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The Modified “Sandwich” Technique: A Novel Surgical Approach to Regenerative Treatment of Horizontal Bone Defects in the Posterior Atrophic Mandible. A Case Report Pietro Felice, MD, DDS, PhD,* Luigi Checchi, MD, DDS, PhD,† Roberto Pistilli, MD, DDS, PhD,‡ Carlo Barausse, DDS,§ and Sergio Spinato, DDSk
rosthetic rehabilitation of a totally or partially posterior edentulous mandible is a common clinical objective.1 Dental implant placement with a fixed implant supported prosthesis is an established procedure to treat edentulous jaws.2 However, implant placement may prove difficult or impossible in sites with limited alveolar bone height or width. In this type of situation, it is difficult to insert an implant of adequate length.1 In an atrophic posterior mandible, various preprosthetic augmentation procedures3–5 have been performed to overcome difficulties caused by the superficialization of the inferior alveolar nerve in areas of significant horizontal and vertical bone defects.
P
*Researcher, Department of Biomedical and Neuromotor Sciences, School of Dentistry, University of Bologna, Bologna, Italy. †Professor of Periodontology, Department of Biomedical and Neuromotor Sciences, School of Dentistry, University of Bologna, Bologna, Italy. ‡Researcher, Oral and Maxillofacial Department, A.C.O. San Filippo Neri, Rome, Italy. §Research Fellow, Department of Biomedical and Neuromotor Sciences, School of Dentistry, University of Bologna, Bologna, Italy. kContract Professor, Department of Biomedical and Neuromotor Sciences, School of Dentistry, University of Bologna, Bologna, Italy.
Reprint requests and correspondence to: Sergio Spinato, DDS, via F. Cavallotti 134/A, 41049 Sassuolo, Italy, Phone: 0039-0536-883868, Fax: 0039-0536-400082, E-mail: [email protected] ISSN 1056-6163/14/02303-232 Implant Dentistry Volume 23 Number 3 Copyright © 2014 by Lippincott Williams & Wilkins DOI: 10.1097/ID.0000000000000062
Purpose: A new augmentation procedure for bone reconstruction of horizontal defects in a posterior atrophic mandible is described. Materials and Methods: A 47year-old male patient with horizontal atrophy of the left posterior mandible was treated using a 2-stage modified “sandwich” osteotomy technique with an interposed mixture of mineralized and demineralized human bone allograft in putty form. Results: The osteotomized superior segment was slightly raised and then drawn and rotated in the buccal direction to augment the horizontal width of the crest. The
osteotomized segment was kept in this position with a titanium miniplate andminiscrews. No complications were reported during the 3-month healing period. In the second surgical phase, 2 implants were correctly placed. Conclusions: Cone beam computed tomography (CBCT) outcomes confirm the effectiveness of this technique in the treatment of horizontal defects. However, further randomized controlled studies are required to confirm the technique’s reliability. (Implant Dent 2014;23:232–238) Key Words: bone regeneration, human allograft, inlay bone graft, mandibular atrophy
Guided bone regeneration (GBR),6 autogenous block grafts from both intraoral7,8 and extraoral sources,9,10 alveolar osteodistraction,11 and autologous bone or biomaterial grafts with a titanium mesh12 are treatments that have been developed to heal bone volume defects. A lack of comparative studies has made the choice of the most reliable and predictable augmentation technique difficult. A recent review of this topic stated that although bone augmentation is possible, the number of complications and failures associated with the
various techniques described remains unacceptably high, especially for vertical bone augmentation (.20%).13 This review also evidenced that it is difficult to establish which technique is most efficient due to the poor quality of research, including only few studies of few patients with only short follow-up periods and often being judged as having high risks of bias. For these reasons, the choice may depend entirely upon the ability of the surgeon.13 One procedure for the reconstruction of an extremely atrophic anterior mandible is the “sandwich” osteotomy
IMPLANT DENTISTRY / VOLUME 23, NUMBER 3 2014
Fig. 1. Preoperative Panorex of posterior left mandible.
intraoral or extraoral bone harvesting, which is invasive, time-consuming, technically demanding, and subject to complications.18 Felice et al9,10 recently demonstrated that with the inlay technique the use of deproteinized bovine bone mineral blocks has clinical and histological results similar to the same procedure with autologous bone harvesting from the iliac crest but is much less invasive and may be preferable to the autogenous bone technique. However, the use of xenografts has been associated with the persistence of residual material due to slow resorption rates.10
Fig. 2. CBCT series revealing crestal width reduction: (A) at section 15, 12 mm above mental nerve foramen; (B) at section 17, 10 mm above nerve canal; (C) at section 19, 8.5 mm above nerve canal. Placement of the 2 implants was planned at sections 17 and 19 for correct mesio-distal positioning.
