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J Dent Res 82(11) 2003 Fluoride and Tooth Crystal 911 Table 1. Descriptive Data from Montreal, Toronto, and Fortaleza and width of the dentin crystallites were 177 Å (+ 31 Å) and 70 Å (+ 18 Å), respectively. Sixtyone percent of the samples analyzed came from patients who had always lived in the city where the teeth were extracted. More than 90% of the analyzed teeth came from patients who had lived in the area of tooth collection for more than 5 yrs (covering the majority of the period in which the 3rd molars were being formed). Table 1 presents the data divided by location. Enamel F concentrations in teeth col- F Concentration (ppm) Crystallite Size (Å) Enamel Dentin Enamel Long Axis Enamel Short Axis Dentin Long Axis Dentin Short Axis Location N Mean (SD) N Mean (SD) N Mean (SD) N Mean (SD) N Mean (SD) N Mean (SD) N Montreal 24 132.5 (55.1) 24 197.8 ( 77.8) 24 236 (39) 24 163 (30) 24 176 (31) 24 71 (24) 24 Toronto 23 198.6 (77.5) 23 322.6 (159.1) 22 243 (44) 23 179 (42) 23 170 (32) 23 64 ( 7) 23 Fortaleza 53 149.4 (99.2) 51 398.7 (177.3) 53 284 (67) 37 208 (48) 37 183 (31) 52 73 (19) 52 Total 100 156.8 (88) 98 333.1 (174.3) 99 259 (58) 84 187 (46) 84 178 (31) 99 70 (19) 99 Table 2. Summary of One-way ANOVA ANOVA Post hoc Dependent Variable F Sig. (I) Location (J) Location Mean Difference (I-J) Sig. Enamel long axis 6.038 0.004 LSD Montreal Toronto - 6.61 0.676 Fortaleza -43.04 0.003 Toronto Montreal 6.61 0.676 Fortaleza -36.43 0.011 Fortaleza Montreal 43.04 0.003 Toronto 36.43 0.011 Enamel short axis 7.780 0.001 LSD Montreal Toronto -15.11 0.218 cross-section Fortaleza -40.81 0.000 Toronto Montreal 15.11 0.218 Fortaleza -25.69 0.020 Fortaleza Montreal 40.81 0.000 Toronto 25.69 0.020 Dentin long axis 1.147 0.322 Dentin short axis 1.441 0.242 cross-section lected in Toronto were significantly higher than those in teeth from Montreal (p = 0.009) and Fortaleza (p = 0.024). Dentin F concentrations were significantly lower in Montreal compared with Toronto (p = 0.008) and Fortaleza (p < 0.001). Enamel crystallite length was significantly greater in teeth from Fortaleza than in those from Toronto (p = 0.011) and Montreal (p = 0.003), while enamel crystallite width was significantly greater in teeth from Fortaleza when compared with that in teeth collected from Toronto (p = 0.020) and Montreal (p < 0.001). No difference in the dentin crystallite size was seen in the 3 different communities. A summary of the one-way ANOVA analysis is presented in Table 2. There was also positive correlation between dentin F concentration and enamel crystallite length (r s = 0.405; p < 0.001) and width (r s = 0.483; p < 0.001). DISCUSSION This is the first study to present data on hydroxyapatite crystallite size and on F concentration in dentin of unerupted third molars from areas with different drinking water F concentrations. Only teeth with completed or almost completed roots were utilized, because of the possible effect that tooth maturation might have on crystal size. Additionally, the use of a single type of tooth avoided problems that may be associated with the variation in F content between different tooth types (Aasenden et al., 1973). Unerupted third molars were chosen because they are more easily collected (commonly extracted) and have not been exposed to the oral environment (thus avoiding topical F exposure). Teeth from 3 different areas were collected. Optimal F levels in drinking water are usually adjusted for the annual average maximum daily air temperature (AAMDAT) and the relationship between average temperature and water intake (Galagan and Vermillion, 1957; PHS, 1962; National Research Council, 1993). Based on this, Toronto (AAMDAT between 14.7 and 17.7°C) and Fortaleza (AAMDAT between 26.3 and 32.5°C) are considered to have optimum F levels in their drinking water. This study showed that dentin F concentrations were significantly higher in teeth collected in Toronto and Fortaleza compared with those collected in Montreal, while enamel F concentrations were higher in teeth from Toronto when compared with teeth from Fortaleza and Montreal. These results were expected, since previous work has shown that the enamel of unerupted third molars has significantly less F concentration in areas where there are low levels of F in the drinking water (Mestriner et al., 1996). Analysis of the data presented also showed that enamel crystallite size was greater (length and width) in teeth coming Downloaded from jdr.sagepub.com by guest on April 8, 2011 For personal use only. No other uses without permission. International and American Associations for Dental Research
912 Vieira et al. J Dent Res 82(11) 2003 from Fortaleza, compared with teeth from Montreal and Toronto. However, no change was seen in the dentin crystallite size in the 3 groups. Dentin has an embryologic origin different from that of enamel and contains collagen and various non-collagenous proteins not found in enamel (Ten Cate, 1994). Some proteins— like phosphophoryn, sialoprotein, osteocalcin, and osteonectin, found in dentin and bone—are known to regulate crystallite growth in mineralized tissues (Bartold and Narayanan, 1998). This dentin crystallite growth regulation is reflected in the fact that dentin crystallites are smaller than enamel crystallites (Marshall, 1993), and may explain the apparent lack of effect of F concentration (or other factors) on dentin crystallite size. This stronger regulation may also explain the fact that dentin F concentration correlates with enamel crystallite size (length and width) and not with dentin crystallite size. Dentin may be the best marker for the estimation of chronic fluoride intake and the most suitable indicator of the body burden of F. This tissue does not normally undergo resorption, is more easily obtained than bone, seems to continue accumulating F slowly throughout life, and is permeated by extracellular fluid (WHO Expert Committee on Oral