Plaque pH Modulating Agents

The dynamic equilibrium between demineralization and remineralization of tooth enamel is crucial for maintaining dental health. While acid production by cariogenic bacteria leads to enamel demineralization, the generation of alkaline substances within dental plaque can neutralize these acids, thereby promoting remineralization. Recent research highlights the critical role of alkali production, particularly via the arginine deiminase system (ADS) in certain oral bacteria, in maintaining plaque pH balance and reducing caries risk.^21-23 By metabolizing arginine into ammonia, these bacteria raise plaque pH, counteracting acid from carbohydrate fermentation and promoting remineralization over demineralization. Higher ADS activity is associated with lower caries incidence, while reduced alkali production correlates with greater caries risk.^21,22 Clinical studies support the use of arginine-containing oral care products to enhance ADS activity, increase ammonia production, and foster a less cariogenic oral environment, making this a promising strategy for caries prevention and management.²³

Xylitol, a naturally occurring sugar alcohol, has been widely studied for its ability to reduce dental caries through multiple mechanisms, including its impact on plaque pH. Unlike fermentable sugars, xylitol is not metabolized by cariogenic bacteria such as Streptococcus mutans, leading to reduced acid production in the dental biofilm. Moreover, xylitol may inhibit the growth and adhesion of S. mutans, which contributes to a healthier oral microbiome. A 2024 systematic review indicates that xylitol consumption, particularly in the form of chewing gum or lozenges, can increase plaque and salivary pH by stimulating saliva flow and reducing bacterial acidogenicity.²⁴ These effects support remineralization and help maintain a neutral to slightly alkaline environment, making xylitol an effective adjunct in caries prevention strategies.

Clinical investigations have revealed that individuals with higher salivary and plaque ADS activity tend to have a lower incidence of dental caries. Conversely, reduced alkali-generating capacity in oral biofilms is associated with increased caries risk. These findings suggest that enhancing alkali production in dental plaque could be a viable strategy for caries prevention.

Stannous fluoride (SnF₂), commonly used in fluoride dentifrices, has shown potential not only for its well-established anticaries and antimicrobial properties but also for its effect on plaque pH. The stannous ion (Sn²⁺) may inhibit acidogenic bacterial enzymes and reduce bacterial acid production, helping to stabilize plaque pH levels.²⁵ In some formulations, stannous fluoride is combined with sodium fluoride to enhance both remineralization and antimicrobial activity. Studies have also suggested that stannous-containing fluoride toothpaste may help create a less acidic environment in the plaque matrix, thereby supporting a shift toward a less cariogenic biofilm.^26,27 While more targeted studies are needed to isolate its alkalinizing effects, current data supports its role in reducing the cariogenic potential of dental plaque alongside its benefits for gingival health and enamel protection.

The inclusion of pH-modulating agents in oral care products, such as stannous fluoride and arginine, represents a strategic approach to caries prevention beyond mechanical plaque removal and remineralization. These agents may help support plaque pH homeostasis, inhibit acidogenic bacteria, and foster a biofilm less favorable to caries development. Continued research is essential to further understand their synergistic effects and optimize their use in clinical care.