Malocclusion is defined as abnormal positioning of the teeth such that they do not meet properly. It is usually caused by a combination of genetic, environmental, and behavioral factors that interfere with proper jaw and tooth development. The three main classes of malocclusion are class 1 (teeth are crowded or spaced), class 2 (overbite with lower jaw smaller than upper), and class 3 (underbite with lower jaw protruding forward). Symptoms include abnormal tooth wear, facial changes, and speech or chewing difficulties.