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Ishimaru Tomoya

Faculty of Dental MedicineAssistant Professor

Researcher basic information

■ Degree
  • Doctor of Philosophy, Hokkaido University, Mar. 2023
■ URL
researchmap URLホームページURL■ Various IDs
Researcher number
  • 41004089
J-Global ID■ Educational Organization

Career

■ Career
Career
  • Apr. 2025 - Present
    北海道大学大学院歯学研究院, 冠橋義歯・インプラント再生補綴学教室, 助教
  • Oct. 2023 - Mar. 2025
    北海道大学病院歯科診療センター, クラウン・ブリッジ歯科, 医員
Educational Background
  • Apr. 2019 - Mar. 2023, Hokkaido University, 大学院, 歯学院
  • Apr. 2012 - Mar. 2018, Hokkaido University, School of Dental Medicine, 歯学科

Research activity information

■ Papers
  • Verification of the relationship between awareness of clenching or the teeth contacting habit and the integral value of masseteric electromyogram during diurnal wakefulness.
    Tomoya Ishimaru; Taihiko Yamaguchi; Taishi Saito; Yu Nakagawa; Yoshinori Hattori; Takahiro Ono; Yoshiaki Arai; Yoko Hasegawa; Hiroshi Shiga; Katsushi Tamaki; Junko Tanaka; Kazuhiro Tsuga; Hitoshi Abekura; Shouichi Miyawaki; Aya Maeda-Iino; Saki Mikami; Akihito Gotouda; Koichi Shimizu; Yuji Kato; Takeshi Namita; Shinichiro Kuroshima
    Clinical oral investigations, 29, 11, 502, 502, 11 Oct. 2025, [Peer-reviewed], [Lead author], [International Magazine]
    English, Scientific journal, PURPOSE: This study aimed to clarify the relationship between diurnal awake bruxism (AB) awareness, tooth-contacting habit (TCH) awareness, and the electromyographic (EMG) waveform integral value. MATERIALS AND METHODS: Unilateral masseteric EMG recordings during the daytime were performed on the habitual masticatory side using an ultraminiature wearable EMG device. One hundred and seven participants (50 and 57 with and without diurnal tooth clenching (d-TC) awareness, respectively) were included. d-TC awareness and TCH awareness were assessed using questionnaires. The standardized burst integral (S-integral) value was calculated for each participant. RESULTS: There was a statistically significant association between d-TC awareness and TCH awareness. The S-integral values were not significantly associated with the awareness d-TC or TCH. The frequency distribution of EMG waveforms of the awareness and non-awareness groups exhibited wide-range overlaps both for d-TC and TCH. CONCLUSION: d-TC or TCH awareness showed no clear correlation with the S-integral value, suggesting that it is important to evaluate AB and TCH based on objective and quantitative test results, such as the masseter muscle's EMG data. CLINICAL RELEVANCE: Diagnosis, treatment, and management of AB and TCH are important issues in dental medicine. The obtained results regarding the actual state of awareness of AB and TCH, and the EMG integral value that was one of the important EMG indices, were considered useful information for establishing diagnostic and assessment methods for AB and TCH in future clinical dentistry.
  • A Pilot Study on the Estimation of Bite Force Using Electromyograms of the Masticatory Muscles.
    Sota Takahashi; Taihiko Yamaguchi; Toshinori Nakajima; Masana Maeda; Miku Saito; Tomoya Ishimaru; Saki Mikami; Akihito Gotouda
    Journal of oral rehabilitation, 09 Sep. 2025, [Peer-reviewed], [International Magazine]
    English, Scientific journal, BACKGROUND: It has not been established how electromyographic (EMG) data of masticatory muscles can estimate bite force (BF) during daily activities at home, such as eating and bruxism, utilising the EMG-BF correlation. OBJECTIVE: This study aimed to investigate the relationship between actual BF and BF estimated using corresponding EMG data and additional information on BF and EMG measured on a separate day. METHODS: Participants were 16 volunteers. The unilateral masseteric EMG was recorded during clenching tasks at 10 levels of force up to maximum voluntary clenching (MVC) twice on separate days (Day 1, Day 2). BF was simultaneously measured using a pressure-sensitive occlusal film. The regression equation between the BF and EMG amplitude was calculated on Day 1. Estimated BF on Day 2 was calculated using information on the EMG amplitude on Day 2 (EMG-amp), Day 1 BF at the MVC, and Day 