Background Bamboo fiber is a widely produced natural plant fiber, with mechanical properties comparable to those of glass fiber, making it a promising biomaterial.

Objective  To develop a bamboo fiber composite material characterized by low modulus and high strength, suitable for use in dental fiber posts.

Methods The bamboo fiber composite was prepared using resin transfer molding and randomly divided into two groups for mechanical and biocompatibility testing. The mechanical properties were evaluated in a control group, which remained unsterilized, and a sterilization group, which underwent sterilization in a high-pressure autoclave at 121℃ and 2.2 MPa for 30 minutes. A high-precision micromechanical testing machine was employed to assess changes in mechanical properties and fracture behavior pre- and post-sterilization, focusing on the load-displacement curves. Scanning electron microscopy was used to examine the surface and fracture morphologies before and after sterilization. Biocompatibility testing included CCK-8 cytotoxicity tests, cell cycle and apoptosis assays, and hemolysis tests. The CCK-8 cytotoxicity test divided samples into negative control groups with normally cultured cells, blank control groups with culture medium only, and experimental groups with various concentrations (25%, 50%, 75%, 100%) of bamboo fiber composite extracts. The cell cycle and apoptosis assays compared a 100% concentration extract group with a negative control group. The hemolysis test involved experimental groups with a 100% concentration extract, physiological saline as the negative control, and distilled water as the positive control, to further assess the biocompatibility of the bamboo fiber composite.

Results The non-sterilized control group exhibited a flexural modulus of (9 ± 2) GPa and a strength of (498 ± 95) MPa; the sterilized group showed a flexural modulus of (11 ± 4) GPa and a strength of (496 ± 30) MPa, with no significant difference between the two groups (P>0.05). Load-displacement curves indicated a more favorable fracture pattern in the control group, exhibiting gradient failure, unlike the brittle fracture observed in the sterilized group. Scanning electron microscopy revealed good integration of fiber and resin in both groups; the control group showed fiber pull-out, while the sterilized group exhibited cohesive fractures of the resin matrix. The CCK-8 assay revealed statistically significant difference in absorbance at 100% concentration of bamboo fiber composite extract compared to the control group (P<0.01), with the highest proliferative capability observed in the extract. Long-term cell cycle and apoptosis experiments showed that the 100% concentration extract maintained a favorable cell proliferation cycle without inducing apoptosis, demonstrating no significant difference from the control group (P＞0.05). Hemolysis tests demonstrated a hemolysis rate of 2.69% for the bamboo fiber composite extract, significantly lower than 5% and markedly different from the positive control (P＜0.01).

Conclusion The mechanical properties of the bamboo fiber composite material remain relatively stable before and after sterilization, exhibiting good biocompatibility and potential for application in dental fiber post manufacturing.