Health Status and Fluoride Use, 1994). Consequently, the F concentration found in dentin better represents the amount of F to which an individual has been exposed. We speculate that crystallite growth regulation in dentin is stronger than the direct effect of F on crystal growth. Therefore, overall F exposure is better reflected in the F concentration in dentin, but the effects of this exposure are more clearly seen in the enamel crystallite size, which is not as strongly regulated by matrix components. In bone, substantial increases in the width of apatite crystal size and/or lattice perfection have been shown to accompany F uptake (Baud et al., 1988). Our findings show an increase in enamel apatite crystal length and width with increasing dentin F concentration. The explanation for the differences in the influence of F on crystallite size in bone and enamel may once again be related to the influence of extracellular matrix present in bone, which may more strongly regulate the crystal growth in one direction than in the other. Teeth originating in Fortaleza had lower levels of F in their enamel, and their enamel crystallites were larger than those from Toronto. F uptake in bone has been shown to increase the width of apatite crystal (Posner and Tannenbaum, 1984; Grynpas, 1990; Eanes and Hailer, 1998). The explanation for the enamel crystallites in Fortaleza being larger than those in Montreal and Toronto is not obvious. This apparent contradictory finding may be explained by the different ethnicity of the population of the two countries, which can influence their susceptibility to the effects of F. Some data suggest (National Research Council, 1993) that DF is more prevalent among African-Americans than among other ethnic groups in the same community. Russell (1962), in the Grand Rapids fluoridation study, noted that fluorosis was twice as prevalent among African-American children than white children in regions with the same amount of F in the drinking water. In the Texas surveys in the 1980s, the odds ratio for African-American children with DF, compared with Hispanic and non-Hispanic white children, was 2.3 (Butler et al., 1985). Additionally, a study conducted in our laboratory has shown that individuals with different F levels in their tooth structure present similar levels of DF, while teeth with different DF levels have similar F concentrations (Vieira et al., 2003). DF is a tooth malformation believed to be caused by chronic ingestion of high levels of F (Murray et al., 1991; Den Besten, 1994). A hypothesis of genetic susceptibility to F has been shown in a recent study of different mouse strains (Everett et al., 2002). In that study, the investigators showed that different inbred strains of mice presented different susceptibilities to DF while having similar F concentrations in their teeth and bones. The ethnic, racial, and genetic make-up of the people living in the 3 areas on which our study has focused can be expected to be quite different, since stronger influences from France, England, and Portugal can be found in Montreal, Toronto, and Fortaleza, respectively. Additionally, due to a stronger recent immigration influence in Toronto and Montreal, compared with Fortaleza, the genetic diversity of the Canadian cities can be expected to be much higher than that in the Brazilian city. It can also be argued that different dietary habits of the two populations (Brazil and Canada), nutritional status of the individuals from the two countries, sun exposure (vitamin D), and any other unknown factors could interfere with the effect of F levels on tooth crystal size. Height and weight of all patients were taken, and body mass index (BMI) was calculated. No subject was found to have a BMI under the cutoff point established by the World Health Organization (WHO, 1995). However, nutritional habits, based on cultural differences and natural resources, can be expected to be quite different in the 3 cities. Fortaleza, which is located 3 degrees from the equator, has an equatorial climate, while Toronto and Montreal, located between the Tropic of Cancer and the Arctic Circle, are located in temperate climates. A lowering of adequate uptake of Vitamin D, which is required for proper mineralization of dental tissues (Limeback et al., 1992), can occur in temperate regions. Therefore, we can hypothesize that the different climates between the two countries might have had an influence on the quality of the mineralized tissues, including teeth, reflected in the size of the apatite crystallites. ACKNOWLEDGMENTS We would like to thank those who helped in tooth collection: Dr. Maia and Mrs. Silva in Fortaleza; Dr. Clokie, Dr. Caminitti, Dr. Baker, and oral and maxillofacial surgery residents in Toronto; and Dr. Gornitsky, Dr. Saleh, Dr. Robin, and Dr. Beaudet-Roy in Montreal. We also thank Drs. Bull and Kopciuk for their help in the statistical analysis. This study was supported by a grant from the Canadian Institute of Health Research (CIHR) and by Harron and Connaught scholarships (AV). REFERENCES Aasenden R, Moreno EC, Brudevold F (1973). Fluoride levels in the surface enamel of different types of human teeth. Arch Oral Biol 18:1403-1410. Bartold PM, Narayanan AS (1998). Biology of the periodontal connective tissues. Carol Stream, IL: Quintessence Books. Baud CA, Very JM, Courvoisier B (1988). Biophysical study of bone mineral in biopsies of osteoporotic patients before and after longterm treatment with fluoride. Bone 9:361-365. Butler WJ, Segreto V, Collins E (1985). Prevalence of dental mottling in school-aged lifetime residents of 16 Texas communities. Am J Public Health 75:1408-1412. Den Besten PK (1994). Dental fluorosis: its use as a biomarker. Adv Dent Res 8:105-110. Downloaded from jdr.sagepub.com by guest on April 8, 2011 For personal use only. No other uses without permission. International and American Associations for Dental Research
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