(PO97) In Vitro Assessment of the Thermal Stability, pH, and Antimicrobial Activity of Candida Albicans of Mixtures of Varying Concentrations of Polyethylene Glycol 1000 (PEG 1000) and Calcium Hydroxide (Ca(OH)₂)

Abstract: Calcium hydroxide Ca(OH)₂ is a commonly used intracanal medicament in endodontics due to its antimicrobial properties and physical barrier function. The mechanism of action is based on the release of highly reactive hydroxyl ions, which cause damage to the bacterial cytoplasmic membrane, DNA, and proteins. Iatrogenic events can occur if calcium hydroxide is extruded past the apex of a tooth. The aim of this research is to determine the concentration of polyethylene glycol (PEG) 1000 and calcium hydroxide at which the mixture is solid at room temperature (68-72°F) and liquid at body temperature (97-99°F), measure the pH at each concentration, and evaluate the antimicrobial activity of these mixtures against Candida albicans. The liquification temperature of a total of 10 g with concentrations of 75% PEG 1000 and 25% Ca(OH)₂, 50% PEG 1000 and 50% Ca(OH)₂, 25% PEG 1000 and 75% Ca(OH)₂ were observed. pH levels were tested for each sample and recorded. Candida albicans samples were prepared and inoculated with mixtures of calcium hydroxide and/or chlorohexidine, and resultant zones of inhibition were measured. Blending 25% Ca(OH)₂ with 75% PEG 1000 yielded a solid-state composition that remained stable until reaching the critical temperature threshold of 30°C, potentially creating a mixture that circumvents undesired material extrusion out of the apex of the tooth. When the mixture contained higher concentrations of calcium hydroxide, a higher pH was detected. Results showed no effect of any concentration of calcium hydroxide and PEG 1000 mixtures against Candida albicans, except when mixed with 2% chlorhexidine (p < .05) and CI: 98%..