Orthdontics Flashcards
prevalence of hypodontia
approx 6%
prevalence of hypodontia in primary dentition
0.9%
hypodontia - most commonly affected teeth
upper lateral incisors - most common
also
- lower incisors
- upper 5s
- lower 5s
hypodontia - potential problems
spacing
drifting
over-eruption
aesthetic impairment
functional problems
hypodontia - special investigations
study models
planning models
radiographs
photographs
CBCT
ideal abutment for a RBB to replace a missing lateral incisor and why?
Canine
- root length
- crown dimensions
- less shine-through
syndromes linked to hypodontia
cleft lip and palate
ectodermal dysplasia
MDT specialists that may be involved in hypodontia cases
orthodontics
paediatrics
oral surgery
restorative
OMFS
Definition of AP skeletal class 1
maxilla is 2-3mm in front of the mandible
gives 2 ways of assessing the AP skeletal base
visual assessment
palpate skeletal bases
how can the skeletal base be assessed in a vertical plane? give the average values
FMPA
- 27 degrees +/-4
LAfH:TAFH
- 55%
What are the occlusal features of a sucking habit?
proclination of upper incisors
retorclination of lower incisors
localised anterior open bite or incomplete overbite
narrow upper arch
- +/- unilateral posterior crossbite
Special investigations that can be done to assess the position of an unerupted maxillary canine
OPT and anterior maxillary occlusal
2x periapicals
- one centred on canine region
- one centred on upper central incisor
- parallax technique to localise canine
CBCT
ectopic canine incidence
1 to 2% in Caucasian population
risks of leaving an ectopic canine unerupted
resorption of roots of adjacent teeth
- 40% risk of lateral incisor root resorption
resorption of canine crown
- 14% risk
ankylosis of unerupted canine
eventual loss of primary canine and complex restorative solutions may be required in future
cystic change of canine (rare)
Ectopic canine - treatment options
accept malcolussion
consider interceptive extraction of the C
surgical exposure and orthodontic alignment
surgical removal of ectopic canine
autotransplantation
special investigations for assessing an unerupted maxillary incisor
anterior occlusal maxilla or pericapicals
- +/- OPT
CBCT
potential factors leading to an unerupted maxillary incisor
trauma to primary tooth causing dilaceration of permanent tooth
early loss of primary tooth allowing adjacent teeth to drift resulting in a crowding = prevention of eruption
unerupted upper central incisor - treatment options
accept malocclusion (not advised)
bring central incisor into line of arch
- URA or fixed appliance to make space for tooth
- surgical exposure - often closed exposure
surgically remove central incisor
Class 2 div 1 malocclusion - give BSI definition
- the lower incisor edges lie posterior to the cingulum plateau of the upper incisors
- there is an increased overjet
- the upper central incisors are proclined or of average inclination
class 2 div 1 incisor relationship prevalence
15-20%
Reasons for treating a class 2 div 1
aesthetic concerns
dental health concerns
- prominent incisors at risk from trauma especially if incompetent lips
- >9mm overjet twice as likely to suffer trauma
- >9mm overjet IOTN (dhc) = 5a
Class 2 div 1 dental features
increased overjet
overbite varies
can see good alignment, crowding or spacing
habitually parted lips may lead to drying of gingiva and exacerbation of any pre-existing gingivitis
management options for class 2 div 1 malocclusion
accept
attempt growth modification
simple tipping of teeth (URA)
camouflage
orthognathic surgery
types of functional appliance for class 2 div 1
removable
tooth borne
- twin block
- activator/bionator
soft tissue borne
- Frankel (FR II)
fixed
- Herbst
functional appliances - effect in class 2 div 1
mostly dento-alveolar changes
- distal movement upper dentition
mesial movement lower dentition
- retroclination of upper incisors
- proclination of lower incisors
minor degree of skeletal changes
- RCT’s indicate that degree of maxillary restraint and mandibular growth is usually small - 1-2mm
- significant variation in response
early functional appliance treatment - potential benefits
improve appearance earlier
- potential psychological benefit
