Caries incidence, salivary flow rate and efficacy of fluoride gel treatment in irradiated patients.

The caries-preventive effect of daily applications of a fluoride gel was studied in 55 patients receiving radiotherapy for tumors of the head and neck. The study was designed as a randomized, double-blind study with two parallel groups. From the start of radiotherapy one group received a 0.42% F gel once a day for 1 year. The other group received a daily application of a 1.23% F gel for 4 weeks followed by the use of the 0.42% F gel daily for 1 year. The results showed that in patients with an unstimulated saliva flow of > 0.1 ml/min daily fluoride gel treatment with a fluoride concentration of 0.42% F was sufficient to inhibit caries almost completely. The use of the 1.23% F gel was not superior to the 0.42% gel treatment program alone. In an attempt to evaluate the salivary flow rate as a diagnostic criterion for increased caries risk, sensitivity and specificity were evaluated. It was found that with an unstimulated saliva flow rate of < 0.1 ml/min the positive predictive value was 80%. The corresponding value for stimulated salivary flow rate of < 0.5 ml/min was 85%. One can therefore predict that 80% of patients with flow rates < 0.1 ml/min will develop at least one carious lesion per year. The corresponding negative predictive value for unstimulated saliva flow > 0.1 ml/min was 75%. That means that 75% of patients using the 0.42% F gel daily and with at least some saliva secretion will not develop any new carious lesions.