求心性の歯周組織感覚入力により誘発された前頭前野の活動は咬合力を抑制する

The prefrontal cortex (PFC) plays an important role in several cognitive functions, such as planning, decision making, and social behavior. We previously reported that periodontal sensory input significantly increases PFC activity during the motor task of maintaining occlusal (biting) force. However, the relationships between periodontal sensation, PFC activity, and the performance of motor tasks, have not been evaluated in detail. Therefore, using functional near-infrared spectroscopy, we investigated PFC activity by monitoring changes in cerebral blood flow (CBF) to specific areas of the PFC that corresponded to changes in occlusal force generated during 4 different biting tasks: 1) occlusion with the central incisor with an interocclusal distance of 5 mm (BI-5 mm); or 2) 10 mm (BI-10 mm); 3) occlusion with the first molars with an interocclusal distance of 5 mm (BM-5 mm), or 4) 10 mm (BM-10 mm). Occlusion of molars generated increased PFC regional CBF as the interocclusal distance decreased (BM-10 mm vs BM-5 mm). No significant differences in CBF during occlusion of incisors were found when comparing 5 mm and 10 mm intercostal distances (BI-5 mm vs BI-10 mm). The mean occlusal force generated by BM-5 mm occlusion was significantly lower than that generated by BM-10 mm occlusion. Taken together, our results suggest that the PFC decreases efferent signaling to motor units, to reduce occlusal force generated when periodontal sensation, which is greater when the interocclusal distance is reduced, is primarily responsible for maintaining occlusal force in the absence of sensations from the temporomandibular joint and muscle spindles

Investigating Eating Behaviors and Symptoms of Oral Frailty Using Questionnaires

A questionnaire survey was conducted to investigate eating behavior and the subjective symptoms of oral frailty, and to examine the relationship between them. A total of 744 subjects with ages over 65 years were included. The questionnaire comprised 18 question items indicating eating behavior and seven question items indicating oral frailty. All items were assessed according to 4 grades on a scale of 1 (not applicable) to 4 (applicable). The total score of oral frailty gradually increased with age. Regarding the scores for “eating recognition” and “eating habits”, no changes were observed, however the scores for “eating action” demonstrated a decreasing tendency with age and the scores of ≥ 85 years age group was significantly lower than the 65–69, 70–74, and 75–79 years age groups. As a result of multiple regression analysis, among the significant independent variable, the scores of “I do not chew foods well” under the category of “eating action” showed the highest standard partial regression coefficients for dependent variable of symptoms of oral frailty. The significant association was found between the eating behavior and subjective symptoms of oral frailty, and this study suggests that the good chewing habit might be an important criterion for the prevention of oral frailty

Does Masticatory Ability Contribute to Nutritional Status in Older Individuals?

Mastication plays a primary role in the process of eating. Hence, compromised masticatory ability may affect the nutrition and quality of life, which are particularly important concerns among older individuals. It remains unclear how is the masticatory ability assessed regarding the nutritional status. We examined the effect of various oral factors on three masticatory ability tests conducted among older individuals. A total of 100 older individuals were enrolled in this study. Body mass index (BMI) as an indicator of nutritional status; and age, sex, and the number of occlusal and molar occlusal supports as clinical attributes were recorded. Three masticatory ability tests (masticatory efficiency, masticatory score, and satisfaction with mastication) were conducted, and tongue pressure, cheek pressure, and occlusal force were assessed as oral functions. A significant but weak correlation was found between masticatory efficiency and the masticatory score, but not between masticatory efficiency and satisfaction score. Objective masticatory efficiency was strongly associated with objective oral factors, whereas subjective assessments of masticatory ability (masticatory score and satisfaction score) were not. Furthermore, BMI was significantly associated with subjective assessments of masticatory ability but not with objective masticatory efficiency. Both subjective and objective assessments of masticatory ability, along with considerations of nutritional formulations, are required for the maintenance and improvement of nutritional status in older individuals

Expectation Management in a Global Collaboration Project Using a Deterministic Design Approach

Expectation management in product engineering design aims at setting achievable goals for both customers and designers, while leaving room for creativity and passion. This is especially challenging in the global workplace. Using an example of a design project, the Dental Headrest project (DHR), this paper reviews how expectations were managed in a successful, collaborative project between the University of Tokushima (UT) and Massachusetts Institute of Technology (MIT). The goal of the project was to design an innovative mechanism for the positioning a dental chair headrest so satisfy both the needs of a patient for comfort and a clinician for flexibility and access. The design team was formed with six students from the MIT MechE’s Precision Machine Design class, while the challenge proposed by a UT team of dentists and design engineers. The team followed a deterministic design procedure inducing understating the challenge and reviewing prior art, strategy and concept generation, detailed module design and fabrication and testing, culminating in presentation and documentation. Through the process was coordinated by online communication and collaborative working spaces which ensured real-time information transfer between the continents. The conclusion was a face-to-face meeting between the two institutions. This DHR project resulted in an innovative design of headrest adjusting mechanism that was implemented in a prototype. Moreover, the students, faculty and clinicians benefitted from the experience of innovative design collaboration in a multidisciplinary, global team.CIMIT: Center for Integration of Medicine and Innovative TechnologyJ. Morita Corporatio