technique, first described by Schettler14 in 1976. This procedure has been performed recently in the posterior mandible with positive outcomes.15,16 Horizontal osteotomy with the interposition of bone in the form of a “sandwich” involves raising a coronal osteotomized segment of the mandible still attached to the lingual periosteum and interpositioning of an autogenous bone block graft. This guarantees greater vascularization of the inlay graft. Additionally, it allows optimum use of the basal bone, which is less prone to resorption.17 Frequently, however, these techniques are associated with autologous bone harvesting, causing discomfort and postsurgical morbidity. Often the patient can not undergo grafting techniques using autogenous bone, as these require
Furthermore, the use of a deproteinized bovine bone block is challenged by the extreme fragility of the block. A high risk of breakage during the shaping and placing of these blocks was described, and clinical results have shown insufficient vertical bone gain.9,10,19 For all these reasons, researchers have examined new graft materials that resorb more rapidly and that perfectly integrate with the surrounding bone.20 All these factors have lead clinicians to focus on the use of allogenic bone graft materials.21 These grafting materials are bonederived products harvested from cadavers, processed, and then sterilized. These graft types have been used for horizontal and vertical ridge regeneration.22–24 A limitation of the inlay technique is that it only corrects vertical and not horizontal defects.9,10,15 The presence
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of a horizontal defect of the residual bone crest does not permit sufficient horizontal bone augmentation. For these reasons, the authors propose a modified “sandwich” technique in the regenerative treatment of the horizontal bone ridge defects. This 2-stage technique was performed monolaterally in this case report to treat horizontal atrophy in an edentulous posterior mandible using mineralized and demineralized human bone allograft.
CASE REPORT A 47-year-old systemically healthy male was referred to the Oral and Maxillofacial Surgery Department of the University of Bologna (Italy) for a fixed prosthetic rehabilitation of the second premolar and molar zone of his posterior left mandible. A preoperatory panoramic radiograph and a cone beam computed tomography (CBCT) scan were performed to plan implant positioning and to evaluate alveolar residual bone anatomy (Figs. 1 and 2). The horizontal defect of the mandibular portion precluded correct implant insertion in the second premolar and first molar region (Fig. 2). The preoperative mean residual bone height above the left mental nerve foramen was 12 mm at section 15 (Fig. 2, A), 10 mm distal to the left mental nerve foramen at section 17 (Fig. 2, B), and 8.5 mm at section 19 (Fig. 2, C). The preoperative mean residual bone width was 3.4 mm above the left mental nerve foramen and 4 mm distal to the left mental nerve foramen (Fig. 2, A and B). A preliminary radiographic evaluation (panoramic and CBCT) was performed and dental casts made. A monolateral “sandwich” augmentation procedure was chosen to allow placement of 2 implants. The patient declined autogenous bone harvesting. Therefore, a regenerative procedure was proposed using a mixture of mineralized and demineralized human bone allograft in putty form (Readi Graft Crunch Putty; LifeNet, Virginia Beach, VA). The patient gave written informed consent to the treatment. The surgical procedure was performed monolaterally under local anesthesia (Fig. 3, A). The technique started
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Fig. 3. A, Preoperative clinical situation revealing atrophic horizontal crest. B, Paracrestal incision in the buccal vestibule. C, Exposition and isolation of mental nerve. D, Coronal segment preparation with piezoelectric device.
Fig. 4. A, Executed horizontal and distal cuts and unexecuted mesial cut to be performed 2 mm distal to first premolar. B, Sparing lingual periosteum. We intended to spare the periosteum by avoiding the use of a blade or dissector on the lingual side of the periosteum and consequently performed a form of tunnel technique on the lingual side.
with a paracrestal incision in the buccal vestibule and the subperiosteal tissues were dissected carefully with no tension on the ipsilateral mental nerve (Fig. 3, B and C) No mucoperiosteal dissection was performed toward the alveolar crest or on the lingual side. Three Piezosurgical inserts (OT8R, OT8L, and OT7; Mectron Piezosurgery Device; Mectron, Carasco, Italy) were used to create a horizontal osteotomy approximately 2 to 3 mm above the mandibular canal and 2
additional oblique cuts (Fig. 3, D). The mesial cut was made 2 mm distal to the last tooth in the arch, whereas the distal cut was made in relation to the implant graft treatment plane (Fig. 4, A and B). Sparing the lingual periosteum, the cranial segment was raised 2 mm (Fig. 5, A) and then drawn and rotated buccally approximately 4 mm (Fig. 5, B) to compensate the horizontal defect. The buccal surface of this repositioned cranial segment becomes the most
coronal part of the new regenerated crest (Fig. 5, C and D). The osteotomized segment was kept in this position with a titanium miniplate and miniscrews (KLS Martin, Tuttlingen, Germany) fixed to both the basal bone and the transported fragment (Fig. 6, A and B). The large gap between the cranial osteotomized segment and the mandibular basal bone was filled by gently injecting bone putty (Ready Graft Crunch Putty; LifeNet) (Fig. 6, A). A resorbable collagen membrane (Colla Guide, Riemser, Germany) was applied above the buccal surface of the surgical site (Fig. 7, A). After making periosteal releasing incisions to obtain tension-free closure, the flaps were sutured carefully with Vicryl 4.0 (Ethicon FS-2; Ethicon, St-Stevens-Woluwe, Belgium) (Fig. 7, B). Antibiotic therapy was amoxicillin (Ratiopharm GmbH, Ulm, Germany) at a loading dose of 2 g, with 2 g/d beginning the day after surgery for 10 days together with a nonsteroidal analgesic (ketoprofen, Orudis; Aventis Pharma, Bridgewater, NJ). Postsurgical instructions included a soft food diet for 2 weeks and appropriate oral hygiene with twice-daily rinsing with a 0.2% chlorhexidine digluconate mouthwash (Corsodyl; GlaxoSmithKline, London, UK). The sutures were removed 15 days postoperatively. CBCT assessment and panoramic radiograph were performed immediately after surgery (Figs. 8 and 9). The patient was examined clinically 1 week after surgery, twice in the first month, and once in each of the subsequent 3 months. No neurosensory disturbances were recorded. In the second surgical phase, 2 implants were correctly placed. The radiographic images showed the healed ridge after another 3-month period, at the reopening appointment (Fig. 10, A–C).
