We examined the effect on dissolution and cell viability of dynamic extraction with similar and dissimilar combinations of type 3 gold alloy (AU), gold-silver-palladium alloy (PD), and silver-indium alloy (AG). Of the six constituent elements that we measured in the alloys, Cu and Zn were selectively dissolved from the materials containing AU and/or PD. They were found in filtrates in the same amount as in extracts. A slight amount of gold and palladium was detected only in the extracts. However, silver and indium were mainly detected in extracts of combinations of AG. They were not found in the filtrates. For the similar and dissimilar combinations of AU and PD, there were only slight differences in cell viability between the extracts and filtrates. Cell viability of extracts was lower in the dissimilar combination of AG than in the similar combinations of AG. Moreover, filtrates exerted less effect on cell viability than did the extracts. The increased dissolution associated with an increase in extraction time further depressed cell viability. These findings indicate that dynamic contact between two alloys may affect dissolution and cytotoxicity of metallic biomaterials used in stress-bearing restorations.

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Using 53 paired dental casts, we determined midpoints of the incisal ridge of the incisors (l1_R, l1_L, l2_R & l2_L), cusp tips of the canines (C_R & C_L), summits of buccal cusps of the premolars (P1_R, P1_L, P2_R & P2_L), summits of mesiobuccal cusps of the molars (M1_R, M1_L, M2_R & M2_L) and the midpoint A of line (l1_R-l1_L). Point B is defined as the intersection of the vertical line from point A with the line (M2_R-M2_L). Point E is the intersection of (A-B) with (C_R-C_L). The midpoint of line (M2_R-M2_L) is defined as point O. We also determined the relation of the contour and position of line (P1-P2-M1-M2) to line (P1-M2). We observed significant differences between round V-shaped arches and the other arch types by evaluating the curvature of anterior teeth and the degree of roundness of the arch. Six selected items were summarized into three principal components. The first principal component showed the curvature of anterior teeth, the second principal component represented the curvilin-ear contour of the dental arch, and the third principal component indicated the length-to-width ratio of the dental arch. We found that the first and second principal components were essential in classification of mandibular dental arches.

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We investigated reproducibility of measurements of occlusal contact area obtained with the T-Scan II, which is an occlusal examination device. The subjects were ten males with healthy, complete dentition. We measured the occlusal contact area at the five levels for 25, 50, 75, 90, and 100% maximum voluntary contraction (MVC). Five repetitions were made for each measurement over two days. Reproducibility of the occlusal contact area measurements was evaluated by the single-factor repeated measures analysis of variance, the standard error of measurement and the intraclass correlation coefficient. The most stable measurements were obtained from the second and third clenching tests. The reliability for same-day measurements was higher than that for different-day measurements. In the same-day measurements, the reliability at 25% and 50% MVC was lower than that at the three other clenching levels. For different-day measurements, the reliability for all clenching levels was essentially the same. The average measurements showed better clinical reliability than did single measurements for the same-day and different-day measurements. We found reproducibility for the same-day and different-day measurements of occlusal contact area with the T-Scan II.

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We investigated the influence of vibratory stimuli on motor evoked potentials (MEPs) in masseter muscles using transcranial magnetic stimulation. A double cone coil driven by a Magstim Model 200 magnetic stimulator was placed on the skull overlaying the right temporal area. The stimulus intensity was set to 50% of maximum output. As a control, we measured the MEP at 50% of maximum clenching before vibratory stimuli. We instructed five volunteers to clench at 50% maximum contraction every 15 seconds for 2 minutes after application of 120Hz vibratory stimuli to the mentalis for 20 seconds. Magnetic stimulation was applied during clenching. Latency and amplitude were measured for the MEP on the ipsilateral side (R-MEP) and contralateral side (C-MEP). We found that the latency of both MEPs remained unchanged after application of vibratory stimuli. The amplitude of R-MEPs decreased compared with the controls, while C-MEPs increased. A significant difference was observed between the R-MEPs and C-MEPs. These findings indicate that vibratory stimuli enhance excitability in the motor cortex.

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We investigated the effect of photocatalytic reactions of titanium dioxide fine powder on rat tongue carcinoma cells induced by 4-nitroquinoline 1-oxide. Three types of titanium dioxide fine powder, anatase type ST-41, rutile type TP-3 and mixed type P-25, were added separately to culture fluid for 48 hours, followed by exposure to 254nm ultraviolet light. The cell survival rate was decreased in the cells cultured with any type of titanium dioxide fine powder, and the decrease was marked in the cells cultured with ST-41. Furthermore, the cell survival rate was decreased in correlation with irradiation time and concentration in the ST-41 group. We found an apoptotic ladder pattern which suggests that the apoptosis was associated with the mechanism of cultured cell kill. These findings indicate that the photocatalytic reactions of ST-41 titanium dioxide fine powder may provide a new modality of cancer treatment.

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Mastication is generally done on the habitual masticatory side. It is assumed that masticatory function and maxillofacial morphology influence each other. We examined the relationship between maxillofacial morphology and masseter muscle morphology on the habitual masticatory side. We determined volume and inclination of the masseter muscle of 22 adult males with normal occlusion using three-dimensional reconstructed MRI images. Outlines of the masseter muscles were traced and reconstructed three dimensionally on a personal computer, and the inclination and volume of each muscle were determined from this data. Postero-anterior cephalograms were used to observe maxillofacial morphologies. We did logistic regression analysis on the measured indexes and examined now the craniofacial morphology related to the habitual masticatory side. We found that the habitual masticatory side was closely related to both masseter muscle morphology, and morphology of the lower face.

