INTRODUCTION

Anterior open bite is one of the most difficult malocclusions to treat orthodontically. The most effective treatment option in adult patients requires surgical repositioning of the maxilla/mandible or both jaws.12 Other treatment alternatives include the use of bite blocks,3 high-pull headgear,4 extraction therapy,5 multiloop edgewise archwire therapy,67 and intermaxillary elastics.8 Recently, skeletal anchorage has gained interest because of its ability to provide absolute anchorage. For this purpose, dental implants,9 miniplates,10–13 miniscrews,14 and microscrews1516 have been used.

Studies have reported successful treatment of open-bite cases with miniplate anchorage.101213 These can provide stable anchorage without the need for the patient's cooperation and allow reliable orthodontic tooth movement.1718

Combined treatments also exist, including surgery and orthodontic appliances. Corticotomy-facilitated orthodontic treatment allows reduced treatment time, and the adverse effects of the orthodontic treatment are limited.19 Chung et al20 reported the use of corticotomy to help molar intrusion. Likewise, Kanno et al21 applied corticotomy and compression osteogenesis in the posterior maxilla to treat a severe anterior open-bite case by 2-stage surgery. This report presents accelerated orthodontic treatment in a severe anterior open-bite case with osteotomy-assisted maxillary posterior segmental impaction using zygomatic miniplate anchorage by 1-stage surgery.

CASE REPORT

A 14-year-old female patient was referred with a complaint of chewing and esthetic problems (Figure 1). Clinical examination revealed a convex profile due to a retrognathic mandible. A severe anterior open bite with an overbite of −5 mm and an overjet of 5 mm were present. Both sides revealed a Class I molar and canine relationship. Mild crowding was present in both arches. Dental hygiene was proper. Compared with Turkish norms,22 the cephalometric analyses showed a skeletal Class II relationship (ANB angle, 8°; norms, 2.65 ± 1.63°) with mandibular retrusion (SNB angle, 68°; norms, 79.92 ± 3.44°). The mandibular plane angle was steep (SN-MP angle, 53°; norms, 31.66 ± 5.25°). The inclination of maxillary and mandibular incisors was normal (U1-SN, 98°; norms, 102.07 ± 9.73°; and L1-MP, 95°; norms, 96.50 ± 7.50°). The maxillary molars were extruded (U6-PP, 25 mm; norm, 23 mm)23 (Figure 2, Table 1).

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Table 1.  Angular and linear cephalometric measurements

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Treatment Progress

The treatment plan included impaction of the maxillary posterior segment using a zygomatic bone anchorage. Surgical assistance was considered to accelerate the treatment and minimize the adverse effects of orthodontic treatment. The patient was fully informed about the procedures.

The first and second upper molars were banded, and a transpalatal arch appliance was prepared to prevent buccoversion of the posterior teeth during the intrusive force application (Figure 3).

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The surgical procedure was performed under local anesthesia with Ultracain DS-forte (Aventis Pharma, Istanbul, Turkey). A horizontal incision was performed above the attached gingiva from the canines towards the tuber maxilla. Full-thickness mucoperiosteal flaps were elevated, taking care not to expose the buccal fat pad. The principle of osteotomy was to create adequate bone gap that would avoid frictions between bone edges during impaction. The horizontal osteotomy was performed 5 mm above the apices of molars with a 2-mm diameter tungsten round bur under saline irrigation. The resulting gap was 2.5 mm. Initial guide bone cuts for anterior and posterior vertical osteotomies were performed with a diamond disk (FRIOS MicroSaw Diamond disk, Friadent, Mannheim, Germany) with a cutting depth of 3.2 mm and a width of 1 mm. An anterior vertical bone cut was performed between the first molars and second premolars 3 mm above the interdental alveolar margin. A posterior vertical bone cut was prepared on the lateral side of the upper third molar extraction gap, which was removed during the operation.