1 regression equation. RESULTS: Actual value of BF showed a small correlation coefficient with EMG-amp, whereas strong correlations were observed with the estimated values additionally using information of Day 1 BF at the MVC. The estimated BF additionally using information of Day 1 regression equation adjusted by the ratio of EMG at the MVC on Day 1 to that of Day 2 showed the smallest error, indicating the power to estimate BF using corresponding EMG data became further improved. CONCLUSIONS: The obtained findings suggest the possibility of the clinical method estimating BF using corresponding EMG data with the additional information of EMG and BF on a separate day.
  • Day-To-Day Variation in Masseteric Electromyographic Waveforms During the Diurnal Awake State.
    Yu Nakagawa; Taihiko Yamaguchi; Tomoya Ishimaru; Taishi Saito; Yoshinori Hattori; Takahiro Ono; Yoshiaki Arai; Yoko Hasegawa; Hiroshi Shiga; Katsushi Tamaki; Junko Tanaka; Kazuhiro Tsuga; Hitoshi Abekura; Shouichi Miyawaki; Aya Maeda-Iino; Saki Mikami; Akihito Gotouda; Koichi Shimizu; Yuji Kato; Takeshi Namita; Shinichiro Kuroshima
    Journal of oral rehabilitation, 12 Jun. 2025, [Peer-reviewed], [International Magazine]
    English, Scientific journal, BACKGROUND: To establish diagnostic/assessment criteria for awake bruxism (AB) using electromyography of the masseter muscle during the diurnal awake state (d-EMG), it is necessary to refer to the actual state of variation of d-EMG waveforms between different days (d-variation). OBJECTIVE: This study aimed to clarify the actual state of d-variation in various indices of d-EMG waveforms. METHODS: The participants included 91 volunteers with or without awareness of diurnal tooth clenching. Measurements were conducted on three days within a two-week period using a wearable EMG device set at the unilateral masseteric region. A waveform with an amplitude more than twice the baseline and a duration of more than 0.25 s was defined as a burst. The number of bursts/h, number of episodes/h, number of bursts ≥ 20% maximum voluntary clenching (MVC)/h, burst integral value/h, and standardised burst integral value/h were calculated. The coefficient of variation (CV) of the three measurement days was calculated for each index. RESULTS: The five indices showed no significant differences among the three days. The median CV for the number of episodes/h, number of bursts/h, number of bursts ≥ 20% MVC/h, burst integral value/h, and standardised burst integral value/h were 0.233, 0.276, 0.507, 0.417, and 0.482, respectively. Of the indices, bursts/h and episodes/h had the smallest day-to-day variation. The CV for the number of waveforms tended to be smaller the larger the number of waveforms. CONCLUSION: These findings are considered useful as reference data for establishing diagnostic/assessment criteria for AB using masseter EMG in the future.
  • Examination of the relationship between masseter muscle activity during sleep and wakefulness measured by using a wearable electromyographic device.
    Saki Mikami; Taihiko Yamaguchi; Mebae Takahashi; Ai Kudo; Miku Saito; Toshinori Nakajima; Masana Maeda; Taishi Saito; Toshimitsu Sakuma; Sota Takahashi; Tomoya Ishimaru; Akihito Gotouda
    Journal of prosthodontic research, 68, 1, 92, 99, 16 Jan. 2024, [Peer-reviewed], [Domestic magazines]
    English, Scientific journal, Purpose This study aimed to measure masseter muscle activity throughout the day in outpatients suspected of having awake bruxism (AB) and/or sleep bruxism (SB) and examine the relationship between AB and SB by comparing muscle activity during daytime wakefulness and nighttime sleep.Methods Fifty outpatients with suspected SB and/or AB participated in this study. A single-channel wearable electromyogram (EMG) device was used for EMG recording. The selected EMG bursts were divided into bursts during sleep (S-bursts) and bursts during awake state (A-bursts). The number of bursts per hour, average burst duration, and ratio of burst peak value to maximum voluntary contraction were calculated for both the S- and A-bursts. These values of the S- and A-bursts were then compared, and the correlations between them were analyzed. Additionally, the