In patients with mutilated posterior teeth, the remaining

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1 CLINICIAN S CORNER Orthodontic distalization with rigid plate fixation for anchorage after bone grafting and maxillary sinus lifting Robert Willer Farinazzo Vitral, a Marcio José da Silva Campos, b Julia Cristina de Andrade Vitral, b Rodrigo César Santiago, b and Marcelo Reis Fraga c Juiz de Fora, Brazil A 68-year-old woman was treated with an autogenous particulated bone graft from the anterior part of the mandible to elevate the right maxillary sinus floor, which was next to the alveolar ridge of an edentulous area, to facilitate dental implant placement. A rigid plate for anchorage was placed into the zygomatic bone. The maxillary right canine and the premolars were moved distally 6 months after the implant was placed and osteointegration of the bone graft had occurred. The Class II relationship was corrected. After tooth movement, the patient underwent multislice computed tomography to determine the mineral density of the bone graft and compare it with the opposite side of the maxilla. The mineral density showed values above normal for the posterior segment of the maxilla. Although the patient was taking bisphosphonate for treatment of osteoporosis, no related complications were noted during treatment. (Am J Orthod Dentofacial Orthop 2009;136:109-14) In patients with mutilated posterior teeth, the remaining teeth must often be repositioned before the dentition can be successfully restored. Displacement of teeth into areas with substantial atrophy of the alveolar ridge or through the maxillary sinus is considered a major limitation. 1 Similarly, the placement of endosseous implants in edentulous areas of the jaws is frequently limited by inadequate bone volume of the residual ridge and decreased bone quantity. 2-5 Edentulism, profound marginal periodontitis, trauma, malformation, neoplasia, poorly fitting dentures, and progressive hyperpneumatization of the sinus can lead to atrophy or defects of the alveolar ridge; these can complicate rehabilitation of the masticatory function. Furthermore, once a tooth has been extracted, resorption of the alveolar bone ensues to a variable extent. In the maxillary sinus region, this resorption can be significant, with nearly the entire region of alveolar bone replaced by the maxillary sinus. 3,6,7 From the Federal University of Juiz de Fora, Juiz de Fora, Brazil. a Associate professor and chair. b Postgraduate student. c Professor. The authors report no commercial, proprietary, or financial interest in the products or companies described in this article. Reprint requests to: Robert Willer Farinazzo Vitral, Av. Rio Branco 2595/ , Juiz de Fora, MG, Brazil, CEP ; , robertvitral@acessa. com. Submitted, February 2007; revised and accepted, July /$36.00 Copyright Ó 2009 by the American Association of Orthodontists. doi: /j.ajodo Fig 1. Periapical radiography of the posterior segment of the maxilla (right side) before grafting. Tooth movement through the maxillary sinus or areas with reduced alveolar bone volume is possible with adequate control of the force and the momentto-force ratio, with light and well-distributed forces on the teeth. The application of adequate forces to teeth allows frontal bone resorption while newly formed bone is deposited on the opposite surface of the alveolus; then the tooth moves with the bone. Simultaneously, a compensatory osseous apposition takes place in the medullary spaces anterior to the tooth; thus, a bone layer of constant thickness is preserved by this mechanism, and dental displacement occurs without bone loss. 8,9 109

2 110 Vitral et al American Journal of Orthodontics and Dentofacial Orthopedics July 2009 Fig 2. Intraoral photography: before tooth movement. A, Right side, (Class II canine relationship); B, frontal view; C, left side. Studies have demonstrated this osseous transportation during tooth movement The reconstruction of either bone atrophy or defects in the maxillofacial region has become possible with the expanded use of osseointegrated implant-supported prosthetics. 3 Onlay grafting and sinus floor augmentation are standardized and successful treatment options for addressing severe atrophy of the posterior maxilla and augmenting the alveolar ridge. Because bone substitutes do not provide the cellular elements necessary for osteogenesis, the use of autogenous bone is still regarded as the gold standard of all possible bone substitutes in maxillofacial surgery. 4,5,11-14 Nonautogenous preparations are still used because of limitations in acquiring adequate amounts of autogenous bone or simply because of the convenience of packaged preparations. 3 However, healing and remodeling of these nonautogenous grafts is less predictable, and they are less biocompatible and osteoinductive. 2,6,15,16 A limiting factor in autogenous bone grafts has been how to acquire adequate bone in a minimally invasive manner. 3 Many sites, intraoral and extraoral, have been used as donor sites, including the chin and retromolar region, calvarium, tibia, rib, and iliac crest. 2,6,7,17,18 However, to confine surgery to the oral cavity and perform it under local anesthesia, intraorally harvested grafts are preferred, especially if a limited amount of bone is required. 19 Among the many intraorally accessible bone surfaces, the mandibular symphysis is one of the few sites available for harvesting enough bone with the traditional surgical technique of removing blocks, sections, or cores of bone. 3,6 The symphysis and the lateral body of the mandible are the most common sites for harvesting blocks of bone. 14,19 Most other intraoral sites are not candidates for harvesting bone because of their proximity to tooth roots, neural structures, and the thin bones overlying the maxillary sinus and the nasal antrum. 3 Fig 3. A, Postgrafting panoramic radiography; B, CT image showing postgrafting maxillary sinus floor. According to the bone-graft biology, the microarchitecture of cortical bone and the membranous origin of mandibular bone allows fast revascularization, less resorption, and a more predictable outcome than bone from the iliac or tibia. 20,21 Furthermore, the bone-graft mineralization rate from the mandibular symphysis has been shown to be 50% higher than that from the iliac crest. 22 The harvested bone can be used as a block, but it