DISCUSSION In the posterior mandible, inlay bone grafting has obtained postoperative vertical bone gains of 4–8 mm9,19,25 with a low complication rate9,26 and low bone resorption before implant placement owing to high potential for bone graft incorporation17,25 and reported success rates $90%.10,26
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Fig. 5. A, Cranial segment raised approximately 2 mm. B, Cranial segment drawn and rotated buccally. C, During the rotation of the coronal segment, we obtained a partial dissection of the periosteum from the bone. The repositioned buccal surface becomes most coronal part of regenerated crest. D, Elevator to maintain correct segment position before fixation.
Fig. 6. A, Cranial osteotomized segment and mandibular basal bone gap filled with bone putty. B, Osteotomized segment kept in this position with titanium miniplate and miniscrews.
Fig. 7. A, Resorbable collagen membrane applied above buccal surface. B, Primary intention closure.
Inlay graft has a greater potential for bone incorporation because the graft is interposed between the basal bone and the osteotomized segment,15
permitting osteoblasts to come from both sides to colonize the interpositional block. However, in the present novel surgical technique, the thinner coronal
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segment is rotated exposing the lingual cortex to oppose the cancellous bone from the basal bone. This may influence incorporation of the graft because colonization of the osteoblasts occurs predominantly from the basal segment. Another important advantage with this technique is the preservation of the lingual periosteum, which maintains blood supply to the graft and may reduce resorption.15,17 In particular, inlay graft results in less bone resorption and more predictable outcomes compared to onlay graft that requires an overheightened bone block graft.27 The presence of native bone in the osteotomized coronal segment can explain why implant survival and success rates are comparable to those in native alveolar bone26 and also the limited amount of peri-implant marginal bone loss after loading.10 Additionally, this rapid integration with different kinds of graft10,15,16,19,27,28 leads to a reduction in the time required before implant installation and final rehabilitation. In fact, instead of the 5 to 6 months necessary when using GBR, it is possible to place implants after only 3 to 4 months,10,27,28 reducing patient waiting time. In the treatment of combined vertical and horizontal bone defects, GBR,6 osteodistraction,11,26 and boneblock grafts7 are recommended, even if the number of complications and failures of these augmentation techniques is still too high (well over 20%) to recommend widespread use of such procedures.13,26 However, this percentage is an overall assessment, burdened by the high rate of complications related to osteodistraction. In fact, there are many publications with low complication rates and high success, especially with regard to bone blocks.7,8 Nevertheless, the main limit of the inlay technique is that it only corrects vertical defects and does not permit correction of horizontal defects.9,10,15 In this case report, a horizontal defect of the residual bone crest was treated with a modified “sandwich” technique to obtain not only a limited vertical augmentation of the crest but also primarily a horizontal increase. In fact, the osteotomized cranial segment was slightly raised and then drawn and rotated
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Fig. 8. Postoperative CBCT. A, Coronal segment rotation. B, Miniplate and miniscrews. C, elevation and rotation of repositioned segment.
Fig. 9. Postoperative Panorex of posterior left mandible.
buccally to augment the horizontal width of the crest (Fig. 5, A and B). The buccal surface of the repositioned cranial segment became the most coronal part of the new regenerated crest (Fig. 5, C and D). In the traditional inlay technique, the fragment is only raised in a coronal direction permitting the interposition of the graft, whereas in this modified technique, the segment is also moved and rotated in the vestibular direction compensating for the horizontal defect and thus completely covering the interposed graft. However, thanks to this soft tissue management technique permitting preservation of the lingual periosteum, an adequate blood supply to both the thin osteotomized segment and the graft was maintained. Surgical differences with GBR and block graft procedures necessitating the elevation of a lingual flap are therefore evident.
Fig. 10. Radiographic images of healed alveolar ridge at the reopening appointment. A, X-ray image of the posterior left mandible. B, CBCT showing the augmented area at the second premolar site. C, CBCT showing the augmented area at the first molar site.
