Abstract : The intracanal breakage of root canal instruments has been considered a big problem in endodontic treatment. To prevent the breakage, dentists should apply efficient root canal therapy in their treatment with knowledge of the characteristics of endodontic instruments.

 This article examines the historical perceptives of intracanal breakage, prevention and prognosis, and describes the method devised and used for seven years by the author for preventing intracanal breakage of root canal instruments.

 The preventive method is applicable for dentists under any clinical situation. The practical application of such a method during treatment will ensure good file conditions, allowing dentists to perform more efficient root canal therapy with less labor and strain.

Abstract : Many kinds of file systems and materials have been developed for root canal enlargement in recent years. Recently, various types of nickel titanium (Ni-Ti) file system have been developed. Initially, manual Ni-Ti instruments were developed and applied clinically, but their cutting efficiency was low, so many engine-driven file systems for easy enlargement have been developed. This study evaluated the shaping ability of K3^® (SybronEndo), a new rotary engine-driven Ni-Ti instrument.

 We compared the shaping ability between the K3^® and Quantec Series 2000^® SC (Analytic Endodontics Company) in terms of the shaping time and cutting efficiency for root canal enlargement. The Quantec 2000^® SC had a positive cutting edge as well as K3^®.

 The working time of the K3^® was faster than that of Quantec Series 2000^® SC to prepare the root canal of human mandibular incisors. The transportation of the root canal wall using the K3^® was significantly less than that of the Quantec Series 2000^® SC at the apical portion of simulated resin canals. Thus, the K3^® had many clinical advantages for root canal preparation.

Abstract : A 20-year-old woman fell from a bicycle, and struck her face. After confirming that no systemic abnormalities were present on a surgical hospital, she consulted our dental clinic 10 days after injury.

 Intra-oral findings showed extrusion in 11, and mobility in 112 was markedly high. The observation of X-ray showed the marked expansion of the periodontal ligament space in 112, particularly in the root apical area.

 After surgical reposition, the teeth were fixed using metal wires and acrylic resin, and the fixation was removed 4 weeks later. Since 1 caused pulpitis 3 months after, pulpectomy and root canal treatment were performed. At first 12 showed no pulp response, but pulp response appeared 7 months after.

 Findings after 10 and 20 years : Pulp response was noted in 12. No abnormal findings were detected in the periodontal tissue in 112. X-ray film showed no abnormal findings around the area of the apical area. X-ray film on 20 years showed that the root canal filling material extruded from the root apex of 1 disappeared.

 Findings after 27 years : Pulp response was present in 12. No abnormal findings were confirmed in the periodontal tissue in 112. X-ray showed no abnormal findings.