Generally the incisive edge of the tooth should be located about 2mm below the upper lip at rest and 2-4mm below the lip edge when smiling. If the gums or the alveolar bone of the upper jaw is exposed when smiling, the teeth are said to be buck teeth. If the teeth or jawbone or maxilla are in front of this vertical line, it is generally considered as a buck tooth. Subconsciously closing the lips together for a long time and finding wrinkles around the lips may also indicate buck teeth. A misalignment between the upper and lower jaws when the teeth are biting together, and the upper row of teeth appearing to be turned out, may also indicate buck teeth. There is also a situation where the back row of teeth are clenched together, but the front teeth are not clenched together, which also indicates the presence of buck teeth.