Abstract : The purpose of this study was to evaluate the physical properties and antimicrobial effect of newly-developed paste-type root canal sealers (zinc oxide eugenol and non zinc oxide eugenol) filled in dual syringes and to compare the results with conventional powder-liquid sealers (Canals^® and Canals-N^®).

 The physical properties of the sealers, namely flow behavior, working time, hardening time, film thickness, shrinkage and solubility, were examined following ISO 6876 and 3107 standards for root canal sealers. The antimicrobial effect was evaluated for 10 oral microorganisms.

 As a result, paste-type sealers of both ZOE and N-ZOE showed physical properties equal to conventional Canals^® and Canals-N^®. Paste-type ZOE sealers produced strong inhibition in P. gingivalis, P. endodontalis and V. parvula. These findings suggest that newly-developed paste-type sealers have adequate physical properties equal to those of conventional powder-liquid sealers and the hardening time of the two types suitable for each case can be chosen in clinical use.

Abstract : The purpose of the present study was to examine the cause and treatment of periodontitis and periodontal abscess with normal pulp on immature permanent teeth after traumatic injuries. Four patients with 5 traumatized young permanent teeth were assessed clinically and radiographically. The ages of the children ranged between 8 to 10 years old at their initial visits.

 1. In the teeth with horizontal root fractures, repositioning and rigid fixation were successful treatments to keep the pulp vital and to repair the periodontal tissue.

 2. In a replanted avulsion tooth with necrotic alveolar bone fragments, removal of fragments enabled the periodontal tissue to recover.

 3. In a tooth with incomplete crown-root fracture, the pulp and periodontal ligaments survived soundly after preparation and filling with bonding resin for the surgically exposed fracture lines.

 Bacteria could invade the periodontal tissue via gingival lacerations of horizontal root fractures, necrotic marginal bone fragments, and incomplete crown-root fractures. For the early detection of periodontitis after traumatic injuries, appropriate periodontal probing around the tooth such as the mobility test, electric pulp test, and radiographic examination is required.

Abstract : In this study, we made gray Portland cement and white Portland cement samples with a composition blend of Bi 20% and gypsum 5% with a weight ratio of 75% of each gray and white Portland cement. Four samples of commercial gray PROROOT MTA^®, gray Portland cement, white PROROOT MTA^® and white Portland cement were observed morphologically with a scanning electron microscope (SEM) and the trace element components were analyzed by energy dispersive X-ray spectroscopy (EDS). We investigated the possibility of endodontic application from these constituent elements and oxidation compound ratio.

 The four samples included CaO and SiO₂ which were mineralization constituents, and the total molar ratios of these oxidation compounds were gray PROROOT MTA^® : 83.77%, gray Portland cement : 79.64%, white PROROOT MTA^® : 80.58% and white Portland cement : 83.51%. Mineralization promoting materials included MgO, Al₂O₃ and SO₃, and Bi₂O₃ of the contrast media. Fe was not included in the white PROROOT MTA^® and white Portland cement, and the oxidation compound molar ratio of Fe₂O₃ was gray PROROOT MTA^® : 0.53% and gray Portland cement : 2.59%.

 From these results, although there were some differences in the weight ratio and atomic weight ratio of trace elements among these four samples, it is suggested that they had similar main components except Fe. However, it is necessary to investigate the trace elements of compounds as a whole, because SEM-EDS analysis was only possible from the sample surface to a depth of several μm.

Abstract : In Japan, the thermoplastic root canal obturation method, in which obturation-gutta soft (OGS) is heated to about 44°C and injected into the intracanal and which was developed by Otani et al. in 1978, offers superior operability and sealing ability. The author has modified the thermoplasticized method by injecting OGS to a shaped and dried intracanal, and performing diffusion and compression with an Ni-Ti condenser, and obturates the apical foramen so as not to form a dead space by the twin pluggers technique. This modified technique has shown superior clinical results for 28 years. After root canal obturation of 6⌋ by this technique, six years passed as super-structure is not attached without visiting to hospital. We had an opportunity to extract a tooth because the bifurcation caries of 6⌋ cannot be restored. We obtained informed consent from the patient and made an epoxy imbedding sample, and we confirmed the excision direction by microCT. We then investigated the obturating ability and long-term dentin mineralization change of each apical area using SEM and SEM-EDS analysis.