- reduce risk of trauma
- often better compliance with appliance wear
potential disadvantages of early use of a functional appliance
early skeletal effects not maintained in long term
overall treatment time increased - 2 phase treatment
- early functional appliance plus retention
- fixed appliances in early permanent dentition
research shows little if any difference in results between those treated early and those who waited until in permanent dentition
orthognathic surgery indications
growth complete
severe skeletal discrepancy in A/P or vertical direction
Class 3 incisor relationship BSI definition
lower incisors edges occlude anterior to the cingulum plateau of the upper central incisors
overjet is reduced or reversed
Class 3 incisor relationship - incidence
uk 3-7%
higher incidence in Asia
Class iii aetiology
strong genetic link
- Habsburg family
environmental factors
- cleft lip and palate
acromegaly
Class 3 dental features
tendency to reverse overjet
class 3 molar relationship (not always)
reduced overbite
- anterior open bite may be present
crossbites
- anterior
- buccal
alignment
- mandible often aligned or spaced
- maxilla often crowded
dentoalveolar compensation
- proclined upper incisors
- retroclined lower incisors
tendency for displacement on closing
Reasons for treating a class 3
aesthetics
- dental
- profile concerns
dental health reasons
- attrition
- gingival recession
- mandibular displacement
function
- speech
- mastication
Factors which affect the difficulty of treating a class 3 malocclusion
number of teeth in anterior cross bite
skeletal element in aetiology
the degree of ap discrepancy
presence of an anterior open bite
Why does facial growth make treating a class 3 malocclusion more difficult?
tends to be unfavourable
- mandibular growth continues for longer
- potential for class 3 to become worse
class 3 growth modification appliances - give examples
functional appliances
- chin cup
- reverse twin block
- Frankel III
protraction headgear +/- rapid maxillary expansion
bollard implants (late mixed and permanent dentition)
Orthodontic camouflage for class 3 - indications
growth stopped
mild to moderate class 3
- ANB >0 degrees
average or increased overbite
able to reach edge to edge incisor relationship
little or no dentoalveolar compensation
class 3 orthodontic camouflage extraction pattern
extract further back in upper arch
extract further forward in lower arch
classic pattern
upper 5s, lower 4s
not always possible as dental health may dictate extraction pattern
GDP role in treatment for class 3
identify class iii malocclusion
refer to hospital service or specialist practitioner
URA treatment
- anterior crossbite correction
give the BSI definition for a Class II division II incisor relationship
lower incisors occlude posterior to the cingulum plateau of the upper incisors
the upper incisors are retroclined
the overjet is reduced but can also be increased
class 2 div 2 incidence
5-18%
class 2 div 2 dental features
retrolination of upper central incisors
retroclined lower incisors
upper 2s often crowded
- may be normal or prolcined depending on position relative to lip line
reduced arch length
- exacerbates crowding
lateral incisors = poor cingulum
lower incisors may occlude with upper incisors or palatal mucosa
deep overbite
class 2 buccal segments
overjet usually reduced
incidence of developmental dental anomalies in class 2 div 2 patients
50% cases have a form of congenital dental anomaly
33% have impacted canine
reasons for treating class 2 div 2
aesthetic concerns
dental health concerns
- traumatic overbite
- IOTN DHC 4f
Examples of functional appliances for class 2 div 2
modified twin block
springs or screw
upper sectional fixed appliance
Aim of fixed appliances in class 2 div 2
overbite reduction
correction of inter incisal angle
- torque
Orthodontics - how may it differ in adults compared to children (factors to consider)
lack of growth
- adults non growing
- growth modification not possible
- overbite correction more difficult
- mid palatal suture closed
periodontal disease
missing/heavily restored teeth
physiological factors
- decreased cell turnover, initial movement may be slower
adult motivation
Why do adults seek orthodontic treatment?