The horizontal palatal bone cuts were carried out through the buccal osteotomy gaps. To weaken the resistance of palatal bone, an initial guide corticotomy was achieved using round bur. This helped prevent the possible damage of palatal mucosa and vascular bundle. The osteotomies were completed by horizontal and vertical palatal osteotomies with a thin custom-made spatula osteotome. All of the bone gaps were 1–1.5 mm, except the buccal horizontal osteotomy (Figure 4). The miniplates (Surgi-Tec, Brugge, Belgium) were mounted on the zygomatic buttresses (Figure 5). After bleeding control, the incision sites were closed with resorbable sutures. No surgical complications were observed in the follow-up period.

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The miniplate was loaded 1 week after the surgery to reposition the corticotomized posterior segment with a force of 250 g by nickel-titanium (Ni-Ti) closed coil springs. The force was applied from the miniplate to the upper first and second molar buccal tubes (Figure 6). The intrusion was completed 2.5 months after the surgery (Figure 7). Afterward, the fixed appliances (0.018-in slots) were placed, and a 0.014-in Ni-Ti archwire was also placed. The posterior segments were attached to the miniplates by ligature wire throughout the treatment to prevent possible relapse. After the alignment of anterior teeth, 0.016 × 0.022-in Ni-Ti archwire was placed, and anterior elastics were used for the stability of the overbite. The orthodontic treatment was finished with 0.017 × 0.025-in stainless steel archwires. The whole treatment lasted 12 months, and optimal occlusion was obtained. At the end of the treatment, the patient was instructed to wear Hawley retainers. The bone anchors were removed under local anesthesia, and complete bone healing was observed at the operation sites without any bone gap remaining.

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RESULTS

The anterior open bite was closed after intrusion of the maxillary posterior teeth, and a well-aligned dentition was obtained (Figure 8). The cephalometric changes are shown in Table 1.

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Soft Tissue Changes

A decrease of 1° was found in the angle of Ns-Sn-Pos, reflecting the slight improvement in the convex profile. Accordingly, the Z angle showed an increase of 1.5°. The upper lip-E plane was decreased slightly from 0 mm to −1 mm. The lower lip-E plane was decreased 0.5 mm.

Pretreatment and posttreatment cephalometric superimpositions (Figure 9A, B) revealed intrusion of the maxillary posterior teeth, labioversion of the maxillary and mandibular incisors, slight extrusion of the mandibular molars, and a closing autorotation of the mandible. No dental or periodontal problems and complications related to surgery were detected during the overall treatment (Figure 10).

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DISCUSSION

Several options to treat anterior open-bite cases have been reported.124–821 Posterior intrusion is reported to be more stable and improve esthetics better than extrusion in skeletal open-bite cases.1516 When the intrusive force is applied by the fixed appliances, the adjacent teeth will extrude, and a clockwise rotation of the mandible can occur.24 The use of corticotomy was suggested to reduce root resorption and loss of tooth vitality as well as to shorten the treatment time.25

In the present case, the patient had a long face with a skeletal open bite. To intrude the maxillary posterior teeth, the resistance of the cortical bone is reduced by a modified osteotomy. The main purpose was to reduce the treatment time. Adequate gaps were created horizontally and posteriorly for the required intrusion to achieve rapid movement of the block of teeth. In conventional corticotomy techniques, both labial and lingual cuts are included.1926 In this case we preferred a 1-stage surgery to reduce the total operation and orthodontic treatment time. In our technique, the palatal bone cuts were performed through the buccal osteotomy gap. The main reason why we kept the palatal mucosa intact was to protect the vitality of the osteotomized segment. After the surgery, no problems related to teeth or periodontal health were found.

Kanno et al21 applied a 2-stage surgery in which they set an anchor plate in the center of the hard palate. Three weeks after the first stage, they placed another anchor plate to the zygomatic buttress area. We used a transpalatal arch to avoid tilting of the posterior segment to the buccal side and avoid an extra operation.