 The results showed that the mesiobuccal root of 6⌋ had a dead space of about 1,360 μm, but there was no interposition of granulation tissue and the central part of the dead space had a narrow segment due to a protrusion (width 292.1 μm, height 127.6 μm). The width was 162.2 μm, which was similar to the physiological apical foramen. As for the composition, both protrusions consisted of Ca : P : Na : Mg : Cl with an average weight ratio (%) of 48.73 : 34.82 : 8.19 : 4.03 : 4.49 by SEM-EDS analysis, and the ratio of Ca/P was 1.40. It is judged that the reparative dentin was formed by such composition elements. In the distobuccal apical area and palatal apical area, mineralization of each apical foramen was observed. It was considered that reparative dentin and cementum had formed.

 Regarding the obturating ability of the apical area, because it did not remove the smear layer in this case of cleaning, a smear layer of average thickness of 3.15 μm existed between the canal wall and OGS. However, in the portion, the OGS adapted directly to the canal wall without interposition of the smear layer and showed superior obturating ability.

 However, as for the OGS, it is thought that the component of OGS is replaced by hard tissue as substitution materials because absorption image was observed in the entire apical area and no Zn existed in the OGS of the absorption process. These results suggest that in an infected root canal caused by endodontic lesion, filling by thermoplasticized obturation of OGS to the apical foramen is required.

Abstract : We report a highly successful apicoectomy aided by a dental microscope after a dental CT examination, and that the dental CT resulted in high diagnostic ability and excellent therapeutic effect.

 The patient was a healthy 35-year-old female. The dental CT radiography revealed the presence of a perforation located 3 mm from the apical portion of the labial root canal of the left maxillary lateral incisor and overextension of the root canal filling material. As it would have been difficult to treat the tooth by conventional methods, apicoectomy and retrograde filling were performed under a dental microscope.

 The dental CT used in the present study detected the presence of a perforation on the root canal surface and overextension of the filling material at the apical portion that could not be seen by conventional radiography. The use of a dental microscope is very effective for allowing accurate apicoectomy and retrograde filling that cannot be achieved by conventional methods. The use of both the dental CT and dental microscope might usher in a new era for better examination, diagnosis and therapies in endodontics.

Abstract : Avulsion of permanent teeth is the most serious of all dental injuries, and replantation is the treatment of choice. However, if the tooth pulp has necrotized, complications such as inflammatory resorption may occur.

 A 10-year-old boy suffered avulsion of his maxillary right and left central incisors due to falling down. The avulsed teeth were replanted immediately and were splinted. Root canal treatment of the maxillary right central incisor was performed 1 month later. At follow-up 6 months later, radiographic observation revealed inflammatory resorption and periapical radiolucency in the maxillary left incisor, so infected root canal treatment was performed. Calcium hydroxide was placed into the root canal, and was changed every month. Root canal filling was performed 6 months later. At 1, 8 and 41 months follow-up, clinical and radiographic examinations showed that the tooth was firm and remained asymptomatic. The results for this case suggest that inflammatory resorption can be prevented depending on the timing of endodontic treatment in replanted teeth.

Abstract : When there are two canals present in a mandibular premolar, they may bifurcate anywhere along the root. Cleaning, shaping, and filling of the tooth can be problematic because of the difficulty of accessing the bifurcating canals. Therefore, proper knowledge of canal morphology, careful interpretation of the radiograph, and tactile sense are major requirements for successful treatment.

