INTRODUCTION

Anterior open bite is one of the most difficult malocclusions to treat and maintain in orthodontics. The morphologic pattern in anterior open bite is characterized by longer vertical dimensions, an increase in development of the maxillary posterior dentoalveolar structure and a steep mandibular plane.1–3 The surgical correction of skeletal open bite often requires maxillary impaction to achieve counterclockwise rotation of the mandible and subsequent reduction of anterior facial height.4 The complexity, the risks, and the cost factor of surgical treatment have initiated a search for alternative clinical procedures.

Bite-blocks with repelling magnets5–7 or spring-loaded bite-blocks8 have been applied to achieve dentoalveolar intrusion of the maxillary posterior segments. Fixed mechanics and vertical elastics have also been used to treat anterior open bite.9–12 Face mask designs have been developed for posterior dentoalveolar intrusion.13 These procedures have been effective in passive intrusion of the maxillary posterior segment5–71314 or in anterior dentoalveolar extrusion.9–12 In all these treatment modalities, however, the correction was achieved primarily through extrusion of incisors or by preventing passive eruption of posterior teeth.

Recent studies have used osseointegrated implants and screws as anchorage units for orthodontic purposes.15–21 In patients not in need of implants for prosthetic reasons, investigators have used the retromolar area,22 palatal region,23–30 or alveolar areas31 to attach various screws and plates solely for the purpose of orthodontic movement of teeth or segments.

Ohmae et al,32 using an animal model, and Umemori et al33 in humans, applied titanium mini plates to the mandibular corpus area and used them as anchorage for intrusion of the mandibular posterior dentoalveolar segment for correction of anterior open bite. Sugawara et al34 used a specially designed skeletal anchorage system (SAS) for correction of anterior open bite by intruding the mandibular molars in humans. Melsen et al,35 De Clerck et al,36 Erverdi et al,37 and Sherwood et al38 reported zygomatic anchorage as an alternative form of maxillary posterior anchorage.

Studies35–38 have shown that the zygomatic buttress area could be a valuable anchorage site to get effective intrusion of the maxillary posterior segment. This preliminary study reports the results of the use of zygomatic buttress anchorage to intrude the maxillary buccal dentoalveolar segment to correct skeletal open bite in nongrowing patients.

MATERIALS AND METHODS

Case selection

This preliminary study involved 10 patients 17 to 23 years of age. Five of the patients had Class I occlusion, and the other five patients had a Class II malocclusion. Six patients were treated with upper first premolar extractions, and the other four patients were treated with a nonextraction treatment approach. A mean of −0.6 mm anterior open bite was present. Lateral cephalograms and posteroanterior radiographs were taken before and after the treatment. Twenty-four measurements were made on each lateral cephalogram to assess the dental, skeletal, and soft tissue changes, and one measurement was made on the posteroanterior cephalograms to assess the buccal tipping of maxillary molars. (Figures 1a,b and 2).

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Surgical method

The surgical method as described by Erverdi et al37 was used. After rinsing the mouth for one minute with 0.2% chlorhexidine gluconate, a local anesthetic was infiltrated bilaterally at the zygomatic process areas. Initially, we used a horizontal sulcular incision as in the surgical method (Figure 3a,b); currently we use a vertical incision instead to simplify the surgical operation, reduce the size of the scar tissue, and enhance the healing process. A one-cm vertical incision was made along the zygomatic buttress and ending at the mucogingival junction. By means of blunt dissection, the zygomatic process of the maxilla was totally exposed. An I-shaped titanium miniplate (Leibinger, Mühlheim-Stelten, Germany) was adjusted to fit the contour of the lower face of each zygomatic process and fixed by two bone screws (length seven mm), with the long arm exposed to the oral cavity from the incised wound. Initially, we intended to use long screws (seven mm) to stabilize the plates. Presently, however, we use five-mm screws, which are long enough to keep the plate in place. The last helix of the screw was exposed to the oral cavity from the mucogingival junction. This surgical method was chosen to reduce the inflammation and minimize discomfort to the patient caused by the movement of the cheeks. The exposed hole in the plate was used to directly receive the intrusive force. The wound was closed and sutured. During the healing period, instructions were given to the patients on how to clean the wound area. Four to seven days later the sutures were removed and force was applied to the miniplates. Figure 4 shows an anteroposterior radiograph, the location of the plates, and application of closed coil springs to deliver an intrusive force.

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Orthodontic treatment

All patients received a transpalatal arch constructed from 0.9 mm stainless steel round wire and adapted three mm away from the palate. The anterior and posterior teeth were aligned with the help of two posterior and one anterior segmental wire. After the initial alignment, nine-mm Ni-Ti coil springs were placed bilaterally between the hole of the mini plate and the first molar buccal tube (Figure 5a,b). The anterior open bite was corrected in a mean of 5.1 months. The biomechanics of the force system is presented in Figure 6.

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Molar intrusion was retained with vertical wire ligation between the tube of the molar bands and the miniplates throughout the subsequent orthodontic treatment (Figure 7a,b). One month before debonding, the plates were removed. The total treatment duration was a mean of 18.3 months.

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RESULTS

Our results showed that the anterior open bite was corrected in all our patients. The correction was achieved with a clockwise rotation of the mandible (an average of 1.7° [P < .01]), maxillary molar intrusion (an average of 2.6 mm [P < .01]), maxillary incisor retroclination and extrusion (an average of 9.6° [P < .01]), and extrusion of 1.1 mm (P < .01). The mandibular incisors were extruded an average of 1.1 mm (P < .01) because of the leveling of the dentition in the mandible. The orientation of the palatal plane did not change, however, and the occlusal plane rotated in a clockwise direction a mean angle of 3.1° (P < .01). The measurement made on the posteroanterior cephalograms showed that the maxillary molars were slightly tipped buccally, an average of 2.8° (P < .01). A radiographic analysis of the treatment results is presented in Tables 1 and 2.

