The Effect of Adding Chitosan Nanoparticle Into Resin Infiltrant on the Color and Surface Microhardness of the Treated Enamel

OBJECTIVE: Chitosan is a naturally derived polysaccharide with antibacterial and bioactive properties. This study evaluated the effect of incorporating chitosan nanoparticles into a resin infiltrant on the color change, microhardness, wettability, and penetration depth of the treated white spot lesions. MATERIALS AND METHODS: Twenty-four bovine central incisors were prepared and baseline color and microhardness were measured. Artificial white spot lesions were created and specimens were randomly received either a resin infiltrant or a resin infiltrant containing 0.25 wt% chitosan nanoparticles. Color and microhardness were reassessed after infiltration, after 7 days of coffee immersion, and following secondary demineralization. Resin penetration depth was evaluated using scanning electron microscopy, and surface wettability was assessed by contact angle measurement. Data were analyzed using repeated-measures analysis of variance and independent t-tests (α = 0.05). RESULTS: Chitosan incorporation significantly improved initial color of white spot lesions (p = 0.022); however, after coffee immersion, it caused greater color change (p = 0.003). Stepwise color changes did not differ significantly between the groups (p > 0.05). Although initial surface microhardness values were lower in the chitosan group, this group demonstrated a more stable hardness change after secondary demineralization (p < 0.001). Resin penetration depth and surface wettability were not significantly affected by chitosan addition (p > 0.05). CONCLUSIONS: Incorporation of chitosan nanoparticles improved initial masking ability and resistance to acid-induced hardness loss without compromising penetration depth or hydrophilicity of resin infiltrant over treated enamel. However, increased susceptibility to extrinsic staining highlights the need for further optimization to balance mechanical stability and long-term optical performance.