Aetiology of Malocclusion Flashcards
Aetiology of malocclusion?
Skeletal pattern (relationship of maxilla and mandible)
Soft tissues
Dental causes
What skeletal patterns need to be considered?
Antero-posterior (class I, II, III)
Vertical
Transverse
Aetiology of class II?
Maxillary protrusion
Mandibular retrusion (main cause)
Or both?
Aetiology of class III?
Maxillary retrusion
Mandibular protrusion (main cause)
Or both
Vertical skeletal pattern - how is it analysed?
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
Increased frankfort mandibular plane angle can cause what?
Anterior open bite
Decreased frankfort mandibular plane angle can result in?
Deep bite
Transverse view (looking at pt from front) - wide lower arch or narrow upper arch causes?
Crossbite
Transverse - what causes asymmetry?
Enlargement of 1 side of face
Reduced size of one side of the face
What soft tissues should you consider?
Lips, cheeks
Tongue
Habits
Labial frenum
Where are the teeth positioned in relation to the tongue and lips? Why?
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)
What to consider with the lips?
Lip length
Lip line
Competency
What can cause a gummy smile?
Vertical maxillary excess
Define competent lips
Lips meet at rest
Define incompetent lips
Lips do not meet at rest
What are potentially competent lips?
Lips would meet if overjet reduced
What is a normal lip line?
Lower lip rests around middle of upper incisor
Low lip line?
Lower lip is below the upper incisors
High lip line? When does this occur?
Retroclined upper incisors - class 2 div 2 Lower lip rests above crowns of upper incisors
Tonge thrust due to?
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)
Soft tissue habit examples?
Dummy sucking
Digit sucking = bigger problem as continues with age
Effects of digit sucking?
Reduced overbite or anterior open bite Proclines upper incisors Retroclines lower incisors Posterior crossbite Asymmetrical open bite
What can the labial frenum cause?
Spacing = diastema
How to examine the labial frenum?
Put under tension = blanches
Can be removed surgically
