etiology of malocclusions

Question 1

Predisposing Factors to Malocclusion, ranks?

Answer 1

• Disturbances in Embryologic Development (3)
• Heredity (genetics) (1)
• Functional matrix: Muscular or functional disturbances and Habits (2)
• Traumas: Especially mandibular fractures.

Question 2

etiological diagram of malocclusions

Answer 2

Question 3

Primary Etiologic Sites of malocclusion, disorders associated?

Answer 3

Bone and hard tissues

• Neuromuscular system… Cerebral Palsy
• Bone: OI
• Teeth: Ectodermic Dysplasia, affects number/ shape of teeth
• Soft tissues (excluding muscles): Sclerodermia

Question 4

Disturbances in Embryologic Development and malocclusions

Answer 4

Teratogens may interfere with cellular differentiation during pregnancy
• Alcohol
• Drugs
• Pollution
• Example: Cleft and Lip Palate (believed genetic now)

Question 5

Crouzon Syndrome

tx?

Answer 5

it is characterized by underdevelopment of the midface and eyes that seem to bulge from their sockets

Crouzon’s syndrome arises because of prenatal fusion of the superior and posterior sutures of the maxilla, along the wall of the orbit. Both structure prematurely fuse and halt growth= small sockets and a retruded maxilla

Tx: artificial sutures

Question 6

Treacher Collins
eyes?
cheeks/jaw? 
nose? 
ear? hearing? 
palate/lip?
heart?

Answer 6

• down slanting eyes with notched lower lids
• underdeveloped cheek and jawbones,
• prominent nose, broad mouth and characteristically small chin with steep lower jaw angle.
• Ears are malformed or prominent and hair may extend towards the face;
• hearing loss is also possible.
• may have: cleft lip and/or palate, heart defects, and strabismus

Question 7

Cleidocranial dysplasia
teeth?
delayed closure of? 
premature closing of what suture?
what structures protrude? 
nasal bridge width? 
palate? 
stature overall?
spine?

Answer 7

hyperdontia=excess teeth due to non functional dental sac
teeth will replace bone thus weakening the structure

• Delayed closure (ossification) of the space between the bones of the skull (fontanels)
• Premature closing of the coronal suture
• Protruding jaw (mandible) and protruding brow bone (frontal bossing)
• Wide nasal bridge due to increased space between the eyes (hypertelorism)
• High arched palate or possible cleft palate
• Short stature
• Scoliosis of the spine

Question 8

Cleidocranial dysplasia

dental abnormalties and shoulders

Answer 8

Dental abnormalities - failure to lose the baby teeth (deciduous) at the expected time; slow
eruption of secondary teeth; extra teeth; delayed or absent formation of teeth
can touch shoulders, lack clavicle

Question 9

OI classes

Answer 9

I- less bone, majority of cases
III- worse
IV- worse

Question 10

OI associated with?

Answer 10

DI- missing and malformed teeth

Question 11

Dentinogenesis Imperfecta (DI)
significant aspect of what disorder?
all teeth affected the same way?
within a family of OI?

Answer 11

• DI is one of the most significant aspect of OI
• Not all teeth are affected in the same manner
• If one OI member of the family has DI, all the other OI member will have DI as well

Question 12

OI classes and DI correspondence

Answer 12

I- 20
IV- 40-60
III- 100
II- N/A dead at birth

Question 13

Down Syndrome
hypoplasia where? 
bridge of nose, midface bones/ maxilla size?
usual class? contributes to? 
frequently affected teeth?

Answer 13

• Underdevelopment or hypoplasia of the midfacial region (retruded maxilla)
• The bridge of the nose, bones of the midface and maxilla are relatively smaller in size.
• Prognathic Class III occlusal relationship which contributes to an open bite (Vittek et al, 1994).
• Molars, impacted maxillary canines, and missing premolars

Question 14

Cleido Cranial Dysplasia:  Some facial features
forehead?
sinuses?
primary teeth?
Supernumerary? 
malocclusion?

Answer 14

• Wide –flat forehead
• Wide set eyes
• Small sinuses
• Prolongued retention of primary teeth
• Supernumary teeth
• Severe malocclusion

Question 15

Condylar Alterations

Answer 15

possibly missing condyles

Question 16

Normal skeletal relationship

Answer 16

1. Cranial base
   • Position and projection of the upper jaw
   • Position and projection of the lower jaw

Question 17

Types of malocclusion

Answer 17

occurs in all 3 dimensions, angles classified in AP relations (classes I, II and III)

Question 18

skeletal patterns of malocclusion, combos

Answer 18

class II: usually man retrusion, 40% cases are bi-retrusive
class III: 90% cases are a combo of man prgnathism and max hypoplasia

Question 19

phenotypic diversity among occlusal classes

Answer 19

not all cases of the same occlusal class are the same, each is unique in what combos it is composed of
example: class III could be due to a combo of man protrusion and max hypoplasia or one or the other 
this means all should not be treated the same

Question 20

ethnic prevalence of malocclusion

Answer 20

Depends on the population
• Southeast Asian ~15%1
• Middle eastern ~10%1
• Indian ~1%1
• European ~1-4%1,2

Question 21

Genetics of Class III

Answer 21

• Focused on mandibular prognathism

intervention with variability in corrections

Question 22

Deep Bite and Openbite: Multifactorial Etiologies

Answer 22

1. Transitory
2. Skeletal (genetic)
3. Neuromuscular imbalance (CP)
4. Oral habits
5. Anterior tongue posture
6. Combination- Sleep Apnea