Irradiation of gallium-aluminum-arsenide (GaAlAs) semiconductor laser to rat molars is known to induce the formation of mineralized tissue in the pulp chamber. The purpose of this study was to analyze mRNA expression levels of selected non-collagenous proteins in GaAlAs laser-irradiated rat molars by means of reverse transcription-polymerase chain reaction (RT-PCR). The mesial surface of the upper right first molar of 8-week-old Wistar rats was irradiated by a pulsed GaAlAs semiconductor laser (Lightsurge 3000, Osada) at an output power of 1.5W for 60 seconds, 3 times. The first molars of unirradiated 8-wk-old rats were used as the control. After 1, 3 and 7 days, the first molars were extracted, and total RNAs were isolated from the coronal pulp. Then, expression levels of mRNAs for osteopontin, osteonectin, osteocalcin, dentin sialophosphoprotein, dentin matrix protein 1, and bone sialoprotein were analyzed by means of RT-PCR. The pulp reaction was examined histologically. mRNA expression levels of all the proteins were upregulated by 3 days, and the upregulation was maintained at 7 days. Histological observation revealed localized tissue necrosis in the mesial portion of the irradiated pulp at 1 and 3 days, whereas rearrangement of odontoblast-like cells and a small amount of newly formed calcified matrix were recognized at 7 days. In conclusion, it was demonstrated that GaAlAs laser irradiation to rat molars caused upregulation of mRNAs for non-collagenous proteins prior to the appearance of newly-generated mineralized tissue-forming cells.

View full abstract

The purpose of this study was to analyze the uptake of fluoride (F), calcium (Ca) and phosphorus (P) by dentin from a newly developed resin-modifier glass-ionomer liner for dentin hypersensitivity treatment (Clinpro™ XT varnish; Clinpro). A standardized box-form cavity (3mm in width and 1.5mm in depth) was prepared in the buccal cervical area of 20 intact human premolars and was filled with Clinpro. The specimens were immersed in distilled water at 37℃ for 1, 7, 30 and 90 days (n=5, each), and then sectioned longitudinally in a bucco-lingual direction through the center of the cavity. Elemental compositional analysis and elemental mapping of the material-dentin interfacial layer was carried out by wavelength-dispersive X-ray spectroscopy electron-probe microanalysis. Set Clinpro specimens without water immersion and dentin specimens without Clinpro filling served as controls. After 90 days of water immersion, relative density of F, Ca and P increased in dentin but decreased in Clinpro along the Clinpro-dentin interface (5-20μm apart from the interface). An increase of Ca/P ratio in the interfacial dentin was also detected. Elemental mapping revealed a layer of high F concentration in the interfacial dentin, and its width gradually increased with longer immersion time. These results demonstrate that Clinpro has the capacity to release F, Ca and P and suggest that this capacity may contribute to the control of dentin hypersensitivity and provide a cariostatic effect on this material.

View full abstract

Recently, single-step self-etching adhesives have been introduced to clinics. Researches on single-step self-etching adhesive systems have revealed that the adhesives have good bonding performance under in vitro as well as in vivo conditions. However, some concerns about degradation of the resin-tooth interface remain because the adhesive contains water which releases hydrogen ions. The Adper™ Easy Bond self-etch adhesive has been developed to solve these problems, but there is little information on its clinical performance. The purpose of this study was to investigate the short-term clinical performance of this single-step self-etch adhesive. A total of 41 restorations were placed with Adper™ Easy Bond in combination with resin composite Filtek™ Supreme DL. All restorations were evaluated using the modified USPHS criteria immediately after placement (baseline), and at 1-week, 3-month, and 6-month recalls. The results were as follows: 1. Pulpal responses, restoration failures, post-operative sensitivity and secondary caries were not detected in any of the cases during the observation period. 2. At the 6-month recall, 41 restorations were rated as Alpha for color match, anatomical form, surface roughness and marginal staining. 3. From the evaluation of marginal adaptation, only one restoration revealed a marginal gap formation detected by using explorer.

