Please activate JavaScript!
Please install Adobe Flash Player, click here for download
ePaper created 2017-03-17, 11:08:54 | version 1.38.0
B i o m a t e r i a l s f o r o n l a y b o n e g r a f t s Introduction After tooth extraction, bone remodeling that leads to bone resorption is a common phenom- enon. Ridge resorption has made grafting pro- cedures popular in implant and restorative ther- apy.1–4 These procedures aim at restoring width and height for proper 3-D implant placement. Numerous treatment alternatives have been proposed (e.g., distraction osteogenesis and guided bone regeneration with particulated bone materials).5 Nonetheless, for extensive or severely atrophic ridges, block grafting has been advocated to be the most predictable ap- proach.6, 7 Autogenous bone has been regarded as the gold standard for bone reconstruction.8 This can be harvested from diferent locations based upon the extension of the atrophic area.8 While intraoral bone block grafts (mandibular ramus or mental symphysis) can be harvested with a less traumatic approach, the amount is often limited. However, extraoral bone block grafts (calvaria or iliac crest) fulfill the requirements in terms of quantity, but they increase the cost and lead to some sequelae for the donor site. Regardless of the harvesting location, autoge- nous block grafts might be further classified depending on their origin. For example, intra- membranous grafts (mandibular ramus and calvaria bone) have less bone resorption and the process of bone remodeling or “creeping sub- stitution” takes longer9 compared with endo- chondral bone (iliac crest).10 Hence, it is import- ant to take this into consideration when planning implant treatment so that it will not cause ex- tensive bone remodeling that threatens the final adequate prosthetically driven implant posi- tion.11, 12 Indeed, autologous bone has osteogenic ca- pacity;8 in other words, bone can potentially grow in between the interface of the graft and the host bone. Nevertheless, as already men- tioned, the drawbacks associated with this ap- proach have encouraged clinicians to use alter- natives, such as allogeneic or xenogeneic bone blocks.13, 14 These treatment modalities not only reduce the possibility of experiencing morbidi- ty, but also shorten the treatment and, hence, increase patient acceptance and satisfaction. The mechanism of forming new mineralized tissue is mediated by the mesenchymal cells, which diferentiate into osteoblasts that are coordinated by glycoproteins (bone morphoge- netic proteins).15 Hence, after an inflammatory process that ends in gradual substitution, the newly formed bone is obtained,16 or in this case hard tissue capable of obtaining first implant stability and subsequently osseointegration. In general, allogeneic and xenogeneic block grafts do not contain osteoprogenitor cells and, consequently, integration with the native bone might be arduous. Promising results have been shown in the literature with application of these block grafts for bone regeneration.17, 18 Depend- ing on their origin, they can be either from human (cadaver), known also as allografts, or from animal origin (equine and bovine), which are also called xenografts. Once harvested, the grafts must be preserved, and each manufac- turing company has developed its own process that can potentially determine the properties of the respective biomaterial. The objective of this article was to review the biological and physical properties of block grafting biomaterials available for bone regen- eration in atrophic maxillary ridges. Further- more, the aim was to present the human and animal clinical and histological findings of bio- materials used for maxillary reconstructions. Materials and methods I n f o r m a t i o n s o u r c e s An electronic literature search was conducted by two independent reviewers (AM and HLW) of several databases, including MEDLINE, EM- BASE, Cochrane Central Register of Controlled Trials and Cochrane Oral Health Group Trials Register databases, for articles written in English up to June 2016. S c r e e n i n g p r o c e s s Combinations of controlled terms (MeSH and EMTREE) and keywords were used whenever possible: (((((((Alveolar bone atrophy[MeSH Terms]) OR alveolar bone loss[MeSH Terms]) AND bone grafting[MeSH Terms]) OR allograft[MeSH Terms]) OR xenograft[MeSH Terms]) OR biomaterials[MeSH Terms]) AND block) OR onlay OR Journal of Oral Science & Rehabilitation Volume 3 | Issue 1/2017 19