The durability of primary molar restorations: II. Observations and predictions of success of stainless steel crowns.

As part of a large retrospective study of the durability and lifespan of 2229 restorations in primary molars of 226 pediatric patients attending a dental school clinic, the histories of first-placement stainless steel crowns were examined. The histories of crowned primary molars in 131 patients were followed for up to 9 years, computerized, and their durability assessed in terms of crown replacements and length of service, using computer-appropriate definitions for failure and success. 0f331 crowns studied, 88% (N = 291, including 54 over formocresol pulpotomies) were successful either to tooth exfoliation or to the end of the study. The distribution of the 12% "true" failures (~ = 40, including 19 over formocresol pulpotomies) showed a decreasing occurrence with increasing age of the child at first placement. The relative risk (odds ratio)for failed crowns to be associated with a formocresol pulpotomy was high (3.97). The mean lifespan of failed crowns increased with placement age (15.3 months for children younger than years; 24.1 mon ths for 4-7 year olds; and 28.8 mon ths for those older than 7 years), while the mean lifespan of successful crowns was 68.2 months for children younger than 4 years. Use of this data pool allowed the statistical prediction that crowns placed in 4 year olds and younger show a success rate which is approximately twice that of Class II amalgams, for each year up to 10 years of service.