Microbial Composition, pH-Depressing Capacity and Acidogenicity of 3-Week Smooth Surface Plaque Developed on Sucrose-Regulated Diets in Man

The effect of 3 weeks dietary supplementation, respectively restriction, of sucrose on gingival smooth surface plaque was assessed in 4 caries-inactive adults. Plaque samples collected from discrete tooth sites were monitored for the prevalence of streptococci, actinomycetes, and veillonellae, with special emphasis placed on Streptococcus mutans. At the end of each dietary period, the acidogenicity of plaques on 5 smooth tooth surfaces in each subject was assessed by in situ pH measurements subsequent to sucrose application. Reversible white spot lesions appeared in 2 of the 4 subjects on the sucrose-rich diet. In 3 of the 4 subjects, the pH-depressing capacity of their plaques was greater on the sucrose-rich than on the sucrose-poor diet. In the 4th subject, the acidogenicity of the plaques was similar on the two diets; this subject moreover appeared not to harbor S. mutans in these plaques. In the other 3 subjects, S. mutans occurred with greater frequency in their plaques on the sucrose-rich diet; however, the prevalence of S. mutans did not appear to be affected by diet. Other bacterial changes in plaques on the two diets seemed to be mainly subject-dependent with no consistent pattern from one individual to another.