hypodontia and supernumeraries

Question 1

Hypodontia

Answer 1

less than 6 congenitally missing teeth

Question 2

Oligodontia

Answer 2

6 or more congenitally missing teeth

Question 3

Anodontia

Answer 3

Absence of all teeth

Question 4

Hyperdontia

Answer 4

Extra teeth

Question 5

Congenitally Missing Teeth potential etiologies:
◼ Ectoderm?
◼ thyroid?
◼ trisomy?
◼ Cleft?
◼ Genetic?
◼ drug/therapies?
◼ Random?

Answer 5

◼ Ectodermal dysplasia: group of syndromes, missing or peg shaped teeth, thin sparse hair, absence of sweat glands
◼ Hypothyroidism: thyroid, pituitary, hypothalamus abnormalities
◼ Down Syndrome: trisomy 21
◼ Cleft palate : one in 600-800 births
◼ Genetic
◼ Radiation/ cytotoxic drugs
◼ Random – no other associations

Question 6

◼ Congenital absence of teeth results from disturbances during what stages of development?

Answer 6

◼ Congenital absence of teeth results from disturbances during the initial stages of tooth formation – INITIATION AND PROLIFERATION

Question 7

Since primary tooth buds give rise to permanent tooth buds, if a primary tooth is missing what is the result?

Answer 7

Since primary tooth buds give rise to permanent tooth buds, if a primary tooth is missing there can’t be a successor

Question 8

can permanent teeth be missing despite a primary tooth present?

Answer 8

Can have missing permanent teeth even when primary was
present.

Question 9

Hypodontia
◼ Incidence
 % of general population (excluding third molars)
 % - Congenitally missing primary teeth
 %- 3rd molars missing in
 M:F ratio?
 Commonly runs in?

Answer 9

 2 – 10% of general population (excluding third molars)
 0.1% to 0.4% - Congenitally missing primary teeth
 20% to 25% - 3rd molars missing in
 Hypodontia is higher in females on a 3:2 ratio
 Commonly runs in families

Question 10

if only one or a few teeth are missing, the absent tooth will be?

Answer 10

if only one or a few teeth are missing, the absent tooth will be the most distal
tooth of any given type

Question 11

genes invovled with hypodontia

Answer 11

MSX1, AXIN2 PAX9

Question 12

The most commonly missing permanent teeth are?

Answer 12

The most commonly missing permanent teeth are the second premolars (more than 40% of all missing teeth)
Mandibular 2nd premolars missing more often than maxillary

Question 14

2nd and 3rd most commonly missing perm teeth

Answer 14

2. maxillary lateral incisors
3. upper second molars

Question 15

Treatment Options for missing teeth

Answer 15

▪ Replacement:Prosthetically, Transplantation, ot Implant – retain 1° tooth till close to time of implant for bone
▪ Extraction of the primary tooth and allowing permanent teeth to drift
▪ Extraction followed by orthodontic treatment
▪ Maintain tooth or teeth, will have occlusal problems since second deciduous tooth is not same size as 2nd premolar

Question 16

Missing maxillary lateral tx options

Answer 16

• Canine Substitution
• Tooth supported restoration
• Single Tooth Implant

Question 17

Canine substitution - Ideal scenario
◼ Similar color to?
◼ Narrow width at?
◼ Relatively flat where?
◼ Narrow width where?
◼ Enameloplasty?

Answer 17

◼ Similar color to central incisor
◼ Narrow width at the CEJ
◼ Relatively flat labial surface
◼ Narrow mid-crown buccolingual width
◼ Enameloplasty !!!

Question 18

Order of Enameloplasty for canine sub

Answer 18

1. Cusp tip
2. Mesial and distal (often underperformed)
3. Labial ridge
4. Mesial composite
5. Line angles

Question 19

Supernumerary teeth result from disturbances when?

Answer 19

disturbances during the initiation and
proliferation stages of dental development

Question 20

Extra tooth obviously has great potential to disrupt?

