Etiology of Malocclusions Part 1 Flashcards
What are the predisposing factors to malocclusion?
- Disturbances in Embryologic Development
— Heredity (genetics) - Functional matrix
— Muscular or functional disturbances
— Habits - Traumas
— Especially mandibular fractures
How do you determine skeletal relationship?
- Cranial base as a reference
— Position and projection of the upper jaw
— Position and projection of the lower jaw
Malocclusion occurs in ___ dimensions
3
__% of patients have normal occlusion
30%
____% of patients have class I malocclusion
50-55%
___% of patients have class II malocclusion
15%
___% of patients have class III malocclusion
1-4%
What skeletal class is a jaw without prognathism?
class I
What skeletal class is a jaw with maxillary prognathism?
class II
What skeletal class is a jaw mandibular prognathism?
class III
What are the possible jaw positions of class II malocclusions?
- Mandibular retrognathism
- 40% present bimaxillary retrusion
- Rarely true maxillary prognathism
What does a typical skeletal class II look like?
*Mandibular retrognathism
*Proclined upper incisors
*Deep bite
How are the jaws positioned in a class I malocclusion?
- Jaws are well aligned in the anteroposterior dimension
- Vertical and transverse dimensions are variable
What distances are measured in the transverse dimension?
Intermolar distance
Intercanine distance
Should the maxillary intermolar distance be the same, greater, or lesser than on the mandibular?
the same
they should be equal
Both arches (max and mand) should have the same…
arch form/shape
What are the possible jaw positions of class II malocclusions?
- Maxillary Retrognathism
- Mandibular prognathism
- Usually, a combination of the two conditions
- Vertical dimension is variable… Deep bite to open bite
What is the prevalence of class III malocclusions by ethnicity?
Depends on the population
*Southeast Asian ~15%
*Middle eastern ~10%
*Indian ~1%
*European ~1-4%
Fundamentally, mandibular growth is induced by both _________________ mechanisms, which interact with each other to produce a Class III phenotype
genetic and environmental
What contributes to an openbite?
- Transitory
- Skeletal (genetic)
- Neuromuscular imbalance (CP)
— Oral habits
— Anterior tongue posture - Combination Sleep Apnea
