Endodontic Clinical Outcome after Separated Instrument Removal Using a Spinal Needle Technique: A Retrospective Study of Thirty Years of Clinical Experience

Introduction Current methods for the removal of separated endodontic instruments (RSI) are not predictable. Methodology The primary outcome of this retrospective study was to assess the clinical and radiographic success (CRS) of teeth in case of RSI after a 5-year follow-up. Secondary outcomes were to evaluate: (1) the effectiveness in RSI; (2) the risk of root fracture after RSI. The study protocol was registered at ClinicalTrials.gov (ID: NCT05128266). The patients were treated by the same endodontist between January 1991 and December 2019. The RSI was performed under the operative microscope as follows: first, the dentine surrounding the coronal part of the broken instrument was selective removed by using a small ultrasonic tip to loosen the fragment; then, a modified spinal needle was used to catch and remove the instrument. The 1-, 3-, 5-, and >5–year CRS were recorded. Logistic regression analysis was performed to determine independent predictors of failure (i.e., tooth number, type of root canal, shape of the root canal, type of broken instrument, apico-coronal level of the separated instrument, presence of periapical lesions, root perforations). Results A total of 158 teeth were included in this study. Finally, 131 instruments underwent RSI (82.9%). RSI was an independent predictor of CRS after 1-year of treatment (OR: 58.3; 95% CI 27.42–95.73, p < 0.05). At the 5 years follow-up, only 10/131 teeth (7.6%) failed. All failures were caused by root fracture (10/10) (χ2 test, p < 0.05). Separated instruments located in the apical third of the root were more difficult to remove (13/49 cases, 26.5% - χ2 test, p < 0.05). Conclusions The proposed technique: • can achieve excellent effectiveness in RSI, • can achieve a high CRS rate, also when a periapical lesion is present, • is not associated to a significant increase in root fracture incidence, • should be performed with the help of an operative microscope.