title: pH and carbonate levels in developing enamel.
abstract: Our earlier studies showed that the surface of developing and calcifying enamel changes its pH alternatively along the tooth axis when stained with pH indicating dyes. Based on the pH conditions, the enamel at this stage was distinguished as neutral zone (N1 and N2) and acid zone (A1 and A2). The aim of the present study was to correlate changes of pH with proteolytic activity and crystal size of the calcifying bovine enamel. Specimens of developing bovine enamel were separated into four maturing stages using pH staining methods. Crystal chemistry of the developing enamel was investigated using thermogravimetry (TGA), ICP emission spectrometry, X-ray diffractometry (XRD) and infrared spectroscopy (IR). Previous biochemical analysis of proteolytic enzyme activity from enamel indicated that the optimal pH of the major protease was approximately pH 6.0, coinciding with the pH of the A1 zone. IR, TGA and XRD analyses showed that most of the organic components of the enamel decomposed at 580 degrees C. Higher levels of carbonate were observed in the secretory stages than in mature enamel. The Ca/P molar ratio of the enamel apatite was lower than the stoichiometric value of 1.67. These results suggest that growth and maturation of enamel apatite crystals is related to a decrease in the carbonate level and appear to be related to the alternative calcification and decomposition of enamel proteins.
authors.affiliation: Department of Biochemistry, Faculty of Dentistry, Tokyo Medical and Dental University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Takagi
authors.forename: T
authors.initials: T
authors.lastname: Ogasawara
authors.forename: J
authors.initials: J
authors.lastname: Tagami
authors.forename: M
authors.initials: M
authors.lastname: Akao
authors.forename: Y
authors.initials: Y
authors.lastname: Kuboki
authors.forename: N
authors.initials: N
authors.lastname: Nagai
authors.forename: R Z
authors.initials: RZ
authors.lastname: LeGeros
mesh_terms: D000565:Ameloblasts; D000818:Animals; D002130:Calcium Phosphates / Q000378:metabolism; D002254:Carbonates / Q000378:metabolism*; D002417:Cattle; D003743:Dental Enamel / Q000254:growth & development / Q000378:metabolism*; D003746:Dental Enamel Proteins / Q000378:metabolism; D017886:Durapatite / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D014961:X-Ray Diffraction
chemical_list: D002130:Calcium Phosphates; D002254:Carbonates; D003746:Dental Enamel Proteins; C485817:beta-tricalcium phosphate; D017886:Durapatite; C018392:tricalcium phosphate