The pH of Bleaching Gels on the Structural and Biological Response of Dental Tissues: A Scoping Review

This scoping review aimed to map and synthesize the available evidence on the influence of the bleaching gel pH on the structural and biological responses of dental tissues.

A comprehensive search was conducted across five databases and one grey literature source. Studies comparing bleaching gels with acidic pH versus neutral or basic pH in human teeth, in both clinical and laboratory settings, were included. A total of 20,282 articles were identified, 72 were selected for full-text reading, and 22 studies met the eligibility criteria. Most studies evaluated bleaching efficacy, while others investigated tooth sensitivity, enamel surface alterations, and penetration of hydrogen peroxide into the pulp chamber. Among the four randomized clinical trials included, two studies reported that bleaching gels with an acidic pH were associated with a higher risk and intensity of tooth sensitivity compared to those with a neutral, stable pH. Laboratory studies consistently demonstrated greater enamel surface alterations and higher hydrogen peroxide diffusion with acidic pH levels (< 7 pH). However, a few studies found no significant differences related to pH.

The pH of bleaching gels plays a critical role in the biological and structural integrity of dental tissues. Although several in vitro studies highlight the risks associated with acidic gels, clinical data remain limited. Given the widespread use of acidic pH gels in dental practice, further randomized clinical trials are needed to determine their safety and to guide evidence-based recommendations on pH control in bleaching protocols.

Whitening gels with acidic pH can increase enamel alterations and hydrogen peroxide penetration, potentially leading to higher tooth sensitivity. However, clinical evidence is limited. Given their widespread use, further randomized clinical trials are needed to confirm risks and guide safer bleaching protocols.