Objectives: To analyse the treatment provided, over 11 years of continuous data, when a re-intervention was considered clinically necessary on a tooth restored with a crown.
Methods: An age-stratified random sample of 84,844 adult patients was tracked, generating 47,474 records of teeth on which crowns were placed. These were matched against records of subsequent treatments of the same tooth and intervals to next intervention, recementing of crown, or extraction of tooth calculated. Modified Kaplan-Meier was used to produce survival curves for these different outcomes, by type of restoration.
Results: Over all the 10,426 teeth with re-interventions in the study period, 12% of the re-interventions involved root treatment, 36% recementing, 17% replacement crowns, 13% direct restoration, and 19% were extracted or replaced by dentures. The longer the interval since crown placement the higher the proportion of extractions or direct restoration and the lower the proportion of recementing. The data are dominated by bonded crowns, which comprised 83% of the crowns with re-interventions. Porcelain crowns were more often followed by a replacement crown (49%). Metal crowns had a lower proportion of recementing (22%)
Ten-year survival to recementing ranged from 90% for metal crowns to 85% for bonded crowns. The figures for survival to other re-interventions, censoring extractions, were 81% for metal, 77% for bonded crowns, and 58% for all-porcelain. The ten-year survival rates to extraction were 99% for metal and bonded crowns, and 92% for all-porcelain crowns.
Conclusion: The type of crown provides a useful indicator of the future survival of the restored tooth and the likelihood of early re-intervention.
The support of the Dental Practice Board, Eastbourne, UK, is acknowledged.