Underbite. Animation showing a dental underbite, a malocclusion (misalignment of the teeth) where the upper teeth lie inside of the lower teeth when the jaws are closed. The whole jaw is affected with the molars also being out of alignment. This condition, also known as prognathism (Class III) is caused by the upper and lower jaws being different sizes. Underbite can cause difficulty chewing and lead to inflammation of the temporomandibular joint, the joint between the lower jaw and skull. Treatment is with orthodontics and jaw surgery to create a normal occlusion (seen at end).HD master is flattened onto a black background, as seen in this preview. The original file has a transparent alpha channel and is available as the HD master of clip K003 3771.