Etiology of Malocclusions Part `1

Question 1

What are the predisposing factors to malocclusion

Answer 1

• distrubrances in embryologic development
• heredity (genetics)
• functional matrix: muscular or functional disturbances, habits
• traumas: especially mandibular forces

Question 2

what are the main factors for malocclusions

Answer 2

genetic
- enrivonmental
- other factors

Question 3

what is measured in the normal skeletal relationship

Answer 3

• cranial base as reference
• position and projection of the upper jaw
• position and projection of the lower jaw

Question 4

malocclusions occur in ______

Answer 4

3 dimensions

Question 5

angle classification is based on _____ relationships

Answer 5

AP

Question 6

what is the prevalance/percentage is each occlusion

Answer 6

• normal:30%
• class I malocclusion: 50-55%
• class II: 15%
• class III: 1-4%

Question 7

what are the skeletal patterns (intuitive theory)

Answer 7

• maxillary prognathism: class II
• jaw without prognathism: class I
• mandibular prognathism: class III

Question 8

describe the class II maloclussion

Answer 8

• mandibular retrognathism
• 40% present bimaxillary retrusion
• rarely true maxillary prognathism

Question 9

describe a typical skeletal class II

Answer 9

• mandibular retrognathism
• proclined upper incisors
• deep bite
• however, multiple presentation are possible

Question 10

describe a class I malocclusion

Answer 10

• jaws are well aligned in the anteroposterior dimension
• vertical and transverse dimension are variable

Question 11

what is measured in the transverse dimension

Answer 11

• intermolar distance
• intercanine distance
• arch shape of the upper and lower

Question 12

describe class III maloclussion

Answer 12

• maxillary retrognathism
• mandibular prognathism
• usually a combination of the two conditions
• vertical dimension is variable - deep to open bite

Question 13

what is the prevalence of class III malocclsuions across populations

Answer 13

• southeast asian~15%
• middle eastern ~10%
• indian ~1%
• european ~1-4%

Question 14

what are the genetics of class III

Answer 14

mandibular growth is induced by both genetic and environmental mechanisms which interact with each other to produce a class III phenotype

Question 15

what are the multifactorial etiologies of the open bite

Answer 15

• transitory
• skeletal (genetic)
• neuromuscular imbalance (CP)- oral habits, anterior tongue posture
• combination sleep apnea