Purpose: To investigate the accuracy of additive manufacturing (AM) by means of internal fit of fixed dental prostheses (FDPs) fabricated with two AM technologies using different resins and printing modes (validated vs nonvalidated) compared to milling and direct manual methods. Material and methods: Sixty 3-unit interim FDPs replacing the first mandibular molar were divided into 6 groups (n = 10): manual (Protemp 4), milled (Telio-CAD), and AM groups were subdivided based on AM technology (direct light processing (Rapidshape P30 [RS]) and stereolithography (FormLabs 2 [FL])) and the polymer type (P-Pro-C&B [St] and SHERAprint-cb [Sh]) (RS-St, RS-Sh, FL-St, FL-Sh). Validated (RS-Sh and RS-St) or nonvalidated (FL-St and FL-Sh) modes were adopted for AM. The specimens were scanned to 3D align (GOM inspect) according to the triple scan method. The internal space between the FDPs and preparation surfaces in four sites (marginal, axial, occlusal, and total) was measured using equidistant surface points (GOM Inspect). Statistical analysis was done using Kruskal Wallis and Dunn post-hoc tests. (α = 0.05). Results: One AM group (FL-Sh) and milling exhibited better adaptation compared to manual and RS-St at molar site (p < 0.05). FDPs with St resin (FL-St and RS-St) displayed bigger marginal space than milled, FL-Sh, and RS-Sh. The nonvalidated printing mode showed better mean space results (p < 0.05) with higher predictability and repeatability (p < 0.001). Conclusions:The AM interim FDPs tested provided valid alternatives to the milled ones in regard to their accuracy results. The printing mode, resin, and the AM technology used significantly influenced the manufacturing accuracy of interim FDPs, particularly at the marginal area. The nonvalidated printing mode with lower-cost 3D printers is a promising solution for clinical applications.

PurposeTo investigate the survival and mechanical properties of 3‐unit interim fixed dental prostheses (FDPs) made with additive manufacturing (AM) technology compared to milled and conventional manual fabrication.Materials and methodsSixty 3‐unit interim FDPs replacing the first left mandibular molar were divided in 6 groups (n = 10): manual (Man) (Protemp 4), milled (Mil) (Telio‐CAD Multi), and 4 additive manufacturing (AM) groups were subdivided into 4 AM technology subgroups: direct light positioning (DLP) (Rapidshape P30 [RS]), and stereolitography (SLA) (Formlabs 2 [FL]) and the type of printed interim polymer (P Pro C&B [St] and SHERAprint‐cb [Sh]) (RS‐St, RS‐Sh, FL‐St, and FL‐Sh). Survival and complications were assessed after thermomechanical aging. The surviving samples were tested for fracture resistance. Kaplan‐Meier test followed by log‐rank test to show differences between groups was used to calculate the survival and complication rates. For fracture strength, one‐way ANOVA and Tukey‐b post hoc test were used to compare groups. Descriptive statistics was used for failure modes and Pearson chi‐square to compare groups (α = 0.05).ResultsSurvival rates among groups varied from 100% (Man, Mil and FL‐Sh), 70% (FL‐St), 50% (RS‐Sh), and 20% (RS‐Sh) (p < 0.001), respectively. Additional events were observed in 50% to 80% in FL‐St, RS‐St, and RS‐Sh groups (p < 0.001). Man, FL‐St, and RS‐S showed lower mean static load resistance (p < 0.001). Fracture through the connector between tooth 35 and the pontic was the most prevalent type of failure.ConclusionThe manufacturing method, type of resin, and the printing mode had a significant influence on the mechanical properties of AM interim 3‐unit FDPs.