Aetiology of Malocclusion Flashcards
Malocclusion
Appreciable deviation from the ideal occlusion that may be considered aesthetically or functionally unsatisfactory
Aetiology of Malocclusion
skeletal pattern
space deficiency
local factors
soft tissues
General factors of malocclusion
Skeletal relationship
Tooth/Arch size disproportion
Soft tissues - macroglossia
Genetic and developmental disorders
TMJ Trauma/Growth abnormalities
Local factors of malocclusion
Early loss/prolonged retention of deciduous teeth
ectopic teeth
absent teeth/supernumeraries
impaction/delayed eruption
local pathology
GF: Skeletal F
Genetic control
GF: T & A size
Relatively small arches cause crowding
Large teeth may cause crowding
GF: Soft Tissues
Tongue posture and size: AOB/CP
Lip form and function
GF: Genetic and Developmental disorders
CLP: Surgical scarring (class III, crossbites), supernumeraries
Achondroplasia: disorder resulting in decreased skeletal growth
Acromegaly: endocrine problem leading to increased mandibular growth
Early loss of deciduous teeth effects depend on:
Tooth lost e.g., D/E –> space lost as 1st molars drift mesially –> premolar crowding
Age –> effects more severe with earlier loss
Degree of crowding in arch –> more space loss with D or E loss if crowding present/greater midline shift with C loss if permanent incisors crowded
Prolonged retention of deciduous teeth
Relatively common
usually Ds or Es
may delay permanent incisor
may become submerged or infra-occluded due to ankylosis (tipping of adjacent teeth/almost all exfoliate naturally/extract only if becoming completely submerged)
Developmental absence of permanent teeth (Hypodontia)
2-3%
excludes 8s
severe hypodontia = 6 or more teeth missing
Hypodontia tx
Space closure
open or maintain space then bridgework
accept
Hypodontia upper laterals
Common 2-3%
Associated with ectopic canines and small contralateral lateral incisors
Hypodontia lateral incisors tx
Space closure
Bridgework
Need fixed appliances
Absent second molars
2%
Appear on radiographs as late as 8yrs
Absent second molars tx
Space closure
Bridgework
Use space to tx crowding
accept and retain Es
Prognosis of Es uncertain, unusual to last beyond 30yrs
Absent lower central incisors
Rare
Tx space closure or bridgework
Supernumerary teeth
1-2%
80% are anterior maxilla
Morphology and Position used for classifications
Clinical effects include delayed eruption of teeth, crowding and midline diastema
Supernumerary teeth tx
no tx
extract
exposure and alignment of teeth with delayed eruption
more than 70% of unerupted upper central incisors will erupt following removal of a supernumerary tooth
Impacted teeth
1st molars
Premolars 3rd molars
1st molars
3-4%
maxilla
2/3 correct spontaneously
require extraction of E and simple URA to disimpact
Premolars
2nd premolars
Early loss of E
Tx - extract 4 to allow eruption of 5, extract 7 and distalise 6 to create space, extract 5 (surgical)
Ectopic maxillary canines
2% incidence
Labial fraenum
Abnormally thick upper labial fraenum
Sometimes associated with midline diastema
Wait until upper canines erupted before tx
Fraenectomy during or after space closure
Early loss of permanent teeth
1st molars (caries)
Upper incisors (trauma)
Early loss of 1st permanent molars
Issues caused –> residual space/OE of opposing first molar/space is difficult to use with appliance for treating anterior crowding or overjet
Ideal age for spontaneous closure is 8-9 years
Upper spaces closure is 8-9 years
Upper spaces close better than lower
Unopposed upper 6s overerupt
midline shift with unilateral loss is minimal
Management of carious 1st molars
Extraction best age 8-9 yrs, if 6s are of poor prognosis at this age then consider extraction
later extraction –> tipping
Lower 3rd molars
very weak association with lower incisor crowding
late lower incisor crowding alone is not an indication for lower 3rd molar extraction
Early loss of permanent upper incisors
due to trauma
class II div I, poor lower lip coverage
try to save if at all possible (RCT, re-implant)
Options if lost or unsaveable –> maintain space with prosthesis. Close space orthodontically and crown lateral poor gingival margin and canine colour
Abnormal tooth form
Dilaceration of permanent upper incisors
- Root bent
- Trauma to deciduous predecessor
- Delayed or non-eruption
- orthodontic alignment
Peg shaped upper lateral incisors
- strong association with ectopic canines
- other lateral may be absent
