A comparison of the anticaries effectiveness of daily and weekly rinsing with sodium fluoride solutions : final results after three years

Children in a fluoride-deh’cient area rinsed their mouths either weekly with a 0.2% NaF solution, weekly with a 0.1% NaC1 ,,;olution (placebo) or daily with 0.05% NaF solution. Rinses were conducted in school under the teacher’,,; supervision. Examinations for dental caries were made by two PHS examiners. After three years, incremental caries scores for Examiner 1 showed that subjects in the weekly and daily F rinse groups developed . 3Z 7% and 4Z4% Fewer DMFS than controls. Corresponding Findings for Examiner 2 were 23.5% and 33.6%. For both examiners combined, each regimen of F rinsing was effective in controlling decay, but the observed difference between the two F rinses was not statistically significant. The weekly regimen takes less school time and requires less effort than daily rinses, and costs an average of only 75~ per child per year, whereas costs of the daily procedure are Four times higher. Because of these practical considerations and the lack of clear-cut difference in effectiveness between the two F rinse procedures, the weekly method is preferable as a cost-effective way to reduce children’s tooth decay in a public health program. This report contains final results of a three-year clinical trial which compared the anticaries effectiveness of daily and weekly mouthrinsing with sodium fluoride solutions. Details of the study design appeared in a previous report of interim findings. 1 Methods and Materials The study was conducted in Biddeford, ME, a nonfluoridated community. Only negligible levels of natural fluoride (0.3 ppm or less) are present in the community’s drinking water. At the start of the study in October, 1976, 824 participants in grades 5, 6, and 7 (ages 10 to 12) attending public and parochial schools were examined. Two Public Health Service examiners, hereinafter identified as Examiners I and 2, made the baseline dental examinations. Children were arbitrarily assigned in about equal numbers to each examiner as each classroom reported for examinations. Both examiners used the criteria for diagnosing dental caries (DMFS) that were resented at the ADA’s Conference on the Clinical Testing of Cariostatic Agents in 1968. ~ Examiner 1 had limited field experience with the classification system. Examinations were conducted with plane dental mirrors, No. 23 explorers, fiberoptic illumination, and compressed air; radiographs were not taken. Each child was re-examined annually by the same investigator who made the baseline examination. The examiners were unaware of any child’s group assignment and did not have access to records from previous examinations. Within each school, participants randomly were assigned to one of the three following groups: Group C (controls) rinsed once a week with a placebo solution (0.1% NaC1); Group W rinsed once a week with a 0.2% NaF solution; and Group D rinsed daily with a 0.05% NaF solution. Subjects rinsed with 10 ml of solution for 60 seconds. Participating children in elementary and junior high school, i.e., through 8th grade, rinsed in their classrooms under the direct supervision of their teacher. However, during the last year, 9th graders in high school rinsed in the cafeteria under the supervision of lay personnel. These children reported to the cafeteria for rinsing in the brief interval between their arrival at school by bus and the start of homeroom period due to scheduling problems. Teachers kept a record of each child’s participation throughout the study. Firstand second-year tallies showed that only a small proportion of the participants, 1.6% and 3.1%, respectively, missed more than 20% of their assigned maximum number of treatments. During the third year, records showed that a problem of poor compliance was occurring in the high school third of the study population. Monetary incentives, convenient times for make-up sessions, and liberal use of late passes were offered to improve participation in the high school, but they had little impact. During the third year, 21.6% of all participants were absent for more than 20% of their