Class 2 Division 1 Flashcards
What is the definition of class 2 division 1
- The lower incisor edges lie posterior to the cingulum plateau of the upper incisors
- There is an increased overjet
- The upper central incisors are proclined or of average inclination
How common is class 2 division 1
Most common
What are the reasons for tx of class 2 div 1
- There are often concerns regarding the aesthetics
- There are concerns regarding dental health
What are the concerns regarding dental health
o Prominent incisors increases risk of trauma especially if they have incompetent lips as the lower lip is not present to protect them
What is the threshold measurmenet for OJ for it to fall into the high risk category
o If the overjet is >9mm then they are twice as likely to suffer trauma and hence fall into the IOTN 5a score
What can the aetiology of class 2 div 1 be divided into
- skeletal pattern
- soft tissues
- dental factors
- habits
What is the most common AP skeletal pattern associated with class 2 div 1
Class 2
possible for it to be class 1/3
How can we get a class 2 div 1 on a class 1/3 skeletal base
this can occur when the upper incisors are proclined and/or the lower incisors are retroclined either by the soft tissues or a habit or due to a buccally displaced/crowded central incisor
What is the common cause of the class 2 skeletal base
Commonly due to a retrognathic mandible but maxillary protrusion is also possible although less common
What is the vertical skeletal pattern associated with class 2 div 1
Found in association with a range of vertical skeletal patterns
The more significant the underlying skeletal discrepancy in any plane, the more difficult it is to treat
If the FMPA/LAFH is effected, are they likely to be increased or decreased
increased
Is there nay association with transvere skeletal pattern + class 2 div 1
No particular association with transverse problems
What is SNA
relates the maxilla to the anterior cranial base where A is the point at the depth of the concavity of the maxilla
What is SNB
relates the mandible position in relation to the anterior cranial base
What is ANB
SNA – SNB
What is the normal ANB
3 +/- 2 but for a class 2 div 1 we would expect the ANB to be bigger
What is the soft tissue presentation that can contribute to the malocclusion
o Lips are often incompetent due to the prominence of the incisors and/or underlying skeletal pattern
o The lower lip trap can be aetiological in the increased overjet
o If the lips are incompetent then special effort is required to create an anterior oral seal and this can be done in different ways, how the anterior oral seal is achieved effects the presentation of the class 2 division 1 incisor relationship
What arethe two ways that a class 2 div 1 w/ incompetent lips can achieve an oral seal
Lip to lip seal by activity of circum-oral musculature & mandible postured to allow lips to meet
Or
Lower lip drawn up behind upper incisors and tongue placed forwards between incisors to lower lip
Or
Combo
If lip to lip contact is not possible and the lower lip is drawn up behind the upper incisors, what can this lead to
this can retrocline the lower labial segment and/or proclined the upper incisors resulting in an incisor relationship that is more severe than the underlying skeletal pattern
If the tongue comes forawrd to contact the lower lip, what can occur
proclination of the lower incisors may occur, helping to compensate for the underlying skeletal pattern. This type of soft tissue behaviour if often associated with increased vertical skeletal proportions and/or grossly incompetent lips or a habit
What are dental factors that can contribute to the class 2 div 1
- crowding (may however have an aligned or spaced arch)
- overbite
- molar relationship
How can crowding lead to an OJ
Crowding –> due to the shortage of space, the upper incisors may be displaced labially to an overjet
Is overbite increased or reduced
Can vary, impacted by the FMPA angle
What is the most common molar relationship
Tends to be class 2 but it is possible to have a class 1 If there is space in the lower jaw resulting in mesial drift
What can the chronic open lips (incompetent) lead to
Habitually parted lips may lead to drying of the gingiva and exacerbation of any pre-existing gingivitis
What is the term for sucking habits
non-nutritive sucking habits
How can habits contribute to class 2 div 1
Proclination of upper anteriors
Retroclination of lower anteriors
Localised anterior open bite/incomplete open bite
Narrow upper arch
How does the sucking habit narrow the arch
Mandible is left slightly open leaving the buccinator unopposed which can cause the maxilla to collapse resulting in a narrower upper arch and possibly an upper posterior crossbite
What are the tx principles of habit
- reinforcement
- removable appliance habit breaker
- fixed appliance habit breaker
What is the removable appliance habit breaker
Passive URA which prevents thumb being pressed against palate
What is the fixed appliance habit breaker
Palatal arch with section of wire behind central incisors to prevent thumb from entering mouth
Why is age important in breaking habits
if the habit persists beyond 9 years old then it will be more disruptive to the occlusion because the eruptive potential of the incisors reduces at this point
Once the habit is stopped, when should we treat the malocclusion
