Subapical osteotomy to correct dental implant malpositioning and vertical ridge deficiency: A clinical report Andrew Kim, DDS,a Kian Kar, DDS, MS,b Hessam Nowzari, DDS, PhD,c Kang-Min Ahn DDS, MSD, PhD,d and Hyunsuk Cha, DDS, MSD, PhDe University of Southern California, Los Angeles, Calif; College of Medicine, University of Ulsan, Seoul Asan Medical Center, Seoul, Korea This clinical report describes a subapical osteotomy to correct vertical ridge deficiency and malpositioned maxillary anterior implants. A 37-year-old woman with a noncontributory medical history presented with the chief complaint of an unesthetic implant-supported prosthesis. The maxillary left central and lateral incisors were restored with metal ceramic restorations. Gingiva-colored porcelain was fabricated to compensate for severe vertical and horizontal soft tissue deficiency. The patient was dissatisfied with the esthetics associated with the restorations and soft tissues since she presented with a high smile line and gingival display. Under general anesthesia, a subapical osteotomy was performed. The implant and ridge segment was coronally repositioned to correct the ridge deficiency. The surgical procedure and postoperative healing were uneventful. The surgical outcome was stable for a follow-up period of 3 years. The subapical osteotomy provided a satisfactory clinical outcome in managing a severely deficient residual ridge and malpositioned maxillary anterior implants as an alternative treatment to other surgical approaches. (J Prosthet Dent 2012;108:204-208) The maxillary subapical osteotomy (SAO) procedure was introduced by Cohn-Stock in 1921 as a form of segmental osteotomy in orthognathic surgery.1 The technique involves separating and repositioning the teethcontaining bone segment. Modifications of this technique have been developed for the advancement or retrusion of anterior segments such as bimaxillary protrusion, correction of occlusal planes, and repositioning a single tooth.2-8 Additionally, a few clinical reports have advocated similar techniques to correct severely malpositioned dental implants. 9-13 These techniques may be useful for managing esthetics in the maxillary anterior sextant with vertical ridge deficiencies. Historically, these defects have been managed with prostheses using gingiva-colored porcelain15 or with bone augmentation procedures.16
Masking those deficiencies with gingiva-colored porcelain can be challenging and may result in unsatisfactory esthetics. Alternatively, vertical ridge augmentation using guided bone regeneration,17,18 onlay block graft,19,20 distraction osteogenesis,21,22 or titanium mesh23 has been advocated by several authors. However, their application has been anecdotally reported to have high rates of adverse outcomes. Few studies have applied the segmental osteotomy for vertical ridge augmentation by coronally down-fracturing a bone segment.24,25 Surgical considerations of this technique include preservation of blood supply,26,27 adjacent tooth vitality, 28-32 and nasal soft tissue profiles.33-37 Management of vertical bone deficiency is more complicated when the implants have been previously placed in these deficient residual ridges. Im-
plant removal, reconstructing the ridge, and subsequent implant placement may be performed to achieve proper tissue contours. However, the patient may be reluctant to undergo multiple surgical procedures because of an increase in morbidity, time, and financial investment. This clinical report describes a surgical technique, subapical osteotomy (SAO), to simultaneously correct vertical ridge deficiency and reposition the implants with a segmental down-fracture.
CLINICAL REPORT A 37-year-old Korean woman presented to a private practice in Seoul, South Korea for management of an unesthetic implant restoration (maxillary left central and lateral incisors). She underwent multiple failed implant surgeries. An autogenous ra-
Resident, Department of Advanced Periodontology, University of Southern California. Associate Professor of Clinical Dentistry, Department of Advanced Periodontology, University of Southern California. c Professor and Clinical Director, Department of Advanced Periodontology, University of Southern California. d Associate Professor, Department of Advanced Periodontology, University of Southern California; Department of Oral and Maxillofacial Surgery, College of Medicine, University of Ulsan, Seoul Asan Medical Center. e Assistant Professor, Department of Prosthodontics, College of Medicine University of Ulsan, Seoul Asan Medical Center. a
b
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1 Gingiva-colored porcelain to camouflage tissue defects in left anterior teeth.