Classical corticotomies exclude the marginal bone from the operation site to protect the crestal bone and periodontal membrane.27 Chung et al20 emphasized that vertical bone cuts began 2–3 mm above the interdental alveolar margin. Our clinical and radiographic examinations revealed that periodontal structures were protected.

There are reports of the stability of miniplate anchorage in open-bite cases.1017 In this case, the intrusion force was 250 g, which is more than was used in previous studies.162829 Kalra et al30 used 90 g per posterior tooth for intrusion in growing patients. Moreover, they pointed out that there are no reports regarding the optimal force value to be applied after corticotomy. As the resistance of the cortical bone was removed by the osteotomy, we applied higher forces more reliably. At the completion of the intrusion, panoramic radiographs showed no marked apical root resorption.

In the current case, the intrusion time was less (2.5 months) than in other studies in which miniplate anchorage was performed without corticotomy.1217 Sherwood et al12 found a mean intrusion of 1.99 mm in 5.5 months. Another study revealed an average of 2.6 mm maxillary molar intrusion in 5.1 months.17 In addition, Sherwood et al18 reported 4.0 mm intrusion in 6.5 months. On the other hand, 2.0 mm of maxillary molar intrusion has been achieved in 3 months with corticotomy assistance.20 Kanno et al21 achieved a 7 mm superior repositioning of the maxillary posterior segments in 2 months after a 2-stage corticotomy. They applied forces from both buccal and palatal sides. However, we achieved 4.0 mm intrusion by the assistance of a 1-stage surgical procedure, which we believed to be critically important in protecting the vitality of the corticotomized segments. Recently it was stated that tooth movement increased at least 2 weeks after corticotomy applications, which depends on the rapid alveolar bone reaction, leading to less hyalinization of the periodontal ligament.31

The rapid tooth movement after corticotomy relies on 2 different views.2632 The first was based on the movement of bony blocks. The latest view was described as the accelerated bone turnover and decreased regional bone-density phenomenon (RAP). Wilcko et al26 presented cases with corticotomy-facilitated orthodontics and periodontal alveolar augmentation and obtained pretreatment and posttreatment computed tomography to clarify the mode of movements. Their results demonstrated a demineralization-remineralization phenomenon rather than bone block movement.

Although the nature of rapid tooth movement in this case is not clear, a RAP effect might have occurred at the palatal site as interdental alveolar bone margin was kept intact during impaction of the whole segment. Our rationale was to create an adequate bone gap that would prevent friction of the bone blocks with the surrounding bony structures during impaction. The whole process could result in a telescoping impaction without bone resistance in a shorter time. Therefore, a larger bone gap on the buccal surface would overcome the side effects of surface irregularities and possible delays in treatment time. Additionally, the slight concavity of palatal bone required a thinner gap.

Previous studies reported that the profile improvement was poor by the intrusion of molars in 1 jaw, which was related to the unwanted extrusion of molars in the opposite jaw.1012 Accordingly, 1 mm extrusion in lower molars could have been prevented by simultaneous bonding of the lower arch. The esthetic improvement was limited in this case. The counterclockwise rotation of the mandible caused only a slight advancement in the profile reflected by the slight decrease in Ns-Sn-Pos and the increase in Z angle. We planned to discuss further treatment options with the patient, such as an advancement genioplasty to improve the facial profile.

One important factor in this case was the growth potential of the patient, which should be considered for the relapse tendency and the functional adaptation of the musculature. A recent report revealed that 30% of mandibular molar intrusions relapse during the first year of retention.33 For this reason, we considered a long-term follow-up, use of a positioner, and muscle exercises.28 Although the facial profile after the treatment was less than we desired, the patient won her self-reliance and gained function, and that was another satisfactory result for us.

CONCLUSIONS

• Miniplates are stable skeletal anchorage units to achieve molar intrusion.

• The 1-stage surgical procedure demonstrated that osteotomy-assisted impaction using zygomatic miniplate anchorage is a technique that has the advantage of reduced treatment time.