11.1 Indications

Key words: Angle class II/2, asymmetrical dental arches, incongruence of the dental arches, elongation of the anterior teeth, extreme deep overbite, overexpansion of the dental arch, segmental blood flow, skeletal open bite, small displacement distances, torqued dental arches, vestibular tilted dental arch segments

Indication for maxillary multisegmentation in the course of a Le Fort I osteotomy is usually incongruence of the maxillary dental arch with the mandibular dental arch with or without orthodontic pretreatment. It can have skeletal and dental reasons and occurs frequently. Predominantly, the maxillary multisegmentation serves a correction of the transverse deficit of the maxillary base, which can be clinically frequently characterized by a uni- or bilateral crossbite, rarely also by a vestibulo-occlusion. However, orthodontically overexpanded dental arches with a narrow bony base of the maxilla and hanging palatal molar or premolar cusps can also have the bony base widened and the excessive vestibular tilting of dental arch and bone segments reduced by sagittal bisection and expansion.

Indications for trisegmentation of the maxilla can be intramaxillary asymmetrical dental arches and/or torqued dental arches with partially elongated regions with vestibular nonocclusion or missing antagonists. Segmentation of the maxilla can be performed if the interradicular bone measures at least 3 mm, allows for an osteotomy gap, and can be individually designed according to dental/occlusal specifications. In daily practice, trisections of the maxilla with orthoradial alveolar ridge separations between the lateral incisor and canine are frequent, and sometimes also distal to the canines. In this case, the anterior segment can be tilted incisally or apically to correct inclinations, and the two posterior segments can be positioned symmetrically and leveled to each other. Indications for segmentation of the maxilla regularly occur when closing a skeletal open bite by tilting the anterior segment to level the dental arch. In the authors’ experience, successful four- or five-segment relocations can be performed in exceptional indications to coordinate the maxillary to the mandibular dental arch. Alternatively, single-tooth corticotomies may be considered (see Chapter 29).

Segment displacements must only be performed in the millimeter range so as not to disturb the dentoalveolar blood supply to the bone segments. Therefore, the nourishing soft tissue should also only be detached from bone in a limited manner.

If the displacement of maxillary segments exceeds the tolerable distance and the nourishing tissue/periosteum comes under too much tensile stress, there is a risk of necrosis. In this case, distraction osteogenesis (see Chapter 15) would have to precede as a separate procedure. Thus, an indication for transverse maxillary distraction has emerged for more than 5 mm expansion, which can be followed 12 months later by a Le Fort I osteotomy, if necessary with multiple sections of the maxilla.

11.2 Planning and model surgery

Key words: Bolton discrepancy, gap closure – orthodontic or prosthetic gap closure, interdental alveolar bone thickness, interdisciplinary planning, intraoperative transfer of model surgery, radiographic control, risk of tooth root damage

Early interdisciplinary planning of maxillary multisegment osteotomies entails concrete preparatory measures for orthodontic expansion of the tooth/tooth root distances in the maxilla. The interdental alveolar bone thickness should be at least 3 mm to be able to perform an osteotomy without harming the tooth roots. A radiograph or panoramic radiograph should always be used as a diagnostic tool for this purpose.

A current (panoramic) radiograph should also be available for the model surgery. The extent of segment displacement is limited because the nourishing periodontium can tolerate ≤ 3 mm of expansion. The positioning of the three plaster segments of the maxilla, which are positioned occlusally to match the mandibular dental arch, makes it necessary to grind down plaster edges of the segments in individual cases. If these planning measures are transferred intraoperatively to the bony segments, there is a risk of damage to osteotomy-related tooth roots due to removal of bone edges. It is essential to ensure that the plaster segments with maxillary teeth are placed congruent with the mandibular arch but with gaps between them during the model surgery. Gaps between the teeth close to the osteotomy can be easily closed orthodontically later after the osteotomies have healed.

In principle, proximal contacts can be easily made orthodontically. However, in some cases of Bolton discrepancies, gap closure is also contraindicated and prosthetic widening of the lateral incisors or canines by adhesive resin fillings is indicated in order to maintain the new intercuspidation and the planned anterior horizontal and vertical overlap. These are the key factors for long-term stability.

11.3 Methodology

Key words: bone harvest in the retromaxillary space, first surgical splint, flexible twist drill, glabellar circle measurement method, H-shaped cortical block, hypomochlion, large wire slings, maxillary bisection, maxillary cranial displacement, maxillary posterior displacement, maxillary trisection star-shaped or U-shaped, mobilization of palatal vascular nerve bundles, resorbable osteosynthesis materials

For preoperative injections, incision guidance, and glabellar circle midface measurement, see Chapter 10.

The initial situation is a downfracture of the maxilla. This is followed by exposure and displacement of the two large vascular nerve bundles until they are mobilized without tension within a distance of approximately 20 mm. Since these vessels are largely responsible for the blood supply to the lateral maxillary segments, this surgical step must be performed very carefully. If damaged, there is a risk of reduced blood flow to the maxillary segments. The adjacent bony structures of the posterior wall of the maxillary sinus are then shortened or even removed, depending on the planned direction of displacement of the maxilla, in order to allow the maxilla unrestricted mobility for cranial (frequent) or even posterior (rare) displacement. Extensive preparation of the vascular nerve bundles may also be necessary in the case of a supposedly minor maxillary anterior or caudal displacement with bone interposition, since the subsequent individual displacement of the segments may require additional space that is difficult to estimate.

Osteotomies to divide the maxilla in two are preferably performed paramedian lateral to the nasal crest because the palatal mucosa is thicker and less likely to be perforated than in the median. They are performed sagittally from the posterior margin of the nasal floor (or hard palate) anteriorly to the alveolar process. In the past, this osteotomy was performed with the Lindemann burr under digital counterpressure from the palate; today, it is increasingly performed piezoelectrically without perforating the mucosa with digital counterpressure with the index finger. Since the bony nasal crest shifts laterally in the case of transverse expansion, especially in the case of posterior maxillary expansion, and can narrow the inferior nasal meatus on one side, in such cases it should be completely ablated on both sides down to the level of the nasal floor so that the septum can then automatically readjust medially. To preserve the anterior nasal spine, the osteotomy is passed laterally around and cuts the alveolar ridge interdentally between the central incisors.

For the trisection of the maxilla, U-shaped osteotomies of the hard palate are usually performed in addition to the above-mentioned paramedian sagittal (star-shaped) osteotomies (Fig 11-1). The star-shaped maxillary osteotomy is again performed sagittally paramedian as in the maxillary bisection. The U-shaped osteotomy is formed from bilateral paramedian sagittal osteotomy clefts that are connected anteriorly in a semicircular fashion. The bony nasal crest should be shortened to nasal floor level in a star-shaped osteotomy, otherwise it will shift paramedially during transverse stretching and reduce the nasal space (see Fig 11-2g). In a U-shaped osteotomy, the crest remains mobile in the median, merely pedicled to the palatal mucosa (see Fig 11-2d).

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