Intra-Arch Distraction

Maxillary and mandibular widening

Mandibular-maxillary deficiency is one of the most common dentofacial deformities. This problem can present in the three dimensions of space: (1) anteroposterior, (2) vertical, and (3) transverse. It also may be combined with other maxillary alterations. In the past, the treatment of this dentofacial problem consisted of either integrated orthodontic-surgical treatment, or orthodontic dental compensations alone. The key to a correct diagnosis of the facial growth alteration is a comprehensive evaluation: the three-dimensional assessment of vertical, anteroposterior, and transverse skeletal and dental positions, and soft tissues. Cephalometric analysis should be performed for every patient to combine the surgical procedures needed to correct the deformities in one surgical intervention. The orthodontist should evaluate the patient for potential initial preoperative orthodontics, root divergence, and prediction for future orthodontic treatment. This new surgical philosophy treats the deformity through calibrated stimulation of the bone: the combination with orthodontics and surgery to correct certain deficiencies of the jaws.

Maxillary widening

When maxillary widening is needed, a tooth-borne appliance is placed 1 day presurgically, a Le Fort I osteotomy, with a complete downfracture going through the tuberosity instead of through the pterygomaxillary junction. A midline osteotomy is accomplished taking in consideration the nasal structures when the maxilla undergoes a three-dimensional movement, or an asymmetric distraction to correct an occlusal asymmetry ( Figs. 1–10 ). The distraction protocol consists of a 7-day latency period, activation phase at a rate of 1 mm per day until desired movement is obtained, an immediate placement of an acrylic tooth added to the orthodontic arch at the distraction site, and switching the dental-borne appliance by a transpalatal bar for a 5- to 7-month consolidation period.

Fig. 1
A 21-year-old woman presenting with anteroposterior, vertical, and transverse deficiencies; severe maxillary crowding; and class III malocclusion and negative upper teeth exposure. The maxilla was advanced 6 mm, widened 8 mm, and inferiorly moved 3 mm in a single surgical stage. Facial features after the surgical movements. Follow-up photographs after combined three-dimensional maxillary repositioning before surgery ( A ) and 5 years later ( B ).

Fig. 2
Smiling photographs showing a wider postoperative smile and better teeth exposure. Nasal width was controlled by detailed cinch closure; the upper vermilion projection was maintained by muscles approximation and V-Y closure. Note the disappearance of tunnel smile and no need for premolar extractions.

Fig. 3
Calculation of movements is based on radiographs, dental models mounted in an articulator, occlusograms, and cephalometrics. Note the surgical photograph. Flexible 1.5-mm width plates are used at the piriform rims and posterior skeletal suspension The 0.024-gauge wires permit slight changes postsurgically either by tightening or releasing the wires. A periosteal elevator is placed in the midline, between both fragments, and light pressure is exercised to widen the superior aspect of the osteotomy as the plates are fixated. The plates already have a step with the lateral and anteroposterior calculated repositioning.

Figs. 4 and 5
The initial dental photograph with anterior and posterior crossbites, severe crowding, and semi-impacted upper canines. As the maxilla is advanced and widened, the posterior teeth positioning improves, and the space created in the midline by distraction osteogenesis is used to eliminate the crowding. An acrylic tooth is placed in the mid-line to avoid early dental movement into the distraction site and avoid periodontal and endodontic problems. The pontic is grinded 1 mm per month per side, starting 2 or 3 months after surgery, once the mineralization is adequate. At 7 months postsurgical the distraction space must be totally closed, achieved by controlled dental movements.

Fig. 5

Figs. 6 and 7
Occlusal views showing dental movements. The distraction device should not be removed before 3 months; the bone healing process is faster than the soft tissues. Distraction appliance removal is followed by an immediate transpalatal bar between the first molars. This bar is maintained in place for the remaining of the orthodontic treatment. The palate mucosa is quite strong and tries to return to the original length and positioning. It takes 10 to 12 months for complete soft tissue healing.

Fig. 7

Figs. 8 and 9
The frontal radiographs are an important tool to diagnose and follow-up the transverse changes in distraction osteogenesis to widen the maxilla. The new maxillary positioning allows the orthodontist to locate the anterior teeth properly. Note that the mandibular presurgical orthodontics was completed before the distraction device was fixed to the maxillary molars. Once the surgery is scheduled, the orthodontist and surgeon agree on the amount of millimeter widening needed, and because no braces are used presurgically in the maxilla, there are no undesirable dental movements, especially moving the premolars out of the alveolar bone or lateral inclinations. At his moment the appliance is fixed to the molars and the remaining of the maxillary braces are fixed.

Fig. 9

Fig. 10
Lateral radiographs show only maxillary anterior and inferior repositioning. Even though the SN-1 was augmented, the facial and smiling esthetics are adequate and no extractions were performed, other than the third molars.

A three-dimensional treatment can be planned for the maxilla in one single stage. The age of treatment is based on three major considerations: (1) the canine eruption level, (2) the anatomic situation of the infraorbital nerve, and (3) the nasolachrymal duct. Patients with bidimensional or three-dimensional maxillary deficiencies can be treated by intraoral distraction osteogenesis to lengthen, widen, or augment vertically the maxillomalar complex at different osteotomy levels according to the individual clinical situation. Complete radiographs and photographs are obtained presurgery, immediately postsurgery, 3 months later, at the appliance removal stage, and 6 months after braces are removed. Dental models in an articulator should be taken before the surgery and after removal of braces.

These patients should undergo a combined surgical-orthodontics treatment ideally to correct the tridimensional problems. In those requiring a high Le Fort I, a conventional incision and osteotomy is accomplished, the maxilla is freely moved, and distractors are placed bilaterally anchored to the base of the zygoma and fixed to the maxilla with the adequate vector based on the three-dimensional planning. A modified Le Fort III has an additional transconjunctival approach: the osteotomy divides the malar process, runs medially above the infraorbital nerve, the orbital floor is sectioned behind the infraorbital rim continuing underneath and obliquely anterior to avoid the nasolachrymal duct reaching the piriform rim, and posteriorly extended to the pterygo-maxillary suture. Finally, two wide-curved osteotomes are placed behind the maxillary tuberosities to displace the malar-maxillary complex. Once it is completely freed, the distractors are fixed, the posterior bar is screwed to the zygoma with 2.0 screws, and the anterior bar is fixed to the maxilla above the teeth.

Mandibular widening

The severe crowding in a patient is usually part of a micrognathia, which includes a deficiency in growth in all three planes with skeletal and dental problems. In the past, dental crowding was treated by compensatory orthodontics and dental extraction, obtaining unstable results or extremely narrow dental arches with tunnel smiles ( Figs. 11–22 ). Because the functional matrix dictates the development of both maxilla and mandible, it is predictable that most of cases with skeletal class II and narrow arch present a problem with the maxilla. It is imperative to make a three-dimensional analysis to provide correct three-dimensional treatment.

Jan 23, 2017 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Intra-Arch Distraction
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