We used electromyography to evaluate the effect of relining removable partial dentures. Electromyograms (EMG) of the bilateral anterior temporalis and masseter muscles were recorded before relining and for two weeks after on eight patients, together with mandibular kinesiograph (MKG) motions during tapping, clenching and mastication of peanuts and raisins. During tapping and mastication, the parameters analyzed were the EMG time parameters (duration, interval, and cycle time), their integrated values, and their respective averages and coefficients of variation (CV). The mean voltage was also measured during clenching. The CV for the EMG time parameters and integrated EMG during mastication of peanuts and raisins were significantly lower immediately after relining and one and two weeks after relining when compared with the situation before relining. EMG burst activity during clenching and during mastication of peanuts and raisins was significantly greater immediately after relining compared with before relining. The results indicated that the CV of EMG time parameters and integrated EMG and EMG burst activities during clenching and mastication are effective parameters for evaluating denture relining.

View full abstract

β-Lactam antibiotics are widely used in the treatment of infectious diseases. However, certain odontogenic infectious diseases become intractable because of antibiotic-resistance developing in obligate anaerobic Gram-nagative rods (OGNRs). We studied 12 strains of 7 oral OGNRs isolated from the saliva of adult humans for elucidation of the β-lactam antibiotic-resistant mechanism in odontogenic infectious diseases. Bacteria in saliva were anaerobic-cultured and Gram-stained. Subsequently, β-lactamase producibile-and-resistant oral OGNRs were isolated by acid sensibility, β-lactamase producibility and minimal inhibitory concentration (MIC) studies. DNA polymerase chain reaction (DNA-PCR) sequencing of the oral OGNR was performed with designed primers and compared with data from the DNA Data Bank of Japan (DDBJ). The PCR products were further induced for gene-transformation in Escherichia coli (E. coli). A 922-944 bp PCR product showing homology with the known β-lactamase gene was acquired in the specimens sequenced with CfxA2 primers. Certain PCR products were also observed in other primers. Although all the PCR products were transformed in E. coli, β-lactamase productivity was confirmed only with selective culture media. These results show that the β-lactamase gene is not specific in oral OGNRs. However, although the gene is widely found in oral OGNRs, it is usually not expressed in OGNR strains isolated from areas other than the oral cavity.

View full abstract

We investigated immunohistochemical expression of p21^WAF1/CIP1 (p21) and TGF-β in rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide (4 NQO). The protein p21, which inhibits cell proliferation, is induced by the wild type p53 tumor suppressor protein and by TGF-β. Expression of the p21 protein almost disappeared in tongue epithelial cells at 16 weeks after 4 NQO administration, while it showed overexpression at 24 weeks. TGF-β was found in small amounts at 16 weeks and was expressed strongly at 24 weeks after administration of 4 NQO. Our co-worker previously found that a p53 mutation occurred in the tongue epithelium at 16 weeks using the same model. Therefore, the overexpression of p21 at 24 weeks may be induced by TGF-β. We also found that expression of Ki-67 was decreased at 24 weeks, which we assumed was caused by changes in p21. However, the inhibitory effect of p21 on carcinoma is not adequate to stop carcinogenesis. This study suggests that expression of p21 in the rat tongue changed as a result of carcinogenesis, and that p21 overexpression in carcinoma may be induced by TGF-β.

View full abstract

We used Western blotting and protein antibody array (AB array) to examine protein changes induced by vitamin A at the time of increased amelogenin and enamelin mRNA in ameloblastoma-like cells. Western blotting showed that vitamin A induced upregulation of Notch and Sonic hedgehog (SHH) proteins. AB array showed that the upregulation induced by vitamin A decreased Ras-GRF2 and Rho-GDI, while it increased TNFα and TRADD compared with the controls. These results indicated that the vitamin A acted to control ameloblastoma-like cell redifferentiation and inhibited growth.

