Hypodontia

Question 1

Define Hypodontia

Answer 1

• Development absence of one or more teeth excluding 3rd molars

Question 2

Incidence

Answer 2

• 3.5-6%

Question 3

Gender

Answer 3

• F>M 3:2

Question 4

Number of teeth

Answer 4

• Mild 1-2
• Moderate 3-5
• Severe (6+)

Question 5

Which teeth involved?

Answer 5

• 25-35% of 8s
• 3% of 5s
• 2% of 2s
  -<1% of 1s

Question 6

Aetiology of Hypodontia

Answer 6

• Environmental- drugs, radiotherapy, chemotherapy
• Genetics - Familial, autosomal dominant MSXI, PAX9, AXIN2
• Syndromic , Non- syndromic

Question 7

Definitive Management

Answer 7

• Permanent dentition
• wants treatment
• Good OH/ caries free
• Records- Radiographs, Photos, SM, Diagnostic aids.
• Multidisciplinary: Orthodontist , Restorative dentist, Paediatric, GDP.

Question 8

Options for Missing 2’s

Answer 8

• Accept
• Restorative treatment only
• Orthodontics alone
• Orthodontics and restorative

Question 9

What to watch out for?

Answer 9

• Primary teeth retained beyond their normal time.
• Primary teeth missing
• asymmetric eruption patterns
• Delayed eruption patterns
• Small permanent teeth (link between small teeth and missing teeth)
• Retained or infraoccluded primary teeth
• Spacing in arch
• palpate for upper canine

Question 10

Options for Missing 2s

Answer 10

• Open or close space for missing 2s :

Facial related- Skeletal class , Buccal corridor, Smile line

Dental related: Incisor classification, Centre line, Canine position, Spacing

Tooth related: Canine Size/ Shape / Colour. First premolar size. Enamel quality and quantity

Question 11

Mechanics for Opening space s

Answer 11

• No bracket modification required
• Use of push / pull mechanics depending on Centre lines and space
• May need Anchorage reinforcement if retracting canines
• Once in rectangular wire can place Pontic onto archwire or instead use closed coil to hold space
• How much space needed?
• How do we measure space?

Question 12

Retention when opening space- Prior debond

Answer 12

• Prior to Debond
• Need to check for root parallelism
• Need to ensure correct space available
• Review with colleagues undertaking restorative work.

Question 13

Retention when opening space-

Options for retention (prior to restorative work)

Answer 13

• VFR with acrylic Pontic inserts
• Hawley with stops !! (+/- bonded retainer)

Question 14

Tooth replacement Option

Answer 14

1 - Resin bonded bridges: Non- destructive, 84% failure at 5 years
- Appearance can be poor

2 Implant
- Need 6.5-7mm of space
- Need good bone
- Need to have stopped growing

Others . P. Denture

Question 15

Mechanism for closing space

Answer 15

*- Bracket modifications: Upper 3 brackets = -7 torque buccal
- Invert to get +7 torque (palatal).
- Place gingivally to extrude (then need enamel reduction)
-Upper 4s- Bond 3 or 4 bracket more distally and incisally (then will need composite build up)
- Close 1-1 and then 3-3 first
- Watch OJ - May need class 3 elastics or lower extractions

Question 16

Retention when closing space

Answer 16

• Review with restorative colleague or GDP pre Debond
• VFRs +/- bonded retainer
• Restorative work I.e. composite build ups, grinding, bleaching , gingival surgery

Question 17

Adv and dis adv of space Opening

Answer 17

• Advantages :
  -Gives teeth in correct order- advantageous both functional and aesthetic. Good intercuspation in buccal segments.
• May not be possible to close the space completely
• Improved aesthetics, permanent teeth may not be ideal shape and colour if space closure consider e.g U3s may be very pointed
• Disadvantages :
  -Need for life long prothesis.
• Maintain lower E long-term but reduce mesial- distal width (Premolarise) as eventual space once E is lost is big for Resin- Bonded Bridge.
• Longer treatment
• Gaps during treatment.
• Prone to relapse
• More root resorption

Question 18

Space Closing - Adv and dis adv

Answer 18

Advantages-
-Shorter treatment.
-Avoid prosthesis.
- Less maintenance
- High patient satisfaction
- May be incorporated into Xtn pattern if malocclusion dictates e.g. crowding present

Disadvantage-
- Often still needs to restorative work and upkeep
- Unnatural teeth order prone to relapse
- Aesthetics- shape and colour of 3/3 next to 1/1

Question 19

Peg Laterals - Decision about lateral

Answer 19

• Width at cervical margins
• Lenght
• Height
• Bucco- palatal position
• inter occlusal space

Question 20

General treatment principle and decision for Hypodontia?

Answer 20

• Combined ortho + restorative option
  Options:
• Reopen space
• close space
• Redistribute space
• Maintainance of primary teeth e.g retain lower Es if good root

Decision:
- Maintain space for prosthetics or closed space

Question 21

What factors count for decision to make?

Answer 21

• Malocclusion and extend of hypodontia
• Shape and colour of permanent teeth
• Pt’s age
  -Pt’s opinion
• Pt’s co operation

Question 22

When U2/2 absents ? Treatment option consider ?

Answer 22

• Consider early referral to assess as part of long -term orthodontic- restorative plan.

-Consider interceptive Extraction of UC/C to encourage 3/3 to erupt into laterals position

Question 23

When 5s absent what to consider ?

Answer 23

• Depends on crowding
  i- if spaced/ aligned arch Preserve E
  ii- Crowding - Extraction of E’s when appropriate and use space to align malocclusion for maximum spontaneous space closure consider interceptive Xtn E’s at 9yrs. If Es survive until 20yrs then they appear to have good prognosis for long term survival

Question 24

What is incidence of missing lateral incisors ?

Answer 24

• 2%