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J Dent Res 82(11): 909-913, 2003
© 2003 International and American Associations for Dental Research

RESEARCH REPORT
Biomaterials & Bioengineering

How Does Fluoride Concentration in the Tooth Affect Apatite Crystal Size?

A. Vieira1,2, R. Hancock3, H. Limeback1, M. Schwartz4,5, and M. Grynpas1,2,*

1 Faculty of Dentistry, University of Toronto;
2 Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Room 840, Toronto, ON M5G 1X5, Canada;
3 Department of Chemical Engineering and Applied Chemistry, University of Toronto;
4 Department of Dentistry, Sir Mortimer B. Davis-Jewish General Hospital; and
5 Faculty of Dentistry, McGill University;

* corresponding author, grynpas{at}mshri.on.ca


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS & METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Despite fluoride’s (F) well-documented ability to prevent caries, the effects of F concentrations on enamel and dentin apatite crystals are unknown. The present study examined the hypothesis that tooth F concentration and tooth crystallite size correlate. One hundred human unerupted third molars were studied—53 from Fortaleza-Brazil (F water 0.7 ppm), 23 from Toronto (1.0 ppm), and 24 from Montreal (0.2 ppm). F concentration was analyzed by Neutron Activation Analysis and apatite crystal size by powder x-ray diffraction. A positive correlation between dentin F concentration and enamel crystallite length and width was found. Enamel crystallite length was significantly greater in teeth from Fortaleza than in teeth from Toronto (p = 0.011) and Montreal (p = 0.003). Enamel crystallite widths were significantly greater in Fortaleza teeth compared with those from Toronto (p = 0.020) and Montreal (p < 0.001). No difference in the dentin crystallite size was seen in the 3 regions. Thus, tooth F concentration and crystallite size correlate.

KEY WORDS: fluoride • crystallite size • dentin • enamel • human


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS & METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Over the last few decades, fluoride (F), despite its link with dental fluorosis (DF) (Den Besten, 1994), has been used all over the world to prevent caries. Fluoridation of community drinking water is considered to be one of the ten most important public health achievements of the 20th century (Everett et al., 2002), and the most cost-effective of all community-based caries-preventive methods (Garcia, 1989). However, despite its documented effectiveness in preventing caries (Murray et al., 1991), the effects of fluoride’s continuous systemic use are not completely understood. Specifically, the effects of different F concentrations on enamel and dentin mineral are unknown.

F has a high affinity for calcified tissues and is found to be concentrated in dental and bone structures (National Research Council, 1993). Approximately 99% of the body burden of F is associated with calcified tissues, where it mainly substitutes for the hydroxyl group (OH-) of the hydroxyapatite (HA) crystals (Ca10[PO4]6[OH]2). The substitution of F for OH in non-biological apatites results in crystal width contraction and no change in crystal length (LeGeros, 1991).

Apatite crystal size, shape, and arrangement in bone are said to be major determinants in establishing its biomechanical properties. Alterations in the dimensional properties of bone apatite crystals have been speculated to contribute to deleterious skeletal disorders such as osteogenesis imperfecta (Vetter et al., 1991; Eanes and Hailer, 1998). It can be hypothesized that alterations seen in fluorotic teeth may be due to alterations in tooth apatite. DF is a tooth malformation related to F ingestion (Den Besten, 1994). Electron micrographs have confirmed areas of enamel hypomineralization, gaps between enamel rods, and a decrease in the numbers of apatite crystals in the enamel rods of patients with DF (Fejerskov et al., 1974). High F ingestion has resulted in a smaller proportion of amelogenins being secreted and removed during enamel maturation (Eastoe and Fejerskov, 1984). Amelogenin is an important protein in tooth mineralization (Ten Cate, 1994). Additionally, F changes the amino acid composition of developing enamel proteins (Patterson et al., 1976). Since F influences bone crystal structure (Grynpas, 1990), it is feasible to postulate that F may also influence tooth apatite crystals. However, no information relating tooth F concentration and tooth (dentin and enamel) crystallite size is currently available.

The main purpose of this study was to determine the correlation between tooth F concentration and tooth crystallite size. Additionally, the difference between F concentration and crystallite size in tooth structure (dentin and enamel) of unerupted third molars from individuals residing in regions with different levels of fluoridated water was analyzed.


   MATERIALS & METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Patients from Toronto, Canada (drinking water artificially fluoridated at 1 ppm F), Montreal, Canada (drinking water not artificially fluoridated—natural levels of 0.2 ppm F), and Fortaleza, Brazil (water artificially fluoridated at 0.7 ppm F), who were scheduled for surgical removal of their unerupted third molars, were asked to participate in this study. Patients were asked to donate their extracted teeth and to answer a questionnaire about their place of residence. Prior to tooth collection, all patients signed consent forms. Ethical approval for this research was granted by the University of Toronto, Sir Mortimer B. Davis-Jewish General Hospital, and Universidade Federal da Paraiba ethical committees.

