Some dentists determine a patient's susceptibility to dental caries by measuring

This should offer some insight!

Two major problems dominate today's clinical cariology: although it has been known for centuries that sugar harms teeth this still does not often impinge on personal behaviour; the development of clinical caries is so slow that any snapshot of the present situation does not necessarily predict future caries incidence. Some simple tests have been developed for overcoming these problems in a causally directed diagnostic and therapeutic system of providing dental care. Routine measurement of stimulated salivary flow collected over 5 min objectively reveals the hyposalivation or xerostomic patients and directs them toward careful dental and medical examinations as well as to intensified preventive measures. Measurement of the pH and buffering capacity of the saliva related to a knowledge of the present caries prevalence gives an indication of the caries susceptibility of the patient. A high salivary lactobacillus count reveals in most cases a high frequency of sugar intake (or removable dentures and/or open carious lesions), and a salivary yeast infection is an indicator of reduced salivary flow and removable dentures. Both these microbiological shifts are shown by caries active patients. Using modern dip-slide techniques salivary aciduric lactobacilli and yeasts are easily cultured, and thus the development of new caries lesions may be predicted. Such cultures can also be used in the motivation phases of patient management. These simple tests help the modern dentist to evaluate the risk of future caries development, and to strengthen the motivation in patients to adopt healthy dietary habits.