(PO144) The Effect of Particle Size on the Setting Time of a Bioceramic Sealer

Abstract: In 1981, Dr. Grossman outlined his famous criteria for ideal sealer properties. Although the particle size may influence almost all of these criteria, existing research remains sparse on the optimal particle size for endodontic sealers. The objective of this project was to evaluate the effect of particle-size reduction in a commercially available bioceramic sealer on the setting time. The initial particle-size reduction used a modified form of the ADA ISO standard for sealers. The initial particle-size characterization of calcium silicate and zirconia powder from BioRoot bioceramic sealer was accomplished using SEM images and ImageJ software. A particle-size reduction process was done after increasing the time of ball milling using a speed mixer. The obtained particle sizes ranged from 1.89 microns to 5.39 microns. These reduced sealer particles were grouped based on their particle size and mixed with liquid per manufacturer’s instructions, and cast into 10 mm diameter molds. All groups were placed in 100% humidity at 37°C and tested with a Gilmore-type metric indenter at multiple intervals starting at 30 minutes. The time from the end of mixing to the lack of visible indentation was recorded as the setting time. A one-way ANOVA and post-hoc Tukey test were used to analyze the data. Longer milling time significantly reduced the particle sizes from 5.39µm to 1.89µm, and the setting time was proportionately reduced with a decrease in particle size (p <.05). The preliminary data from this experiment indicates that as the particle sizes for BioRoot® bioceramic sealer decrease, the setting time also appears to decrease.