Research on The Bending Strength of Dental PMMA.

The research on the bending strength of dental PMMA mainly focuses on reinforcing materials, preparation processes and testing conditions. The following is a detailed analysis:

The influence of reinforcing materials on bending strength

Inorganic nanoparticles: Zirconium dioxide (ZrO₂) nanoparticles can significantly enhance the flexural strength of PMMA at a weight ratio of 3% to 5%. For instance, the flexural strength increases to 98.4MPa at a concentration of 3% and reaches 101.2MPa at 5%. Titanium dioxide (TiO₂) nanoparticles can enhance flexural strength at a concentration of 1.5%, but the effect weakens at high concentrations (such as 7%). Alumina (Al₂O₃) nanoparticles at a concentration of 16wt% (mixed in a ratio of 1:1:1 for sizes 40, 150, and 500nm) can achieve a flexural strength of 168.45MPa.

Fiber material: E-glass fiber can significantly enhance the bending strength within the concentration range of 3% to 7%. For instance, at a concentration of 7%, the bending strength can reach 105MPa. Pre-impregnated and silane-treated glass fibers can further enhance their flexural strength and impact strength. Polyethylene fibers, polyamide fibers (such as aramid), etc. can also enhance the flexural strength of PMMA, but they may affect hardness or aesthetics.

Other fillers: The combination of microcrystalline cellulose (MCC) and sisal fiber can improve the bending performance of PMMA, but the addition amount needs to be controlled to avoid a decrease in strength. In the composite material of antibacterial graphene oxide nanosheets (nGO) loaded with crystalline curcumin (CUR), TiO₂ nanoparticles can significantly enhance the flexural strength.

The influence of the preparation process on the bending strength

Copolymerization modification: By copolymerizing with monomers such as butyl methacrylate (BMA) and isobutyl methacrylate (IBMA), the flexural strength and modulus of PMMA can be significantly enhanced. For instance, a 40% concentration of IBMA copolymer can bring the bending strength to its maximum.

Nanocomposites: The PVP/ZrO₂ composite nanofibers prepared by electrospinning technology, when combined with PMMA, can significantly enhance the bending strength and toughness. For instance, the bending strength of PMMA/PVP/ZrO₂-10s samples has increased by 83%.

3D printing technology: The bending strength of 3D printed PMMA is affected by the printing direction (layer orientation). The bending strength of samples printed with 0-degree orientation is higher than that of samples printed with 45-degree and 90-degree orientation. In addition, autoclave polymerization can enhance the flexural strength of unmodified PMMA.

The influence of test conditions on bending strength

Test method: The bending strength of PMMA is usually determined by a three-point bending test. Parameters such as test speed and support point distance must comply with standards (such as ISO 178).

Environmental factors: Cold and hot cycles, water absorption and other factors may affect the bending strength of PMMA. For instance, the flexural strength of PMMA may decrease after cold and hot cycles, while the increase in water absorption may lead to the deterioration of material performance.