This study was conducted to improve protection of the abutment tooth by modifying the inner crown form in an electroformed telescope crown. Inner crowns with a 0°, 2° and a combination taper (0° taper for the cervical 1.5mm and 2° taper above that) were made of gold alloy, and five outer crowns were made by electroforming on the inner crowns. We measured the retentive force and the negative pressure generated between the inner and outer crowns with 60% glycerin solution substituted for saliva. The peak retentive forces for the inner crowns with the 0° taper and for the combination crowns were greater than those for the 2° tapered crowns. There was no difference between the 0° taper crowns and the combination taper crowns. There were also no differences among the three types for the maximum negative pressure. The distances before the generation of peak retentive force and maximum negative pressure were significantly greater for 0° than for the other tapers. The retentive force generating distance at 0° was significantly greater for the 2° and combination tapers. A 0° electroformed telescope required significantly greater retentive energy for removal than either the 2° or combination taper. We concluded that the combination taper, which had an improved inner crown, helped reduce the retentive energy imparted on the abutment tooth without reducing the retentive force, and could be used as an effective retainer for protection of the abutment teeth.

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All-ceramic restorations have the advantage of being esthetic. All-ceramic core materials of alumina and zirconia have high in vitro strength. The translucency of dental porcelain is largely dependent on light scattering. I compared the translucency and contrast ratio of two different all-ceramic system core materials at clinically appropriate thicknesses. The translucency and contrast ratio of all-ceramic core materials were measured in single and laminated specimens consisting of core material and porcelains. For the laminations used in this study, there were no significant differences in the translucency and contrast ratio of the two core materials examined. However, significant differences were noted in the translucency and contrast ratio among various combinations of core materials and laminate specimens.

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Magnetic resonance imaging (MRI) often produces artifacts as a result of the mechanism of image construction. They include disappearance and distortion of the image caused by substances existing in and around the subject. We examined the effects of multibracket appliances for orthodontic treatment on MRI using various combinations of materials. Three types of MRI sequences, which are often employed in maxillofacial and craniofacial examinations, were used for this study with a 1.5 Tesla MRI. The range of impairment in each image was measured, and the following results were obtained. In the Spin Echo T1 weighted (SE T1) images, Fast Gradient Echo T2 weighted (FGR T2) images and fluid attenuated inversion recovery (FLAIR) images, we observed the largest impairment with orthodontic appliances that had metal brackets, archwire bent keyhole loops, ligature wires and a palatal bar. The smallest impairments were observed in images with ceramic brackets, archwire bent L-loops, elastic ligatures and no palatal bar. Currently, most orthodontic appliances use metal brackets and stainless-steel wires. Therefore multibracket appliances become a factor for artifacts with MRI. These results suggest that we must take into consideration the type of materials and shape of arch-wires when doing MRI and be aware of the possibility for artifacts in images of the maxillofacial area of patients with multibracket appliances.

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Establishing and maintaining stable occlusion is one of the most important challenges in orthodontic treatment. We investigated the correlation between centric occlusion and the temporomandibular joint (TMJ). Thirty-four male adult volunteers were enrolled in this study, presenting normal occlusion without subjective symptoms of TMJ disorders or any other abnormality in jaw function or masseter muscles. For occlusal force measurements, occlusal balance was determined by calculating the sum of the product of the area and the pressure at each occlusal contact on both sides of the mouth. A dynamic MRI was used for measurement of the TMJ space. The subjects were asked to achieve the maximum voluntary contraction (MVC) for 10 minutes and a set of 20 magnetic resonance images (MRI) were exposed on each side. The joint space dimensions were then measured on the images using image analysis software. We next investigated the relationship between occlusal balance and joint space dimension. In the group with greater occlusal force on the right side, the joint space dimension at the glenoid fossa (90°) on the left side showed a significant reduction during MVC, whereas in the bilateral equilibrium group the joint space dimension at the glenoid fossa (90°) on both sides showed a significant reduction (p<0.05). In the group with greater occlusal force on the left side, the joint space dimensions at the tuberculum articulare (45°) on the left side and at the glenoid fossa (90°) on the right side showed a significant reduction during MVC, whereas the joint space dimension at the glenoid fossa (90°) on the left side showed a significant increase (p<0.05). These findings indicate that poor balance between occlusal forces on the right and left sides can influence the TMJ. The findings also show the importance of balancing occlusal force in orthodontic treatment.