View full abstract

We examined the metallic artifacts created in magnetic resonance images (MRI) of various orthodontic appliances placed on plastic study models. We used steel, ceramic and resin brackets, steel, NiTi, heat-activated NiTi and Beta-Ti orthodontic wires, and steel and elastic ligatures. By six sequences (spine echo for T1 weighted images, fast spine echo for T2 weighted images, fast spine echo for T2 weighted fat suppression images, gradient echo for T2 weighted images, fast gradient echo for 2 dimensional T2 weighted images and fast gradient echo for three dimensional T2 weighted images). A 1.5 tesla super-conductive MRI machine was used to make six sequences of images. A model that adapted steel brackets, steel wire and steel ligatures produced the largest metallic artifacts in the MRI. A model with steel brackets alone produced large metallic artifacts while a model with ceramic brackets and Ti wire did not produce large metallic artifacts. In addition to the signal loss caused by the metallic artifacts, image distortion was spread over a wide area. We concluded that orthodontists should not use steel orthodontic brackets and wires for patients who expect to have MRI of the head and neck region.

View full abstract

It is well documented that bacteria possessing biofilm phenotype cause persistent infections. Recent studies have indicated that denture plaque can cause not only denture-induced stomatitis, but also systemic infections such as pneumonia and endocarditis. Our previous studies disclosed that exopolysaccharides produced by biofilm-forming bacteria may contribute to pathogenicity. However, little is known about the distribution of these bacteria. In this study, we attempted to isolate and identify biofilm-forming bacteria to understand the proportional distribution of these bacteria in denture plaque. We used scanning electron microscopy to demonstrate the existence of the extracellular matrix materials which are observed as meshwork-like structures around the cells. We found that 42.6% of all isolates from denture plaques showed meshwork-like structures around the cells. We identified these bacteria as Streptococcus salivarius, Streptococcus parasanguis, Streptococcus mitis, Prevotella denticola, Lactobacillus rhamnosus, Streptococcus anginosus and Streptococcus pneumoniae by 16S ribosomal RNA gene sequencing. This study showed that common denture plaque bacteria can form a biofilm on acrylic resin dentures during routine use. These results suggest that denture plaques can act as reservoirs of biofilm-forming bacteria that cause chronic systemic infections.

View full abstract

In order to evaluate how postural changes affect swallowing of liquids, we analyzed simultaneously recorded data of intraoral and pharyngeal pressures during a single, continuous swallowing of water. The subjects were 7 males who had no detectable abnormalities in eating and swallowing function. Intraoral pressure was measured using a microchip pressure transducer in the oral cavity, and pharyngeal pressure was measured by transnasal insertion of a pressure measuring microchip. The head position at which the subject could most easily swallow water through a straw in a single action was defined as the upright position. The positions where the subject was bent forward and backward 30 degrees were defined as the forward and backward inclinations, respectively. We defined a single swallow as sucking and swallowing water through a straw one time. Continuous swallow was defined as repeating the above single swallowing action ten times without rest. We found that postural changes affected how smoothly the water passed from the oral cavity to the pharynx. When we analyzed the early and late stages of swallowing, which were divided at the time of elevation of the larynx, we found that posture affected swallowing in the early stage. However, postural changes did not affect swallowing in the pharyngeal stage, nor did it affect the rhythm or volume of swallowing.

View full abstract

We investigated how water affects the ablation of hydroxyapatite (HAP) by the Er:YAG laser. Ablation of HAP requires that water be both internal and external to the tooth. The wavelength of the Er:YAG laser is 2.94 μm, which almost reachs the absorption spectra peak for water. Therefore, the Er:YAG laser has two characteristics. One is photo-ablation by laser absorbed by water molecules inside and outside the tooth. The other is the photo-thermal effect from heat. We used extracted teeth that had been dried in an electric furnace (dried teeth) and the teeth that had been kept in physiological saline solution immediately after extraction (wet teeth). Quantiative analysis of the moisture content was done by thermal desorption spectroscopy and Karl Fischer's method. Laser irradiation of the enamel and dentin of the test teeth was done with the laser tip 0.1 mm from the dental surface for 1 sec at 3 Hz (3 pulses) and 2 sec at 5 Hz (10 pulses). The pulse width was 10 ns, and the radiation energy was 200 mJ. The external conditions during irradiation were either a spray of light water (normal distilled water), a spray of heavy water, or no spray (air). Light water absorbs photons emitted by the Er:YAG laser, while heavy water does not. Scanning electron micrographs were taken of the ablated tooth surface, and the area and depth of the tested surfaces were measured. We also recorded the number of cracks on the surface of the ablated teeth. We found that water in the tooth affected the ablated enamel to a greater extent than it did the dentin. We also found that the hydroxyl radicals of the HAP increased temperature and contributed to photo-ablation. Permeated external water improved ablation efficiency by supplying water to the dried surface of the ablated tooth.

