Akinori Ohno

Chewing-induced regional brain activity in edentulous patients who received mandibular implant-supported overdentures: A preliminary report

PURPOSE We used functional magnetic resonance imaging (fMRI) to investigate the change in brain regional activity during gum chewing when edentulous subjects switched from mandibular complete dentures to implant-supported removable overdentures. METHODS Four edentulous patients (3 males and 1 female, aged 64 to 79 years) participated in the study. All subjects received a set of new maxillary and mandibular complete dentures (CD), followed by a maxillary complete denture and a new mandibular implant-supported removable overdentures (IOD). A 3-T fMRI scanner produced images of the regional brain activity for each subject that showed changes in the blood-oxygenation-level-dependent (BOLD) contrast in the axial orientation during gum-chewing with CD and IOD. RESULTS Region-of-interest analysis showed that IOD treatment significantly suppressed chewing-induced brain activity in the prefrontal cortex. The chewing-induced brain activities in the primary sensorimotor cortex and cerebellum tended to decrease with IOD treatment, however they did not reach to significance level. There was no change in brain activity in the supplementary motor area, thalamus and insula between gum chewing with CD and IOD. Group comparison using statistical parametrical mapping further showed that, within the prefrontal cortex, the neural activity of the frontal pole significantly decreased during gum-chewing with IOD when compared to that with CD (P<0.05). CONCLUSION Despite the limitation of a small sample size, these results suggest that the gum-chewing task in elderly edentulous patients resulted in differential neural activity in the frontal pole within the prefrontal cortex between the 2 prosthodontic therapies-mandibular CD and IOD.

Loss of molars early in life develops behavioral lateralization and impairs hippocampus-dependent recognition memory

BackgroundUsing 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.ResultsThe 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.ConclusionsLoss 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.

Soft-food diet induces oxidative stress in the rat brain.

Decreased dopamine (DA) release in the hippocampus may be caused by dysfunctional mastication, although the mechanisms involved remain unclear. The present study examined the effects of soft- and hard-food diets on oxidative stress in the brain, and the relationship between these effects and hippocampal DA levels. The present study showed that DA release in the hippocampus was decreased in rats fed a soft-food diet. Electron spin resonance studies using the nitroxyl spin probe 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl directly demonstrated a high level of oxidative stress in the rat brain due to soft-food diet feeding. In addition, we confirmed that DA directly react with reactive oxygen species such as hydroxyl radical and superoxide. These observations suggest that soft-food diet feeding enhances oxidative stress, which leads to oxidation and a decrease in the release of DA in the hippocampus of rats.

Denture Treatment Improves Oral Discomfort Accompanying Dry Sensation

Aim: In recent years, the number of patients complaining of symptoms of oral discomfort such as dry mouth, tongue pain, and burning sensation of the mouth has been increasing. This study aimed to determine whether denture treatment improved oral discomfort accompanying dry and sticky sensations. Methods: Forty-eight partial and/or complete denture wearers complaining of oral discomfort were recruited from non-xerogenic patients with normal salivary flow after obtaining informed consent. Measurement outcomes were: 1) subjective symptoms evaluated by self-administered questionnaire, including five questions on oral discomfort; 2) objective symptoms such as congestion and erosion of the tongue, erosion and congestion of the palate, and angular stomatitis evaluated by one dentist; and 3) unstimulated and stimulated salivary flow rates. Outcomes were evaluated before and after denture treatment. Mean differences in outcomes between before and after denture treatment were analyzed by Wilcoxon signed-rank test, then multiple regression analysis was applied to determine predictive variables associated with each score. Results: All outcomes were improved by denture treatment. Both unstimulated and stimulated salivary flow rates were significantly increased (p=0.042, p=0.014). Multiple regression analysis revealed that new denture fabrication improved stimulated salivary flow much more than only adjustment of the existing denture, and stimulated salivary flow significantly reduced objective symptoms (p=0.020), and sensations of dryness (p=0.010), pain or burning in the mouth (p=0.029). Conclusions: The results suggest that denture treatment improves salivary flow and reduces oral discomfort.

Influence of ultraviolet irradiation treatment on porcelain bond strength of titanium surfaces

To determine the effect of titanium (Ti) surface modification by ultraviolet irradiation (UVI) on the bond strength between Ti and porcelain. Grade 2 Ti plates were allotted to five groups: sandblasted (SA), 15 min UVI (UV), SA+5 min UVI (SA+UV5), SA+10 min UVI (SA+UV10), and SA+15 min UVI (SA+UV15). After surface treatment, porcelain was added. A precious metal (MC) was used for comparison with Ti. The effects of 24-h storage at room temperature versus thermal cycling only at 5 and 55°C in water were evaluated. Subsequently, the tensile strength of each sample was tested. Data were analyzed using one-way analysis of variance and the Tukey test. In both the room temperature and thermal cycling groups, the MC and SA+15 min UVI samples showed significantly greater bond strengths than the other samples (p<0.05). UVI processing efficiently increases the bond strength between porcelain and the Ti surface.

