Abstract : Tri-Auto ZX2＋ was introduced for endodontic therapy. According to the manufacturer, this Endo motor can be used for apical patency and glide path preparation.

 Purpose : The aim of this study was to determine the possibility of apical patency and to compare the times for obtaining apical patency and the glide path preparation times in constricted canals with periapical lesions using OGP2 in Tri-Auto ZX2＋ and hand files.

 Methods : Eighty-five roots needing root canal treatment were included. In Group 1 (N＝40) hand files were used ; in Group 2 (N＝45) OGP2 with NiTi files were used. Group 1 had 14 roots and Group 2 had 39 roots for which apical patency was to be obtained. The time from negotiation to apical patency was measured with an electronic stopwatch for the 53 roots. After the establishment of apical patency, glide path preparation times were recorded with an electronic stopwatch (Group 1 : 14 roots, Group 2 : 39 roots). The data were analyzed using the t-test and chi-square test (p＜0.05).

 Results : Group 2 had a higher rate of obtaining apical patency than Group 1. There was a statistically significant difference in the mean glide path preparation times and the time to obtain apical patency between Group 1 and Group 2 (p＜0.05).

 Conclusion : Under the limitations of this study, OGP resulted in a statistically higher possibility of establishing apical patency than hand files. OGP resulted in statistically faster glide path preparation times and the time to obtain apical patency than hand files.

Abstract : Purpose : The aim of this study was to confirm the changes after contact between walking bleach agent and hardened white mineral trioxide aggregate (WMTA).

 Materials and Methods : WMTA discs were formed by a mixture of WMTA powder and distilled water (DW). The discs were immersed in a mixture of sodium perborate tetrahydrate (SPT) and 30% hydrogen peroxide (H₂O₂) (SPT＋H₂O₂), SPT and DW (SPT＋DW), and 30% H₂O₂ alone. Portland cement (PC) discs were formed by a mixture of PC powder and DW. PC discs and bismuth oxide powder were also contacted with 30% H₂O₂. Their changes in condition and temperature were confirmed by a digital video camera and an infrared thermography camera, respectively. The elemental distribution of the surface of WMTA discs contacted with 30% H₂O₂ and DW was analyzed by energy dispersive X-ray spectroscopy.

 Results and Discussion : Many bubbles were observed when WMTA discs were contacted with SPT＋H₂O₂ and 30% H₂O₂, however few bubbles were identified when they were contacted with SPT＋DW, suggesting that contact between H₂O₂ and WMTA is the main cause of bubble formation. PC discs contacted with 30% H₂O₂ also induced the formation of many bubbles. WMTA discs and PC discs continued to induce bubble formation for 180 min. Many bubbles were also formed when bismuth oxide powder was contacted with 30% H₂O₂ and their formation was rapidly accelerated after around 2 min. WMTA discs, PC discs, and bismuth oxide powder contacted with 30% H₂O₂ increased in temperature in a time-dependent manner. WMTA discs contacted with 30% H₂O₂ showed a decrease in silicon elements compared with discs contacted with DW.

 Conclusion : 30% H₂O₂, which is contained in walking bleach agent, induces the formation of bubbles, an increase in temperature, and a loss of silicon elements from WMTA when they are contacted with hardened WMTA.

Abstract : Purpose : Conventionally, the structure of root apical ramification and the pathology of the root apex have been observed mainly by optical microscopy. This study aimed to clarify the structure of root apical ramification and the accumulation of bacteria and leukocytes by using X-ray micro-computed tomography (micro X-ray CT) and scanning electron microscopy (SEM), which have become widely used in recent years.

 Materials and Methods : The maxillary left second premolar of an 83-year-old male was used for observation. Observations were made by micro X-ray CT and SEM after tooth extraction.

 Results and Discussion : Micro X-ray CT revealed four ramifications at the apex of the buccal root. At least seven ramifications were observed at the apex of the palatal root, and 12 cavities were observed in the horizontal-section image. SEM observation revealed the presence of bacteria and leukocytes slightly inside the opening of the apical ramification.

 Conclusion : The maxillary second premolar has many apical ramifications, and once infected, it is considered difficult to treat. As root-canal cleaning of this tooth is physically difficult, it is necessary to combine chemical methods to achieve cleaning. If healing is difficult, surgical treatment should be considered.