Retrograde Instrumentation of Surgically Resected Roots Using Controlled Memory Files: A Human Cadaver Study.

Abstract Introduction The purpose of this study is to evaluate the amount of residual obturation material of retroinstrumented surgically resected roots using controlled memory (CM) files and to evaluate the incidence of adverse treatment outcomes. Methods Thirty maxillary anterior teeth in human cadavers were selected and non-surgical root canal treatment was performed on these teeth. A standardized 4-mm osteotomy and a 3-mm root resection with as close to a zero-degree bevel as possible was made on each tooth. A microsurgical diamond tip was used to create a 1-2 mm starting point for each retropreparation. A 25/06 and 30/06 VTaper 2H (SS White, Lakewood, NJ) were bent at a about 90-degree angle to mimic the clinical and anatomical restrictions and used to create a retropreparation to a depth of 14-mm. Micro-CT scans were taken and analyzed for volume and percentage of residual obturation material at 5- and 10-mm. Additionally, the incidence of instrument separation and crack and ledge formation in the teeth were recorded. Results The median volume of residual obturation at 5- and 10-mm was 0.18 mm3 (interquartile range of 0.36 mm3), and 1.97 mm3 (interquartile range of 1.99 mm3) respectively. The overall incidence of file separation during retropreparation was 13.33% (4/30). Among the cases analyzed with micro-CT, none showed crack or ledge formation. Conclusions Retroinstrumentation of surgically resected roots using controlled memory files cleans the canal effectively with relatively low adverse treatment outcomes. This novel technique, while limited in application, is a safe and effective way to achieve a deep, clean retropreparation.