Purpose: Inorganic polyphosphates (polyPs) bind to the tooth surface and aid in removing stains and preventing stain deposition. In this study, we investigated whether the degree of polymerization of polyP affects the stain removal and prevention of stain deposition on the tooth surface. We also investigated whether polyP bound to the tooth surface suppresses demineralization.

 Methods: Hydroxyapatite powders stained with tea and coffee extracts were placed in centrifuge tubes, and purified water or polyPs solution of various chain lengths was added to it. The solution was mixed and then centrifuged to separate the hydroxyapatite. Further, unstained hydroxyapatite powder was mixed with polyPs solution or purified water in the same manner, and dyed with tea and coffee. The color of the hydroxyapatite powder for each sample was scanned using an image scanner, and the color density was measured to evaluate the extents of stain removal and prevention of deposition. An ivory plate was then sanded to prepare a smooth specimen. Each specimen was immersed in 1% polyP9.7-Saliveht solution or Saliveht for 10 min and then washed with water and dried. The specimen was then treated with 40% phosphoric acid for 20 min. After this, the phosphoric acid was washed off with water, and the specimen was dried. The cross-sectional depth of the demineralized portion after drying was observed with an optical microscope.

 Results: PolyP with a degree of polymerization of 9.7 (polyP9.7) was highly effective in removing stains and preventing deposition. PolyP9.7 was more effective in removing stains and preventing deposition than tripolyphosphate, a polymer of three phosphate residues commonly used in dentifrices, and polyP, which has a degree of polymerization of 60. In addition, demineralization was suppressed on the ivory surface treated with polyP9.7 upon phosphoric acid etching.

 Conclusion: PolyP9.7 is highly effective in removing stains and preventing deposition on the tooth surface and can suppress the demineralization by binding to the tooth surface.

 Purpose: Recently, dual-curing resin cements and self-etch adhesives have been increasingly used for indirect esthetic restorations to ensure optimal polymerization of resin cements and adhesives. However, attenuated light irradiation intensity may lead to severe clinical problems, because the polymerization of dual-curing resin cements and self-etch adhesives is greatly affected by the light-curing method. Some resin cement systems include catalysts both in resin cements and adhesives and the chemical copolymerization is facilitated when the adhesive comes in contact with the corresponding resin cement (touch-curing system), in order to improve the copolymerization of resin cements and adhesives. The purpose of this study was to evaluate the effects of the shade of indirect restorations on microtensile bond strengths (μTBSs) of resin cements using a touch-curing system to dentin.

 Methods: Twenty-four extracted human molars were randomly assigned to four experimental groups according to the four resin cements used in this study, which were PANAVIA V5 (PV) and Rely X Ultimate Adhesive Resin Cement (RU) as dual-curing resin cements using a touch-curing system, ESTECEM (EC) as a self-curing resin cement, and Rely X Veneer Cement (RV) as a light-curing resin cement. Indirect restorations were fabricated from resin composites (Pearl Este, shade DA2 and ODA2). After applying the corresponding adhesive of each resin cement to flat dentin surfaces and corresponding primer to resin discs, the resin discs were bonded to the dentin using each resin cement, and cured using a halogen light-curing unit. After storage in distilled deionized water at 37°C for 24 h, the specimens were sectioned into approximately 0.7×0.7 mm² pieces. Following that, each specimen was subjected to the μTBS test and the results were statistically analyzed using a t-test with Bonferroni correction (α=0.05). After testing, the fracture modes were determined and statistically analyzed using the Chi-square test (α=0.05).

 Results: In only the RV, which is a light-curing resin cement, there was a significant difference between the μTBSs of the DA2 and ODA2 groups. In both shade groups, the μTBS of PV, which uses a touch-curing system, was significantly higher than that of the other resin cements, and the μTBS of RV was significantly lower than that of EC and RU. The Chi-square test revealed no significant differences between the fracture modes of the DA2 and ODA2 groups in all resin cements.

 Conclusion: Within the limitations of this study, the shade of indirect restorations does not affect the dentin bond strength of dual-curing resin cements using the touch-curing system. This suggests that the touch-curing system may achieve adequate polymerization of dual-curing resin cements by attenuated light irradiation.

 Purpose: Aichi Gakuin University conducts basic phantom training in endodontics for fourth-year students in the School of Dentistry to allow them to acquire necessary basic knowledge, skills, and attitudes for the treatment of pulpal and periradicular diseases. Currently, the assessment of students’ basic training performance is mainly based on product evaluation; however, process evaluation and/or formative evaluation of students’ treatment techniques are also important. Therefore, we introduced a practical root canal treatment test as part of basic endodontic training to verify students’ techniques in using hand stainless-steel files.

 Methods: The subjects were fourth-year students in the School of Dentistry who participated in basic endodontic training: 138 in 2018 and 132 in 2019. The task was to enlarge and prepare the root canal of a maxillary anterior tooth using K-files and H-files with a standard technique. The test time was 5 minutes. One instructor assessed the skills of each student. Immediately after the test, the instructor provided each student with feedback. The students were asked to complete a questionnaire about the practical test at the end of the basic training.

