Preformed metal crowns

Fiona GilchristClinical Lecturer in Paediatric

Dentistry

Aims

• To discuss the indications and contra-indications of preformed metal crowns

• To discuss different techniques for placing preformed metal crowns

Learning objectives

• Participants should:– Understand the reasons for using preformed metal

crowns

– Have knowledge of different preparation techniques

What are they?• Preformed metal

crowns

• No impressions, no laboratory stage

• Pre-contoured and pre-crimped

Preformed metal crowns (PMC)• 3M ESPE surgical grade

stainless steel primary molar crowns

• 6 different sizes per tooth (sizes 2-7)

• Size located on the buccal aspect

When to use… primary teeth• Teeth with large or multi-

surface carious lesions• Pulp treated teeth• Trauma• Enamel and dentine defects• Abutment for crown-loop

space maintainer• Infraoccluded teeth to

maintain mesial/distal space – height of the tooth is lower

…and when not to use in primary teeth• Unrestorable tooth

• Failed pulp therapy

• Soon to exfoliate

• Cautions– Severe wear / severe space loss– Poor cooperation– Poor motivation?– Multiple grossly carious teeth

When to use… permanent teeth

• Hypomineralised molars• Amelogenesis imperfecta• Dentinogenesis imperfecta• Severe erosion• Temporary restoration

Advantages of PMCs

• Straightforward technique• Quick and cheap• Evidence of excellent longevity, low failure

rates, compare well with other materials• Failure, if occurs, is easily corrected

Disadvantages

• Poor aesthetics• May impede eruption of adjacent teeth if too

big• May cause gingival inflammation if cement not

removed completely• Theorectical nickel allergy risk

Evidence

• Randall, Vrijhoef and Wilson (2000)

• Systematic review

• Ten studies, 1975 -1997, duration 1.6 - 10 yrs

• Failure rate 1.9 – 30.3% for SSCs vs. 11.6 – 88.7% for amalgam

• SSCs had greater longevity, reduced retreatment need

• All studies favoured treatment with SSCs

Selling them

• Parents often don’t like the look of them

• Children love them!– Princess/Barbie teeth– Tooth jewellery– Pirate tooth– Bling!

Things to tell the patient/parent

• They stay on until the tooth falls out• They need to be brushed just like normal

teeth• The glue tastes a bit like lemons/salt and

vinegar crisps• They feel a bit funny to bite on to start with

Patient/parent experiences

Special toothMy tooth feels betterMakes me feel like a

princess

I say I’m from Mars

I don’t really like the look of the

silver crowns but if they are helping my

son’s teeth then that’s all that

matters

Call it a pirate tooth

Child’s opinionWhat do you think about your silver

tooth?

I really like my silver tooth 64%

I don't mind my silver tooth 29%

I really hate my silver tooth 7%

Parent’s opinion

57%29%

7%

0% 7%

I have no concerns about how the silver crown looks

Strongly agee

Agree

No opinion

disagree

strongly disagree

Chris, age 5

Age 7, at follow-up, 2 years after completion of treatment

Conventional technique

You will need …

• Essential materials– Whole box of crowns – Topical/LA – Diamond burs – Adams pliers– Cement– Dental tape - knotted

You will need …

• Optional materials– Rubber dam– Crown scissors – Crimping pliers– Orthodontic band seater

Airway protection

• Child sitting slightly upright

• Rubber dam• Gauze• Adhesive handle

Innes et al. 2007

Technique

1. Topical/LA2. Remove caries3. Pulpotomy/pulpectomy if needed4. Prepare tooth5. Select crown6. Adapt crown or modify prep7. Cementation

Occlusal reduction

Mesial and distal reduction

Finishing touches

Select a crown

Adapt the crown / modify the prep

• Coping with: – Poorly adapted crown

margins – Space loss – Gingival blanching– Occlusal discrepancies

Cementation

• Choice of cement• Glass ionomer (Aquacem)• Polycarboxylate (Poly F)• Zinc oxide eugenol

(Kalzinol)

• Clotted cream consistency• Enough to fill the crown• Remove excess with

knotted floss

James, age 8

Liam, age 6

The Hall technique

The Hall Technique

• No tooth preparation• No local analgesia • No try-in• Not for extensively carious teeth• Caries not removed, but sealed into the tooth

to isolate it from the mouth

The Hall Technique

• Tooth asymptomatic• Child not at risk of endocarditis• Pre-operative radiograph• +/- separators• Airway protection• Occlusion

The Hall Technique

• Innes N, Evans DJP, Stirrups DR (2007)– Split mouth RCT– 132 children, aged 3-10– 17 GDPs in Tayside, Scotland– Clinical and radiographic follow-up

Main outcomes after 2 years

Innes and Evans (2007)

(n=124 conventionally treated teeth + 124 Hall teeth)

Dentists' estimation of discomfort experienced by child

(n = 132 children)

Innes, Evans and Stirrups (2007)

Patient/carer/dentist treatment preference

(n = 396 for 132 treatment events)

Innes, Evans and Stirrups (2007)

Technique

• If necessary place separators 1 week before

• Measure space • Topical• Choose crown• Airway protection• Try crown to contact

point only

Technique

• Fill crown with glass ionomer cement

• Push down as far as possible

• Allow child to bite on band seater/cotton wool roll

Innes et al. 2007

Technique

• Remove excess cement with wet gauze

• Get child to bite together

• Remove further cement with gauze

• Knotted floss between contact points

Patient instructions

• May be a little uncomfortable afterwards

• Advice about analgesia

• Occlusion will be propped open but will settle

Further reading• Innes N, Evans D. The Hall Technique. A child centred approach to managing the

carious primary molar. A Users Manual. University of Dundee. www.scottishdental.org/?o=1404

• Welbury R R, Duggal M S, Hosey M T. Paediatric Dentistry. Oxford Medical Publications, 2005, Ch 9.

• Kindelan SA et al. Stainless steel preformed crowns for primary molars, UK National Clinical Guidelines in Paediatric Dentistry. International Journal of Paediatric Dentistry, 1999; 9:311-314. http://www.bspd.co.uk/publications.html