Abstract : An apical observation method for the root canal for recording the apical root canal with high image quality was developed. Apical observation at approximately 200 magnification was possible by attaching a hi-vision digital video camera to a dental microscope. The method was used to produce clinical images of apical granulation tissue. The apical granulation tissue was suggested to affect the electric measurement of root canal length.

Abstract : The purpose of this study was to evaluate the effect of treatment with Hypochlorous-acid Electrolyzed Water and three kinds of root canal irrigant (NaOCl, EDTA and MTAD) on the bond strength of 4-META/MMA-TBB resin to dentin. Bovine dentin surfaces of maxillary anterior teeth were ground with 600-grit silicon carbide abrasive paper under water coolant for 30 seconds to make them plane-parallel and then were irrigated with various root canal irrigants for 10 minutes.

 4-META/MMA-TBB resin was bonded to prepolymerized resin cores accorded to the manufacturers’ instructions. After storage in distilled water at 37°C for 24 h, specimens were stressed at a crosshead speed of 1 mm/min. The interfacial adhesion was observed under SEM of various samples.

 In the results of the shear test, the group treated with sodium hypochlorite showed significantly decreased bond strength compared with the control group. On the other hand, the HEW, MTAD and EDTA treated groups showed no significant differences in bond strength value. Observations of the resin—dentin interfaces using SEM showed a morphological difference in HEW and each of their comparison groups. In the NaOCl, MTAD and EDTA groups, crevices between resin and dentin were observed, whereas crevices were not found in the HEW and control groups.

 From these results, it is suggested that HEW did not affect the 4-META/MMA-TBB resin bond strength.

Abstract : The aim of this study was to evaluate the efficiency of laser-activated irrigation (LAI) in cleaning accessory root canals. Simulated root canal models with accessory canals were used. Accessory canals of 0.5 mm diameter were located at 1, 3, 5, 10 mm from the apex. Accessory canals were filled with the flowable radiolucent material, CalcipexⅡ^®. Root canals were irrigated with Er:YAG laser-activated irrigation (LAI) or syringe irrigation. Three groups (n=4) were evaluated as follows : Group 1 : LAI with a cone-shaped tip for 20 s at 30 mJ and 20 pps, stationary method ; Group 2 : LAI with a cone-shaped tip at 30 mJ and 20 pps, pull-up method (1 mm/s) ; Group 3 : syringe irrigation with 3 mL water. Digital X-ray photographs using microtomography were analyzed for the quantity of radiolucent material remaining after irrigation. Overall comparison (average of the material-removed area from all four accessory canals) between irrigation methods was performed using the Tukey-Kramer test. Differences between the four accessory canals after each irrigation method were also investigated. Statistically significant differences (p<0.01) were found between the LAI and syringe irrigation groups. LAI was more effective in cleaning the accessory root canals than syringe irrigation. The effect of LAI in the upper accessory canal was lower than that in the other accessory canals. Especially, the stationary method showed this tendency more remarkably than the pull-up method. These results suggest that LAI irrigation using Er:YAG laser equipped with a cone-shaped tip may be promising in cleaning accessory root canals.

Abstract : Mineral Trioxide Aggregate (MTA) possesses a high sealing ability and a good hard tissue inducing capacity, and has been regarded as an ideal material for perforation repair. Here, we report a case of perforation repair with MTA after removal of a huge radicular cyst (13 mm diameter) presumably caused by perforation of a metal post. MTA was filled from the root canal after removing the radicular cyst, but some amount of MTA was pushed out to the extra root canal space. Following the removal of overhanging MTA after its complete hardening, the periodontal pocket was improved from 6 mm to 3 mm during 30 days. Good bone formation and periapical tissue healing were achieved during long-term three-year follow-up, however, a slight surface defect of MTA concomitant with deeper depth of periodontal pockets was detected at 3 years. The defect of MTA may have been caused by its exposure to the periodontal pockets. It is suggested that MTA effectively induces alveolar bone formation and periodontal tissue repair for root canal perforation accompanied with large bone defects. However, dissolution of MTA may induce loss of periodontal attachment and the formation of deep periodontal pockets.