From all the teeth collected, only the teeth with completed or almost-completed roots were used. Teeth collected in Canada were kept frozen between collection and analysis. However, teeth originating from Brazil were sent to Canada (where analysis was performed) wrapped in gauze (embedded in thymol) and were subsequently frozen.

Teeth were defrosted, embedded in epoxy resin (Epoxycure resin, Buehler , Markham, Canada), and sectioned by means of a low-speed saw (Isomet, Buehler Ltd., Lake Bluff, IL, USA) and scalpel (Fig. 1Go). Dentin samples from the buccal and lingual sides of each tooth were pooled and collectively analyzed for F concentration by neutron activation analysis (INAA). The same procedure was used for enamel samples. [In INAA, each sample is bombarded with thermal neutrons that produce short-lived radioisotopes from the elements in the sample. These radioisotopes decay with specific half-lives, emitting gamma rays of discrete and characteristic energies. The relative amounts of gamma rays detected are proportional to the concentrations of the elements in the sample (Mernagh et al., 1977).]



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  		Figure 1. Schematic of sample preparation. First, we prepared two sections (2 mm apart) in the central part of the teeth (in the buccal-lingual direction following the coronal-apical axis), dividing each tooth into 3 sections (mesial, central, and distal). The coronal-central part was then further sectioned to provide buccal and lingual samples. We used a scalpel under a microscope to separate the enamel and dentin tissues.

 
After INAA, the samples were ground to a fine powder in a freezer mill (6750 Freezer/Mill, Spex Certiprep Inc., Metuchen, NJ, USA). We performed powder x-ray diffraction on the ground samples to calculate crystallite size using a powder x-ray diffractometer (Rigaku MultiFlex, Rigaku/MSC, Woodland, TX, USA). In powder x-ray diffraction, a thin layer of the sample is exposed to x-rays of fixed wavelength at different angles of incidence. We used the broadening of the peaks at 26- and 40-degree two-theta (2{theta}) to calculate the hydroxyapatite crystallite length and width, respectively (Klug and Alexander, 1954). An example of x-ray diffraction pattern and an apatite crystal schematic description are presented in Fig. 2Go.



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  		Figure 2. Schematic of a hydroxyapatite crystallite.

 
The diffraction pattern of the samples was determined with the use of Cu x-rays (1.54 Å wavelength). The values of B1/2 (002 and 130), the width at 50% maximum height of the hydroxyapatite reflections, were measured by a step-scanning procedure. Two scans were performed. The first scan was from 22 to 44 degrees 2{theta} with a step size of 0.5 degrees and a collection time of 0.1 sec per step. A second scan from 37.5 to 42.5 degrees 2{theta} was performed with a step size of 0.1 and a collection time of 1 sec per step. D values, which are related to crystal size/strain length (002) and width (130) of the apatite crystals, were calculated according to the Sherrer equation (below). The "crystal width" term is used to designate the cross-section length of the crystal ab plane (Fig. 2Go).


where K = "shape factor" constant (0.9), {lambda} = wavelength of the x-ray, Radian = constant 57.3°, Cos{theta} = cosine of half the 2{theta} angle, and ß = line broadening.

Statistical analysis was done with the SPSS software (SPSS Inc., Chicago, IL, USA). We performed a one-way analysis of variance (ANOVA) test to compare crystallite size as well as F concentration (enamel and dentin) in the 3 different locations (Fisher’s LSD post hoc test). We used the Spearman Correlation test to analyze the correlation between F concentration in tooth structure (dentin and enamel) and tooth crystallite size (dentin and enamel). The means as well as the standard deviations (SD) were determined. P values less than 0.05 were considered statistically significant.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
From 85 subjects, only teeth with mostly complete roots were used (42 subjects). One hundred teeth from Toronto (n = 23), Montreal (n = 24), and Fortaleza (n = 53) were selected. Only teeth with completely (n = 57) or almost completely formed (n = 43) roots were analyzed. F concentrations ranged between 39 and 550 ppm in enamel samples and between 100 and 860 ppm in dentin. Mean length and width of enamel crystallites were 257 Å (± 57 Å) and 186 Å (± 45 Å), respectively. The mean length and width of the dentin crystallites were 177 Å (± 31 Å) and 70 Å (± 18 Å), respectively. Sixty-one 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 1Go presents the data divided by location.


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  		Table 1. Descriptive Data from Montreal, Toronto, and Fortaleza
 
Enamel F concentrations in teeth collected 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 2Go. There was also positive correlation between dentin F concentration and enamel crystallite length (rs = 0.405; p < 0.001) and width (rs = 0.483; p < 0.001).


