Physicochemical and Mechanical Characterization of Two Self-Curing Composite Resins for Direct Provisional Prostheses

In this experimental in vitro study, both the physicochemical and mechanical properties of two self-curing dental composites were compared: Structur 3 (based on Bis-GMA) and Visco III (based on Bis-EMA), which are used for the direct fabrication of temporary dental prostheses. The properties evaluated included flexural strength, toughness, hydrophilicity (measured using the contact angle), density, microhardness, water absorption, and wear and scratch resistance. In terms of flexural strength, Structur 3 exhibited a higher value (127 ± 16 MPa) than Visco III (103 ± 25 MPa). In addition, the dental composite based on Bis-GMA showed a higher toughness (36.52 ± 9.20 mJ) compared to 16.55 ± 7.55 mJ for the dental composite based on Bis-EMA) and a greater displacement to fracture (2.50 ± 0.38 mm compared to 1.72 ± 0.38 mm). However, Visco III showed a higher microhardness (17.045 ± 0.93 HV0.5) compared to Structur 3 (8.10 ± 0.76 HV0.5) and a lower water absorption (11.2 ± 0.4 µg/mm³ compared to Structur 3). In wear tests, Structur 3 showed greater wear (0.047 ± 0.021 mm² wear channel area) compared to Visco III (0.031 ± 0.013 mm²). Density analysis showed that Visco III is denser (1.5917 ± 0.006 g/cm³) than Structur 3 (1.324 ± 0.005 g/cm³). Fractography analysis showed that both dental composites exhibited brittle fractures. Contact angle tests revealed a similar hydrophilicity of both dental composites with values below 90°. These differences in properties may be influenced by the filler composition of the two dental composites, as Visco III contains macro-fillers with elements such as aluminum and barium, which increase radiopacity. The conclusion is that Visco III is preferable in terms of durability and resistance, while Structur 3 is more suitable for applications that require flexibility, such as in provisional prostheses with pontics or in situations that require high esthetic quality.