View full abstract

We analyzed electroencephalograms to investigate whether the frequency of flinching in phase 2 of the formalin test in rat neuropathic pain models is an appropriate index of pain. Electroencephalograms show high-amplitude slow waves at rest, and low-amplitude fast waves in the presence of various stimuli including pain. When an electroencephalogram consists of a fast wave, it is not appropriate to evaluate the reduction of pain-related behaviors as hyposensitivity or pain reduction. We found that the chronic constriction injury (CCI) model showed an electroencephalogram consisting of a fast wave despite the reduction of flinching in phase 2 of the formalin test. After oral administration of indomethacin, an electroencephalogram consisting of a slow wave was detected. We concluded that flinching in phase 2 of the formalin test in the CCI model may not be a useful index of pain.

View full abstract

We investigated the difference between the in vitro expression of human β-defensin-2 (hBD-2) and the production of IL-8 in primary human gingival epithelial cells (HGEC) in response to challenge with various concentrations of IL-1β, which is one of the inflammatory cytokines. mRNA expression of hBD-2 in HGEC stimulated under various conditions was assessed by the semi-quantitative reverse transcription-polymerase chain reaction, and culture supernatants from HGEC after stimulation under various conditions were analyzed quantitatively by enzyme-linked immunosorbant assay. Although the levels of hBD-2 mRNA and IL-8 production in HGEC stimulated with IL-1 β tended to increase with exposure time, the levels were not significantly changed by variations in concentration. These findings suggest that the expression of hBD-2 and IL-8 was observed in IL-1 β-stimulated HGEC regardless of the severity of the inflammation.

View full abstract

We investigated the relationship between occlusal force, mandibular morphology and facial morphology in 60 adults with normal occlusion. We used a non-contact three-dimensional (3D) laser scanner to obtain the 3D facial data. Occlusal force was evaluated using pressure sensitive occlusal sheets. Mandibular morphology was assessed by measuring the Frankfort mandibular plane angle (FMA) on a lateral cephalogram. We found a significant correlation between occlusal force and FMA in both males and females. Occlusal force and FMA also correlated with facial width, vertical position of the chin, and anteroposterior position of the chin. These results suggest that occlusal force and mandibular morphology influence facial morphology in normal occlusion.

View full abstract

We investigated the ultraviolet (UV) light sheltering effect of two esthetics coating materials (ECM), White Coat^<TM> and Beauti Coat. ECM was coated on tetracycline-containing cement which was then irradiated with UV light. The sheltering effect was evaluated by color changes in the cement. Statistical evaluation using Tukey's test showed that both materials significantly decreased transmission rate. We also investigated the marginal leakage between enamel and the ECM using the dye-penetration method. The Mann-Whitney U-test was used to evaluate the marginal leakage would occur after long-term application of ECM. The coated specimens were divided into three groups for examination. The coating was removed after 24 hours in the first group. In the second group the coating was removed after thermal cycling 500 times. For the third group the thermal cycling was done 1500 times. The specimens were then observed by SEM. We found that although exfoliation had occurred at the interface between ECM and enamel, there was no damage to the enamel.

View full abstract

We evaluated the effect of laser irradiation on dentin permeability using an in vitro model of hypersensitive dentin. The lasers used in the experiment were the Erwin AdvErl^[○!R], which is an Er: YAG laser, and the Panalas^[○!R]C 05 Σ, which is a CO_2 laser. Forty dentin discs were prepared from extracted bovine anterior teeth for use as hypersensitivity model samples. The samples were applied to a device made by modifying the one reported by Pashley, with the pulpal pressure fixed at 25 mm Hg. Dentin permeability was measured when the sample surface was irradiated with each laser at a distance of 0 or 1 mm. Statistical analysis was performed by one-way analysis of variance and Scheffes method. We found that laser irradiation decreased dentin permeability, suggesting its efficacy for the treatment of dentin hypersensitivity.

View full abstract

We investigated the effect of molar loss on learning and memory. Five-weeks-old male Sprague-Dawley rats were divided into a tooth extraction group and a control group. At seven weeks of age the animals were subjected to a passive-avoidance task consisting of acquisition and retention trials. Release of hippocampal glutamate was measured during the trials. A telemetric glutamate biosensor was used to measure the release of hippocampal glutamate before and after the start of each trial. Our findings suggest that molar loss may represent one factor hindering learning and memory.