 Results: The assessment by the instructors was generally good, averaging 11.3 points in 2018 and 12.2 points in 2019 out of 14 points. In response to the question “Was this practical test useful?”, more than 70% of the students (71.0% in 2018, 81.1% in 2019) said that it was “useful”. In response to the question “Was this practical test helpful for confirming your hand file technique?”, 44.5% in 2018 and 56.1% in 2019 answered “extremely helpful”, and 38.7% in 2018 and 33.3% in 2019 answered “helpful”. Regarding the feedback from the instructor, 84.8% in 2018 and 74.2% in 2019 considered that it was “very appropriate”.

 Conclusion: We were able to verify all fourth-year students’ hand file techniques in a way that could not be assessed by the Pre-Clinical Clerkship Objective Structured Clinical Examination. We were also able to provide each student with feedback. A practical test for root canal treatment in basic training may be useful for students, allowing them to consolidate the necessary basic skills in clinical practice.

 Purpose: In this study, we examined the usefulness of a new model of infected root canals for use as an in vitro experimental system, which was prepared by bacterial infection in the root canals of porcine extracted teeth.

 Methods: Following the extraction of porcine mandibular molars, their roots were divided into mesial and distal groups. Cleaning and shaping of the root canal were performed with instrumentation up to #60, in accordance with conventional methods. Root canals were filled with a suspension of Enterococcus faecalis cells (containing an approximately consistent number of bacteria) and cultured aerobically at 37°C for 21 days. The following analyses were performed before, immediately after, and 2 days after root canal irrigation with sodium hypochlorite solution: ①comparison of the number of E. faecalis in the root canal, using the serial dilution method; and ②SEM observation of the root canal surface.

 Results: Analysis using the serial dilution method showed that the number of E. faecalis decreased below the detection limit immediately after root canal irrigation with sodium hypochlorite solution; however, it had returned to a level comparable with the saline control at 2 days after irrigation. Furthermore, SEM observation showed no biofilm-like formation on the root canal wall surface immediately after irrigation with sodium hypochlorite solution, although it was again evident on the root canal wall surface at 2 days after irrigation.

 Conclusion: It was suggested that this infected root canal system model using porcine extracted teeth has potential for use as an in vitro experimental system in the endodontic field.

 Purpose: This study aimed to investigate the effect of saliva contamination (no saliva, mild saliva or severe saliva contamination) and/or dentin demineralization on the shear bond strength of restorative materials (two encapsulated glass ionomer cements and two resin composites) to bovine dentin.

 Materials and Methods: Four restorative materials, CAREDYNE ZIF-C (GC) and a glass ionomer Fuji Ⅶ CAPSULE (GC), and two resin composites, BEAUTIFIL Flow Plus X F03 (Shofu) and Filtek Supreme Ultra Flowable Restorative (3M Japan), were examined in this study. Bovine dentin was embedded into epoxy resin and polished using SiC#400 abrasive papers under running water. Six different dentin surface conditions were prepared: control, demineralization, mild or severe saliva contamination and those combinations of saliva contamination and demineralization. The restorative materials were bonded (3 mm in diameter, 3 mm in height) to each treated dentin surface and shear bond strengths were determined after 24 hours (n=15). Two-way ANOVA/Bonferroni and Weibull analyses were performed on the results.

 Results: Under the mild saliva contamination, demineralization did not affect the bond strengths of materials except for BEAUTIFIL Flow Plus X F03 (p>0.05). As compared to the control, the bond strength after the severe saliva contamination of CAREDYNE ZIF-C increased but that of BEAUTIFIL Flow Plus X F03 reduced (p<0.05). Resin composite treated by both severe saliva contamination and severe saliva contamination after demineralization showed lower Weibull moduli than the control.

 Conclusion: Surface saliva contamination and demineralization significantly affected the dentin bond strengths of restorative materials examined. Dentin demineralization significantly decreased the bond strength of restorative materials under the conditions without saliva and with severe saliva contamination. The results of Weibull analysis suggested that the bond strengths of glass ionomer cements were less influenced by demineralization and saliva contamination compared to those of resin composites.

 Purpose: Aichi Gakuin University Dental Hospital (AGUDH) established a micro-endodontic clinic in November 2018. Treatment at this clinic is all self-funded; we perform accurate root canal treatment using a dental operating microscope. Currently, patients unable to be treated at general dental clinics because of intractable conditions and/or anatomical problems attend this clinic. The purpose of this study was to investigate trends in the patients referred to the micro-endodontic clinic and to verify its role.

 Methods: This study evaluated data from new patients who attended the micro-endodontic clinic of AGUDH from 1 November 2018 to 31 May 2020. Information accessed included age, sex, address, referred teeth, clinical diagnosis, clinical symptoms, treatment procedures, number of treatments, and prognosis.

