Purpose: To investigate the effects of titanium (Ti) ions on the cell viability, the cell differentiation and the gene expressions related to bone resorption including Receptor Activator of NF-kB Ligand (RANKL) and Osteoprotegerin (OPG) in the tissues around dental implants, the osteoblast-, osteoclast-, and gingival epithelial-like cells were exposed to Ti ions.
Methods: An MTS assay was carried out to evaluate the viabilities of osteoblast-like MC3T3-E1, osteoclast-like RAW264.7 and epithelial cell-like GE-1 cells. The gene expressions in these cells were analyzed by the use of RT-PCR and real-time quantitative RT-PCR.
Results: Ti ions in the concentration range 1-9 ppm had little effect on the viabilities of MC3T3-E1, RAW264.7 and GE-1, whereas 20 ppm Ti ions significantly decreased the viabilities of all cells. Analyses of RT-PCR and real-time quantitative RT-PCR data revealed that Ti ions at 9 ppm remarkably inhibited the expressions of Runx2, Osterix and type I collagen in MC3T3-E1. In RAW264.7, Ti ions showed no effects on the levels of mRNAs for TRAP and cathepsin K enhanced by RANKL. Ti ions at the range of 1-9 ppm showed no effects on the levels of mRNAs for RANKL and OPG in GE-1, while Ti ions at 9 ppm enhanced the expression of these genes in MC3T3-E1.
Conclusions: These results, taken together, suggested that Ti ions show the biological effects, both on the viabilities of osteoblast and osteoclast and on the differentiation of either the osteoblastic or osteoclastic cells, which may influence the prognosis of dental implants.

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Purpose: Subjective speech evaluation is important in maxillofacial rehabilitation. In previous research, the automatic speech intelligibility test system using monosyllables was developed using a computerized speech recognition technique, and it was suggested that the system may effectively be used in evaluated maxillectomy patients' speech. However the system showed some disadvantages such as the low sensitiveness for the mild speech disorders. In this study, the system was remodeled employing sentences as test stimuli to overcome the shortcomings. The new system was used to evaluate speech of normal adults and maxillectomy patients.
Methods: The speech of 10 normal adults and 13 maxillectomy patients was evaluated using the automatic conversation intelligibility test system that employed sentences as test stimuli. Normal subjects repeated the test for three times on different days. The patients' utterances were examined in two conditions: with and without prostheses. The results from patients with and without prostheses were compared to each other, and also compared with their corresponding conversation intelligibility obtained using a perceptual method.
Results: In normal subjects, there was no significant difference in their scores using the automatic conversation intelligibility test on three different days. The result of the automatic test was significantly improved in patients by wearing prostheses. There were significant correlations between the result of the automatic test and the corresponding conversation intelligibility both in patients with prostheses and without prostheses.
Conclusion: It was indicated that the automatic conversation intelligibility test system using sentences as stimuli would be effectively used in evaluating maxillectomy patients' speech.

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Purpose: This study aimed to clarify the role of the artificial tooth arch (ATA) during swallowing in edentates.
Methods: The tongue pressures, activities of the masseter and suprahyoid muscles, and laryngeal and mandibular movements when swallowing saliva, water, pudding, and corned beef were measured simultaneously using experimental dentures with and without an ATA. We analysed the maximum magnitudes of muscle activities and tongue pressures (MAmax and TPmax, respectively), the times from reaching MAmax and TPmax to laryngeal movement (TLM-MAmax and TLM-TPmax, respectively), and the vertical mandibular position. Results: The MAmax of the masseter muscle and TPmax were significantly greater with the ATA than without the ATA ( p < 0.05). However, MAmax of the suprahyoid muscles was not significantly different in the conditions with and without the ATA.
TLM-TPmax was significantly longer without the ATA than with the ATA ( p < 0.05) but the TLM-MAmax of the suprahyoid and masseter muscles were not significantly different with and without the ATA. The MAmax of both suprahyoid and masseter muscles and the TPmax were significantly greater, and TLM-TPmax was significantly longer when swallowing corned beef than other materials ( p < 0.05).
The intermaxillar distance and the range of measured mandibular position at the time of swallowing were shorter and wider in the absence of the ATA than with it.
Conclusion: The present study shows that during swallowing the ATA supports the function of the tongue to perform skillful movements for the smooth passage of food to the oropharynx and the elevation of the larynx by maintaining the mandible position constant near the intercuspal position.

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Purpose: The objective of this study was to confirm the validity of a Self-Implementable method to evaluate masticatory performance using a newly developed color scale and color-changeable chewing gum.
Methods: We developed a dedicated color scale that enables anyone to easily check the color of the chewing gum instead of using specialist equipment. To examine the reliability of evaluating the masticatory performance by the subjects themselves, three groups of six subjects were recruited: a group of dentists, a group of adults and a group of elderly adults were asked to check the colors of the chewed samples using the color scale. The correlation between the use of the color scale and the use of a colorimeter to determine the color of the chewing gum was studied to confirm the validity of the color scale. To assess the reliability, intraclass correlation coefficients (ICCs) were determined.
Results: A strong correlation was found between the a* value measured by the colorimeter and the mean scores from the color scale. The ICCs for intra-examiner and inter-examiner consistency were more than 0.88 for all three groups.
Conclusions: This research confirmed the validity and reliability of colorimetric analysis of color-changeable chewing gum using a color scale as a Self-Implementable method of evaluating masticatory performance.

