implants - international magazine of oral implantology International Edition

_Introduction The aim of the present study was to compare the clinical outcome and radiographic bone changes in augmentedridgesutilizingasyntheticNanoBoneblock versusanallograftboneblock,andtoinvestigatehisto- logicallythesuccessofasyntheticNanoBoneblockver- sus an allograft bone block for ridge augmentation. In thepreviousissuesofimplants:internationalmagazine oforalimplantology,theauthorsgaveadetailedintro- duction to their topic and explained the materials and methods used in their study (implants 1/2013) and the results of clinical outcomes & radiographic bone changes (implants 2/2013). In this issue, their report is completedbythehistologicalresultsoftheirinvestiga- tionsandanextensivediscussion. _Bone regeneration process Phase1:Boneregeneration1 Withinthegraft,whetherforamandibularcontinu- ity defect, a sinus augmentation surgery or dental im- plantisplacedinadeadspacefilledwithclottedblood. The platelets entrapped in the clot degranulate within hours of graft placement, releasing PDGF, TGF-b1 and TGF-b2.Bothofthesefactorebegaintheboneregener- ativeprocess.PDGFbindstoendothelialcellstoinitiate the ingrowth of capillaries, while TGF-b1 and TGF-b2 bind to the endosteal osteoblasts and marrow mes- enchymalstemcellstoinitiatemitosistoincreasetheir numbers as well as stimulate their production of os- teoid.Thiscontinuesduringthefirst3daysofthegraft, atwhichtimecapillariesarealreadyseentobeentrap- pingthegraft.However,bythistime,theplateletshave degranulated and are no longer a primary source of growth factors to drive the bone regenerative process. At these times, macrophages take over this role. Macrophageswereinitiallyattractedtothegraftascir- culatingmonocytesoffreetissuecellsbyinherentoxy- gen gradient in the graft. Thus, the inherent properties of the wound, particularly the oxygen gradient, PDGF andTGF-b,initiateearlyangiogenesisfromsurrounding capillaries and mitogenesis of the transferred osteo- componentcells.Thecompleterevascularizationofthe graft is seen by day 14. By this time, the endosteal os- teoblasthavealreadylaiddownosteoidontheoriginal bone trabeculae and the marrow stem cells have dra- matically increased in number and have begun differ- entiatingintoosteoblasts.Thestemcellpopulationand endostealosteoblastsproducesmallamountofosteoid. Duringthefirst3to4weeks,thebiochemicalandcel- lular phase of bone regeneration proceeds to clinically consolidate the graft by coalescing individual osteoid islands, surface osteoid on cancellous trabeculae and host bone. This process is essentially transplanted os- teogenessis. However, it uses the fibrin network of the grafts as a framework. This is referred to as osteocon- duction,whichprovidesascaffoldforwhathasbeencall (creepingsubstitution).Thatis,thenormallynonmotile I research Figs. 1a & b_X100, H&E stained section showing ostoid bone formation. Ridge augmentation for an atrophied posterior mandible—Part III NanoBone block versus allograft bone block Authors_Dr Omar Soliman, Prof. Dr Dr Mohamed Nassar, Ass. Prof. Dr Mahmoud Shakal & Ass. Prof. Dr Eman Mohy El-din Megahed, Egypt 22 I implants4_2013 Fig. 1bFig. 1a