Although the number of roots and root canals is decided by tooth type, extra roots and additional root canals are sometimes observed and so knowledge of the morphology of these roots and root canals is required for successful root canal treatment. The mesio-buccal root of a maxillary molar often has two canals, and the second root canal, which is located palatally, is called the mesio-buccal root second canal (MB2). MB2 is relatively common, but it is often difficult to find without a loupe or microscope. The root canal orifice of MB2 is located 0.5-1.0 mm more mesial aspect from MB1 and the palatal root canal line. For the treatment of MB2, it is important to find the root canal orifice and coronal enlargement. The disto-lingual root of the mandibular molar is called Radix Entomolaris. Radix Entomolaris is often observed in Japanese, Taiwanese and Chinese populations. The treatment of Radix Entomolaris is not easy because of the curvature to the buccal aspect of this root. Coronal enlargement, negotiation with small-sized files and glide path processes are important. A very rare extra root, which is found on the mesio-buccal side of mandibular molars, is called Radix Paramolaris. The mesial root of a mandibular molar usually has two canals, but sometimes has an additional canal, called the middle mesial (MM) canal. The prevalence of MM canals depends on the race and seems to be less common in Japanese. MM canals are prepared with stainless steel files or nickel-titanium files. It has been suggested that a prepared MM canal is just part of the enlarged isthmus; preoperative CBCT is recommended to confirm this. For successful root canal treatment, it is important to understand the root and root canal morphology of each individual patient before commencing treatment.

 Purpose: It is well established that video teaching materials are useful for improving the learning efficiency of dental students in mastering dental treatment procedures. However, no study has examined the effectiveness of video teaching materials in periodontal treatment. In the study, we investigated the effectiveness of using video as a teaching tool to enable students to understand initial periodontal therapy techniques, which are difficult to grasp using illustrations and photographs alone.

 Methods: Twenty third-year students of Kanagawa Dental University who advanced to the next grade in April 2021 and provided informed consent participated in the study. They were randomly divided into two groups: a video group (four females and six males) and an image group (five females and five males). Each group received a lecture on initial periodontal therapy (bass method, modified Stillman method, scaling and root planing, and sharpening) using videos or images. After the lecture, two teachers evaluated seven tasks according to the established evaluation criteria. Statistical analyses were performed using Fisher’s exact test and Welch’s t-test at a significance level of 5%.

 Results: The results were tabulated for each assignment, with “completed” being defined as two evaluators judging the assignment to have met the standard, and “not completed” being defined as the assignment not having met the standard. There were no significant differences between the two teaching methods in any of the tasks. Next, the total score (out of 7 points) was calculated for the seven tasks, with 1 point allotted when all evaluators judged that the standard was met, 0.5 points allotted when only one evaluator judged that it was met, and 0 points given when the two evaluators judged that it was not met. The results showed that the mean score of the video group was significantly higher (p=0.012).

 Conclusions: The video materials on initial periodontal therapy effectively helped students acquire treatment skills and techniques. However, the effectiveness of video materials may vary depending on the content and target audience,

 Purpose: We have been studying the use of an intraoral scanner (IOS) in dental health guidance to quantify and visualize changes in periodontal tissues, to make it easier for patients to understand the state of periodontal tissues, and to improve the accuracy of examining the effects of treatment. In this study, the usefulness of dental health guidance using IOS was examined by comparing conventional dental health guidance methods and dental health guidance using IOS for faculty, staff, and students of the University who had not received dental health guidance.

 Subjects and Methods: The study subjects were a total of 9 faculty, staff, and students (mean age 41.6 years) who had never received adequate dental health guidance. Three dental hygienists provided the following dental health guidance at intervals of at least two weeks for each subject, in different order. (1) Conventional method 1: Dental health guidance without intraoral photographs, study models, or IOS records. (2) Conventional method 2: Dental health guidance using intraoral photographs and study models. (3) IOS method: Dental health guidance using IOS records (images showing changes in intraoral conditions and gingiva). In each dental health guidance, periodontal examination, plaque control record (PCR), and gingival condition were recorded on the survey form, and the oral cavity was scanned by IOS (TRIOS 3, 3Shape, Denmark). After the second recording, the subjects were asked to fill out a questionnaire about their discomfort during recording and the ease of understanding the instructions. IOS records were exported as 3D data in STL format and analyzed using 3D measurement data evaluation software.

