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

OBJECTIVE

To evaluate whether coating enamel with a polymeric primer (PPol) containing titanium tetrafluoride (TiF) before applying a bleaching gel with 35% HO (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, 6TiF, and 10TiF 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 Lab* system, ΔE, 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 HO 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, no difference was observed among groups 2TiF, 6TiF, and PC (p > 0.05). The ΔWI was similar between groups 2TiF and PC (p > 0.05). The ΔWI of group 6TiF was superior to PC (p < 0.05), and group 10TiF achieved the highest ΔE and ΔWI values (p < 0.05). Besides limiting enamel microstructural changes compared to PC, group 10TiF significantly increased the hardness of this mineralized dental tissue. The highest cellular viability occurred in 10TiF compared to the other bleached groups (p < 0.05). Trans-amelodentinal HO diffusion decreased in groups 2TiF, 6TiF, and 10TiF in comparison with PC (p < 0.05).

CONCLUSION

Coating enamel with a PPol containing TiF 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 promoted the best outcomes.