This study investigated the possible contributing effect of oral motor function on maximal and explosive grip force production characteristics. Fourteen healthy male subjects (age 22.5±2.1 years) were asked to exert maximal explosive grip strength with their dominant hands under the following four conditions : 1. Teeth clenching before and during grip strength exertion (C-C), 2 . Teeth clenching before grip strength exertion and mandibular resting position during grip strength exertion (C R), 3 . Mandibular resting position before grip strength exertion and teeth clenching during grip strength exertion (R-C), and 4. Mandibular resting position before and during grip strength exertion (R-R) . Maximal force (maxF), average force for every 0.1 s (aveF), maximal rate of force development (maxRFD) and time required to reach 90% of maxF (T 90%max) were analyzed for 1 s from the onset of grip force production. MaxF under C-C and R-C were significantly greater than that under R-R by 12.1% and 12.3%, respectively. AveF under C-C was significantly greater by 10.0-41.2% than that under R-R for all ten periods. AveF under C-R was significantly larger by 9.8-19.0% than that under R-R conditions from 0 to 0.4 s. Compared with under R-R conditions, maxRFD under C-C and C-R increased by 15.8% and 8.5%, respectively, and T 90%max under C-C, C-R and R-C decreased by 22.3%, 12.3% and 12.8%, respectively. These findings suggest that oral motor functions such as teeth clenching may influence not only maximal grip strength generation but also the rapidity of grip force production.
In the developing tooth, 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) causes hypoplasia and hypomineralization of enamel and dentine. The present study was undertaken to clarify the effects of HEBP on the formation of dental tissues of tooth germs in an organ culture system. Mandibular first molars from 17.5-day-old mouse embryos were cultured with or without 250μM HEBP in culture medium. Cultured tooth germs were analyzed by histological examination and by immunohistochemical localization using anti-amelogenin antibody. In cultured tooth germs treated with HEBP before the commencement of calcification in dentine, calcification of dentine matrix was inhibited completely and enamel formation was not observed. Ameloblasts were directly adjacent to dentine matrix. However, immunohistochemical data indicated that these ameloblasts secreted amelogenin. In the experiments of adding HEBP to cultured tooth germs on culture day 13, calcified dentine and enamel had formed before the administration of HEBP, but the dentine matrix newly formed after the administration of HEBP had not calcified. It was confirmed by immunohistochemical observations that enamel matrix-like material had penetrated into uncalcified dentine matrix and accumulated in dental papilla of tooth germs. However, no enamel matrix-like material was observed in calcified dentine and predentine underneath the calcified dentine by immunohistochemical staining. From these results, it might be concluded that ameloblasts secreted enamel matrix in the presence of HEBP and diffused through uncalcified dentine matrix into dental papilla. These findings suggest the calcification of dentine might be essential for the physical barrier to accumulate the enamel matrix and form a distinct layer of enamel as enamel.
This study investigated the effect on the vibratory characteristics of a Class I Kennedy maxillary removable partial denture when varying its major connector design. Three types of major connector were used : the U-shaped palatal connector type (UPCD), the single palatal bar type (SPBD), and the anteriorposterior palatal bars type (APBD) . Three types of denture were excited by a shaker, and frequency response functions were recorded on an FFT analyzer to identify their modal shapes. In addition, transient response simulations were carried out and the maximum displacement of each denture was obtained. The maximum displacements were statistically analyzed by ANOVA and Scheffe's F test (p<0.01) . In the modal shapes of SPBD, there were no nodal points on the major connector at all natural modes. The maximum displacement of SPBD was significantly smaller than that of UPCD and APBD. This study indicated that SPBD was a more rigid design than UPCD and APBD from the standpoint of vibratory characteristics.
Tetragonal zirconia polycrystals stabilized with 3 mol-% yttria (TZP) exhibit good mechanical properties, favorable esthetic appearance and translucency. Despite this, zirconia has not been widely used for all-ceramic restorations due to the difficulty of shaping it. A new process called the cercon smart ceramics® system overcomes this limitation by milling ceramic blanks in a porous, presintered and yet easily machinable state which are afterwards sintered to full density. The sintering shrinkage is compensated for by enlarging the shape prior to machining. Not only the fracture resistance but also the marginal fitness are important for all-ceramic restorations to produce satisfactory results. In this comparative in vitro study, the marginal fitness of TZP all-ceramic crowns and fixed partial dentures (FPDs) were examined. The marginal discrepancies of the FPDs (29.3μm) were not significantly different from those of the crowns (31.3μm) . The results of this work suggest that 1) The marginal fitness of all-ceramic restorations fabricated by the Cercon® system was satisfactory for clinical use. 2) The dimensional stability of the Cercon® substructure was maintained during firing of the porcelain and successive glazing.
This study explored the relationship between the function of the autonomic nervous system (ANS) and glossodynia. The function of the ANS was examined in patients with glossodynia by frequency analysis of heart rate variability. The subjects were 50 women given the diagnosis of glossodynia and 24 healthy volunteers. The heart rate variability of these subjects was evaluated. Mean values of the high frequency power at rest were 1, 323 ± 1, 484 ms2 in the group without functional disorders (NF group), 1, 861±1, 601 ms2 in the group with functional disorders (F group), and 3, 229±2, 044 ms2 in the standard group (H group) . Mean values of HF/LF were 0.968±0.961 in the NF group, and 1.696±0.847 in the H group. Mean values of the high frequency power at rest were 1, 032±977 ms2 in the group with CMIs in regions III and IV (III-IV group), 3, 299±2, 044 ms2 in the H group, and 2, 314±1, 883 ms2 in the group with CMIs in regions I and II (I-II group) . Mean values of HF/LF were 0.965±0.744 in the III-IV group and 1, 696±0.847 in the H group. The results of this study suggest that nervous tension, which was the cause of indefinite complaints in patients with glossodynia, had resulted from a pronounced reduction in activities of the parasympathetic nervous system, but not from an excessive increase in activities of the sympathetic nervous system. An assessment of the function of the ANS by means of heart rate variability seemed to be useful for comprehending the clinical conditions of glossodynia.
Terminally differentiated neurons irreversibly withdraw from the cell cycle. The mechanisms governing the activity of cyclin D 1, a key regulator of the cell cycle, during neuronal cell cycle withdrawal are not fully understood. This study shows that cyclin D 1 became predominantly cytoplasmic in differentiated cortical neurons. Cytoplasmic cyclin D 1 assembled with cyclin dependent kinase 4 (CDK 4), and the CDK inhibitors p 21Cip1 and p 27Kip1. Although forced expression of p 21 caused cyclin D 1 nuclear accumulation, the inhibition of its nuclear export by inhibiting GSK-3 β activity had no effect. Furthermore, ectopically expressed cyclin D 1 entered the nucleus of proliferating nervous, but not that of differentiated neurons, whereas ectopic cyclin D 1 in quiescent fibroblasts accumulated in the nucleus and induced cell cycle progression. These results indicate that cyclin D 1 nuclear localization is tightly inhibited in terminally differentiated neurons, and suggest that the regulation of its nuclear import plays a role in neuronal cell cycle withdrawal.