Clinical outcomes and influence of material parameters on the behavior and survival rate of thin and ultrathin occlusal veneers: A systematic review

Purpose: Various oral rehabilitation approaches are available for severely worn dentition. However, evidence-based guidelines for permanent treatment are limited. This review aims to investigate clinical observational findings and com-pare in-vitro outcomes of thin and ultrathin occlusal veneers using different materials and approaches.Methods: An electronic search of online databases, such as PubMed (MEDLINE), BioMed Central (BMC), Cochrane, and Scopus, was performed for the 2009 -Jun 2021 period, following the PRISMA 2020 criteria. The reports sought for retrieval were all the articles evaluating the clinical outcomes of permanent full-mouth rehabilitation, and all in-vitro records that investigated and compared fracture strength, survival rate, and modes of failure of ultrathin (0.3 -0.6 mm), thin (0.5 -0.8 mm), and thick (0.8-1.5 mm) occlusal veneer restorations, with regard to the available indirect restorative materials. The Newcastle Ottawa risk of bias criteria was used to judge the clinical studies and a modified consort statement was used for the evaluation of in-vitro studies. The data of the included studies were extracted and grouped based on the similarity of the outcomes and study protocols. Data heterogeneity determined the qualitative and quantitative grouping of the results. Results: Two clinical and 17 in-vitro studies were included. Data exhibited heterogeneity within the materials, variables, testing protocols and observation periods. Therefore, only qualitative synthesis of the results was feasible. Clinically used 1 mm lithium disilicate overlays and ultrathin one-step no-prep polymer infiltrated ceramic network (PICN) occlusal veneers exhibited very high success and survival rates. The analysis of in-vitro studies exhibited variable survival rates and fracture load values, based on materials, thickness, and restorative approaches used.Conclusions: Within the limitations of this systematic review, it can be concluded that the clinical outcomes of thin and ultrathin occlusal veneers/overlays are auspicious. In-vitro experimental results support the usage of the thin and ultrathin occlusal veneers.