hypodontia

Question 1

give the definition of hypodontia

Answer 1

developmental abscence of one or more teeth

excluding third molars

Question 2

describe the classification system for hypodontia

describe also the IOTN

Answer 2

mild = 1-2 missing teeth

moderate = 3-5 missing teeth

severe / oligodontia = 6 or more missing teeth

anodontia = complete abscence of any teeth

IOTN

• 4h = 1 tooth missing in any quadrant
• 5h = >1 tooth missing in any quadrant

Question 3

what is the prevalence of hypodontia in the primary dentition?

Answer 3

0.08-1.55%

Question 4

where is hypodontia more common in primary dentition?

max/mand

M/F

most common tooth??

Answer 4

maxilla>mandible

M=F

lateral incisors

Question 5

what is the prevalence of hypodontia in the permanent denition?

Answer 5

6%

Question 6

where is hypodontia more common in the permanent dentition?

M/F?

most common missing tooth?

Answer 6

F>M

lower 5s then upper 2s

Question 7

what is the aetiology of hypodontia?

Answer 7

• strong genetic component
  
  • MSX1, PAX9, AXIN1, SHH
• environmental
  
  • cleft palate disruption during development

Question 8

what syndromes are associated with hypodontia?

Answer 8

• ectodermal dysplasia
• downs syndrome
• ehlers danlos
• van der woude
• hemifacial microsomia
• syndromic / non-syndromic cleft palate

Question 9

what are the clinical features of ectodysplasia?

how does it affect the dentition, sweat glands, hair, nails and saliva?

Answer 9

Question 10

what are the extra-oral features of hypodontia?

Answer 10

• reduced alveolar development
  
  • retrusive maxilla with/without retrusive mandible
  • tendency towards class III malocclusion
  • reduced vertical proportions

Question 11

what are the intra-oral features of hypodontia?

describe the change to tooth morphology

Answer 11

• microdontia
  
  • localised/generealised
  • may affect crowns and roots
  • contributes to spacing
• conical teeth
  
  • localised/generalised
• enamel hypoplasia
  
  • due to effect on dental lamina during development
• taurodontism
  
  • enlarged pulp chamber with apical displacement of pulp floor, diagnosed radiographically
  • often seen in molars

Question 12

what are the intra-oral features of hypodontia?

describe the change to eruption

Answer 12

• ectopic position
  
  • impaction and transposition may affect maxillary canines
  • ectopic eruption in lateral incisor space
• transpositions
  
  • teeth swap spaces
  • can be pseudo - crown is in wrong place but root is in correct place
    
    • or true- both in wrong place
• rotations
• infraocclusion
  
  • delayed exoliation of primary teeth
• delayed eruption of permanent teeth
  
  • average delay - 1.5 years

Question 13

what are the intra-oral features of hypodontia?

describe the change to alveolar development

Answer 13

• increased overbite
  
  • due to
    
    • reduced vertical proportions
    • reduced alveolar development
    • retroclination of incisors

Question 14

what prevention methods can be used in patients with hypodontia?

Answer 14

• diet analysis and advice
• oral hygiene advice
• fluoride supplementation
• fissure sealing permanent molars and pits
• mouth guards to protect protrusive maxillary incisors
• artificial saliva in patietns with xerostomia

Question 15

when is early orthodontic referral suggested in the case of hypodontia?

Answer 15

• 7-9 years if developmental abscence of upper 2s suspected
  
  • consider position of maxillary canine
• if 5s are absent
  
  • consideration of extraction of Es if crowding - to allow mesial drift of 6s
  • consideration of long term prognosis of Es if no crowding/spacing

Question 16

what are the options when there is mild hypodontia

Answer 16

open or close the space

• open
  
  • recreate, distribute and leave space for a prosthetic replacement
• close
  
  • use orthodontics to close any residual spacing associated with the missing tooth

Question 17

what factors should you consider in hypodontia on whether to open or close the space?

Answer 17

1. incisor relationship and overjet
2. molar relationship
3. overbite
4. crowding/spacing
5. canines
   
   • eruption of 3s
   • smile
   • shape/size of 3s
6. patient’s wishes
   
   • prosthesis: restorative burden

Question 18

open or close the space in this case?

class III with tenuous overjet

Answer 18

open

• correction of reverse overjet
• maintains arch length and lip support

Question 19

open or close the space in this case?

class II div II incisor relationship

deep overbite

class II canines

Answer 19

close space

• good in class II cases
• canines have a good colour