Factors associated with the occurrence of developmental defects of enamel and dental fluorosis among 4 and 8 year olds in Nigeria

Abstract

Enamel formation may be affected by genetic and environmental factors resulting in enamel defects such as developmental defects of enamel (DDE) and dental fluorosis. This 3 phase project investigated the influence of fluoride (F) exposure (intake and excretion), nutritional deficiencies, dental factors as well as other environmental factors and genetics on DDE and dental fluorosis among 4 and 8 year old Nigerian children. In Phase 1, dental examination for the presence of DDE, dental fluorosis and caries experience using the modified DDE index, Thylstrup and Fejerskov (TFI) and Dean’s indices and dmft/DMFT indices respectively was undertaken for 302 four-year-olds and 322 eight-year-olds and a parent/guardian questionnaire collected data on dental health and nutrition. In Phase 2, information and samples to estimate F intake and urinary F excretion of a sub-sample of 61-four- and 64 eight-year-olds was obtained. In Phase 3, a buccal mucosa swab was collected from the subsample for gene sequencing to determine the presence of Single Nucleotide Polymorphisms (SNP) in the COL1A2 gene. The prevalence of dental fluorosis, dental caries and DDE was 5.6%, 10.6% and 78.5% and 9.3%, 16.8% and 64.7% in the primary dentition of 4 and 8 year olds respectively while it was 29.8%, 7.5% and 67.1% respectively in the permanent dentition of 8 year olds. The Spearman correlation coefficient for severity of primary dentition dental fluorosis and drinking water F in 4 and 8 year olds was 0.12 and 0.15 respectively (p<0.05); in the permanent dentition of 8 year olds it was 0.17 (p=0.002) for cooking water F and 0.28 (p=0.001) for drinking water F. The Pearson correlation coefficient for Total Daily F Intake (TDFI) and urinary F excretion was 0.41 (p=0.001) and 0.57 (p<0.001) in 4 and 8 year olds respectively. Drinks, foods and toothpaste contributed 17%, 54% and 29% and 21%, 54% and 25% to TDFI among 4 and 8 year olds respectively. Fluoride toothpaste use, gender, drinking water F, cooking water F, exclusive breastfeeding, infant/childhood diseases, TDFI and Total Daily Fluoride Retention (TDFR) were statistically significant predictors of DDE and dental fluorosis (p<0.05). The presence of SNPs CC and AC in the COL1A2 gene approached statistical significance as predictors for dental fluorosis (p=0.08). Enamel formation is vulnerable process, prone to many influences. The DDE and TFI indices provided a sensitive record to explore predictors for the presence of enamel defects and dental fluorosis in this young Nigerian population. Adoption of oral health and feeding habits which prevent excessive F exposure remain key principles to mitigate against these conditions.