Abstract : The purpose of this study was to compare the NiTi rotary files and hand files concerning the lateral and outside canal transportations after instrumentation of the curved canal. Ten dentists instrumented 100 plastic blocks with either NiTi or stainless steel hand files up to #35. Methylene blue liquid was injected into the canal before and after preparation, and digital photographs were taken. The maximum lengths of the lateral and outside transportation were measured on composite images and analyzed by Student’s t-test. In the preparation with NiTi files, the working time was about one third compared with the hand files. The elbow, apical transportation and the step formation were especially seen with hand files. Transportations of NiTi files were smaller than those of hand files. The outside of the curvature was cut down at the cervical side from the elbow, and the inside was cut at the apical foramen side. When the apical foramen was turned below and it was observed from the apical foramen, the right side wall of the apical root canal was cut more than the left side. These results suggest that NiTi files prepared root canals rapidly with less lateral and outside transportation than hand files.

Abstract : This case report describes the treatment of the lingual canal (MB2) in mesio-buccal roots of maxillary molar teeth with the dental microscope by referring to sectional images obtained by the limited cone-beam CT. Dentin removal during the canal detection procedure could be done safely under magnification because the operator had understood the presence and location of MB2 beforehand. Images obtained by the cone-beam CT were useful for canal detection under the dental microscope.

Abstract : This study was designed to examine the efficacies of the combination of EDTA and NaOCl, or ultrasonics with or without EDTA on smear layer removal from root canal. The effects of different working times of EDTA and NaOCl (1 or 2 min. for EDTA, and 0.5, 1 or 2 min. for NaOCl, i. e. six combinations) were evaluated in four segments in the canal : at orifice, middle third, and 3 mm or 1 mm from apical foramen (apical 3 mm or apical 1 mm, respectively). Combined irrigation of EDTA and NaOCl showed time-dependent effects. The treatment of 2-min. EDTA and 2-min. NaOCl was most effective in all combinations. However, its efficacy was somewhat lower at apical 3-1 mm, while the smear layer of the orifice to center was effectively removed. Ultrasonic irrigation without movement revealed that when it was used with water, only the smear layer in the segment contacted by the tip was removed, but partially, while using with EDTA it worked effectively throughout the whole canal. Taken together, totally ultrasonic irrigation with EDTA tended to be superior at the apical 3-1 mm to the combination of 2 min. EDTA and 2 min. NaOCl. Further studies of irrigation methods with syringes or ultrasonic irrigation time with EDTA and its concentration are needed.

Abstract : The objective of this study was to investigate the effect on antimicrobial activity of the addition of chlorhexidine to a glass-ionomer cement (GIC) sealer. Chlorhexidine gluconate was added to an experimental GIC sealer at concentrations ranging from 0% to 5% by weight. At 1 h setting time the specimens were placed onto agar plates inoculated with Enterococcus faecalis (E. faecalis) or Porphyromonas gingivalis (P. gingivalis), and the zone of inhibition was measured after 24 h incubation. The samples using E. faecalis and P. gingivalis strains caused significant bacterial growth inhibition at concentrations of 0.5% and 0.1%, respectively. These results suggest that the addition of chlorhexidine to a GIC sealer results in a significant reduction in microorganisms when compared with GIC alone, and the antibacterial effect depends on the concentration of chlorhexidine added.

Abstract : Hypochlorous acid is a weak acid with the chemical formula HClO. It forms when chlorine dissolves in water. HClO is an acid involving a polyatomic ion. HClO is used as a bleach, oxidizer, deodorant, and disinfectant. Campher^TM contains 80% HClO and is used as a food disinfectant, deodorant, air cleaner, and in instrument and package cleaner systems. The purpose of this study was to examine the efficacy of Campher^TM as a root canal irrigant in endodontics. Both pH 6.5 and pH 7.0 Campher^TM were examined for bactericidal effect and cytotoxicity. Obligative anaerobic bacteria were completely inhibited by applying Campher^TM for 1 minute, and facultative bacteria was inhibited 10⁻²～10⁻³ by Campher^TM for 1 minute in bactericidal effect. The growth of oral epithelial cells was not affected by Campher^TM for 48 hours. Both bactericidal effect and cytotoxicity did not vary with the different pH of Campher^TM. These results suggested that Campher^TM has a bactericidal effect and no cytotoxicity, and could be useful as a root canal irrigant.

