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 specific 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 concentration 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 the flexural strength at a concentration of 1.5%, but the effect is weakened at high concentrations (such as 7%). Alumina (Al₂O₃) nanoparticles can achieve a flexural strength of 168.45MPa at a concentration of 16wt% (with sizes of 40, 150, and 500nm mixed in a ratio of 1:1:1).

Fiber material: E-glass fiber can significantly enhance the flexural strength within the concentration range of 3% to 7%, for instance, the flexural strength can reach 105MPa at a concentration of 7%. Pre-impregnated and silane-treated glass fibers can further enhance their bending 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 fibers can improve the bending performance of PMMA, but the addition amount needs to be controlled to avoid a decrease in strength. In the composite materials of antibacterial graphene oxide nanosheets (nGO) loaded with crystalline curcumin (CUR), TiO₂ nanoparticles can significantly improve the flexural strength.

The influence of preparation process on 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 example, a 40% concentration of IBMA copolymer can maximize the bending strength.

Nanocomposites: The PVP/ZrO₂ composite nanofibers prepared by electrospinning technology, when combined with PMMA, can significantly enhance the bending strength and toughness. For example, the bending strength of the PMMA/PVP/ZrO₂-10s sample 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 a 0-degree orientation is higher than that of samples oriented at 45 degrees and 90 degrees. 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 the three-point bending test. Parameters such as the test speed and the distance of the support points need to 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 bending strength of PMMA may decrease after cold and hot cycling, and the increase in water absorption may lead to the deterioration of material performance.