Summary evaluation of the fracture and repair bond strength of temporary restorations produced with additive manufacturing technology

Aim: The aim of this study is to evaluate the initial bending strength of 3 dimension printed temporary restorations and the effect of different surface treatments on the repair bond strength with a 3-point bending test. Materials and Methods: 50 samples of 25 mm × 2 mm × 2 mm in size were produced from methylmethacrylate-free photopolymer resin temporary material (GC TempPrint) with a 3D printer. Initial flexural strength was evaluated by 3-point breaking test on a universal testing machine (AG-IS, Shimadzu, Japan). The broken samples were randomly divided into 5 groups to apply different surface treatments. In the control group, no surface treatment was applied to the fracture surfaces (Group C). In other groups, sandblasting (Group G), sandblasting and silane bonding agent (GS), sandblasting with 50 µm Al2O3 particles (S), sandblasting with 50 µm Al2O3 particles and silane bonding agent (SS) were applied to the samples, respectively. Fractured surfaces were repaired with high-filling flowable composite (G-Aenial Universal Flo) and polymerized with a LED light device for 20 seconds. Repair bond strength was evaluated with a 3-point fracture test on a universal testing device. The data obtained were examined with oneway ANOVA and paired sample t-test. The surface treatments applied to the fractured surfaces were examined using a stereomicroscope (Olympus microscope bx50). Results: There was no statistical difference between early period fracture strengths according to groups (P>0.05). There is a statistically significant difference between repair bond strengths (P<0.05). The highest repair bond strength was obtained in Group SS and the lowest in Group C. Conclusion: It has been observed that silane application after sandblasting with Al2O3 is the most effective method in the repair process of 3 D printed photopolymer resin temporary material that does not contain methylmethacrylate. Keywords: Repair Strength, Printable Resin, 3D Production, Temporary restorations