What’s the Risk? Bacterial Biofilm Imbalance

The bacterial biofilm on teeth is commonly referred to as dental plaque. Dental plaque consists of a community of diverse bacteria from more than 700–800 different species of bacteria.1 While there is great diversity in the potential bacterial makeup of everyone’s dental plaque, typically, a healthy person has only about 120 different species in their plaque. Interestingly, patients with high risk for dental caries (cavities) may have more gross plaque but usually have fewer total species.2 Not as many bacteria are adapted to survive in the low pH conditions of the dental-caries-producing plaque or biofilm. Dental plaque is a risk factor for cavities primarily in two different ways. First, if the plaque biofilm on your teeth has a high concentration of the cavity-causing, acidic bacteria, there is an increased risk of tooth mineral loss. Second, if there is too much total bacterial plaque on your teeth, there is an increased risk of tooth mineral loss.

The growth and type of your dental plaque biofilm can be influenced by several factors, including the availability of nutrients, the pH of the oral environment, and the roughness of the tooth surface (rougher surfaces are an ideal setting for microbial adhesion).

There are many ways to identify if too much plaque is a risk factor. First, if a patient or dental professional notices any visible plaque buildup between brushings. Plaque buildup between brushings is a sign of a highly active biofilm, and the bacteria within the biofilm are reproducing quickly. Additionally, a dental professional can perform a plaque index check which can gauge the degree of dental plaque accumulation. This is done by providing the patient with a plaque-disclosing dye solution that will color all of the tooth surfaces containing plaque. The practitioner will then count the number of plaque-containing tooth surfaces and divide it by the number of available tooth surfaces. For example, if a patient has a total of 100 tooth surfaces and 70 are identified as containing plaque, the patient’s plaque index is 70%. There are numerous plaque indices that have been used over the years in dentistry.3 However, they are time-consuming and not many dental practices perform a routine plaque index check.

A dental professional can also perform a bacterial ATP swab test, like the CariScreen, to identify patients who have a prevalence of the cavity-causing bacteria in their dental plaque as well as a high bacterial load.This swab test is a quick, painless procedure, and results can be identified in less than one minute. ATP is often used for caries risk screening as high numbers of ATP correlate to high quantities of cavity-causing bacteria in the dental plaque. While it can’t be used to diagnose current decay, bacterial ATP screening is a good indicator of future decay; you can find a CariFree dentist in your area if you’re interested in having a CariScreen test done.

A patient is at risk if they have too much plaque buildup/accumulation, or a high quantity of cavity-causing bacteria within their dental biofilm. This risk factor is commonly referred to as biofilm challenge and/or plaque buildup. Patients that are found to have high volumes of bacterial plaque or high numbers of cavity-causing bacteria in their plaque may be recommended a professional broad-spectrum antibacterial therapy, pH neutralization products, xylitol-containing products, and increased fluoride exposure to reduce the biofilm challenge.


  1. B. Rosan, R. J. Lamont, “Dental Plaque Formation,” Microbes Infect 2(2000): 1599–607.
  2. Y. Li, Y. Ge, D. Saxena, and P. W Caufield, “Genetic Profiling of the Oral Microbia Associated with Severe Early-Childhood Caries,” J Clinical Microbiology 45, no. 1 (January 2007): 81–87.
  3. S. Matthijs, M. M. Sabzevar, and P.A. Adriaens, “Intra-Examiner Reproducibility of 4 Dental Plaque Indices,” J ClinPeriodontol 28, no.3 (Mrach 2001): 250–4.

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