Purpose: Most dental treatments are performed at private dental clinics, while some of them are referred to secondary or tertiary dental care institutions. Although the number of missing teeth caused by fracture has been increasing recently, there are few reports on the present situation of tooth fracture in Japan. The purpose of this study was to identify the problems and demands of present dental practice by surveying patients with tooth fracture visiting the endodontic outpatient clinic of a university dental hospital.
 Methods: The subjects were new patients who visited the endodontic outpatient clinic of Tokyo Medical and Dental University for 22 days in June 2011. Their teeth and chief complaints were surveyed based on dental records and X-ray films after examination.
 Results: The number of patients was 462. Of these, the chief complaint of 118 patients (25.5%) was thought to be caused by tooth fracture. A fracture line was found in 44 (37.3%) of the 118; whereas tooth fracture was not found but was inferred from other findings in the other 74 patients (62.7%). Of the 462 patients, 134 (29.0%) consulted our hospital directly without consulting a private clinic and receiving a referral (①); 111 (24.0%) were referred from private clinics (②); 76 (16.5%) consulted our hospital without a referral even though they had been treated at a private dental clinic, as they wanted our hospital to treat or judge the validity of their treatment because the symptoms remained (③); 55 (11.9%) wanted our hospital to provide a second opinion about the validity of the diagnosis or treatment plan provided by a private clinic (④); 86 (18.6%) were referred from other outpatient clinics of our hospital (⑤). The number of tooth fracture cases of ① to ⑤ were 20 (14.9%), 25 (22.5%), 26 (34.2%), 25 (45.5%) and 21 (24.4%), respectively.
 Conclusions: This survey revealed the following regarding tooth fracture.
 1. There is a great demand for endodontic outpatient clinics. 2. It is necessary to educate general dentists about diagnostics. 3. Objective diagnostics at an early stage should be established. 4. It is necessary to inform patients that tooth fracture may require tooth extraction.

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 Purpose: By incorporating sodium fluoride in adhesive resin cement, the release of fluoride from the cement is expected to strengthen the teeth and prevent secondary caries. However, there is a concern that such fluoride incorporation and release could impair the physical properties of the cement. In this study, we investigated the influence of incorporating sodium fluoride on the flexural strength, water absorption and solubility of adhesive resin cement.
 Materials and Methods: The experimental resin cements were prepared at concentrations of 0-20 wt% sodium fluoride. The amounts of fluoride released from the cements were measured from day 1 to day 84. Next, a three-point bending test of the experimental resin cements was performed after initial curing (24 hours storage in water at 37°C) and after thermal cycle loading (5°C-55°C, 10,000 times). Furthermore, water absorption and solubility following 30 days immersion in water were measured.
 Results: Fluoride release increased with an increase in the content rate of sodium fluoride. After initial curing, the three-point bending strengths of 5 wt% and 10 wt% sodium fluoride compounded cement were not statistically decreased compared to those of sodium fluoride 0 wt%, but were significantly reduced by incorporation of more than 15 wt%. There were no significant differences in the strength between 15 wt% sodium fluoride compounded cement and 20 wt% sodium fluoride compounded cement. Similar results were also observed in the comparison of flexural strength after thermal cycle loading. Regarding the 30-day water absorption amount, there was no significant difference between 5 wt% sodium fluoride compounded cement and that of 0 wt% sodium fluoride cement. However, the 30-day water absorption of 10 wt% sodium fluoride compounded cement was significantly increased compared to that of 0 wt% sodium fluoride compounded cement. The solubility was not significantly different between the content rate of 0-10 wt% sodium fluoride.
 Conclusion: Increasing the sodium fluoride content improved the amount of fluoride release. On the other hand, the flexural strength of the cement was decreased, and the amounts of water absorption and solubility were increased. Within the limit of this study, it is suggested that 10 wt% sodium fluoride compounded cement could provide fluoride release without decreasing mechanical strength.