Atrophic bone crests of less than 5 mm in width are considered to require regenerative procedures to create a bony wall of at least 1 mm around implants and provide successful long-term function.29 Spilt-crest techniques have also been proposed for this kind of horizontal defect.30 One-stage31 or 2-stage32 splitcrest techniques determine an increase in the width of the ridge, but do not provide vertical bone gain, as described in the present case report using a modified “sandwich” technique. Autografts are considered the gold standard for their osteogenic, osteoinductive, and osteoconductive properties.33 It is often impractical, however, to harvest the necessary amount of autologous bone block to reconstruct extensive defects. In addition, harvesting of autologous blocks entails patient discomfort due to doubling of the surgical site, postoperative morbidity, and complications, including nerve damage, gingival recession, edema, and loss of tooth vitality.18 The use of allografts23,34 and xenografts9,10 has been advocated to avoid all the cited problems. Allografts show better histomorphometric results and a higher resorption rate than xenografts.35 In this case report, the authors did not use a human bone block graft to fit the gap between the coronal osteotomized segment and the basal bone, but preferred to fill it with a mixture ofmineralized and demineralized allograft in putty form to obtain a better and quicker revascularization of the graft from the native bone. This mixture should offer the following additional advantages: the mineralized allograft is an osteoconductive material with relatively slow resorption,36 whereas demineralized bone matrix is considered to have osteoconductive capacity in intraoral edentulous sites36 and osteoinductive potential, as demonstrated by bone formation, when implanted submuscularly in animals.37,38 This combination should be advantageous, in that the demineralized bone matrix stimulates new bone formation and mineralized allograft offers a scaffold for bone deposition and remodeling as demonstrated in sinus elevation procedures.39
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CONCLUSION Within the limits of this case report, the clinical outcome suggests that the modified sandwich technique’s capabilities in horizontal bone reconstruction in the atrophic mandible eliminate problems caused by autologous bone graftings. Further research will confirm or refute potentially advantageous properties of this technique compared to other regenerative procedures for the treatment of horizontal defects in the posterior atrophic mandible.
DISCLOSURE The authors claim to have no financial interest, either directly or indirectly, in the products or information listed in this article.
REFERENCES 1. Felice P, Cannizzaro G, Checchi V, et al. Vertical bone augmentation versus 7-mm-long implants in posterior atrophic mandibles. Results of a randomized controlled clinical trial of up to 4 months after loading. Eur J Oral Implantol. 2009;2:7–20. 2. Albrektsson T. A multicenter report on osseointegrated oral implants. J Prosthet Dent. 1988;60:75–84. 3. Pikos MA. Block autografts for localized ridge augmentation: Part II. The posterior mandible. Implant Dent. 2000;9: 67–75. 4. Schwartz-Arad D, Levin L. Multitier technique for bone augmentation using intraoral autogenous bone blocks. Implant Dent. 2007;16:5–12. 5. Le B, Burstein J, Sedghizadeh PP. Cortical tenting grafting technique in the severely atrophic alveolar ridge for implant site preparation. Implant Dent. 2008;17: 40–50. 6. Simion M, Jovanovic SA, Tinti C, et al. Long-term evaluation of osseointegrated implants inserted at the time or after vertical ridge augmentation. A retrospective study on 123 implants with 1-5 year follow-up. Clin Oral Implants Res. 2001; 12:35–45. 7. Cordaro L, Amadé DS, Cordaro M. Clinical results of alveolar ridge augmentation with mandibular block bone grafts in partially edentulous patients prior to implant placement. Clin Oral Implants Res. 2002;13:103–111. 8. Schwartz-Arad D, Levin L, Sigal L. Surgical success of intraoral autogenous block onlay bone grafting for alveolar ridge augmentation. Implant Dent. 2005;14: 131–138.
9. Felice P, Marchetti C, Piattelli A, et al. Vertical ridge augmentation of the atrophic posterior mandible with interpositional block grafts: Bone from the iliac crest versus bovine anorganic bone. Eur J Oral Implantol. 2008;1:183–198. 10. Felice P, Marchetti C, Iezzi G, et al. Vertical ridge augmentation of the atrophic posterior mandible with interpositional bloc grafts: Bone from the iliac crest vs. bovine anorganic bone. Clinical and histological results up to one year after loading from a randomized controlled clinical trial. Clin Oral Implants Res. 2009;20:1386–1393. 11. Raghoebar GM, Liem RS, Vissink A. Vertical distraction of the severely resorbed edentulous mandible: A clinical, histological and electron microscopic study of 10 treated cases. Clin Oral Implants Res. 2002;13: 558–565. 12. Pieri F, Corinaldesi G, Fini M, et al. Alveolar ridge augmentation with titanium mesh and a combination of autogenous bone and anorganic bovine bone: A 2-year prospective study. J Periodontol. 2008;79: 2093–2103. 13. Esposito M, Grusovin MG, Felice P, et al. The efficacy of horizontal and vertical bone augmentation procedures for dental implantsdA Cochrane systematic review. Eur J Oral Implantol. 2009;2:167–184. 14. Schettler D. Sandwich-technique with cartilage transplant for raising the alveolar process in the lower jaw [in German]. Fortschr Kiefer Gesichtschir. 1976;20:61–63. 15. Marchetti C, Trasarti S, Corinaldesi G, et al. Interpositional bone grafts in the posterior mandibular region: A report on six patients. Int J Periodontics Restorative Dent. 2007;27:547–555. 