Caries Risk Assessment

More than 90% of adults have experienced dental caries before 30 years old. Dental caries is defined as a transmissible localized infection caused by a multifactorial etiology linking complex risk factors and protective factors. In order for dental caries to develop, four interrelated factors must occur:

  1. the patient’s (host) diet must consist of repeated digestion of refined carbohydrates,
  2. the host’s resistance to disease is decreased,
  3. the factor of time, and
  4. there must be a specific bacteria (Streptococci or S. mutans) present in the dental plaque.

The S. mutans bacteria play an active role in the early stages of the caries process, whereas the bacteria lactobacilli contribute to the progression of carious lesions. Carious lesions must be diagnosed in conjunction with a current clinical examination and imaging to verify suspicious lesions – especially interproximal lesions. Laser caries detectors can also be used as an adjunct in caries diagnosis.

Enamel is the most highly mineralized hard tissue in the body. The enamel matrix is made up of a protein network consisting of microscopic mineralized hydroxyapatite crystals arranged in rods or prisms. The protein network facilitates the diffusion of fluids, such as calcium and phosphate ions distributing these ions throughout the enamel. As carbohydrates are consumed by the host, the carbohydrates are broken down in the oral cavity by the protein enzyme amylase. This reaction causes lactic acid to be produced, thereby demineralizing the enamel matrix. If the demineralization of enamel is not reversed by the action of fluoride or calcium and phosphate ions, then the demineralization process continues further into the tooth structure, affecting the dentinoenamel junction (DEJ) and eventually the dentinal layer. The term “overt or frank” caries is used when it reaches the DEJ.

A carious lesion develops in three stages of demineralization. The first stage in demineralization of enamel is called the incipient lesion or “white spot” (Figure 1). This beginning carious lesion can be reversed with the daily use of the fluoride, calcium, and phosphate ions, persistent oral hygiene care to reduce plaque that harbors cariogenic bacteria, and a reduction of refined carbohydrates. The second stage of caries development involves the progression of demineralization of hard tooth tissue leading to the DEJ and into the dentinal layer. The third stage is the actual cavitation in the dentinal layer. Neither of the last two stages can be reversed and require mechanical removal of dental caries.

Figure 1. Incipient Interproximal Caries.
Incipient Interproximal Caries
Image source: The Ohio State University College of Dentistry

There are three levels of preventive dentistry that the dental professional should understand when educating patients in the dental caries process. The first step is primary prevention. This initial phase includes the transmission of S. mutans bacteria via saliva. Primary prevention seeks to reduce the number of bacteria that cause dental caries, as well as using assessment tools to prevent future caries. The second step is secondary prevention, which prevents, arrests, or reverses the microbial shift before any clinical signs of the disease occur. The third step focuses on limiting or stopping the progression of the caries process by initiating remineralization therapy of existing lesions.