Calcified Tissue International

, Volume 36, Issue 1, pp 60–63 | Cite as

Role of acid phosphate in hydroxyapatite lattice expansion

  • R. A. Young
  • D. W. Holcomb
Clinical Investigations


Questions remain about which subcomponents of human tooth enamel (TE) are responsible for its crystallographica axis being nearly 0.02Å longer than that of pure hydroxyapatite (OHAp) and contracting to that of OHAp on heating. From infrared spectroscopic and X-ray diffraction studies of a synthetic OHAp containing HPO4 and “structural” H2O, it has been concluded that HPO4 expands thea axis at the rate of ∼ 0.0015Å/ wt % but that this accounts for substantially less than one-half of the total observable contraction. The remaining, more than one-half of thea axis change, may be only partially ascribable to “structural” H2O and partially to P2O7 (formed from the HPO4), coming out of solid solution in the apatite. Some 90% of the HPO4 observed with infrared is lost in the 160–240° temperature range and more than one-half of the P2O7 observed as a separate phase is developed above that temperature and continues to increase all the way up to the 500°C, the limit of the experiments. The loss of HPO4 is accompanied by reduction of disorder or variety in the structural OH ion sites, consistent with the view that initially some of the PO4 groups neighboring the OH ions were actually HPO4 groups.

Key words

Human tooth enamel a axis HPO4 Structural H2


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  1. 1.
    Young RA, Holcomb DW (1982) Variability of hydroxyapatite preparations. Calcif Tissue Int 34:S17-S32PubMedGoogle Scholar
  2. 2.
    Sudarsanan K Young RA (1978) Structural interactions of F, Cl and OH in apatites. Acta Crystallographica B34:1401–1407Google Scholar
  3. 3.
    LeGeros RZ, Bonel G, Legros R (1978) Types of “H2O” in human enamel and in precipitated apatites. Calcif Tissue Res 26:111–118CrossRefPubMedGoogle Scholar
  4. 4.
    Holcomb DW, Young RA (1980) Thermal decomposition of human tooth enamel. Calcif Tissue Int 31:189–201PubMedGoogle Scholar
  5. 5.
    LeGeros RZ, Trautz OR, Klein E, LeGeros JP (1969) Two types of carbonate substitution in the apatite structure. Separatum Experientia 24:5–7CrossRefGoogle Scholar
  6. 6.
    Trombe J-C, Bonel G, Montel G (1968) Sur les apatites carbonatees preparees a haute temperature. Bull Soc Chim Fr, n° special, 1708–1712Google Scholar
  7. 7.
    Labarthe J-C, Bonel, G, Montel G (1973) Sur la structure et les proprietes des apatites carbonatees de type B phosphocalciques. Ann Chim t-8, no 5:289–301Google Scholar
  8. 8.
    Arends J, Davidson CL (1975) HPO4 2− content in enamel and artificial carious lesions. Calcif Tissue Res 18:65–79PubMedGoogle Scholar
  9. 9.
    Gee A, Deitz VR (1953) Determination of phosphate by differential spectrophotometry. Anal Chem No. 99, 25: 1320–1324CrossRefGoogle Scholar
  10. 10.
    Gee A, Deitz VR (1955) Pyrophosphate formation upon ignition of precipitated basic calcium phosphates. J Am Chem Soc 77:2961–2965CrossRefGoogle Scholar
  11. 11.
    Wiles DB, Young RA (1981) A new computer program for rietveld analysis of X-ray powder diffraction patterns. App Cryst 14:149–151CrossRefGoogle Scholar
  12. 12.
    Joris SJ, Amberg CH (1971) The nature of deficiency in nonstoichiometric hydroxyapatites. J Phys Chem no. 20, 75: 3167–3178CrossRefGoogle Scholar
  13. 13.
    Montel G, Bonel G, Trombe JC, Heughebaert JC, Rey C (1977) Relations entre la physico-chimie des apatites et leur comportement dans les milieux biologiques et les differents traitements industriels. In: Institut Mondial du Phosphate: First International Congress on Phosphorus Compounds Proceedings. Rabat, Morocco, 17–21Google Scholar
  14. 14.
    Winand L, Duyckaerts G (1962) Etude infrarouge de phosphates de calcium de la famille de l'hydroxylapatite. Bulletin des Societes Chimiques Belges 71:142–150Google Scholar
  15. 15.
    Young RA Some aspects of crystal structural modeling of biological apatites. Colloques internationaus, No 230Google Scholar
  16. 16.
    Elliot JC, Mackie PE, Young RA (1973) Monoclinic hydroxyapatite. Science (1969) 180:1055–1057Google Scholar
  17. 17.
    Sudarsanan K, Young RA (1969) Significant precision in crystal structural details: Holly Springs hydroxyapatite. Acta Cryst part 8, B25: 1534–1543Google Scholar

Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • R. A. Young
    • 1
  • D. W. Holcomb
    • 1
  1. 1.School of Physics and Engineering Experiment StationGeorgia Institute of TechnologyAtlantaUSA

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