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 Purpose: The surface pre-reacted glass ionomer (S-PRG) filler is a bioactive material able to release various ions, and water-extract solutions of the S-PRG filler are known to form precipitates when mixed with phosphate-buffered saline (PBS) or artificial saliva (AS). This study focused on the precipitate formation, and investigated the dentinal tubule-occluding ability of S-PRG filler extract solutions on artificially demineralized bovine dentin.
 Methods: An S-PRG filler extract solution without filler particles (SF0), and an S-PRG filler slurry containing 50% of filler particles (SF50) were used as test materials. The test materials were mixed with either PBS or AS, and the elemental compositions of supernatants and precipitates were analyzed with inductively coupled plasma atomic emission spectroscopy and wavelength-dispersed electron probe microanalysis, respectively. Qualitative phase analysis of the precipitates was made with X-ray diffraction. To analyze the tubule-occluding ability, artificially-demineralized bovine dentin specimens were created by phosphoric acid etching (10%, 10 minutes) followed by polishing with a paste containing hydroxyapatite; treated with the S-PRG filler extract solutions followed by either PBS or AS; and observed with a scanning electron microscope.
 Results: Na, B, P, F, Sr, Si and Al were detected from the supernatant of the SF0-PBS mixture; Ca in addition to the 7 elements were detected from the supernatant of the SF0-AS mixture. The precipitate contained elements originating from the S-PRG filler extract solutions (Na, Sr, Si, Al, B and F) and PBS/AS (P, Na and Ca). X-ray diffraction revealed the presence of NaCl and Na₃H₂P₃O₁₀・1.5H₂O in the precipitates of the SF0-PBS and SF0-AS mixtures, respectively. Moreover, insoluble deposits were formed on the tubule openings and peritubular area of the artificial hypersensitive dentin specimens treated with SF0 or SF50 followed by PBS or AS. The deposit formation was most prominent on the SF50-treated followed by the AS-treated dentin specimens.
 Conclusion: The two-step application of S-PRG filler extract solutions followed by PBS or AS exhibited dentinal tubule-occluding ability on artificially-demineralized bovine dentin.

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 Purpose: We prepared an in vitro model of hypersensitive dentin, which had the same intrapulpal pressure as in humans and the wet condition inside the dentinal tubules closely resembled that in the clinical setting, and performed light-cured composite resin filling on it. We then examined the state of adhesion when the dentin was sealed with a light-cured composite resin for the treatment of dentin hypersensitivity.
 Methods: Human molar teeth were used for this experiment. For the experiment, pieces of coronal dentin were smoothed to a flat surface and their coronal sides were abraded with wet sandpaper until #600, in order to prepare dentin disks of 1 mm thickness. With dentin disks that would be subjected to pressure of 25 mmHg, the same as human intrapulpal pressure, the in vitro model of hypersensitive dentin was prepared. Then, adhesives of four types of one-bottle one-step bonding system (BeautiBond Multi (BB), G-BOND PLUS (GB), Scotchbond Universal Adhesive (SU) and CLEARFIL S³BOND ND Quick (TB) ) were applied. Meanwhile, the control group was prepared through the same procedure except that the dentin disks of 1 mm thickness were not put on the apparatus. After the adhesive was applied, they were preserved in water at 37°C for 24 hours or 6 months and then subjected to a tensile bond strength test, creating four groups: 24h control group, 24h hypersensitive group, 6M control group, and 6M hypersensitive group (n=7).
 Results: Concerning the specimens after 24-hour preservation, TB in the control group and SU and TB in the hypersensitive group showed significantly greater bond strength compared with other products. Concerning the specimens after 6-month preservation, in the control group no significant differences were observed among the products, whereas in the hypersensitive group SU showed significantly greater bond strength compared with BB. When the 24h control group, the 24h hypersensitive group, the 6M control group, and the 6M hypersensitive group were compared with each other in each of the products, no significant differences between the 24h control group and the 6M control group were observed except in TB.
 Conclusion: When dentin hypersensitivity is treated with adhesive resins, bonding systems that include an organophosphate monomer (MDP) are more effective. However, moisture from dentinal tubules may permeate and cause adhesion failure with the passage of time.

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 Purpose: Periodontitis is a chronic gingival inflammatory disease caused by periodontopathic bacteria. Alveolar bone resorption is induced by inflammatory responses to bacterial infection. In our previous studies, we demonstrated that T cells are associated with LPS-induced inflammatory bone resorption. On the other hand, traumatic occlusion is regarded as an aggravating factor in periodontitis. Excessive occlusal force is involved in a large part of alveolar bone destruction. Previously, we established a rat occlusal trauma model showing bone loss in the furcation area in response to occlusal overload. Furthermore, in that study, we reported that bone resorption was accelerated by injection of LPS around the furcation area. However, it is unclear whether T cells are involved in bone resorption in response to traumatic occlusion. In the present study, in order to evaluate the involvement of T cells in bone resorption in response to traumatic occlusion, we histologically examined osteoclast formation in the alveolar bone when normal or T cell deficient nude rats received traumatic occlusion.
 Methods: Excessive occlusal force was loaded to the left first molar by bonding a metal wire in the left first maxillary molar of normal or nude rats. Histopathological changes were observed and the number of osteoclasts was counted in the furcation area at day 3 after application of mechanical force. Furthermore, CD4-positive T cells were immunohistologically evaluated in the bone resorption area.
 Results: Bone resorption was observed in the furcation area in both normal and nude rats at day 3 after application of mechanical force. The number of osteoclasts was not significantly different between normal and nude rats. CD4-positive T cells were not detected in the area of the bone resorption.
 Conclusion: It is suggested that T cells have little influence in the early phase of bone resorption in response to occlusal trauma.

