Aetiology of Malocclusion

Question 1

Malocclusion

Answer 1

Appreciable deviation from the ideal occlusion that may be considered aesthetically or functionally unsatisfactory

Question 2

Aetiology of Malocclusion

Answer 2

skeletal pattern
space deficiency
local factors
soft tissues

Question 3

General factors of malocclusion

Answer 3

Skeletal relationship
Tooth/Arch size disproportion
Soft tissues - macroglossia
Genetic and developmental disorders
TMJ Trauma/Growth abnormalities

Question 4

Local factors of malocclusion

Answer 4

Early loss/prolonged retention of deciduous teeth
ectopic teeth
absent teeth/supernumeraries
impaction/delayed eruption
local pathology

Question 5

GF: Skeletal F

Answer 5

Genetic control

Question 6

GF: T & A size

Answer 6

Relatively small arches cause crowding
Large teeth may cause crowding

Question 7

GF: Soft Tissues

Answer 7

Tongue posture and size: AOB/CP
Lip form and function

Question 8

GF: Genetic and Developmental disorders

Answer 8

CLP: Surgical scarring (class III, crossbites), supernumeraries
Achondroplasia: disorder resulting in decreased skeletal growth
Acromegaly: endocrine problem leading to increased mandibular growth

Question 9

Early loss of deciduous teeth effects depend on:

Answer 9

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

Question 10

Prolonged retention of deciduous teeth

Answer 10

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)

Question 11

Developmental absence of permanent teeth (Hypodontia)

Answer 11

2-3%
excludes 8s
severe hypodontia = 6 or more teeth missing

Question 12

Hypodontia tx

Answer 12

Space closure
open or maintain space then bridgework
accept

Question 13

Hypodontia upper laterals

Answer 13

Common 2-3%
Associated with ectopic canines and small contralateral lateral incisors

Question 14

Hypodontia lateral incisors tx

Answer 14

Space closure
Bridgework
Need fixed appliances

Question 15

Absent second molars

Answer 15

2%
Appear on radiographs as late as 8yrs

Question 16

Absent second molars tx

Answer 16

Space closure
Bridgework
Use space to tx crowding
accept and retain Es
Prognosis of Es uncertain, unusual to last beyond 30yrs

Question 17

Absent lower central incisors

Answer 17

Rare
Tx space closure or bridgework

Question 18

Supernumerary teeth

Answer 18

1-2%
80% are anterior maxilla
Morphology and Position used for classifications
Clinical effects include delayed eruption of teeth, crowding and midline diastema

Question 19

Supernumerary teeth tx

Answer 19

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

Question 20

Impacted teeth

Answer 20

1st molars
Premolars 3rd molars

Question 21

1st molars

Answer 21

3-4%
maxilla
2/3 correct spontaneously
require extraction of E and simple URA to disimpact

Question 22

Premolars

Answer 22

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)

Question 23

Ectopic maxillary canines

Answer 23

2% incidence

Question 24

Labial fraenum

Answer 24

Abnormally thick upper labial fraenum
Sometimes associated with midline diastema
Wait until upper canines erupted before tx
Fraenectomy during or after space closure

Question 25

Early loss of permanent teeth

Answer 25

1st molars (caries) Upper incisors (trauma)

Question 26

Early loss of 1st permanent molars

Answer 26

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

Question 27

Management of carious 1st molars

Answer 27

Extraction best age 8-9 yrs, if 6s are of poor prognosis at this age then consider extraction later extraction --> tipping

Question 28

Lower 3rd molars

Answer 28

very weak association with lower incisor crowding late lower incisor crowding alone is not an indication for lower 3rd molar extraction

Question 29

Early loss of permanent upper incisors

Answer 29

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

Question 30

Abnormal tooth form

Answer 30

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