title: Changes in acid-phosphate content in enamel mineral during porcine amelogenesis.
abstract: The present study was undertaken to investigate changes in the acid-phosphate content of porcine enamel mineral during its development and to assess separately the HPO4(2-) pools in labile and stable forms. Enamel samples at the secretory and maturing stages of amelogenesis were obtained from the permanent incisors of five- to six-month-old slaughtered piglets. Human enamel from erupted, extracted teeth, synthetic hydroxyapatite, and carbonatoapatite containing acid phosphate were included as references. The acid-phosphate content of each sample was determined chemically through its pyrolytic conversion to pyrophosphate. The assessment of HPO4(2-) in labile forms was made by analysis of samples preequilibrated with solutions containing 3 mmol/L phosphate at pH11 (to de-protonate the HPO4(2-) species on crystal surfaces). The analytical results of porcine enamel samples showed that: (a) the outermost secretory (youngest) enamel contained the highest HPO4(2-), corresponding to about 16% of the total phosphate; (b) the acid-phosphate content decreased gradually to 10% in the inner (older) secretory and to 6% in the maturing tissue; (c) a substantial part of the HPO4(2-) in developing enamel tissue (50-60% of the HPO4(2-) for the secretory enamel) was in labile forms; and (d) the pool of the labile HPO4(2-) decreased with the growth of enamel mineral. In parallel studies with mature human enamel, it was ascertained that the total acid phosphate was only about 3% of the total phosphate, much lower than in developing porcine enamel, and that the labile pool of HPO4(2-) was also small, corresponding to about 15% of the total acid phosphate determined.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Forsyth Dental Center, Boston, Massachusetts 02115.
authors.forename: S
authors.initials: S
authors.lastname: Shimoda
authors.forename: T
authors.initials: T
authors.lastname: Aoba
authors.forename: E C
authors.initials: EC
authors.lastname: Moreno
mesh_terms: D000566:Amelogenesis / Q000502:physiology; D000818:Animals; D001031:Apatites / Q000032:analysis; D002021:Buffers; D002118:Calcium / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis; D002254:Carbonates / Q000032:analysis; D003461:Crystallography; D003743:Dental Enamel / Q000737:chemistry* / Q000648:ultrastructure; D003746:Dental Enamel Proteins / Q000032:analysis; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008854:Microscopy, Electron; D010710:Phosphates / Q000032:analysis*; D012972:Sodium Hydroxide / Q000737:chemistry; D013552:Swine
chemical_list: D001031:Apatites; D002021:Buffers; D002130:Calcium Phosphates; D002254:Carbonates; D003746:Dental Enamel Proteins; D010710:Phosphates; D012972:Sodium Hydroxide; D002118:Calcium