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  		Table 2. Summary of One-way ANOVA
 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
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 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 cut-off 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).

Received February 27, 2003; Last revision July 25, 2003; Accepted September 8, 2003


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
 RESULTS
 DISCUSSION
 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.[ISI][Medline]

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 long-term treatment with fluoride. Bone 9:361–365.[Medline]

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.[Abstract]

Eanes ED, Hailer AW (1998). The effect of fluoride on the size and morphology of apatite crystals grown from physiologic solutions. Calcif Tissue Int 63:250–257.[ISI][Medline]

Eastoe JE, Fejerskov O (1984). Composition of mature enamel protein from fluorosed teeth. In: Tooth enamel. Fearnhead R, Suga S, editors. Amsterdam: Elsevier, p. 326.

Everett ET, McHenry MA, Reynolds N, Eggertsson H, Sullivan J, Kantmann C, et al. (2002). Dental fluorosis: variability among different inbred mouse strains. J Dent Res 81:794–798.[Abstract/Free Full Text]

Fejerskov O, Johnson NW, Silverstone LM (1974). The ultrastructure of fluorosed human dental enamel. Scand J Dent Res 82:357–372.[ISI][Medline]

Galagan DJ, Vermillion JR (1957). Determining the optimum fluoride concentrations. Publ Hlth Rep (Wash) 72:491–493.

Garcia AI (1989). Caries incidence and costs of prevention programs. J Public Health Dent 49:259–271.[ISI][Medline]

Grynpas MD (1990). Fluoride effects on bone crystals. J Bone Miner Res 5(Suppl 1):S169–S175.

Klug H, Alexander L (1954). X-ray diffraction procedures for polycrystalline and amorphous materials. 2nd ed. Toronto: Wiley Interscience.

LeGeros R (1991). Biologically relevant calcium phosphates: preparation and characterization. In: Calcium phosphates in oral biology and medicine. New York: Karger, pp. 4-45.

Limeback H, Schlumbohm C, Sen A, Nikiforuk G (1992). The effects of hypocalcemia/hypophosphatemia on porcine bone and dental hard tissues in an inherited form of type 1 pseudo-vitamin D deficiency rickets. J Dent Res 71:346–352.

Marshall GW Jr (1993). Dentin: microstructure and characterization. Quintessence Int 24:606–617.[Medline]

Mernagh JR, Harrison JE, Hancock R, McNeill KG (1977). Measurement of fluoride in bone. Int J Appl Radiat Isot 28:581–583.[Medline]

Mestriner W Jr, Polizello AC, Spadaro AC (1996). Enamel fluoride concentrations in unerupted third molars and the influence of fluoridated water on caries scores. Caries Res 30:83–87.[ISI][Medline]

Murray JJ, Rugg-Gunn AJ, Jenkins GN (1991). Fluoride in caries prevention. 3rd ed. Oxford: Butterworth-Heinemann Ltd.

National Research Council (1993). Health effects of ingested fluoride. Washington, DC: National Academy Press.

Patterson CM, Basford KE, Kruger BJ (1976). The effect of fluoride on the immature enamel matrix protein of the rat. Arch Oral Biol 21:131–132.[ISI][Medline]

PHS (US Public Health Service) (1962). Public Health Service drinking water standards. PHS Publ. No. 956. Washington, DC: US Government Printing Office.

Posner AS, Tannenbaum PJ (1984). The mineral phase of dentin. In: Dentin and dentinogenesis. Linde A, editor. Boca Raton, FL: CRC Press, pp. 17-36.

Russell AL (1962). Dental fluorosis in Grand Rapids during the seventeenth year of fluoridation. J Am Dent Assoc 65:608–612.

Ten Cate AR (1994). Oral histology: development, structure, and function. 4th ed. St. Louis: Mosby.

Vetter U, Eanes ED, Kopp JB, Termine JD, Robey PG (1991). Changes in apatite crystal size in bones of patients with osteogenesis imperfecta. Calcif Tissue Int 49:248–250.[ISI][Medline]

Vieira AP, Hancock R, Maia R, Limeback H, Grynpas MD (2003). Is fluoride concentration in dentin and enamel a good indicator of dental fluorosis? J Dent Res (in press).

WHO (1994). Expert Committee on Oral Health Status and Fluoride Use. Fluorides and oral health. Geneva: WHO Technical Report Series, 846.

WHO (1995). Physical status: the use and interpretation of anthropometry. Geneva: WHO Technical Report Series.




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A. Vieira, R. Hancock, M. Dumitriu, M. Schwartz, H. Limeback, and M. Grynpas
How Does Fluoride Affect Dentin Microhardness and Mineralization?
J. Dent. Res., October 1, 2005; 84(10): 951 - 957.
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