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.

Function and repair of dental enamel – Potential role of epithelial transport processes of ameloblasts

“…Acid/base conditions play an important role during the biomineralization process of enamel hydroxyapatite since the crystal growth on a delicate cellular control of the ionic composition and pH of the extracellular fluid [41]. The control of these parameters is primarily achieved by ameloblasts [42].…”

Role of NBCe1 and AE2 in Secretory Ameloblasts

“…The proton production rate and the bicarbonate secretory rate likely change temporally, given the pH differences that exist, depending on the ameloblast stage. Specifically, the net pH during the secretory stage is near neutral and becomes acidic during the transition stage, and modulates between neutral and acidic during the maturation stage (Sasaki et al, 1991;Takagi et al, 1998).…”

“…Apatite crystal growth, proteinase activity in the extracellular space, and the triggering of ameloblast morphologic changes are thought to be pHdependent phenomena requiring that cellular transport processes controlling the extracellular fluid pH be coordinated in a highly controlled fashion (Smith, 1998;Takagi et al, 1998).…”

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…During maturation of enamel, the mineral content increases from initially *45 wt.% up to *98-99 wt.% (Avery 2001; Nanci 2012; Bonar et al 1991). The enamel crystal rods widen and thicken by additional growth (Rey et al 1995b;Bonar et al 1991;Smith 1998) with a simultaneous increase of the Ca/P molar ratio (Smith 1998) and a decrease in carbonate content (Sydney-Zax et al 1991;Rey et al 1991;Takagi et al 1998), finally resulting in the most highly mineralized and hardest substance produced by vertebrates. It is interesting to note that in the radular teeth of chitons, ACP was found to be the first-formed CaPO 4 mineral, which over a period of weeks was transformed to dahllite (Lowenstam and Weiner 1985).…”