Objectives: The purpose of this study was to explore the factors influencing time to re-intervention on teeth restored with crowns. These include dental factors such as tooth position and crown type, patient factors such as age, sex, and charge-paying status, and dentist factors including age, sex and country of qualification.
Methods: A modified version of Kaplan-Meier statistical methodology was used to plot re-intervention curves for different sub-groups within the overall population of restorations on adult patients.
Results: All-metal crowns had the longest expected interval before re-intervention (68% remaining without re-intervention after ten years) followed by metal-ceramic (62% after ten years) and then all-porcelain (48% after 10 years). Canine teeth had shortest survival time to next intervention, followed by incisor teeth. Teeth with root fillings and/or posts and cores had shorter crown re-intervention intervals than those without. Older dentists provided crowns which lasted longer before re-intervention than those placed by younger dentists, but there were no differences between male and female dentists. Dentists from outside Europe placed crowns which lasted longer till re-intervention than those graduated within Europe, or who entered by the statutory examination. Crowns placed for patients aged 30 to 59 consistently out-performed those for older and younger patients. Crowns for charge-paying patients outlasted those for patients whose treatment was free.
Conclusions: Type of crown, tooth position and both dentist and patient factors have been identified and quantified as being related to variation in survival time of crowns from placement to next intervention. Acknowledgment. The support of the Dental Practice Board, Eastbourne, UK, is acknowledged.