Abstract Objectives : Dental patients sometimes complain of nociceptive chronic pain due to chronic inflammation in the dental pulp and periapical tissues. Neuropathic orofacial pain, including deafferentation pain, has also been reported. Tooth extraction and extirpation of the tooth pulp may fall under the category of deafferentation. The purpose of this study was to analyze factors associated with well-localized, nociceptive and/or neuropathic orofacial chronic pain associated with endodontic treatment (ECP).

 Methods : We analyzed the ECP-associated factors in 129 teeth of 58 patients with a complaint of well-localized ECP. They were endodontically treated in the Endodontic Clinic, in cooperation with the Orofacial Pain Clinic or Ambulatory Anesthesia Service of the Dental Hospital, Tokyo Medical and Dental University.

 Results : Diversity of ECP was observed. We could reduce and remove nociceptive ECP by the conventional endodontic treatment in most cases. However, neuropathic or nociceptive ECP related to endodontic accidents, retreatment or long-term infection was sometimes persistent after the endodontic procedure.

 Conclusions : Endodontic treatment can help eliminate nociceptive causes of ECP and relieve ECP. However, care must be taken not to instigate ECP by thoughtless endodontic treatment or extraction of multiple teeth. Lack of a correct diagnosis or treatment plan could be one of the main causes of severe ECP.

Abstract Objective : The purpose of this study was to examine the influence of operator experience on the quality of K-file hand instrumentation and nickel-titanium (Ni-Ti) file instrumentation in root canal preparation using a dental simulator.

 Materials and Methods : A total of 18 extracted human maxillary first premolars were selected and mounted to a manikin dental simulator. Operators having clinical experience of 1 or over 5 years were selected and each of them performed root canal preparation using K-files and Ni-Ti files (FKG Race). The working time of each root canal preparation was recorded, and a root canal surface of each sample was also observed with a scanning electron microscope.

 Results : When using K-files, the average working time and root canal surfaces prepared by operators with over 5 years of experience were better than those with only 1 year of experience. On the other hand, without relation to experience, averages of the working time and root canal surfaces prepared using Ni-Ti files were better than those prepared using K-files. There were no differences of the working time and root canal surfaces prepared using Ni-Ti files between the two groups.

 Conclusion : The systematic root canal preparation using Ni-Ti files resulted in relatively good performance without relation to experience under clinical simulation.

Abstract : The purpose of this study was to investigate the antibacterial effects of Er:YAG laser on experimentally infected bovine root canals in vitro. After the pulp tissue was removed, samples were inoculated with a suspension of Enterococcus faecalis for 5 days, and subsequently irradiated by an Er:YAG laser equipped with a cone-shaped tip (core diameter : 400 μm) at a power of 50 mJ. The disinfecting efficacy was evaluated using scanning electron, light, and fluorescence microscopies. Bacteria stained with Gram staining were seen in the dentinal tubules at the mean depth of 500 μm after incubation for 5 days. Scanning electron microscopic investigation revealed that the bacterial layer of the inner dentin surface had been eliminated. On the other hand, some bacterial colonies were seen immediately adjacent to the lased surface. However, live and dead staining showed that bacteria seemed to be dead at least 100 μm from the inner dentin surface. These results suggest that the Er:YAG laser has bactericidal effects not only on the ablated dentin surface, but also on the deeper dentin layer.

Abstract : In this study, we used calcium hydroxide for temporary root canal filling and prevented exudation from periapical abscesses. Here, we present two cases of the healing effect of a temporary root canal filling.

 The patients were an 11-year-old girl and a 23-year-old woman, who had a radiolucent lesion of chronic periodontitis of the lower first molar and lower second incisor, respectively. Each tooth had a fistula, and showed draining not only from the fistula but also into the root canal. Root canals were enlarged by the step-back technique and irrigated by 5% NaClO and Östby-EDTA. The effect of cleaning the root canal wall was evaluated by microscope. After the mechanical and chemical cleaning of the root canal were finished, calcium hydroxide paste (Vitapex^®) was temporarily filled into the root canal, even though the periapical lesion showed draining into the root canal but no acute symptoms such as pain. Consequently, it seems that a temporary root canal filling prevents an immunogen, exudation into the root canal from a periapical abscess, and finally helps the healing of a periapical abscess wound due to chronic apical periodontitis.