The face is one of the most important parts of the body in every respect. It gives our basic aesthetic appearance and is where we perform many vital functions. These include eating, breathing, speaking, mimicry, taste and feeling. Anatomically, the upper and lower jaws cover two thirds of the face. The face itself is made up of the forehead; the upper jaw and cheeks; and the lower jaw. Jawbones, unlike other bones, have teeth on them and are in close co-operation with one another. Corrective jaw surgery covers diseases of the face. These include congenital-developmental diseases and trauma as well as tumors.
Structural and Functional Properties of Jaw Bones
To better understand corrective jaw surgery, we look at the face’s anatomical features. First, we look at Jawbones. We classify Jawbones between parts with teeth and parts without teeth.
Alveolar bone (toothed segment):
The Alveolar bone is a soft-bone structure that holds the teeth by special bonds. It also is known as the Alveolar Process. Its soft nature allows some movement of the teeth to protect them from shock. The Alveolar bone surrounds the teeth and only can survive when it is holding onto the teeth. When a tooth is pulled, its root is pulled out of the Alveolar bone. This deforms that portion of the Alveolar bone and leaves an empty space in place of the tooth’s root. The result is Gingival weakness in this area which in turn may cause a reduction in soft tissue support. This results in aesthetic problems, as well as the misalignment of other teeth in this region. Teeth misalignment can then cause deterioration of healing and/or regenerative processes. Pre-operative orthodontic treatment is designed to correct misalignment of the teeth and their relationship to the Alveolar bone. The methods of orthodontic treatment include orthodontic intrusion as well as orthodontic separation of the teeth.
This is the basic compact (hard) bone part of the upper and lower jaw. It carries the alveolar bone on top. It provides nourishment and support to the alveolar bone and teeth. The Basal bone contains vital veins and nerves. The Basal bone is a hard and durable bone. But, the risk of fracture of the Basal bone increases when teeth are lost from the alveolar bone.
The upper jaw bone (maxilla) and the lower jaw bone (mandible) provide support to soft tissues on a large scale and allow them to function properly. Between themselves they form a biting plan through the jaw joint (temporo-mandibular joint). Normally, the overlap between the upper jaw’s teeth and the lower jaw’s teeth should be slightly forward. The biting plan ensures that the teeth of the upper and lower jaws are in harmony with each other. It also ensures that they contact each other at the same time. Otherwise, even one tooth which is not in position can disrupt the whole bite plan between the two jaws.
Biting disorders in the jaw can occur for various reasons. Frequent causes are developmental disorders, traumas, genetic or racial traits. Other causes include inadequate habits such as finger sucking and prolonged bottle use, premature tooth extraction, delayed treatment of unequal teeth, and an extra large tongue. Less common causes are certain bone diseases, benign tumors, and vascular diseases (hemangiomas).
Patients with a poor bite plan may have many medical problems. These include speech disorders, respiratory disorders, premature tooth decay, gingival crevices, bad breath, and dysfunctions and pain in the jaw joint can be seen. For example, a person with a very small lower jaw may experience significant respiratory and sleep problems. These in turn can be associated with heart diseases. Those whose mouths are always open because their teeth do not close well often have deteriorated oral hygiene since they have problems with chewing and grinding their food.
Orthodontic treatment of the teeth in the alveolar bone segment can provide proper alignment of teeth and a good bite (occlusion). However, if the problem is in the basal bone, the alignment of the teeth is not enough to correct the bite. In such cases, the skeletal structure must be corrected at the basal level. This is accomplished by bringing the upper and lower jaws to their appropriate places by corrective by jaw surgery.
Patients who come for corrective surgery are first given detailed face and mouth examinations, and dynamic problems are examined during the movement of the jaw joint. The asymmetry (inequality of one side of the face to the other) is determined by the proportional evaluation of the volumes and dimensions of the different regions of the face (forehead, eyes, cheeks, nose, etc.) between the right and left sides. Differences in soft tissue lay-outs are investigated. Especially size of the lips and their dynamic positions when smiling are very important.
In corrective jaw surgery:
When we divide the face into three parts, each part ideally should be equal. Specifically, the base of the head (upper face), middle of the face (upper jaw-maxilla) and lower part of the face (lower jaw) are equal parts. This is called the golden ratio of Leonardo da Vinci. This gives us an idea clinically about the proportions and balance of the face within itself. The head: in healthy people the head is balanced on top of the spinal bones. If we consider the neck bones as the center of a balance, the weight of structures in the front part of the face should be approximately equal to the weight of the back part of the head. The reason that we have a smaller jaw than the nose, a more forward lower jaw compared to the upper jaw, and a head with a larger back than the front of the face is to protect the macro static balances of the head.
After the number of teeth, their individual positions, cavities, past treatments, dimensions of the tongue and volume are assessed, the dental relationship-biting (occlusion) of the lower and upper jaws is evaluated. In corrective jaw surgery, the upper anterior teeth (located at about 110 degrees to the upper jawbone) are in front of the lower anterior teeth (located at about 90 degrees on the lower jawbone) and overlap it slightly. This is how a natural bite is. This bite is medically called class I bite. Sometimes we can evaluate this bite according to canine (dog) teeth. If the upper teeth are in front of the lower teeth when the bite is examined, this bite is classified as class II (malocclusion); and if the lower teeth are further forward in comparison to the upper teeth, it is called class III malocclusion. Apart from this, the teeth have the same bite connections on the sides. The narrowness of a jaw can create the same problem by disrupting its relationship with the other jaw. While minimal biting and tooth alignment problems can be solved by orthodontic treatment alone, biting disorders related to upper and lower jaw skeletons (facial bone), facial and jaw asymmetries should be corrected with corrective jaw surgery.
