Prevalence of caries-associated microflora after radiotherapy in patients with cancer of the head and neck.

In this clinical study of irradiated head and neck cancer patients at M. D. Anderson Hospital, 68 adult xerostomic patients using different fluoride gels were evaluated for oral levels of Lactobacillus and Streptococcus mutans during the postradiotherapy period, which ranged from 2 months to 20 years. The fluoride groups were compared with a control group consisting of 21 cancer patients who were scheduled to undergo radiotherapy. Lactobacillus levels were significantly elevated in all postradiotherapy groups, irrespective of the type of fluoride gel used. S. mutans levels in the 0.4% SnF2 group were significantly lower than in the 1.0% NaF gel group. The low levels of S. mutans observed in the SnF2 group suggest that this agent may be exerting a downward selective pressure on the microorganism during the postradiotherapy period.