Malocclusion Flashcards
components of facial skeleton
maxillary base
mandibular base
maxillary & mandibular alveolar processes
maxillary complex is attached to anterior cranial base while the mandible articulates with the posterior cranial base
why a lateral ceph
- standardised
- reproducible - ptx positioned in a cephalostat, a set distance from the cone & film
class I ceph angles
SNA relates maxilla to anterior cranial base; av value is 81o +/- 3o
SNB relates mandible to anterior cranial base; av value is 78o +/- 3o
ANB relates mandible to maxilla; av value is 3o +/- 2o
AP class II relationship
mandible placed posteriorly relative to maxilla
mandible most commonly too small, maxilla too large or combination of both or mandible normal sized but placed too far back due to obtuse cranial base angle
AP class II ceph angles
SNA usually average but may be increased if maxilla prognathic
SNB usually decreased
ANB >5o
AP class III
mandible placed anteriorly relative to maxilla
maxilla too small most commonly, mandible too large or combination of both
normal sized jaws but mandible positioned too far forwards due to acute cranial base angle
AP class III ceph angles
expect SNA to be decreased if maxilla deficient
SNB often average but may be increased if mandible prognathic
ANB <1o or negative
definition of local cause of malocclusion
a localised problem or abnormality within either arch usually confined to 1, 2 or several teeth producing a malocclusion
tends to get worse with time
scope for interceptive tx
good to recognise early
local causes of malocclusion (5)
- variation in tooth number
- variation in tooth size or form
- abnormalities of tooth position
- local abnormalities of soft tissue
- local pathology
causes of variation in tooth number (5)
- supernumerary teeth
- hypodontia
- retained primary teeth
- early loss of primary teeth
- unscheduled loss of permanent teeth
supernumerary teeth
tooth or tooth like entity which is additional to the normal series
most common in anterior maxilla
M > F
1% primary dentition
2% permanent dentition
4 types of supernumerary teeth
- conical
- tuberculate
- supplemental
- odontome
conical supernumeraries
small, peg shaped
close to midline (mesiodens)
may erupt so xla
usually 1 or 2
tend not to prevent eruption but may displace adjacent teeth
tuberculate supernumeraries
tend not to erupt
paired
barrel shaped
usually xla
one of the main causes of failure of eruption of permanent upper incisors
supplemental supernumeraries
extra teeth of normal morphology
most often upper laterals or lower incisors
often xla; decision based on form & position
odontome supernumeraries
compound - discreet denticles
complex - disorganised mass of dentine, pulp & enamel
hypodontia
developmental absence of 1 or more teeth
F > M 3:2
4-6% population
commonly upper laterals / 2nd premolars
retained primary teeth
a disruption in sequence of eruption
a difference of >6 mths between shedding of contra lateral tooth = alarm bells, take radiograph to see what’s going on
reasons for retained primary teeth
- absent successor
- ectopic successor / dilacerated
- infra occluded (ankylosed) primary molars
- dentally delayed in terms of development
- pathology / supernumerary
what to do if absent successor
- maintain primary for as long as possible if good prognosis
- xla deciduous tooth early to encourage spontaneous space closure in crowded areas
early ortho referral for advice
infra occluded molars
process where a tooth fails to achieve or maintain its occlusal relationship with adjacent teeth
temporary ankylosis
common 1-9%
percussion sound
causes of early loss of primary teeth
- trauma
- periapical pathology
- caries
- resorption by permanent successor
balancing extraction
xla of tooth from opposite side of same arch
designed to minimise midline shift
compensating extraction
xla of tooth from opposing arch of same side
designed to maintain occlusal relationship
early loss of incisors
very little impact
no compensating or balancing
early loss of canines
unilateral loss in crowded arch give centre line shift
will get some mesial drift of buccal segments
consider balancing xla
early loss of molars
more space loss with Es > Ds
more space loss in upper > lower
6s drift mesially and steal 5s space
don’t tend to balance or compensate
unscheduled loss of 6s
routine assessment of 6s at 8-9yrs
seldom ideal tooth of choice for relief of crowding
but planned loss at correct age is better than later enforced loss
factors that influence the impact of the loss of 6s
age at loss
crowding
malocclusion
age at loss of 6s
upper - not very important
lower -
if 7s erupted (late) often poor space closure
if too early there is distal drift of 5s particularly if Es lost at same time as 6s
if crowding
upper - potential for rapid space loss
lower
spaced - will have spaces
aligned - will have spaces
crowded - best results likely
unscheduled loss of central incisor
- effect depends on timing of loss; early results in drift of adjacent teeth & late will result in long term space
- ideally maintain space so re implant or simple denture
- plan how to deal with space longer term i.e. definitive prosthesis
- if lateral incisor drifts to fill space then re open space for prosthesis or build up lateral
variation in tooth size or form
- macrodontia = too large
- microdontia = too small
- abnormal form
macrodontia
larger teeth than average
localised / generalised
problems inc:
- crowding
- asymmetry
- aesthetics
microdontia
smaller teeth than average
localised / generalised
leads to spacing
linked to hypodontia
abnormal form of teeth
peg shaped laterals
dens in dente
geminated / fused teeth
talon cusps
dilaceration
accessory cusps & ridges
ectopic teeth
most commonly
8s > upper 3s > FPM 6s > upper 1s
ectopic maxillary canines
1-3% of population and 80% palatal
check for palpable buccal canine bulge from 9yrs onwards!! further investigation i.e. PAs or refer if in doubt
ectopic canines
long path of eruption (eye teeth)
palatal canines often occur in well aligned arches
higher incidence: absent / peg shaped U laterals or class II div 2 incisor relationship
buccal canines more associated with crowding
clinical assessment of ectopic canines
- visualisation / palpation of any obvious bumps of 3
- inclination of 2
- mobility of c or 2
- colour of c or 2
radiographic assessment of ectopic canines
2 radiographs required to localise position usually OPT & upper anterior oblique occlusal
use parallax technique
3Ps = presence, position, pathology
management of ectopic canines
- prevention
- xla of c to encourage improvement in position of 3
- retain 3 and observe (accept its position)
- surgical exposure & ortho alignment
- surgical xla
- autotransplantation
ectopic first molars
<5%, commonly U arch, reversible before 8, caries risk
sign of:
crowding, mesial path of eruption, abnormal morphology of E
management:
separator, attempt to distalise 6, xla E
ectopic upper central incisors
no obvious causes
but perhaps supernumerary or trauma to primary predecessor
transpositions
interchange in position of 2 teeth
either true / pseudo
commonly:
upper canines & first premolar
lower canines & incisors
either accept, xla or correct
local abnormalities of soft tissues
- digit sucking
- fraenum
- tongue thrust
impact of digit sucking (4)
- proclined upper incisors
- retroclined lower incisors
- anterior over bite
- unilateral posterior crossbite
- due to narrow maxillary arch
- may cause mandibular displacement
local pathology causing malocclusion (3)
- caries
- cysts
- tumours
tongue thrust
can either be because of an AOB where tongue protrudes forwards to create anterior oral seal or can cause an AOB