Answer 20

xtra tooth obviously has great potential to disrupt normal occlusion

Question 21

when to intervene with supernumeraires?

Answer 21

Early intervention to remove them is indicated

Question 22

hyperdontia incidence compared to hypo

Answer 22

much lower

Question 23

hyperdontia incidence rates
◼ Primary dentition -
◼ Permanent dentition -
◼ Upper jaw (Pre-maxilla) -

Answer 23

◼ Primary dentition - 0.5%
◼ Permanent dentition - 1.0%
◼ Upper jaw (Pre-maxilla) - 85% (85% cases here)

Question 24

most common supernumerary?
others?

Answer 24

mesiodens
Laterals, premolars and 4th molars can also appear

Question 25

supernumerary tooth shapes

Answer 25

can be normal or abnormal

Question 26

Supernumerary teeth - Mesiodens
◼ how many can there be?
◼ Most common cause of?
◼ alt of tooth path?

Answer 26

◼ Often exist singularly, but sometimes
in combination
◼ Most common cause of unerupted
upper central incisor
◼ Can deflect tooth

Question 27

mesiodens halting 8/9 eruption tx?

Answer 27

removal of mesiodens and exposure/bracketing of 8/9

Question 28

Supernumerary teeth
◼ Treatment aimed at? why?
◼ General rule:

Answer 28

◼ Treatment aimed at extraction before problems arise, or minimizing effect on other teeth
◼ General rule: More supernumeraries, more abnormal, higher their position, harder to manage

Question 29

Conical supernumerary teeth removal indications
◼ If it?
◼ orientation?
◼ Displacing?
◼ Producing?
◼ Delaying?

Answer 29

◼ If it erupts
◼ Inverted – won’t erupt
◼ Displacing adjacent teeth
◼ Producing diastema
◼ Delaying eruption of
permanent tooth

Question 30

Conical supernumerary teeth removal contraindications

Answer 30

◼ If well above the apices of the permanent tooth
◼ Observe

Question 31

Supernumerary teeth - Typical presentation
◼ Resembles? produces what effects?
◼ Extract which tooth? unless?

Answer 31

◼ Resembles a normal tooth in morphology & commonly produces crowding or displacement
◼ Extract the tooth most dissimilar to the contralateral tooth, unless it is severely displaced

Question 32

Impactions & Ectopic Eruptions
◼ Estimated incidence at?
◼ M:F?
◼ % bilateral impactions
◼ Mandibular canine impaction is %

Answer 32

◼ Estimated incidence at 1.7%
◼ Twice as common in females (1.17%) as in males (0.51%)
◼ 8% bilateral impactions
◼ Mandibular canine impaction is 0.35%

Question 33

Etiology of impactions/ectopic eruptions
◼hard tissue?
◼ path?
◼ Disturbance of ?
◼ genetic?

Answer 33

◼ Local hard tissue obstruction
◼ Local pathology
◼ Disturbance of normal development of the incisors
◼ Hereditary or genetic factors

Question 34

Canine impaction considerations
◼ It is unerupted after % of its root development
◼ The contralateral tooth has erupted for at least ? months with complete root formation
◼ ? years after the adolescent growth spurt were passed
◼ ? months after canine root completion was passed
◼ % of palatal impactions had sufficient space for eruption
◼ % of labial impactions showed an arch length deficiency

Answer 34

◼ It is unerupted after 75% of its root development
◼ The contralateral tooth has erupted for at least 6 months
with complete root formation
◼ Two years after the adolescent growth spurt were passed
◼ 6 months after canine root completion was passed
◼ 85% of palatal impactions had sufficient space for eruption
◼ 83% of labial impactions showed an arch length deficiency

Question 35

diagnostic imaging for impactions/ectopic eruptions

Answer 35

◼ Periapical radiographs (SLOB rule)
◼ Occlusal radiographs
◼ CBCT imaging

Question 36

CBCT vs. conventional imaging for impactions and ectopic eruptions

Answer 36

Conventional radiographic methods demonstrated a more subjective diagnosis. CBCT is a more accurate and precise examination method