Zeta Potentials of Human Enamel and Hydroxyapatite as Measured by the Coulter® DELSA 440

Abstract

The zeta potential of human enamel is of physiological importance for interactions between enamel surfaces and the surrounding aqueous medium of saliva. The zeta potentials of both enamel and hydroxyapatite (HA) have been examined previously by various techniques. In this study, we examined the zeta potential of human enamel and HA using the Coulter DELSA 440, which, by a laser, makes independent Doppler shift measurements of moving particles in an electric field at 4 different angles, providing advantages over previous techniques. The enamel and HA particles were suspended directly in different phosphate buffers, or first incubated for 2 hrs in parotid (PS) or whole saliva (HWS) and then suspended in the same buffers. The enamel and HA particles exhibited an overall net surface potential of -15 to -30 mV, depending on the buffer content. Incubation in PS and HWS gave less negative potentials of -8 to -14 mV. In our previous studies, the salivary micelle-like structures (SMSs), seen in TEM of parotid saliva, were observed to have a zeta potential of -9 mV (Rykke et al., 1996). The zeta potential determinations in this study support the concept of an adsorption of mostly SMSs to the enamel surfaces, with a change of the zeta potential of the enamel and HA toward that of the SMSs.

Effect of Zeta Potentials on Bovine Serum Albumin Adsorption to Hydroxyapatite Surfaces

“…In a study by Young 15) , the zeta potentials of human enamel and hydroxyapatite particles became less negative after adsorption of parotid or whole saliva. In a study by Shimomura 11) , the zeta potential of the surfaces of hydroxyapatite plates became less negative after protein adsorption.…”

Synthesis of hybrid copper-chitosan nanoparticles with antibacterial activity against cariogenic <i>Streptococcus mutans </i>

“…It has been reported that chitosan is capable of interfering with S. mutans adhesion and primary biofilm formation [21][22][23] . Chitosan is also known as a bioadhesive polymer 24) that may interact with the negatively charged hydroxyapatite surface of enamel as well as with the negative cell wall of biofilm bacteria 25) . These kinds of interactions would be responsible of the higher copper retention on the biofilm/enamel surface (EDX mapping) and the improved anti-biofilm action exhibited by CuChNP.…”

The Future of Fluorides and Other Protective Agents in Erosion Prevention

“…It has been suggested that chitosan can form a layer-by-layer build-up on dental enamel, providing better protection against erosive attacks . This layer is formed because chitosan has a strong positive zeta potential, and it can readily adsorb to surfaces with a strong negative zeta potential [Claesson and Ninham, 1992], such as enamel [Young et al, 1997]. Chitosan was also shown to adsorb onto salivary pellicle proteins [Sano et al, 2001;van der Mei et al, 2007].…”