Abstract : Recently, the use of electrolyzed water has become widespread in a variety of fields. Although electrolyzed water have antimicrobial effects, they cause little harm to human being or the environment. We investigated antimicrobial effects of various electrolyzed water when used for root canal irrigation.

 The irrigants examined were two kinds of strong acid electrolyzed waters (SAW A and B), weak acid electrolyzed water (WAW), neutral electrolyzed water (NW), alkaline electrolyzed water (AW), 3%NaOCl and sterilized distilled water (DW). The root canals of extracted human teeth and artificial canals (epoxy resin) that had a working length of 10 mm and a size of #70 were used. Enterococcus faecalis was injected into the canal and then irrigated with 1, 3, 6, and 12 ml of each irrigant. After irrigation, the paper points used for sampling were incubated in tryptic soy broth at 37°C for 48 hours, and assessed for antimicrobial effects.

 All samples irrigated with NaOCl were negative growth (−). All DW samples were positive growth (+). For SAW, WAW and NW, some antimicrobial effects were seen on the artificial canals. However, there was a little effect on the extracted teeth. Antimicrobial effects of AW were not shown in artificial canal and extracted teeth.

Abstract : The purpose of this study was to evaluate the cutting ability of root canal orifices and walls as well as the exposure of root canal entrances by a Er : YAG laser beam. For this study, 42 human extracted teeth and the prototype Er : YAG laser device were used. The laser parameter was fixed at 8 Hz and 250^mJ/_pulse. The exposure time of a laser beam was 60 seconds in a single root case and 120 seconds in multiple root cases. Keeping the laser tip of holotube type on the root canal orifices, the laser irradiation was carried by the non-contact method. The evaluation of this research was done by the examination of X-ray pictures as well as the LM and SEM pictures. The results were as follows :

 The root canal orifices and walls of all specimens could be clearly exposed at the parameter of 8 Hz and 250^mJ/_pulse for 60 seconds and 120 seconds laser irradiation. In the cases of the curved root canals, the possibility of the perforation of the root canal wall was observed radiographically. So, it was mentioned that it was necessary to decrease the irradiation time or power in the curved root canals. The root canal surface lased by a Er : YAG laser beam showed the smooth surface with a LM and the scale-like structure with a SEM. Of course, there were little debrisses on the root canal surface. In some cases, the zip formation on the root canal wall close to the orifices could be observed with the radiographic examination.

Abstract : When the resected surface is examined after apicoectomy, openings of dentinal tubules, lateral canals and minute cracks are observed other than the smear layer. The failure of apicoectomy or the recurrence may be due to the method of surgery or the operator. However, the condition of resected surface may be one of the causes of unsatisfactory result of the operation. In order to examine the influence of the exposed dentin after apicoectomy, the dye penetration test and scanning electron microscopic observation were conducted to the resected surface.

 Seventy-five extracted human upper central incisors were kept in physiological saline solution. After the crowns were removed, the apex of each tooth was resected by 3 mm using a diamond slice disk through running water. Of the 75 teeth, 50 were vertical sectioned and 50 samples were obtained. They were divided into five groups as each group has 10 teeth. Group 1 : Resected surface was treated by 10% phosphoric acid solution for 30 seconds. Group 2 : The surface was treated with self-etching primer followed by application of resin adhesives (Cliarfil Liner Bond-2, Kuraray Japan) and then coated with a light-activated low viscosity composite resin (Protect Liner-F, Kuraray). Group 3 : Nd : YAG laser was applied to the surface. Group 4 : The surface was treated by 10% phosphoric acid solution and then Nd : YAG laser was applied. Group 5 : The surface was not treated. Dye penetration test was conducted to all samples of five groups. The remaining 25 teeth were divided into five groups and were also treated by the same manner employed in the 5 groups. Then the resected surfaces were observed by scanning electron microscope.

 The result shows that the samples in Group 2 and 4 have significantly low degree of dye penetration. The smear layer covered the resected surface of all the test samples before the surface treatment. The smear layer was removed after the treatment using 10% phosphoric acid solution, the application of self-etching primer and laser irradiation. Opened dentinal tubules were coated with the low-viscosity resin or sealed by the application of laser after removing smear layer.

 It is suggested from this study that the application of composite resin coating or laser irradiation after removing the smear layer were capable to seal the opened dentinal tubules on the resected surface, which might cause the dead space or connect the root canal to apical periodontal tissue.

Abstract : The present study was carried out to investigate histologically and histometrically the effect of experimental unilateral traumatic occlusion on periapical tissue after pulpectomy in rats.

 Sixty rats were divided into 4 groups. The animals in Group A received no treatment as a control. The animals in Group B received pulpectomy of the left mandibular first molar, those in Group C, a resin plate was cemented onto the occlusal surface of the left maxillary molars, and those in Group D, pulpectomy of the left mandibular first molar and a resin plate installed of the left maxillary molars. All animals were killed at 1, 3 and 7 days after treatment, and the periapical periodontal ligament and the interradicular furcation of the left mandibular first molar were examined histologically. Moreover, the area of the periapical periodontal ligament was measured histometrically.

