MUTANS STREPTOCOCCI IN A THAI POPULATION - RELATION TO CARIES AND CHANGES IN PREVALENCE AFTER APPLICATION OF FISSURE SEALANTS

The aims of this study were to evaluate the level of mutans streptococci in two groups of Thai (Bangkok) children; to relate the findings to caries prevalence and to the caries increment over 2 years, and to study whether different sealant and fluoride programmes affected levels of mutans streptococci over a 2-year period. The baseline survey comprised 1,114 children aged 12 years. For the sealant project, a minimum of three caries-free permanent molars was required; 752 children aged 12-13 and 512 children aged 7-8 years were distributed into five groups: control group, Delton fissure sealant group, glass ionomer fissure sealant applied by dentist (GIC-dentist group) or by school teachers given a 3-day course (GIC-teacher group), and an HF group (0.5% HF solution applied 3 times). The WHO standard criteria were used to record caries. Prevalence of mutans streptococci was estimated using the Strip mutans(R) test. Mean DMFT (n = 1,114) of 12-years-olds was 2.96; 17% had Strip mutans class 0 (low level), 32% class 1, 33% class 2 and 18% class 3 (the corresponding mean DFT +/- SD for each mutans streptococci class was 1.84+/-2.33, 2.23+/-2.14, 3.18+/-2.75, and 3.59+/-3.01 respectively). For the 7- to 8-year-olds (n = 512), mean df teeth at baseline was 5.36 (d = 5.19; f = 0.17); 5% had Strip mutans class 0, 17% class 1, 33% class 2 and 45% class 3 (the corresponding mean df teeth was 3.19+/-2.5, 4.13+/-2.84, 4.89+/-2.94 and 6.39+/-3.16 respectively). Mean DFS occlusal caries increments for age group 12-13 years were: control 0.70 surfaces, Delton 0.05, GIC-dentist 0.48, GIC-teacher 0.56, and HF 0.76 DFS. For age group 7-8 years, mean DFS occlusal caries increment was: control 0.66 surfaces, GIC-dentist 0.32, GIC-teacher 0.17 and HF 0.44. In conclusion, levels of mutans streptococci were significantly related to caries prevalence and increment. The study also showed that the outcome of various treatments was associated with the levels of mutans streptococci at baseline.