 This case report describes three cases of mandibular first and second premolars with bifurcating canals which were successfully treated endodontically. In these cases, diagnosis was based on radiographic and clinical examinations using endodontic files. In a radiographic examination, as the root appears to have one large canal, radiographic images should be taken to locate any additional canals. An examination of the canal wall to probe for a catch which may indicate the orifice of an additional canal was performed using an endodontic file. It is suggested that in the case of the mandibular premolar tooth, clinicians should carry out a careful radiographic examination to ensure that any multiple canals are detected. Moreover, the combined use of a surgical microscope and an ultrasonic tip is useful to find another canal whose orifice is deeper than the original canal orifice.

Abstract : Removal of Thermafil carriers can be a challenge during root canal retreatment. This study compared the time required for removing Thermafil Plus plastic carriers using different NiTi rotary instruments. Sixty simulated root canals with a 30-degree curvature in resin blocks were instrumented to size 25/06 (using K3) or 25/08 (using ProTaper) and filled with size 25 Thermafil Plus obturators. Plastic carriers were removed using one of the following instruments : ProTaper D1, K3 (25/10, 25/06 and 25/04), Peeso reamer (size 1) and Gates Glidden drill (size 1). The time required to remove the plastic carrier was recorded. Carriers were successfully removed in all of the canals where NiTi instruments were used, whereas all the carriers were severed when Peeso reamers or Gates Glidden drills were used. ProTaper D1 and K3 25/10 instruments required significantly shorter time compared with K3 25/06 and 25/04 instruments. The difference of canal taper did not influence the removal time. No file separation occurred. It was concluded that, under the present experimental conditions, the use of NiTi rotary files with an active cutting tip and/or greater taper facilitated the removal of Thermafil Plus plastic carriers.

Abstract : For a good clinical course after either a pulpectomy or infected root canal treatment, it is important to fill the root canal up to the physiological apical foramen. However, we sometimes encounter clinical cases in which insufficient root canal filling has no radiolucent area at the apex on X-ray photos and yet the clinical course is good. In this study, we evaluated the relationship between the condition of root canal filling and the state of root apex on X-ray photos in order to identify ideal methods of root canal filling.

 2,000 single-root teeth with root canal filling on dental X-ray photos were randomly selected and the condition of root canal filling and the existence of a radiolucent area at the root apex on X-ray photos were evaluated. The teeth were classified into three groups : “under-filling”, “fair-filling” and “over-filling”. Under-filling of 2-3 mm showed the lowest prevalence (p<0.001, Chi square-test). In 85.7% of teeth without an apical radiolucent area in “Under-filling”, the unfilled area of root canals was unclear in X-ray photos.

 These findings suggest that not only the condition of root canal filling but also the state, such as bacterial resistance, of the root canal during root canal filling strongly influences the prognosis of root canal treatment.

Abstract : Without appropriate treatment, infection spreads from root canal to bone and a periapical lesion forms. Therefore, appropriate systemic administration and local application of antibiotics is necessary depending on the state of infection. This report describes a case of chronic apical periodontitis with large periapical lesion that was treated non-surgically by systemic administration and local application of antibiotics based on a susceptibility test.

 The patient was a 31-year-old woman. X-ray images of the affected tooth, the maxillary right second molar, showed a large periapical lesion. After routine root canal treatment, the exudates from the periapical lesion were subjected to bacterial examination with the anaerobic culture system and antibiotics susceptibility test. Based on the results, levofloxacin hydrate was systemically administered for three days, and cefaclom and ciprofloxacin were locally applied into the root canals. After the treatment, all clinical symptoms and anaerobic cultivable bacteria disappeared and so the root canals were filled. The prognosis was good 18 months after the root canal filling. This case suggests that non-surgical treatment with systemic administration of adequate antibiotics based on the antibiotics susceptibility test may be effective for large periapical lesions, for which surgical treatment is usually the first choice.