Aetiology of Malocclusion

Question 1

Aetiology of malocclusion?

Answer 1

Skeletal pattern (relationship of maxilla and mandible)
Soft tissues
Dental causes

Question 2

What skeletal patterns need to be considered?

Answer 2

Antero-posterior (class I, II, III)
Vertical
Transverse

Question 3

Aetiology of class II?

Answer 3

Maxillary protrusion
Mandibular retrusion (main cause)
Or both?

Question 4

Aetiology of class III?

Answer 4

Maxillary retrusion
Mandibular protrusion (main cause)
Or both

Question 5

Vertical skeletal pattern - how is it analysed?

Answer 5

Frankfort mandibular plane (infraorbital canal to external auditory meatus)
Mandibular plane
Look at angle where frankfort and mandibular plane meet

Look at facial proportions - put face into 3 3rds
Lower border of nose to chin
Lower border of nose to top of eyebrows
Top of eyebrows to top of head

Question 6

Increased frankfort mandibular plane angle can cause what?

Answer 6

Anterior open bite

Question 7

Decreased frankfort mandibular plane angle can result in?

Answer 7

Deep bite

Question 8

Transverse view (looking at pt from front) - wide lower arch or narrow upper arch causes?

Answer 8

Crossbite

Question 9

Transverse - what causes asymmetry?

Answer 9

Enlargement of 1 side of face

Reduced size of one side of the face

Question 10

What soft tissues should you consider?

Answer 10

Lips, cheeks
Tongue
Habits
Labial frenum

Question 11

Where are the teeth positioned in relation to the tongue and lips? Why?

Answer 11

Teeth in position of stability with tongue and lips either side
5g force from lips onto upper and lower teeth each and tongue more than 5g (uppers) or 10g (lowers)

Question 12

What to consider with the lips?

Answer 12

Lip length
Lip line
Competency

Question 13

What can cause a gummy smile?

Answer 13

Vertical maxillary excess

Question 14

Define competent lips

Answer 14

Lips meet at rest

Question 15

Define incompetent lips

Answer 15

Lips do not meet at rest

Question 16

What are potentially competent lips?

Answer 16

Lips would meet if overjet reduced

Question 17

What is a normal lip line?

Answer 17

Lower lip rests around middle of upper incisor

Question 18

Low lip line?

Answer 18

Lower lip is below the upper incisors

Question 19

High lip line? When does this occur?

Answer 19

Retroclined upper incisors - class 2 div 2
Lower lip rests above crowns of upper incisors

Question 20

Tonge thrust due to?

Answer 20

Pt brings tongue forward to create a seal e.g. when anterior open bite
Adaptive = thumb sucking = tongue moves forward to correct a seal to swallow
Endogenous = associated with lisping and bimaxillary proclination (incomplete overbite/anterior open bite)

Question 21

Soft tissue habit examples?

Answer 21

Dummy sucking

Digit sucking = bigger problem as continues with age

Question 22

Effects of digit sucking?

Answer 22

Reduced overbite or anterior open bite
Proclines upper incisors
Retroclines lower incisors
Posterior crossbite
Asymmetrical open bite

Question 23

What can the labial frenum cause?

Answer 23

Spacing = diastema

Question 24

How to examine the labial frenum?

Answer 24

Put under tension = blanches

Can be removed surgically