16. Felice P, Piana L, Checchi L, et al. Vertical ridge augmentation of the atrophic posterior mandible with a 2-stage inlay technique: A case report. Implant Dent. 2012;21:190–195. 17. Stellingsma C, Raghoebar G, Meijer HJA, et al. Reconstruction of the extremely resorbed mandible with interposed bone grafts and placement of endosseous implants. A preliminary report on outcome of treatment and patient’s satisfaction. Br J Oral Maxillofac Surg. 1998;36:290–295. 18. Nkenke E, Radespiel-Troger M, Wiltfang J, et al. Morbidity of harvesting of retromolar bone grafts: A prospective study. Clin Oral Implant Res. 2002;13:514–521. 19. Felice P, Piattelli A, Iezzi G, et al. Reconstruction of atrophied posterior mandible with an inlay technique and inorganic bovine bone block: A case report. Int J Period Rest Dent. 2010;30:583–591. 20. Figuelredo M, Henriques J, Martins G, et al. Physicochemical characterization of biomaterials commonly used in dentistry as bone substitutesdComparison
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with human bone. J Biomed Mater Res B Appl Biomater. 2010;92:409–419. 21. Scarano A, Degidi M, Iezzi G, et al. Maxillary sinus augmentation with different biomaterials: A comparative histologic and histomorphometric study in man. Implant Dent. 2006;15:197–207. 22. Block MS, Degen M. Horizontal ridge augmentation using human mineralized particulate bone: Preliminary results. J Oral Maxillofac Surg. 2004;62(suppl 2):67–72. 23. Morelli T, Neiva R, Wang HL. Human histology of allogeneic block graft for alveolar ridge augmentation: Case report. Int J Period Rest Dent. 2009;29: 648–656. 24. Menoni A, Bernardello F, Spinato S, et al. Full-arch vertical reconstruction of an extremely atrophic mandible with “Box– Technique”. A novel surgical procedure: A clinical and histological case report. Implant Dent. 2013;22:2–7. 25. Yeung R. Surgical management of the partially edentulous atrophic mandibular ridge using a modified sandwich osteotomy: A case report. Int J Oral Maxillofac Implants. 2005;20:799–803. 26. Bianchi A, Felice P, Lizio G, et al. Alveolar distraction osteogenesis versus inlay bone grafting in posterior mandibular atrophy: A prospective study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008;105:282–292. 27. Felice P, Pistilli R, Lizio G, et al. Inlay versus onlay iliac bone grafting in atrophic posterior mandible: A prospective controlled clinical trial for the comparison of two techniques. Clin Implant Dent Relat Res. 2009;11(suppl 1):e69–e82. 28. Felice P, Lizio G, Marchetti C, et al. Magnesium-substituted hydroxyapatite grafting using the vertical inlay technique. Int J Periodontics Restorative Dent. 2013; 33:355–363. 29. Albrektsson T, Zarb G, Worthington P, et al. The long-term efficacy of currently used dental implants: A review and proposed criteria of success. Int J Oral Maxillofac Implants. 1986;1:11–25. 30. Scipioni A, Bruschi GB, Calesini G. The edentulous ridge expansion technique: A five-year study. Int J Periodontics Restorative Dent. 1994;14:451–459. 31. Vercellotti T. Piezoelectric surgery in implantology: A case reportda new piezoelectric ridge expansion technique. Int J Periodontics Restorative Dent. 2000;20: 358–365. 32. Anitua E, Begoña L, Orive G. Controlled ridge expansion using a twostage split-crest technique with ultrasonic bone surgery. Implant Dent. 2012; 21:163–170. 33. Chiapasco M, Zaniboni M. Clinical outcomes of GBR procedures to correct peri-implant dehiscences and fenestra-
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tions: A systematic review. Clin Oral Implants Res. 2009;20(suppl 4):113–123. 34. Waasdorp J, Reynolds MA. Allogeneic bone onlay grafts for alveolar ridge augmentation: A systematic review. Int J Oral Maxillofac Implants. 2010;25:525–531. 35. Froum SJ, Wallace SS, Elian N, et al. Comparison of mineralized cancellous bone allograft (Puros) and anorganic bovine bone matrix (Bio-Oss) for sinus
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augmentation: Histomorphometry at 26 to 32 weeks after grafting. Int J Period Rest Dent. 2006;26:543–551. 36. Cammack GV, Nevins M, Clem DS, et al. Histologic evaluation of mineralized and demineralized freeze-dried bone allograft for ridge and sinus augmentation. Int J Period Rest Dent. 2005;25:231–237. 37. Urist MR. Bone: Formation by autoinduction. Science. 1965;150:893–899.
38. Zhang M, Powers RM Jr, Wolfinbarger L. A quantitative assessment of osteoinductivity of human demineralized bone matrix. J Periodontol. 1997;68: 1076–1084. 39. Kim DM, Nevins ML, Camelo M, et al. The efficacy of demineralized bone matrix and cancellous bone chips for maxillary sinus augmentation. Int J Periodontics Restorative Dent. 2009;29:415–423.
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The Modified “Sandwich” Technique: A Novel Surgical Approach to Regenerative Treatment of Horizontal Bone Defects in the Posterior Atrophic Mandible. A Case Report Pietro Felice, MD, DDS, PhD,* Luigi Checchi, MD, DDS, PhD,† Roberto Pistilli, MD, DDS, PhD,‡ Carlo Barausse, DDS,§ and Sergio Spinato, DDSk
rosthetic rehabilitation of a totally or partially posterior edentulous mandible is a common clinical objective.1 Dental implant placement with a fixed implant supported prosthesis is an established procedure to treat edentulous jaws.2 However, implant placement may prove difficult or impossible in sites with limited alveolar bone height or width. In this type of situation, it is difficult to insert an implant of adequate length.1 In an atrophic posterior mandible, various preprosthetic augmentation procedures3–5 have been performed to overcome difficulties caused by the superficialization of the inferior alveolar nerve in areas of significant horizontal and vertical bone defects.
