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Reconstruction of the Narrow Ridge Using Combined Ridge Split and Guided Bone Regeneration with rhPDGF-BB Growth Factor–Enhanced Allograft

Tat Chiang, DMD1/Ana Lucia Roca, DDS, MDS2/Sylwia Rostkowski, DMD2 Howard J. Drew, DMD3/Barry Simon, DDS, MSD4 In clinical situations where the presence of severe horizontal ridge deficiencies precludes simultaneous implant placement and bone augmentation, a staged approach may be desirable to allow optimal implant placement. Numerous therapeutic options are available for the treatment of the horizontally deficient ridge. With advances in tissue engineering, the use of growth factors can significantly improve wound healing with more rapid bone formation and maturation. These case reports demonstrate a technique that enhances the predictability of horizontal bone gain with reduced surgical trauma and postoperative complications. Recombinant human platelet-derived growth factor BB (rhPDGF-BB) in combination with particulate allograft is used to stimulate the proliferation and migration of osteogenic cells. A ridge split technique with vertical bone incisions allows expansion and mobilization of the buccal plate, creating a space that will contain the particulate graft material. Decortication of the mobilized buccal plate will create pathways to allow cellular and vascular access for enhanced maturation. Additional graft material is placed lateral to the mobilized buccal plate to increase apical ridge width. The use of piezoelectric surgery enables a precise crestal bony incision in severely deficient ridge widths and aids in faster wound healing. This study discusses the technique and the recommended therapeutic considerations to ensure predictable regeneration of adequate bone for optimal implant placement in horizontally deficient ridges. (Int J Periodontics Restorative Dent 2014;34:123–130. doi: 10.11607/prd.1633)

Clinical Associate Professor, Department of Periodontics, New Jersey Dental School, Newark, New Jersey, USA. 2Postgraduate Student, Department of Periodontics, New Jersey Dental School, Newark, New Jersey, USA. 3Clinical Professor, Department of Periodontics, New Jersey Dental School, Newark, New Jersey, USA. 4Professor, Department of Diagnostic Sciences, New Jersey Dental School, Newark, New Jersey, USA. 1

Various techniques have been used to restore the noncontained horizontal bone dimension. Autogenous block grafts obtained from the symphysis, ramus, tori, and extraoral sites have been considered the gold standard for therapy. However, patient morbidity concerns, such as neurosensory alterations, chin ptosis, lip incompetence, block and jaw fractures, and damage to adjacent teeth, are found. In addition, significant resorption of up to 50% of the block graft has been documented.1,2 Alternative successful therapies for horizontal ridge augmentation include guided bone regeneration (GBR) with particulate grafts (with or without the use of tenting screws), titanium mesh combined with particulate grafts with or without the addition of aqueous growth factors (recombinant human morphogenetic protein 2 [rhBMP-2] or recombinant

Correspondence to: Dr Ana Lucia Roca, Department of Periodontics, New Jersey Dental School, 110 Bergen Street, Newark, NJ 07103; email: [email protected] Tat Chiang and Ana Lucia Roca shared equally in this study and both are primary authors. ©2014 by Quintessence Publishing Co Inc.

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124 human platelet-derived growth factor BB [rhPDGF-BB]), distraction osteogenesis, ridge expansion with osteotomes, and ridge splitting techniques.3 GBR for noncontained horizontal defects often requires a more rigid scaffold such as titanium-reinforced nonresorbable membranes for space maintenance. Soft tissue management for primary flap closure is necessary, since high risk of membrane exposure has been reported,4 leading to early complications, such as infections and insufficient bone volume formation. Resorbable membranes with tenting screws for space maintenance have been advocated to minimize these complications5; however, it is often difficult to maintain the desired shape and volume of the augmented bony ridge. Additionally, large sites require multiple screws, adding cost and time to the procedure. In case reports, the use of rhBMP-2 has been shown to be predictable and successful for bone formation,6,7 but the procedure is costly and has a high incidence of extensive postoperative swelling and bruising despite the use of systemic steroids.7 Ridge split procedures with simultaneous implant placement have been shown to be predictable if primary stability and an intact laterally mobilized buccal bone flap are achieved. However, there are instances where there are anatomical limitations or inadequate bone volume for optimal prostheticdriven implant placement that may preclude simultaneous implant treatment. In the maxillary anterior region, the presence of extensive

