A surgical rearrangement of the positional relationship of the jaws is referred to as rearrangement osteotomy of the jaws (maxillomandibular osteotomy; maxillomandibular rearrangement osteotomy, MMO). A distinction is made between the realignment of only one jaw – i.e. the upper or lower jaw – and the bignath realignment osteotomy, in which both jaws are operated on. A jaw that is normal in size and position with a resulting normal tooth position is called eugnath.If there are discrepancies or deviations of the teeth or jaws, we speak of dysgnathia. Pronounced dysgnathia (malocclusion of the jaws), however, not only affects the appearance, but also the well-being and state of health of the entire craniomandibular system (jaws, temporomandibular joints, chewing and facial muscles). The chewing process can be significantly more difficult. Hurtful behavior by fellow human beings can also contribute to an enormous reduction in quality of life. If there is a pronounced form of dysgnathia that cannot be satisfactorily treated by orthodontic treatment measures alone, the surgical realignment of one or both jaws, the realignment osteotomy, is the means of choice to not only optimize the function of the masticatory system, but also to achieve a harmonious appearance and thus decisively improve the quality of life. Dysgnathia can be caused by diseases or malformation syndromes, such as:
- Pfeiffer syndrome (synonym: Pfeiffer’s disease): rare, autosomal-dominant inherited disease; it belongs to the craniofacial malformations (short skull, flat back of the head, large interpupillary distance underdeveloped midface, broad, outwardly directed terminal phalanges of the thumb and big toes).
- Crouzon syndrome (synonym: Crouzon disease): acrocephalosyndactyly syndrome with malformations of the bony skull and phalanges).
- Goldenhar syndrome (synonym: oculo-auriculo-vertebral dysplasia, OAV): congenital malformation of unclear etiology; it usually affects only one side of the face and is characterized by a malformation of the auricle, chin displaced to the affected side, unilateral higher corners of the mouth, an enlarged eye or a missing eye)
- Cleft lip and palate (LKG clefts).
However, acquired causes such as early deciduous tooth loss, habits (harmful habits such as sucking), mouth breathing, or trauma (injury) can also cause dysgnathia.
Indications (areas of application)
Dysgnathia surgery may be performed for a variety of reasons, such as:
- Pronounced discrepancy between the jaw bases.
- Clearly open bite
- Clearly recognizable disharmony of the facial profile
- Mandibular prognathism – pronounced reverse anterior overbite, the base of the lower jaw is too far forward in relation to the base of the upper jaw, the lower incisors bite in front of those of the upper jaw.
As a rule, surgical intervention is always performed only when the limits of orthodontic therapy have been exhausted.
Before surgery
Surgical intervention is embedded in a comprehensive therapy concept that begins with thorough planning using clinical and radiographic examinations. A cephalometric lateral radiograph (FRS) is used to determine how pronounced the discrepancy between the jaw bases is. Prior to the procedure, preparatory orthodontic treatment is necessary, which can last up to 18 months. The goals of this combination therapy are to establish a harmonious occlusion (fit of teeth to each other) and to harmonize the facial profile. In addition, surgical intervention is preceded by waiting for growth to complete. Otherwise, further growth could negatively affect the painstakingly achieved result. For an operation planned in the lower jaw, the wisdom teeth must be removed at least three months beforehand, as they lie in the operating area of the realignment osteotomy. If the operation is finally imminent, a so-called splint is made preoperatively in the dental laboratory – a plastic splint with which the upper and lower jaws are connected intraoperatively (during the operation) in order to secure their position, the desired interlocking and the position of the condyles (temporomandibular joint heads). The individual phases of combined orthodontic and maxillofacial surgical therapy include:
- Orthodontic pre-treatment – decompensation, duration depending on individual situation 6 to 18 months.
- Surgery – adjustment osteotomy
- Orthodontic fine adjustment
- Stabilize the treatment result – Retainment
The surgical procedure
The repositioning osteotomy is performed under general anesthesia and involves an inpatient stay of several days. To move the upper jaw to a new position, it is detached from the facial skull above the roots of the teeth (Le Fort I osteotomy) and fixed in a more anterior or posterior position, depending on the situation, using plates and screws. To bring the mandible into the desired position, the sagittal osteotomy according to Obwegeser and Dal-Pont is often performed. Here, the mandible is split in the ramus ascendens (in its ascending branch) retromolar (behind the molars) to such an extent that it is possible to bring the jaw into an optimal position. The lower jaw is also fixed in its new position by means of plates and screws. The splint fixes the upper and lower jaw in their position in relation to each other.
After surgery
The healing phase of the surgery is followed by the second phase of orthodontic treatment to fine-tune tooth positions and thus occlusion (final bite and chewing movements). If tooth movements are no longer necessary, the treatment result is secured in the long term in the so-called retention phase or retainment. For this purpose, retainers (wires), for example, are adhesively fixed (bonded) to the oral side (back) of the upper and lower incisors.The plates inserted during the adjustment osteotomy are removed again in a second surgical procedure after bone healing is complete.
Possible complications
- Injury to nerves with signs of paralysis, loss of sensitivity, numbness – e.g., mandibular nerve.
- Opening of the maxillary sinus in the upper jaw.
- Injury to teeth
- Infections
- Wound healing disorders
- Pseudarthrosis – formation of a false joint.
- Et al