Tooth Preparation Assessment Criteria for All-Ceramic CAD/CAM Posterior Crowns: An Evidence Map.

Abstract

Background: An evidence map review was used to determine universal criteria for all-ceramic CAD/CAM posterior crowns to ensure standardized assessments by dental faculty, students, and practitioners.

Materials and methods: Covidence was used to perform the evidence map review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Web of Science (WOS), Embase, Dentistry and Oral Sciences Source (EBSCO), and MEDLINE (Ovid) were searched over a 10-year range (January 2012-December 2023), English only. This was complimented by a manual search. Descriptive statistics (i.e. frequencies and modes) and a chi-square goodness of fit test were used.

Results: A total of 640 articles were identified, out of which 73 were selected for review across six reduction parameters: occlusal reduction, axial reduction, finish line reduction, total occlusal convergence (TOC), preparation surface finish, and anatomic form. Zirconia was excluded from this analysis. Significant differences were found between the observed and expected frequencies of consolidated parameters associated with occlusal reduction and finish line shoulder parameters at the p ≤ 0.05 level. There were no significant differences found between the observed and expected frequencies of the consolidated reduction parameters associated with finish line chamfer, axial reduction, surface finish, or TOC (p > 0.05).

Conclusions: Recommendation parameters for all-ceramic CAD/CAM posterior crown preparations are 1.5-2.0 mm for the occlusal reduction and 1.0 mm for the reduction of the shoulder finish line. Recommendations of at least 1.0 mm for the chamfer reduction, 12° for the TOC, 1.0-1.5 mm for the axial reduction, and a smooth preparation surface finish with internally rounded angles were also made, though none of these results were statistically significant. The literature review revealed the "finish line" category is multi-dimensional suggesting a more encompassing term as "finish boundary profile (FBP)."