Orthognathic surgery (Greek "orthos" means straight and "gnathos" means jaw) is a single or double jaw surgery which is performed to reposition the jaws. During orthognathic surgery a correct jaw alignment and occlusion, as well as, facial harmony is achieved. When the jaws are moved forwards or backwards, up or down, or rotated, the facial soft tissue in the chin, cheeks, lips and tip of the nose move accordingly. Therefore, once the jaws are correctly positioned a harmony between the facial features is acquired which results in a beautiful profile. Malocclusion impedes jaw function and does not allow proper chewing of food. If there is no adequate contact between upper and lower teeth, grinding of food is insufficient. This might exert negative influence on food digestion and overall body health. Moreover, crowding of teeth facilitates accumulation of food debris and aggravates maintenance of oral hygiene, therefore, teeth are more likely to be affected by dental caries or periodontal disease. Due to malocclusion teeth may wear out faster than usually and the lifetime of dental prostheses may shorten. Severe skeletal malocclusions caused by jaw mismatch in size and position may cause serious problems. For example, extremely small lower jaw may result in snoring and sleep apnea, which can consequently cause many health problems. In cases of short upper lip and vertical excess of the upper jaw, the lips are usually open as they fail to close without efforts due to increased lower third of the face. Consequently, it may stimulate undesirable mouth breathing which further worsens occlusion. Frequently malocclusion can have strong negative effect on speech function and often it can be accompanied by jaw joint pain. And last but not least, occlusion and the position of jaws define the height of the lower third of the face to the greatest extent, hence the aesthetics of the facial profile as well. Convex "bird face" or concave "mature face" profiles are considered anaesthetic, therefore severe anomalies can cause social problems if left untreated.