Micro-Computed Tomography Evaluation of Partial Indirect Adhesive Restorations: A Proof-Of-Concept Study on the Effect of Preparations and Traditional or Additive Cam Workflow

PURPOSE: This proof-of-concept study investigates the marginal and internal fit of lithium disilicate overlays produced using traditional and digital workflows. It also evaluates the influence of variables such as tooth preparation design and 3D printer type on the accuracy of the final restoration. MATERIALS AND METHODS: Two extracted maxillary third molars were prepared with two different self-centering preparations (C1 and C2). Impressions were obtained with both conventional polyvinylsiloxane and digital intraoral scanners. Two different 3D printers were employed in this study. Working models were fabricated using conventional plaster and resin-based 3D printing techniques. Lithium disilicate overlays were then produced using both lost-waxing and 3D-printing workflows. All overlays were seated on their corresponding prepared tooth and scanned using micro-CT to assess the marginal and internal fit. RESULTS: The findings of this study revealed that restorations produced via 3D printing demonstrated comparable accuracy in marginal and internal fit to those fabricated through traditional heat-pressing techniques. The flat preparation design (C1) resulted in a superior marginal accuracy of the restorations. Although some differences in marginal accuracy were observed between the two printers tested in this study, these differences consistently remained below 100µm. CONCLUSIONS: Within the limitations of this proof-of-concept design, both traditional and digital workflows are capable of producing lithium disilicate overlays with clinically acceptable accuracy. This study suggests that 3D printing represents a viable and efficient alternative to conventional techniques for fabricating indirect restorations in clinical practice.