Special x-rays (cephalometry graphs) are taken so that a more detailed examination can be done in patients who may need corrective jaw surgery. All skeletal structure of the head and face and positions of the teeth are evaluated with these graphs and it is investigated whether the problem is with the skeletal structure (i.e. ossicular bone) or with the dental structure (dental-alveolar) complex. In patients with biting disorders, the problem is both skeletal and dental. Cephalometric measurements are made by taking into consideration the ratio of the sizes of the upper, middle and lower face to the base of the head and the soft tissue (especially the cheeks and lips).
After radiology, dental plaster molds of upper and lower jaws are taken and pre-treatment situations of dental relations are determined. According to skeletal and dental problems, orthodontic treatment is started after a suitable surgical foresight.
Orthodontic treatment takes between 6 months and 24 months. Orthodontics should start after the age of 12 years old, when the last permanent teeth develop. Ideal timing can be done from 12 to 18 years of age until the age of jaw surgery. Because orthodontic treatment planning is very featured, it is very important that the surgeon knows the preparations and that this is done by experienced orthodontists and that the treatment is followed with intervals. Unplanned, poorly planned and poor orthodontic treatment can lead to major problems.
Sometimes patients are not adequately informed, and because of some orthodontists who do not have enough surgical experience, the teeth of patients with skeletal insufficiency at the bone level are tried to be corrected only by orthodontic treatment, which causes insufficient and bad results. In these cases, most of the teeth are turning back to their old positions. As tooth roots are excessively challenged, teeth are loose, gums are deformed, the aesthetic result is inadequate and similar problems are experienced all over again. In order to survive these problems, it is necessary to plan the treatment with an experienced orthodontist and to get advice from an experienced oral and maxillofacial surgeon. Orthodontic treatment that has been initiated improperly is often not possible to use as a bases for plastic or reconstructive surgery.
Corrective Jaw surgery (Orthognathic surgery)
Orthognathic surgery is usually performed after 17-18 years of age. It can be performed on anyone with a suitable jaw bone until advanced ages. For example, it can be performed on patients who are suffering from sleep apnea. For patients treated according to surgical planning and have completed orthodontic treatment, an acrylic plate called a bite plate is made before the jaw surgery. If surgery is to be performed in one jaw, 1 bite plate is prepared, if two jaws are to be operated, 2 bite plates are prepared. These are intended to provide the ideal position of the jaws during surgery relative to the base of the skull, and the ideal tooth correlation between each other (occlusion).
Corrective Jaw Surgery Techniques
There are three commonly used operations in orthognathic surgery.
Lefort I Surgery applied in upper jaw disorders;, Sagittal Split Surgery applied in lower jaw disorders; and Genioplasty Surgery applied in jaw disorders. All of these operations are performed under general anesthesia, each taking 1-2 hours on average. A 1-2 day hospital stay is enough. Recovery is usually between 1 and 3 weeks.
Lefort I Surgery;
This corrective jaw surgery is performed by making an incision between the upper lip and the upper jawbone inside the mouth, from the upper jawbone nose floor, through the root of the teeth. At this time, the upper jaw is only caught by the soft palate and is nourished by the vessels from it. The upper jaw-toothed bone segment then can be moved in three dimensions in order to find the ideal. The ideal is achieved by placing a previously prepared intermediate bite plate. The remaining part of the upper jaw is secured in the new position by means of mini-plates and screws. According to the needs of the upper jaw, all procedures such as embedding, sagging and rotation can be moved forward. The incision in the mouth is stitched with a self-dissolving thread and heals without any scarring. If there is a significant septum (nose) deviation during the operation, it can be corrected and the nasal tip can be somewhat reduced. Likewise, soft tissues can also be fixed on to the bone.
Mandibular Sagittal Split (longitudinal dissection of the lower jaw) Surgery:
According to what is required, this surgery is performed in order to bring the lower jaw back in skeletal disorders (deformities) of the lower jaw. Corrective jaw surgery is performed inside the mouth with a 3-4 cm incision made on the lower jaw bone behind the teeth on both sides without leaving a scar. There’s a nerve which passes through the lower jawbone (mandible), giving the lower lip a sense of lower teeth. This nerve is carefully preserved during the operation; the bone is horizontally separated into two as inner and outer folium. The nerve stays inside the inner folium and is checked whether it has been damaged or not. Very rarely, if the nerve is damaged, it will be repaired with a microsurgical technique (under the microscope). The bite plate prepared for the lower jaw is placed between the teeth and when the ideal location of the lower jaw and the bite is determined, the two bone foliums separated from each other are fixated together with a screw into their new position. The screws are placed in very small holes of 3-4 mm which open on both sides. The scars disappear after a while and do not become visible.
Chin Surgery (mentoplasty); the surgery is performed with a 3-4 cm incision made between the bones and the lips. The lower jaw bone is cut (osteotomized) so that the roots of the teeth are protected according to the structure of the defect. Meanwhile, the jaw bone segment, which feeds on the vessels from the muscles and becomes mobile, can be moved back and forward if there’s need, keeping it either hidden or exposed, or rotation can be done and the bone is fixated with mini plaques and screws. The incisions inside the mouth are not visible and are stitched with self-dissolving threads.
Care after Corrective Jaw Surgery
In patients who undergo corrective jaw surgery, pain relievers, antibiotics and treatments are used to reduce swelling in the face, as well as IV injections. It is very uncommon for the patient to be in intensive care. Food intake starts the next day with liquid foods. After the general condition of the patient is established, usually the lower and upper jaws are fixed to each other with elastic bands 2-4 days after the operation and the mouth is closed for 1-3 weeks. This makes healing of the bone safer.