![]() Sodium bicarbonate is mainly known as an abrasive substance in whitening toothpastes, but it is also sold as an active ingredient in OTC whitening gels. Sodium chlorite decomposes into chlorine dioxide and the active bleaching agent in the presence of acid. ![]() PAP, an organic peroxide, oxidizes chromogens without the formation of free radicals, due to epoxidation of molecules containing conjugated double bonds. Therefore, OTC teeth-whitening products on the market contain a range of other active ingredients, such as phthalimidoperoxycaproic acid (PAP), sodium chlorite or sodium bicarbonate. Within the European Union, products containing > 0.1% peroxides are not allowed for individual sale and their in-office use and prescription with individualized trays is limited to dentists. The mineral loss was found down to a depth of 250 μm below the enamel. In vitro studies have demonstrated demineralization effects, such as a reduction of the mineral content or changes in the calcium/phosphate ratio. Some studies report changes in the enamel surface caused by bleaching with peroxides, while others did not report any surface alterations. Nevertheless, it remains unclear whether the tooth enamel is damaged by bleaching procedures with peroxides. This effect is most likely due to microscopic surface damage of the enamel, allowing oxygen radicals to diffuse towards the dental nerve and damage cells, which leads to temporary dental nerve inflammation. However, it is known to temporarily increase teeth sensitivity, which affects 43% to 80% of patients after whitening their teeth with peroxides. Tooth-whitening with peroxides is generally considered a safe and effective procedure. Thus, these are broken down into smaller molecules and absorb fewer wavelengths of visible light, resulting in a lighter appearance of the teeth. ![]() Peroxides release highly reactive free radicals, leading to oxidization of organic chromophores, small molecules from coffee, red wine or tea. Peroxide-based products used for in-office bleaching are applied directly to the enamel surface in combination with a cheek retractor and protection of the soft tissue. It has a slower degradation rate compared to H 2O 2 and, since it is usually applied to the tooth surface via dental trays, it is in contact with the surrounding tissue for a longer period of time compared to H 2O 2. CP is used in different concentrations in both products for in-office treatment and home bleaching. Dental in-office bleaching systems are primarily based on hydrogen peroxide (H 2O 2) or one of its precursors, such as carbamide peroxide (CP). Beyond that, the market for over-the-counter (OTC) whitening systems has increased over the last years, due to a rising demand for easy and home-based aesthetic procedures. Tooth-whitening has become a highly sought-after in-office dental treatment. Bromelain treatment was neither cytotoxic, nor resulted in enamel surface alterations, and its whitening effect was less, yet still effective, compared to hydrogen peroxide. (4) The maximum effect achieved by all OTC bleaching agents was the removal of stains, whereas hydrogen peroxide was capable of further whitening the teeth. Bromelain was the only non-cytotoxic agent. Bromelain and PAP treatment showed no enamel surface changes, in contrast to hydrogen peroxide treatment, which showed very mild interprismatic dissolution. Hydrogen peroxide caused the greatest color difference. (3) The application of all whitening gels resulted in a greater color difference of the enamel (ΔE) in comparison to the negative control. ![]() Cytotoxicity of the tested substances was assessed based on the cell viability of primary human fibroblasts. Scanning electron micrographs (SEM) were taken to assess the enamel structure. Color measurements were performed with a spectrophotometer. (2) Human teeth (n = 60) were randomly assigned into 6 groups (n = 10), stained with coffee solution for 7 d, followed by a whitening period of 7 d with either placebo, bromelain, sodium bicarbonate, sodium chlorite, PAP or hydrogen peroxide. (1) This study investigated the whitening effect, cytotoxicity and enamel surface alterations induced by different over-the-counter (OTC) bleaching agents in comparison to hydrogen peroxide. ![]()
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