Instrument separation is a critical complication during root canal therapy, impacting treatment success and long-term tooth preservation. The etiology of instrument separation is multifactorial, involving the intricate anatomy of the root canal system, instrument-related factors, and instrumentation techniques. Instrument separation can hinder thorough cleaning, shaping, and obturation of the root canal, posing challenges to successful treatment outcomes. Although retrieval of separated instrument is often feasible, it carries risks including perforation, excessive removal of tooth structure and root fractures. Effective management of separated instruments requires a comprehensive understanding of the contributing factors, meticulous preoperative assessment, and precise evaluation of the retrieval difficulty. The application of appropriate retrieval techniques is essential to minimize complications and optimize clinical outcomes. The current manuscript provides a framework for understanding the causes, risk factors, and clinical management principles of instrument separation. By integrating effective strategies, endodontists can enhance decision-making, improve endodontic treatment success and ensure the preservation of natural dentition.
Humans ; Root Canal Therapy/adverse effects* ; Consensus ; Root Canal Preparation/adverse effects*

Objective:To develop and validate an clinical prediction model for the risk of breast cancer-related lymphedema (BCRL).Methods:Breast cancer patients who were prepared to undergo axillary lymph node dissection were propsectively enrolled, indocyanine green combined with Photodynamic Eye (PDE) was applied to reveal the arm lymphatic flow . The arm lymphatic fluorescence images were collected to calculate the proportion of arm lymph flow above and below the axilla vein. Volumetric measurements of both arms and subjective questionnaire were performed to evaluate the occurrence of lymphedema. A difference in volume between the arms >10% was defined as lymphedema. Univariate logistic regression analysis was used to analyze the relationship between each factor and BCRL. The stepwise forward method was used to include multiple factors in the logistic regression analysis to establish the prediction model.Results:Three hundred and twelve patients were enrolled. Fourty-five (14.4%) patients developed BCRL. Using the coefficients obtained from multivariate analysis, BMI ( OR 95% CI: 1.34 (1.25-1.77), P<0.05), chemotherapy ( OR 95% CI: 2.26 (1.97-2.63), P<0.05), regional lymph node radiotherapy ( OR 95% CI: 1.59 (1.05-2.41), P<0.05) and the proportion of arm lymph flow above the level of the axillary vein ( OR 95% CI: 0.70 (0.68-0.81), P<0.05) were identified as independent predictive factors for BCRL, and the following prediction equation was derived: Y=0.369×(BMI at surgery)+0.713×(taxane-based chemotherapy)+0.862×(radiotherapy)-9.058×(proportion of the arm lymph above the axillary vein)-6.859 8. The ROC curve was screened to the optimal boundary value of 0.118 6 by the Youden's index. The sensitivity, specificity, positive predictive value and negative predictive value of prediction of this model were 93.3%, 79.4%, 73.3%, 98.6%, respectively. Conclusion:With the guidance of the predictive model, particular patients who need the preservation of axillary lymphatic system can be identified, and timely intervention can be carried out.