Abstract

This clinical case report describes and demonstrates successful use of recombinant human platelet-derived growth factor (rhPDGF-BB) in conjunction with autogenous bone, anorganic bone mineral, and barrier membranes to reconstruct severe alveolar bone defects. A combined sinus augmentation and vertical alveolar ridge augmentation was successfully performed. In addition, a significant amount of periodontal bone gain was achieved in close apposition to a previously denuded root surface, which is significant from a periodontal standpoint, given the possibility of vertical periodontal regeneration.

Introduction

Vertical and horizontal alveolar ridge augmentation utilizing guided bone regeneration (GBR) has become a significant treatment option to provide optimal bone support for osseointegrated dental implants. The surgical technique and application of GBR for supracrestal regeneration have been described previously,1 and the first animal and human histologic studies demonstrated successful vertical bone augmentation.2,3 Long-term results concluded that vertically augmented bone using GBR techniques responds to implant placement in a similar fashion to native, nonregenerated bone.4,5 

The GBR technique for vertical bone augmentation was used in combination with a subantral augmentation procedure for posterior maxillary reconstruction utilizing machined surface implants. However, implant survival and success rates were 92.1% and 76.3%, which conflicted with previously reported results on vertical and horizontal GBR.6 

A potential solution for overcoming this difference in results could be the use of bone inductive growth factors. This may enhance the development of mature lamellar bone, which possibly could support dental implants sooner and more predictably.

The safety and efficacy of recombinant human platelet-derived growth factor (rhPDGF-BB) have been demonstrated for periodontal regeneration.7 Results of a preclinical canine study demonstrated that purified recombinant PDGF-BB, used in combination with a deproteinized bovine block, and without placement of a barrier membrane, has the potential to regenerate significant amounts of new bone in severe mandibular ridge defects.8 

Several case studies utilizing various combinations of autogenous bone, anorganic bovine-derived bone mineral (ABBM) (Bio-Oss, Geistlich Pharma AG, Wolhusen, Switzerland), and rhPDGF-BB were published recently and report successful histologic and clinical results.9,10 

This clinical case report describes and demonstrates the successful use of rhPDGF-BB in conjunction with autogenous bone, anorganic bone mineral, and barrier membranes to reconstruct severe alveolar bone defects.

Case Presentation

A 30-year-old healthy female patient presented for an evaluation of her posterior right maxilla, which had a history of dentoalveolar infection. Significant clinical findings included several fistulous tracts and periodontal probing depths of up to 10 mm around teeth Nos. 2, 3, and 4. Although the 3 teeth were splinted together, advanced mobility of the entire 3-unit prosthesis was evident. Radiographic examination revealed advanced periodontal bone loss with associated periapical lesions (Figure 1).

The prognosis was poor, and extraction was performed. Following a 2-month healing period, a severe vertical ridge defect was noted as anticipated, which also was visible during her smile. This caused an esthetic concern for the patient (Figure 2). The vertical defect in close proximity to the floor of the sinus significantly compromised the site with regard to implant reconstruction (Figure 3). The patient desired a fixed reconstruction; therefore, the clinical plan was to regenerate the alveolar defect to ideally reconstruct form and esthetics and subsequently place implants to support a fixed prosthetic restoration.

Surgical Procedure

The patient was premedicated with amoxicillin 2 g 1 hour before surgery and was given 500 mg penicillin 3 times a day for 1 week following the surgery. The patient rinsed with 0.12% chlorhexidine solution (Peridex) for 1 minute; the patient's skin surrounding the surgical site was disinfected, and a sterile surgical drape was applied to minimize potential contamination from extraoral sources. A full-thickness, midcrestal incision was made in the keratinized gingiva on the alveolar crest. For adequate surgical access, a divergent vertical incision was made at the mesial line angle of tooth No. 6. After primary incisions were made, periosteal elevators were used to reflect a full-thickness flap beyond the mucogingival junction and at least 5 mm beyond the bone defect. A rectangular antrostomy with rounded corners was created with a round diamond bur at the lateral wall of the maxillary sinus. The sinus window was infractured and the sinus membrane was reflected carefully with sinus curettes and was elevated with care to prevent perforations (Figure 4). With a small round bur, the recipient bony bed was prepared with multiple decortical holes to expose the medullary space. Autogenous bone was harvested from the right ascending ramus and was particulated in a bone mill (R. Quétin Bone-Mill, Roswitha Quétin Dental Products, Leimen, Germany). The autogonous bone was mixed with ABBM (Bio-Oss, Geistlich Pharma AG) and then was hydrolyzed in rhPDGF-BB (Gem 21, Osteohealth, Shirley, NY). An appropriate-sized, titanium-reinforced expanded polytetrafluoroethylene membrane (e-PTFE) (GORE-TEX Regenerative Material Titanium Reinforced, W.L. Gore & Associates, Flagstaff, Ariz) was selected and trimmed with consideration of graft volume. The membrane was fixated first on the palatal side using multiple titanium pins. The bone graft then was placed within the subantral space and appositionally on the vertical alveolar defect. The membrane was folded over onto the buccal alveolus and fixated with additional titanium pins (Figure 5). The mesial border of the e-PTFE membrane was placed 4 mm from the distal surface of tooth No. 4 to prevent membrane exposure. The mesial end of the membrane was unfilled for about 2 mm supracrestally (Figure 6). This area was filled with additional bone graft, connecting the denuded root surface to the open end of the membrane (Figure 7). A resorbable collagen membrane (Bio-Gide Resorbable Bilayer Membrane, Osteohealth) then was applied to protect and contain this area in an attempt to minimize postoperative complications (Figure 8). An additional collagen membrane was applied to cover the sinus window. Periosteal releasing incisions were made to provide adequate flap reflection for tension-free primary closure. The flap was closed (GORE-TEX CV-5 Suture, W.L. Gore & Associates) in 2 layers with the use of horizontal mattress and single interrupted sutures.

