Arginine-modified orthodontic resin cement inhibits cariogenic bacterial-fungal co-adherence and enamel hardness loss.

OBJECTIVE: The co-adherence of Streptococcus mutans (S. mutans) and Candida albicans (C. albicans) is frequently observed in orthodontic patients and synergistically contributes to the development of white spot lesions (WSLs). This study aimed to develop an arginine-modified orthodontic adhesive and investigate its mechanical properties, ability to reduce cariogenicity, and effectiveness in preventing enamel hardness loss induced by bacteria-fungal co-adherence. MATERIALS AND METHODS: l-arginine was incorporated into orthodontic resin-modified glass ionomer cement (RMGIC) at mass fractions of 1.5 %, 3 %, and 5 %. Curing and mechanical properties were assessed using Fourier transform infrared Spectrometer (FT-IR) and shear bond strength (SBS). Antimicrobial efficacy was evaluated based on the metabolic activity and lactic acid production of a saliva-derived inoculum. Inhibition of S. mutans-C. albicans biofilm co-adherence on the material was assessed using confocal laser scanning microscopy and colony-forming unit (CFU) assays. Protection against enamel hardness loss was investigated using the Knoop microhardness test. RESULTS: FT-IR and SBS results demonstrated that incorporating up to 3 % arginine into RMGIC did not compromise its clinical performance. The cumulative arginine release increased with higher arginine concentrations and plateaued after 3-7 days. The incorporation of arginine significantly decreased metabolic activity and lactic acid production, inhibited the co-adherence of S. mutans and C. albicans, and mitigated enamel hardness loss around brackets. CONCLUSION: RMGIC with 3 % arginine exhibited optimal antimicrobial effects, reducing biofilm co-adherence and enamel hardness loss while maintaining clinically acceptable bond strength. CLINICAL SIGNIFICANCE: Incorporating arginine into orthodontic RMGIC may inhibit carious lesions around brackets.