Hypodontia and Supernumerary Teeth

Question 1

Hypodontia

Answer 1

less than 6 congenitally missing teeth

Question 2

Oligodontia

Answer 2

more than 6 congenitally missing teeth

Question 3

Anodontia

Answer 3

Absence of all teeth

Question 4

Hyperdontia

Answer 4

Extra teeth

Question 5

◼ Missing:
 Hypodontia -
 Oligodontia -
 Anodontia - ◼ Excess:
 Hyperdontia -

Answer 5

less than 6 congenitally missing teeth
6 or more missing teeth
failure of teeth to develop (agenesis of teeth), very rare

extra teeth (Supernumerary teeth)

Question 6

Congenitally Missing Teeth
(7)

Answer 6

◼ Ectodermal dysplasia
◼ Hypothyroidism
◼ Down Syndrome
◼ Cleft palate
◼ Genetic
◼ Radiation
◼ Random – no other associations

Question 7

◼ Ectodermal dysplasia:

Answer 7

group of syndromes, missing or peg shaped teeth,
thin sparse hair, absence of sweat glands

Question 8

◼ Hypothyroidism: (3)

Answer 8

thyroid, pituitary, hypothalamus abnormalities

Question 9

◼ Down Syndrome:

Answer 9

trisomy 21

Question 10

◼ Cleft palate :

Answer 10

one in 600-800 births

Question 11

Congenitally Missing Teeth
◼ Congenital absence of teeth results from

Answer 11

disturbances during
the initial stages of tooth formation – INITIATION AND
PROLIFERATION.

Question 12

◼ Since primary tooth buds give rise to permanent tooth buds, if a
primary tooth is missing…

Answer 12

there can’t be a successor

Question 13

◼ Can have missing permanent teeth even when …

Answer 13

primary was present

Question 14

Hypodontia◼ Incidence
 —% of general population (excluding third molars)
 —% - Congenitally missing primary teeth
 —% - 3rd molars missing in
 Hypodontia is higher in females on a – ratio
 Commonly runs in families

Answer 14

2 – 10
0.1% to 0.4%
20% to 25%
3:2

Question 15

 As a general rule, if only one or a few teeth are missing, the absent tooth will be

Answer 15

the most distal
tooth of any given type

Question 16

Hypodontia
Etiology
 Missing teeth can be inherited as part of a syndrome or a polygenic multifactorial model of etiology
(4)

Answer 16

 Genes –MSX1, PAX9, AXIN2
 Cytotoxic drugs
 Radiotherapy
 Random

Question 17

If primary tooth missing –

Answer 17

can’t have permanent tooth

Question 18

The most commonly missing permanent
teeth are the

Answer 18

second premolars (more
than 40% of all missing teeth)

Question 19

— 2nd premolars missing more
often than —

Answer 19

Mandibular
maxillary

Question 20

Mandibular 2nd premolars missing more
often than maxillary
◼ Followed by —
◼ Followed by —

Answer 20

maxillary lateral incisors
upper second molars

Question 21

Treatment Options
(4)

Answer 21

▪ Replacement
▪ 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 22

▪ Replacement
(3)

Answer 22

▪ Prosthetically
▪ Transplantation
▪ Implant – retain 1° tooth till close to time of implant for bone

Question 23

Canine substitution - Ideal
(5)

Answer 23

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

Question 24

Order of Enameloplasty
(5)

Answer 24

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

Question 25

Supernumerary teeth –

Answer 25

disturbances during the initiation and
proliferation stages of dental development

Question 26

Extra tooth obviously has great potential to

Answer 26

disrupt normal occlusion

Question 27

— to remove them is indicated

Answer 27

Early intervention

Question 28

Incidence of hyperdontia much — than hypodontia

Answer 28

lower

Question 29

◼ Primary dentition - —%
◼ Permanent dentition - —%
◼ Upper jaw (Pre-maxilla) - —%

Answer 29

0.5
1.0
85

Question 30

Maxillary midline = most common location called a —

Answer 30

mesiodens

Question 31

(3) can also appear

Answer 31

Laterals, premolars and 4th molars

Question 32

Supernumerary tooth - (2) in shape

Answer 32

Typical or atypical

Question 33

Supernumerary teeth - Mesiodens
(3)

Answer 33

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

Question 34

Supernumerary teeth
◼ Treatment aimed at extraction before problems arise, or
minimizing effect on other teeth
◼ General rule:

Answer 34

 More supernumeraries, more abnormal, higher their
position, harder to manage

Question 35

Conical supernumerary teeth
Remove
(5)

Answer 35

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

Question 36

Conical supernumerary teeth
Don’t remove
(2)

Answer 36

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

Question 37

Supernumerary teeth - Typical
(2)

Answer 37

◼ 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 38

Impactions & Ectopic Eruptions
◼ Estimated incidence at –%
◼ Twice as common in …
◼ –% bilateral impactions
◼ Mandibular canine impaction is –%

Answer 38

1.7
females (1.17%) as in males (0.51%)
8
0.35

Question 39

Etiology
(4)

Answer 39

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

Question 40

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 40

75
6
Two
6
85
83

Question 41

Diagnosis
(3)

Answer 41

◼ Periapical radiographs
◼ Occlusal radiographs
◼ CBCT imaging

Question 42

Periapical radiographs
(2)

Answer 42

◼ Clark’s Technique
◼ SLOB rule