Periodontitis is one of the most common osteolytic inflammatory diseases in humans. Formation of a periodontal bacteria-associated biofilm is thought to be a trigger for the development of periodontitis, but it is not believed to be sufficient by itself to sustain the disease, as compromise of the host immune response is critical for inflammatory tissue breakdown and disease progression. Macrophages play an important role in the immune response both during the initiation and resolution of the inflammation. Macrophages are broadly classified into two phenotypes, pro-inflammatory M1 and wound-healing M2 cells. Since M2 macrophages contribute to the tissue-remodeling process, effective M2 macrophage induction would provide a favorable environment for resolution of the inflammation and tissue regeneration.

Mesenchymal stem cell (MSCs) have been applied for the purpose of inducing tissue regeneration and treating autoimmune disorders. Specifically, MSC-derived exosomes have attracted much attention for cell-free MSC therapy, because of their ability to transport vesicular cargo molecules, including growth factors and regulatory miRNAs, which mediate cell-to-cell communication. As compared with other somatic MSCs, gingival tissue-derived MSCs (GMSCs) have the unique capacity for pronounced immunoregulation and secrete large amount of exosomes. Recent studies have indicated that appropriate preconditioning of MSCs with disease-related stimuli can optimize the contents of the exosomes to efficiently support the repair of specific diseases.

In this review, we report the therapeutic effects of TNF-α-preconditioned-GMSC-derived exosomes on periodontal disease and discuss the underlying molecular mechanisms. Our study revealed that TNF-α-enhanced exosomal CD73 expression leading to anti-inflammatory M2 macrophage polarization and exosomal miR-1260b is an important negative regulator of osteoclastogenesis. Accordingly, our findings may pave the way for the development of a novel therapeutic strategy for patients with periodontitis.

In recent years, various risk factors and treatments for peri-implantitis, one of the most common complications after implant treatment, have been studied. Peri-implant mucositis or peri-implantitis is defined as infection of the plaque biofilm according to the new classification of EFP and AAP published in 2018. In order to prevent the development of peri-implant diseases, we would like to compare natural teeth and peri-implant tissues, especially focusing on peri-implant soft tissues, and consider methods to prevent these diseases that can be applied today.

Patients with periodontitis could lose teeth for reasons other than periodontal disease. The aim of this study was to assess the association of the use of the new periodontitis classification with changes in the incidence rate of tooth loss due to periodontitis (TLPD) and tooth loss due to other reasons (TLOR) during the maintenance phase. A total of 328 patients (mean age: 52.1 years) treated for periodontitis at a dental clinic who were followed up for periods ranging from 60 to 143 months were retrospectively categorized according to the new 2018 classification of periodontitis at the baseline. The association of the new classification of periodontitis with the cumulative incidence rate for tooth loss (TL) during the maintenance phase was explored using 1-KM survival analysis and Gray analysis. The cause-specific mortality was examined by regression analysis using a Cox proportional hazards model. No tooth loss was found in stage I or grade A patients during the maintenance phase. The 97-month cumulative incidence rates of TLPD were 6.6%, 3.4%, and 2.8% for stage IV, grade C, and generalized patients, respectively. Statistically significant differences were observed among stages and grades, and between extents. The multivariate Cox regression analysis demonstrated that the new periodontitis classification was associated with the cumulative incidence rate of TL and TLPD, but not of TLOR, although TLOR was associated with the number of teeth at the start of maintenance. The new periodontitis classification has been shown to be associated with TL and TLPD, but not with TLOR during the maintenance phase.

Recently, periodontal inflammatory surface area (PISA) has attracted attention as a new method of evaluation of the severity of periodontal disease for promoting medical-dental collaboration. PISA represents a quantitative estimate of the inflamed area of periodontal tissue and serves as an objective parameter of the severity of periodontal disease as a chronic inflammatory lesion of one organ. As there have been no related reports to date, we conducted this study to evaluate the relationship between PISA and the presence of diabetic complications such as arteriosclerosis. A total of 447 patients with diabetes who were hospitalized for diabetes education between April 2010 and March 2017 at Rakuwakai Otowa Hospital, Japan, were enrolled in the study. We excluded some of these patients from the initial evaluation, as follows: refusal of dental checkups (n=30), lack of radiographic data and/or data on the periodontal pocket depths (n=30), underlying type 1 rather than type 2 diabetes (n=41), and presence of an edentulous jaw (n=34). Finally, 312 patients with type 2 diabetes were included in this study. The results of our analysis showed no significant association between the severity of periodontal disease as evaluated by PISA and any specific complication of diabetes, however, a tendency was noted for association between the severity of periodontal disease and carotid arterial thickening.