labial concavities is a common occurrence. This may limit optimum implant placement for proper esthetics, function, and phonetics. In the mandible, a thick, dense cortical plate and inelasticity of the bony segment is often found. Bravi et al8 reported that because of the high rate of complete buccal wall fractures in the posterior mandible, 44% of ridge split procedures required a two-stage protocol. The authors had encountered buccal plate fractures at the time of simultaneous implant placement and hypothesized that this could be from drilling vibrational forces or overstressing the elastic properties of the buccal cortex. In the following cases, rhPDGFBB is used to enhance bone formation and maturation of the allograft. The signaling molecule rhPDGF-BB is capable of stimulating cellular events associated with tissue regeneration. It has chemotactic and mitogenic effects on fibroblasts and osteoblasts and stimulates angiogenesis, which promotes bone regeneration and faster wound healing.9 The modified ridge split includes vertical bony incisions (5 to 8 mm) prior to an expansion of 30 to 40 degrees to create a 3- to 5-mm intraosseous space. The mobilized bony plate acts similarly to tenting screws to support the volume of the particulate graft placed buccal to the plate and to prevent collapse when the flap is sutured. Decortication of the buccal plate creates pathways for cellular and vascular access to the graft. These pathways may allow the continuous signaling effect of

the rhPDGF-BB to upregulate osteogenic cells to migrate to the graft particles placed outside of the mobilized buccal plate. Piezoelectric surgical cuts were used to minimize trauma and enable more precise bony incisions, which aided in faster wound healing.10 The following cases demonstrate a staged approach using piezoelectric surgery and allograft in combination with purified recombinant human platelet-derived growth factor (rhPDGF-BB) to improve wound healing and increase bone maturation for a significant gain in horizontal width and volume.

Method and materials The patients selected for implant treatment had completed periodontal and restorative evaluations, and any active diseases were controlled prior to surgery. Cone bean computed tomography (CBCT) was used for case selection. Two grams of amoxicillin were given 1 hour before surgery. A chlorhexidine prerinse was prescribed. Following administration of local anesthetic (2% xylocaine with 1:100,000 epinephrine), a full-thickness mucoperiosteal flap was elevated to expose the buccal bony defect and to facilitate the placement of particulate graft lateral to the mobilized buccal plate (Fig 1). Piezoelectric surgery (Mectron) with a setting of bone quality 1 and an OT7 surgical tip was used to perform the crestal and vertical bony incisions. The crestal horizontal incision extended 5 to 8 mm subcrestal and

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Apical discharge corticotomy

Crestal corticotomy

Vertical corticotomy

Full-thickness flap

Nerve

Fig 1    Full-thickness flap to access defects and perform necessary bony corticotomies.

Fig 2    Extension of crestal corticotomy allows progressive access of osteotomes; note the additional expansion of buccal plate as the apical corticotomy collapses.

Decortication Membrane Particulate graft with rh-PDGF Apical discharge corticotomy

Fig 3    Self-contained space within ridge, buccal decortications, GBR, and primary closure.

1 mm from the adjacent teeth. Subsequently, vertical cuts were made at the lateral aspects to completely transect the buccal cortical plate. In the posterior mandible, where a thick buccal cortex was present, an additional apical corticotomy was performed to aid in the mobilization of the split buccal plate. This bony incision did not fully transect the buccal cortex and acted as a hinge for the labial movement of the buccal bony plate. Upon

completion of the corticotomies, ridge expansion chisels were used to widen the ridge (Fig 2). After initially expanding the ridge by 1 to 2 mm, decortication of the apical half of the mobilized plate was performed with a 1/2 round bur. The decortications were a minimum of 5 mm apart to avoid compromising the vascular supply and integrity of the plate. Intramarrow penetration was performed apical to the split ridge to allow access for

osteo­progenitor cells. At this time, the ridge expansion was continued, creating the required osseous space. Crushed cortical freezedried bone allograft (FDBA) of 300 to 500 µm was hydrated with sterile water for a minimum of 15 minutes. The material was then thoroughly dried and rehydrated with rhPDGFBB (GEM 21S, Osteohelath) for at least 10 minutes. The rhPDGF-BB– enhanced FDBA was placed firmly into the intraosseous bony defect

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Fig 4    Reflection of a papillary sparing full-thickness flap keeping the buccal keratinized tissue around canines.

