College Physics (4th Edition)

The force exerted by the incisors is $83.3~N$
The torque exerted by the muscle about the joint is equal in magnitude to the torque exerted by the incisors about the joint. We can find the force $F_i$ exerted by the incisors: $r_i~F_i = r_m~F_m$ $F_i = \frac{r_m~F_m}{r_i}$ $F_i = \frac{(2.5~cm)(220~N)}{6.6~cm}$ $F_i = 83.3~N$ The force exerted by the incisors is $83.3~N$