7. Deep and Open Bites

Question 1

What are the causes of dental deep bites

Answer 1

• Over-eruption of incisors
• Increased interincisal angle
• Mesial drift posteriors
• Muscle abberations (i.e tongue thrust)

Question 2

Under the posterior canial base is the

Answer 2

mandibular ramus

Question 3

Under the anterior cranial base is the

Answer 3

maxillary posterior teeth

Question 4

Etiology of skeletal deep bites

Answer 4

• Non-ideal cranio-facial growth
• Excess vertical development of ramus and posterior cranial base
• Lack of vertical growth between maxillary posterior teeth and anterior cranial base
• Mandible rotates in closing direction

Question 5

Characteristics of skeletal deep bite

Answer 5

• Posterior face height approximates anterior face height
• Lower anterior face height smaller v.s upper face height
• Face is broad and bradycephalic
• Four planes (horizontal) of face are almost parallel
• Midface usually retrusive
• Lips are thin
• Prominent labio-mental sulcus
• Small teeth (prone to attrition)
• Masticatory muscles are powerful

Mandible morphology

• Well developed body of mandibule
• Symphysis is strong and broad
• Well developed pogonion

Question 6

Characteristics of closed bite

Answer 6

• Reduction in dental height
• Over-closed mandible
• Decreased lower facial vertical dimension

Question 7

Casuses of a closed bite

Answer 7

• Loss of posterior teeth
• Attrition and decreased crown height
• Agenesis posterior teeth

Question 8

Open bite causes

Answer 8

• habits
• Abnormal tongue posture
• Tongue thrust
• Ankylosis of deciduous teeth
• Very large tongue

Question 9

Characteristics of dental open bite

Answer 9

• Normal cranio-facial growth

- Normal anterior/posterior facial heights

Question 10

Etiology of skeletal open bites

Answer 10

• Cranio-facial growth pattern
• Excess vertical growth between anterior cranial base and maxillary posterior teeth
• Lack vertical development of ramus and posterior cranial base
• Mandible rotates in opening direction

Question 11

Characteristics of skeletal open bite

Answer 11

• Posterior face height is about half anterior face height
• Lower anterior face height is much larger v.s upper face height
• Face is long narrow and dolicocephalic
• Four planes of face divergent
• Face is very convex
• Lips are short and incompetent
• Large tooth size relative to deep bite sizes
• Mastication musculature is weak

Mandible morphology

• Mandible body is short and narrow
• Symphysis is tear-drop shapped and narrow
• Pogonion recessive= little/no chin button
• Condylar head inclined backward