P
*Researcher, Department of Biomedical and Neuromotor Sciences, School of Dentistry, University of Bologna, Bologna, Italy. †Professor of Periodontology, Department of Biomedical and Neuromotor Sciences, School of Dentistry, University of Bologna, Bologna, Italy. ‡Researcher, Oral and Maxillofacial Department, A.C.O. San Filippo Neri, Rome, Italy. §Research Fellow, Department of Biomedical and Neuromotor Sciences, School of Dentistry, University of Bologna, Bologna, Italy. kContract Professor, Department of Biomedical and Neuromotor Sciences, School of Dentistry, University of Bologna, Bologna, Italy.
Reprint requests and correspondence to: Sergio Spinato, DDS, via F. Cavallotti 134/A, 41049 Sassuolo, Italy, Phone: 0039-0536-883868, Fax: 0039-0536-400082, E-mail: [email protected] ISSN 1056-6163/14/02303-232 Implant Dentistry Volume 23 Number 3 Copyright © 2014 by Lippincott Williams & Wilkins DOI: 10.1097/ID.0000000000000062
Purpose: A new augmentation procedure for bone reconstruction of horizontal defects in a posterior atrophic mandible is described. Materials and Methods: A 47year-old male patient with horizontal atrophy of the left posterior mandible was treated using a 2-stage modified “sandwich” osteotomy technique with an interposed mixture of mineralized and demineralized human bone allograft in putty form. Results: The osteotomized superior segment was slightly raised and then drawn and rotated in the buccal direction to augment the horizontal width of the crest. The
osteotomized segment was kept in this position with a titanium miniplate andminiscrews. No complications were reported during the 3-month healing period. In the second surgical phase, 2 implants were correctly placed. Conclusions: Cone beam computed tomography (CBCT) outcomes confirm the effectiveness of this technique in the treatment of horizontal defects. However, further randomized controlled studies are required to confirm the technique’s reliability. (Implant Dent 2014;23:232–238) Key Words: bone regeneration, human allograft, inlay bone graft, mandibular atrophy
Guided bone regeneration (GBR),6 autogenous block grafts from both intraoral7,8 and extraoral sources,9,10 alveolar osteodistraction,11 and autologous bone or biomaterial grafts with a titanium mesh12 are treatments that have been developed to heal bone volume defects. A lack of comparative studies has made the choice of the most reliable and predictable augmentation technique difficult. A recent review of this topic stated that although bone augmentation is possible, the number of complications and failures associated with the
various techniques described remains unacceptably high, especially for vertical bone augmentation (.20%).13 This review also evidenced that it is difficult to establish which technique is most efficient due to the poor quality of research, including only few studies of few patients with only short follow-up periods and often being judged as having high risks of bias. For these reasons, the choice may depend entirely upon the ability of the surgeon.13 One procedure for the reconstruction of an extremely atrophic anterior mandible is the “sandwich” osteotomy
IMPLANT DENTISTRY / VOLUME 23, NUMBER 3 2014
Fig. 1. Preoperative Panorex of posterior left mandible.
intraoral or extraoral bone harvesting, which is invasive, time-consuming, technically demanding, and subject to complications.18 Felice et al9,10 recently demonstrated that with the inlay technique the use of deproteinized bovine bone mineral blocks has clinical and histological results similar to the same procedure with autologous bone harvesting from the iliac crest but is much less invasive and may be preferable to the autogenous bone technique. However, the use of xenografts has been associated with the persistence of residual material due to slow resorption rates.10
Fig. 2. CBCT series revealing crestal width reduction: (A) at section 15, 12 mm above mental nerve foramen; (B) at section 17, 10 mm above nerve canal; (C) at section 19, 8.5 mm above nerve canal. Placement of the 2 implants was planned at sections 17 and 19 for correct mesio-distal positioning.
technique, first described by Schettler14 in 1976. This procedure has been performed recently in the posterior mandible with positive outcomes.15,16 Horizontal osteotomy with the interposition of bone in the form of a “sandwich” involves raising a coronal osteotomized segment of the mandible still attached to the lingual periosteum and interpositioning of an autogenous bone block graft. This guarantees greater vascularization of the inlay graft. Additionally, it allows optimum use of the basal bone, which is less prone to resorption.17 Frequently, however, these techniques are associated with autologous bone harvesting, causing discomfort and postsurgical morbidity. Often the patient can not undergo grafting techniques using autogenous bone, as these require
Furthermore, the use of a deproteinized bovine bone block is challenged by the extreme fragility of the block. A high risk of breakage during the shaping and placing of these blocks was described, and clinical results have shown insufficient vertical bone gain.9,10,19 For all these reasons, researchers have examined new graft materials that resorb more rapidly and that perfectly integrate with the surrounding bone.20 All these factors have lead clinicians to focus on the use of allogenic bone graft materials.21 These grafting materials are bonederived products harvested from cadavers, processed, and then sterilized. These graft types have been used for horizontal and vertical ridge regeneration.22–24 A limitation of the inlay technique is that it only corrects vertical and not horizontal defects.9,10,15 The presence
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of a horizontal defect of the residual bone crest does not permit sufficient horizontal bone augmentation. For these reasons, the authors propose a modified “sandwich” technique in the regenerative treatment of the horizontal bone ridge defects. This 2-stage technique was performed monolaterally in this case report to treat horizontal atrophy in an edentulous posterior mandible using mineralized and demineralized human bone allograft.