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 Purpose: The prognosis for mandibular incisors after root canal filling is poor, even though there is only a single root. Thus, it is difficult to treat the root canal. Micro-CT, which enables specimens to be observed non-destructively, is used in various fields for studying internal structures. This study used micro-CT to examine the root canal morphology of mandibular incisors.
 Materials and Methods: Micro-CT examination was performed on 50 human extracted mandibular incisors. Based on the three-dimensional images, the root canal morphology, root canal axis, root canal length, root canal curvature, direction of apical foramen, and apical root canal morphology were analyzed.
 Results: Of 50 teeth, a single root canal was observed in 44 teeth, two root canals with one apical foramen in 5 teeth, and two root canals with two apical foramens in one tooth. Of 53 canals, the root canal axis was on the incisal edge in 27 canals, 25 canals on the labial side, and one canal on the lingual side. According to the observation from the labiolingual side, the root canal length was 19.25 mm on average, and 19.05 mm in the mesiodistal direction, and a difference was found depending on the measuring direction. Labiolingual curvature of the root canal was seen in 42 teeth, and severe curvature of 10 degrees or more was more common than curvature of less than 10 degrees. Mesiodistal curvature was seen in 30 teeth, and moderate curvature of less than 10 degrees was observed more frequently. In 8 teeth, the apical foramen and apex coincided with each other. The direction of the apical foramen deviated by 0.34 mm on average on the labial side from the apex, and by 0.03 mm on the mesial side. The apical root canal morphology according to observations from the mesiodistal direction was as follows: single constriction in 12 teeth, tapering in 12 teeth, parallel in 13 teeth, flaring in three teeth, apical delta in 9 teeth, and multi constriction in one tooth. From the labiolingual direction, single constriction was found in 5 teeth, tapering in 7 teeth, parallel in 37 teeth, and flaring in one tooth, and the morphological distribution differed depending on the direction of observation.
 Conclusion: The results of this study suggest that the complexity of root canal morphology due to bifurcation and curving of the root canal, and also the difficulty of preparing the access cavity due to labial-side displacement of the root canal axis, seem to cause the difficulties in root canal treatment.

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 Purpose: Direct Crowns made of a composite resin material have recently been developed by 3M ESPE. These crowns maintain the coronal morphology even in an uncured state. The advantage of Direct Crowns is that the entire process of crown fabrication until cementing and delivery can be completed chairside on the same day. However, there is little information available regarding the immediate bonding property of resin cement to light-cured composite resin crowns. Thus, this study examined the effects of time after crown fabrication on the bonding property.
 Methods: This study used a combination of composite resin and resin cement from the same manufacturer. The materials used were: Direct Crowns with RelyX Unicem 2 Automix (3M ESPE, USA) and Estenia C & B with Panavia F 2.0 (Kuraray Noritake Dental). Discs of Estenia C & B and Direct Crowns were fabricated and divided into the following four groups: bonding performed immediately after fabrication of discs ( (1) 0h-Direct Crown group and (2) 0h-Estenia C & B group) and bonding performed after 48 hours ( (3) 48h-Direct Crown group and (4) 48h-Estenia C & B group). A microtensile bond strength test was performed and the fracture surface was examined by scanning electron microscopy. ATR-FTIR (attenuated total reflection-fourier transform infrared spectroscopy) analysis was performed on the Direct Crowns.
 Results: The adhesive strength was significantly higher in the 0h-Direct Crown group (76.6±13.4 MPa) compared with the 0h-Estenia C & B group (60.9±14.8 MPa), the 48h-Direct Crown group (45.8±9.7 MPa), and the 48h-Estenia C & B group (53.7±12.5 MPa). When fracture surfaces were examined after the microtensile bond strength test, the 0h-Direct Crown group had many mixed fractures but no fracture at the interface between composite resin and resin cement. The other three groups had mainly mixed fractures and fractures at the interface between composite resin and resin cement. The results of ATR-FTIR analysis suggest that the degree of surface polymerization was low for Direct Crowns immediately after fabrication compared with Direct Crowns 24 hours later.
 Conclusion: The results of this study suggest that Direct Crowns are effective in clinical use with their high adhesion due to bonding immediately after fabrication.

