Preformed metal crowns Flashcards
What is another name for preformed metal crowns
Stainless steel crowns (but they are actually made of nickel chrome)
What are preformed metal crowns?
For children (deciduous and permanent teeth)
No impressions, no lab stage
Pre-contoured and pre-crimped
How many sizes (3M ESPE)
6 different sizes per tooth
Sizes 2-7
Size located on buccal aspect
When to use PMC on primary teeth
Teeth with large or multi-surface carious lesions (most common)
Pulp treated teeth (full seal, big hole, brittle because no fluid in dentinal tubules)
Trauma (rare: big fractures)
Enamel and dentine defects
Abutment for crown-loop space maintainer
Infraoccluded teeth (sinking) to maintain mesial/ distal space
Teeth with severe wear (if you can get crown on)
Abutment
Structure built to support the lateral pressure of an arch or span
When not to use PMC on primary teeth
Unrestorable tooth (too broken down or dead) Failed pulp therapy Soon to exfoliate Pre-cooperative Severe space loss Poor motivation? Multiple grossly carious teeth
When to use PMC on permanent teeth
Hypomineralised molars Amelo- and dentinogenesis Temporary restoration Severe erosion To keep space for ortho
Advantages of PMCs
Straightforward technique
Quick and cheap
Evidence of excellent longevity, low failure rates, compare well with other materials
Failure, if occurs, if easily corrected
Disadvantages of PMCs
Poor aesthetics
May impede eruption of adjacent teeth if too big
May cause gingival inflammation if cement not removed completely
Theoretical nickel allergy risk
Evidence for PMCs: Einwag and Dunninger (1996)
LEARN ONE
Longitudinal study of 66 pxs
- PMC paired with amalgam restorations on contralateral teeth
- 4.5 year survival rate was >90% for PMCs but <40% for amalgam
- only 6% of PMCs required replacement, but 58% of amalgams
Evidence for PMCs: Randall, Vrijhoef and Wilson (2000)
LEARN ONE
SR, 10 studies from 1975-1997, duration 1.6-10 years
Failure rate 1.9-30.3% for PMCs vs 11.6-88.7% for amalgam
PMCs had greater longevity, reduced retreatment need
All studies favoured treatment with PMCs
Barriers
Lack of training, esp. undergrad
Reluctance to administer LA to children
Difficulties in prep in young children
Perceived reaction by parents
Selling them
Parent's often don't like the look of them Children love them -princess/ Barbie teeth -tooth jewellery -pirate tooth -iron man tooth -bling
Things to tell px/ parent
They stay on until tooth falls out
Need to be brushed like normal teeth
Glue tastes like lemons/ salt and vinegar crisps
They feel a bit funny to bite on to start with
Conventional technique: you will need
Pointy bur (Xmas tree) Whole box of crowns Topical/ LA Diamond burs Cement Dental tape - knotted Maybe: -rubber dam -crown scissors -crimping pliers -ortho band seater