Abstract : LL37 is the last 37 amino acid at the C-terminus of 18 kDa cationic antimicrobial protein and shows antimicrobial activity against bacteria, fungi and viruses. Elimination of bacteria, inhibition of inflammation and promotion of pulp cell function are necessary for regeneration of pulp-dentin complex in the treatment of pulpitis. In addition to antimicrobial activity, LL37 may influence the expression of cytokines in pulp cells. To prove this hypothesis, we examined the effect of LL37 on the gene expression of the inflammatory cytokines, interleukin (IL)-6 and IL-8, in human pulp cells (HP cells).

 HP cells were obtained from explant cultures of pulps taken from healthy teeth extracted for orthodontic reasons. HP cells were pretreated with synthesized LL37 (10 μg/mL) or BzATP (100 μM), an agonist of P2X₇ receptor, for 30 min. Subsequently, the HP cells were exposed to peptidoglycan (PGN derived from Staphylococcus aureus, 10 μg/mL) for 6 hours. mRNA levels of IL-6 and IL-8 were examined by real-time PCR. The expression of P2X₇ receptor was observed by immunofluorescence microscopy.

 HP cells expressed P2X₇ receptor. LL37 as well as BzATP suppressed the increase in IL-6 and IL-8 mRNA levels in HP cells stimulated by PGN.

 These findings suggest that LL37 inhibits cytokine mRNA expressions through P2X₇ receptor in HP cells. LL37 may participate in the regeneration of pulp-dentin complex by regulating inflammation and possessing antimicrobial activity.

Abstract : This article reports a new clinical method for the removal of broken instruments in root canals using a combination of endoscope and Er:YAG laser device. This technique is based on two stages under endoscopic observation : laser irradiation for minimal elimination of dentin around the fragments, and hand instrumentation with a long K-file for loosening and retrieval of the separated instruments. This method offers the advantage of conserving the remaining dentin wall of the root canal.

Abstract : The temperature of the applicator needle of the ObturaⅡ was measured using a thermocouple. For precise measurement, a very thin thermocouple (0.15 mm in diameter) that had low latency and heat capacity was used. The temperature setting of the ObturaⅡ was 200°C. The output of the thermocouple was connected to a digital recorder and later analyzed.

 The temperature at the needle connection was 140°C when its trigger was not activated, and 170°C when the trigger was activated. The temperature at the 25-gauge needle tip was 100°C when its trigger was not activated, and 120°C when the trigger was activated. When air was blown at the needle, the temperature of the needle tip considerably decreased.

 It is suggested that the following be performed to facilitate root canal filling using the ObturaⅡ :

 1. Just before the gutta-percha injection, the gutta-percha remaining in the needle should be discarded.

 2. Before filling, the canal should be dried and only a small quantity of sealer should be left in the canal.

 3. Air blow or air suction near the applicator needle should be avoided when injecting the canal.

 4. A thicker needle should be used if possible.

Abstract : To develop the safest irrigation technique, we measured the pressure generated outside the apical foramen during root canal irrigation. This pressure may increase when a large quantity of irrigation solution extrudes from the apical foramen.

 A pressure sensor was connected via a plastic tube to a root canal model made of glass. The root canal was irrigated while changing the tip position of the irrigation needle, the needle size, and the needle shape. A high pressure was recorded when the needle tip was bound to the root canal wall or extruded from the apical foramen. A negligible pressure was recorded when a Clean-washing needle was used.

 The results suggested the following :

 1. Irrigation solution should be placed in the canal with minimum pressure rather than be injected.

 2. The tip of the irrigation needle should not be extruded from the apical foramen and should not be bound to the root canal wall.

 3. Irrigation with a Clean-washing needle is one of the safest ways.

Abstract : For safe irrigation of the root canal, Fukumoto et al. developed the intracanal aspiration technique (IAT), although its clinical use was difficult because the tip of the aspiration needle was not thin enough. Since a novel thin aspiration needle has been developed, we evaluated its efficacy and safety in IAT.

 First, the aspiration capacity of the new needle was compared with older ones : the aspiration capacity of the new needle was very high.

 During IAT, the periapical pressure was recorded using a pressure sensor in a root canal model made of glass. The recorded pressure was approximately −1 kPa during usual IAT. A small positive pressure (5 kPa) was recorded only when the plunger of the irrigation syringe was strongly pressed.

 During IAT, the extrusion of the irrigation solution was recorded with a video camera. A negligible extrusion was observed in usual IAT. When the plunger of the syringe was strongly pressed, 3-4 mm extrusion of the solution from the aspiration needle tip was observed.

Abstract : Traumatic dental injuries usually result in crown infraction, crown fracture, root fracture, luxation, and other problems. The high incidence of injuries to the permanent teeth of young people is the result of their collective activities throughout their school years.

 A 14-year-old boy suffered luxation of his maxillary right central incisor in a sports accident. He was referred to our clinic one hour after the injury. The patient had kept the luxated tooth in his oral vestibule. The tooth was placed into the socket, and it was splinted temporarily. Root canal therapy was performed ten months later. At one year, there was no radiographic evidence of ankylosis in the luxated or subluxated tooth after root canal filling.

 An 11-year-old girl suffered luxation of her maxillary right central incisor in a bicycle accident. She was referred to our clinic one hour after the injury. The luxated tooth had been stored under a dry condition prior to her arrival. The tooth was placed into its respective socket and splinted to the adjacent teeth. Root canal therapy was performed six months later. Radiographic examination showed slight root resorption with clinical complications at 24, 30 and 39 months after the injury, respectively.

 Our results suggest that a luxated tooth should quickly be stored in an appropriate medium until the patient can arrive at the dental office for proper replantation.

Abstract : This article reports 3 cases of molar tooth with a vertical incomplete fracture. The cases were a vital mandibular left first molar without dental treatment history, a non-vital maxillary left second molar without dental treatment history, and a non-vital mandibular left second molar with gold class Ⅰ inlay. For each case, the fractured tooth was prepared and covered with a temporary resin crown immediately after the fracture was detected. All teeth were restored with a gold crown after the endodontic treatment for the two non-vital cases. Careful observation is necessary for these cases because of the poor prognosis of incomplete fractured teeth.