Fig 5    Depiction of the corticotomies. Due to the nasal spine, an additional corticotomy was necessary to allow for adequate expansion.

Fig 6    The graft material is placed into the created ridge space and over the buccal concavity. A resorbable membrane is adapted over the area.

Fig 7    CBCT showing pre- and postgrafting with bone augmentation greater than 5 mm.

created with the ridge split procedure and lateral to the mobilized buccal plate. A resorbable collagen membrane (Ossix Plus OraPharma and/or Bio-Gide, Geistlich), was used to contain the graft material (Fig 3). Periosteal releasing incisions with horizontal mattress and interrupted sutures were used to obtain tension-free primary closure. Remaining rhPDGF-BB was applied to the inside of the flap and incision lines after suturing (Vicryl Ethicon or Cytoplast PTFE, Osteogenics Biomedical). The patients were prescribed amoxicillin 500 mg, three times per day for 1 week; chlorhexi-

dine rinses twice per day; and a Medrol Dose pack (methylprednisolone) to control postoperative swelling. The initial postoperative visit was scheduled 10 to 14 days after surgery.

Case reports Patient no. 1

A 50-year-old woman with a nonsignificant medical history presented with an edentulous maxillary anterior area extending from the right to left lateral incisors. Teeth

were lost due to trauma 7 years prior to the procedure (Fig 4). Based on CBCT evaluation, the width of the alveolar ridge was less than 3 mm with a severe buccal concavity in the area of the right incisors. The treatment plan included placement of two implants in lateral incisor sites for an implant-supported fixed partial denture. Due to the anatomy of the ridge and thick cortical bone, the design included an additional midline corticotomy to facilitate bone expansion (Fig 5). Following expansion, the GBR procedure was completed (Fig 6), and passive

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127 primary closure was achieved by periosteal incisions with horizontal mattress and interrupted sutures. Prior to implant placement, a follow-up CBCT was taken (Fig 7). Following a healing period of 6 months, a full-thickness flap was reflected, and a gain of over 5 mm in width could be observed. Using a surgical guide, two implants were placed in the lateral incisor sites (Fig 8). Figure 9 depicts the patient 2 years after treatment.

Fig 8    A papillary sparing full-thickness flap to expose the augmented site and an acrylic resin surgical guide are used to aid in proper implant placement.

Fig 9    Final prosthesis.

Fig 10    A mucoperiosteal flap reveals the severe atrophic ridge; note, width less than 3 mm.

Fig 11    The apical corticotomy to guide the buccal plate.

Patient no. 2

A 41-year-old woman presented with a negative medical history. CBCT and clinical examination revealed a significantly resorbed ridge. The crest was approximately 2 mm, widening at the base (Fig 10). An apical corticotomy was performed in addition to the crestal and vertical incisions because of the inelasticity of the buccal plate and thick cortex (Fig 11). Bone chisels were used to expand the ridge, and decortication of the plate and GBR were performed. At 4 months, the site was revisited and more than 5 mm of horizontal width gain was observed; two implants were placed in an optimum position to support a three-unit fixed partial denture (Fig 12).

Fig 12    Substantial gain in width upon flap elevation was achieved to place implants.

Patient no. 3

A 45-year-old woman with a nonsignificant medical history presented with loss of her maxillary left lateral incisor and canine due

to severe caries. Upon evaluation, a severe buccal concavity was evident. The residual crestal width was less than 2 mm. Crestal

and vertical corticotomies were performed. Following expansion, the buccal plate was decorticated (Fig 13) and GBR procedures were

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Fig 13    A round bur was used to decorticate the buccal plate.

Fig 14    At stage-two surgery, an adequate ridge was found for optimum implant placement.