TABLE 1. Comparison of Initial and Final Skeletal Measurements (in degrees)

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TABLE 2. Comparison of Initial and Final Dental Measurements

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Synopsis of patient treatment

SE was an 18 years 1 month–old female individual who presented with a symmetrical frontal facial appearance, a “gummy” smile in the posterior region, and a slightly convex profile (Figure 8a–c). Intraorally, she presented with a Class I molar and canine relationship with a maxillary dentoalveolar constriction and three mm of anterior open bite (Figure 9a–c). Our treatment plan was to use skeletal anchorage for molar intrusion and fixed appliance therapy. The results showed that a 3.0-mm anterior open bite was corrected and 2.0 mm of overbite was achieved in five months (Figure 10a–c). Because of the force application on the buccal side of the posterior segment, the dental posterior maxillary constriction was eliminated. After achieving good interdigitation, ideal overbite and overjet were achieved and the braces were removed.

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At the end of the treatment the patient's smile and profile were significantly improved. The posterior gummy smile was eliminated. Extraoral and intraoral pictures of the patient at the end of fixed orthodontic therapy are presented in Figures 11a–c and 12a–c. Initial and final lateral cephalometric radiographs and superimpositions showed the improvement of the anterior open bite, clockwise occlusal plane rotation, and intrusion of the maxillary molars (Figures 13a–c). The initial and final panoramic radiographs showed a flattening of the maxillary occlusal plane (Figure 14a,b).

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DISCUSSION

The present study shows that the use of zygomatic miniplates is an effective and minimally invasive surgical procedure to correct skeletal anterior open bites. The benefits of this treatment as an alternative to conventional orthodontic appliances such as extraoral appliances1339 (headgear) and/or intraoral mechanics9–11 (anterior box elastics) are significant.

To improve the esthetics and achieve stable treatment results in the anterior open bite, high angle growth pattern, and excessive posterior growth patient, molar intrusion should be the treatment goal. The literature shows that overerupted posterior teeth are significant contributors to anterior open bite.1–3 Investigators have used occlusal blocks and repelling magnets6–7 to slow dentoalveolar posterior growth and intrude the maxillary posterior teeth to correct anterior open bite.

Kim11 criticized the use of headgear for molar intrusion. He advocated extraction of the second and third molars and application of multiloop arches and anterior elastics to upright mesially tipped molars. However, their findings showed uprighting of the maxillary molars but not intrusion. In another study, the investigators evaluated the changes in dentofacial structures of open bite patients treated with mesially accentuated–curved and mandibular reverse–curved nickel titanium archwires and intermaxillary elastics. The results of this study show that the bite closure was achieved primarily by extrusion of the mandibular incisors and uprighting of the maxillary incisors.12 Although the configuration of the archwires in the molar region was aimed at intruding and uprighting the molars, no molar intrusion took place. Instead, the molars were extruded while being uprighted. This technique closed the anterior open bite mainly by extruding the anterior segment.

The present study showed that 3.7 mm of anterior open bite was corrected by 2.6 mm maxillary molar intrusion, 1.1 mm maxillary and mandibular incisor extrusion, 3.1° clockwise rotation of the maxillary occlusal plane, and 1.7° counterclockwise rotation of the mandible. In summary, 40% of the anterior open bite correction was achieved with autorotation of the mandible and 60% with extrusion of the incisors. The smile and the profile of the patients were improved, and good function and esthetics were achieved in a short period of time.

Dental implants have been used successfully for fixed orthodontic anchorage.23–30 Our study, along with other recent studies, shows that mini plates provide stable anchorage for orthodontic tooth movement, especially for the correction of anterior open bites.33–38

Before intrusive force application, the molars were connected with a TPA that was constructed three mm away from the palatal tissue to avoid impingment of the wire in the tissues during the intrusion phase. This modification could also exert an intrusive force of the tongue against the TPA and molars. Also introduce the abbreviation TPA with its expansion.

Most of the anterior open bite patients treated needed posterior maxillary dental expansion. Our finding shows maxillary dental constriction was corrected by uprighting the posterior teeth with the application of an intrusive force. The maxillary occlusal plane rotated in a clockwise direction. For patients who do not present with maxillary posterior dental constriction, a rigid posterior acrylic cap splint type of appliance can be used to resist the moment generated by the intrusive force.

Some patients experienced some tissue inflammation at the implant site because of plaque accumulation and irritation of the cheeks by the implant. We recommended good oral hygiene and oral rinses with chlorhexidine. We modified the incision technique to reduce postoperative patient discomfort and enhance the healing process. The modification consisted of using a vertical instead of a horizontal incision. For increased patient comfort and reduced soft tissue irritation, specially designed plates can be used with better adaptation to the anatomical structures instead of the conventional titanium mini plates.

CONCLUSIONS

Contemporary orthodontic treatment requires a short treatment time and minimal patient cooperation. This preliminary investigation showed that skeletal anchorage can be used effectively for anterior open bite correction in nongrowing patients. Minimal patient cooperation was required (no headgear, no anterior box elastics), except for good oral hygiene. A minimally invasive and simple technique facilitated the surgical procedure and reduced the operation time.

Skeletal anchorage has become an important contemporary tool in orthodontics, and the findings of our preliminary study are promising for future investigations. Long- term follow-up should be carried out to assess the stability of the treatment results.