Comparison of fit and trueness of single-unit and short-span fixed dental restorations fabricated by additive and subtractive manufacturing - A systematic review and meta-analysis

Objectives: Numerous studies have been conducted on the adaptation of dental restorations fabricated by additive (AM) and subtractive manufacturing (SM); however, the results are conflicting. This systematic review and meta-analysis aimed to evaluate the fit and trueness of fixed restorations made by AM compared to SM.

Data: Studies investigating internal fit, marginal fit, and trueness of fixed prostheses were involved.

Sources: The protocol was registered in PROSPERO (registration number CRD42022323090). An electronic search was performed with a predefined search query across four medical databases on the 6th of September 2023.

Study selection: A total of 57 eligible studies were included and sub-grouped by material type (metals, ceramics, acrylic resins, composites). The outcomes were specified as internal fit, marginal fit, and trueness expressed in micrometer (µm). Further subgrouping was based on measurement area: axial, occlusal, and marginal. When we analyzed marginal fit, there were no statistically significant differences between the two techniques in any of the subgroups. The measurement of internal fit metal and ceramic restorations provided no significant differences. However, milled acrylic resin restorations showed a significantly higher occlusal gap compared to 3D printed prostheses with 39.12 µm (95% CI: 12.44; 65.79). In the case of trueness, a statistically significant difference was observed between ceramic AM and SM restorations with -47.76 µm (95% CI: -95.51; -0.00). QUIN and GRADE Pro tools were used to evaluate the risk of bias and certainty of evidence.

Conclusion: Fixed restorations manufactured with additive manufacturing are valid alternatives to subtractive manufacturing in the digital workflow.

Clinical significance: Additive manufacturing is an accurate and cost-effective manufacturing method of digital workflow, especially for metal and resin fixed restorations. Once the challenges in ceramics manufacturing are addressed, AM will show more significant promise in the field.