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Advances in CAD/CAM systems have made it possible to process a homogeneous framework of zirconia which has excellent mechanical strength. Development of porcelain with a thermal expansion coefficient similar to zirconia has made it possible to fuse the two materials. I compared the shear bond strength of porcelain fused to zirconia with that of porcelain fused to metal frameworks. Zirconia cylinder specimens were milled 3mm in diameter and 10mm long. The upper portion of the specimens was airborne-particle abraded with 50μm or 100μm aluminum oxide particles to a circumference of less than 2mm. Opaque and dentin porcelain were applied to 1.5mm thickness using a mold. Porcelain was also bonded to a metal ceramic gold casting alloy, a Ni-Cr casting alloy, and milled pure titanium, respectively. Eight specimens were fabricated for each metal in the same manner as for the zirconia specimens. The specimens were subjected to shear bond testing in an apparatus mounted in a universal testing machine, with a cross-head speed of 0.5mm/min. The measurement data were analyzed by one-way ANOVA, and fracture surfaces were observed with Scanning electron microscopy and energy dispersive X-ray spectroscopy. The mean shear bond strengths were 31.5±5.3MPa for zirconia (50μm particles), 27.1±7.5MPa for zirconia (100μm particles), 32.1±2.3MPa for gold casting alloy, 28.2±4.2MPa for Ni-Cr alloy, and 24.5±6.2MPa for milled pure titanium. The bond strength of zirconia (50μm particles) was significantly greater than that of Ni-Cr alloy. There was no significant difference in the shear bond strength between zirconia ceramics and ceramics fused to casting gold alloys. The surface roughness of zirconia had little effect on bond strength. The reasons for failure of zirconia ceramic differed greatly from those of metal ceramic. There results suggest that zirconia ceramic restorations can be both biocompatibile and esthetic.

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c-Met is the receptor of hepatocyte growth factor and is linked to metastasis and proliferation of cancer. β-eaten in is a protein that binds to the cytoplasmic tail of cadherins and has an essential role in intercellular adhesion and signal transduction. We examined the expressions of c-Met and β-catenin in oral squamous cell carcinomas (OSCC) by immunohistochemical staining. Thirty tissue specimens each for the cervical lymph node metastasis group (N(+)) and for the no lymph node metastasis group (N(-)) were obtained from the Osaka Dental University Hospital. We also investigated the T category and the clinical stage of OSCC. Of 30 N(+) cases, three (10%) had negative reactions and 27 (90%) were positive to c-Met. Of 30 N(-) cases, 14 (47%) had negative reactions and 16 (53%) were positive to c-Met. We found that c-Met overexpression was greater in N(+) than in N(-), greater in advanced T categories than in early T categories, and greater in the advanced clinical stages than in early clinical stages. Reduced β-catenin expression was also observed in the N(+) group. There were statistically significant differences in the expression of c-Met between N(+) and N(-), for the different T categories, and for the different clinical stages. We found the expressions of c-Met and β-catenin were independent prognostic factors. These results suggest that the expressions of c-Met and β-catenin may be effective in screening OSCC with N(+).

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Burning mouth syndrome (BMS) is a chronic pain syndrome that mainly affects middleaged and elderly women with hormonal changes or psychological disorders. Saliva can be gathered more non-invasively than other body fluids. We measured the anxiety and depression levels of BMS patients and healthy individuals using the Hospital Anxiety Depression Scale (HADS) and the Self-Rating Depression Scale (SDS), and compared changes of salivary cortisol and chromo-granin A (CgA) in both groups. The subjects were ten healthy persons and nine BMS patients. Immediately and 30 minutes after administering the tests, changes in salivary cortisol and CgA were recorded. All tests were repeated on the following day. The HADS and SDS levels in BMS patients were significantly greater than in healthy persons. Salivary cortisol was significantly elevated in the healthy group, but not in the BMS patients. None of the subjects showed significant change in salivary CgA. We concluded that BMS patients were more influenced by psychological stress than healthy persons, as reflected in their salivary cortisol levels.