View full abstract

The aim of this study was to investigate the percentage of various dental procedures in the total treatment time spent by the general dental practitioners at the Department of Dentistry, Toranomon Hospital. The dental treatments were classified into 14 categories: examination at the first appointment, periodontics, endodontics, resin composite restoration, inlay/onlay restoration, re-set, crown, bridge, denture, implant, oral surgery, temporo-mandibular joint dysfunction, bleaching, and others. These 14 categories were further classified into a total of 50 subitems. Eleven dentists measured the time taken to complete each procedure with a stopwatch while they treated their patients. After the 3-month investigation period, the total number of patients, and the total and average treatment time for the 50 items, were calculated. Furthermore, the Point/Time ratio (P/T ratio) was calculated to compare the rate of insurance fee to the average treatment time. The treatment time was 29,556min (28.7%) in periodontics, 9,274min (9.0%) in endodontics, and 16,083min (15.6%) in operative dentistry. The treatments in conservative dentistry (periodontics, endodontics, and operative dentistry) accounted for 53.3% of the total treatment time. The treatment time in descending order was scaling (21,677min, 21.0%), resin composite restoration (13,019min, 12.6%), examination at the first appointment (9,312min, 9.0%), periodontal disease treatment (4,276min, 4.1%), partial denture/full denture adjustment (3,938min, 3.8%), crown non-vital preparation of tooth crown+impression taking+bite taking+temporary crown (3,930min, 3.8%), and root canal treatment (3,725min, 3.6%). The time for scaling and resin composite restoration was the first- and second-largest among the various dental procedures. The dental procedures with the highest P/T ratio were hard resin bridge set (218.8), full denture set (171.6), and night guard set (170.1), and those with the lowest P/T ratio were crown metal core cavity preparation+impression taking (1.3), bridge metal core cavity preparation+impression taking (two abutments: 1.6), hard resin bridge trial (1.8), and root canal treatment (single root canal: 1.9). The P/T ratio is thought to be an index of the cost performance of the various dental procedures.

View full abstract

The Society for Endodontic Education aims to create an appropriate dental training system for the future. As the first step, we conducted a questionnaire survey on the instruments, materials and medicines used for endodontic practice in Japanese dental schools. The subjects were 29 endodontic departments responsible for education on endodontology and endodontics at dental schools across Japan. The response rate to the questionnaire was 100%. The results showed that there were differences not only among schools but also between the clinic and practice even in the same school. It is believed that the causes of differences among schools are different from those within one school. The causes of the differences among schools are believed to be that some endodontic procedures are not standardized nationwide, and that there are various contents of education among schools. On the other hand, the causes of the variations between the clinic and practice are the different criteria for selecting instruments, materials and medicines. While clinics tend to select advanced instruments, materials and medicines, in practice they need to follow the Outline of Dental Education, Model Core Curriculum for Dental Education, OSCE, and questions on the national dentist examination. Therefore, it is believed that there is a time lag in the selection of instruments, materials and medicines between clinic and practice. A comprehensive analysis is needed in order to decide whether these differences are to be eliminated or not. We need to examine the link between this difference and the educational effect in order to improve practice education.

View full abstract

Although adhesive resinous sealers for root canals have mainly been investigated by push-out bond testing, the microtensile bond strengths (μTBS) of these sealers to radicular dentin have not been systematically studied. To evaluate the bonding properties of four representative adhesive resinous sealers, the μTBS to radicular dentin was measured, debonded surfaces were analyzed by video-microscope, and the sealer-dentin interface was observed by SEM. Extracted single-rooted human teeth were used. After enlarging the root canal, the pulp chamber was irrigated with root canal irrigant and dried with paper points. Roots were then filled with Super-Bond RC-Sealer (Sun Medical), Epiphany® (Pentron, USA), Epiphany® SE™ (Pentron), or MetaSEAL™ (Parkell, USA) where an acrylic was point inserted. All specimens were kept moist at 37℃ for 2 weeks. The specimens were then ground into halves parallel to the long axis of the tooth to expose the point space, and sliced into 0.7mm thick sections. Slices were trimmed to create dumbbell-shaped specimens with a cross-sectional area at the bonding interface of 1.0mm², and μTBS was measured at a cross-head speed of 1.0mm/min. The interface between the sealer and radicular dentin was observed by SEM, and the failure mode was examined by video-microscope. The results were as follows: 1. The μTBS of RC-Sealer and MetaSEAL™ was significantly higher than that of Epiphany® or Epiphany® SE™. 2. Microscopic evaluation of the failure mode indicated that failures in RC-Sealer and MetaSEAL™ were cohesive within the sealer itself, whereas in Epiphany® and Epiphany® SE™ failures were mostly interfacial. 3. In SEM observations of RC-Sealer and MetaSEAL™, gaps were not observed in any of the interfaces and the formation of resin tags and a hybrid layer was observed. In Epiphany® or Epiphany® SE™, resin tags were formed in part of the sealer-dentin interface. However, the hybrid layer was not observed in any of the radicular dentin walls, and gaps were occasionally observed.

View full abstract