Variation in fluorosis and caries experience among Lithuanian 12 year olds exposed to more than 1 ppm F in tap water

Aim: The aim of the present study was to analyze caries experience in relation to the occurrence of fluorosis in 12 year olds in a natural fluoride area. Methods: This cross-sectional study was conducted among 12-year-old lifetime residents (n = 301) of Klaipeda, Lithuania, where the natural fluoride content is 1.7-2.2 ppm F. Data collection included a clinical dental examination and an inquiry about toothbrushing habits. Dental caries was diagnosed according to the World Health Organization criteria and described in terms of decayed, missing, and filled teeth (DMFT)/decayed, missing and filled surfaces (DMFS) indices and decayed, filled surfaces (DFS) on selected proximal surfaces. Dental fluorosis was diagnosed according to the Thylstrup-Fejerskov (TF) index and categorized as none (TF = 0), mild (TF = 1-2), moderate (TF = 3-7), or severe (TF = 8-9). The chi(2)-, Kruskal-Wallis, and Mann-Whitney tests, Pearson's correlation, and linear regression served for statistical analyses. Results: A total of 34% of the 12 year olds studied had no signs of fluorosis, while the rest had mild (42%) or moderate (24%) fluorosis. Caries experience was negatively related to the presence of fluorosis. When present (TF > 0), the mean DMFT was 1.8 (standard deviation [SD]: 1.7) versus 2.6 (SD: 2.3) in the absence of fluorosis (TF = 0, P = 0.008). The corresponding mean DMFS values were 2.6 (SD: 3.1) versus 3.8 (SD: 4.3, P = 0.014). Conclusion: The presence of fluorosis associates with lesser caries experience in 12-year-old lifetime residents of an area with moderately-elevated natural fluoride.