Influence of coating dental enamel with a TiF 4 -loaded polymeric primer on the adverse effects caused by a bleaching gel with 35% H 2 O 2 .

Objective: To evaluate whether coating enamel with a polymeric primer (PPol) containing titanium tetrafluoride (TiF ₄ ) before applying a bleaching gel with 35% H ₂ O ₂ (35% BG) increases esthetic efficacy, prevents changes in morphology and hardness of enamel, as well as reduces the cytotoxicity from conventional in-office bleaching.
Materials and Methods: Standardized enamel/dentin discs were stained and bleached for 45 min (one session) with 35% BG. Groups 2TiF ₄ , 6TiF ₄ , and 10TiF ₄ received the gel on the enamel previously coated with PPol containing 2 mg/mL, 6 mg/mL, or 10 mg/mL, respectively. No treatment or application of 35% BG directly on enamel were used as negative control (NC), and positive control (PC), respectively. UV-reflectance spectrophotometry (CIE L*a*b* system, ΔE ₀₀ , and ΔWI, n = 8) determined the bleaching efficacy of treatments. Enamel microhardness (Knoop, n = 8), morphology, and composition (SEM/EDS, n = 4) were also evaluated. Enamel/dentin discs adapted to artificial pulp chambers (n = 8) were used for trans-amelodentinal cytotoxicity tests. Following the treatments, the extracts (culture medium + bleaching gel components diffused through the discs) were collected and applied to odontoblast-like MDPC-23 cells, which were assessed concerning their viability (alamarBlue, n = 8; Live/Dead, n = 4), oxidative stress (n = 8), and morphology (SEM). The amount of H ₂ O ₂ in the extracts was also determined (leuco crystal violet/peroxidase, n = 8). The numerical data underwent one-criterion variance analysis (one-way ANOVA), followed by Tukey's test, at a 5% significance level.
Results: Regarding the ΔE ₀₀ , no difference was observed among groups 2TiF ₄ , 6TiF ₄ , and PC (p > 0.05). The ΔWI was similar between groups 2TiF ₄ and PC (p > 0.05). The ΔWI of group 6TiF ₄ was superior to PC (p < 0.05), and group 10TiF ₄ achieved the highest ΔE ₀₀ and ΔWI values (p < 0.05). Besides limiting enamel microstructural changes compared to PC, group 10TiF ₄ significantly increased the hardness of this mineralized dental tissue. The highest cellular viability occurred in 10TiF ₄ compared to the other bleached groups (p < 0.05). Trans-amelodentinal H ₂ O ₂ diffusion decreased in groups 2TiF ₄ , 6TiF ₄ , and 10TiF ₄ in comparison with PC (p < 0.05).
Conclusion: Coating enamel with a PPol containing TiF ₄ before applying a 35% BG may increase enamel microhardness and esthetic efficacy and reduce the trans-amelodentinal cytotoxicity of conventional in-office tooth bleaching. The PPol containing 10 mg/mL of TiF ₄ promoted the best outcomes.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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