hypodontia

Question 1

definition

Answer 1

congenital absence of one of more teeth (excluding third molars)

Question 2

anodontia

Answer 2

complete absence of teeth

Question 3

severe hypodontia/oligodontia

Answer 3

6 or more congenitally absent teeth

Question 4

prevalence of hypodontia

Answer 4

around 6% excluding 8s

6.3% F, 4.6% M in European pop

Question 5

prevalence of hypodontia in primary dentition

Answer 5

0.9%

Question 6

most affected teeth

Answer 6

L5s, U2s, U5s, L incisors
excluding 8s
U1s hardly ever missing

Question 7

missing U2s prevalence

Answer 7

1-2% pop

around 20% of all missing teeth

Question 8

what are missing U2s associated with?

Answer 8

ectopic canines

esp palatally - don’t have guiding effect of U2 root - drifts mesially and gets tucked behind 1

Question 9

broad etiological categoriesx3

Answer 9

multifactorial

• non-syndromic
• syndromic
• environmental

Question 10

non-syndromic aetiology

Answer 10

mutations in at least 3 genes associated with missing teeth in non-syndromic hypodontia
familial
sporadic

Question 11

syndromic aetiology

Answer 11

>100 craniofacial syndromes associated with hypodontia
CLP
Van der Woude syndrome
Down syndrome
anhydrotic ectodermal dysplasia
 - ectoderm doesn't develop properly
 - lack of sweat glands and body hair, severe              
   hypodontia, v thin wispy blonde hair

Question 12

environmental aetiology

Answer 12

trauma
radiotherapy/chemotherapy

Question 13

presentation

Answer 13

• delayed or asymmetric eruption
• retained or infra-occluded deciduous teeth
• absent deciduous tooth
  • if primary tooth missing permanent likely to be too as permanent tooth germ develops from the primary tooth germ
• tooth form

Question 14

what should you do if you suspect hypodontia?

Answer 14

refer early

Question 15

main associated problem x1

Answer 15

microdontia

Question 16

associated problems

Answer 16

microdontia
malformation of other teeth
short root anomaly
impaction (esp U3)
delayed formation and/or delayed eruption of other teeth
crowding and/or malposition of other teeth
U3/4 transposition
taurodontism
enamel hypoplasia
altered CF growth

Question 17

taurodontism

Answer 17

elongated pulp chambers

Question 18

potential problems

Answer 18

spacing
drifting
over-eruption
aesthetic impairment
fct problems (less common as PC)
Deep OB/ reduced LFH

Question 19

hypodontia care pathway

Answer 19

GDP recognition
referral to specialist orthodontist
in GDH - initial assessment in ortho and allocate when appropriate to a hypodontia clinic (ortho and Rx input)

Question 20

keys to successful management

Answer 20

interdisciplinary team (joint appt)
joint assessment and tx planning with precise aims
joint collaboration at transitional stages of tx
follow up of treated cases - learn what is best and deal with any problems as they arise

Question 21

assessment and planning

Answer 21

history
EO exam
IO exam
 - orthodontic aspects
 - restorative aspects
investigations
problem list
definitive plan
retention/maintenance

Question 22

investigations

Answer 22

study models
planning models - kesling, diagnostic
 - simulate tooth movement
 - planning
 - show pt what could potentially be achieved
radiographs - often OPT +/- other IOs
photographs
CBCT

Question 23

missing U2s - options

Answer 23

accept
restorative alone
ortho alone
combined ortho and restorative (most common)

Question 24

basic options for combined treatment

Answer 24

open space
close space

Question 25

opening space

Answer 25

implant autotransplantation e.g. crowded premolar in palate RBB conventional bridgework - a bit destructive RPD / overdenture

Question 26

close space types x2

Answer 26

* simple - ortho used just to close space * space closure plus - close space ortho - position teeth in a way to make Rx work easier - Rx tx

Question 27

plan of choice should:

Answer 27

satisfy expected **aesthetic** objectives least invasive satisfies expected **functional** objectives - immediate - long-term (65+ years)

Question 28

in case of missing U2, why retracting canines for RBB needed

Answer 28

canine often erupts next to central if retained c as pushes it to erupt where lateral missing

Question 29

retention after retracting canines

Answer 29

* high relapse potential if have retracted canine a lot or if rotated * RBB ends up buccally outside line of arch if insufficient retention * often need TAD (temporary anchorage device)

Question 30

which bridge design has better success?

Answer 30

cantilever design - less failure if debond - but more relapse potential

Question 31

RBB ideal abutment

Answer 31

canine - less shine through of metal wing - root length - crown dimensions - (but) might fail due to canine guidance/ excursion movement

Question 32

advantages of RBB

Answer 32

``` relatively simple (short timescale) do when young (complete tx) non-destructive can look good place on semi-permanent basis (e.g. if future implant) ```

Question 33

disadvantages of RBB

Answer 33

``` technique sensitive - operator important failure rate appearance sometimes not good (try again, new materials) ortho retention needs are high maintenance ```

Question 34

opening space for implant

Answer 34

* retract canine to give **7mm space** at level of gingival margin * can give **retainer with prosthetic tooth** until can get implant * leave good quality bone * need roots at correct angulation * stands alone - doesn't stress other teeth * CBCT

Question 35

RBB vs implant: key differences

Answer 35

cant do implant until at least 21-23yo (later for M) - pts grow vertically esp in anterior region need min **7mm space** root separation often need bone graft technically v demanding in aesthetic zone - can get recession and metal shine through significant extra time to do significant cost

Question 36

factors for simple space closure

Answer 36

tooth shape/size tooth colour - canines can be yellowy gingival architecture - central and canine higher, lateral lower

Question 37

how to make a canine look like a lateral

Answer 37

individualised **extrusion** of canine re gingival contour height relative to U1 significant reshape - do gradually so as not to threaten pulp bleaching - can use bleaching tray as retainer

Question 38

how to make a first premolar look like a canine

Answer 38

intrude U4 to give correct gingival architecture **Rotate mesially** to take up more space and so you don't see palatal cusp composite build up or veneer U4 to restore vertical height and "caninise" it

Question 39

space closure advantages

Answer 39

no prosthesis - relatively **low maintenance** good aesthetics with appropriate ortho and Rx techniques can be done at an **early age**

Question 40

When to refer

Answer 40

- abnormality in eruption sequence/ > 6mo diff of contra lateral - complete absence of space - severely infraoccluded primary tooth