Materials Science Photo-oxidation of Tetracycline Adsorbed on Hydroxyapatite in Relation to the Light-induced Staining of Teeth

Abstract

In an attempt to understand the chemistry of the light-induced staining of children's teeth by tetracycline, we studied the photochemical behavior of tetracycline adsorbed on hydroxyapatite, as a simple model of enamel. Tetracycline was strongly bound by hydroxyapatite to give a pale yellow material which, under ultraviolet light, showed a bright yellow fluorescence (λ_max 525 nm). On exposure of this material to the radiation from a medium-pressure mercury lamp, the fluorescence gradually disappeared, and a red-purple product was formed. Photo-acoustic spectroscopy was employed to follow the disappearance of tetracycline and the concomitant formation of the red-purple product, the spectrum of which (λ_max 530 nm) led to the conclusion that it was 4α, 12α-anhydro-4-oxo-4-dedimethylaminotetracycline (AODTC). This assignment was supported by the observation that 1 mole of oxygen was absorbed per mole of adsorbed tetracycline converted to the red-purple product.

It is suggested that the formation of AODTC on hydroxyapatite probably takes place by a mechanism of photo-oxidation similar to that already proposed for solutions of tetracycline, and that the formation of AODTC in children's teeth is responsible for the light-induced staining caused by tetracycline.

Get full access to this article

View all access options for this article.

References

Bennick, A. ; Cannon, M. ; and Madapallimattam, G. (1979): The Nature of the Hydroxyapatite Binding Site in Salivary Acidic Proline-Rich Proteins, Biochem J 183:115-126.

Davies, A.K. ; McKellar, J.F. ; Phillips, G.O. ; and Reid, A.G. (1979): Photochemical Oxidation of Tetracycline in Aqueous Solution, J Chem Soc Perkin Trans II:369-375.

Hlavka, J.J. and Bitha, P. (1966): Photochemistry IV. A Photodeamination, Tetrahedron Lett:3843-3846.

Ibsen, K.H. ; Urist, M.R. ; and Sognnaes, R.F. (1965): Differences among Tetracyclines with Respect to the Staining of Teeth, J Pediatr 67:459462.

Johnson, R.H. and Mitchell, D.F. (1966): The Effects of Tetracyclines on Teeth and Bones , J Dent Res 45:86-93.

Lambrou, D.B. ; Tahos, B.S. ; and Lambrou, K.D. (1977): In Vitro Studies of the Phenomenon of Tetracycline Incorporation into Enamel, J Dent Res 56:1527-1532.

Reid, J.S. and Newman, P. (1977): Bleaching Tetracycline Stained Vital Teeth: Results of a Pilot Study, J Dent Res 56: D102.

Renson, R.E. , quoted in Health Shock by Martin Weitz, Newton Abbot, London: David and Charles, 1980, p. 184.

Rosencwaig, A. : Photoacoustics and Photoacoustic Spectroscopy. In: Chemical Analysis: A Series of Monographs on Analytical Chemistry and its Applications, Vol. 57, Elving, P.J. , Winefordner, J.D. , and Kolthoff, I.M. , Eds., New York: John Wiley and Sons, 1980, pp. 132-136.

10.

Wallman, I.S. and Hilton, H.B. (1962): Teeth Pigmented by Tetracycline, Lancet 1:827-829.

11.

Wiebe, J.A. and Moore, D.E. (1977): Oxidation Photosensitised by Tetracyclines, J Pharm Sci 66:186-189.

12.

Wilkes, P.D. and Leach, S.A. (1979): Adsorption of Human Submandibular Salivary Proteins to Hydroxyapatite, J Dent Res 58:1249.

13.

Witkop, C.J. and Wolf, R.O. (1963): Hypoplasia and Intrinsic Staining of Enamel Following Tetracycline Therapy, JAMA 185 :100-103.