Abstract : The purpose of this study was to evaluate the microleakage and bond strength at the interface between resin-based core materials and resin-based sealers. Materials tested were Resilon (a polyester-based material, R), FlexPoint Neo (a polypropylene-based material, F) and gutta-percha points (G) as cores, and Epiphany (a dual curable composite resin sealer, EP), Superbond sealer (a 4-META MMA/TBB resin sealer, SB), Sealapex (S) and Canals N (C) as sealers. Specimens were prepared by inserting a point in a layer of unset sealer in a plastic mould. For microleakage evaluation, the specimens were immersed in 1% methylene blue for 7 days and dye penetration was scored. For the evaluation of bond strength, a pulling load was applied to the specimens via a universal testing machine (crosshead speed 1 mm/min) and loads at failure were measured. The results demonstrated that the EP/R and SB/G groups showed significantly less leakage than the SB/F group (p<0.005). The EP/R and SB/R groups expressed significantly greater bond strength than the EP/G, SB/G and C/G groups (p<0.05). These findings suggest that sealing/bonding quality at the sealer-core interface may be improved when certain combinations of resin-based root canal filling materials are used instead of conventional materials.

Abstract : The purpose of this study was to establish a reliable method to observe the healing process of the periapical lesion after endodontic surgery. Using a collimating device, geometrically standardized radiographs of a periapical lesion were taken. The density of radiographs was digitized by means of an image scanner. A copper foil step wedge was used for film density standardization. Quantitative information of periapical bone density was expressed in copper equivalent value.

 A clinical application of this technique indicated that it is a reliable way to assess changes of bone density following the healing or destructing process after endodontic surgery.

Abstract : Researchers have suggested that deficiencies in parathyroid hormone (PTH) and calcitonin promote osteoclastic bone resorption and the development of periapical lesions. In the present study we have investigated the effects of PTH and calcitonin on periapical bone destruction in rats without parathyroid and in rats that had neither a parathyroid nor thyroid. Of the 90 seven-week-old female Wistar rats studied, we gave 40 a parathyroidectomy (P-ect) and gave another 40 both a parathyroidectomy and thyroidectomy (T&P-ect).Ten rats were kept as a control group. We administered PTH as replacement therapy to half of the rats in the P-ect group, and we administered both PTH and calcitonin (on alternate days) as replacement therapy to half of the rats in the T&P-ect group. Therapy continued until the end of the experiment. At 11 weeks, we exposed pulp to the oral cavity for from 1 to 3 weeks to induce experimental periapical lesions in all test animals. We measured the bone-loss area to quantify the extent of periapical bone destruction and the number of osteoclasts and inflammatory cells in the periapical lesions. Mean values of periapical-bone destruction and the number of osteoclasts increased for both P-ect and T&P-ect groups. At 3 weeks, the bone loss of the rats that had received replacement therapy (either PTH or PTH and calcitonin) was not observably different than that of rats that had received no replacement therapy. Our result shows that PTH and calcitonin regulate periapical bone destruction.

Abstract : Apical stop loss is often found in cases of root resorption, apical perforation, and immature teeth. Prevention of the extrusion of obturation material and periapical healing are difficult in such case. The purpose of this study was to evaluate the non-surgical apical barrier technique clinically in the use of mineral trioxide aggregate (MTA) as an apical barrier. An apical barrier of white MTA and the thermo-plasticized obturation technique were applied to apical stop loss cases and examined under the microscope and subsequent follow-up examination. The MTA was placed into the affected canals using a MTA carrier, where it was introduced 5 mm short of the radiographic apex and condensed in the apical third by gentle packing with an endodontic plugger. At the 3 to 12-month follow-up, apical stop loss cases were asymptomatic, and the periapical radiolucent lesion area showed partial healing. These results suggested that the MTA apical barrier technique may be up-regulated during the development of hard tissue formation and periapical healing.

