dura & apposition of osteoid on tension side
remodelling of socket is known as frontal resorption
pdl fibres will then reorganise but gingival will remain distorted and this stored energy helps lead to relapse
moderate force
if moderate force on tooth there will be occlusion of blood vessels on side of pressure
will lead to cell free areas on pressure side (hyalinisation) & hyperaemia of vessels on tension side however
hyalinisation will cause a period of stasis but there will be an increase in endosteal vascularity leading to undermining resorption
once this occurs relatively rapid movement of tooth occurs & there is bone deposition on tension side
after this tooth can become slightly loose
there will be healing of the pdl with reorganisation, the gingival fibres will stay as they were however
excessive force
if tooth placed under excessive force there will be necrosis of tooth with undermining resorption present
resorption of root surfaces by osteoclasts
this all leads to permanent tooth damage & pain
5 displacement forces on a URA
- speech
- mastication
- gravity
- displacement by active components
- tongue & other soft tissues
why use self cure & not heat cure PMMA for the baseplate
much quicker to use
however,
not as strong, will contact more & may have more residual monomer that heat cured (boiled off in heart cure) & this can cause an allergic reaction
FABP
flat anterior bite plane
will correct an OB & nothing else
does this by increasing vertical dimension allowing the over eruption of posteriors which will raise the bite thus reducing the OB
lowers will be more likely to erupt as uppers will have adam’s clasps preventing further eruption
size of FABP should be OJ + 3mm; this is so lowers do not slip behind the bite plane, if this happened it would be very traumatic for the lowers & overtime they would become retroclined
FPBP
flat posterior bite plane
will disengage the bite allowing teeth to move forwards into an anterior crossbite
if FPBP was not present the active component pushing an anterior upper forward may not be able to because a lower tooth could potentially be preventing movement
while using FPBP anteriors will not overerupt as posterior teeth would while using a FABP, they may however continue to erupt to their normal level as this may previously have been prevented
Z spring
in 0.5 HSSW
may be used to rotate teeth, one of the few components of a URA that can actually produce a non-tipping movement
depending on amount that each coil is turned, will cause different levels of rotational movement in tooth
buccal canine retractors
0.5 HSSW
tubing placed on parts of the BCR to give component stability & rigidity in the buccal sulcus
this means it will not be the part of the component that moves actively but the non tubing covered areas will be active
mid palatal screw
will expand upper arch on both the left and right hand side
can be used to relieve crowding & to correct a posterior crossbite
screw itself is turned 1-2 x weekly & each turn is equivalent to 1/4mm movement which allows for 1mm of movement / month
FPBP must be used alongside this to allow lowers to ‘slide’ along uppers
when fitting an appliance
- check appliance is correct for ptx
- check design & prescription sheet correct for ptx
- check integrity - look for work hardening / any fractures
- check for any sharp or protruding edges of appliance on fit / design surfaces
- insert appliance
- check for any blanching or trauma to mucosa and if it is comfortable
- check flyover of adam’s clasp - is it too high & interfering with occlusion as this can lead to fatigue & fracture, may also dislodge or distort component, can push arrowhead into gingivae
- check arrowhead of adam’s clasp - is it engaging undercut?
- check anterior retention
- activate appliance
- teach ptx how to insert & remove appliance and get them to demonstrate it back to you
- recall ptx in 4-6wks
after advice to give ptx for URA
- may feel discomfort but should wear 24/7, explain this is just the appliance working & moving the teeth & they will get used to it
- explain it may feel very big to begin with
- advise them they may get a lisp but should practice reading a book aloud at home & they will get used to it
- may have excess saliva but this will reside within 24hrs
- if they don’t wear all the time the treatment will take longer
- should remove after eating to clean & remove for contact sports
- avoid hard, sticky & sugary foods
- caution when eating hot food & hot drinks as appliance will be a poor conductor of heat
- provide emergency contact if there are any issues
fixed appliance
any appliance attached to teeth by bands or bonds and brackets and which moves teeth by means of the brackets & their attachment on the bands (or bonds), this appliance cannot be removed by ptx
adv of fixed appliance
- compliance
- less invasive
- can move teeth all at once
- can bodily move teeth through bone
disadv of fixed appliance
- OH is poorer
- root resorption
- trauma to soft tissues
- if it breaks it cannot be removed by ptx
- significantly more expensive
- more difficult to control anchorage
- will slightly damage tooth
main risks of ortho tx
- decalcification
- relapse
- root resorption
others inc - tooth wear, enamel #, loss of vitality, loss of periodontal support, soft tissue trauma, allergy, poor/failed tx
uses of study casts
- diagnosis
- education
- research
- ptx motivation
- ptx records
- tx planning
- audit
constituents of stainless steel
72% iron - combined with carbon becomes steel
18% chromium - lowers content of carbon allowing martensite to form at a lower temp & allows for passive oxide layer improving corrosion resistance
8% nickel - with chromium allows for martensite formation, also improves corrosion resistance
1.7% titanium - inhibits precipitation of chromium carbides at grain boundaries when the alloy is heated; this improves strength
0.3% carbon - combined with iron becomes steel
