Antibacterial Activity of Experimental Gypsum-based Biomaterials as a Pulp Liner

Objective: The aim of this in-vitro study was to evaluate the antibacterial activity of experimental gypsum-chitosan (Gyp-CHT) biomaterials at different ratios. The results were compared with commercial pulp lining materials. Method: Chitosan (CHT) (Nova Matrix, Norway) was mixed with pure alpha-hemihydrate gypsum (Sigma Aldrich, USA) at ratios of  0%, 10%, 20%, 40% and 80%; to prepare a moldable Gyp-CHT biomaterials 190µL,  200µL, 300µL, 400µL and  600µL of distilled water (pH 6.5) were added to the above ratios respectively. For each ratio, a constant weight of 250 mg of Gyp-CHT powder was used.  The antimicrobial activity of the freshly mixed samples was tested by agar diffusion method using Mueller-Hinton agar (MHA) against the strain of Streptococcus mutans which were seeded on the MHA. Wells were made by removing agar at equidistant points. The experimental biomaterials were placed immediately into the wells after manipulation and preincubated for 2 h in room temperature followed by incubation at 37¢ªC in anaerobic condition. The means of inhibition zones were measured at 24, 48 and 72 h. Antibacterial effects of Ca(OH)₂ (Dycal, Dentsply, USA) and  glass ionomer cement (GIC) (GC Fuji lining LC, Japan) were compared with the experimental Gyp-CHT biomaterials as well. Each material was tested in triplicate and the measurements were obtained through three independent experiments. Data were analyzed using one-way ANOVA at level of p< 0.05. Result: Antibacterial activity was observed with all four ratios of Gyp-CHT biomaterials; significantly greater inhibition zones were observed with CHT concentration of 80%. The results of Gyp-CHT with 80% CHT were comparable with GIC; however Ca(OH)₂showed significantly higher antibacterial activity among the tested groups. Conclusion: Gyp-CHT biomaterials have shown potent antibacterial activity against Streptococcus mutans. Pure gypsum is biocompatible and would act as a promising scaffold to release the active antimicrobial components of chitosan.