 Results: The IOS recordings allowed for a more detailed examination of gingival changes than the conventional periodontal examination. The deviation of the marginal gingival surface obtained by aligning the IOS records had a poor relationship with the results of probing depth, gingival swelling and redness, and changes in BOP. No difference in guidance effectiveness was found between dental health guidance using IOS and conventional guidance methods.

 Conclusion: Currently, the clinical usefulness of dental health guidance using IOS is not high. Although the positional alignment of IOS records one tooth at a time can provide a very detailed examination of gingival changes, it is not clinically useful because it takes a very long time; block-by-block alignment is regarded as more appropriate. However, recording by IOS is a method that allows detailed gingival evaluation from a different viewpoint than conventional periodontal examination and is easy to understand for both the dental hygienist and the patient.

 Purpose: Metformin (MT) has become the first-line drug for the treatment of type 2 diabetes mellitus, and studies on its effects on periodontitis have recently begun to attract attention. In this study, we aimed to clarify whether local MT administration to the gingiva is effective in preventing periodontitis.

 Methods: Ten male C57BL/6J mice aged 60-70 weeks (Aged group) and ten male C57BL/6J mice aged 10 weeks (Young group) were subjected to the experiment, and were divided into two groups: an experimental group that was topically administered 1% MT solution, and a control group that was topically administered PBS. Seven days after the last administration, the mice were sacrificed and maxillary bone and peripheral venous blood samples were collected. Micro-CT images were taken of the maxillary bone, and the histological images were observed by HE staining of the tissue sections. The collected blood was analyzed for cytokines in serum. The palatal gingiva was collected from two mice in each of the Aged experimental group and the Aged control group, and the expression of wound healing-related genes from the gingiva was quantitatively analyzed. Twelve aged mice were divided into experimental and control groups as in experiment 1, and their maxillary right second molars were ligated with silk threads, and the maxillary bones were harvested after 4 days of ligation. The amount of alveolar bone resorption from micro-CT images, the number of inflammatory cells, and the number of TRAP-positive cells were measured from histological images of the maxillary bones. The Tukey test was used as a post-hoc test after analysis of variance (ANOVA) , and the significance level was set at 5%.

 Results: There was no change in the amount of alveolar bone in the Aged and Young groups compared to the experimental and control groups. Histological images of the Aged experimental group showed that the junctional epithelium around the site of administration was maintained. The expression of wound-related genes was decreased in the Aged-MT group, while the expression of healing-related genes was higher in the aged-MT group. There was no significant difference in the serum cytokine levels. In Experiment 2, alveolar bone resorption in the PBS-ligated group was significantly higher than in the MT-non-ligated and PBS-non-ligated groups. The number of inflammatory cells in the MT- and MT-non-ligated groups was significantly lower than in the PBS-ligated group. The number of TRAP-positive cells was significantly higher in the PBS-ligated group than in the PBS-non-ligated, MT-ligated, and MT-non-ligated groups.

 Conclusion: Local administration of MT to the gingiva of aged mice maintained the amount of collagen fibers in the gingival connective tissue and suppressed inflammation in the gingival tissue. Local administration of MT before ligation suppresses inflammation and bone resorption during the development of experimental periodontitis. These results suggest that local MT administration in the gingiva may effectively prevent the onset of periodontitis.

 Introduction: Cases have been reported in which adhesive bridges with a low amount of preparation were used for anterior single tooth defects as a result of improved adhesive strength. However, appropriate tooth selection is as important as devising a method to prevent detachment when conditions are unfavorable. In this report, we describe a case in which a single-retainer adhesive bridge was used to restore a tooth and a wide defect with horizontal alveolar crest resorption after improvement of the condition.

 Case: The patient, a 67-year-old woman, visited our clinic because the crown of a maxillary right lateral incisor that had been extracted four years earlier and was bonded to both adjacent teeth, had become detached. The maxillary right lateral incisor defect was wide both proximally and distally, and horizontal alveolar crest resorption was observed. The maxillary right central incisor and canine were healthy.

 Progress: To restore esthetics and apply an ovate pontic, connective tissue was harvested from the palate of the maxillary right molar and grafted to the maxillary right lateral incisor. Composite resin was added to the proximal maxillary right canine to narrow the proximal width of the defect. Using the central incisor as the abutment, a single-retainer zirconia bonded bridge with an ovate pontic was then placed on the lateral incisor space. No dehiscence or fracture was observed for two years after bonding.

 Conclusion: For anterior tooth defects with horizontal resorption of the alveolar crest leading to a wide defect, single-retainer adhesive bridges can be applied by reducing the space with alveolar crest augmentation and composite resin addition, with high patient satisfaction.