Assessment of chitosan addition to at-home bleaching gel with and without calcium on the physical properties of tooth enamel

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Abstract
Dental bleaching is a widely used esthetic treatment, but concerns persist regarding its potential effects on enamel integrity. The incorporation of remineralizing and protective agents into bleaching gels, such as calcium and chitosan, has been proposed to mitigate these effects. Objective: This in vitro study evaluated the effects of adding 2% chitosan to at-home bleaching gels with and without calcium on enamel physical properties. Methodology: Bovine enamel specimens stained with black tea were assigned to five groups (n = 12): control (no bleaching), 7.5% hydrogen peroxide (7.5% HP), 7.5% HP + 2% chitosan (7.5% HP+ Chi), 7.5% HP + calcium (7.5% HP + Ca), and 7.5% HP + calcium + chitosan (7.5% HP + Ca + Chi). Bleaching was performed for 14 days (1 hour/day). Color (∆L*, ∆a*, ∆b*, ∆Eab, ∆E00, and ∆WID), surface roughness, and surface microhardness (SMH) were evaluated at baseline (T1) and after treatment (T2). Mineral content (Ca, P, and the Ca/P ratio) was assessed by energy-dispersive X-ray spectroscopy and enamel morphology by scanning electron microscopy. Statistical analyses included the Kruskal-Wallis and Dunn's tests, mixed models, and ANOVA. Results: Groups containing chitosan (7.5% HP + Chi and 7.5% HP + Ca + Chi) showed the lowest surface roughness and the highest microhardness values. For these groups, SMH showed no decrease after treatment (T2), remaining similar to the initial values (T1). Color changes were similar among all bleached groups. Calcium, phosphorus, and Ca/P levels were the same for all groups. Conclusion: Adding 2% chitosan to 7.5% hydrogen peroxide-based at-home bleaching gels appears to be a promising approach to protect enamel against changes in roughness, microhardness, and mineral content without compromising bleaching efficacy.

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