The Relationship between Surface Free-Energy and Kinetics in the Mineralization and Demineralization of Dental Hard Tissue

Abstract

The interfacial free-energy is an important factor in the regulation of mineralization and dissolution at the surfaces of dental hard tissues. However, few thermodynamic studies have been aimed at the elucidation of the interfacial terms. Contact angle measurements (sessile drop and thin layer wicking) and kinetic dissolution and growth techniques have been used to study the interfacial properties of root dentin (D), human enamel (E), and hydroxyapatite (HAP). The interfacial tensions between water (w) and each of these phases were calculated from contact angle data according to surface tension components theory. The values γ_wD = 4.5 x 10^-3J m^-2, γ_wE = 8.8 x 10^-3J m^-2, and γ_w,HAP = 10.4 x 10^-3J m^-2 were of the same order of magnitude as those obtained from dissolution kinetic data (pH = 4.5): γ_wD = 1.4 x 10^-3J m^-2, γ_wE = 3.2 x 10-3J m^-2, and γ_wHAP = 9.3 x 10^-3J m^-2. Kinetics studies of the crystallization of HAP on HAP, dentin, and enamel yielded the interfacial free-energy values, γ_wHAP = 17.1 x 10^-3J m^-2, 17.7 x 10-3J m^-2, and 9.4 x 10-3J m^-2, respectively, probably reflecting the interfacial energies of the deposited phases rather than those of the dental hard-tissue substrata. The lower interfacial tension values are consistent with the higher solubilities of these solid phases: logKso = -52.0, -55 - 57, and -58 - 59, for root dentin, enamel, and HAP, respectively, expressed as an equivalent HAP ionic product. The higher interfacial free-energy is also consistent with the slower mineralization of HAP on dentin and enamel surfaces.

Keywords

surface free energy interfacial tension mineralization demineralization dental hard tissue enamel solubility contact angle

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References

Amjad Z. , Koutsoukos PG , Nancollas GH (1981). The mineralization of enamel surface. J Dent Res 60 :1783-1792.

Arends J. , Jongebloed WL (1977). Mechanism of enamel dissolution and its prevention . J Biol Buccale 5:219-237.

Arends J. , Christoffersen J. , Christoffersen MR , Schuthof J. (1983). Influence of fluoride concentration on the progress of demineralization in bovine enamel at pH = 4.5. Caries Res 65:455-457.

Bates RG (1973). pH determination, theory and practice. New York: John Wiley.

Bennema P. (1967). Analysis of crystal growth models for slightly supersaturated solutions. J Cryst Growth 1:278-286.

Brauer GM , Wiedeman WH (1964). Measurement of the surface area and heats of wetting of dentin powders. J Dent Res 43:921-926.

Budz JA , Lore M. , Nancollas GH (1987). Hydroxyapatite and carbonated apatite as models for the dissolution behavior of human dental enamel. Adv Dent Res 1:314-312.

Burton WK , Cabrera N. , Frank FC (1951). Growth of crystals and the equilibrium structure of their surfaces. Phil Trans R Soc London A 243:299-358.

Chen WC , Nancollas GH (1986). The kinetics of dissolution of tooth enamel-a constant composition study. J Dent Res 65:663-668.

10.

Christoffersen J. , Christoffersen MR (1992). A revised theory for the growth of crystals by surface nucleation. J Cryst Growth 121:608-616.

11.

de Jong HP , van Pelt Awj , Arends J. (1981). Contact angle measurements on human enamel-an in vitro study of influence of pellicle and storage period. J Dent Res 61:11-13.

12.

de Jong HP , de Boer P. , Busscher HJ , van Pelt Awj , Arends J. (1984). Surface free energy changes of human enamel during pellicle formation. Caries Res 18:408-415.

13.

Ebrahimpour A. , Zhang J. , Nancollas GH (1991). Dual constant composition method and its application to studies of phase transformation and crystallization of mixed phases. J Cryst Growth 83-91.

14.

Foreman PC , Soames JV (1989). The vulnerability of primary and secondary dentin . J Dent Res 65:955-958.

15.

Fuierer TA (1996). A dual constant composition study of the mineralization kinetics of hydroxyapatite and human dental enamel (PhD dissertation). Buffalo, NY SUNY at Buffalo.

16.

Glantz P. -O (1969). On wettability and adhesiveness. Odontol Revy (Suppl 20) 17:5-132.

17.

Glantz P-O. , Nyquist G. (1966). The effect of topical fluorine application on the surface free energy of dentin. Odontol Revy 17:332-338.

18.

Gray JA ( 1962). Kinetics of the dissolution of human dental enamel in acid. J Dent Res 41 :633-645.

19.

Head J. ( 1912). A study of saliva and its action on tooth enamel in reference to its hardening and softening. J Am Dent Assoc 59:2118-2122.

20.

