Method: Samples from eleven commercial MTA-type cements were used: Avalon Biomed (Bradenton, USA), Angelus, (Londrina, Brazil), BioMTA (Seoul, Republic of Korea), Dentsply Tulsa Dental (Johnson City, USA), Maruchi (Wonju, Republic of Korea), MicroMega (Besancon, France), Septodont (Saint Maur des Faussés, France) and VladMiVa (Belgorod, Russia). Two grams of each cement was employed for particle size analysis using laser diffraction. The refractive index was determined by using the weighted average of the refractive indices of ingredients of each cement. The standard reference points of particle size were compared between samples, and linear correlation coefficients the logarithmic relationship with setting time calculated. Setting time data was received from manufacturers who performed indentation setting time tests as specified by ISO 6786 (n=9) and ISO 9917.1 (n=2).
Result: No correlation existed with d10 (r=0.067) and a weak positive correlation was found for d50 (r=0.219). In contrast, a strong positive correlation (r=0.554) exists for d90 in the logarithmic regression model with the matching equation for setting time being t=103.59ln(d90)-184.43.
Conclusion: Commercial MTA-type cements contain components that may accelerate or retard the setting time of the cement. Nevertheless, the larger boundary of the 90th percentile of particle size shows a strong positive correlation with the setting time of MTA.