Bond Strength and Water Resistance of a Resin Composite Bonded to Glass Plates Treated with Commercial Ceramic Primers

Background: Silane coupling agents are used as a bonding agent between ceramics and resins in dentistry. The effectiveness of these agents is often enhanced by the addition of acid or by heat treatment. Objective: This study aimed to evaluate, the clinical characteristics, TBS (tensile bond strength) and water resistance of eight commercial ceramic primers (seven silane coupling agents and one alumina zirconia primer). Method: Glass plates were used as the adherent. The TBS of the resin composite and the wettability of the resin monomer to glass surfaces treated with ceramic primers was investigated, with 3-MPS (methacryloxypropyltrimethoxysilane) used as a control. The values obtained from the experiments were analyzed using one-way ANOVA followed by Tukey’s multiple comparison tests (p < 0.05). Results: No significant differences in TBS were observed between the commercial products and MPS, except for the alumina zirconia primer. However, four products (three of the seven agents and the alumina zirconia primer) exhibited significantly lower TBS values after application of thermal stress when compared with those stored in water (p < 0.05). All but one of the eight primers displayed significantly higher contact angles between the treated glass and the resin monomer when compared with MPS (p < 0.05). These results suggest that some commercial ceramic primers may contribute to increased strength and durability.

Erratum to “Soft-food diet induces oxidative stress in the rat brain” [Neurosci. Lett. 508 (2012) 42–46]

Division of Fixed Prosthodontics, Department of Oral and Maxillofacial Rehabilitation, Kanagawa Dental College, Yokosuka 238-8580, Japan Division of Pharmacology & ESR Laboratories, Department of Clinical Care Medicine, Kanagawa Dental College, Yokosuka 238-8580, Japan Department of Electronics and Bioinfomatics, School of Science and Technology, Meiji University, Kamsaki 214-8571, Japan Department of Physiology and Neuroscience, Kanagawa Dental College, Yokosuka 238-8580, Japan

Molar extraction accelerates the ageing process of the hippocampus in SAMP8 mice

P3-q09 Molar extraction accelerates the ageing process of the hippocampus in SAMP8 mice Masatsuna Kawahata 1 , Yumie Ono 2, Akinori Ohno 1, Syouichi Kawamoto 1, Katsuhiko Kimoto 1, Minoru Onozuka 3 1 Dept.of Oral & Maxillofacial Rehabilitatin Kanagawa Dent. Col., Kanagawa, Japan 2 Dept. of Elec. and Bioinformatics, Sch. of Sci. and Eng., Meiji Univ., Kanagawa, Japan 3 Dept. Physiol. and Neurosci. Kanagawa Dent. Col., Kanagawa, Japan

Effects of mastication with differences of food texture on oxidative stress and dopamine release in the rat brain

that ACE inhibition enhances A 42 deposition. ACE is one of the most commonly targeted enzymes by inhibitors in elderly hypertensive populations. To investigate whether ACE inhibition leads to neurodegeneration in the brain of Alzheimer’s disease mouse model, we performed a long-term treatment of Tg2576 mice with a high or a low dose of ACE inhibitor. The treatment with high dose ACE inhibitor significantly reduced blood pressure and resulted in a lower survival rate of mice compared with the control and the low-dose treatment. In addition to the increase of A 42 deposition, other Alzheimer-like pathologies were also found in the brain of the high-dose ACE inhibitor treatment group. These results suggest that potent inhibition of ACE may be a risk factor for the development of Alzheimer’s disease.

Effect of chewing on stress-induced dopamine and serotonin releases in the rat hippocampus

We previously reported that brain thromboxane A2 is positively involved in the central regulation of plasma catecholamine levels in uretrhane-anesthetized rats. In the present study, we pharmacologically analyzed the role of inflammatory mediators in the restraint stress-induced elevation of plasma catecholamines (noradrenaline and adrenaline). The Restraint stress (8 h) elevated plasma catecholamines levels (adrenaline > noradrenaline). The elevations of both catecholamines reached the peak about 30 min after the restraint stress. Intraperitoneal administration of indomethacin (10 mg/kg, a non-selective cyclooxygenase inhibitor), NS-398 (5 mg/kg, a selective cyclooxygenase 2 inhibitor), daltroban (20 mg /kg, a selective thromboxane A2 receptor antagonist), CP-154,526 (20 mg/kg, a selective CRF1 receptor antagonist), PDTC (200 mg/kg, a NF B inhibitor) or MK 801 (2 mg/kg, a NMDA receptor antagonist) reduced the stress-induced elevation of plasma catecholamines. These results suggest that brain inflammatory mediators are important component of the restraint stress-induced elevation of plasma catecholamines.