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Purpose: This study aimed to clarify the relation between the shape of the retainers and the plaque formation on abutment teeth to improve the denture design.
Methods: This study observed the buccal surface for the clasps and distoproximal surface for a guide plate of the mandibular first premolar which was the abutment tooth with a direct retainer of a distal extension RPD. The buccal surface was observed in 10 subjects and the distoproximal surface in 14 subjects. The latter cohort was divided into two groups (the group with an open type guide plane and a close type guide plane). All subjects provided their informed consent. The state of plaque accumulation was inspected by standardized photography and bacterial quantification and compared among the cast circumferential (CC), Ibar, wire circumferential (WC) and control (no clasps) in individuals regarding the buccal surface and between the groups with the open type and close type guide plane of the distoproximal surface.
Results: No significant differences were observed among the CC, Ibar, WC and control (P > 0.05) regarding the buccal surface, while in regard to the distoproximal surface, the group with the open type guide plane had significantly more plaque than the group with the close type guide plane (P < 0.05).
Conclusion: The plaque formation on the buccal surface is not dependent on the types of clasps. It is effective to prepare a guide plane as close to the gingival margin as possible to reduce the plaque accumulation on the distoproximal surface.

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Purpose: To examine gene expression profile changes in the mouse masseter muscle tissue after repetitive electrical stimulation by using a DNA microarray technique.
Methods: Nine male ICR mice aged 10 weeks were used. Each anesthetized mouse was secured on a platform in a supine position and the masseter muscle tissues on both sides were exposed. Bipolar electrodes were set on the right masseteric fascia to electrically stimulate the masseter muscle (8 V, 10 Hz, 20 ms) for 30 min. After cessation of stimulation bilateral masseter muscle tissues were sampled at 0 h (n = 3),1h(n = 3), 2 h (n = 3). TotalRNAwas isolated fromthe homogenized muscle tissuesand purified mRNAsamples (50 mg) were processed and hybridized with microarray slides. Probe arrays were then scanned and analyzed to calculate the signal density. Gene expression profiles were compared at each time point between the right (stimulation side) and left (control side) masseter. When the gene expression levels were different more than 2-fold, the difference was regarded as positive.
Results: Of the 6400 genes assessed, 1733 genes were up-regulated and 515 genes were down-regulated in the stimulation side at least once during the experimental time course. These up-or down-regulated genes were associated with autoimmune/inflammatory disease (28/114), cardiovascular disease (17/61), neuroscience (12/50), apoptosis (27/93), diabetes/obesity (9/28), signal transduction (66/250) and others. 28 genes were up-regulated and 25 genes were down-regulated at all time points.
Conclusions: Dramatic gene expression changes were induced by the repetitive electrical muscle stimulation in mouse masseter.

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Purpose: To investigate the influence of wearing complete dentures on postural control in standing and walking.
Methods: Thirty-four edentulous patients participated in this study. All the subjects were wearing complete dentures, and the dentures were adjusted or replaced with new dentures when necessary. Measurements were performed under two conditions: wearing dentures and not wearing dentures. Standing stability was evaluated by the locus of center of mass, and gait stability was evaluated by the gait velocity, stride and gait cycle. In addition, gait stability was also evaluated by the maximum acceleration, maximum angle rate, lateral equilibrium, root mean square and harmonic ratio with a tri-axial accelerometer at a sampling rate of 66 Hz. Differences for the locus of center of mass, gait velocity, gait cycle and stride length were assessed with the paired t test (P < 0.05). Other outcomes were compared with the Wilcoxon signed-rank test (P < 0.05).
Results: With denture wear, the locus of center of mass was significantly shortened, and the gait velocity and harmonic ratio of the vertical angle rate were significantly increased; though other parameters showed no differences. Complete dentures produced an effect on the stability of edentulous patients under both static and dynamic conditions.
Conclusions: These results indicate that wearing complete dentures may be an effective aid to maintain and improve balance and control for elderly people.

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Purpose: The aim of present magnetoencephalography study was conducted to investigate how the cerebellum is involved in intracerebral activity immediately before conscious and voluntary teeth-clenching.
Methods: We recorded the neuromagnetic signal immediately before teeth-clenching in five healthy subjects. A single trial consisted of self-paced teeth-clenching for 2 s followed by a semi-randomized interval of 2-4 s, and 25 trials were performed in a single session. Each subject performed a total of 125 trials over 5 sessions. The subjects also performed five control sessions without the teeth-clenching task. The subjects were asked to observe a visual cue providing task information. We used magnetic field tomography to obtain a tomographic reconstruction of brain activity for each time slice of the average signal for each subject and session. Activation of regions of interest by cerebellar neuron activity was computed from the magnetic field tomography result.
Results: Cerebellar activation before the teeth-clenching task was identified in all five subjects: bilaterally in three, and unilaterally in two. The peak amplitudes for the left and right cerebellar hemispheres in the main session were significantly greater than those in the control session (P < 0.01). Left and right cerebellar hemisphere activities were detected approximately 150 ms after visual cue.
Conclusion: Our findings suggest that the cerebellum is involved in the signal pathway immediately before teeth-clenching.

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