Hypodontia Flashcards
What is hypodontia?
The developmental absence of 1 or more teeth, excluding the third molars.
Not congenital as teeth develop during growth, not present at birth.
Define mild/moderate/severe hypodontia and adontia.
Mild: 1-2 missing teeth
Moderate: 3-5 missing teeth
Severe: 6+ missing teeth
Adontia: no teeth at all
Describe the prevalence of hypodontia.
- 0.08-1.55%
- Maxilla > Mandible
- M=F
- Lateral incisor most common
Which teeth are most commonly missing?
- Lower 5s
- Upper 2s
- Upper 5s
- Lower 1s
What genes are associated with hypodontia?
- Msx1
- Pax9
- Axin1
- Ssh
Strong genetic component, check family history.
Name 6 conditions associated with hypodontia.
- Ectodermal dysplasia
- Down’ syndrome (Trismony 21, extra chromosome 21)
- Ehler’s Danlos
- Cleft lip and palate
- Van der Woude
- Hemifacial microsomia
Describe ectodermal dysplasia.
- Group of genetic syndromes associated with abnormalities in the ectodermal structues
- Autosomal dominant or recessive
- Affects teeth, glands, hair, nails and saliva
Describe the common extra-oral features of hypodontia.
Some pts have classic extraoral features:
- Reduced alveolar development due to absence of teeth, can lead to a retrusive maxilla (and/or mandible)
- Tendency towards class 3 malocclusion due to retrusive maxilla
- Reduced vertical proportion
What are the intra-oral features of hypodontia?
- Abnormal tooth morphology
- Abnormal eruption
- Reduced alveolar development
Describe the effects of hypodontia on tooth morphology.
- The teeth that are present may be smaller, creates spacing
- If someone is missing a lateral incisor they often have a contralateral peg lateral
- Enamel hypoplasia could be present
- Taurodontism = really long pulp chamber
Describe the effects of hypodontia on tooth eruption.
- Ectopic position e.g. canine drifting into place of lateral incisor
- Transpositions, teeth swap places. Pseudo = crown in wrong place, root correct. True = crown and root in wrong place
- 90 or 180 degree rotations
- Infraocclusion (submersion) bc delayed exfoliation
- Delay of permanent tooth eruption
Describe reduced alveolar development in hypodontia.
Reduced alveolar development = reduced vertical proportions = increased overbite.
Why is prevention important in children with hypodontia, how is this achieved?
Important to preserve the teeth they do have.
- OHI
- Diet analysis and advice
- Fluoride
- Fissure seal permanent molars
- Fissure seal primary molars if being retained
- Mouthguard for protrusive incisors
- Artificial saliva for pts with underlying syndrome e.g. ectodermal dysplasia
Why is early orthodontic referral for children with hypodontia important?
- If you suspect the absence of a lateral incisor the ideal time of referral is aged 7-9 years in order to consider the position of eruption of the canine.
- If you suspect that the 5s are absent also refer. May be able to extract the Es early to allow some mesial drift of the 6s.
- Consideration of holding onto the E for longer if there is no crowding/spacing and using the extraction space in order to align the teeth.
What are the 2 management options for mild hypodontia?
- Open: leave space for prosthetic treatment
- Close: use orthodontics to close any residual space
What factors should you consider when deciding to open or close a space for a missing lateral incisor?
Consider size and shape of canine if you are thinking of using it to fill the lateral space.
How would you manage this patient?
- Class 3 incisor relationship
- Large centreline shift
- Missing UR2
- Create space to improve overjet and centreline, prosethesis used
How would you manage this patient?
- Close the space
- Class 2, disguise 3s as 2s (add composite to teeth) and 4s as 3s
What are the aesthetic considerations for digsuising canines as laterals?
Could extrude canines slightly to bring the gingival margin down and have it appear more like a lateral incisor.
What are the factors to consider when deciding to open or close space from a missing premolar?
What factors should be considered when choosing restorative replacement of missing teeth?
- Aesthetics
- Cost
- Life span/restorative burden
E.g. implants require at least 7mm interdental space and roots of adjacent teeth must be completely parallel