ratios of phasic and tonic bursts in the S- and A-bursts were compared.Results The number of bursts per hour was significantly higher for A-bursts than for S-bursts. No significant correlation was found between the numbers of S- and A-bursts. The ratio of phasic bursts was large and that of tonic bursts was small in both the S- and A-bursts. A comparison of the S- and A-bursts showed that the S-bursts had a significantly lower ratio of phasic bursts and higher ratio of tonic bursts than the A-bursts.Conclusions The number of masseteric EMG bursts during wakefulness did not show any association with that during sleep. It became clear that sustained muscle activity was not dominant in AB.
  • Actual state of the diurnal masseteric electromyogram: Differences between awareness and non-awareness of awake bruxism.
    Tomoya Ishimaru; Taihiko Yamaguchi; Taishi Saito; Yoshinori Hattori; Takahiro Ono; Yoshiaki Arai; Yoko Hasegawa; Hiroshi Shiga; Katsushi Tamaki; Junko Tanaka; Kazuhiro Tsuga; Hitoshi Abekura; Shouichi Miyawaki; Aya Maeda-Lino; Saki Mikami; Akihito Gotouda; Kaoru Satoh; Koichi Shimizu; Yuji Kato; Takeshi Namita
    Journal of prosthodontic research, 12 Jan. 2024, [Peer-reviewed], [Lead author], [Domestic magazines]
    English, Scientific journal, PURPOSE: This study aimed to elucidate the relationship between diurnal masseter muscle activity and awareness of diurnal awake bruxism (d-AB) by conducting a comparative analysis of electromyographic (EMG) data from individuals with and without awareness of diurnal awake bruxism (d-AB), utilizing EMG data gathered from multiple subjects. METHODS: Unilateral masseter electromyography (EMG) recordings were performed during the daytime using an ultraminiature wearable EMG device. A total of 119 participants (59 with awareness of diurnal tooth clenching [d-TC] and 60 without awareness of d-TC) were included. Waveforms longer than 0.25 s with the two amplitude conditions, exceeding twice the baseline and >5% of maximum voluntary clenching, were extracted. In addition, the number of bursts and episodes (groups of bursts), burst duration, and burst peak amplitude were calculated for each participant. RESULTS: There were no significant differences in the EMG parameters between the groups with and without awareness of d-TC. Additionally, the frequency distribution of the number of EMG waveforms exhibited wide ranges and substantial overlap between the two groups. CONCLUSIONS: The variability in the number of bursts and episodes, burst peak amplitude, and burst duration among subjects suggests the need for an objective classification of d-AB severity based on EMG values. The absence of significant differences and large overlap in frequency distributions between the groups with and without awareness of d-TC indicate difficulty in predicting muscle activity solely based on awareness of d-AB.
  • Relationship between measured value of bite force measurement devices and amplitude of masseteric electromyogram waveform: comparison of different bite force measurement systems
    Nakajima, Toshinori; Yamaguch, Taihiko; Takahashi, Sota; Maeda, Masana; Ishimaru, Tomoya
    北海道歯学雑誌, 44, 61, 68, 北海道歯学会, 15 Sep. 2023, [Peer-reviewed]
    Japanese, Scientific journal, Purpose: This study aimed to investigate the relationship between amplitude of masseteric electromyogram (EMG) and measured values of T-scan system (TS) which can measure dynamic occlusal force but whose measured values are not expressed in a specific unit of force, and the relationship bet ween the masseteric EMG amplitude and bite force value expressed in Newton units measured using the Dental Prescale (PS).
    Methods: A total of 18 healthy participants were included. EMG and bite force were measured simultaneously as the participants’ jaws occluded at 10 levels of strength, including the maximum voluntary contraction force.
    Measurements were taken twice on different days. EMG electrodes were attached to the masseter muscle region on the main masticatory side and maintained for TS and PS measurements on the same day.
    Regarding EMG measurements, the maximum amplitude of each waveform was measured. Regression analysis was performed with the measured values for TS and PS as objective variables and EMG amplitudes as explanatory variables.
