Masahiro Tanaka

Osaka Dental University, Ōsaka, Ōsaka, Japan

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Publications (78)8.14 Total impact

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    ABSTRACT: Implant treatment is believed to cause minimal invasion of remaining teeth. However, few studies have examined teeth adjacent to an implant region. Therefore, this study investigated the effect of occlusal contact size of implants on the periodontal mechanosensitive threshold of adjacent premolars. A cross-sectional study design was adopted. The Department of Oral Implantology, Osaka Dental University, was the setting where patients underwent implant treatment in the mandibular free-end edentulous area. The study population comprised of 87 patients (109 teeth) who underwent follow-up observation for at least 3 years following implant superstructure placement. As variables, age, sex, duration following superstructure placement, presence or absence of dental pulp, occlusal contact area, and periodontal mechanosensitive threshold were considered. The occlusal contact area was measured using Blue Silicone ® and Bite Eye BE-I ® . Periodontal mechanosensitive threshold were measured using von Frey hair. As quantitative variables for periodontal mechanosensitive threshold, we divided subjects into two groups: normal (≤5 g) and high (≥5.1 g). For statistical analysis, we compared the two groups for the sensation thresholds using the Chi square test for categorical data and the Mann–Whitney U test for continuous volume data. For variables in which a significant difference was noted, we calculated the odds ratio (95 % confidence interval) and the effective dose. There were 93 teeth in the normal group and 16 teeth in the high group based on periodontal mechanosensitive threshold. Comparison of the two groups indicated no significant differences associated with age, sex, duration following superstructure placement, or presence or absence of dental pulp. A significant difference was noted with regard to occlusal contact area, with several high group subjects belonging to the small contact group (odds ratio: 4.75 [1.42–15.87]; effective dose: 0.29). The results of this study suggest an association between implant occlusal contact area and the periodontal mechanosensitive threshold of adjacent premolars. Smaller occlusal contact application resulted in an increased threshold. It appears that prosthodontic treatment should aim not only to improve occlusal function but also to maintain oromandibular function with regard to the preservation of remaining teeth.
    Preview · Article · Dec 2015 · SpringerPlus
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    ABSTRACT: Despite advances in stem cell biology, there are few effective techniques to promote the osteogenic differentiation of human primary dedifferentiated fat (DFAT) cells. We attempted to investigate whether epigallocatechin-3-gallate (EGCG), the main component of green tea catechin, facilitates early osteogenic differentiation and mineralization on DFAT cells in vitro. DFAT cells were treated with EGCG (1.25–10 μM) in osteogenic medium (OM) with or without 100 nM dexamethasone (Dex) for 12 days (hereafter two osteogenic media were designated as OM(Dex) and OM). Supplementation of 1.25 μM EGCG to both the media effectively increased the mRNA expression of collagen 1 (COL1A1) and runt-related transcription factor 2 (RUNX2) and also increased proliferation and mineralization. Compared to OM(Dex) with EGCG, OM with EGCG induced earlier expression for COL1A1 and RUNX2 at day 1 and higher mineralization level at day 12. OM(Dex) with 10 μM EGCG remarkably hampered the proliferation of the DFAT cells. These results suggest that OM(without Dex) with EGCG might be a preferable medium to promote proliferation and to induce osteoblast differentiation of DFAT cells. Our findings provide an insight for the combinatory use of EGCG and DFAT cells for bone regeneration and stem cell-based therapy.
    Preview · Article · Nov 2015 · International Journal of Molecular Sciences
