Denture base fabrication has advanced with the introduction of computer-aided design and manufacturing (CAD-CAM) techniques, such as subtractive milling and additive 3D printing. However, concerns persist regarding the mechanical performance of 3D-printed denture bases. This systematic review and meta-analysis aimed to evaluate and compare the flexural strength (FS), surface hardness, fracture toughness, and impact strength of 3D-printed denture bases with those produced by milling and conventional methods. A systematic search of PubMed, Scopus, Web of Science, and Cochrane Central was conducted up to March 2025 in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. In vitro studies comparing 3D-printed denture bases with milled or conventional heat-polymerized bases in terms of mechanical properties were included. The Joanna Briggs Institute (JBI) checklist for quasi-experimental studies was used. Data was extracted, and quantitative synthesis was performed where possible. Thirty-eight studies were included, comprising 562 specimens for FS and 231 for surface hardness. Meta-analysis revealed that milled denture bases demonstrated the highest flexural strength (MD = -1.11, 95% CI [-1.29, -0.93], p < 0.001) and surface hardness (MD = -26.49, 95% CI [-29.89, -23.10], p < 0.001) compared to 3D-printed bases. Conventional bases outperformed 3D-printed ones in most mechanical properties. Milled denture bases exhibited the highest FS (120–146 MPa), followed by conventional PMMA (95–119 MPa), while 3D-printed bases showed wider variability (28–128 MPa). Surface hardness (VHN), fracture toughness (MPa·m¹/²), and impact strength (kJ/m²) were also superior in milled bases. Statistical heterogeneity was present due to differences in materials, printing orientation, and post-curing protocols. Subgroup analysis based on printing orientation (0°, 45°, and 90°) partially explained this variability, showing higher FS in horizontally printed specimens. Although 3D-printed denture bases offer customization and production efficiency, their mechanical properties remain inferior to milled alternatives. Optimization of resin formulations, printing parameters, and post-processing protocols is essential to enhance their clinical performance. The main limitations were high heterogeneity among included studies, differences in material formulations, variability in testing standards, and the in vitro nature of most included studies. This review was registered in PROSPERO (CRD420250639092). There were no deviations from the registered protocol.

The purpose of this study is to systematically review the effect of printing layer thickness and build orientation on the marginal and internal fit of 3D-printed fixed dental prostheses (FDPs). A systematic search was conducted in PubMed, Scopus, Web of Science, and Cochrane Library up to August 2025 following PRISMA guidelines (PROSPERO: CRD42024591005). Comparative studies assessing the impact of layer thickness on marginal gap (MG), internal gap (IG), or absolute marginal discrepancy (AMD) of 3D-printed FDPs and crowns were included. Risk of bias was assessed using a modified CONSORT tool. Thirteen in vitro studies met the eligibility criteria. Thinner layers (20–50 μm), particularly at 50 μm, improved marginal and internal fit compared to thicker layers (100 μm). Intermediate build orientations (45°–60°) minimized discrepancies, while extreme orientations (0° and 90°) increased stair-stepping effects. Marginal gap values generally ranged from 40 to 120 μm, within clinical acceptability. Subtractive (milled) restorations consistently showed superior fit compared to additive manufacturing. Layer thickness and build orientation significantly influence the fit of 3D-printed FDPs. A layer thickness of 50 μm at intermediate build orientations (45°–60°) provides the best adaptation. Milling remains the gold standard for precision, although optimized 3D-printing parameters can achieve clinically acceptable accuracy. Optimizing 3D-printing parameters—especially using 50 μm layer thickness with intermediate build orientations—enhances the marginal and internal precision of FDPs. While 3D printing is suitable for provisional restorations, milled prostheses remain preferable for definitive restorations requiring the highest accuracy.