    In addition, the ratio of the regression coefficients for TS and PS (TS/PS) was calculated.
    Results: Both PS value and EMG amplitudes and TS value and EMG amplitudes showed a linear and significant correlation. The average correlation coefficients of PS and EMG values measured first and second were 0.91 and 0.88, respectively. Those for TS measured first and second were 0.90 and 0.85, respectively. For both PS and TS, no significant difference（PS：P=0.20，TS：P=0.35）was observed in the regression coefficients of the measured occlusal force values and EMG amplitudes between the 1st and 2nd measurements. However, considerable variabilities were observed both between days and between participants.
    A significant correlation was found between the regression coefficient of the occlusal force measured using PS and the EMG amplitude between the 1st and 2nd measurements. However no significant correlation was found in the TS measurements.
    The median values of the ratio of regression coefficients (TS/PS) for all participants in the 1st and 2nd measurements were 5.67 and 6.84, respectively. Although there was no significant difference（P=0.37） between the 1st and 2nd measurements, variability was observed between the days. In addition, the variations among participants were large.
    Conclusion: The measurement values using TS and PS correlated with the EMG amplitude. The finding suggests the possibility of linking the occlusal force displays of the TS an d PS via electromyogram amplitude values. However, the ratio of regression coefficients between measurement values using PS and EMG amplitudes and TS and EMG amplitudes in the linear regression equations was not constant owing to large inter-individual variations and day-to-day variabilities.
    It is suggested that it is necessary to improve the analysis methods and parameters that link the occlusal force displays of the TS and PS.
  • A case with awake bruxism of extremely high frequency despite normal range of electromyographic activities during sleep
    Mariko Mizuno, Taihiko Yamaguchi, Miku Saito, Tomoya Ishimaru, Saki Mikam
    Nov. 2022, [Peer-reviewed]
■ Other Activities and Achievements
■ Lectures, oral presentations, etc.
  • 移植細胞の違いはBRONJ 様病変の硬軟組織治癒に異なった影響を与える
    松澤樹; 石丸智也; 澤瀬隆; 黒嶋伸一郎
    第55回公益社団法人日本口腔インプラント学会学術大会, 26 Oct. 2025
    24 Oct. 2025 - 26 Oct. 2025
  • 細胞移植の違いがBRONJ様病変の軟組織治癒に与える影響を比較解析する
    松澤 樹; 石丸智也; 澤瀬 隆; 黒嶋伸一郎
    公益社団法人日本口腔インプラント学会 第45回東北・北海道支部学術大会, 07 Sep. 2025
    06 Sep. 2025 - 07 Sep. 2025
  • BRONJ様病変に異なる影響を与える非培養脂肪組織由来細胞移植と培養末梢血単核球由良齲細胞移植
    黒嶋伸一郎; 石丸智也
    第43回日本骨代謝学会学術集会, 25 Jul. 2025
    24 Jul. 2025 - 26 Jul. 2025
  • 非培養SVFCsと培養QQPBMNCs移植はBRONJ様病変の治癒に異なった影響を与える
    黒嶋伸一郎; 松澤 樹; 石丸智也; 澤瀬 隆
    第37回北海道骨粗鬆症研究会学術集会, 11 Jan. 2025
    11 Jan. 2025 - 11 Jan. 2025
  • 日中覚醒時咬筋活動量と臨床所見の関連性の検討
    石丸 智也; 山口泰彦; 齋藤大嗣; 長谷川陽子; 荒井良明; 志賀博; 玉置勝司; 津賀一弘; 宮脇正一; 三上紗季; 後藤田章人; 佐藤華織
    第36回一般社団法人日本顎関節学会総会・学術大会, 08 Jul. 2023, Poster presentation
    08 Jul. 2023 - 09 Jul. 2023
  • 日中覚醒時の咬筋筋電図波形積分値の実態解明
    石丸 智也; 山口泰彦; 齋藤大嗣; 服部佳功; 小野高裕; 荒井良明; 長谷川陽子; 志賀博; 玉置勝司; 田中順子; 津賀一弘; 安部倉仁; 三上紗季; 後藤田章人; 佐藤華織
    令和4年度公益社団法人日本補綴歯科学会東北・北海道支部学術大会, 16 Oct. 2022, Oral presentation
    15 Oct. 2022 - 16 Oct. 2022
  • シンポジウム1 みんなで学ぶ顎関節症の鑑別診断 -顎関節診療歯科医ドクターT-
    【シンポジスト】佐藤 淳; 北川 善政; 土生 学; 川尻 秀一; 定梶 嶺; 大井 一浩; 【パネリスト】石丸 智也; 久根下紀香; 松﨑奈々香; 宮園 敬資; 吉田 一央; 渡辺 陽久
    第35回 一般社団法人日本顎関節学会総会 学術大会, Jul. 2022
  • 日中覚醒時ブラキシズムの自覚の有無と咬筋活動の実態に関する検討
    石丸 智也; 山口泰彦; 服部佳功; 小野高裕; 荒井良明; 長谷川陽子; 志賀博; 玉置勝司; 田中順子; 津賀一弘; 安部倉仁; 宮脇正一; 前田綾; 三上紗季; 後藤田章人; 佐藤華織
    日本顎口腔機能学会第64回学術大会, 19 Dec. 2020, Oral presentation
    19 Dec. 2020 - 20 Dec. 2020
■ Research Themes
  • Understanding of medication-related osteonecrosis of the jaw surrounding implants based on osteocyte death
    Grants-in-Aid for Scientific Research
    01 Apr. 2025 - 31 Mar. 2028
    石丸 智也
    Japan Society for the Promotion of Science, Grant-in-Aid for Early-Career Scientists, Hokkaido University, 25K20321
  • 副甲状腺ホルモン製剤の口腔内投与によるインプラント周囲MRONJの病態形成機構解明と革新的治療法開発研究
    2024年度研究開発助成
    Apr. 2025 - Mar. 2028
    黒嶋伸一郎; 石丸智也; 長谷川智香
    公益財団法人ナカニシ財団, Coinvestigator