2 Preoperative panoramic radiograph.
3 Seven millimeter vertical defect was observed. Average of 3 mm probing depth.
4 Mucogingical incision line was marked.
mus bone graft was subsequently performed. The implants were replaced and the definitive prosthesis with gingiva-colored porcelain was inserted. The patient was not satisfied with the esthetic result of the prosthesis, and presented with a high smile line and significant discrepancies between the soft tissue levels of the gingivacolored prosthesis and the gingival architecture of the adjacent teeth (Figs. 1, 2). Upon removal of the prosthesis, approximately 7 mm of vertical ridge loss could be assessed at the implant sites (Fig. 3). To accommodate the significant ridge resorption, the implants had been placed more apically than the desired implant position. To correct the vertical ridge deficiency and position of the implant, SAO was performed under general anesthesia. This decision was made after reviewing risk benefits, cost
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benefit and treatment time of an alternative treatment plan of implant removal, ridge reconstruction, and placement of new implants. A mucosal vestibular incision was performed approximately 5 to 8 mm apical to the mucogingival junction at the malpositioned implant sites (Fig. 4). By using a modified Cupar’s maxillary anterior SAO technique,27 full-thickness flap elevation was performed from the mucosal incision with minimal exposure of the bone to maximize periosteal attachment connected to the buccal side of the bone segment.38 SAO was performed by using small carbide round burs (Resin Bur; Aesculap, Inc, USA, Center Valley, Pa) and microsaws (Aesculap ELAN-EC Surgical Drill set; Aesculap, Inc, USA). A horizontal osteotomy was prepared apical to the implant and 5 mm coronal to the nasal cav-
ity to prevent distortion of the nose. Vertical osteotomies were prepared to separate the block segment from the maxillary ridge that contained the implant. The palatal periosteum was released through the access created by the osteotomies. The bone segment containing the implants was downfractured by using 7 mm chisels (Leibinger Chisel; Stryker Leibinger GmbH & Co, Mühlheim, Germany) (Fig. 5). Previous abutments were used to determine the ideal position for the bone segment, which was guided by the prosthodontist. To stabilize the down-fractured segment, autogenous block bone graft harvested from the ramus was inserted between the down-fractured segment and the apical basal bone (Fig. 6). The ramus bone graft was fixed with the remaining ridge and implant-supporting bone segment by using miniplates
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5 Subapical osteotomy was performed. Seven millimeter 6 Right side ramal bone harvested using microsaw and segmental down-fracture was performed. Periosteal soft drill. tissue attachments were connected to down-fractured segment.
7 Harvested ramal bone grafted to gap and fixed with microplate and miniplate.
8 Seven millimeter downward position was observed immediately after surgery.
9 Postoperation radiograph.
10 Definitive prosthesis 3 years after subapical osteotomy.
and screws (Leibinger Universal Fixation System, 1.2 mm microplate Yshape, 1.7 mm low-profile miniplate, straight 4 hole, 5 mm screws; Stryker Corporation, Kalamazoo, Mich). Remaining gaps were filled with particulate bone (Fig. 7). The custom
abutments were changed to healing abutments to create clearance for occlusion. The flap was sutured with interrupted submucosal and continuous mucosal sutures (4-0 Vicryl; Ethicon Inc, Somerville, NJ). Immediately after surgery, it was
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evident that the bone segment containing the implants had been coronally positioned by 7 mm (Figs. 8, 9). This was assessed by comparing the bone crest to the mandibular incisal edge distance before and after segmental down-fracture. Sutures were
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October 2012 removed at 2 weeks and an interim partial removable dental prosthesis was provided. Healing was uneventful. A new prosthesis without gingiva-colored porcelain was inserted 4 months after surgery. The patient was satisfied with the esthetic results. The results were stable 3 years posttreatment (Fig. 10).
