Abstract
BACKGROUND: This study used micro-computed tomography (µCT) to assess the post space preparation systems [Rebilda (VOCO), RelyX (3M)] and preparations of varying lengths to create root dentin cracks. METHODS: Forty extracted maxillary first premolars with two roots were randomly divided into four groups. Teeth were decoronated to a length of 18 mm. Following root canal treatment, first µCT scans were performed. Post spaces were prepared with Rebilda post drills at 1/2 of the working length (WL) in Group 1 and at 2/3 of the WL in Group 2, while post spaces were prepared with RelyX post drills at 1/2 of the WL in Group 3 and at 2/3 of the WL in Group 4. After post space preparation, second µCT scans were performed. Dentinal cracks were detected by comparing the first and second µCT scan images, which were classified as "newly formed cracks", "advanced cracks" and "completed cracks". The chi-square test was used to compare among the groups, with a p-value of < 0.05 considered statistically significant. RESULTS: No statistically significant differences were observed between the groups for completed and advanced cracks (P > 0.05). In terms of newly formed cracks, the Rebilda-2/3 group showed more cracks than the RelyX-1/2 group, and the RelyX-2/3 group had more cracks than the RelyX-1/2 group (P < 0.05). CONCLUSION: Completed and advanced cracks were observed in all groups, while no newly formed cracks were detected in the RelyX-1/2 group. The type of post drill and the preparation length are crucial factors in preventing the development of root dentinal cracks. Preparing 1/2 of the canal length may be a safer preparation length, and the RelyX drill may pose less risk of inducing root dentinal cracks.