Why would god give us and other animals incisor teeth. if we had meant to be in eden forever?

Incisors are for shearing/cutting food. This is used mainly for plants, grains, etc. They actually provide little to no use for eating flesh/meat because in order to eat it, it has to be torn for the body. That's what canines are for. I'm not defending the story, I'm just pointing out that your question should pertain to canine teeth, not incisors.