Transverse mandibular deficiency with crowding of the mandibular anterior teeth is frequently manifested in patients with malocclusions. It is usually managed by orthopedic devices, extractions, interproximal reduction of tooth mass, and dental compensations (protruding incisors to increase arch length), sometimes limiting or compromising the final occlusal, periodontal and esthetic results. A new orthodontic surgical method has been developed to increase the mandibular intercanine distance based on gradual osteodistraction following a vertical interdental symphyseal osteotomy. After a seven day latency period a distractor device is activated 1 mm per day until the desired expansion is obtained. The appliance is then stabilized to maintain the distraction.

Twenty patients between 13 and 38 years of age (average 14.3 years) underwent distraction osteogenesis ranging from 4 to 14 mm of expansion with a mean of 7.7 mm.. The patients were followed for a minimum of 2 and a maximum of 10 years. A significant mandibular widening and proper dental alignment was achieve without extractions in all patients, with excellent osseous union, a healthy periodontal response, and absence of temporomandibular joint dysfunction. The V-shaped mandibular form was changed to U-shaped. There was exceptional patient compliance. The intraoral mandibular widening via distraction osteogenesis provides a reliable technique for mandibular expansion, offering the orthodontist a new alternative to manage patients with a transverse mandibular deficiency.

PRESURGICAL ORTHODONTICS

• Align and level the maxillary arch
• Obtain ideal maxillary arch
• Placement of rectangular surgical maxillary arch
• Fabrication of the intraoral distractor appliance
• Placement of the distractor appliance on the mandibular arch

POST-SURGICAL ORTHODONTICS

• Placement of lower anterior brackets
• Maintenance of the dental gap for 2 months with a plastic tooth
• Orthodontic mechanics are undertaken 2 months after surgery
• Periodically stripping of plastic tooth
• Mobilization of teeth into the distraction site
• Align and level, arch interdigitation and finishing followed by retention

METHOD AND MATERIALS

Twenty patients ( 14 women, 6 men, ages between 13 and 38) average 14,3 years old with transverse mandibular deficiency were treated by intraoral symphyseal osteotomy mandibular expansion and subsequent non-extraction orthodontic treatment, range of expansion from 4 to 14 mm mean 7.7. An intraoral tooth-borne hyrax distractor appliance was used to gradually widen the anterior part of the mandible. A vertical interdental osteotony was made between the central incisors in 14 patients, between central and laterals in 2 patients, and between lateral and canines in two others. 12 of the patients had simultaneous genioplasty by osteotomy of the inferior border of the mandible. All of the surgical procedure were accomplished under local anesthesia and intra-venous sedation in an ambulatory outpatient clinic.

SURGICAL TECHNIQUE

A horizontal incision is made with an electro-knife or scalpel 4-6 mm labial to the depth of the mandibular vestibule through the orbicularis muscle in the posterior aspect of the lower lip extending from canine to canine. The dissection is directed obliquely, posteriorly and inferiorly through the mentalis muscle until contact is made with the mandibular symphysis. The tissues are reflected inferiorly in a subperiosteal plane to the lower border of the mandible, were a channel retractor is placed. The tissues are reflected with a skin hook superiorly to the alveolar crest, care is taken to avoid tearing of the gingival tissue. Generally, once the flaps are reflected the roots can be seen or palpated. The inferior portion of the mental symphysis, below the level of the incisors, is completed with an oscillating saw blade. The labial cortical plate and alveolar bone below the level of the incisors apices are sectioned with a No. 701 fissure bur. The symphysis is sectioned into two halves by malleting a spatula osteotome into the partially sectioned interdental osteotomy site. The forefinger is used at all times to avoid any tearing of the lingual flap. Once the osteotomy is completed, the guide pin is inserted into the expansion appliance and activated. Expansion is continued judiciously. The gingival tissue, however should not remain blanched. Care must be taken to avoid tearing of the tissue because this might cause permanent periodontal problems.

RESULTS

Twenty patients underwent intraoral mandibular widening with tooth borne osteodistractor appliances. The mandible was expanded a mean of 7.7 mm (range 4-14 mm). Bony union which was observed in all patient based upon radiographic assessment of the distraction gap. Clinically, all procedures and appliances, placed on the teeth, were well tolerated. The post-operative course of the patients was uneventful, without evidence of infection or devitalization of teeth contiguous to the interdental osteotomy sites. All patients were treated in an ambulatory surgical setting without the need for hospital admission. 12 of the 20 patients underwent simultaneous genioplasties, which were fixed with a four-wire interosseous technique without complications. Two patients manifested temporo-mandibular pain and dysfunction during the stabilization period thought to be caused by occlusal instability. The symptoms disappeared after the patient's occlusion was refined orthodontically. Small amounts of mandibular expansion at the symphysis using osteodistraction techniques have been shown to produce an adaptive response within the mandibular condyle.

INDICATIONS

• Brodie Syndrome ( Scissors bite ): unilateral or bilateral.
• Severe lower crowding with normal maxillary arch and naso-labial angle.
• Severe maxillo-mandibular crowding with narrow smile (tunnel smile and Crocodile bite).
• Impacted anterior teeth due to a small mandible.

CONCLUSIONS

Mandibular widening by means of intraoral distraction osteogenesis is an easy, predictable and controlled method that creates new bone. It increases the intercanine distance so the Orthodontist can unravel anterior crowding without extractions. The surgery is performed under intravenous sedation on an ambulatory basis and requires minimal patient compliance. It has low morbidity and no donor site for bone grafting is needed. A strict protocol needs to be followed to avoid any complications including pre- surgical orthodontics, the method of osteotomy, incorporating a latency period, rate and timing of expansion, and stabilization period. This innovative technique opens new horizons for patients with a variety of clinical situations seen with mandibular transverse deficiencies.

Editors note: This image was digitally enhanced to illustrate the appliance

REFERENCES

1. Guerrero C. Rapid Mandibular expansion . Rev. Venez.Ortod 1990;48:1-2

2. Guerrero C, Contasti G. Transverse (horizontal) mandibular deficiency. In: Bell WH, ed. Modern Practice in Orthognatic and Reconstructive Surgery, vol.

3. Philadelphia: WB Saunders,1992: 2383-2402 3. Guerrero C, Bell W, Flores A, Modugno V, Contasti G, Rodriguez A, Meza L.; Distracción Osteogénica Intraoral Mandibular . Rev. Odont. Al Día. 1995;116-131 vol 11-2

4. Guerrero c, Bell WH, Contast G, Rodriguez A.. Mandibular widening by Distraction Osteogeniesis. British Journal of Oral and Maxillofacial Surgery. 1997. 35, 383-392.

5. Bell WH, Harper RP, Cherkashin AM, Samchukov ML. Distraction Osteogenesis to widen the mandible. British J. Oral Maxillofac. Surg 1997; 35: 11-19.