Occlusion and Malocclusion

Question 1

What is an ideal occlusion and a normal occlusion?

Answer 1

Ideal occlusion: anatomically perfect arrangement of teeth, rare
Normal occlusion: acceptable variation from ideal occlusion
- all teeth well aligned
- no crowding
- class I incisor relationship (upper incisors cover lower incisors by around 30%)
- class I molar relationship (MB cusp of upper 6 occludes with MB groove of lower 6)

Question 2

What is malocclusion and its classes?

Answer 2

Malocclusion: irregularity in the occlusion beyond accepted range of normal, not all malocclusions require treatment
Class I - overjet and overbite normal
Class II - overjet is increased
Class III - overjet is decreased or reversed meaning lower incisors ahead of upper incisors

Question 3

What are some genetic causes of malocclusion?

Answer 3

Genetic: skeletal pattern, size of jaws and teeth, syndromes e.g. cleft lip and palate

Question 4

What are the classes of skeletal pattern?

Answer 4

Class I - normal skeletal pattern, maxilla is 2-4mm ahead of mandible
Class II - maxilla is more than 4mm ahead of mandible, may be associated with class II malocclusion (increased overjet)
Class III - mandible is less than 2mm behind maxilla, may lie ahead of maxilla and can be associated with class III malocclusion

Question 5

What can be altered in skeletal pattern?

Answer 5

• transverse plane: asymmetry, two halves of face not symmetrical, can be detected by looking straight in front of the patients face
• vertical face height: lower 1/3rd of face may be increased or decreased in comparison to rest of face

Question 6

How can the size of jaws and teeth cause malocclusion? Which syndromes are relevant?

Answer 6

• crowding: big teeth, small jaws
• spacing: small teeth, large jaws
  Syndromes: cleft lip and palate, facial structures do not fuse properly in unborn foetus resulting in a cleft

Question 7

What are some environmental causes of malocclusion?

Answer 7

• soft tissues e.g. incompetent lips
• habits e.g. thumb sucking - anterior open bite
• pathology e.g. tumour applying force to teeth and move them out of alignment
• trauma e.g. intrusion

Question 8

What are some local environmental factors impacting malocclusion?

Answer 8

• additional teeth (supernumerary): may prevent eruption of normal teeth, crowding, can be surgically removed and gold chain attached to unerupted tooth
• missing teeth (hypodontia): replace with a bridge, implant or close space using using braces
• fraenum: can cause diastema
• retained primary tooth: prevents eruption of permanent tooth in correct position
• early loss of primary teeth: loss of space, crowding

Question 9

What is the IOTN?

Answer 9

IOTN - Index of Orthodontic Treatment Need
- measurement of severity of malocclusion
- considers dental health component and aesthetic component

Question 10

What is the dental health component (DHC) and what are the grades?
What is the aesthetic component?

Answer 10

DHC - looks at unerupted teeth, missing teeth, overjet, crossbite, crowding and overbite
Grade 1: no tx required
Grade 2: little tx needed
Grade 3: borderline tx need
Grade 4 and 5: treatment required
Aesthetic Component: effect on malocclusion on aesthetics, series of graded photos to score teeth, score 1 most attractive, 10 = least attractive