Etiology of Malocclusion Part 1 Flashcards
List the predisposing factors to malocclusion:
- disturbances in embryologic development
- heredity (genetics)
- functional matrix (muscular/functional disturbances & habits)
- traumas (especially mandibular fractures)
Give an example of a functional matrix that may be a predisposing factor to malocclusion: (2)
muscular/functional disturbances & habits
What trauma specifically is a predisposing factor to malocclusions?
Mandibular fractures
What three factors contribute to malocclusion?
- genetics
- environmental
- other
What do we use for a reference point for a normal skeletal relationship?
cranial base
We use the cranial base as a reference point for no real skeletal relationship. This includesL (2)
- position & projection of the upper jaw
- position & projection of the lower jaw
Malocclusions occur in:
3 dimensions
Angle classification is based on:
AP relationships
List the relative percentages for the following:
- Normal occlusion
- Class I malocclusion
- Class II malocclusion
- Class III malocclusion
- Normal occlusion: 30%
- Class I malocclusion: 50-55%
- Class II malocclusion: 15%
- Class III malocclusion: 1-4%
According to the intuitive theory, what is the cause of a Class I?
jaw WITHOUT prognathism
According to the intuitive theory, what is the cause of a class II?
maxillary prognathism
According to the intuitive theory, what is the cause of Class III?
mandibular prognathism
Class II malocclusion:
- Mandibular _____
- 40% present _____
- Rarely ____
- Mandibular retrognathism
- Bimaxillary retrusion
- True maxillary prognathism
T/F: A class II malocclusion is most commonly caused by a true maxillary prognathism
False- that is rare- typically caused by mandibular retrognathism
What percent of class II malocclusions present with bimaxillary retrusion?
40%
- Mandibular retrognathism
- 40% present bimaxillary retrusion
- Rarely true maxillary prognathism
Class II malocclusion
Describe a typical skeletal class II: (3)
- mandibular retrognathism
- proclined upper incisors
- deep bite
Describe the typical bite for a skeletal class II:
deep bite
Describe the incisors for a typical skeletal class II:
proclined upper incisors
- Mandibular retrognathism
- Proclined upper incisors
- Deep bite
(Skeletal class?)
Typical skeletal class II
- Jaws are well aligned in the anteroposterior dimension
- Vertical and transverse dimensions are variable
Class I malocclusion
In a class I malocclusion, the jaws are well aligned in the ____ dimension, while the ____ & ___ dimensions are variable
anteroposterior; vertical & transverse
Transverse dimension involves the: (3)
- intermolar distance
- intercanine distance
- arch shape
T/F: Both the intermolar distance and inter canine distance are involved with transverse dimension
true