Abstract : Purpose : The aim of this study was to compare the canal shaping properties of XP-endo Shaper (FKG, Switzerland) which was formed into a helical shape by thermal technology (MaxWire alloy) and NEX file (GC, Japan), which is a conventional constant taper nickel-titanium instrument in the oval-shaped tooth replica model by using micro-computed tomography (micro-CT) scanning.

 Methods : A total of 20 oval-shaped mandibular premolar tooth same replica models were provided by two groups (XP-endo group : 10 ; NEX group : 10) and scanned preoperatively and postoperatively by micro-CT scanning. Canals were prepared with a new XP-endo Shaper which was formed into a helical shape and new NEX files as a conventional constant-taper nickel-titanium file under sterilized water irrigation. The volume of treated canal and the amount of the untreated area were measured. The data was analyzed using Student’s t-test.

 Results : Instrumentation of canals increased their volume and surface area. The XP-endo group had a significantly higher proportion of treated volume and prepared surfaces than the NEX group (p<0.01).

 Conclusion : Preparations with the XP-endo group had a greater volume of treated canal and smaller untreated area than the NEX group in oval-shaped mandibular premolar tooth replica models.

Abstract : The purpose of this study was to investigate the root canal morphology of extracted second mandibular molars determined as single root.

 Sixty-nine single rooted mandibular second molars were used. Gutta-percha point was inserted into the root canal after root canal preparation by a standardized method. Transparent specimens were made from the test teeth and the root canal morphology was evaluated on images taken with a digital microscope.

 A C-shaped canal was found in 28.9%. When the root canal was prepared in accordance with the root canal orifice observed in the pulp chamber floor, a missed canal was found in 42% of the teeth. Missed canals could not be discovered due to branching inside the root.

Abstract : An apical foramen is sometimes unavoidably made too wide after mechanical root canal enlargement in order to eliminate bacteria. A wide foramen may lead to unsuccessful root canal filling. In a 60-year-old female patient, dental radiography and cone beam computed tomography revealed a large periapical lesion and external resorption of the maxillary right second premolar. This case was diagnosed as chronic apical periodontitis with external root resorption, and so infected root canal treatment was performed. The buccal root canal needed enlargement to the size of #80 to remove infected dentin. Obturation of the root canal by the conventional root canal filling with gutta-percha points was difficult. On the other hand, the palatal root had a clinically closed root canal at the apical area. Long-term use of calcium hydroxide was applied to encourage the closure of the widely-formed apical foramen with deposition of hard tissue. As a result, apical barrier formation at the apical area was observed under a microscope. Root canal filling was carried out by mineral trioxide aggregate. The CAD/CAM crown was set on the tooth. At 2-year clinical and radiographic follow-up, the affected region had almost completely healed.