Final answer:
To increase the mechanical advantage of incisors, which act as wedges, one would need to increase their length without changing the thickness at the widest part. This would make the wedge longer and more effective for cutting and biting into food. So the correct option 4.
Step-by-step explanation:
The mechanical advantage of incisors, which are front teeth that act as wedges, can be increased by altering their physical dimensions about the fulcrum, which in this context is where the tooth is anchored in the jaw. Based on the principles of levers and wedges, we can assess the options presented.
- A decrease in the distance of the teeth from the fulcrum would not increase the mechanical advantage as it would make the arm of the lever shorter.
- An increase in the distance of the teeth from the fulcrum would also not increase the mechanical advantage for a wedge since the fulcrum does not move in this context.
- An increase in the thickness at the widest part of the teeth without changing the length would not affect the mechanical advantage as a wedge. The wedge's efficiency is related to the length and sharpness of the wedge rather than its thickness.
- An increase in the length of the teeth without changing the thickness at the widest part would increase the mechanical advantage as a wedge. The longer wedge would allow a greater force to be exerted at the tip of the tooth.
Thus, the correct answer is an increase in the length of the teeth and no change in the thickness at the widest part of the teeth, which would make the wedge longer and more effective for cutting and biting.