Background. Insufficient information exists regarding the fracture resistance and failure pattern of newly developed zirconia-reinforced lithium disilicate (ZL, Vita Ambria) onlays. This in vitro study compared the fracture resistance of two types of onlays: monolithic lithium disilicate (LD) and monolithic ZL. Methods. Forty-eight ceramic onlay restorations were fabricated on epoxy dies using a maxillary first premolar model. The samples were divided into two main groups: LD and ZL. Half of each group was subjected to thermomechanical fatigue loading (TML) using a chewing simulator. All the samples were cemented with self-adhesive resin cement. Subsequently, they were loaded until failure in a universal testing machine, and the fracture patterns and resistance were recorded. Results. Before TML, ZL demonstrated the highest statistically significant mean fracture resistance (499.76±34.14N) compared to LD (470.40±27.38N). After TML, ZL showed the highest non-statistically significant mean fracture resistance (429.27±131.42N), while LD’s mean fracture resistance decreased (377.31±62.18N). Conclusion. Monolithic zirconia-reinforced onlays demonstrated higher fracture resistance and a more favorable failure mode compared to LD. However, the impact of thermomechanical aging resulted in reduced fracture resistance for both materials, with a notable preference observed for ZL

This in vitro investigation evaluated the marginal fit of three pressable glass-ceramic onlay materials: a conventional monolithic lithium disilicate (IPS e.max Press, EM, ivoclar vivadent AG, Schaan, Liechtenstein) and two zirconia-reinforced glass-ceramics (Vita Ambria, VA, VITA Zahnfabrik, Bad Säckingen, Germany; Celtra Press, CP, Sirona Dentsply, Milford, CT, USA). A typodont maxillary first premolar was prepared for an intensive onlay design by a single operator using a milling surveyor. The master die was duplicated with silicone impressions to create 72 identical epoxy resin dies. Seventy-two onlays (n = 24 per material) were fabricated and adhesively cemented to their respective dies. Vertical marginal gaps were recorded under a stereo-electron microscope before and after thermomechanical loading (TML) in a chewing simulator. Data were analyzed with one-way ANOVA and Tukey’s post hoc tests for intergroup comparisons and paired t-tests for pre- versus post-TML values. All groups showed a significant increase in marginal gap following TML. VA exhibited mean gaps of 46.41 µm before and 57.28 µm after loading (p = 0.001). EM demonstrated 41.16 µm before and 46.63 µm after TML (p = 0.002). CP showed 45.70 µm before and 55.99 µm after TML (p = 0.003). Among the three materials, EM maintained the most accurate marginal adaptation both before and after simulated chewing. Despite the increases, all post-loading values remained within the clinically acceptable threshold for marginal discrepancy. These findings indicated that thermomechanical fatigue adversely affected the marginal integrity of pressable glass-ceramic onlays, including zirconia-reinforced formulations. Nevertheless, zirconia-reinforced ceramics (VA and CP) achieved marginal gaps comparable to conventional lithium disilicate and remained within acceptable clinical limits. IPS e.max Press provided the best overall fit, suggesting it may offer superior long-term marginal stability for onlay restorations.

Objective: Marginal fit is crucial for the success of glass-ceramic onlay restorations, but limited data exists on one pressable zirconia-reinforced lithium disilicate's (ZL) marginal fit. This in vitro study assessed onlays from two materials: monolithic lithium disilicate (LD) and newly developed monolithic zirconia-reinforced lithium disilicate (ZL). Material and methods: Twenty-four onlay ceramic restorations were constructed on epoxy dies, divided into LD and ZL groups, and cemented with self-adhesive resin. Vertical marginal gaps were measured with a stereo electron microscope. The samples underwent thermomechanical fatigue loading (TML) in a chewing simulator and were re-evaluated. Results: ZL had a non-significant mean marginal gap of 46.42 μm before TML (p=0.086) and a significant mean gap of 57.28 μm after TML (p=0.00). LD exhibited marginal gap values of 41.16 μm before TML and 46.63 μm after TML. Conclusions: Marginal gap values for onlays before and after TML within clinically acceptable ranges. The marginal gap before TML was not significantly affected by the materials, but TML negatively impacted the marginal gap for both materials