Longevity of lithium disilicate indirect restorations in posterior teeth prepared by undergraduate students: A retrospective study up to 8.5 years.

Abstract Objectives To analyze retrospectively the clinical performance and survival of lithium disilicate inlays, partial crowns and crowns placed by undergraduate students. Methods 250 lithium disilicate posterior restorations (IPS™Emax Press) were evaluated. Mean service time was 6.6 years (79 months) with a maximum observation time of 8.5 years (102 months). Clinical performance was assessed using FDI Criteria. Descriptive statistics were used to display the distribution of the criteria. Success and survival of the restorations were calculated with the Kaplan Meier method. A Cox regression analysis was performed to detect influencing parameters for the survival or the success of the restorations. Results Survival and success rates of lithium disilicate indirect restorations were calculated at 6.6 years with 96.3 % and 93.8 %, respectively. After 8.5 years the survival rate was calculated with 94 % and the success rate with 83.8 %. 10 out of 250 restorations (4%) failed, while the main reasons for failure were fracture of material, debonding/loss of restoration, endodontic complications as well as recurrence of caries. A Cox regression analysis failed to show a correlation between restoration failure and the experience level of the students, an existing root canal treatment, type of tooth, bruxism or the use of rubber dam. Conclusions Lithium disilicate indirect posterior restorations demonstrate a high success and survival rate after a mean service of 6.6 years when placed by undergraduate students with different levels of experience. Co-factors influencing the survival or success rate of these restorations could not be identified. Clinical significance Lithium disilicate restorations show a good clinical performance up to 8.5 years when prepared by undergraduate students.