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
Class III malocclusion:
- Maxillary ____
- Mandibular ____
- Usually a ____ of the two conditions
- _____ dimension is variable causing a ____ to ___ bite
- maxillary retrognathism
- mandibular prognathism
- combination
- Vertical dimesnion; deep bite to open bite
- Maxillary retrognathism
- Mandibular prognathism
- Usually, a combination of the two conditions
- Vertical dimension is variable, deep bite to open bite
Class III malocclusion
Prevalence of class III malocclusion depends on:
the poplulation
List the prevalence of Class III malocclusions based on the following populations:
- Southeast Asian
- Middle Eastern
- Indian
- European
- Southeast Asian: 15%
- Middle Eastern: 10%
- Indian: 1%
- European: 1-4%
Fundamentally, mandibular growth is induced by both genetic and environmental mechanism, which interact with each other to produce:
class III phenotype
List the components involved that contribute to the mandibular growth in a class III relationship:
- genes
- environment
- condylar cartilage (acted on by genes & environment)
Fundamentally, mandibular growth is induced by:
both genetics and environmental mechanisms
What is the etiology for an open bite?
multifactorial etiologies
List some examples of the multifactorial etiology of an open bite: (4)
- Transitory
- Skeletal (genetic)
- Neuromuscular imbalance (CP)
- Combination sleep apnea
What influences the neuromuscular imbalance seen with an open bite? (2)
- oral habits
- anterior tongue posture