improve dental appearance
- refused treatment as a child
- lack of earlier opportunities
- unhappy with result of earlier treatment e.g. relapse
adjunctive
- facilitate restorative treatment
- after periodontal drift
- part of surgical correction of jaw discrepancy
benefits of orthodontics
improvement in
appearance
- dental
- facial
function
dental health
MOCDO acronym stands for
Missing teeth
Overjet
crossbites
Displacement of contact point
Overbites
impacted teeth - potential consequences
can cause resorption
supernumerary teeth can prevent normal eruption
can be associated with cyst formation
overjet >6mm - potential consequence
risk of trauma to upper incisors increased
- worse with incompetent lips
Anterior crossbite - consequence
loss of periodontal support
tooth wear
posterior crossbite - consequence
significant displacement may lead to asymmetry
- must be corrected early
deep traumatic overbite - consequences
can cause gingival stripping
loss of periodontal support
Risks of orthodontic treatment
main ones
decalcification
root resorption
relapse
soft tissue trauma
others
recession
loss of periodontal support
enamel fracture and tooth wear
loss of vitality
allergy
poor/failed treatment
headgear injuries
how to prevent decalcification
good case selection
- motivated patient
- good OH pre treatment
- low caries risk
oral hygiene
diet advice
fluoride
Oral hygiene instruction for ortho patients should include:
before start and during
- toothbrushing - target areas
- interdental brushing
- brushing minimum twice per day
- target gingival margins and around each bracket
- disclosing tablets
diet advice for ortho patient
encourage a low cariogenic diet
sugar amount and frequency
- avoid snacks between meal
- avoid fizzy drinks etc
- sports drinks
- lollipops etc
sugar free gum
- stimulates salivary buffers
define the term ‘relapse’ in relation to orthodontic treatment
the return of the features of the original malocclusion following correction
which teeth and cases are particularly prone to relapse following orthodontic treatment?
lower incisors
crowding
rotations
instanding laterals
downsides of fixed retainers
prone to plaque and calculus build up
can break without patient noticing
requires excellent OH
requires more care/long term maintenance
What special investigations can be undertaken following an orthodontic assessment?
- OPT
- Vitality tests
- Study models
- Photographs
Orthodontic assessment - things to check for lower arch
- degree of crowding
- presence of rotations
- inclination of canines
- angulation of incisors to mandibular plane
Orthodontic assessment - things to check for upper arch
- degree of crowding
- presence of rotations
- inclination of canines
- angulation of incisors to Frankfort plane
What score is used to assess the treatment need for a patient in orthodontics?
IOTN
What is the SNA?
-sella-nasion A point angle
-relates the maxilla to anterior cranial base
avg value 81 +/- 3 degrees
What is the SNB?
-Sella-nasion B point angle
-relates the mandible to the anterior cranial base
avg value 78 +/- 3 degrees
What is the ANB
- A-point-nasion B-point angle
- relates the mandible to maxilla
avg value 3 degrees +/- 2
What are the typical cephalometrics of a class II occlusion?
- SNA usually average
- SNB usually decreased
- ANB> 5 degrees
outline the typical cephalometrics of a class III occlusion
- expect SNA to be decreased
- SNB often average
- ANB <1 degrees or negative
What are the borders for the upper and lower anterior face heights?
Upper anterior face height
- brow ridge to base of nose
Lower anterior face height
- base of nose to inferior aspect of chin
What are the planes looked at when assessing the vertical jaw relationship?
Frankfort plane
- lower orbital rim to superior border of external auditory meatus
Mandibular plane
- lower border of mandible
What are the typical features of a short facial type?
- LAFH to TAFH <55%
- FMPA < 23 degrees
- deep overbite tendency
- tendency to parallelism of jaws
What is the prevalence of malocclusion?
68%
What is meant by a ‘local’ cause of malocclusion?
a localised problem or abnormality within either arch, usually confined to one, two or several teeth producing a malocclusion.
- tend to get worse with time
Give some examples of local causes of malocclusion
- variation in tooth number
- variation in tooth size or form
- abnormalities of tooth position
- local abnormalities of soft tissues
- local pathology
What is a supernumerary tooth?