Application of artificial intelligence in the dental field : A literature review

Purpose: The purpose of this study was to comprehensively review the literature regarding the application of artificial intelligence (AI) in the dental field, focusing on the evaluation criteria and architecture types. Study selection: Electronic databases (PubMed, Cochrane Library, Scopus) were searched. Full-text articles describing the clinical application of AI for the detection, diagnosis, and treatment of lesions and the AI method/architecture were included. Results: The primary search presented 422 studies from 1996 to 2019, and 58 studies were finally selected. Regarding the year of publication, the oldest study, which was reported in 1996, focused on “oral and maxillofacial surgery.” Machine-learning architectures were employed in the selected studies, while approximately half of them (29/58) employed neural networks. Regarding the evaluation criteria, eight studies compared the results obtained by AI with the diagnoses formulated by dentists, while several studies compared two or more architectures in terms of performance. The following parameters were employed for evaluating the AI performance: accuracy, sensitivity, specificity, mean absolute error, root mean squared error, and area under the receiver operating characteristic curve. Conclusion: Application of AI in the dental field has progressed; however, the criteria for evaluating the efficacy of AI have not been clarified. It is necessary to obtain better quality data for machine learning to achieve the effective diagnosis of lesions and suitable treatment planning

Does Periodontal Tactile Input Uniquely Increase Cerebral Blood Flow in the Prefrontal Cortex?

We previously studied the effect of peripheral sensory information from sensory periodontal ligament receptors on prefrontal cortex (PFC) activity. In the dental field, an alternative dental implant without periodontal sensation can be applied for missing teeth. In this study, we examine whether periodontal tactile input could increase cerebral blood flow (CBF) in the PFC against elderly patients with dental implants lacking periodontal tactile (implant group), elderly individuals with natural teeth (elderly group), and young individuals with natural teeth (young group). The experimental task of maintaining occlusal force as closed-loop stimulation was performed. Compared with the young group, the elderly group showed significantly lower CBF. Contrastingly, compared with the young group, the implant group showed significantly lower CBF. There were no significant differences between the elderly and implant groups. Regarding the mean occlusal force value, compared with the young group and the elderly group, the implant group had a numerically, but not significantly, larger occlusal force exceeding the directed range. In conclusion, the periodontal tactile input does not uniquely increase PFC activity. However, increased CBF in the PFC due to the periodontal tactile input in the posterior region requires existing attention behavior function in the PFC

Use of a Polyetheretherketone Clasp Retainer for Removable Partial Denture : A Case Report

Clasp retainers made of metal alloys may be esthetically unappealing or cause allergic reactions. To investigate alternative materials, we used the nonfiller polyetheretherketone (PEEK) to fabricate the clasp retainer of a removable partial denture for the mandibular bilateral distal free-end abutment of an 84-year-old female. Two years later, few color and texture changes of PEEK were found macroscopically. The rest part and the clasp arm fitted well without any deformation. There were no particular occlusal or periodontal problems. Subjective satisfaction was expressed by both the practitioner and the patient

ニッケルアレルギー惹起相におけるセマフォリン７Aの効果

Background: Metal allergy is caused by many factors, including cells, cytokines, chemokines, or the environment. Recent studies suggested semaphorin7A (Sema7A), expressed on activated T cells, is crucial to produce inflammation through α1β1 integrin on monocytes and macrophages. However, the role of Sema7A on keratinocytes in metal allergy is still unclear. In this study, we focused on keratinocytes since they are known as an important player for skin immunity, and analyzed the effect of Sema7A expressed on keratinocytes in the development of metal allergy. Materials and Methods: Mouse keratinocyte line PAM2.12 cells were treated with NiCl2 to analyze the expression of Sema7A. Ni allergy was induced in female C57BL/6J mice (6-8 weeks old) with or without Sema7A suppression to confirm if Sema7A is necessary to produce allergic reactions to NiCl2. Results: NiCl2 enhanced the expression of Sema7A in a dose and time-dependent manner after 72 hours of stimulation. PAM 2.12 produced TNF-α in response to NiCl2, and this secretion was reduced by Sema7A inhibition. In a mouse model, ear thickness, at 48 hours after NiCl2 injection, was significantly decreased by Sema7A siRNA administration. Conclusions: Sema7A is essential to produce an allergic reaction to NiCl2, especially during the effector phase. Since the interaction between Sema7A and α1β1 integrin enhances inflammation in many skin diseases, this interaction may also have possibilities to be a therapeutic target for metal allergy