Electro Kinetic Properties of Colloidal Dental Wastewater. 

H. BATCHU, C. A. NALEWAY, P. L. FAN, and D. MEYER [American Dental Association Health Foundation, Chicago, IL] 
and M. STONE [Naval Dental Research Institute, Great Lakes, IL, USA] 

Dental wastewater contains amalgam particulates ranging from large to colloidal particles. Earlier studies (IADR, Abst # 25, 1994 and IADR Abst # 1101, 1995) on particulate size distributions showed that about 10% by weight of the total particles in the wastewater is in the colloidal form. In order to devise methods to remove these colloidal particles efficiently, the characterization of the particulates is important. The supernatant from clinical wastewater after several hours of settling, consisting colloidal particles, was removed for evaluation. The zeta potential of colloidal particles was measured using a Doppler Electrophoretic Light Scattering Analyzer (Coulter DELSA 440). For the clinical samples the zeta potential distributions were bi-modal, one peak at 32 mV was identified to be associated to enamel and the other peak at 28 mV was identified to be associated with amalgam. Amalgam particles (Tytin) and hydroxyapatite particles were also suspended separately in deionized water and the zeta potential was found to be -13 mV and –23 mV, respectively. By pH profile measurements the iso-electric point of the dental wastewater (disinfected with bleach) is found to be around pH 3.8. [Journal of Dental Research, 75:37 #163, 1996]

NDRI Dental Mercury Environmental Issues