Volume 9 • 2022 • Issue 5

The Science of Tooth Whitening The “whitening reaction” is carried out by hydrogen peroxide-derived free radicals that break down large molecules in the dentine into smaller molecules that don’t absorb as much light. Unfortunately, hydrogen peroxide does not remain confined to the dentin and can reach the pulp chamber, by travelling through the dentinal tubules. Once it reaches the pulp, hydrogen peroxide has been shown to decrease cell proliferation, metabolism and viability, reduce pulp- reparative capacity, cause tissue necrosis and induce tooth pain. Findings of the Study Dr. Bozec’s study used an in-vitro model, which found that 5% and 16% concentrations of carbamide peroxide induces a 50% reduction in the percentage weight of organic content in enamel, making it more porous and susceptible to peroxide diffusion into dentin and pulp tissue. Home tooth-whitening kits, with high concentrations and long application times, can produce intense oxidative stress on both gingival fibroblast and pulp cells, associated with a severe reduction in cell viability. Recommendations Using lower concentrations of carbamide peroxide may reduce the harmful effects of tooth whitening. “People sometimes prefer higher concentrations because they can see the effect immediately,” says Dr. Bozec. “There isn’t a lot of knowledge among the public of the oral health impacts of cosmetic products like at-home tooth whitening.” He believes a compromise needs to be found between the concentration of carbamide peroxide used, exposure time, desired patients’ outcomes, and side effects experienced. “When I talk to dentists about the side effects of cosmetic treatments, whitening is seen as the healthier option for the tooth when compared to veneers.” Educating patients about the possible side effects of any treatment is part of how dentists can promote good oral health. “Our hope is that people will opt for a lower concentration of peroxide if they decide to use a tooth- whitening product as they are so much less harmful to your teeth,” says Dr. Bozec. Home tooth-whitening kits, with high concentrations and long application times, can produce intense oxidative stress on both gingival fibroblast and pulp cells, associated with a severe reduction in cell viability. Microscope image of tooth enamel. (Image courtesy of the Bozec Lab) References: 1. Redha O, Mazinanian M, Nguyen S, Son DO, Lodyga M, Hinz B, et al. Compromised dental cells viability following teeth-whitening exposure. Sci Rep 2021;11(1):15547. 2. Browne JT, Ng YN, Odlyha M, Gulabivala K, Bozec L. Influence of root maturity or periodontal involvement on dentinal collagen changes following Na OC l irrigation: an ex vivo study. Int Endod J. 2020;53(1):97-110 “Many home tooth-whitening products have such a high concentration of peroxide gel, sometimes as much as 35%, and yet, little is known about what it does to the inside of our teeth,” says Dr. Bozec. “We believe this is the first study of its kind to show the toxic effects of using a tooth-whitening agent.” The views expressed are those of the author and do not necessarily reflect the opinions or official policies of the Canadian Dental Association. 28 | 2022 | Issue 5 Issues and People