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Botulinum toxin (BoNT) disrupts neurotransmitter release from cholinergic nerves. We investigated whether temporary acinar atrophy occurs simultaneously with chemical denervation of the glands. Male Wistar rats weighing 250-300g were used. Intraductal injection of BoNT induced a transient denervation of the submandibular gland, which is associated with reduced salivary secretion. Morphological and ultra structural analyses of the cell organelles and secretory granules showed a clear atrophy of the acini, which was more prominent in glands treated with BoNT. Morphometric measurements of the glandular acini revealed a significant reduction in the area of the acinar cells after BoNT treatment. The expression of amylase was significantly reduced in BoNT treated glands. Intraductal injection of BoNT induced structural and functional changes in the salivary glands, which was indicated by glandular atrophy. These effects may be the results of glandular denervation induced by the inhibition of the soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors (SNAREs) involved in acetylcholine release at the neuro-glandular junction, and especially the results of the inhibition of the cells involved in exocytosis of the acinar cell granules.

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Hyperplasia of the tendon and aponeurosis of masticatory muscles (HyTAM) is a new disease entity characterized by chronic severe mandibular hypomobility with a square mandible caused by contracture of the masticatory muscles resulting from hyperplasia of tendons and aponeuroses. We investigated the skeletal features of HyTAM using cephalometric analysis. Angular analysis showed that the gonial angle (p<0.01), FMA (p<0.05), cant of the occlusal plane (p<0.01) and Y-axis (p<0.001) were significantly less than the standard values. The saddle angle (p<0.05) and facial angle (p<0.001) were significantly greater than the standard values. Linear analysis showed that S-Go/N-Me was significantly less than the standard value (p<0.05). The typical patient with HyTAM is characterized by a square mandibular configuration. Based on our findings, it is reasonable to suppose that HyTAM is marked by a lower gonial angle. Our findings also indicated that HyTAM patients not only showed hyperplasia of the tendon and aponeurosis of masticatory muscles, but also had unique facial skeletal appearances such as jaw deformity.

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We examined the inhibitory effect of Gypenoside (GP), Baicalia (BC), Salvia miltiorrhiza (SM), and Erigeron breviscapus (EB) to determine whether Chinese herbal medicines are effective against oral cancer. Phenazine methosulfate-methyl thiazoly tetrazolium (PMSMTT) assay was performed on the oral squamous cancer cell lines Tca-8113 and CAL-27. The ID 50 of the four Chinese herbal medicines was calculated. We found that BC and EB were the most effective. The ID 50 values for Tca-8113 and CAL-27 of BC were 128.63μmol/L and 117.79μmol/L, respectively. They were 223.18μmol/L and 1010.98μmol/L, respectively for EB. The ID 50 for the combined effect of BC and EB, was 27.131μmol/L for Tca-8113 and 20.674μmol/L for CAL-27. Thus BC and EB had a synergistic effect in inhibiting Tca-8113 and CAL-27 (CI<1).

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It has been reported that there are differences in the prevalence of deciduous caries among the different regions of Japan. These differences have been explained by socioeconomic factors in each region. However, there has been no analysis using data from the past decade, even though the socioeconomic situation of these regions has been changing during that time. We investigated the relationship between dental caries prevalence in Japanese 3-year-olds and socioeconomic status in 1995, 2000 and 2005. The data used in this study were collected at the prefectural level. Dental caries maps for 3-year-olds in each prefectures in 1995, 2000 and 2005 were drawn based on the data from annual dental health check-ups. Multiple linear regressions analysis was conducted with the average number of decayed, missing and filled deciduous teeth (dmft) as the dependent variable, and socioeconomic status as the independent variable. The dmft for 3-year-olds decreased between 1995 and 2005, and regional variations in the prevalence of dental caries among the prefectures decreased every year. Multiple linear regression analysis showed that the dmft of 3-year-olds was significantly associated with proportion of workers in the primary sector, the average size of the household, the unemployment rate, and the number of nursery schools per million children under 4 years of age (p<0.05, R^2=0.598). In 2000 the dmft for 3-year-olds significantly correlated with the proportion of workers in the primary sector, the average size of the household, the unemployment rate, and the amount of family savings (p<0.05, R^2=0.712). In 2005 the dmft for 3-year-olds significantly correlated with the amount of family savings, the proportion of household budget spent on education, the proportion of workers in the primary sector, the number of nursery schools per million children under 4 years of age, and the number of dental offices per 100,000 people (p<0.05, R^2=0.706). Factors related to dental caries in 3-year-olds changed from factors relating to industrialization to factors relating to stability of life. The reasons for this change might be explained by changes in life-styles and the reduction in dental caries. In 2005 it was found that factors associated with dental services affected dental caries in 3-year-olds. Our findings suggest that it is necessary to consider socioeconomic status when planning public health policy for dental caries prevention.

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