Effect of varying water-to-powder ratios on the setting expansion of white and gray mineral trioxide aggregate.

Introduction: Clinicians commonly mix mineral trioxide aggregate (MTA) to a desired consistency rather than use the recommended amounts of powder and water. The purpose of this in vitro study was to evaluate how varying the water-to-powder (WP) ratio affects the setting expansion of white MTA (WMTA) and gray MTA (GMTA).

Methods: Eight combinations (n = 5) of WMTA and GMTA were mixed using varying WP ratios. Randomized samples were placed in a linear variable displacement transformer and submerged under Hank's balanced salt solution for 25 hours. Expansion was compared using a 2-way analysis of variance (alpha = 0.05).

Results: Mean percent expansions ranged from 0.058%-0.093% for WMTA and 2.15%-2.56% for GMTA. GMTA expanded significantly more than WMTA at p = .001. No differences in expansion were found between WP ratios (p = .218). No significant interaction was found between the WP ratio and material type (p = .228).

Conclusions: GMTA expanded significantly more than WMTA; however, varying the WP ratio did not affect the setting expansion.