Once habit is stopped, should allow time for spontaneous improvement and then treat the residual malocclusion if required
What are the 5 management options
- accept
- attempt growth modification
- simple tipping of teeth
- camoflauge
- orthognathic surgery
When should we accept the malocclusion
If the overjet is mild then this will result in a low IOTN score and therefore tx is not required
If there is a significant overjet but the patient is not unhappy
What should the patient be warned about in regards to accepting the malocclusion
patient should be advised of the trauma risk and possibility that treatment may be more difficult in the future
What are the two ways to attempt growth modification
- headgear
- functional appliance
What is the function of headgear
Function is to restrain growth of the maxilla horizontally and/or vertically
Does this by using the back of the head as anchorage support and force is applied to try and distalise the upper molars
Not common anymore due to social acceptability
How do functional appliances work
Utilizes, eliminates or guides the force of muscle function, tooth eruption and growth to correct a malocclusion
Used mostly for class 2 div 1
What is the aim of functional appliance
Aim is to produce restraint of maxillary growth and encourage mandibular growth
Theory is it encourages the mandible to grow as it is pulled downwards and forwards, out of the fossa stimulating muscle growth
What can then therapeutic effects be categorized into
dentoalveolar changes (main change)
skeletal changes (minor degree)
What are the dentoalveolar changes that may be done with functional appliance
o Distal movement of the upper dentition
o Mesial movement of the lower dentition
o Retroclination of the upper incisors
o Proclination of the lower incisors
Why are the skeletal changes by functional appliances debated
o Randomised controlled trials indicate that degree of maxillary restraint and mandibular growth is usually small (only 1-2mm)
o Significant variation in response
o It is hard to know whether the growth would have happened anyway without the appliance
What are the types of removeable functional appliances
tooth borne & soft tissue borne
What are the 2 tooth borne functional appliances
twin block
activator/bionator
What is the twin block
- Most widely used
- Clasps present on the upper and lower teeth with blocks in between
How does the twin block work
The blocks hold the mandible forward in a postural position bringing the teeth closer to edge to edge
What is the soft tissue born functional appliance
Frankel FRII
How does frankel FRII work
- Designed to correct class 2
- Sits into soft tissue sulcus with shields and aims to posture the mandible and expand the maxilla and effect the way the alveolar processes grow
When should functional appliances be used
- Should be used during pubertal growth spurt (ideally)
What are the two types of use of functional appliance
What age
early and later u se
When is early use done
10 YO
2 phase tx
Why is early use of functional appliance done
This is to remove the risk of trauma and risk of bullying and then second phase would be with fixed appliances once the permanent dentition is complete
What is the disadvantages of early use
Early skeletal effects from functional appliance/headgear therapy not maintained long term
Overall treatment time increased due to 2 phase treatment
* Early functional appliance + retention
* Fixed appliance in early permanent dentition
Research doesn’t show much difference between those treated early and those who waited until the permanent dentition
What are the advantages of early use
Improve appearance earlier
Reduced risk of trauma
Often better compliance with appliance wear
What is later use of functional appliance
Start with functional then move onto fixed straight away
What do we use for simpling tipping of teeth
URA
Is it common to simply tip the teeth
No
not common tx
When may a URA be prescribed for class 2 div 1
Very mild class 2/1
Overjet due to proclined and spaced incisors
Overbite is favourable
Only then after a specialist assessment has been done and treatment recommended would this be used
Write the lab prescription for the URA for class 2 div 1
Active component: Robert retractor in 0.5mm tubing
Retention: Adams crib 6/6 0.7mm HSSW
Stops mesial to 3/3
Baseplate: flat anterior biteplane
What is camouflage
No growth modification, skeletal relationship remains the same but fixed appliance used to move the teeth
How do we camouflage class 2 div 1
reduce OJ
How can we reduce the overjet in camouflage
Take out premolars to make space and then take upper canines back and the incisors
Can also extraction 7s and do distal movement of the upper 6s
Proclining lower incisors
What must a px be warned about when proclining lower incisors
risk of gingival recession as limited alveolar bone to maintain coverage
When is orthognathic surgery carried out
when growth is complete
What is the indication for orthognathic surgery
when skeletal discrepancy is severe in A/P and/or vertical direction
What jaws will be moved in orthognathic surgery for class 2 div 1
Usually involves mandibular surgery, but may also involve maxillary surgery
Usually mandibular advanced however sometimes maxilla and mandible moved forward together
When do we use fixed appliance with orthognathic surgery
Before surgery to align and coordinate dental arches
During surgery
After surgery
