Preparation and physicochemical evaluation of paste-paste calcium hydroxide based dental cement and the effect of replacement of glycol disalicylate by methyl salicylate on its basic properties

Abstract

Dycal® is a paste-paste calcium hydroxide dental cement uses as pulp capping and liner in dentistry. First paste (base paste) contains titanium dioxide and barium sulphate in glycol disalicylate and second paste (catalyst paste) contains calcium hydroxide, zinc oxide and zinc stearate in ethyl toluene sulphonamide. Equal amounts of base and catalyst paste were mixed together and a hard mass is obtained after a certain time. The set material consists of TiO2, ZnO (fillers), BaSO4 (radiopacifier) and free unreacted Ca(OH)2 dispersed in an amorphous calcium phenolate matrix. This unreacted calcium hydroxide is responsible for biological properties of Dycal® (antibacterial and formation of reparative dentin). In this research Dycal® has been fabricated and furthermore glycol disalicylate was gradually replaced by methyl salicylate up to 20 % in base paste. Cements were characterized by X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) and scanning electron microscopy (SEM). Also effect of the replacement was investigated on setting time, water solubility, pH and compressive strength of the cement. Results showed that unreacted calcium hydroxide decreased in set cement when methyl salicylate increase in base paste and therefore, and pH of distilled water containing cement decrease by this replacement. Setting time and water solubility also decreased when methyl salicylate increased in base paste (from 5.5 to 3 min and 4.5% to 2.5% respectively). The compressive strength showed no changes by this replacement.