Fig 15    Final restoration evaluation after 2 years.

completed. Four months later, a gain of more than 5 mm in width was found (Fig 14) and two implants were placed. Figure 15 depicts the restoration after more than 2 years in function.

ed a substantial increase in bone width by using a technique that consisted of ridge splitting in combination with expansion via round and flat osteotomes.11 Mazzoco et al used motorized ridge expanders (MREs) for lateral ridge augmentation and measured the amount of bone augmentation at 6 months. The results found were 1.5 mm of horizontal gain at the coronal portion and 1.6 mm at 5 mm from the crest when MREs were used.13 Vercellotti was able to gain 2 to 3 mm in width by using a piezoelectric device in the edentulous ridge expansion technique.10 The present case reports follow the principle of tissue engineering for bone formation. Three basic elements must be present and work together: a signal, cells, and a scaffold matrix.9 Simion et al reported excellent clinical and histologic bone augmentation when using rhPDGF-infused Bio-Oss blocks for vertical augmentation without membranes in an animal study.14 Results reported included chemotaxis, mitogenesis, and proliferation of osteoblasts and fibroblasts.

Another benefit of using rhPDGF-BB is the positive effect on angiogenesis, which promotes blood vessel proliferation and capillary budding into the graft, both of which are important for bone regeneration.9 The scaffold matrix used was mineralized cortical FDBA. For growth factor–mediated tissue regeneration, the scaffold matrix has to have good binding and releasing properties.15 The use of FDBA has been shown to have satisfactory binding properties for rhPDGF-BB; this combination resulted in robust bone formation.15 Typically, during implant placement, the quality of the regenerated bone is hard and firm and resistant to drilling similar to type 2 and 3 bone. In a recent study by Nevins et al,16 the authors used a mineral collagen bone substitute hydrated with rhPDGF-BB without membranes in extraction sites with a minimum or absence of labial plates. Significant clinical and histologic new bone formation was reported. Further studies will be needed to evaluate this vehicle as an appropriate scaffold matrix and

Discussion There are times when ridge splitting with simultaneous implant placement is not predictable and a staged approach is more appropriate because of reduced complications. Traditional GBR procedures are based on the exclusion of epithelium and connective tissue with a barrier membrane allowing the osteogenic cells to migrate into the osteoconductive matrix. This represents passive therapy. With advances in tissue engineering, these cases illustrate bioactive therapy, where growth factors are used to actively recruit healing cells to aid in wound healing and faster bone formation. Various techniques using twostage approaches to gain moderate horizontal width have been reported.11–13 Elian et al document-

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129 carrier for rhPDGF-BB for lateral ridge augmentation. In addition, Sarment et al17 in a periodontal wound healing study measured the bone turnover marker pyridinoline cross-linked carboxyterminal telopeptide of type I collagen in gingival crevicular fluid. Results indicated that the effect of rhPDGFBB on the upregulation of bone turnover and bone wound healing would continue for 6 to 12 weeks postplacement of rhPDGF. Bravi et al reported that as a result of the inelastic thick buccal cortical bone in the posterior mandibular area, the risk of fracture is high. They reported that 44% of mandibular sites required a twostage technique to avoid the risk of malfracture due to lack of elasticity of the posterior mandibular buccal plate, as opposed to only 1.5% of sites in the maxilla.8 To overcome the problems encountered during single-stage ridge splitting, Enislidis et al18 used a two-staged approach to create a “pedicle graft” for the future implant site. A full-thickness flap and a rectangular complete buccal corticotomy were performed followed by a healing period of 40 days. Thereafter, a partial-thickness flap was elevated and the buccal plate was laterally displaced with the attached periosteum and its vascular supply intact. This approach allows for the location of the greenstick fracture to be established in advance. The technique described in this report uses an apical corticotomy in areas where there is inelasticity of bone associated with a thick cortical bone. The purpose of the

apical bony incision is to guide the greenstick fracture. This corticotomy should not transverse through the cortical plate into the marrow spaces, as illustrated with patient no. 2. In addition, the authors found that in large areas requiring augmentation, as documented in patient no. 1, a third additional vertical corticotomy greatly eases the mobilization of the segmented buccal plate. Other authors using ridge-split techniques have used similar cuts.12,13,19 A piezolectric surgery unit was used for all bony cuts in the present study. This allowed for precise, controlled cuts and faster and less traumatic healing when compared with the use of burs and saws, as reported in histologic and biomolecular studies by Vercelloti et al.20 Primary soft tissue healing is essential for successful ridge augmentation, and the use of rhPDGF-BB applied to the soft tissue incision lines appears to have a positive effect on soft tissue healing and maintenance of the intact incision and greatly reduces the occurrence of membrane exposure.21

