Abstract
Multiple side effects related to bleaching were found to occur in the dental pulp tissue, including decreased cell metabolism and viability. In this work we evaluated the in vitro diffusion capacity, cytotoxicity and biocompatibility of four commercial bleaching products on stem cells from human dental pulp (hDPSCs). Two commercial bleaching gels hydrogen peroxide-based (HP), Norblanc Office 37.5% (Nor-HP) and Opalescence Boost 40% (Opal-HP) were applied for 30 min to enamel/dentine discs. Another two gels from the same manufacturers, 16% carbamide peroxide-based (CP), Norblanc Home (Nor-CP) and Opalescence CP 16% (Opal-CP), were applied for 90 min. The diffusion of HP was analysed by fluorometry. Cytotoxicity was determined using the MTT assays, the determination of apoptosis, immunofluorescence assays and intracellular reactive oxygen species (ROS) level. Tissue inflammatory reactions were evaluated histopathologically in rats. Statistical differences were performed by one-way ANOVA and Bonferroni post-test (α < 0.05). Normon products showed lower cytotoxicity and diffusion capacity than the Ultradent products. A high intracellular ROS level was measured in hDPSCs after exposure to Opal-HP. Finally, a severe necrosis of both coronal and radicular pulp was observed with Opal-HP. Similar concentrations of hydrogen peroxide and carbamide peroxide in a variety of bleaching products exhibited different responses in cells and dental pulp tissue, suggesting that bleaching products contain unknown agents that could influence their toxicity.
Highlights
In 1989, Haywood and Harald Heymann introduced vital tooth whitening with a research paper called ‘Nightguard vital bleaching’
We demonstrated that there are some variations in the homovanillic acid dimer (HD) formation when compared the different bleaching products
To determine whether the different bleaching products possess cytotoxic effects on Human DPSCs (hDPSCs), we studied the induction of cell death on hDPSCs after exposition with the distinct bleaching eluates by analyzing Annexin-V and 7-AAD staining, an analysis frequently employed to distinguish between necrotic and apoptotic cells
Summary
In 1989, Haywood and Harald Heymann introduced vital tooth whitening with a research paper called ‘Nightguard vital bleaching’. The paper opened up a new research line as many researchers looked into new techniques[3], leading to the introduction of several new whitening products, most used hydrogen peroxide (HP) or carbamide peroxide (CP) as their basis, applying the same directly by means of mouth guards or strips or directly applied[4]. For in-office procedures, bleaching agents (HP 25–40% or CP 35%) are applied for shorter time periods[5,6]. It has been reported that dental pulp plays a primary role in the regenerative response after an injury or trauma by secreting tertiary dentin and contributing to the differentiation of stem cells from dental pulp (DPSCs) into odontoblast-like cells[17,18]. As DPSCs can be obtained from tooth under local anesthesia and without damage, they are the ideal seeding cells for medicine regenerative research and cytotoxic studies[20]
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