Abstract : Even though FC fixation, iodine calcium, and calcium hydroxide applications are usually used for direct pulp capping and the root canal filling of primary teeth, the prognosis may not necessarily be success. In this study, Mineral Trioxide Aggregate (MTA) which has the capability for dentin mineralization was used as a direct pulp capping material to dog tooth pulp.

 The present author et al. performed a component analysis of MTA powder using a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDS). The substitution mineralization is possible by making the MTA contribute to the substitution of the mineral in a mineralization process by the non-collagen framework suggested.

 After six weeks and eight weeks, we compared MTA to a mixture of calcium hydroxide/Ca (OH) ₂ with 2% Xylocaine as dog tooth pulp medicament for pulp capping in animal testing. The stricture (the mineralization of union formation) mechanism of the cavity of tooth by MTA is cement-like conduction ability. Furthermore, we previously reported that, although hyperaemia was partially observed in the healing of pulp tissue lacking in mineralization contribution cells, we obtained good histological results without inflammatory influence and the change of the apical area tapetum.

 We performed pulp capping using MTA in the clinical treatment of the acute pulpitis dental condition of human primary teeth based on these studies this time. It is supposed that more or less normal tooth pulp regeneration can occur with the use of MTA in direct pulp capping. Moreover, it continued until the absorption of the primary tooth and external eruption.

 It is supposed that

 1. MTA is a component that does not cause any tissue injury to tooth pulp.

 2. MTA is an effective dentin and cement-like mineralization framework conduction material.

 3. MTA does not affect the apical area, and is a material that does not affect the tooth germ of odontclasts and their permanent successor there by contributing to root resorption of normal primary teeth.

 4. There is a slight possibility that MTA may be absorbed when primary teeth roots are absorbed.

 These results suggest that MTA controlled vital reactions, and that it is useful in the direct pulp capping of primary teeth.

Abstract : A study was performed to compare the apical closure efficacy of FR-Ca with that of Canals^® in the maxillary four canine teeth of two crab-eating adult monkeys. These teeth had necrotic pulps with periapical radiolucent areas. Each tooth in a monkey had an incompletely formed root with everted canal. External fistulae were seen on the face caused by the two pulpal lesions. Four root canals of these teeth were instrumented and filled during the same session with FR-Ca or Canals^® sealers. In the teeth filled with Canals^®, PTC was placed, and in teeth filled with FR-Ca, FR liquid was dressed.

 In incompletely formed roots, the right canine tooth was filled with lateral condensation of gutta percha cones and Canals^®. The left canine tooth was filled with FR-Ca sealer. In FR-Ca filling, gutta-percha cones were placed about 2 mm short of the apex. In completely formed roots, the left canine tooth was filled by using the former lateral condensation method. In the right canine tooth, FR-Ca sealer was placed to occupy about 1-2 mm of the apical canal space. The cavities were lined with zinc phosphate cement and then sealed with amalgam. The animals were sacrificed 9 months later. After decalcification, serial celloidin sections 15 μm thick were prepared in a buccolingual plane and stained with hematoxylin-eosin.

 Although FR-Ca sealer extruded apically, there were no apparent long-term adverse effects. Apical calcific tissues were observed microscopically. Radiographically, apical healing also progressed with time. In Canals^® to open apex, fibrous cicatrization of periapical tissue was observed and apexification did not occur. In FR-Ca to open apex, periapical closure occurred as a result of what appeared to be inward bending of root sheath, and a calcific bridge was continuous with the cementum of the undisturbed root apex. Loose connective tissue, abundance of fibroblasts, and some macrophage-like cells and multinucleated giant cells were apparent in the periapical periodontium. Inflammation was almost never seen. In a canal of completely formed root with Canals^®, chronic abscess was found with epithelial proliferation, bacterial masses and bacteria invaded dentin chips in the apical lesion. Areas of bone and root resorption were more frequent and apical repairs were not seen in the tooth.