Heughebaert JC , Nancollas GH (1984). Kinetics of crystallization of octacalcium phosphate . J Phys Chem 88:2478-2481.

21.

Hunter RJ (1981). Zeta potential in colloid science. London: Academic Press.

22.

Israelachvili JN (1991). Intermolecular and surface forces. San Diego, CA: Academic Press.

23.

Koutsoukos PG , Nancollas GH (1981). The kinetics of mineralization of human dentin in vitro. J Dent Res 60:1922-1928.

24.

Larsen MJ , Pearce Eif , Jensen SJ (1993). Note on the dissolution of human dental in dilute acid solution at high solid/solution ratio. Caries Res 27:87-95.

25.

Liu Y. , Nancollas GH (1996). Fluorapatite growth kinetics and the influence of solution composition. J Cryst Growth 165:116-123.

26.

Liu Y. , Sethuraman G. , Wu W. , Nancollas GP , Grynpas G. (1997). The crystallization in the presence of hydroxyapatite seeds and of hydroxyapatite in the presence of fluorapatite seeds. J Colloid Interf Sci 186:102-109.

27.

Margolis HC , Moreno EC (1985). Kinetic and thermodynamic aspects of enamel demineralization . Caries Res 19:22-35.

28.

McCann HG (1968). The solubility of fluorapatite and its relationship to that of calcium fluoride. Arch Oral Biol 13:987-1001.

29.

McDowell H. , Gregory TM , Brown EW (1977). Solubility of Ca5(PO4)3OH in the system Ca(OH)2-H3PO4-H2O at five, 15, 25, and 37°C (abstract). J Res Natl Bur Stds 81:273.

30.

Mullin JW , Ang NM (1976). Nucleation characteristics of aqueous nickel ammonium sulphate solutions. Disc Faraday Soc 61:141-148.

31.

Nancollas GH (1997). Unpublished data.

32.

Newman GV , Sharpe LH (1966). On the wetting of tooth surfaces. J NJ Dent Soc 37:289-306.

33.

Nielsen AE (1964). Kinetics of precipitation. New York: Pergamon Press.

34.

Nielsen AE (1980). Transport control in crystal growth from solution . Croat Chem Acta 53:255-279.

35.

Nielsen AE (1984). Electrolyte crystal growth mechanisms. J Cryst Growth 67:289-310.

36.

Nielsen AE , Christoffersen J. (1982). The mechanism of crystallization and dissolution . In: Biological mineralization and demineralization. Nancollas GH , editor. Berlin, Germany: Dahlem Konferenzen, pp. 37-77.

37.

Nielsen AE , Sohnel 0 (1971). Interfacial tension electrolyte crystal-aqueous solution, from nucleation data. J Cryst Growth 11:233-242.

38.

Ohara M. , Reid RC , (1973). Modeling crystal growth rates from solution. Englewood Cliffs, NJ: Prentice-Hall, Inc.

39.

Pickerill HP (1918). Untenable position with regard to the problem of the immunity to dental caries. Dent Rec 38:337-345.

40.

Shellis RP , Wahab FK , Heywood BR (1993). The hydroxyapatite ion activity product in acid solutions equilibrated with human enamel at 37°C. Caries Res 27:365-372.

41.

Shyu LJ , Perez L. , Zawacki S. , Heughebaert JC , Nancollas GH (1983). The solubility of octacalcium phosphate at 37°C in the system Ca(OH)-H3PO4-KNO3-H2O. J Dent Res 62:398-400.

42.

Sohnel 0 (1982). Electrolyte crystal-aqueous solution interfacial tensions from crystallization data. J Cryst Growth 57:101-108.

43.

Sohnel 0 , Mullin JW (1988). Interpretation of crystallization induction periods . J Colloid Interf Sci 123:43-50.

44.

Souder W. , Schoonover IC (1944). Experimental remineralization of dentin. J Am Dent Assoc 31:1579-1586.

45.

Tan J. (1995). The mineralization and demineralization kinetics of synthetic hydroxyapatite and human dentin (PhD dissertation). Buffalo, NY SUNY at Buffalo.

46.

van Oss CJ (1994). Interfacial forces in aqueous media. New York: Marcel Dekker, Inc.

47.

van Oss CJ , Chaudhury MK , Good RJ ( 1988). Interfacial Lifshitz-van der Waals and polar interactions in macroscopic systems. Chem Rev 88:927-941.

48.

Ware BR ( 1974). Electrophoretic light scattering. Adv Colloid Interf Sci 4:1-44.

49.

Washburn EW (1921). The dynamics of capillary flow. Phys Rev 17:273-283.

50.

Wu W. , Nancollas GH (1997a). Nucleation and crystal growth of octacalcium phosphate on titanium oxide surfaces. Langmuir 13:861-865.

51.

Wu W. , Nancollas GH (1997b). Nucleation and crystal growth of hydroxyapatite and fluorapatite on titanium oxide surfaces. Colloids & Surfaces B (in press).