Human Dental Pulp Stem Cells Exhibit Different Biological Behaviours in Response to Commercial Bleaching Products

Abstract

The purpose of this study was to evaluate the diffusion capacity and the biological effects of different bleaching products on human dental pulp stem cells (hDPSCs). The bleaching gel was applied for 90, 30 or 15 min to enamel/dentine discs that adapted in an artificial chamber. The diffusion of hydrogen peroxide (HP) was analysed by fluorometry and the diffusion products were applied to hDPSCs. Cell viability, cell migration and cell morphology assays were performed using the eluates of diffusion products. Finally, cell apoptosis and the expression of mesenchymal stem cell markers were analysed by flow cytometry. Statistical analysis was performed using analysis of variance and Kruskal–Wallis or Mann–Whitney tests (α < 0.05). Significant reductions of approximately 95% in cell viability were observed for the 3 × 15 min groups (p < 0.001), while 1 × 30 min of PerfectBleach and 1 × 90 min of PolaNight resulted in reductions of 50% and 60% in cell viability, respectively (p < 0.001). Similar results were obtained in the migration assay. Moreover, the 3 × 15 min group was associated with cell morphology alterations and reductions of >70% in cell live. Finally, hDPSCs maintained their mesenchymal phenotype in all conditions. Similar concentrations of carbamide peroxide (CP) and HP in different commercial products exhibited different biological effects on hDPSCs.

Hydrogen Peroxide Diffusion through Enamel and Dentin

“…Diffusion capacity and the biological effects of different commercial bleaching products on human dental pulp stem cells ( h DPSCs) has been evaluated. The findings were that different commercial products with similar HP concentrations exhibited different biological effects on h DPSCs [ 35 ] than similar concentrations of CP and HP.…”

Increased whitening efficacy and reduced cytotoxicity are achieved by the chemical activation of a highly concentrated hydrogen peroxide bleaching gel

“…Therefore, to achieve effective dental color alteration in short periods, highly concentrated H 2 O 2 bleaching gels (35-40%) have been traditionally used for professional tooth-bleaching. 1 However, many studies have shown that such esthetic therapy allows diffusion of high amounts of H 2 O 2 through enamel and dentin, 4,5 causing in vitro [6][7][8][9][10][11] and in vivo [12][13][14][15] toxicity to pulp cells. Therefore, the "non-reacted H 2 O 2 " has been considered the main pathway for bleaching-induced tooth sensitivity, claimed by 80-100% of patients undergoing professional tooth-bleaching performed with high-concentrated gels.…”

“…[12][13][14][15][19][20][21] Recent demonstrations show H 2 O 2 from bleaching gels induces pro-inflammatory cytokine release by pulp cells, negatively influencing their long-term regenerative potential. 8,11,14,15,22 Therefore, many alternative therapies have been proposed to increase the biocompatibility of in-office bleaching therapy with the pulp-dentin complex, mainly aimed at reducing the amount of H 2 O 2 capable of reaching pulp cells. 18 Several authors have reported that reducing the H 2 O 2 concentration in bleaching gels and the period of contact of these dental products with enamel may decrease the in vitro and in vivo toxicity caused by these esthetic therapies.…”

Cytotoxic Effects of Zoom® Whitening Product in Human Fibroblasts

“…Because the tooth is a semi-permeable structure, whitening agents applied at the tooth surface can diffuse and reach the dental pulp, promoting damage to dental pulp cells, such as a decrease in cell viability and metabolism, inflammatory response, DNA damage, apoptosis, or even necrosis [9,10]. These cytotoxic effects are directly proportional to the concentration of HP applied and cell damage relates to tooth sensitivity, the most clinically related adverse effect of tooth whitening [11].…”

“…Manufacturers try to overcome this issue by adding desensitizing, stabilizing, or antioxidant agents to the formulation of whitening products, thus promoting protection from oxidative stress for dental pulp cells and preventing tooth sensitivity [12]. However, the exact composition of these products is often unknown, and thus the ability of these other components to protect cells from oxidative stress may vary, contributing to different in vitro and in vivo biocompatibility reports [9].…”