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 Purpose: We have devised a technique for daily clinical practice whereby the treatment site is filmed with an intraoral camera and treatment is performed while viewing the images. This study compared the accuracy of cavity preparation between a method with an intraoral camera and with a mirror.
 Materials and methods: The subjects were 24 fourth-year dental students. They received training in cavity preparation of maxillary molars while viewing mirror images. They also received training in holding an intraoral camera with the left hand and filming a maxillary left first molar, and preparing cavities with the right hand while viewing images from the camera. When using the camera, the original images were rotated 180 degrees and right-left reversed so that the direction of hand-piece movement on the monitor was the same as the actual direction. In experiments, the maxillary left first molar was set in a mannequin, and cavity preparation was performed in the 12 o'clock position. The occlusal surface of this artificial tooth was flat and cruciform lines were printed in the center. The subjects were instructed to cut only inside between the cruciform lines with flat cavity floors using a diamond point attached to the turbine hand-piece. Cavity preparation for the first tooth was performed while viewing mirror images, and for the second tooth while viewing images from an intraoral camera. After cavity preparation, the teeth were assessed as to accuracy of outlines and flatness of cavity floors by two instructors with the naked eye. Statistics were analyzed by the chi-square test. Cavity preparation time was also measured and tested with Wilcoxon's signed rank sum test.
 Results: Out of 24 subjects, 21 had better outlines with an intraoral camera, while 3 received better outlines with a mirror. Out of 23 subjects, 19 had flatter cavity floors with an intraoral camera, while 4 received flatter floors with a mirror. Statistics indicated that significantly more subjects had better outlines and flatter cavity floors with an intraoral camera than with a mirror. Cavity preparation time was 158 seconds (±79 seconds) with a mirror, and 150 seconds (±52 seconds) with an intraoral camera. They were not significantly different from each other.
 Conclusion: Cavity preparation of the maxillary left first molar was performed significantly better while viewing images from an intraoral camera than while viewing mirror images.

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 Purpose: The management of a patient under intravenous bisphosphonate (BP) treatment who presented with a bone defect spreading to a peri-implant area is described. The lesion was diagnosed as apical periodontitis of an adjacent tooth and was treated by non-surgical root canal treatment (NSRCT) with a favorable outcome.
 Case description: A 51-year-old female visited our facility with a chief complaint of spontaneous pain in the left maxillary lateral incisor region and gingival swelling, and requested conservative treatment of the left maxillary central incisor, canine and implant in the left maxillary lateral incisor region. The patient was undergoing intravenous administration of a BP preparation (Zometa) to prevent metastasis of multiple myeloma. The left maxillary central incisor and canine evidenced pain on percussion, as well as apical tenderness in response to pressure. The tooth exhibited Class 2 mobility, and the probing depth was within 3 mm around the entire tooth. Sinus tracts were observed in the apical gingiva of the left maxillary central incisor and lateral incisor region. No redness or swelling of the gingiva in the area around the left maxillary lateral incisor implant was observed, nor was any mobility of the implant seen. The probing depth was 1 mm around the entire implant. Dental X-rays and CBCT revealed a radiolucent area centering primarily around the apices of the left maxillary central incisor and canine, including the implant in the left maxillary lateral incisor region. These findings indicated that although there was apical periodontitis of the left maxillary central incisor and canine, the possibility that infection had spread to the implant itself was low. The patient expressed a preference for non-surgical treatment. Accordingly, root canal treatment, which is a non-surgical endodontic approach, of the left maxillary central incisor and canine was initiated.
 One year after the crown prostheses were placed, the patient showed improvement. Moreover, no remarkable changes were observed in the left maxillary lateral incisor implant.
 Conclusion: In the case described here, a large bone defect was observed deriving from apical inflammation, and bone had resorbed in the peri-implant area. However, because the infection had not reached the implant itself, the peripheral bone may have regenerated as healing of the apical periodontitis progressed.

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