Medications were followed as described earlier. In addition, an anti-inflammatory medication, 50 mg diclofenac (Voltaren XR) was prescribed 3 times a day for 1 week following surgery. For chemical plaque control, 0.12% chlorhexidine solution was used daily from 24 hours post surgery until the time of suture removal. Postoperative swelling was remarkable, reaching maximum at 48 hours postoperatively. Swelling gradually subsided but was still visible at 1 week and disappeared completely after 10 days. Postoperative discomfort usually was associated with tension from the swelling. Pain was negligible, however. No other symptoms occurred during the postsurgical period.

To avoid postsurgical trauma, a removable appliance was not utilized. After a previously described 9 months of uneventful healing, the area was explored employing the same full-thickness flap design.3 The membrane had maintained its original position, and bone growth was evident over the membrane in the area where the resorbable collagen membrane was utilized (Figure 9). After removal of the titanium pins and the e-PTFE membrane, complete vertical bone regeneration was observed. The defect between the distal surface of tooth No. 4 and the e-PTFE membrane also demonstrated complete bone fill. About 2 mm of the previously denuded root surface of tooth No. 4 was also in intimate contact with bone (Figure 10).

Three Branemark TiUnite implants were placed (Nobel Biocare, Yorba Linda, Calif) in accordance with the manufacturer's protocol (Figure 11). During implant placement, a collagen membrane (Bio-Gide Resorbable Bilayer Membrane, Osteohealth) was placed empirically over the newly formed crestal bone to protect the graft from possible early resorption.

The implants were submerged through a 2-stage technique for 6 months and then were uncovered and restored with a splinted, 3-unit implant supported fixed partial denture (Figures 12 and 13).

Discussion

rhPDGF-BB has demonstrated safety and efficacy for periodontal regeneration in previous studies.7 It has been shown both in a preclinical canine study8 and in subsequent case reports that PDGF has the potential to regenerate significant amounts of supracrestal bone in conjunction with ABBM and autogenous particulated bone.9,10 

This case report demonstrates that significant vertical bone regeneration is possible in a demanding clinical defect in the posterior maxilla. Conflicting results of posterior maxillary vertical regeneration have been reported previously. In one study,5 100% success rates were reported using enhanced surface implants (Ti-Unite, Nobel Biocare) after vertical GBR, whereas another study reported implant survival and implant success rates of 92% and 76%, respectively, when machined surface implants were used.6 Both studies used the success criteria delineated by Albrektsson et al.11 In this case report, a combined subantral augmentation and vertical alveolar ridge augmentation was performed successfully, leading to 100% implant success11 and survival over 12 months for these 3 implants. In addition, a significant amount of periodontal bone gain was achieved in close apposition to a previously denuded root surface, which is significant from a periodontal standpoint, given the possibility of vertical periodontal regeneration.

This limited case report demonstrates remarkable vertical bone regeneration and perhaps periodontal regeneration using rhPDGF-BB in conjunction with autogenous bone, anorganic bone mineral, and barrier membranes. No controls were included in this case report. In the future, controlled studies are needed to evaluate the extent of benefit derived when PDGF is used. Continued follow-up will be necessary to investigate long-term implant success, as well as stability of the newly regenerated bone around the implants and the natural tooth.

This treatment modality has the potential to eliminate completely the need for bone harvesting; preliminary results are encouraging. However, the clinician should recognize that clinical information regarding this technique, including information on resorption of the regenerated bone, implant survival, and crestal remodeling around the implants, is currently limited. Further documentation using controlled long-term, randomized, clinical trials is necessary before this new treatment technique can be recommended for routine clinical practice.

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Author notes

Istvan A. Urban, DMD, MD, is Assistant Professor, Graduate Implant Dentistry, Loma Linda University, Loma Linda, Calif, and is in private practice in Periodontics and Implant Dentistry in Budapest, Hungary. Address correspondence to Dr Urban at Sodras utca 9, Budapest, Hungary 1026. (e-mail: istvan@implant.hu).

Nicholas Caplanis, DDS, MS, is Assistant Professor, Graduate Implant Dentistry, Loma Linda University, Loma Linda, Calif, and is in private practice in Periodontics and Implant Dentistry in Mission Viejo, Calif.

Jaime L. Lozada, DDS, is Professor, Department of Restorative Dentistry, Director of Graduate Implant Dentistry, LomaLinda University, Loma Linda, Calif.