Hypodontia

Question 1

What is hypodontia?

Answer 1

Congenital absence of one or more teeth

Question 2

What is anodontia?

Answer 2

Complete absence of teeth

Question 3

When is hypoodontia considered severe?

Answer 3

6 or more congenitally absent teeth

Question 4

How common is hypodontia?

Answer 4

Approx. 6% (excl. 8s)
- 6.3% F
- 4.6% M

Question 5

What is the prevalence of hypodontia in primary dentition?

Answer 5

0.9% (rare)

Question 6

What teeth are most affected by hypodontia?

Answer 6

(8s)
L5s
U2s
U5s
Lower incisors

Question 7

How common are missing upper lateral incisors?

Answer 7

• 1-2% of population
• approx. 20% of all missing teeth
• associated with ectopic canine

Question 8

What is associated with missing teeth in relation to orthodontics?

Answer 8

Slow moving teeth
- ortho takes longer

Question 9

What is the aetiology of hypodontia?

Answer 9

Non-syndromic
- mutations in at least 3 genes
- familial
- sporadic

Syndromic
- >100 craniofacial syndromes associated with hypodontia
- cleft lip & palate
- anhydrotic ectodermal dysplasia

Environmental
- trauma
- radiotherapy/chemotherapy

Question 10

How might potential hypodontia present clinically?

Answer 10

• delayed or asymmetric eruption
• retained or infra-occluded decidious teeth
• absent decidious tooth
• tooth form

Question 11

What is the most important thing to look out for when diagnosing potential hypodontia?

Answer 11

Order of eruption of teeth (is there any disorder of sequence?)

Question 12

What problems can be associated with hypodontia?

Answer 12

• microdontia
• malformation of other teeth
• short root anomaly
• impaction
• delayed formation and/or malposition of other teeth
• maxillary canine/first molar transposition
• taurodontism (long pulp chamber, flow is below CEJ)
• enamel hypoplasia
• altered craniofacial growth

Question 13

What issues can hypodontia directly cause?

Answer 13

• spacing
• drifting
• over-eruption
• anaesthetic impairment
• functional problems

Question 14

List the hypodontia care pathway:

Answer 14

• GDP recognition
• referral to specialist orthodontist
• in GDH

Question 15

In which teeth is taurodontism most common/most difficult?

Answer 15

7s

Question 16

What special investigations may you require in a patient with hypodontia?

Answer 16

• study models
• planning models
• radiographs
• photographs
• conebeam CT

Question 17

What treatment options are available for hypodontia of upper lateral incisors?

Answer 17

• accept
• restorative alone
• orthodontics alone
• combined ortho & restorative treatment

Question 18

What size are lateral incisors roughly?

Answer 18

6.5-7mm

Question 19

What size are central- incisors roughly?

Answer 19

9mm

Question 20

What restorative options are available for treatment of missing upper laterals where the space is open?

Answer 20

• resin bonded bridge
• implant
• partial denture
• auto-transplantation
• conventional bridgework

Question 21

What tooth is the ideal abutment for a resin bonded bridge?

Answer 21

canine

Question 22

What is key to successful management?

Answer 22

• inter-disciplinary team
• joint assessment and treatment planning with precise aims
• joint collaboration at transitional stages of treatment

Question 23

What are the advantages of resin bonded bridges?

Answer 23

• simple
• can do when pt is young
• non-destructive
• can look good
• place on semi-permanent basis

Question 24

What are the disadvantages of resin bonded bridges?

Answer 24

• high failure rate
• appearance sometimes not good
• orthodontic retention needs are high
• predictable aesthetics

Question 25

Why is a cone-beam CT useful for restorative dentists sometimes?

Answer 25

You are able to assess the volume of alveolar bone present (cannot do this with regular plain film)

Question 26

Why does a high smile line make restorative dentistry difficult?

Answer 26

Unforgiving gingival margins, hard to hide restorations etc.

Question 27

In a patient with one missing lateral incisor, how could you treat the patient without orthodontics?

Answer 27

Camouflage
- composite on 3 to mimic adjacent lateral
- cuspal reduction of 3
- bleaching of 3 to mimic adjacent lateral

Question 28

Why might an RPD be a good option for hypodontia patients?

Answer 28

• able to replace multiple missing teeth at different sites in arch
• able to replace soft tissue

Question 29

Why do RBB in a canine position have a lower survival rate compared to a RBB in a lateral position?

Answer 29

Canines are an important tooth in lateral excursion (eg canine guidance)

Question 30

Why is a canine the ideal abutment tooth for a lateral RBB?

Answer 30

• long roots
• crown dimensions
• less ‘shine-through’

Question 31

How much space is required for an implant to be placed in a lateral incisor position?

Answer 31

In excess of 6.5mm

Question 32

What is a disadvantage of implant treatment in hypodontia pts?

Answer 32

Can’t do it until growth has ceased 21+
- if you place implant too young it will end up looking submerged as alveolus continues to grow