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    ABSTRACT: Our previous research reports that NaOH treatment leads to the formation of a Ti-O-Na titanate layer on the titanium-6-aluminium-4-vanadium (Ti6Al4V) surface. However, this titanium nanosheets (TNS) hydrogel layer is so brittle that it easily detaches from the implant and can cause many problems, including degradation in the living body due to inhomogeneous composition distribution. The aims of the present study were to investigate combined alkali-treatment of Ti6Al4V alloy and then heated and evaluate the ability of this modified surface to affect osteogenic differentiation of rat bone marrow (RBM) cells, to increase the success rate of titanium implants. We fabricated TNS on titanium alloy surfaces by NaOH treatment prior to heat treatment at 600 °C, and determined RBM cell properties and differentiation potential on the surface in comparison to untreated control surfaces. The nanoscale network structures formed by alkali etching markedly enhanced RBM cell adhesion and osteogenic-related gene expression. Other cell behaviors, such as proliferation, alkaline phosphatase activity, osteocalcin deposition and mineralization, were markedly increased on the TNS-modified Ti6Al4V with heat treatment. Our results suggest that titanium implants modified with nanostructures promote osteogenic differentiation, which may improve the biointegration of these implants into the alveolar bone.
    Preview · Article · Jul 2015 · Journal of Hard Tissue Biology
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    Masaki Kakudo · Norio Mukai · Junko Tanaka · Masahiro Tanaka
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    ABSTRACT: Patient: The patient was a 68-year-old woman who came to our hospital complaining of a masticating disorder due to loss of a mandibular removable partial denture. The remaining teeth of the maxilla were the right second premolar and second molars on both sides. A maxillary removable partial denture had been set at the site of the defect. The mandibular right second premolar, and first and second molars on both sides were missing. A removable partial denture was manufactured by the traditional method and fitted to the mandible. The tongue movement during mastication was observed using ultrasonography, and was classified into the early, intermediate, and final periods from the M-mode waveform. Then, by tracing the B-mode coronal images at the lowest points of the M-mode for five consecutive waveforms of each period, we measured the distance to the surface of the mandible skin from two points on the surface of the tongue in the left and right sides 15 mm away from the midline. The difference in height between the left and right sides of the tongue was observed before and after treatment. Movements were chewing on one side of the left or right. The test food was 10 g of cooked rice. Tongue movements were observed before treatment, and at 1 and 6 months after treatment.Discussion: The difference in height of the tongue did not change in each period before treatment, but showed a decreasing trend with the progress of mastication at 1 and 6 months after treatment. Furthermore, at 6 months after treatment it was similar to the clinical reference value of dentate elderly.Conclusion: In this case, it was considered that tongue movement during mastication adapted to the environment by chewing denture in about 6 months, and that wearing dentures affects tongue movement during mastication.
    Preview · Article · Jan 2015 · Annals of Japan Prosthodontic Society
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    ABSTRACT: The present study aimed to investigate cellular behavior on nanoscale features of a titanium surface by controlling the deposition time in NaOH. These effects were then evaluated for osteogenic differentiation of rat bone marrow cells to potentially increase the success rate of titanium implants. Titanium disks were left untreated or soaked in 10 M NaOH for 5 min, and 1h, 3h, 9h and 24 h. Scanning electron and probe microscopy were used to evaluate the nanoscale features. Rat bone marrow cells were seeded on the specimens in osteogenic differentiation medium. Alkaline phosphatase activity, osteocalcin production, and mineralization were then analyzed. Statistical significance was analyzed using one-way ANOVA followed by the Tukey test. Nanofeatures were detected at 1 h after NaOH treatment and were well established at 9 h. Alkaline phosphatase activities of specimens soaked for 1 h or 3 h were significantly different from specimens soaked for 9 h or 24 h after 14 days of differentiation. Osteocalcin production and calcium deposition between untreated specimens and specimens soaked for 5 min, as well as between specimens soaked for 9 h and 24 h, were significantly different after 21 days. It was found that the nanoscale modification of a titanium implant surface by NaOH treatment affects osteoblastic differentiation of bone marrow cells and enhances mineralization. This study found that modification of titanium surfaces with NaOH could be an effective method of improving their biological properties. Further developments in nanotechnology may help improve osseointegration of titanium implants.
    No preview · Article · Jan 2014 · Journal of Hard Tissue Biology

