哺乳瓶栄養児における咬筋の活動低下

Reduction of masseter muscle activity in bottle-fed babies.

抄録

これまでの研究から、母乳栄養児と哺乳瓶栄養児では、顎の成長や筋活動に大きな違いがあることが示唆されています。この違いを定量的に確認するために、哺乳瓶で育てられた乳児の咬筋の筋電活動を調査した。哺乳瓶で育てられた乳児12名と、対照群として母乳で育てられた乳児12名を対象に、哺乳瓶または母乳授乳中の筋電図検査を行った。吸啜バーストの持続時間，インターバル時間，サイクルタイム，0-ピーク振幅，バーストの積分振幅，積分振幅／持続時間を測定し，30μV以上のバースト数を数えた．平均値の差はすべてt-検定により有意であった。哺乳瓶で育てられた赤ちゃんの咬筋の活動は、著しく低下している。この結果は、母乳育児でも哺乳瓶育児でもほとんど同じ吸啜動作が報告されている先行論文とは対照的である。これまでの研究者が、母乳栄養児と哺乳瓶栄養児の吸啜動作は基本的に同じであると考えた理由を考察し、その違いが歯の健康に与える影響を考察した。

Our previous studies suggested that there are significant differences in the growth of the jaw and in muscle activity between breast- and bottle-fed infants. To confirm these differences quantitatively, myoelectric activities of the masseter muscles of bottle-fed babies were studied. Twelve bottle-fed babies, as well as 12 breast-fed babies as a control group, were examined electromyographically during bottle or breast feeds. The duration time of sucking bursts, interval time, cycle time, 0-to-peak amplitude, integrated amplitude of bursts, and integrated amplitude/duration time were measured and the number of bursts over 30 microV was counted. All differences of means were significant by t-test. The masseter muscle activity in bottle-fed babies is significantly reduced. Our results are contrary to previous papers in which almost the same sucking actions in both breast and bottle feeding were reported. The reason why previous researchers thought that the sucking patterns in breast- and bottle-fed babies are essentially the same is considered, and the implications of the differences for dental health are discussed.