 Occlusion refers to the closing of the dinosaur's mouth, where the teeth from the upper and lower parts of the jaw meet.If the occlusion causes teeth from the maxillary or premaxillary bones to cover the teeth of the dentary and predentary, the dinosaur is said to have an overbite, the most common condition in this group.The opposite condition is considered to be an underbite, which is rare in theropod dinosaurs.