Retreatment of Two Bioceramic Sealers Included Two Different Percentages of Calcium Silicate Using Two Endodontic File Systems: An In Vitro Study

Calcium silicate materials are widely used in endodontic treatment. Different calcium silicate percentages can be included in bioceramic sealers. The aim of this <i>in vitro</i> study was to investigate the effect of the calcium silicate percentages on mineral deposition into dentinal tubules at 7 days, 1 month, and 4 months of aging, as well as the effect of calcium silicate percentages on the quality of retreatment using two endodontic retreatment systems.Single rooted premolars were used in the present study. After the shaping and irrigation steps, the obturation was performed using high (Ceraseal "CRS") and low (AH Plus Bioceramic "AHB") calcium silicate percentage sealers. ReTreaty (RT) and ProTaper Universal Retreatment (PUR) were used to perform the retreatment process. The time required to achieve the apex was recorded. A digital microscope and a cone-beam computed tomography (CBCT) were used to evaluate the remaining materials after the retreatment procedure. Scanning electron microscope was used to investigate the presence of mineral deposition into dentinal tubules and the change in mineral morphology at 7 days, 1 month, and 4 months. The data was statistically analyzed using two-way analysis of variance and <i>t</i>-test.Both materials (CRS and AHB) demonstrated different mineral depositions onto their surfaces after 24 hours, 1 month, and 4 months, and showed mineral depositions into dentinal tubules at 4 months. RT was faster in achieving the apex for CRS group compared to PUR (<i>p</i> < 0.001), while no difference was found between both systems among the AHB groups. Both retreatment systems were quicker to achieve the apex in AHB compared to the CRS group (RT <i>p</i> = 0.035 and PUR <i>p</i> < 0.001). CBCT demonstrated a more precise measurement compared to the digital microscope in which the instrument and the material factors influence the removal ability at the coronal and middle thirds (<i>p</i> < 0.05). No significant difference was found at the apical third.The retreatment of AHB was easier and faster than CRS. RT demonstrated higher removal ability and faster time compared to PUR. The apical third proved to be a difficult area to achieve an optimal cleaning. Calcium silicate percentages included in bioceramic sealers could play an important role in root canal retreatment. Higher percentages of calcium silicate can decrease the capacity of the retreatment process and increase the needed time to remove the materials.