DISCUSSION Management of malpositioned implants in a vertically deficient ridge can be challenging for the clinician and patient. Implant removal and subsequent vertical ridge reconstruction for implant replacement can be considered to restore tissue contours and to correct the implant position. Numerous techniques, such as guided bone regeneration, onlay block graft, distraction osteogenesis, and titanium mesh, have been advocated for vertical ridge reconstruction. However, the application of these techniques has been difficult to generalize because of the limited number of studies, varying measured variables, and varying complication rates.16 Additionally, the patient may be reluctant to accept treatment that involves implant removal, grafting, and replacement of the implant. The SAO may be useful in applications for ridge reconstruction or implant repositioning. Langer24 and Jensen et al25 reported successful treatment of patients with vertical augmentation of the maxillary anterior ridge by coronally positioning a bone segment. Additionally, several clinical studies have applied the SAO to reposition incorrectly placed implants with various stabilization methods. Other reported methods involved miniplates and screws to fix the implant-containing bone segment,9 a prefabricated cast-metal substructure for positioning and stabilization of the implant-containing bone segment,10 repositioning the segment without any rigid fixation appliances,12 and orthodontic wires to stabilize the implant at the healing abutment similar to an avulsed
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tooth.11 The reports recommend a full thickness crestal incision to gain access to the surgical site, which may decrease the periosteal blood supply to the implant-containing bone segment and overall success of the procedure. The most significant inherent risk for this procedure would be necrosis of the bone segment, which could result in functional failure of the implant and a catastrophic increase in defect size. Preservation of the periosteal attachment to the bone segment is considered essential for maintaining adequate blood supply to the segment.26 Surgical techniques by Wassmund, Wunderer, and Cupar aim to preserve maximal blood supply while providing access for osteotomy preparation.27 This modified technique was used to provide direct visual access to the osseous tissue with a labial vestibular incision and to maintain buccal and palatal periosteal blood supply to the segment. Current literature describing segmental osteotomy for implant dentistry is limited to clinical reports and case series. However, segmental osteotomy has had a long history of success as a form of orthognathic surgery since it was described by Cohn-Stock in 1921.1 This technique has been used to correct a wide variety of dental and skeletal concerns by repositioning teeth-containing bone segments. The maxillary subapical SAO is commonly used to correct bimaxillary protrusion, which is commonly seen in Asian populations.3,4 Additional applications of subapical osteotomy include correcting anterior open articulation,2 repositioning ankylosed teeth,5,6 and immediate diastema closure.7,8 Postoperative pulp vitality in teeth within and adjacent to the block segment is another significant consideration when performing the subapical osteotomy. Several studies have reported that changes in the pulpal status were mostly associated with teeth contained in the mobilized bone segment.28-32 Teeth adjacent to the vertical osteotomy in the nonmobilized
bone did not have a significant longterm change in the pulp vitality.31 Nonetheless, damage to the implant and adjacent teeth should be avoided with careful surgical techniques and pre-operative analysis of inter-implant-radicular distance. In the SAO, implants contained in the bone segment are inherently not vital and are, therefore, immune to necrosis. The predictability of implant survival and changes in bone-to-implant contact due to the subapical osteotomy have not been investigated. Clinically, maxillary anterior implants are placed with varying proximities to the nasal cavity. Sufficient clearance between the implant and nasal floor should be present before attempting the subapical osteotomy in the maxillary anterior sextant. Maxillary orthognathic surgery has the potential to induce changes in nasal soft tissue profiles with the inclusion of the nasal floor and lateral nasal wall in the mobilized segment.33-36 Modified maxillary SAO that excludes the nasal components is increasingly becoming the favored surgical technique for treatment of bimaxillary protrusion because soft tissue profiles are more predictable.3,37 These principles should be considered when performing the subapical osteotomy to avoid nasal soft tissue changes. Interdisciplinary consideration is essential for successful management of malpositioned implants with the SAO. Ideal implant position is necessary to achieve optimal esthetic results and appropriate contours of the definitive restorations. Before surgical execution, the restorative dentist can determine the desired implant position with the fabrication of a surgical guide or by using an implant guide pin. The surgeon can use the surgical guide with implant guide pins on the malpositioned implants to verify the desired position of the mobilized segment. This allows visualization of the implant depth, buccopalatal position, and angulation during the surgical procedure. In this patient, SAO was performed to vertically augment the re-
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sidual ridge and coronally reposition the implants simultaneously by using a modified Cupar’s technique with a 3-year follow-up. The SAO may be a useful alternative to implant removal, bone graft, and implant replacement, which need multistaged surgeries and longer treatment time. The awareness and predictability of success of the subapical osteotomy for correcting malpositioned implants are not well established. Current literature that applies the segmental osteotomy to implant dentistry is limited to case studies and series. Further controlled studies are needed to demonstrate the predictability of this subapical osteotomy.