- a tooth or tooth-like entity which is additional to the normal series
- most common in anterior maxilla
- more common in males
what is the prevalence of a supernumerary tooth?
- 1% in primary dentition
- 2% in permanent dentition
What is an ectopic tooth?
A tooth that is not located at the dental arch
How to do you check for an ectopic maxillary canine?
- check for palpable buccal canine bulge from age 9 onwards
Factors causing a variation in tooth number
- supernumerary teeth
- hypodontia
- retained primary teeth
- early loss of primary teeth
- unscheduled loss of permanent teeth
Why might a primary tooth be retained?
absent successor
ectopic or dilacerated successor
ankylosed primary molars
dentally delayed in terms of development
pathology/supernumerary
early loss of primary teeth - possible causes
trauma
periapical pathology
caries
resorption by successor
Balancing extraction - what does this mean?
- extracting a tooth from the opposite side of the same arch
- in order to minimise midline shift
compensating extraction - what does this mean?
- extracting a tooth from the same side of the opposing arch
- in order to maintain occlusal relationship
early loss of canines - management
- consider balancing extraction
- early loss in crowded arch can give centre line shift
- some mesial drift of buccal segments
Factors influencing impact of loss of 6s
age at loss
degree of crowding
malocclusion
unscheduled loss of upper permeant central incisors - management
- ideally maintain space
- re implant
- simple denture
definitive prosthesis to deal with space long term
What are the types of orthodontic tooth movement?
- tipping
- bodily movement
- extrusion
- intrusion
- rotation
- torque
What effects do excessive orthodontic forces have on a tooth?
- pain
- necrosis
- root resorption
- anchorage loss
- possible loss of tooth vitality
What factors affect the response a tooth may have to an orthodontic force?
- magnitude
- duration
- age
- anatomy
types of orthodontic appliances
- removable (URA)
- functionals
- fixed
what are the dentoalveolar changes from use of twin block functional appliances?
- mesial migration of lower teeth
- distal migration of upper teeth
- retroclination of upper teeth
- proclination of lower teeth
ARAB - what does this acronym stand for?
Active component
Retention
Anchorage
Baseplate
Types of forces which could displace a URA
- gravity
- occlusal
- masticatory
- active component
Anchorage - define
the resistance to unwanted tooth movement
(URA precription ) Retentive component for anterior teeth + gauge of wire
Southend clap, 0.7mm HSSW
retentive component used for posterior teeth + gauge of wire
Adams claps, 0.7mm HSSW
Baseplate is made out of…
self cure PMMA
Baseplate modification to treat an overbite
Flat anterior bite plane, Overjet + 3mm
Advantages of removable appliances
- tipping of teeth
- excellent anchorage
- generally cheaper than fixed
- shorter chair side time required
- OH easier to maintain
- non-destructive to tooth surface
- less specialised training required to manage
- can be easily adapted for overbite reduction
- can achieve block movements
disadvantages of removable appliances
- less precise control of tooth movement - only tipping
- can be easily removed by patient
- only 1-2 teeth can be moved at one time
- specialist technical staff required to construct appliances
- rotations can be difficult to correct
information to give patient following delivery of a URA
appliance will feel big and bulky
- will get used to it, perfectly normal
may cause initial salivation
- will pass in 24 hours
may impinge on speech
- practice reading aloud
to be worn 24/7 including meal times and sleep
remove after every meal and clean with a soft brush
remove and store in protective container when participating in contact or active sports
avoid hard or sticky foods - be wary with hot food and drinks
missing appointments and non-compliance will significantly increase treatment time
emergency contact details
Write a prescription for a URA to expand the upper arch
Active component - midline palatal screw
retention - 16 + 26: Adam’s clasps: 0.7 HSSW
14 + 24; Adam’s clasps; 0.7mm HSSW
anchorage - reciprocal anchorage
baseplate - self cure PMMA
what would you use to reduce a 6mm overjet in a URA?
