lets start with how rats teeth are normally. The bottom mandible of the jaw is not solid like a human, its actually 2 pieces connected by a ligament. This enables the bottom teeth to splay out to grip things etc. when a rat is struggling, sometimes yawning etc, those teeth will splay but will return to normal beside each other after. The way to tell if your rat has a true misalignment of their teeth called malocclusion is to look at the top of the teeth. Do they go straight across more or less evenly or is there slants and crookedness going on? The top incisors grind against the opposing bottom incisors when they brux to keep the teeth evenly ground down, when a tooth or teeth are out of alignment you will get crooked teeth that will eventually need trimming.