 Results: Forty new patients were referred over 19 months. Approximately 50% of the patients were in their 40s and 50s. More than 80% of the patients resided in Aichi Prefecture; of these, nearly 60% were from the city of Nagoya. The most frequently referred teeth were the maxillary anterior teeth, which made up 35.4% of the total, followed by mandibular molars, which made up 33.3% of the total. The clinical diagnosis was chronic apical periodontitis in every case and all were retreatment cases. Sixty-five percent of new patients were treated at the micro-endodontic clinic; of these, approximately 24.1% received only endodontic microsurgery and approximately 65.5% received infected root canal treatment.

 Conclusion: This survey showed that the micro-endodontic clinic of AGUDH plays an important role in the retreatment of cases that are too difficult to treat at general dental clinics. We will continue to promote coordination with regional medical institutions as a high-level medical facility. Information about the specialization and benefits of endodontic treatment should be disseminated throughout the local community.

 Purpose: Periodontal disease is a common infectious disease and bleeding on probing (BOP) is one of the major clinical markers for periodontitis, indicating local inflammatory burden. Many studies showed an association between periodontal disease and systemic health. Although deep periodontal pockets and increased clinical attachment level are associated with systemic diseases, only a few reports showed a link between BOP and systemic health. The aim of the present study was to assess systemic parameters related to BOP. In addition, the association between BOP and answers to a self-reported questionnaire was analyzed.

 Methods: Nine hundred and twenty-seven patients with cardiovascular diseases in Tokyo Medical and Dental University Hospital from 2012 to 2015 were enrolled in this study. Clinical periodontal examinations were performed and medical data were obtained from medical records. Subjective periodontal condition was asked using a self-reported questionnaire.

 Results: Parameters associated with BOP were male sex, smoking status, obesity, diabetes mellitus, and hypertension, while age and dyslipidemia did not show a relationship with BOP. Patients with subjective inferiority of their dental and periodontal condition had an increased BOP value. A multivariate analysis revealed that obesity, smoking, and male sex had a statistical association with BOP.

 Conclusion: The present study focusing on patients with cardiovascular diseases revealed an increase of BOP in obese patients, smokers, diabetes patients and patients with hypertension. Particularly, obese patients and smokers had a high BOP level after adjusting for gender. Dyslipidemia was not associated with BOP. Results of a questionnaire showed that those lacking knowledge or with subjective inferiority of their periodontal condition had an increased BOP value.

 Purpose: Endodontic-periodontal lesions are observed relatively frequently. The clinical symptoms can be similar to those of root fracture, perforation, and cementum detachment, therefore differential diagnosis is very important. We report a case of endodontic-periodontal disease caused by abnormal root morphology which was diagnosed as a root fracture at several dental clinics and was cured by endodontic treatment and periodontal tissue regenerative therapy.

 Case: A 41-year-old female. Chief complaint: Draining of the maxillary right central incisor and occlusal pain. Systemic history: No special notes. Current medical history: She had received initial endodontic treatment for a trauma-induced fracture of her anterior teeth about 30 years ago. After that, she had undergone re-treatment by her primary care physician twice due to caries and other reasons. When she visited another doctor in January 2018 for spontaneous pain, she was diagnosed with a root fracture of the upper right central incisor, and tooth extraction was recommended. She had a strong desire to preserve her tooth and consulted four dentists, but all of them diagnosed similar results. Therefore, she visited the Osaka University Dental Hospital in February 2018 for a detailed examination and treatment of the same site. Clinical findings: The maxillary right central incisor had a resin faced crown with spontaneous pain (+), percussion pain (+), gingival swelling (+), mobility (degree 2), root tenderness (+), sinus tract (−), and probing depth (PD, 11 mm) at the center of the palatal side. Cone beam computed tomography (CBCT) showed a large apex transmission image that expanded to the incisal canal. Diagnosis: Maxillary right central incisor, previously treated, acute periapical periodontitis, endodontic-periodontal lesion type III.

 Treatment process: On the first visit, after CBCT imaging, occlusal adjustment and removal of supragingival tartar, it was decided to sedate the acute inflammation with antibiotics. After the acute symptoms improved, the resin faced crown was removed and the infected root canal treatment was started. After treatment, the radiolucency of the apical region in the right upper incisor was reduced, so we performed root canal filling. Approximately 4 months after the infected root canal treatment, periodontal tissue regenerative therapy using REGROTH (Kaken Pharmaceutical) was performed as the PD was not fully improved even after the completion of the initial preparation. During the surgery, an abnormal root morphology was found in the center of the palate rather than a root fracture, and tartar-like calcite was deposited in the root sulcus. One year and four months after the surgery, periodontal tissue regeneration at the site was radiographically confirmed, and the clinical symptoms disappeared.

 Conclusion: The clinical examination showed that the apical translucency had extended to the incisal canal, and extraction of the tooth was thought to be appropriate at the first visit. However, the clinical symptoms were dramatically improved by ensuring the removal of the source of infection by CBCT and dental operative macroscope during endodontic treatment and periodontal tissue regenerative therapy for endodontic-periodontal disease due to abnormal root morphology not root fracture.