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The safety and efficacy of 'over the counter' bleaching products in the UK

Introduction EU council directive 2011/84/EU resulted in a demand for over the counter (OTC) bleaching products. The industry has latched onto this renewed demand by developing a range of non-hydrogen peroxide OTC products. Aims To determine whether non-hydrogen peroxide OTC whitening products available in the UK are safe and to determine the lightening effect of those products. Materials and methods A total of 21 extracted teeth (11 incisors and ten premolars) were collected and stored in chloramine-T solution. Five days before the study, all teeth were immersed in 5 ml of a standard green tea solution at room temperature (22±2 °C). Roots were sectioned from the teeth and cleaned using an ultrasonic bath. Teeth were then embedded in epoxy resin and sectioned inciso-gingivally to serve as paired test and control specimens. A positive control of 10% carbamide peroxide was used while saline was used as a negative control. Five OTC products were selected from two major British consumer outlets. Initially, products were applied to the teeth samples for two one-hour cycles, followed by the equivalent of one-week's application, according to the manufacturer's instruction. Samples were stored overnight in saline to minimise any effects of dehydration. Shades of teeth were taken blindly by a single trained clinician in a natural light environment against a grey background before and after application of the products. Vickers microhardness tests and scanning electron microscopy (SEM) analysis were undertaken. Results SEM analysis showed surface morphology alterations to varying degrees, with several samples demonstrating a distinct etching pattern post-exposure to the OTC products. Sample three ('Brilliant 5 minute kit') and sample five ('iWhite instant teeth whitening') produced the most extensive surface alterations. Samples three and five also resulted in a significant reduction (p = 0.008) in Vickers microhardness. Two OTC products resulted in a lightening effect less than the negative control saline, whereas two other OTC products resulted in a lightening effect greater than carbamide peroxide. Conclusion This study suggests that non-hydrogen peroxide OTC products have the potential to damage enamel and lighten teeth. The lightening effect of the OTC products is variable, however, it is most likely to occur in sodium chlorite based products.

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Greenwall-Cohen, J., Francois, P., Silikas, N. et al. The safety and efficacy of 'over the counter' bleaching products in the UK. Br Dent J 226, 271–276 (2019).

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