Class III is where the lower first molar is anterior (or more towards the front of the mouth) than the upper first molar. In this abnormal relationship, the lower teeth and jaw project further forward than the upper teeth and jaws. There is a concave appearance in profile with a prominent chin. Class III problems are usually due to an overgrowth in the lower jaw, undergrowth of the upper jaw or a combination of the two. Like Class II problems, they can be genetically inherited.