This study used the electromyogram (EMG)/force-function curve as a mea
ns of estimating functional bite forces. Surface EMG recordings were m
ade for the masseter and anterior temporalis muscles bilaterally in te
n adults while incisal bite forces were measured using a force transdu
cer embedded in custom-made hydroplastic bite blocks. Measurements wer
e made for mouth openings of 15 and 30 mm. Each subject was first inst
ructed to develop a maximum level of bite force, and then to develop b
ite-force levels that corresponded to decreasing percentages of his or
her maximum, from 90 to 10%, in 10% decrements. After the force measu
rements had been made, each subject was instructed to incise various f
ood substances. The power-density spectrum and r.m.s. power level were
calculated for each sample. Maximum bite-force levels varied consider
ably among the 10 subjects, ranging from a minimum of 2.5 kg to a maxi
mum of 40 kg. For the subjects as a whole, estimated bite forces for t
he different types of food ranged from 3.0 to 5.5 kg. This range was i
ndependent of the subjects' maximum bite-force levels. Thus, bite forc
es exerted to incise different foods probably depend more on the food
than on the individual's bite capabilities. There was variability with
in this range, although, as expected, bite forces were least for choco
late and greatest for apple and toffee.