  • No preview · Article · Jan 2013

  • No preview · Article · Jan 2013 · Annals of Japan Prosthodontic Society

  • No preview · Article · Jan 2013

  • No preview · Article · Jan 2013
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    ABSTRACT: PURPOSE: The aim of this study is to examine the factors, which predict the effect of mandibular condylar movement exercise (MCME). MATERIAL AND METHODS: We investigated the efficiency of MCME and the significant difference in average age and the mean duration length of closed lock symptoms prior to the initial consultation in both success cases and failure cases in initial visiting. Seventy-four women aged between 19 and 75 (mean: 41.4) years were included in this study. RESULTS: On the initial visiting day, the success cases were 50 cases (67.6%) and the failures were 24 cases (23.4%). The average age of success cases is 38.0years, and failure cases are 48.4years. Duration of the lock in success cases is 35.3days, and failure cases are 87.6days. CONCLUSION: These results suggested that lower improvement rates thus correlated with increasing age with exercise. MCME is effective mouth-opening exercise in patients with a history of short duration of locking. In conclusion, age and duration of locking, it must become the important factor predict an effect MCME.
    No preview · Article · Jul 2012 · Journal of cranio-maxillo-facial surgery: official publication of the European Association for Cranio-Maxillo-Facial Surgery
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    ABSTRACT: Recently, there has been considerable interest in finding novel applications and functions for existing dental materials. We found that, at room temperature and atmospheric pressure, titanium oxide spontaneously generates nanostructures very similar to the "nanotubes" created by TiO(2) sputtering. The aim of this study was to evaluate the ability of this surface to affect the cellular osteogenic differentiation response. Titanium disks without and with a 'nanosheet' deposited on their surface were used as the control and test groups, respectively. Cell culture experiments were performed with SD rat bone marrow cells, which were seeded into microplate wells and cultured in media designed to induce osteogenic differentiation. We measured alkaline phosphatase (ALP) activity, osteocalcin (OCN) production, calcium deposition and Runx2 gene expression to assess the levels of differentiation. After 14 and 21 days, cellular ALP activity was significantly higher in the test group than in the control group. After 28 days, cells in the test group also showed significantly more calcium deposition and OCN production than those in the control group. There was significantly different expression of Runx2 mRNA in the test group compared to the control group after 3 days of culture. In conclusion, these data suggest that titanium implants modified by the application of nanostructures promote osteogenic differentiation, and may improve the biointegration of these implants into the alveolar bone.
    No preview · Article · May 2012
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    Junko Tanaka · Norio Mukai · Muto Tanaka · Masahiro Tanaka
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    ABSTRACT: Objective . The purpose of this study was to investigate whether teeth that have undergone prosthetic restoration are under conditions that promote caries recurrence. Methods . The subjects were 20 dentate adults with both a healthy tooth and an affected tooth entirely covered with a complete cast crown in the molar regions of the same arch. The pH was measured in plaque adhering to the margin of the tooth covered with a complete cast crown and adhering to the cervicobuccal area of the natural tooth. In addition, the numbers of cariogenic bacteria (mutans streptococci and lactobacilli) were measured employing the saliva test. The relationships between the number of cariogenic bacteria and plaque pH of the natural tooth and between the number of cariogenic bacteria and plaque pH of the tooth covered with a complete cast crown were investigated. Results . The plaque pH of the tooth covered with a complete cast crown decreased as the numbers of SM and LB increased. The natural tooth were also influenced by the number of SM. Conclusion . Secondary caries are likely to develop from the marginal region of the crown in the oral cavity with a high caries risk unless a preventive program is prepared and the oral environment is improved following the program.
    Preview · Article · Jan 2012 · International Journal of Dentistry

