Longevity of Digital Restorations Performed in a Predoctoral Clinical Curriculum

Objectives: To evaluate the longevity of digital single-tooth restorations performed by dental students and factors potentially associated with longevity.
Methods: Following IRB approval, electronic records of patients who received a restoration fabricated using a digital impression and milled from a prefabricated ceramic block during a 52-month period were assessed. Longevity, calculated from restoration cementation date until the most recent re-evaluation, was evaluated based on: student provider year, tooth location (anterior, posterior), restoration type (crown, onlay), material (lithium disilicate, feldspathic porcelain, zirconia), and cement (adhesive, resin-modified glass ionomer (RMGI), self-adhesive). If any failures occurred, reasons for failure were recorded.
Results: One-hundred thirteen (113) digital restorations were appraised with mean longevity at the time of evaluation being 13.2 months and maximum longevity at 56 months (4.7 years). In addition, 14 of 113 restorations (12%) had failed with time to failure varying from 6 months or less (9 restorations) to 40 months for 1 restoration. Reasons for failure included open margin (57%), fracture (21%), or debond (21%). Across restorations, the majority were crowns (85%), placed on posterior teeth (73%), milled from lithium disilicate (67%), cemented with adhesive cement (54%), and placed by D4 students (85%). There was no association between longevity and student year, tooth location, or restoration type. In contrast, cement type was significantly associated with longevity (p=0.001) with adhesive cement demonstrating higher longevity than RMGI or self-adhesive cement. There was also a significant association with material type (p=0.001), with zirconia showing lower longevity; however, because zirconia was implemented into the curriculum later than the other materials a longer assessment period is needed.
Conclusions: Overall, the majority of restorations (88%) performed in a predoctoral clinical curriculum, using a completely digital workflow, were clinically acceptable and functional during the evaluation period of this retrospective record review. Supported by UMKC SOD Summer Scholars Program.