REDUCTION OF MASSETER MUSCLE-ACTIVITY IN BOTTLE-FED BABIES

Our previous studies suggested that there are significant differences in the growth of the jaw and in muscle activity between breast- and bo ttle-fed infants. To confirm these differences quantitatively, myoelec tric activities of the masseter muscles of bottle-fed babies were stud ied. Twelve bottle-fed babies, as well as 12 breast-fed babies as a co ntrol group, were examined electromyographically during bottle or brea st feeds. The duration time of sucking bursts, interval time, cycle ti me, 0-to-peak amplitude, integrated amplitude of bursts, and integrate d amplitude/duration time were measured and the number of bursts over 30 mu V was counted. All differences of means were significant by t-te st. 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 report ed. The reason why previous researchers thought that the sucking patte rns in breast- and bottle-fed babies are essentially the same is consi dered, and the implications of the differences for dental health are d iscussed.