Effect of different water-to-powder ratios on the compressive strength of Root-MTA(mineral trioxide aggregate)

Abstract

Introduction MTA (Mineral trioxide aggregate) is an endodontic biomaterial that is used for various applications such as perforations repair and direct pulp cap. This material can be affected by pressures of restoration material compaction and mastication. Therefore, compressive strength which is representative of its resistance against crushing, is important. The first commercial brand of MTA is ProRoot MTA. Since ProRoot MTA was high-cost, researchers developed other similar products. Root-MTA has been investigated by Dr. Lotfi in Tabriz university of medical sciences. Several published studies have represented the desired properties of Root-MTA in comparison to ProRoot MTA. The aim of this study was to evaluate the effect of various water-to-powder ratios on compressive strength of Root-MTA.

Methods and materials Root-MTA was mixed with distilled water in 3 groups of 13 specimens with different water-to-powder ratios including 1 to 2, 1 to 3 and 1 to 4. Then, obtained mixture, was gradually poured into stainless steel mold and compacted by condenser with moderate force. The internal diameter and the height of holes of the mold was 4 and 6 mm, respectively. Wet pieces of gauze were placed on top of the mold. Then, the specimens were incubated at 37°C in 100% humidity. After seven days, the samples were removed from the incubator. After removal, the samples were visually evaluated for lack of voids or cracks. They were submitted to compressive strength tests using a universal testing machine. The maximum load needed to fracture each specimen was recorded.

Statistical analysis After performing descriptive analyses, normality assumption was verified with the one-sample Kolmogorov-Smirnov test. Due to the normal distribution of data, the comparison between 3 groups was carried out by performing one-way ANOVA. The results were reported as means ± SDs. The statistical analyses were performed using SPSS Statistics software, version 25.

Results The highest compressive strength value was observed respectively in the groups with water-to-powder ratio of 0.25 and 0.34. The group with water-to-powder ratio of 0.5 showed the lowest compressive strength. The differences among the various ratios were statistically significant (P-value<0.05).

Conclusion Compressive strength of Root-MTA decreases by increasing water-to-powder ratio.

Keywords: Root-MTA, compressive strength, water-to-powder ratio