Comparision and compressive strength of white MTA with or without adding Na2Hpo4 in different liquid to powder ratio

Abstract

MTA has been used in vital pulp therapy, furcal and lateral perforation repair, as an apical plug in non-vital teeth with open apices and as a root-end filling material during apical surgery. However, the initial reaction of inflammatory cells to this MTA and its setting time are not favorable. Studies have shown that Na2HPO4, as an MTA accelerator, decreases its setting time but does not change its pH. In this study the effect of various liquid-to-powder ratios on the compressive strength of WMTA and mixture of MTA and Na2HPO4 (NAMTA) was evaluated. Materials and methods: A total of 120 samples were placed in a two-segment stainless steel mold with two holes measuring 6 mm in height and 4 mm in diameter for compressive strength test. In 60 samples WMTA and in 60 samples a 2.5-wt% mixture of Na2HPO4 and MTA were placed. The compressive strengths of the samples were measured at different liquid-to-powder ratios of 0.50, 0.60, and 0.70 at 24-hour and 21-day intervals. Two-way ANOVA was used to evaluate inter-group differences. If there were differences, appropriate post hoc tests or non-parametric Kruskal-Wallis and Wilcoxon-Wallis tests were used. Statistical significance was defined at P<0.05. Results: The type of the material (WMTA and NAMTA) had no effect on the compressive strength (P=0.205, Z=1.268). Kruskal-Wallis test showed significant differences in compressive strengths between the three different material ratios (chi-squared=15.054, Df=2, P=0.01). Mann-Whitney U test was used for the two-by-two comparison of the groups, which revealed no significant differences between 0.50 and 0.60 groups; however, there were significant differences between 0.70 group and both 0.50 and 0.60 groups. Conclusion: The compressive strength of NAMTA at 0.50 and 0.60 liquid-to-powder ratios is similar to that of MTA.