In regard to the association with the diabetes severity, in the patient group with HbA1c levels of less than 10%, but not in the patient group with HbA1c levels of ≥10%, the odds ratio for carotid thickening (IMT ≥ 1.1) was significantly higher in the subjects with severe periodontal disease than in the subjects with mild periodontal disease. The odds ratio (95% CI) of carotid artery thickening adjusted for the gender, BMI, smoking habit, and drinking habit was 2.74 (1.02-7.40) (P < 0.05). On the other hand, there was no significant difference in the group with HbA1c levels of 10% or more.

Using PISA to assess the severity of periodontal disease, an association was found between the severity of periodontal disease and arteriosclerosis in diabetic patients with HbA1c levels of less than 10%.

Treatment for severe vertical bone resorption in periodontal tissue regeneration therapy includes the recently developed recombinant human FGF-2 therapy (REGROTH^®), bone graft, guided tissue regeneration (GTR), and enamel matrix proteins (Emdogain^® gel). We report an excellent long-term outcome in a patient with severe chronic periodontitis (stage IV, grade B) with secondary occlusal trauma, who underwent periodontal tissue regeneration therapy using artificial bone (hydroxyapatite: HA) grafting and hemisection.

The patient had malocclusions but suitable plaque control. However, seven years after the start of SPT (supportive periodontal therapy), the patient underwent long-term chemotherapy for cancer, which caused temporary taste disorder, but no onset of stomatitis. Eighteen years after the bone grafting, the HA remains without radiographic replacement or resorption, and there are no functional problems, it has not been a source of infection, and there have been no acute symptoms or periodontal pocket progression. We believe that thorough plaque control effectively maintains periodontal tissue after periodontal surgery and the oral environment during chemotherapy. We concluded that complete plaque control effectively maintains periodontal tissue after periodontal surgery and the oral environment during chemotherapy.

There are various methods of root coverage for gingival recession, and there are also various methods for recipient site formation in connective tissue graft (CTG), which is currently considered the gold standard for root coverage. Preoperative diagnosis is important to determine which technique to choose for the classification of gingival recession and to achieve a good prognosis. Herein, we report a 24-year-old female patient who visited our hospital because she was concerned about tooth loss following gingival recession of two mandibular central incisors. Both 31 and 41 were Maynard's classification Type 4, and the gingival recession was classified as Class III by Miller's classification and Recession Type (RT) 2 by Cairo's classification. Preoperative cone-beam computed tomography (CBCT) showed mild bone resorption on the labial side between 31 and 41, but no bone resorption on the lingual side. The distance between the roots near the alveolar crest was narrow between 41 and 42, and wide between 31 and 41, because of the centrifugal inclination of the 41 root. When performing CTG, there is no blood supply on the exposed root surface, so that it is important to ensure blood supply from the surrounding tissues. The interdental papilla plays an important role in this blood supply. In this case, for gingival recession of two mandibular central incisors according to Miller's classification Class III and Cairo's classification RT2, we used CBCT to determine the alveolar bone condition and measure the distance between the roots. Furthermore, considering the dimension of the interdental papilla, we selected the tunnel technique without incision into the interdental papilla for CTG, with good results. The results of this case are reported here.

Objective: A part of the clinical clerkship at the Nippon Dental University School of Life Dentistry was shifted to online lectures during the COVID-19 pandemic in 2020. Therefore, we conducted online lectures about student-generated clinical multiple-choice questions (MCQs) with the expectation that they would serve as a substitute for clinical clerkship and promote active learning. A questionnaire survey was performed after the online lectures to discuss the effects of this strategy on the students' learning.

Methods: A total of 124 students in the fifth grade were assigned to groups of 7 or 8 students and given the task of creating multiple-choice questions based on clinical cases. The assignment was done with active learning through group discussions and peer learning. Questionnaires were administered after all the lectures and analyzed quantitatively and qualitatively.

Results and Conclusion: After this course, 80% of the students thought that they had learned for themselves well, and about 60% said that their self-study time had increased. About 84% of the students also indicated that the discussions among students had been helpful for their learning. The quantitative text analysis based on free-text descriptions indicated that this course promoted "acquisition of knowledge, " "advancement of knowledge, " "a richer understanding, " and "ability to think independently. " We also believe that by listening to "others' opinions, " the students were able to fill gaps in knowledge and deepen their learning. However, some students were still reluctant to engage in learning, and it is necessary to consider further learning strategies to encourage more active learning and obtain better learning outcomes.