Conclusion Bioactive therapy using a combined split ridge technique with modified GBR is a viable technique for horizontal augmentation of the narrow residual ridge. The technique, when properly performed, has low morbidity with significant horizontal bone gain. With the use of ridge splitting, piezoelectric surgery, allografts with rhPDGF-BB

growth factors, and GBR on the external surface of the laterally spread buccal plate, significant amounts of bone can be augmented predictably on the deficient ridge for optimum prosthetic-driven implant dentistry.

Acknowledgment The authors reported no conflicts of interest related to this study.

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 9. Nevins M, Hanratty J, Lynch SE. Clinical results using recombinant human platelet-derived growth factor and mineralized freeze-dried bone allograft in periodontal defects. Int J Periodontics Restorative Dent 2007;27:421–427. 10. Vercellotti T. Piezoelectric surgery in implantology: A case report—A new piezoelectric ridge expansion technique. Int J Periodontics Restorative Dent 2000;20: 359–356. 11. Elian N, Ziad J, Ehrlich B, et al. A twostage full arch ridge expansion technique: Review of the literature and clinical guidelines. Implant Dent 2008;17: 16–23. 12. Holtzclaw D, Toscano J. Rosen PS. Reconstruction of posterior mandibular alveolar ridge deficiencies with the piezoelectric hinge-assisted ridge split technique: A retrospective observational report. J Periodontol 2010;81:1580–1586. 13. Mazzoco F, Nart J, Cheung W, Griffin T. Prospective evaluation of the use of motorized ridge expanders in guided bone regeneration for future implant sites. Int J Periodontics Restorative Dent 2011; 31:547–554.

14. Simion M, Rocchietta I, Kim D, Nevins M, Fiorellini J. Vertical ridge augmentation by means of deproteinized bovine bone block and recombinant human plateletderived growth factor-BB: A histologic study in a dog model. Int J Periodontics Restorative Dent 2006;26:415–423. 15. Nevins M, Camelo M, Nevins ML, Lynch SE. Periodontal regeneration in humans using recombinant human platelet-derived growth factor-BB (rhPDGF-BB) and allogenic bone. J Periodontol 2003;74:1282–1292. 16. Nevins M, Camelo M, Schupbach P, Nevins M, Kim S, Kim D. Human buccal plate extraction socket regeneration with recombinant human platelet-derived growth factor BB or enamel matrix derivative. Int J Periodontics Restorative Dent 2011;31:481–492. 17. Sarment DP, Cooke JW, Miller SE, et al. Effect of rhPDGF-BB on bone turnover during periodontal repair. J Clin Periodontol 2006;33:135–140.

18. Enislidis G, Wittwer G, Ewere R. Preliminary report on a staged ridge splitting technique for implant placement in the mandible: A technique note. Int J Oral Maxillofac Implants 2006;21:445–449. 19. Blus C, Szmukler-Moncler S. Split-crest and immediate implant placement with ultra-sonic bone surgery: A 3-year lifetable analysis with 230 treated sites. Clin Oral Implant Res 2006;17:700–707. 20. Vercellotti T, Nevins M, Kim D, et al. Osseous response following resective therapy with piezosurgery. Int J Periodontics Restorative Dent 2005;25:543–549. 21. Wang HL, Boyapati L. “PASS” principles for predictable bone regeneration. Implant Dent 2006;15:1:8–17. 22. Nevins M, Al Hezaimi K, Schupbach P, Karimbux N, Kim D. Vertical ridge augmentation using an equine bone and collagen block infused with recombinant human platelet-dervived growth factor-BB: A randomized single-masked histologic study in non-human primates. J Periodontol 2012;83:878–884.

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Reconstruction of the narrow ridge using combined ridge split and guided bone regeneration with rhPDGF-BB growth factor-enhanced allograft.

In clinical situations where the presence of severe horizontal ridge deficiencies precludes simultaneous implant placement and bone augmentation, a st...
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