22, 21, 11, 12; Roberts retractor; 0.5mm HSSW + 0.5mm ID tubing
stops; 13 + 23 mesial stops; 0.7mm (flattened) HSSW
What active component would you use to retract a buccally placed canine?
Buccal canine retractor; 0.5mm HSSW and 0.5mm ID tubing
causes of unerupted central incisors
supernumeraries
trauma to primary tooth
- dilaceration to permanent tooth
other pathology or developmental anomaly
congenital absence - rare
what is meant by the term ‘dilaceration?
An abnormal bend in the root or crown of a tooth, caused by trauma or developmental disturbances
first molar extraction - most ideal time to extract
- 7s bifurcation calcifying
- 8s present
- mesial angulation of lower permanent molar
- class 1/reduced overbite
- moderate lower crowding
- mild/moderate upper crowding
anterior cross bite - things to assess clinically
displacement
mobility of lower incisor
tooth wear
gingival recession
Give examples of habit breaker appliances
URA with palatal goal posts
Fixed appliance with tongue rake
Infra occluding teeth aetiology
ankylosis of primary tooth
surrounding alveolar bone continues to grow
primary tooth gets left behind
8 signs pt is wearing URA
wearing on entering
speech with appliance in
proficient handling
good fit
worn appearance of acrylic
indentations on palatal mucosa
signs of tooth movement
active component passive
absence of excess salivation
How is cleft lip and palate classified?
LAHSHAL
Lip
Alveolus
Hard Palate
Soft palate
Start from classifying from right
- use a dash for any part that is unaffected
Cleft lip and palate aetiology
genetic
- syndromes
- family history
environmental
- social deprivation
- smoking
- alcohol
- anti-epileptics
What MDT specialities may be involved in cleft cases
Speech
Hearing and airway
Cardiac
ENT
dental team
CNS
psychology
Cleft lip and palate patient journey
3 months = lip closure
6-12 months = palate closure
8-10 years = alveolar bone graft
12-15 years = definitive orthodontics
18-20 years = orthognathic surgery
Why does a cleft patient need to be at least 8 years old before carrying out alveolar bone grafting?
if done earlier - risk of damaging tooth buds in alveolus or creating a fistula
Cleft lip and palate dental implications
missing teeth
- most commonly lateral incisor
impacted teeth
crowding
growth
- 20% have skeletal class III
caries
Lateral Cephalohgrams - uses
gross inspection
- anatomy/pathology
assess dent-skeletal relationships
assess soft tissue relationships to underlying hard tissues
monitoring facial growth
prognosis and treatment planning
predict future growth
assess changes due to treatment and growth
Lateral cephalogram indications
to aid diagnosis
pretreteamnet record
monitoring progress
research project
Limitations of lateral cephalograms
radiographic projection errors
- magnification
- distortion
errors within measuring system
errors in landmark identification
- quality of image
- operator procedure
- landmark definition and location
What is interceptive orthodontics?
any procedure that will reduce or eliminate the severity of a developing malocclusion
primary dentition - occlusal features
incisors more upright
spaced - presence of anthropoid spaces and may present with generalised spacing
tooth wear
- incisors after a period of time may tend towards edge to edge
Additional space is required to accommodate the larger teeth of the permanent dentition. How is the space gained?
