Palotie et al XXXXXXXXXXinvestigated the “survival” or longevity of teeth restorations in Finland. The data that were extracted from the electronic patient files of the Helsinki City Public Dental...

Palotie et al. (2017) investigated the “survival” or longevity of teeth restorations in Finland. The data that were extracted from the electronic patient files of the Helsinki City Public Dental Service (PDS) and prepared for analyses consist of 5542 restorations conducted on 3051 patients in 2002. Information about the size, type, and material for the restorations of each particular tooth as well as the dates of the placement, possible reintervention, and the patient’s most recent visit were recorded. The fate of the restorations was followed as long as the patient continued visiting the Helsinki City PDS, but no longer than the end of 2015. The researchers focused on the premolars and molars (excluding the wisdom teeth), one of their hypotheses being that the longevity of restorations in the premolars exceeds that in the molars. Dig into the data, plot the Kaplan–Meier curves for each type of teeth on the same graph, and comment on the differences. Use a log-rank test to compare the survival functions.