Retrospective clinical evaluation of ceramic onlays placed by dental students

Statement of problem. Indirect restorations with partial or complete occlusal surface coverage have been recommended to restore teeth with weakened walls in order to prevent cusp fracture. The success of these restorations when performed by dental students is unknown. Purpose. The purpose of this retrospective study was to evaluate the clinical performance of adhesively bonded ceramic onlay restorations placed by third- and fourth-year dental students. Material and methods. Sixty-five ceramic onlays were placed in patients between 2009 and 2015. The onlays were laboratory or chairside fabricated with a computer-aided design and computeraided manufacturing (CAD-CAM) system, using either IPS e.max Press or IPS e.max CAD. An adhesive technique and luting composite resin agent were used to cement the restorations. Thirty-seven onlays were evaluated clinically using the modified United States Public Health Service (USPHS) criteria. Data were statistically analyzed using the Cox proportional hazards model to compare tooth type and failures and the Fisher exact and McNemar tests to compare the USPHS criteria for significant differences (alpha=.05). Survival probability was calculated using the Kaplan-Meier algorithm. Results. Five onlays were considered to be failures and needed replacement. According to the Kaplan-Meier analysis, the estimated survival rate was 96.3% after 2 years and 91.5% at 4 years. All 5 of the failures occurred on molars (13.5%) and none on premolars (P=.025). A statistically significant difference was found for marginal discoloration between onlays placed within 0 to 3 years and 3 to 6 years (P<.05) but no differences between any other criteria. Conclusions. Ceramic onlays placed by dental students demonstrated acceptable long-term clinical performance.