CASE REPORT A 47-year-old systemically healthy male was referred to the Oral and Maxillofacial Surgery Department of the University of Bologna (Italy) for a fixed prosthetic rehabilitation of the second premolar and molar zone of his posterior left mandible. A preoperatory panoramic radiograph and a cone beam computed tomography (CBCT) scan were performed to plan implant positioning and to evaluate alveolar residual bone anatomy (Figs. 1 and 2). The horizontal defect of the mandibular portion precluded correct implant insertion in the second premolar and first molar region (Fig. 2). The preoperative mean residual bone height above the left mental nerve foramen was 12 mm at section 15 (Fig. 2, A), 10 mm distal to the left mental nerve foramen at section 17 (Fig. 2, B), and 8.5 mm at section 19 (Fig. 2, C). The preoperative mean residual bone width was 3.4 mm above the left mental nerve foramen and 4 mm distal to the left mental nerve foramen (Fig. 2, A and B). A preliminary radiographic evaluation (panoramic and CBCT) was performed and dental casts made. A monolateral “sandwich” augmentation procedure was chosen to allow placement of 2 implants. The patient declined autogenous bone harvesting. Therefore, a regenerative procedure was proposed using a mixture of mineralized and demineralized human bone allograft in putty form (Readi Graft Crunch Putty; LifeNet, Virginia Beach, VA). The patient gave written informed consent to the treatment. The surgical procedure was performed monolaterally under local anesthesia (Fig. 3, A). The technique started
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Fig. 3. A, Preoperative clinical situation revealing atrophic horizontal crest. B, Paracrestal incision in the buccal vestibule. C, Exposition and isolation of mental nerve. D, Coronal segment preparation with piezoelectric device.
Fig. 4. A, Executed horizontal and distal cuts and unexecuted mesial cut to be performed 2 mm distal to first premolar. B, Sparing lingual periosteum. We intended to spare the periosteum by avoiding the use of a blade or dissector on the lingual side of the periosteum and consequently performed a form of tunnel technique on the lingual side.
with a paracrestal incision in the buccal vestibule and the subperiosteal tissues were dissected carefully with no tension on the ipsilateral mental nerve (Fig. 3, B and C) No mucoperiosteal dissection was performed toward the alveolar crest or on the lingual side. Three Piezosurgical inserts (OT8R, OT8L, and OT7; Mectron Piezosurgery Device; Mectron, Carasco, Italy) were used to create a horizontal osteotomy approximately 2 to 3 mm above the mandibular canal and 2
additional oblique cuts (Fig. 3, D). The mesial cut was made 2 mm distal to the last tooth in the arch, whereas the distal cut was made in relation to the implant graft treatment plane (Fig. 4, A and B). Sparing the lingual periosteum, the cranial segment was raised 2 mm (Fig. 5, A) and then drawn and rotated buccally approximately 4 mm (Fig. 5, B) to compensate the horizontal defect. The buccal surface of this repositioned cranial segment becomes the most
coronal part of the new regenerated crest (Fig. 5, C and D). The osteotomized segment was kept in this position with a titanium miniplate and miniscrews (KLS Martin, Tuttlingen, Germany) fixed to both the basal bone and the transported fragment (Fig. 6, A and B). The large gap between the cranial osteotomized segment and the mandibular basal bone was filled by gently injecting bone putty (Ready Graft Crunch Putty; LifeNet) (Fig. 6, A). A resorbable collagen membrane (Colla Guide, Riemser, Germany) was applied above the buccal surface of the surgical site (Fig. 7, A). After making periosteal releasing incisions to obtain tension-free closure, the flaps were sutured carefully with Vicryl 4.0 (Ethicon FS-2; Ethicon, St-Stevens-Woluwe, Belgium) (Fig. 7, B). Antibiotic therapy was amoxicillin (Ratiopharm GmbH, Ulm, Germany) at a loading dose of 2 g, with 2 g/d beginning the day after surgery for 10 days together with a nonsteroidal analgesic (ketoprofen, Orudis; Aventis Pharma, Bridgewater, NJ). Postsurgical instructions included a soft food diet for 2 weeks and appropriate oral hygiene with twice-daily rinsing with a 0.2% chlorhexidine digluconate mouthwash (Corsodyl; GlaxoSmithKline, London, UK). The sutures were removed 15 days postoperatively. CBCT assessment and panoramic radiograph were performed immediately after surgery (Figs. 8 and 9). The patient was examined clinically 1 week after surgery, twice in the first month, and once in each of the subsequent 3 months. No neurosensory disturbances were recorded. In the second surgical phase, 2 implants were correctly placed. The radiographic images showed the healed ridge after another 3-month period, at the reopening appointment (Fig. 10, A–C).
DISCUSSION In the posterior mandible, inlay bone grafting has obtained postoperative vertical bone gains of 4–8 mm9,19,25 with a low complication rate9,26 and low bone resorption before implant placement owing to high potential for bone graft incorporation17,25 and reported success rates $90%.10,26
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Fig. 5. A, Cranial segment raised approximately 2 mm. B, Cranial segment drawn and rotated buccally. C, During the rotation of the coronal segment, we obtained a partial dissection of the periosteum from the bone. The repositioned buccal surface becomes most coronal part of regenerated crest. D, Elevator to maintain correct segment position before fixation.
Fig. 6. A, Cranial osteotomized segment and mandibular basal bone gap filled with bone putty. B, Osteotomized segment kept in this position with titanium miniplate and miniscrews.
