Class 3 Flashcards
What is the prevelence of class 3 malocclusion?
3%
What is a class 3 incisor relationship?
Lower edge of the incisor occluded anterior to the clingulum plateau of the upper incisors
What are the broad causes of class 3?
Skeletal
Soft tissue
Occlusal and dento alveolar
Facial growth
What are the skeletal causes of class 3?
AP: usually class 3: large mandible, small maxilla or both and short anterior cranial base
Vertical: can be average increased or decreases
Transverse: narrow upper arch, broad lower arch
What are the soft tissue causes of class 3?
Not usually a cause but leads to dento alveolar compensation
What is the UIA in a class 3 and how does this compare to the average size?
Class 3: 118
Normal: 109
What is the LIA in a class 3 and how does this compare to the average size?
Class 3: 89/79
Normal 93
What are the occlusal features of class 3? And what can its lead to?
Anterior cross bite due to class 3 incisor Posterior cross bite due to arch width discrepancy and also the larger parts of the mandible occlude with the smaller parts of the maxilla
Wear on labial upper incisors and recession on lower
Crowded upper arch and spaced or aligned lower
Can lead to mandib displacement
T/F It is not possible to compensate for adverse growth in class 3 compared to class 2?
T
Where is there more bone, behind the upper incisors or in front?
Behind
Why do we treat class 3 later than earlier?
It is not possible to predict growth for that individual and must assume that their growth will be average. Best to not treat until they stop growing
In which case do you treat early?
Mild class 3 with mandibular displacement
Why do you treat mild class 3 early?
May cause damage to the periodontium and it is quick and easy to treat and thus if the later growth is unfavourable then not much has been lost
How do you treat a mild class 3?
Procline upper incisors with URA
How do you treat a moderate class 3?
Procline uppers and retroclined lowers with FA
How do you treat a severe class 3?
Orthognathic
What factors would indicate treatment is likely to be successful?
NALM
Normal or increased overbite
Anterior mandib displacement
Little or no DA compensation
Mild class 3 pattern
With Moderate class 3 when would you treat them?
Treat them later rather than earlier to avoid uncertainty from future growth
What does a forward ,anterior displacement suggest?
- It is a tooth related cause
2. Some of the correction will arise from the condyles dropping back into the fossa
When do you treat severe class 3?
Once growth stopped since needs surgery
What would be the purse of ortho in severe class 3?
Decompensate the incisors and co ordinate arches
What surgery would be done to the mandible ?
Bilateral Sagittal split
What surgery would be done to the maxilla ?
Le Fort 1 osteotomy