- increase in inter canine width through lateral growth of the jaws
- upper incisors erupting onto a wider arc
- primary canines moving back into the anthropoid spaces (mandible)
- the leeway space
leeway space in the upper arch
((primary canine + first + second molar) - (permanent canine+ first premolar and second premolar))=
1 to 1.5mm
leeway space in lower arch
((primary canine + first molar + second molar) - (permanent canine + first premolar + second premolar))
2 to 2.5mm
general rules for extracting a poor prognosis first permanent molars
if extracting lower, extract upper
don’t balance with sound tooth
don’t balance if well aligned or paced
if extracting upper, lower does not need to be extracted
extraction of first permanent molar - most ideal result is gained when…
7s bifurcation calcifying
8s present
moderate lower crowding
mild/moderate upper crowding
best age typically 8-9 years
infra occluding tooth management if successor is present
monitor 6-12 months
extract if primary tooth below inter proximal contact point
consider extraction if root formation of successor is near completion
maintain space if tooth extracted
risks of doing nothing to an infra occluding tooth, if successor is present
permanent successor could become more ectopic
infra occlusion worsens with tipping of adjacent teeth
- primary tooth becomes inaccessible for extraction
caries
periodontal disease
management of an infra occluding tooth - if permanent successor is absent
depends on
- degree of crowding
- degree of infra-occlusion
- malocclusion
retain primary if in good condition and consider onlay
extract if below interproximal contact point
- maintain space for prosthesis
- close space
- or reduce space
Growth modification in Class III is most successful when:
skeletal I or only mild class III
average or reduced face height
patient age 8-10
(must be worn 14+ hours a day)
Primary tooth eruption sequence
a-b-d-c-e
lowers before uppers
6 months - 2.5 years
primary central incisors usually erupt between
6-7 months
primary lateral incisors usually erupt between…
7-8 months
primary canines usually erupt between…
18-20 months
primary first molars usually erupt between….
12-15 months
primary second molars usually erupt between….
24-36 months
How much spacing is required in the primary dentition to guarantee no crowding?
> 6mm
What percentage of 6 year olds have a diastema?
96%
what percentage of 12 year olds have a diastema?
7%
diastemas will typically close if they are narrower than…
2.5mm
impaction of first permanent molar - management options
if patient <7 years wait 6 months
- 90% of cases self-correct
orthodontic separator
attempt to distilise first molar
extract E
distal disking of ‘e’
Describe Andrew’s 6 keys
Class 1 molar relationship
correct crown angulation
- long axis of the teeth have a slight mesial inclination except for lower incisors
correct crown inclination
- crowns of the canines back to molars have a lingual inclination
no rotations
no spaces
flat occlusal planes or slight curve of spee
benefits of fixed appliances
3d control
complex tooth movements
control of root
less dependent on compliance
downsides of fixed appliances
requires excellent oral hygiene
risk of iatrogenic damage
poor intrinsic anchorage
components of fixed appliances
bracket/tube
band
arch wire
auxiliaries
anchorage components
force generating components
orthodontic brackets can be made of…
metal
- stainless steel
- CoCr
- Ti
- Au
polymers
ceramics
How are brackets and tubes bonded to teeth?
composite via acid etch technique
how are molar bands bonded to teeth?
glass ionomer
Archwires can be made of
stainless steel
nickel titanium
cobalt chromium
beta-titanium
composite/glass
properties of nickel titanium arch wire
flexible
light continuous force
shape memory
- returns to original shape
- cannot bend
higher friction than stainless steel
properties of stainless steel arch wire
working arch wire to slide teeth
- low friction
formable
- arch wire bends
- loops
give an example of force generating components in fixed appliances
sliding mechanics
- Elastic power chain
- NiTi coils
- intra-oral elastics
- active ligature
teeth move by utilising the energy stored in the elastic spring
what do intra oral elastics for class 3 do?
retrocline lower incisors
procline upper incisors
mesial movement of upper teeth
distal movement of lower teeth
extrusion of upper molars
what do intra oral elastics for class 2 do?
Retrocline upper incisors
procline lower incisors
extrusion of lower molars
distal movement of upper teeth
mesial movement of lower teeth
What are the different types of anchorage?
simple
compound
reciprocal
Components which can be used for anchorage in fixed appliances
temporary anchorage devces
- non osseointergrating mini screw
- inter-radicular TAD
- palatal TAD
cortical plates
- cortical anchorage
- maintains intermolar width
nance palatal arch
inter maxillary anchorage
- Class III elastics
- Class II elastics
malocclusion features with high relapse potential
diastema
rotations
palatally ectopic canines
proclination of lower incisors
anterior open bite
instanding upper laterals
types of removable retainer
pressure formed
Hawley
How can enamel wear occur from fixed appliances?
from opposing brackets
higher risk with ceramic brackets