3 American Journal of Orthodontics and Dentofacial Orthopedics Vitral et al 111 Volume 136, Number 1 Fig 4. A, Intraoral photography (right side) after tooth movement (canine Class I relationship); B, periapical radiography of the right posterior segment of the maxilla after tooth movement; C, pre- and postmaxillary right canine and premolar distalization intraoral occlusal photography. Fig 5. Multislice CT image of the maxillary right second premolar after tooth movement (right side). is most often rendered into particulate form with rongeurs or a bone mill. The particulate form of the graft, which can be adapted to the site being reconstructed, increases the density of the graft and enhances the rate of healing. 2,4,11-13,23 Anchorage is the first consideration in the design of any orthodontic appliance, especially for an adult. Recently, oral implants have become reliable therapeutic alternatives when natural intra-oral anchorage cannot be found. 9 The skeletal anchorage system consists of anchor miniplates with monocortical bone screws that are temporarily implanted on the cortical bone of the maxilla or mandible; it was developed to provide absolute intraoral anchorage for orthodontic tooth movements. 24

4 112 Vitral et al American Journal of Orthodontics and Dentofacial Orthopedics July 2009 Fig 6. Multislice CT image of the maxillary right sinus floor after tooth movement (right side). Fig 7. Multislice CT image of the maxillary left sinus floor (left side). DISCUSSION A 68-year-old woman who was taking bisphosphonateas (ibandronate sodium) as part of treatment for osteoporosis had lost her maxillary right first and second molars in an accident at 20 years of age. She was referred to the orthodontic clinic at Federal University of Juiz de Fora, Juiz de Fora, Brazil, for proper repositioning of her teeth and subsequent replacement of her maxillary right removable partial denture with implants. Her chief complaint was that her denture caused discomfort and migraine headaches. The patient exhibited pneumatization of the maxillary sinus resulting from earlier extractions (Fig 1). The maxillary and mandibular right canines had a Class II relationship (Fig 2, A); therefore, the maxillary canine and first and second premolars needed distalization. Figure 2, B, shows the frontal view of the occlusion, and Figure 2, C, shows the left lateral view of the occlusion.

5 American Journal of Orthodontics and Dentofacial Orthopedics Vitral et al 113 Volume 136, Number 1 For adequate implant placement, autogenous bone graft and lifting of the maxillary sinus were planned. An autogenous particulated bone graft from the mandibular symphysis was done. This donor site was chosen because it provides a significant amount of bone, 3,6 it is not near any structure vulnerable to injury during bone harvesting, 3 and it has a high mineralization rate. 22 A rigid straight fixation plate with three mm screws was placed into the body of the zygomatic bone to provide the necessary anchorage for tooth distalization (Fig 3). This plate remained in place submucously for 6 months. Then osteointegration was verified, and tooth movement was started. The maxillary right posterior segment was distalized until a Class I canine relationship was obtained (Fig 4). Distalization time was 26 weeks. The maxillary right premolar brackets were removed so that multislice computed tomography (CT) images could be made to evaluate the bone graft density and compare it with the contralateral side in the maxilla. Bone mineral densitity is predominantly responsible for initial fixation and implant overlife; however, the failure rate increases considerably when an implant is placed into low-quality bone. 24 Quantitative CT is considered an effective method for assessing bone mineral density. Bone mineral densitity values are expressed in Hounsfield units (HU); normal values are above 850 HU for the anterior part of the mandible and range from 0 to 550 for the posterior part of the maxilla. 25 The values obtained for the right side were 527 HU for the bone graft area near the root apex of the second premolar (Fig 5) and 515 HU for the bone graft area in the maxillary sinus floor distal to the second premolar (Fig 6). On the left side, the values were HU for the area superior to the apex of the second premolar and for the region distal to the second molar (Fig 7). The bone-graft mineral density showed values above normal in the posterior part of the maxilla because the donor site had higher density than the receptor site. These bone density values, associated with alveolar ridge height, enabled the patient to receive dental implants in the maxillary molar region. On the right side, the bone mineral density values were within normal limits. CONCLUSIONS Maxillary sinus lifting with an autogenous bone graft has been shown to be effective in allowing tooth movement in an area with reduced alveolar ridge height and pneumatization of the maxillary sinus, and in providing conditions for implant placement in good-quality bone (mineral density), ensuring a favorable prognosis for the procedure. 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