When it comes to your toothbrush, you need to worry about two things: the size and the type of bristles.
Your toothbrush needs to reach all areas of your mouth, including the teeth in the very back. That means you probably need a toothbrush on the smaller side. A big toothbrush might look like it cleans more, but if it’s so big you can’t use it to clean your back molars, then what’s the point? The type of bristles are also important. You want soft ones. The harder the bristles, the more likely they will hurt your enamel or gums.