(PR54) Root Dentin Thickness Following Ultrasonic Retro-preparation at Resection Levels 3mm, 6mm, and 9mm in Endodontic Microsurgery

Abstract:

Introduction: With retro-preparations we should be concerned with the amount of root dentin thickness remaining as the depth of the preparation increases. More than a 10% decrease in root dentin thickness(RDT) could increase the likelihood of vertical root fracture. In microsurgery when preparing beyond 3mm, are we removing too much dentin when we increase our preparation length?

Purpose: To investigate if 3, 6, 9mm ultrasonic retro-preparation will result in a 10% decrease in RDT at the resection level and at corresponding preparation depths. We hypothesized that there would be >10% loss in RDT as we increased the length of the retro-preparation from 3mm to 6mm to 9mm. Materials &

Methods: 32 single-canal anterior teeth were root canal treated, resected 3 mm from the apex, scanned using CBCT, and were retro-prepared at resection level using 3, 6, 9mm tips. CBCT scans were taken after each longer tip was used. Measurements from the axial views of CBCT scans were used to calculate the decrease in RDT both at the resection level before and after different tips used and at the corresponding depth of each tip. Statistical significance was set at p<0.05.

Results: Retro-preparation resulted in a statistically significant decrease(p < 0.0001) in RDT at resection level and at the 3 levels investigated.

Conclusion: Retro-preparation significantly decreases RDT after using 3, 6, 9mm tips at resection level and at corresponding depths of these tips making the teeth more susceptible to fracture. Care should be taken to avoid weakening these teeth during retro-preparation procedures.