Effect of different water to power ration on the solubility and microhardness of a bioactive material an in vitro study

Abstract

CONTEXT (BACKGROUND): Insolubility and good microhardness are important criteria for an ideal bioactive material to prevent any microleakage between the root canal and the periradicular space and provide sealing ability when used as root-end filling, root perforation repair, orthograde obturation and apical plug formation material. AIM: To evaluate the effect of changes in the ratio of liquid to powder on the solubility and weight changes in synthetic tissue fluid/ Phosphate buffer solution and microhardness of OrthoMTA. MATERIALS AND METHOD: One gram of OrthoMTA powder was mixed with 0.5 mL, 0.4 mL and 0.33 mL of distilled water. For solubility, a total of 60 specimens were prepared (n=20 per each ratio) in the disk- shaped polycarbonate moulds with a height of 2 mm and internal diameter of 4 mm. The specimens of each water-topowder ratio were randomly divided into two subgroups: half (n=10) were immersed for 7 days and the other half (n=10), were immersed for 28 days in Synthetic tissue fluid/ Phosphate buffer solution. The weight change in the specimens were calculated. To measure microhardness, a total of 30 specimens were prepared (10 per each ratio, n=10). The mixtures were transferred to two-part split polycarbonate moulds with an internal diameter of 4 mm and height of 6 mm. After 4 days the samples were subjected to Vicker's test. The data were analysed using ANOVA, Paired t test and post-hoc Bonferroni tests at a significance level of 0.05. RESULT: The 0.33 water-to-powder ratio showed significantly greater mean microhardness value (23.42±1.24) compared to 0.4 and 0.5 ratios (18.63±0.89, 13.62±1.29 respectively). Statistical analysis revealed that there were no significant differences in the weight changes and percentage weight changes between the experimental groups. However, Group III showed highest weight gain after immersion in synthetic tissue fluid for 28 days. CONCLUSION: Higher WP ratios result in lower microhardness and lower the amount of weight gain in OrthoMTA. Therefore, the 0.33 water-to-powder ratio would be the ideal proportion.