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what % of people exhibit a Class I occlusion with no orthodontic problems?
30%
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what % of people have a Class I occlusion but have malopposed teeth/rotation/crowding?
50-55%
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what % of people have a class II occlusion?
25% - lower molar distally positioned
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what % of people have a class III occlusion?
<1% - lower molar mesially positioned
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what 3 planes are viewed to look at malocclusion
- 1. sagittal
- 2. vertical
- 3. transverse
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what % of americans exhibit malocclusion?
60%
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list 2 characteristics of crowding
- 1. increases with age
- 2. more common in mandibular
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list 2 characteristics of diastemas
- 1. 26% of youth have diastemas but most self-correct
- 2. blacks are 2x more likely to have >2mm diastemas
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what racial relationships are seen in terms of Class II/III occlusions
- 1. Class II most common in whites
- 2. Class III most common in blacks, hispanics, asians
- 3. asians have highest occurance of Class III
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list 3 reasons for a need of ortho tx
- 1. psychosocial problems
- 2. oral function
- 3. injury/disease (class II max. inc. more likely to have trauma)
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list 3 specific causes of malocclusion
- 1. teratogens
- 2. skeletal growth disturbances
- 3. muscle dysfunction
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list 5 examples of muscle dysfunction
- 1. atrophy/lost of musculuature (due to motor nerve damage)
- 2. hyperfunction (results in facial asymmetry)
- 3. Muscle weakness (cerebral palsy)
- 4. acromegaly (excessive growth hormone; creates skeletal class III)
- 5. hemimandibular hypertrophy (unilateral excessive growth of mandible; more likely in girls)
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what % of malocclusion is attributed to hereditary factors?
40%
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which type of development, skeletal or dental, has more of a familial correlation?
skeletal
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how does age relate to skeletal and dental estimates?
increase in age = increase in skeletal inheritance estimates; decrease in dental inheritance estimates
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how does chewing pressure affect arch size?
increase use of jaws/increase biting force = increase dimension of jaws/dental arch
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how are chewing pressures associated with eruption?
- - long faced patients: lower biting force, teeth erupt farther
- - different biting force is more likely an effect than a cause of malocclusion
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skeletal traits are influenced by? dental traits are influenced by?
- skeletal: genetic
- dental: environmental
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list the ages of when permanent mandibular canine, lateral, centrals, first and second molars erupt
- Central Incisors/1st Molars: 6
- Lateral Incisors: 7
- Canine: 11
- 2nd Molars: 12
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List the ages of when permanent maxillary canine, lateral, central, 1st and 2nd molars erupt
- 1st Molar: 6
- Centrals: 7
- Laterals: 8
- Canines/2nd Molars: 12
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define leeway space
a space that develops due to the difference in size between permanent canine/PMs and primary canine/molars. Permanent Mandibular 1st molar moves forward into this space. allows for the formation of a class I occlusion.
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