Root canal treatment is the main therapy of dental pulp diseases and periapical diseases. The success or failure of the treatment largely depends on the quality of root canal preparation. In root canal preparation, an access to the pulp cavity is created and continuous, smooth root canal is established. This process is the initial preparation of root canal and results in clean root canal. Accordingly, root canal instruments can smoothly enter the root canal and instrument fracture can thus be avoided. Special instruments are used to establish smooth canal when necessary. Preliminary preparation instruments for root canal with unique function and good forming capability can be developed rapidly. This paper provides constructive suggestions in treating dental pulp and periapical diseases.%根管治疗是牙髓病和根尖周病的主要治疗手段，而根管治疗成功与否很大程度上取决于根管预备的质量。在根管预备之前，首先要设计良好的髓腔入口并建立连续光滑的根管疏通通道，这个过程即为根管的初步预备。根管初步预备使清洁和成形根管的器械能够顺畅进入根管，可避免器械分离，为此专门用于建立根管光滑通道的器械应运而生。当下，根管初步预备器械凭借其独特的作用和良好的成形能力发展较为迅速，本文就根管初步预备器械的发展现状作一综述，旨在给牙髓病和根尖周病的治疗提供一些建设性的建议。
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机译：控制无人驾驶飞行器的人为因素问题：支持加拿大部队联合无人驾驶飞行器监视目标获取系统项目的初步调查结果（事故发生人：飞行员驾驶员飞行员预防飞行员：预备部队初步调查和预防飞行员联合会D'acquisition D'Objectif au moyen de Vehicules aeriens Telepilotes de surveillance des Forces Canadiennes）
