The Effects Of Fluorosis On The Distribution Of Fluorine And Related Elements In Human Dentin

Objective: 1) Investigate the effects of fluorosis on the distribution of fluoride and other related elements in human dentin. 2) Compare the differences in the morphology structure and inorganic component distribution of normal teeth and dental fluorosis from non-endemic fluorosis areas to normal teeth and dental fluorosis from fluorosis areas. 3) Explore the binding and symbiotic relationship between fluoride and its related elements. Methods: The first experimental group was consisted of normal third molars from fluorosis areas. The second experimental group contained third molars of moderate dental fluorosis from endemic fluorosis areas(according to the classification criteria of Dean on dental fluorosis), while the control group was consisted of normal third molars from non-endemic fluorosis areas. Every-group had 30 teeth. The teeth in vitro were collected and processed by blank treatment, demineralization and deproteination. The morphology characteristics of the three groups were observed by SEM. The content distribution of fluorine and its related elements in dentine was observed and measured by TOF-SIMS and EPMA. Data analysis was based on the SPSS 17.0 statistics software. Results: 1. The Fluoride content in the first experimental group, the second experimental group and the control group showed significant differences at all levels. In addition, the Fluoride content gradually increased from the enamel-dentinal junction to the pulp cavity. The content of Calcium, Magnesium, Sodium and Phosphorus in the same level of dentin in the first experimental group and the control group showed no significant differences. However, between the first and the second experimental group, as well as, between the second experimental group and the control group, the differences were statistically significant. The Potassium content showed no statistical significance in the pulp cavity between the three groups. The Calcium and Phosphorus content was highest in the middle layer and lowest in the proximal pulp cavity, with the under-enamel-dentinal junction in between. The Magnesium content gradually increased from the enamel-dentinal junction to the pulp cavity. However, these differences between the experimental group and the control groups were not statistically significant at different depths. The Sodium content was not statistically significant between the middle and the side of the proximal pulp cavity in the three groups.2. On the distribution of different elements in dentin, TOF-SIMS results demonstrated that the distribution images of Fluorine was similar to that of the Calcium, Sodium and Hydroxyl. Meanwhile, the distribution of Phosphate in the peritubular dentin was opposite to that of the above elements.3. The morphology characteristics observed by SEM shows normal teeth from non-endemic fluorosis area had regularly arranged, uniformly shaped, and consistently sized dentin tubules. It was also observed that the structural integrity of the peritubular dentin was maintained. On the other hand, in normal teeth from fluorosis areas, the dentin tubules were arranged slightly irregular and shaped unevenly. In addition, some tubules were atresia and with peritubular dentin collapse-deformation and defects. The dentine tubules of moderate dental fluorosis showed different open sizes and shapes, disordered and irregular arrangement, and even part of dentinal tubules loss and deformation. Most of peritubular dentin could not be observed. Conclusion: 1. The Fluorine, Sodium and Magnesium content gradually increased from the enamel-dentinal junction to the pulp cavity. The Calcium, Phosphorus and Sodium content in different depth of fluorotic dentine were higher than that of normal teeth. However, the Calcium, Phosphorus and Sodium content in different depth of the normal teeth from fluorosis area was lower than that of normal teeth.2. On the microstructure change of dentine by fluorosis, under the experimental conditions: the destruction of dentin tubules increased with the degree of fluorosis, which caused the irregular arrangement of tubes. Fluorosis also led to change in the shape of the tubular opening from circular to deformation, sometimes even resulting in dentin tubule missing or fusion and peritubular dentin transitioning from defect to disappear.