Antibacterial Effect of Orthodontic Adhesive with Organic Nanoparticles

Orthodontic adhesives can accumulate biofilm, which may lead to long-term white-spot lesions; however, incorporating poly (lactic-co-glycolic acid) (PLGA) nanoparticles could improve their anticariogenic properties. Objective: To develop PLGA nanoparticles containing antiseptic agents for orthodontic adhesives, improve antibacterial activity against Streptococcus mutans, and assess cytotoxicity in gingival fibroblasts. Methods: PLGA nanoparticles with chlorhexidine and chitosan were synthesized and characterized using FTIR, SEM, and UV-Vis spectroscopy. Antibacterial activity was evaluated by agar diffusion and microdilution assays, and cytotoxicity and microhardness were also assessed. Results: PLGA-NPs showed moderate antibacterial effects, with inhibition rates from 74.25% to 54.05% in agar diffusion and reduced activity in microdilution (CC50: 3.75 µg/mL in adhesive, 15 µg/mL free). PLGA-NPs-CHx exhibited stronger antibacterial activity, with inhibition ranging from 89.38% to 73.75% and a CC50 of 0.93 µg/mL in both forms. PLGA-NPs-CH also showed significant inhibition (83.11% to 69.39%) and a CC50 of 1.87 µg/mL in adhesive and 7.5 µg/mL free. Vickers microhardness values were similar across groups: 74.67 HV for adhesive only, 74.11 HV for adhesive with PLGA-NPs, 74.22 HV for PLGA-NPs-CH-Adh, and 74 HV for PLGA-NPs-CHx-Adh. Conclusions: Incorporating PLGA nanoparticles functionalized with antiseptic agents into orthodontic adhesives shows promising antibacterial potential and may benefit orthodontic practice.