1 - Class 2 div 1 malocclusion Flashcards
What is the BSI definition of a class 2 div 1 malocclusion?
The lower incisor edges lie posterior to the cingulum plateau of the upper incisors, there is an increased overjet, and the upper central incisors are proclined or of average inclination
What percentage of the population have a class 2 div 1 malocclusion?
15-20%
What are the reasons for treating a class 2 div 1 malocclusion?
- aesthetic concerns
- trauma risk due to incompetent lips
Describe the skeletal patterns associated with class 2 div 1 malocclusion.
A/P
- typically class 2 skeletal base
- commonly have retrognathic mandible
- can be seen on class 1 base, if uppers +++ proclined
Vertical
- found with a range of vertical patterns
Transverse
- not associated with transverse problems
- can have narrow maxilla due to thumb sucking
What is the normal SNA value?
81 +/- 3
What is the normal SNB value?
78 +/- 3
What is the normal ANB value?
3 +/- 2
What is the normal MxP/MnP value?
27 +/- 4
What is the normal Ui/MxP value?
109 +/- 6
What is the normal Li/MnP value?
93 +/- 6
What is the SNA value?
Sella turcica to soft tissue point A
What is the SNB value?
Sella turcica to soft tissue point B
What is the ANB value?
Angle between soft tissue point A and B
What is the MxP/MnP value?
Angle between the maxillary and mandibular planes
What is the Ui/MxP value?
Angulation of upper incisors to maxillary plane
What is the Li/MnP value?
Angulation of lower incisors to mandibular plane
What is the normal LAFH/TAFH value?
55%
How do soft tissues influence class 2 div 1 malocclusion?
- lips become incompetent due to proclination of upper incisors
- lip trap can further procline the upper incisors
How is an anterior oral seal achieved with a class 2 div 1 malocclusion?
- lip to lip seal by circum-oral musculature and mandible postured forward
- lower lip drawn up behind upper incisors / tongue placed forward between incisors
- combination of above
Describe the dental features of a class 2 div 1 malocclusion.
- increased overjet
- overbite varies
- habitually parted lips leads to drying of gingiva, that can exacerbate any pre-existing gingivitis (can become hyperplastic)
What is NNSH?
Non-nutritive sucking habits
What are common NNSH?
- thumb
- fingers
- blanket
- lip
What are the occlusal features of a sucking habit?
- proclination of upper anteriors
- retroclination of lower anteriors
- localised AOB or incomplete OB
- narrow upper arch (can be seen with unilateral posterior crossbite)
Why is a narrow upper arch common in a thumb sucking habit?
Buccinator muscles are unopposed due to the tongue being held down by the thumb, the neutral zone is lost
How do you manage a patient with a NNSH?
- stop the habit (reinforcement, removable/fixed appliance breaker)
- allow spontaneous improvement (6-12 months)
- treat any residual malocclusion
What are the management option for class 2 div 1 malocclusion?
- accept
- attempt growth modification
- tipping of teeth
- camouflage
- orthognathic surgery
Describe accepting a class 2 div 1 malocclusion.
- mildly increased overjet suitable
- warn of trauma risk and advise re mouthguard
- explain that this may complicate treatment in future
How does head gear modify growth?
- restrain growth of maxilla horizontally and vertically
- works by distilising teeth rather than maxillary change (?)
Define a functional appliance.
Functional appliances utilise, eliminate, or guide the forces of muscle function, tooth eruption and growth to correct a malocclusion.
How does a twin-block function?
- mandible is postured down and forwards
- the MOM pull the mandible back, trying to achieve normal posture
- these forces pull maxillary teeth backwards
- limited mandibular growth is observed
Name other types of functional appliance that can be used in class 2 div 1 malocclusions.
- activator/bionator (tooth-borne)
- Frankel (soft tissue borne)
- Herbst (fixed)
What dento-alveolar changes can be observed after using a twin-block appliance?
- distal movement of upper dentition
- mesial movement of lower dentition
- retroclination of upper incisors
- proclination of lower incisors
When can a functional appliance be worn?
- during growth
- early use around 10 years old
- later use in late mixed dentition
When is the period of maximal growth in girls?
11-13 years
When is the period of maximal growth in boys?
13-15 years
What are the potential disadvantages of early use of a functional appliance?
- early skeletal changes may not be maintained long term
- 2 phase treatment
What are the potential benefits of early use of a functional appliance?
- improve appearance earlier (combat teasing, psychological benefit)
- reduce risk of trauma
- better compliance with wear
When can a URA be used in the treatment of increased overjets?
- v mild class 2 or class 1
- overjet is due to spaced and proclined upper incisors
- overbite is favourable
Why is URA treatment not commonly used in the management of class 2 div 1 malocclusions?
Creates a class 2 div 2 malocclusion which is not favourable
Describe the design of a URA used for retroclining upper anteriors.
A: Robert’s retractor 0.5mm in tubing
R: Adam’s clasp 16, 26 in 0.7mm HSSW
A: mesial stops on 13, 23
B: FABP
How is camouflage achieved when treating a class 2 div 1 malocclusion?
- remove teeth (not always the case, sometimes all teeth are moved distally)
- control tip of teeth with fixed appliances
When is orthognathic surgery indicated in class 2 div 1 malocclusions?
- when growth is complete
- when skeletal discrepancy is severe in AP or vertical
- fixed appliances are required before, during and after surgery
What is maxillary impaction?
Orthognathic surgery where the maxilla is raised to reduce the amount of tooth shown
QUIZ
What is the approximate prevalence of class II, division 1 malocclusion in the U.K. population?
15-20%
QUIZ
What other occlusal feature can accompany an increased overjet in patients with a digit sucking habit?
- posterior crossbite
- narrow maxillary dental arch
- retroclined lower anteriors
- anterior open bite
QUIZ
When analysing a lateral cephalograph of a patient with a class II jaw relationship, you would expect the ANB angle to measure:
Greater than 5 degrees
QUIZ
The main therapeutic effect of functional appliance treatment, in a growing child with a class II, division 1 malocclusion is:
Reduction of the overjet and correction of the molar relationship through dentoalveolar change.
