Our earlier studies showed that the surface of developing and calcifying en
amel 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 ai
m of the present study was to correlate changes of pH with proteolytic acti
vity and crystal size of the calcifying bovine enamel. Specimens of develop
ing bovine enamel were separated into four maturing stages using pH stainin
g methods. Crystal chemistry of the developing enamel was investigated usin
g thermogravimetry (TGA), ICP emission spectrometry, X-ray diffractometry (
XRD) and infrared spectroscopy (IR). Previous biochemical analysis of prote
olytic enzyme activity from enamel indicated that the optimal pH of the maj
or protease was approximately pH 6.0, coinciding with the pH of the Al zone
, IR, TGA and XRD analyses showed that most of the organic components of th
e enamel decomposed at 580 degrees C. Higher levels of carbonate were obser
ved 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 r
esults suggest that growth and maturation of enamel apatite crystals is rel
ated to a decrease in the carbonate level and appear to be related to the a
lternative calcification and decomposition of enamel proteins.