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Effect of fluoride concentration in pH 4.3 and pH 7.0 supersaturated solutions on the crystal growth of hydroxyapatite

Effect of fluoride concentration in pH 4.3 and pH 7.0 supersaturated solutions on the crystal growth of hydroxyapatite

Article information

Restor Dent Endod. 2012;37(1):16-23
Publication date (electronic) : 2012 March 02
doi : https://doi.org/10.5395/rde.2012.37.1.16
1Department of Conservative Dentistry, Yonsei University College of Dentistry, Seoul, Korea.
2Department of Conservative Dentistry, Gangnam Severance Hospital, Yonsei University College of Dentistry, Seoul, Korea.
Correspondence to Chan-Young Lee, DDS, MSD, DDSc. Professor, Department of Conservative Dentistry, Yonsei University College of Dentistry, 50 Yonsei-ro, Seodaemun-gu, Seoul, Korea 120-752. TEL, +82-2-2228-8701; FAX, +82-2-313-7575; chanyoungl@yuhs.ac
Received 2011 December 17; Revised 2012 January 13; Accepted 2012 January 20.

Abstract

Objectives

Present study was undertaken to investigate the crystal growth onto synthetic hydroxyapatite (HA) seeds in pH 4.3 and pH 7.0 supersaturated solutions with different fluoride concentrations.

Materials and Methods

8 groups of pH 4.3 and 7.0 calcium phosphate supersaturated solutions were prepared with different fluoride concentrations (0, 1, 2 and 4 ppm). Calcium phosphate precipitates yield crystal growth onto the HA seed surface while solutions flow. For evaluation of crystallizing process, the changes of Ca2+, PO43-, F- concentrations of the inlet and outlet solutions were determined. The recovered solid samples were weighed to assess the amount of minerals precipitated, and finally determined their composition to deduce characteristics of crystals.

Results

During the seeded crystal growth, there were significantly more consumption of Ca2+, PO43-, F- in pH 4.3 solutions than pH 7.0 (p < 0.05). As fluoride concentration increased in pH 4.3 solution, Ca2+, PO43-, F- consumption in experimental solutions, weight increment of HA seed, and fluoride ratio in crystallized samples were increased. There were significant differences among the groups (p < 0.05). But in pH 7.0 solution, these phenomena were not significant. In pH 7.0 solutions, analyses of crystallized samples showed higher Ca/P ratio in higher fluoride concentration. There were significant differences among the groups (p < 0.05). But in pH 4.3 solution, there were not significant differences in Ca/P ratio.

Conclusions

Crystal growth in pH 4.3 solutions was superior to that in pH 7.0 solutions. In pH 4.3 solutions, crystal growth increased with showed in higher fluoride concentration up to 4 ppm.

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Article information Continued

Figure 1

Schematic illustration of experimental set-up.

Figure 2

Schematic illustrations of calculating the amounts of crystal growth. (a) Amounts of seed crystals oriinally placed in the reaction column; (b) Weighed amounts of solid sampe recovered at the end of experiment; (b)-(a) Difference between (b) and (a), amounts of crystal growth.

Table 1

Initial composition of experimental solutions

Table 1

Table 2

Changes in compositions of the experimental solution after experiments (Mean ± SD, n = 10)

Table 2

SD, standard deviation; NM, not measurable, no fluoride was added to the experimental solutions.

Different letters denote statistically different (p < 0.05).

Table 3

Weight increments of the HA seed after crystal growth (Mean ± SD, n = 10)

Table 3

SD, standard deviation.

Different letters denote statistically different (p < 0.05).

Table 4

Molecular ratio in crystallized samples (Mean ± SD, n = 10)

Table 4

SD, standard deviation.

*1 sample is missed in two groups (groups 6 and 8, n = 9).

Different letters denote statistically different (p < 0.05).