pH Neutralization

One of the most important factors in maintaining healthy teeth is pH. First, consider what pH means. It is a measure of acidity or alkalinity.

The lower the pH, the more acidic something is; and the higher the pH, the more alkaline something is. The pH scale goes from 1 to 14, 1 being the most acidic, 14 being the most alkaline, and 7 being neutral (like most water) (See Figure 10). A pH of 5.5 is an important pH level for teeth as the teeth begin to dissolve or demineralize at a pH in the mouth below 5.5. At a pH above 5.5, the teeth begin to remineralize (See Figure 11).

Many oral microorganisms require a pH around neutrality for growth and are sensitive to extreme changes in acid or alkali. The pH of most surfaces in the mouth is regulated by saliva, which has a mean unstimulated pH of 6.75–7.25. Optimal pH values for healthy bacterial growth will be provided to the areas of the mouth bathed by saliva.[1] Shifts in the proportions of bacteria within the dental plaque from healthy to unhealthy occur following fluctuations in environmental pH.[1] When we eat, the pH in plaque can fall rapidly to below pH 5.0 through the production of acids (predominately lactic acid) as the bacteria metabolize (eat) the ingested nutrients.[1] Consuming acidic foods and drinks can likewise lower the pH within the mouth. Depending on the frequency (and the acidity) of food intake, the bacteria in plaque will be exposed to a variety of episodic challenges of low pH.[1] Many of the predominantly healthy bacteria within dental plaque (nonacid producers) can tolerate brief conditions of moderately low pH but are inhibited or killed by more frequent or prolonged exposures to acidic conditions.[1] If a patient’s mouth experiences dramatic or long-lasting periods of low pH, this can result in the enhanced growth of, or colonization by, aciduric and acidogenic (cavity causing) bacteria.[1]

Put simply, the equation looks like this:

Prolonged/intense low pH in the mouth = death of healthy bacteria/overgrowth of cavity-causing bacteria = caries infection = CAVITIES.

Dental plaque that is kept at a pH of 7.0 or greater does not experience this shift in the bacterial species to aciduric and acidogenic (cavity-causing) bacteria even during exposure to sugar. If the pH in the mouth can be maintained at a neutral or alkaline pH, regardless of sugar, food, or acidic drink consumption, the healthy bacteria within the dental plaque biofilm will not die and the shift to cavity-causing bacteria will not occur.[2]

A healthy pH balance in the mouth can explain why many people—family members, coworkers, friends, etc.—can consume lots of sugary food and drink, seemingly take little care of their mouth, and yet do not have cavities. At the same time, many people who are extremely diligent about their diet and home care continue to get cavities because the bacteria in their biofilm are primarily cavity causing bacteria. These people continue to be very susceptible to small changes in pH.

The good news is that this microbial shift from healthy bacteria to cavity causing bacteria can be reversed using alkaline pH dental therapies (such as CTx4 Treatment Rinse, CTx3 Rinse, and CTx4 Gel 1100). The pH neutralization (alkaline) therapy can be used in a few different ways.

For those patients that are experiencing dental decay, alkaline dental products with pH ranges from 8 to 11 can be used daily (such as CTx3 Rinse) to reverse the bacterial shift from cavity-causing bacteria to healthy bacteria. In addition, daily uses of a pH neutralizing oral spray, gel, or gum after meals, snacks, and drinks can quickly elevate acidic oral conditions caused by diet. This method of pH neutralization can shorten acid attacks caused by foods/sugars and keep the acid attack from dropping to intensely low pH levels.

Finally, for patients that have risk factors leading to a bacterial imbalance, targeted pH neutralization dental products used daily can greatly aid in preventing a bacterial shift in their oral biofilm. This is especially important for individuals with unmodifiable risk factors such as a restricted diet, saliva issues, prescription medications, and children at risk. It is preferable to prevent the bacterial shift from healthy to unhealthy (cavity-causing) than to reverse an acidic biofilm back to a healthy balance.

In a clinical trial, conducted by the authors, examining the potential of pH neutralization as a caries treatment strategy, ten high caries risk adults were instructed to wear oral trays containing a gel with a pH of 9.0 for 8 hours at night for a period of 30 days. Mixed samples of their plaque were taken prior and after the 30-day period. The plaque samples from each individual were then checker-boarded using PCR and 16S gene sequencing DNA identification to identify the individual bacteria and the changes the bacterial species and concentration based on the neutralizing strategy. The results demonstrated an elimination of caries-causing bacteria like Selenomonas, slight reduction of Streptococcus mutans/sobrinus, Lactobacillus species, and a concurrent growth of healthy bacteria including Prevotella, Campylobacter, and Veillonella (See Figure 13). These limited results demonstrate that it is possible to reduce/shift the cariogenic microbes from the oral biofilm while replacing them with healthy organisms by regular maintenance of a neutral pH with a tray/gel system.

The method of pH neutralization is a safe and effective way of reversing the bacterial shift or preventing the bacterial shift toward cavity-causing bacteria and can be used for all age groups, including infants. Patients are encouraged to identify the pH of dental products they use in order to identify if the products are pH neutralizing. The ideal pH range for prevention is 8–9, and the ideal pH range for treatment of an unhealthy biofilm is 9–11.

  1. Philip D. Marsh, Michael V. Martin, Oral Microbiology, 5th ed. (2009),15–16.
  2. P. D. Marsh, “Dental Plaque as a Biofilm and a Microbial Community—Implications for Health and Disease,” BMC Oral Health 6, Suppl. 1(2006): S14.