健常高齢者における咬筋硬直のミオトノメトリ測定と最大咬合力との関連性．

Association between myotonometric measurement of masseter muscle stiffness and maximum bite force in healthy elders.

• Koji Hara
• Chizuru Namiki
• Kohei Yamaguchi
• Kenichiro Kobayashi
• Takayuki Saito
• Kazuharu Nakagawa
• Miki Ishii
• Takuma Okumura
• Haruka Tohara

抄録

背景:

最大咬合力（MBF）は咀嚼機能の一般的で有用な指標であり，高齢者の体力と相関している．強制咬合時の咬筋の硬さの触診はMBFと関連していると考えられています。しかし、この評価方法は主観的な判断に依存しており、MBFと咬筋硬直（MMS）の定量的測定値との関係を検証した研究はありません。

BACKGROUND: Maximum bite force (MBF) is a common and useful index of masticatory function; it correlates with physical strength in elderly people. Palpation of stiffness in the masseter muscle during forceful biting has been considered to be associated with MBF. However, this assessment method relies on subjective judgments; no study has verified the relationship between MBF and quantitative measurements of masseter muscle stiffness (MMS).

目的:

咬筋筋ミオトノメトリクス評価結果とMBFとの関連を検証することを目的とした。

OBJECTIVE: We aimed to verify the association between masseter muscle myotonometric assessment results and MBF.

方法:

首都圏の65歳以上の地域居住者117名を対象とした。強咬時の支配側のMMSをMyotonPRO装置を用いて測定した。安静時と強制咬合時の咬合筋厚（MMT）を超音波診断装置を用いて測定し，安静時と強制咬合時の咬合筋厚の差（DMMT）を求めた．MBFデータは感圧シートとそれに付随する装置を用いて取得した．MBFとMMSに影響を与える独立変数を決定するために，年齢，性別，歯数を調整した多変量線形回帰分析を行った．

METHODS: In total, 117 community-dwelling >65-year-old individuals from the Tokyo metropolitan area were assessed. MMS on the dominant side during forceful biting was measured with a MyotonPRO device. Masseter muscle thickness (MMT) during rest and forceful biting was measured with an ultrasonic diagnostic apparatus, and the difference in MMT (DMMT) between the rest and forceful biting conditions was determined. MBF data were obtained with a pressure-sensitive sheet and an associated device. To determine the independent variables affecting MBF and MMS, multivariate linear regression analyses with adjustments for age, sex and number of teeth were performed.

結果:

多変量解析の結果、MBFは歯の数(β=.489、P<.001)およびMMS(β=.259、P=.003)と相関していた(R=.433)。MMSはMBF(β=.308, P=.003)およびDMMT(β=.430, P<.001)と相関した(R=.326)。

RESULTS: The multivariate analysis revealed that MBF correlated with the number of teeth (β = .489, P < .001) and MMS (β = .259, P = .003) (R  = .433). MMS correlated with MBF (β = .308, P = .003) and DMMT (β = .430, P < .001) (R  = .326).

結論:

咬合筋の硬さは，咬合時に咬合筋が発生する力を反映している可能性があります．そのため，最大咬合力（MBF）を評価する際には，咬合筋の強さの指標としてだけでなく，歯の喪失を評価するためにもMMSは有効である．

CONCLUSION: Masseter muscle stiffness possibly reflects a force generated by the masseter muscle during forceful biting. Therefore, MMS is effective to assess tooth loss as well as an index of masseter muscle strength when evaluating MBF.

© 2020 John Wiley & Sons Ltd.