Biocompatibility of polymethyl methacrylate heat-polymerizing denture base resin copolymerized with antimicrobial monomers

Statement of problem. Quaternary ammonium (QA)-based monomers such as dimethyl-hexadecyl-methacryloxyethyl-ammonium iodide (DHMAI) and 2-dimethyl-2-dodecyl-1-methacryloxyethyl ammonium iodine (DDMAI) have been investigated as copolymerizable monomers to impart antimicrobial activity to dental restorative and prosthetic materials. However, the biocompatibility of these antimicrobial monomers needs to be investigated in vivo before their clinical use. Purpose. The purpose of this study was to assess the in vivo biocompatibility of polymethyl methacrylate (PMMA) heat-polymerizing denture base resin copolymerized with varying concentrations of DHMAI and DDMAI. Material and methods. The toxicity and genotoxicity of the antimicrobial monomers (DHMAI 5 mu g/mL and DDMAI 20 mu g/mL) at 1 to 100 mu g/mL concentrations were investigated against zebrafish embryos (Danio rerio, n=10) using a zebrafish embryotoxicity test (ZET) or fish embryotoxicity test (FET) and comet assay, respectively. Further, DHMAI 5 mu g/mL and DDMAI 20 mu g/mL were incorporated into a conventional PMMA denture base system and a similar test was done on specimens of modified PMMA resin. For the evaluation of in vivo biocompatibility, modified PMMA specimens were subcutaneously implanted into Wistar rats (n=6) and biochemical, hematological, and histopathological parameters were investigated. Results were analyzed and compared using ANOVA and the Tukey post hoc test (alpha=.05). Results. Toxicity and genotoxicity studies using zebrafish embryos revealed that the incorporation of monomer to PMMA did not increase the toxicity, as confirmed by post-hour fertilization. Modified PMMA did not affect the hematological parameters, such as red blood cell (RBC) and white blood cell (WBC) except for the platelet count, which was significantly increased (P<.001), and the biochemical parameter, such as total protein (TP), blood urea nitrogen (BUN), serum glutamic-oxaloacetic transaminase (SGOT), triglyceride (TG), creatinine (Crea), total cholesterol, and serum glutamic pyruvic transaminase (SGPT), except for high-density lipoprotein (HDL) cholesterol, which was significantly decreased (P<.01). Histopathologically, no changes were observed in the sections of the liver, kidney, spleen, and subcutaneous tissues in the modified PMMA implanted rats. Additionally, no significant variation was found in the expression of immunohistochemical marker tumor necrosis factor alpha (TNF-alpha), confirming the noninflammatory response exerted by the modified PMMA on experimental rats. Conclusions. Zebrafish embryos treated with modified PMMA specimens demonstrated favorable biological properties and did not exhibit significant cytotoxicity and genotoxicity. Subcutaneously implanted modified PMMA did not cause any major hematological, biochemical, and histopathological alterations in Wistar albino rats, thus confirming the biocompatibility of PMMA heat-polymerizing denture base resin incorporated with DHMAI and DDMAI for dental applications.