View full abstract

We used electromyography to evaluate the effect of relining removable partial dentures. Electromyograms (EMG) of the bilateral anterior temporalis and masseter muscles were recorded on eight patients together with mandibular kinesiograph (MKG) motions during mastication, tapping and clenching before relining and for two weeks after. The coefficient of variance (CV) for the EMG parameters decreased after relining while EMG bursts during clenching and mastication increased. The results showed that the effectiveness of denture relining was confirmed by electromyography.

View full abstract

We performed an electromyographic analysis of the masseter and temporalis muscles after placement of implant supported mandibular distal extension overdentures. The data obtained was analyzed and compared from seven patients who had mandibular free-end removable partial dentures with and without implant support. We found that posterior support shortened the duration, interval and cycle-time of EMG bursts. In addition, it increased masticatory muscle activity, especially on the working-side masseter muscle, and decreased the coefficient of variation. We concluded that implant support under the free-end saddle electromyographically improved masticatory function.

View full abstract

We attempted to clarify how the mandibular rest position is affected by psychological stress and by relaxation brought about by auditory stimulation. The jaw movements of 10 subjects were recorded with a mandibular kinesiograph (MKG) together with electromyograms (EMG) of the bilateral anterior temporalis and masseter muscles, and electroencephalograms (EEG) at Cz. White noise and relaxation sounds at 90 dB were used as auditory stimulation. We found that compared to the periods of silence or periods of listening to relaxing sounds, when the subjects were exposed to the white noise there was a significant decrease in the interocclusal distance at rest, while there were increases in both the jaw-closing muscle activity and the β wave constituents. We concluded that unpleasant stress, such as white noise, affected the mandibular rest position.

View full abstract

We studied 12 strains of 6 obligate anaerobic Gram-nagative rods (OGNR) isolated from the saliva of adult humans for elucidation of the β-lactam antibiotic-resistant mechanism in odontogenic infectious diseases. DNA polymerase chain reaction (DNA-PCR) sequencing of the OGNR was performed with designed primers and compared with data from the DNA Data Bank of Japan (DDBJ). The PCR products were further induced for gene-transformation in E-coli. A 922-944 bp PCR product showing homology with the known β-lactamase gene was acquired in the specimens sequenced with CfxA 2 primers. Certain PCR products were also observed in other primers. Although all the PCR products were transformed in E-coli, β-lactamase productivity was confirmed only with selective culture media. These results show that the β-lactamase gene is not specific in oral OGNRs. However, although the gene is widely found in oral OGNRs, it is usually not expressed in OGNR strains isolated from areas other than the oral cavity.

View full abstract

Deviation from normal bone resorption may result in bone diseases. Lipid rafts are specialized plasma membrane microdomains enriched with glycosphingolipids, sphingomyelin and cholesterol. In order to investigate the role of lipid rafts in RAW 264 cell signaling, the lipid rafts were disrupted by depleting cholesterol with methyl-β-cyclodextrin (MβCD). We found that receptor activator of nuclear factor κB ligand (RANKL)-induced differentiation into osteoclasts was markedly inhibited by MβCD, which enhanced the phosphorylation of ERK 1/2 MAP kinase. In contrast, MβCD blocked the phosphorylation of IκB kinase. These data suggest a crucial role for cholesterol in the regulation of the RANKL-mediated signaling pathway and osteoclast differentiation in RAW 264 cells.

View full abstract

We investigated immunohistochemical expression of p21^{WAF1 Cip1} (p21) and TGF-β in rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide (4NQO). p21, which inhibits cell proliferation, is induced by the wild type p53 tumor suppressor protein, and by TGF-β. Expression of p21 protein almost disappeared in tongue epithelial cells at 16 weeks after 4NQO administration, while p21 showed overexpression at 24 weeks. TGF-β was found in small amounts at 16 weeks and was expressed strongly at 24 weeks after administration of 4NQ0. These results suggest that the overexpression of p21 at 24 weeks may be induced by TGF-β. Our co-worker previously found that a p53 mutation occurred in the tongue epithelium at 16 weeks using this same model.

View full abstract