Development of masticatory muscles and oral behavior from suckling to chewing in dogs.

1. At the age of 20 postnatal days, more than a half of the dogs (13/20) showed incisor eruption. At the age of 25 postnatal days, half of the dogs (10/20) showed molar eruption. 2. At the age of 24 postnatal days, half of the dogs (10/20) started chewing behavior. 3. EMG amplitudes of temporal muscle were larger than that of masseter muscle until 26.5 days after birth, but they were reversed at 26.5 days after birth. 4. This suggests that in dogs the earlier teeth erupted, the earlier the dominant oral behavior was changed from suckling to mastication, and concomitantly the dominant muscle for the oral behavior was changed from the temporal to the masseter muscle.