 In the periodontal ligament at 7 days, no changes were found in Group A. In Group B, infiltrates of inflammatory cells and an increased amount of fibrous connective tissue were seen. In Group C, compression of the periodontal ligament was noted. In Group D, inflammation equal to that in Group B and undermining resorption were found.

 The area of the periapical periodontal ligament in Group C was significantly smaller (p<0.01) than that in Group A at 7 days.

 The results of the present study suggest that traumatic occlusion may delay the recovery of the periapical lesion in experimental animals.

Abstract : Anaerobic, Gram-negative, black-pigmented rods (BPRs) have been thought to be one of putative periodontic and endodontic pathogenes.

 Recently, one of BPRs, Prevotella intemedia, was reclassified into P. intermedia and P. nigrescens. Many investigators have determined the occurence of these bacteria in periodontal diseases using new classification, however, there is only few reports to estimate the occurence of them in apical periodontitis.

 The purpose of this study was to investigate the occurrence of P. intermedia and P. nigrescens in apical periodontitis including the teeth which have been done partial pulp treatments and the teeth without any pulp treatments. Subjects in this study were 8 teeth diagnosed as apical periodontitis. After removing their filling of the teeth, endodontic entry was done using rubber dam, and infected apical dentin was taken by H-file. The tip of file was cut by sterilized cutter, put into 1 ml of GAM broth and performed serial 10-fold dilutions with GAM broth. One hundred μl aliquot of each dilution was put on Brucella HK agar supplemented with 5% sheep blood, hemine and menadion and cultivated in Anaero Box under an atmosphere of 80% N₂, 10% CO₂ and 5% H₂ for 7 days. All BPRs were isolated and classified into Genus Porphyromonas and Prevotella with performing Rapid ID 32 A system, fluorescence under long-wave of ultra violet (360 nm), trypsin-like enzyme activity, α-glucocidase activity. Furthermore, Genus Prevotella identified into P. intermedia and P. nigrescens using the difference of migration pattern of glutamate dehydrogenase and malate dehydrogenase.

 In the teeth which have been done partial pulp treatments, facultative anaerobic bacteria were predominant while anaerobic bacteria were predominant in the teeth without any endodontic treatments. BPRs predominated among the isolates from the teeth which showed big radiolucent images at the apical lesions.

 P. nigrescens was seldom isolated although P. intemedia was the most predominant species among the identified BPRs.

Abstract : Root canal irrigants, smear layer removal agents and/or fluorides were applied to the smear layers that were produced after filing of human root canal walls’. Permeability was studied by the dye penetration test. Surface structure of root canal dentin was examined by scanning electron microscope (SEM).

 The following results were obtained :

 1) In root canal irrigants, NaClO was ineffective to remove the smear layer, however, Tubulicid Plus, EDTA and EDTA-NaClO-H₂O₂ were effective to remove smear layer on the SEM observation. All irrigants except Tubulicid Plus enhanced dye penetration.

 2) In smear layer removal agents, Dentin Conditioner, Tubulicid Blue and Tubulicid Red were ineffective to remove the smear layer on the SEM observation. Tubulicid Blue enhanced dye penetration, however, Dentin Conditioner and Tubulicid Red reduced it.

 3) Application of SnF₂ or Dentin Conditioner with SnF₂ to the smear layer did not remove it. Dentin Conditioner with SnF₂ was most effective to reduce dye penetration, however, dye penetration was not reduced by SnF₂.

 Therefore, considering the three dimensional obturation after root canal preparation, irrigation of EDTA-NaClO-H₂O₂ is useful for clinical procedure. On the other hand, Dentin Conditioner with SnF₂ is useful for dentin-chips filling method.

Abstract : In the endodontic therapy of the pulpless permanent tooth with a wide-open blunderbuss apex, apexification is useful treatment for apical closure. In this case report, treatment of apical periodontitis via resin restration of central tubercle of lower left second premolar was done to adult. The tooth has been prepared on the occlusal surface and restored with resin filling about 10 years ago. Since then, patient has been always suffered from discomfort and fistula on the patient tooth. On the x-ray film, large periapical lesion was observed. After removal of composite resin, no caries was observed in the cavity, but a small hole was observed on the cavity floor. The pulp was none vital so root canal treatment was done and filled with calcium hydroxide successively. When apexification was completed and periapical lesion disappeared after five months, root canal filling with vertical condensation of gutta perch was done. After one year from root canal filling, patient has no problem on the lower left second premolar.

Abstract : To confirm the safety of the HY-c cement, including tannin agent, in use as a root canal sealer, we showed in a previous report that the experiment in vitro, which indicate the safety in tissue culture.

 But some unknown points of the reaction of a living body in the state of the direct contact to that still remained. Therefore, the experiment in vivo of this time was performed.

 At first, the HY-c cement was directly implanted into the muscle of Balb mice.

 Then, the mice were sacrificed after 2 or 5 weeks, and the tissue reactions were examined with a microscope. It showed that any inflammation on the tissue was not observed. That result indicated that the safety of this agent was confirmed also in vivo.

 We expect that this tannin agent will play a great role in saving teeth.