| Abstract|| |
The challenge of correcting deficient vertical alveolar height for dental implant placement has been there since dental implants came in to regular clinical placement. The ability of various methods to increase the residual alveolar height has met with varying results. The primary reason is that the techniques were not quite successful in maintaining the required residual alveolar height. Use of Bone Morphogentic Protein, especially rhBMP-2 has been met with high degree of success in deficient vertical alveolar height in a mandibular ridge. The demonstration of this using a case has been presented here.
Keywords: Ameloblastoma, bone morphogenetic proteins, dental implant, tissue engineering, vertical bone augmentation
|How to cite this article:|
Balaji S M. Augmentation of residual alveolar bone height with tissue engineering for dental implant placement. Indian J Dent Res 2014;25:410-2
Large mandibular defect as a consequence of tumor removal leads to functional and esthetic compromise. Such defect could lead to difficulties with speech and eating, loss of support, loss of vertical dimension, an aged face and a reduced range of expression, whereas prosthesis would lack insufficient retention. Given this situation, the routine activities of patient are compromised. Dental implants offer a permanent and reliable solution for this problem. Widespread use of dental implant system and better advances in preprosthetic surgery has led to better results when such implant systems are used. However, the vertical height of the residual mandibular bone will be a problem in the situation. Surgical methods for vertical height gaining in this situation would be autogenous bone block grafting as the only possibility as it has the maximum osteogenic potential and remains the most reliable method.  However, such method has a 0-25% chance of the grafted bone being resorbed most of it after connecting implant abutments. 
|How to cite this URL:|
Balaji S M. Augmentation of residual alveolar bone height with tissue engineering for dental implant placement. Indian J Dent Res [serial online] 2014 [cited 2020 Sep 26];25:410-2. Available from: http://www.ijdr.in/text.asp?2014/25/3/410/138360
Bone morphogenetic proteins (BMPs) are a group of osteoinductive signaling protein molecules that mediate bone volume, skeletal organogenesis and bone regeneration. These molecules, particularly the BMP-2 act at the cellular level causing proliferation, differentiation and extracellular osteo-matrix formation. They also attract and stimulate the adult mesenchymal stem cells to form bone. This eliminates the need for unreliable alloplastic substitutes, risky xenografts as well as issues related to autografts. BMP-2 can be synthesized by recombinant technology. This manuscript intends to produce a novel way to increase the vertical height of a postsurgical defect of mandible in a novel way using only rhBMP-2 along with conventional way.
| Case report|| |
A 29-year-old male sought treatment for a well-circumscribed ameloblastoma of mandible. The growth was present for about 2 years. At the presentation, the growth measured 7.5 × 2 × 4.8 cm in maximum dimension. Cortical bone was eroded in four different places [Figure 1]a and b].
After investigations, surgical planning was performed. Considering the benign biological potential of the tumor, an en-bloc removal of the tumor with preservation of lower cortex of mandible and sufficient wide margin along the proximal side was planned. In areas of breach, complete removal of adjacent soft tissues was also performed
|Figure 1: (a) Preoperative intraoral view, (b) CT scan showing ameloblastoma in right mandible|
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[Figure 2]a and b]. The posttreatment functional rehabilitation was also considered. As the defect was huge, immediate functional replacement was not a possibility. In an attempt to restore normalcy during excisional surgery, the defect was reconstructed with rib graft. The graft was secured with titanium screws [Figure 3]a and b] overlaid with rhBMP-2 [Figure 4] as per then evidence.  As the vertical height of bone would decrease with implant loading  placement of rhBMP-2 was considered along with implant placement. Later, after adequate healing [Figure 5], six dental implants (Nobel Biocare, Sweden, 13 mm length, - diameter) of appropriate length were chosen and fixed [Figure 6]a and b] after sub-periosteal placement of rh-BMP2 in Absorbable Collagen Sponge carrier. The entire periosteum had been previously dissected along with tumor. The implants were allowed to heal and after 3 months period, the super structures were placed as per standard procedure [Figure 7]. The patient is being followed for about 30 months without any complications.
|Figure 2: (a) En-bloc removal of the tumor, (b) Ressected portion of the mandible|
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|Figure 3: (a) Rib graft harvested (b) Graft secured with titanium screws|
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|Figure 5: Reconstructed mandibular alveolar ridge after complete healing|
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| Discussion|| |
It has been shown through animal studies that vertical bone augmentation (VBA) was enhanced by the application of rhBMP-2 with cortico-cancellous human bone block  as observed in current report. Replacement of such postsurgical defect of mandible for complete functional rehabilitation requires complex treatment such as microvascular surgery  or stem cell therapy,  which are at their preliminary stages. Moreover, these procedures are time consuming and the economic viability is being tested. There were no long-term data on such therapy or published literature at the time of the case rehabilitation. Use of rhBMP-2 with bone graft for lost oro-facial structures has been in regular practice.  Successful use of rhBMP-2 aided VBA appeared in maxillofacial literature recently. 
In the present case, the role of rhBMP-2 is probably to compensate for the loss of vertical bone height that usually accompanies the bone grafting in VBA. The osteogenic potential of rhBMP-2 was utilized for this purpose. The autologous bone graft provided the much needed osteogenic signals, rhBMP-2 caused chemotaxis, both leading to recruitment and aggregation of monocytes at the surgical site and later its differentiation into osteoblastic cells. Osteoblasts later differentiated into definitive osteoblastic cells, which progressively laid the matrix. The matrix later calcified. All these sequential, essential healing process was occurring in the presence of the dental implants. This ensured successful remodeling of the bone causing the much needed osseo-integration. The 3 months postoperative vertical height of the reconstructed site was normal. There was no clinical nor radiological evidence of reduction in loss of bone height during the abutment placement or during the 30 months follow-up.
Wide resection and stripping of periosteum  ensured the complete removal of the lesion, as there have been instances of recurrence even three decades later in a reconstructed mandible. The technique, mentioned herein will join one of the few cases in literature of immediate reconstruction of critical sized defect of mandible, especially with VBA immediately after a benign tumor resection. Though such off-label use has been sporadically reported in literature, in clinical practice, they provide an excellent result. However, reservations for its regular practice exist.  Further large scale studies are needed to establish its potential for regular inception in clinical practice.
The effectiveness of rhBMP-2 with autogenous bone grafts have been previously established ,,,,,, even in pathological conditions. , The uniqueness of this technique is the primary and secondary stability that is much required for dental implants, especially during the bone remodeling period. The proposed technique offers the much needed stability and support during the early stages as well as during the late remodeling phase. The advantage is that the height of the ridge is not lost due to resorption.
| References|| |
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S M Balaji
Director and Consultant, Balaji Dental and Craniofacial Hospital, Teynampet, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]