Question

why do teeth have different shapes?

Answer 1

Our teeth are different shaped because they have to do different types of work.
Here's the brief information:
Incisor teeth are the teeth in the very front. They’re the sharpest teeth, built to cut food and shaped to shovel the food inward.

Canine teeth are in the corners of your mouth. Because they’re meant for grasping and tearing food, they have very long roots.

Premolars are located just behind your Canine teeth. Premolars have a more flat chewing surface because they’re meant for crushing food.

The Molars are the last teeth towards the back of your mouth. Molars are much bigger than the Premolars and have bigger, flatter chewing surfaces because their job is to chew and grind the food into smaller pieces.