use of preformed metal crowns in paediatric

Question 1

what are preformed metal crowns

Answer 1

• no impressions
• no lab stage
• premade
• pre contoured (to fit gingival margin) and pre crimped (at cervical region to give fit over the crown)

Question 2

when to use preformed metal crowns

Answer 2

teeth with large or mutli-surface carious lesions
pulp treated teeth
trauma
enamel/dentine defects
abutment for crown loop space maintainer
infraocclued teeth to maintain mesial/distal space

Question 3

when not to use metal crowns

Answer 3

1) Unrestorable tooth
2) failed pulp therapy
3) soon to exfoliate

Question 4

cautions with preformed metal crowns

Answer 4

• severe wear/severe space loss
• not much room to place, or loss of crown height
• pre cooperative children, unable to sit in the chair
• poor motivation from the family, may be better to extract
• multiple grossly carious teeth (i.e. are you going to place 8 crowns on the teeth, children likely to get fed up, is there a better treatment plan eg extraction of some teeth)

Question 5

when to use for permanent teeth

Answer 5

useful to interum restorations

1) Hypomileralised molars
2) amelogeneisi imperfecta
3) dentiogenetis imperecta
4) temporary restoration
5) severe erosion

Question 6

advantages of PMC

Answer 6

1) straightforward technique
2) evidence of good longevity
3) low failure rates
4) compare well with other materials
5) failure if occurs is easily corrected
- write in notes what size so it falls out can be replaced

Question 7

disadvnatges

Answer 7

1) Poor aesthetics
2) may impede eruption of adjacent teeth if too big
- ensure big enough to cover whole tooth but smallest one possible
3) May cause gingival inflammation if cement not removed completely
4) theoretical nickel allergy risk

Question 8

barriers to PMC

Answer 8

1) Lack of training esp at undergraduate level
2) reluctance to administer LA to children
- worry it will cause pain or scare them
3) difficulties in preparation in young children
- need a cooperative child that sits still
4) perceived reaction by parents

Question 9

essential materials for PMC

Answer 9

• whole box of crowns
• topical/LA
• diamond burs
• cement
• dental tape – knotted

Question 10

airway protection

Answer 10

1) Child sitting slightly upright
2) rubber dam
3) gauze
4) adhesive handle

Question 11

technique

Answer 11

1) Topical and local anaesthetic
2) remove caries
3) pulpotomy/pulpectomy if needed
4) prepare tooth
5) select crown
6) adapt crown or modify prep
7) cement
Occlusal reduction
- Take 1mm off the cusps
- follow the contour of the cusps (to aid retention)

Question 12

adapting the crown

Answer 12

1) poorly adapted crown margins
- crimp
2) Space loss
- modify shape or use crown from opposite side and arch
3) gingival blanching
- will resolve
4) Occlusal discrepancies
- will resolve
- occlusion will adapt and level out

Question 13

Hall technqiue

Answer 13

• no tooth preparation
• no LA
• no try in
• not for extensively carious teeth (that need pulp)
• caries not removed but sealed into the tooth to isolate it from the mouth
• need tooth asymptomatic
• children not at risk of endocarditis
• pre operative radiograph (to make sure there is no intraradical infection)
• may need to use separators (to create space for the crown)
• airway protection
• occlusion will be raised, will settle

Question 14

technique steps for hall

Answer 14

1) If necessary place separators 1 week before
2) can use topical (optional)
3) choose crown
4) airway protection
5) try crown to contact point only
6) fill crown with glass ionomer cement
7) push down as far as possible
8) allow child to bite on band seater/cotton wool roll
9) remove excess cement with wet gauze
10) get child to bite together until cement sets
11) remove further cement with gause, excavator or probe
12) knotted floss between contact points
13) may be little uncomfortable afterwards
14) advice about analgesia
15) occlusion will be proper open but will settle