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When all or part of the tongue has become enlarged, regardless of the reason, it is called macroglossia. We did a tongue reduction on a 58 years-old woman who had the habit of chewing the edge of her tongue. Voice analysis using the Sugi speech analyzer before and after the operation showed no significant change in the patient's articulation.

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I examined the influence of aquaporin 5 (AQP 5) on paracellular water transport in submandibular gland acini using male Wistar rats weighing 250-280g. In unstimulated cells, immunoelectron staining detected AQP 5 on the luminal membrane, and ZO-1 on the lateral membrane. After parasympathetic stimulation, both AQP 5 and ZO-1 were distributed on the luminal membrane, lateral membrane and secretory granules. AQP 5 treatment of the lateral membrane increased tight junctional permeability. Because water-rich fluid was secreted in the lumen of the acinar cells where AQP 5 and ZO-1 were both abundantly present, it is reasonable to speculate that both intercellular and intracellular transport play important roles in water secretion.

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Bisphosphonates (BPs), synthetic analogs of pyrophosphate, are potent inhibitors of bone resorption and are being successfully used with increasing frequency in the treatment of osteoporosis. We investigated whether BPs (etidronate, alendronate and risedronate) affect the proliferation and mRNA expression of type l collagen, osteocalcin and alkalinephosphatase on human osteoblast-like Saos 2 cells. When alendronate and risedronate were co-cultured with Saos-2 cells, proliferation decreased compared both with the controls and with Saos-2 cells cultured with etidoronate. The mRNA expression was analyzed using a reverse trancriptase-polymerase chain reaction. The expression of mRNA, type l collagen, osteocalcin and alkalinephosphatase were decreased by treatment with alendronate and rise-dronate, but not by treatment with etidronate. These results indicate that N-BPs may influence the activity of osteoblasts, not but non-N-BPs.

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Although human papillomavirus (HPV) infection has been shown to be a significant carcinogen in cervical squamous cell carcinoma (SCC), its significance in oral SCC remains unclear. We developed highly sensitive detection methods for HPV to elucidate the prevalence and localization of HPV in paraffin sections from human oral SCC using modified in situ PCR and in situ hybridization AT tailing (ISH-AT). Analyses revealed a high prevalence of several HPV types (HPV-16, 18, 22, 38 and 70) under optimal conditions. The ISH-AT method can be used as an alternative to in situ PCR. Various staining patterns were observed in the 20 cases and HPV-positive cells were localized within the surface epithelium as well as in neoplastic cells. We demonstrated that HPV DNA could be detected in paraffin sections using either the method of in situ PCR or ISH, providing an appropriate primer and probe are used.

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We investigated the influence of vibratory stimuli on motor evoked potentials (MEPs) in masseter muscles using transcranial magnetic stimulation. MEPs were measured every 15 seconds for 2 minutes after application of 120Hz vibratory stimuli to the mentalis for 20 seconds in five volunteers. Latency and amplitude were measured for R-MEPs on the ipsilateral side and C-MEPs on the contralateral. After application of vibratory stimuli, the amplitude of R-MEPs decreased compared with the controls, while C-MEPs increased. A significant difference was observed between R-MEPs and C-MEPs. These findings indicate that vibratory stimuli enhance excitability in the motor cortex.

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We investigated reproducibility of measurements of occlusal contact area obtained with the T-Scan II system, which is an occlusal examination device. We measured the occlusal contact area at the five levels for 25, 50, 75, 90, and 100% maximum voluntary contraction (MVC). Five repetitions were made for each measurement over two days. Reproducibility of the occlusal contact area measurements was evaluated by intraclass correlation and by the standard error of measurement. The most stable measurements were obtained from the second and third clenching tests. We found reproducibility for within-day and between-days measurements of the occlusal contact area.

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We did clinical examinations to compare shortened dental arches (SDA) and complete dental arches (CDA). The parameters evaluated were occlusal contact area of the mandibular premolars, the center of force, occlusion time, masticatory ability and contact points. We found that there was a difference between SDA and CDA, and that SDA was inferior. It is recommended that more clinical data be collected on SDA.

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We examined the biofilm forming capacity of 74 clinical isolates of black-pigmented Gram-negative anaerobic rods isolated from periodontal lesions. Two strains (OD 1-2 and OD 1-16) were obtained and identified as Prevotell intermedia (P. intermedia). Exopolysaccharide (EPS) from strain OD 1-16 cultures consisted primarily of polysaccharide that was 62% mannose. Compared to the non-EPS-producing strain, ATCC 25611, strain OD 1-16 had a higher capacity to induce abscess formation in mice. Our results suggest that P. intermedia can produce large amounts of exopolysaccharide, form biofilm, and play an important role in the development of biofilm infections in the oral cavity.

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We isolated a spore-forming Gram-positive aerobic rod from a persistent periapical lesion that was identified as Bacillus subtilis using an API system, 16 S rRNA sequencing, and DNA-DNA hybridization. We named it B. subtilis strain N 38. Scanning electron microscopy revealed that this strain had dense mesh-like structures on the cell surface, which is typical of biofilm-forming bacteria. Several genes, previously reported as crucial factors for biofilm formation in B. subtilis, were detected by the polymerase chain reaction method. Compared with the ATCC 6051, which is a type strain of B. subtilis, the susceptibility of strain N 38 to anti-microbial agents did not show a particular pattern. Our data suggest that biofilm-forming B. subtilis can cause persistent periapical periodontitis.

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