SUMMARY The results of this clinical report show that SAO is a viable treatment option that can be considered for select patients requiring correction of implant position.
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24.Langer B. The segmental down fracture for vertical bone augmentation: a case report. Clin Implant Dent Relat Res 2010;12 Suppl 1:e126-31. 25.Jensen OT, Kuhlke L, Bedard JF, White D. Alveolar segmental sandwich osteotomy for anterior maxillary vertical augmentation prior to implant placement. J Oral Maxillofac Surg 2006;64:290-6. 26.Bell WH. Biologic basis for maxillary osteotomies. Am J Phys Anthropol 1973;38:279-89. 27.Balaji S. Textbook of Oral & Maxillofacial Surgery. New Delhi: Elsevier;2009. 464-492. 28.Banks P. Pulp changes after anterior mandibular subapical osteotomy in a primate model. J Maxillofac Surg 1977;5:39-48. 29.Pepersack WJ. Tooth vitality after alveolar segmental osteotomy. J Maxillofac Surg 1973;1:85-91. 30.Poswillo DE. Eearly pulp changes following reduction of open bite by segmental surgery. Int J Oral Surg 1972;1:87-97. 31.Theisen FC, Guernsey LH. Postoperative sequelae after anterior segmental osteotomies. Oral Surg Oral Med Oral Pathol 1976;41:139-51. 32.Leibold DG, Tilson HB, Rask KR. A subjective evaluation of the re-establishment of the neurovascular supply of teeth involved in anterior maxillary osteotomy procedures. Oral Surg Oral Med Oral Pathol 1971;32:531-4. 33.Sarver DM, Weissman SM. Long-term soft tissue response to LeFort I maxillary superior repositioning. Angle Orthod 1991;61:267-76. 34.Rosen HM. Lip-nasal aesthetics following Le Fort I osteotomy. Plast Reconstr Surg 1988;81:171-82. 35.Betts NJ, Vig KW, Vig P, Spalding P, Fonseca RJ. Changes in the nasal and labial soft tissues after surgical repositioning of the maxilla. Int J Adult Orthodon Orthognath Surg 1993;8:7-23. 36.Engel GA, Quan RE, Chaconas SJ. Soft-tissue change as a result of maxillary surgery. A preliminary study. Am J Orthod 1979;75:291-300. 37.Park JU, Hwang YS. Evaluation of the soft and hard tissue changes after anterior segmental osteotomy on the maxilla and mandible. J Oral Maxillofac Surg 2008;66:98-103. 38.Cupar I. Surgical treatment of alterations in form and position of the maxilla. Osterr Z Stomatol 1954;51:565-77. Corresponding author: Dr Kang-Min Ahn Department of Oral and Maxillofacial Surgery College of Medicine, University of Ulsan Seoul Asan Medical Center Seoul KOREA Fax: +82-2-3010-6967 E-mail:
[email protected] Copyright © 2012 by the Editorial Council for The Journal of Prosthetic Dentistry.
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