Background: Using senescence-accelerated mouse prone 8 (SAMP8), we examined whether reduced mastication from a young age affects hippocampal-dependent cognitive function. We anesthetized male SAMP8 mice at 8 weeks of age and extracted all maxillary molar teeth of half the animals. The other animals were treated similarly, except that molar teeth were not extracted. At 12 and 24 weeks of age, their general behavior and their ability to recognize novel objects were tested using the open-field test (OFT) and the object-recognition test (ORT), respectively. Results: The body weight of molarless mice was reduced significantly compared to that of molar-intact mice after the extraction and did not recover to the weight of age-matched molar-intact mice throughout the experimental period. At 12 weeks of age, molarless mice showed significantly greater locomotor activity in the OFT than molar-intact mice. However, the ability of molarless mice to discriminate a novel object in the ORT was impaired compared to that of molar-intact mice. The ability of both molarless and molar-intact SAMP8 mice to recognize objects was impaired at 24 weeks of age. These results suggest that molarless SAMP8 mice develop a deficit of cognitive function earlier than molar-intact SAMP8 mice. Interestingly, both at 12 and 24 weeks of age, molarless mice showed a lateralized preference of object location in the encoding session of the ORT, in which two identical objects were presented. Their lateralized preference of object location was positively correlated with the rightward turning-direction preference, which reached statistical significance at 24 weeks of age. Conclusions: Loss of masticatory function in early life causes malnutrition and chronic stress and impairs the ability to recognize novel objects. Hyperactivation and lateralized rotational behavior are commonly observed with dysfunction of the dopaminergic system, therefore, reduced masticatory function may deplete the mesolimbic and mesocorticolimbic dopaminergic systems to impair the cognitive functions of selective attention and recognition memory in the prefrontal cortex and the hippocampus.

Nagata K, et al. J Adv Prosthodont. 2025 Feb;17(1):1-10. https://doi.org/10.4047/jap.2025.17.1.1

The purpose of this study was to investigate the effect of denture adhesives on oral moisture in a 10-center parallel randomized clinical trial. Two hundred edentulous subjects wearing complete dentures were allocated into three groups: cream-type adhesive, powder-type adhesive and control groups. The adhesives (and saline solution in the control group) were applied to the mucosal surface of the dentures for 4 days, and baseline data and data after the intervention for eight meals over 4 days were obtained. For the main outcome, oral moisture was measured with a moisture checking device. Secondary outcomes were denture satisfaction, masticatory performance, denture retention, and occlusal force. In addition to between-group and within-group comparisons of oral moisture, investigations for secondary outcomes were undertaken in subgroups classified according to the degree of oral moisture at baseline (normal subgroup and dry mouth subgroup). Intention-to-treat analysis was also performed. Between-group and within-group comparisons of oral moisture showed no significant differences. The cream-type and powder-type denture adhesives were significantly effective in the dry mouth group for denture satisfaction ratings of ability to masticate, stability, retention, and comfort of mandibular dentures (p<0.05). The masticatory performance and retentive force of the dry mouth denture adhesive using groups were significantly improved after intervention (p<0.05). The oral moisture of complete denture wearers was not influenced by the use of denture adhesives. Our findings showed that denture adhesives improved subjective denture satisfaction, masticatory performance, and retention for complete denture patients with oral dryness.

Objective: The objective of this study was to investigate morphologically the progression of periimplantitis around an ultraviolet (UV)-light-irradiated implant in dogs. Materials and Methods: Pure titanium implants (3.3 mm in diameter and 8 mm long) were placed into dog jawbone bilaterally. Implants on one side were irradiated with UV light for 15 minutes using a photodevice immediately before placement (UV group), whereas those on the other side were not irradiated (non-UV group). Osseointegration was confirmed 90 days after implant placement by radiography. Experimental periimplantitis was induced by the application of dental floss over 90 days. Clinical and radiographic examination and micro-computed tomography (micro-CT) were performed after 90 and 180 days, and bone resorption was measured. The bone-implant interface in tissue sections was examined by light microscopy. Results: Bone resorption around the UV-irradiated implant was less pronounced than around the non-UV-irradiated implant in the ligature-induced periimplantitis model. Tissue section images revealed no contact and partial destruction at the bone-implant interface. Conclusion: Within the limitations of this preliminary investigation, it is suggested that UV-light-irradiated implants suppress spontaneous progression of periimplantitis.

Several efforts have been made to use virtual reality (VR) and augmented reality (AR) for medical and dental education and surgical support. The current methods still require users to wear devices such as a head-mounted display (HMD) and smart glasses, which pose challenges in hygiene management and long-term use. Additionally, it is necessary to measure the user’s inter-pupillary distance and to reflect it in the device settings each time to accurately display 3D images. This setting is difficult for daily use. We developed and implemented a novel anatomy education method using a spatial reality display capable of stereoscopic viewing with the naked eye without an HMD or smart glasses. In this study, we developed two new applications: (1) a head and neck anatomy education application, which can display 3D-CG models of the skeleton and blood vessels of the head and neck region using 3D human body data available free of charge from public research institutes, and (2) a DICOM image autostereoscopic viewer, which can automatically convert 2D CT/MRI/CBCT image data into 3D-CG models. In total, 104 students at the School of Dentistry experienced and evaluated the system, and the results suggest its usefulness. A stereoscopic display without a head-mounted display is highly useful and promising for anatomy education.

The major causes of oral candidiasis include decreased salivary flow rate and the use of ill-fitting dentures. However, the relationships among prosthetic treatment, saliva, and Candida albicans have not been elucidated. This study aimed to examine the effects of prosthetic treatment and changes in saliva (mainly the salivary flow rate) on oral candidiasis symptoms. Participants requiring prosthetic treatment underwent testing for C. albicans, salivary flow rate, intraoral symptoms, and bite force at the initial visit and four months after treatment to evaluate pretreatment and post-treatment changes. The relationships among C. albicans, salivary flow rate, dentures, and intraoral symptoms were analyzed using multiple regression analysis. Denture treatment improved activity against C. albicans as well as the salivary flow rate, intraoral symptoms, and masticatory function. Multiple regression analysis revealed that changes in the stimulated salivary flow rate due to prosthetic treatment significantly improved C. albicans detection (p = 0.011), intraoral symptoms (p = 0.037), and bite force (p = 0.031). This study showed that prosthetic treatment improved salivary flow and intraoral symptoms and confirmed the influence of stimulated salivary flow rate changes.