Evaluation of Flexural Strength of Milled versus Printed Provisional 4-Unit Fixed Dental Prostheses

Abstract

Aim of this study: The objective of this in vitro study was to evaluate the flexural strength of 4 – unit provisional poly-methyl methacrylate (PMMA) fixed dental protheses (FDPs) fabricated with two different methods. Materials & methods: Ninety-six 4- unit PMMA provisional FDPs were fabricated from 3 different PMMA materials. Group 1 (Form 3B+ CB resin) and Group 2 (Dentca CB resin) FDPs were printed using two different printers (Form 3B+ 3D and Carbon DLS respectively); while Group 3 (TelioCAD) FPDs were milled (Programill PM7). A 3-point bending flexural test was preformed using a universal testing machine. The force was applied at the center of the FDPs at a crosshead speed of 0.5mm/min until failure occured. The flexural strength data were calculated in megapascals (MPa) and analyzed by using Welch’s ANOVA. Post hoc analysis was performed using the Games-Howell test. Results: Milled Telio CAD (Group 3) FDP’S showed the highest mean flexural strength (0.33 ± 0.08 kN). Welch’s ANOVA results showed a statistically significant difference in mean load at fracture between group 1 (Form 3B+ CB resin) and group 3 (Telio, P<0.001) and between group 2 (Carbon) and group 3 (P < 0.001), but not between group 1 and group 2 (P=0.99). In terms of displacement, there was not statistically significant difference between any of the groups tested (P= 0.17) Conclusion: Telio CAD PMMA provisional 4-unit FDPs showed significantly higher flexural strength compared to the printed ones. However, displacement before breakage was not significantly different between any of the tested groups. This research provides insightful information to dental professionals on materials selection; even though further investigation into a broader range of materials and design is needed.