Mechanical Properties of Additively Manufactured and Milled Interim 3-Unit Fixed Dental Prostheses

To 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.Sixty 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 CB [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).Survival rates among groups varied from 100% (Man, Mil and FL-Sh), 70% (FL-St), 50% (RS-Sh), and 20% (RS-Sh) (p0.001), respectively. Additional events were observed in 50% to 80% in FL-St, RS-St, and RS-Sh groups (p0.001). Man, FL-St, and RS-S showed lower mean static load resistance (p0.001). Fracture through the connector between tooth 35 and the pontic was the most prevalent type of failure.The manufacturing method, type of resin, and the printing mode had a significant influence on the mechanical properties of AM interim 3-unit FDPs.