What are the long-term (≥12 months) benefits and harms of preformed crowns for decayed primary molar teeth?

Question:
What are the long-term (≥12 months) benefits and harms of preformed crowns for decayed primary molar teeth?
Clinical Answer:
Moderate-quality evidence indicates that preformed metal crowns, compared to conventional fillings, are less likely to develop major failure (on average, 20 versus 112 per 1000 children), pain (12 versus 83 per 1000 children), and discomfort associated with the procedure (134 versus 239 per 1000 children), when used for managing dental caries in primary molars of children over a 12 to 48-month period. Low-quality evidence suggested similar rates for the groups in terms of gingival bleeding over 12 months. No studies reported on satisfaction with treatment (parent-, child- or dentist-rated), or time to failure/need for re-treatment.

When crowns were compared with non-restorative caries treatments, there were no clear differences between groups in regards to major failure, discomfort associated with the procedure or gingival bleeding, but the evidence was very low quality and numbers of children small. No study reported on pain, satisfaction with treatment or time to failure/retreatment.