Effect of polyimide addition on mechanical properties of PMMA-based denture material

The aim of the study was to evaluate the effect of modifying polymethyl methacrylate (PMMA) denture base material with polyimide (PI) on its flexural property and biocompatibility. Low molecular weight (1,500 g/mol) PI was synthesized and small amount of PI (0.4, 0.6, 0.8 and 1 wt%) was dispersed into the PMMA matrix. Three-point bending tests, scanning electron microscopy and thermal cycling were used to measure the mechanical properties, while MTT assay was used to evaluate the biocompatibility of the denture base material. The results showed that 0.6% addition of PI significantly increased flexural strength of PMMA denture base material by 13.5%, compared with the control group (p<0.05). Even after 5,000 hydrothermal cycling the reinforce effect still existed. However, when the PI content further increased, flexural strength of the denture base material decreased due to particle agglomeration. The MTT assay confirmed that the addition of PI did not change the biocompatibility of the PMMA denture base material. The present study suggested that blending polyimide in the proper proportion can be a potential method to strengthen the PMMA-based denture base material.