Fig. 7. A, Resorbable collagen membrane applied above buccal surface. B, Primary intention closure.
Inlay graft has a greater potential for bone incorporation because the graft is interposed between the basal bone and the osteotomized segment,15
permitting osteoblasts to come from both sides to colonize the interpositional block. However, in the present novel surgical technique, the thinner coronal
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segment is rotated exposing the lingual cortex to oppose the cancellous bone from the basal bone. This may influence incorporation of the graft because colonization of the osteoblasts occurs predominantly from the basal segment. Another important advantage with this technique is the preservation of the lingual periosteum, which maintains blood supply to the graft and may reduce resorption.15,17 In particular, inlay graft results in less bone resorption and more predictable outcomes compared to onlay graft that requires an overheightened bone block graft.27 The presence of native bone in the osteotomized coronal segment can explain why implant survival and success rates are comparable to those in native alveolar bone26 and also the limited amount of peri-implant marginal bone loss after loading.10 Additionally, this rapid integration with different kinds of graft10,15,16,19,27,28 leads to a reduction in the time required before implant installation and final rehabilitation. In fact, instead of the 5 to 6 months necessary when using GBR, it is possible to place implants after only 3 to 4 months,10,27,28 reducing patient waiting time. In the treatment of combined vertical and horizontal bone defects, GBR,6 osteodistraction,11,26 and boneblock grafts7 are recommended, even if the number of complications and failures of these augmentation techniques is still too high (well over 20%) to recommend widespread use of such procedures.13,26 However, this percentage is an overall assessment, burdened by the high rate of complications related to osteodistraction. In fact, there are many publications with low complication rates and high success, especially with regard to bone blocks.7,8 Nevertheless, the main limit of the inlay technique is that it only corrects vertical defects and does not permit correction of horizontal defects.9,10,15 In this case report, a horizontal defect of the residual bone crest was treated with a modified “sandwich” technique to obtain not only a limited vertical augmentation of the crest but also primarily a horizontal increase. In fact, the osteotomized cranial segment was slightly raised and then drawn and rotated
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Fig. 8. Postoperative CBCT. A, Coronal segment rotation. B, Miniplate and miniscrews. C, elevation and rotation of repositioned segment.
Fig. 9. Postoperative Panorex of posterior left mandible.
buccally to augment the horizontal width of the crest (Fig. 5, A and B). The buccal surface of the repositioned cranial segment became the most coronal part of the new regenerated crest (Fig. 5, C and D). In the traditional inlay technique, the fragment is only raised in a coronal direction permitting the interposition of the graft, whereas in this modified technique, the segment is also moved and rotated in the vestibular direction compensating for the horizontal defect and thus completely covering the interposed graft. However, thanks to this soft tissue management technique permitting preservation of the lingual periosteum, an adequate blood supply to both the thin osteotomized segment and the graft was maintained. Surgical differences with GBR and block graft procedures necessitating the elevation of a lingual flap are therefore evident.
Fig. 10. Radiographic images of healed alveolar ridge at the reopening appointment. A, X-ray image of the posterior left mandible. B, CBCT showing the augmented area at the second premolar site. C, CBCT showing the augmented area at the first molar site.
Atrophic bone crests of less than 5 mm in width are considered to require regenerative procedures to create a bony wall of at least 1 mm around implants and provide successful long-term function.29 Spilt-crest techniques have also been proposed for this kind of horizontal defect.30 One-stage31 or 2-stage32 splitcrest techniques determine an increase in the width of the ridge, but do not provide vertical bone gain, as described in the present case report using a modified “sandwich” technique. Autografts are considered the gold standard for their osteogenic, osteoinductive, and osteoconductive properties.33 It is often impractical, however, to harvest the necessary amount of autologous bone block to reconstruct extensive defects. In addition, harvesting of autologous blocks entails patient discomfort due to doubling of the surgical site, postoperative morbidity, and complications, including nerve damage, gingival recession, edema, and loss of tooth vitality.18 The use of allografts23,34 and xenografts9,10 has been advocated to avoid all the cited problems. Allografts show better histomorphometric results and a higher resorption rate than xenografts.35 In this case report, the authors did not use a human bone block graft to fit the gap between the coronal osteotomized segment and the basal bone, but preferred to fill it with a mixture ofmineralized and demineralized allograft in putty form to obtain a better and quicker revascularization of the graft from the native bone. This mixture should offer the following additional advantages: the mineralized allograft is an osteoconductive material with relatively slow resorption,36 whereas demineralized bone matrix is considered to have osteoconductive capacity in intraoral edentulous sites36 and osteoinductive potential, as demonstrated by bone formation, when implanted submuscularly in animals.37,38 This combination should be advantageous, in that the demineralized bone matrix stimulates new bone formation and mineralized allograft offers a scaffold for bone deposition and remodeling as demonstrated in sinus elevation procedures.39
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CONCLUSION Within the limits of this case report, the clinical outcome suggests that the modified sandwich technique’s capabilities in horizontal bone reconstruction in the atrophic mandible eliminate problems caused by autologous bone graftings. Further research will confirm or refute potentially advantageous properties of this technique compared to other regenerative procedures for the treatment of horizontal defects in the posterior atrophic mandible.
DISCLOSURE The authors claim to have no financial interest, either directly or indirectly, in the products or information listed in this article.
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