Dental variables associated with differences in severity of fluorosis within the permanent dentition

The aim of this study was to assess the influence of age at start, duration, and completion of enamel formation, as well as of tooth-eruption age and enamel thickness on the severity of dental fluorosis within the permanent dentition. The material comprised Ugandan children (n = 219), aged 10-14 years, with 28 teeth and at least 1 tooth with fluorosis. The children were permanent residents in districts with either 0.5 mg or 2.5 mg fluoride/l in the drinking water. Fluorosis was assessed on the vestibular surfaces of all teeth using the modified Thylstrup and Fejerskov (TF) index. In order to relate fluorosis to the dental variables, the material was divided into a test group (n = 103), with fluorosis on all teeth, and a reference group (n = 116), with fluorosis on up to 27 teeth. The reference group was used to confirm or refute the findings in the test group. Paired comparisons showed significantly higher median TF scores for the late than for the early mineralizing and erupting teeth. In multiple regression analyses, the age at start, duration, and completion of enamel formation as well as tooth eruption was significantly related to the severity of fluorosis after controlling for enamel thickness (P < 0.05, n = 14). The effect (R2change) of the dental variables on the variation in severity of fluorosis within the dentition was in decreasing order: the duration of enamel formation, age at completion of enamel formation, tooth-eruption age, and the start of enamel formation.