Mechanical Properties of Current Provisional Restoration Materials

Objectives: Current materials used to fabricate provisional restorations include bis-acryl (BA) composite resin and urethane-based dimethacrylate (UDMA). Their initial mechanical properties are very important, considering that provisional restorations are placed into function immediately after fabrication Moreover, due to increased polymerization shrinkage, some clinicians may rely solely on chemical polymerization (self-cure) of dual-cure materials, which may adversely impact initial mechanical properties. The objective was to compare initial mechanical properties of BA and UDMA materials and evaluate the impact of polymerization mode (self-cure vs dual-cure).
Methods: Three BA-based (TelioCS, ProtempPlus, IntegrityMultiCore) and 2 UDMA-based (TuffTemp, TempSmart) materials were evaluated. Beam (25x2x2mm) specimens were prepared and polymerized according to manufacturer’s instructions (N=10 beams/material). Additional specimens that were self-cured only were made for all dual-cured materials (IntegrityMultiCore, TuffTemp, TempSmart, N=10/material). Sixty min following polymerization, beams were subjected to a 3-point bend test. The flexural strength (FS), flexural modulus (FM), and work of fracture (WOF) were calculated and evaluated with a 2-factor ANOVA and Tukey’s post hoc, α = 0.05. SEM imaging of fractured surfaces was used to evaluate fracture and particle morphology.
Results: When chemically-cured only, dual-cure materials had a lower FS, FM, and WOF. When light-cured, dual-cure UDMA resins had a higher FM than BA-based resins. For materials with large, irregular shaped particles, fracture appeared to occur through the resin and particles. For materials with round and smaller particles, fracture appeared to occur through the resin. The WOF for materials containing nano-sized particles was significantly higher.
Conclusions: Regardless of resin type, dual-cure materials that are chemically-cured only demonstrate lower initial mechanical properties. Light-cured, dual-cure UDMA-based resins demonstrated the highest initial mechanical properties. Nano-sized particles appear to enhance the WOF of provisional restoration materials, irrespective of resin type. These factors should be considered when selecting provisional material, especially for longer-term restorations. Supported by UMKC SOD Summer Scholars program