Evaluation of Healing Following Tooth Extraction With Ridge Preservation Using Cortical Versus Cancellous Freeze-Dried Bone Allograft

• Localización: Journal of periodontology, ISSN 0022-3492, Nº. 4, 2014, págs. 514-524
• Idioma: inglés
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• Resumen

  • Background: The objective of this study is to compare histologic and clinical healing following tooth extraction and ridge preservation with either cortical or cancellous freeze-dried bone allograft (FDBA) in non-molar extraction sockets.

    Methods: Forty patients requiring implant placement were enrolled, with 20 patients randomly assigned to each group (cortical versus cancellous FDBA). All of the allograft materials were obtained from the same donor to control for variability between donors and processing. Patients returned after 17 to 21 weeks (average: 18.2 weeks), and a 2-mm-diameter core biopsy was obtained before implant placement. Histomorphometric analysis was performed to determine percentage of new bone formation, residual graft material, and non-mineralized connective tissue (CT)/other material. Clinical measurements of ridge dimensions were taken at the time of tooth extraction and again at implant placement.

    Results: There was no significant difference in new bone formation between the cortical and cancellous FDBA groups (P = 0.857). A significantly greater percentage of residual graft material was detected in the cortical FDBA group compared with the cancellous FDBA group (P = 0.019). A significantly greater percentage of non-mineralized CT/other material was found in the cancellous FDBA group compared with the cortical FDBA group (P = 0.040). The only significant clinical difference between groups was a greater loss of lingual ridge height in the cancellous group.

    Conclusions: This is the first reported study to compare the histologic changes following tooth extraction with ridge preservation in humans using cortical versus cancellous FDBA. There were no differences in the percentage of new bone formation between the groups.

    Ridge preservation is commonly performed following tooth extraction in preparation for dental implant placement. Many different biomaterials are used to reduce the dimensional changes following tooth extraction including autogenous, allogenic, xenograft, and alloplast sources. Due to the success in space maintenance, rapid bone turnover, biocompatibility, and the lack of need to harvest from another site, allograft materials have become increasingly popular.1 Freeze-dried bone allograft (FDBA) is commonly used today and has shown success, both clinically and histologically, as a ridge preservation material.2-4 FDBA serves as an osteoconductive scaffold, allowing the migration of mesenchymal cells from the recipient site to extend into the allograft to form new bone.5,6 Over time, the scaffold is replaced with new bone.7,8 Although both cortical and cancellous FDBA are osteoconductive, their healing patterns are dissimilar. Cancellous allografts have been shown to heal via creeping substitution.5,6,9,10 This process involves early invasion of the allograft matrix with host mesenchymal cells, vascularization, and differentiation to osteoblasts. Therefore, new bone forms initially, followed by osteoclastic bone resorption. In contrast, cortical allografts have been shown to heal via reverse creeping substitution. This involves early differentiation and recruitment of osteoclasts, whereby bone resorption precedes bone formation.6,9,11-13 Cortical FDBA contains residual bone morphogenetic proteins (BMPs) in its matrix.14 Subsequent to osteoclastic resorption, these growth factors are released from the mineralized matrix and induce new bone formation.15-18 In the orthopedic literature, cancellous allografts have been shown to completely resorb, whereas cortical allografts have been shown to remain present for several years.5,6,13,19 Cortical allografts also act as effective filler materials to prevent compression of the grafted space6 and may be more resistant to compressive forces than cancellous allograft owing to their increased mineral content and reduced porosity.9,20 However, some studies have shown that cancellous allograft forms new bone more rapidly than cortical allograft. Seebach et al.8 showed that a cancellous allograft provided the best scaffold for new bone formation, as its macroporosity, microporosity, and collagen fiber structure promoted the earliest seeding of host mesenchymal stem cells to its matrix compared with other bone graft substitutes. Cancellous allograft heals by the formation of an internal callus, a process that is more rapid than that of cortical allograft, which heals by forming an external callus.9 Others have added that the increased surface area and trabecular structure of cancellous bone allows for earlier and more rapid vascularization.9,21 This concept is supported by studies that have shown that the degree of porosity and interconnectivity of the pores significantly affects vascularization and new bone formation.7,8,22,23 Thus, cancellous FDBA may offer the potential advantage of increased porosity compared with cortical FDBA.

    Some claim that there is no difference in the potential for new bone formation between cancellous and cortical FDBA. In standard bone defects in baboons, there was no difference in new bone formation between the materials.24 The authors claimed that a microparticle size of 90 to 300 µm made the cortical and cancellous bone indistinguishable.24,25 A standard particle size of 250 to 1,000 µm was chosen for the current study. This is a particle size commonly used for oral applications and is widely available on the market. Currently, there are no published studies that have compared cortical and cancellous FDBA for use in ridge preservation following tooth extraction. Therefore, clinicians make decisions as to which material to choose based on animal model research or studies of bone grafting for orthopedic applications. The primary aim of the current study is to histologically evaluate new bone formation following ridge preservation with cortical FDBA compared with cancellous FDBA. The secondary aim is to determine whether there were any differences in alveolar ridge height or width after ridge preservation with the two different materials.