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  • No preview · Article · Jan 2011
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    ABSTRACT: It was proposed that technologies derived from CAD-CAM and computed tomography may be useful for flapless implant treatment procedures. The aims of this study were to validate the reliability of this concept in a prospective 12-month clinical study. Twelve patients with fully edentulous areas in their mandibles were included in this study. A total of 71 implants were inserted in interforaminal regions by use of a CAD/CAM drill template(), specially designed for flapless implant surgery. To assess the degree of pain and discomfort, the patients were examined at 2 days and 1 week after surgery. Patient satisfaction and implant functionality were further evaluated at follow-up intervals of 1, 3, 6, and 12 months postoperatively. One implant failed early in 1 patient. All of the other implants were in a good functional state throughout the study. The mean marginal bone loss after 1 year of follow-up was 0.3 mm (SD, 0.1) at center, 0.5 mm (SD, 0.1) at canine and 0.7 mm (SD, 0.2) at distal fixtures, respectively. Statistically, there was not significant differences among each sites(P>.05)The mean ISQ change after 1 year of follow-up was -1.05 (SD, 2.76) at center, -0.85 (SD, 2.59) at canine and -1.27 (SD, 2.18) at distal fixtures, respectively. This prospective pilot study showed that the use of CAD/CAM technology and flapless implant surgery may be considered reliable for fully edentulous mandible of patients.
    Full-text · Article · Jan 2011
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    Junko Tanaka · Masahiro Tanaka
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    ABSTRACT: The purpose of this study was to investigate the relationship between the number of missing teeth (MT) and the statuses of oral environmental factors (the stimulated salivary flow rate, buffering capacity, and the counts of mutans streptococci, lactobacilli, and Candida) in the elderly. The subjects were 64 elderly subjects with fixed prostheses and 49 who wore removable partial dentures aged over 65 years. We used one-way ANOVA to test for overall differences of the number of MT among 5 oral environmental factors. The significant differences were observed in the lactobacilli counts for different number of MT. The number of MT increased with an increase in the lactobacilli counts with removable denture. In conclusion, for the patients wearing removable dentures, increasing number of MT was associated with an increase in the lactobacilli counts in saliva. For the patients with crowns and fixed partial dentures, the number of MT was not significantly affected by salivary mutans streptococci, lactobacilli, and Candida counts.
    Preview · Article · Sep 2010 · International Journal of Dentistry
  • Junko Tanaka · Masahiro Tanaka · Takayoshi Kawazoe
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    ABSTRACT: The purpose of this study was to investigate oral environmental risk factors involved in caries incidence in the elderly. We investigated the relationship between the oral environment factors of the elderly with both fixed prostheses and removable prostheses at baseline and at follow-up and examined time-course changes of each oral environmental factor by prosthesis type. The subject group consisted 11 elderly patients with fixed prostheses and 11 who wore removable prostheses. We examined oral environmental factors by saliva tests. Five oral environmental factors were examined: the stimulated salivary flow rate, buffering capacity, and the counts of mutans streptococci (SM), lactobacilli (LB), and Candida (CA). We compared these factors for subjects with fixed prostheses and those wearing removable prostheses at baseline and at follow-up. Furthermore, 3-year changes in the factors of each oral environment were compared and evaluated. Significant differences were observed between the two groups in the salivary microbial counts of SM and LB at baseline and at follow-up. The LB counts increased in the Denture group during the 3-year period and significant differences were noted. We found that fixed prostheses are less cariogenic, and removable prostheses cause an increase in the cariogenic bacterial count. Regarding time-course changes by the type of prosthesis, the LB count tended to increase in the subjects with removable prostheses. The risk of caries due to a fixed prosthesis may be lower than that of removable prostheses.
    No preview · Article · May 2009
  • Naoya Uemura · Masahiro Tanaka · Takayoshi Kawazoe
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    ABSTRACT: Neck pain is one of the main symptoms of temporomandibular disorder. Muscle activity of the sternocleidomastoid muscle during occlusion has been clarified in recent years. We reported that when healthy individuals were instructed to chew rapidly, the activity of the sternocleidomastoid muscle responded to activity of the masseter muscle, however, during voluntary jaw opening, activity of the sternocleidomastoid muscle did not respond, but worked actively due to motor programming. The objective of the present study was to investigate the learning effects of repetitive training, that is, changes in activity mode of the neuromuscular system. The sternocleidomastoid and the anterior belly of digastric muscles in 8 healthy male adults were analyzed. In response to acoustic stimulation, each subject was instructed to open their mouth as quickly and widely as possible a total of 30 times with a break between measurements. EMG-reaction times (RT) of the sternocleidomastoid and anterior belly of digastric muscles were measured, and the length of time from the start of EMG activity of agonist to the start of actual movement was measured. In all subjects, at first measurement, EMGRT of the sternocleidomastoid muscle did not precede that of the anterior belly of digastric muscle. With each measurement, the difference in EMG-RT between the sternocleidomastoid and the anterior belly of digastric muscles decreased, and in 6 of the 8 subjects, EMG-RT of the sternocleidomastoid muscle preceded that of the anterior belly of digastric muscle. Repetitive task movement alters the start times of muscular activities, and from the perspective of EMG kinesiology, motor learning effects were confirmed with maximum ballistic voluntary jaw opening.
    No preview · Article · Nov 2008 · Nihon Hotetsu Shika Gakkai Zasshi
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    ABSTRACT: We previously reported correlations between the pressure pain threshold (PPT) at the styloid process, which represents individual pain sensitivity, and PPTs of the masticatory muscles in healthy subjects, and proposed the 95% confidence interval (95%CI) of the PPT at the styloid process as a reference range. In this study, we evaluated its usefulness as a reference range. Serial changes in the PPT relative to the 95%CI were studied in 7 healthy subjects. Next, the determination of abnormal sites in the PPT relative to the 95%CI was studied in 7 patients with temporomandibular disorders (TMD). In the healthy subjects, the PPT remained within the 95%CI at all sites. Since the PPT deviated from the 95%CI at some sites in TMD patients, abnormal sites could be determined. The 95%CI of the PPT at the styloid process is useful as a means for the evaluation of muscle symptoms of TMD patients.
    No preview · Article · Aug 2008 · Nihon Hotetsu Shika Gakkai Zasshi

  • No preview · Article · Jan 2007 · Prosthodontic Research & Practice