what % of people exhibit a Class I occlusion with no orthodontic problems?
what % of people have a Class I occlusion but have malopposed teeth/rotation/crowding?
what % of people have a class II occlusion?
25% - lower molar distally positioned
what % of people have a class III occlusion?
<1% - lower molar mesially positioned
what 3 planes are viewed to look at malocclusion
what % of americans exhibit malocclusion?
list 2 characteristics of crowding
1. increases with age
2. more common in mandibular
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
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
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)
list 3 specific causes of malocclusion
2. skeletal growth disturbances
3. muscle dysfunction
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)
what % of malocclusion is attributed to hereditary factors?
which type of development, skeletal or dental, has more of a familial correlation?
how does age relate to skeletal and dental estimates?
increase in age = increase in skeletal inheritance estimates; decrease in dental inheritance estimates
how does chewing pressure affect arch size?
increase use of jaws/increase biting force = increase dimension of jaws/dental arch
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
skeletal traits are influenced by? dental traits are influenced by?
list the ages of when permanent mandibular canine, lateral, centrals, first and second molars erupt
Central Incisors/1st Molars: 6
Lateral Incisors: 7
2nd Molars: 12
List the ages of when permanent maxillary canine, lateral, central, 1st and 2nd molars erupt
1st Molar: 6
Canines/2nd Molars: 12
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.