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Journal of Oral Science & Rehabilitation Issue 01/2015

46 Volume 1 | Issue 1/2015 Journal of Oral Science & Rehabilitation larsystem ofABB particles and ontheirsurface close to osteoclast-like cells (Fig. 2). At six months, OPN expression was princi- pally observed at the interstitial boundary of bone with ABB particles and within lacunae andbonecanaliculi,formingastarshape(Fig.2), with no expression in the trabecular bone or in- terstitium. Cortical OPN expression was di- rectly correlated with the number of osteo- cytes per mm2 (rho coefficient  =  0.405, p = 0.045, Spearman test), with OPN expres- sion in cement lines (rho coefficient = 0.757, p < 0.001, Spearman test) and with OPN ex- pressioninosteocytes(rhocoefficient = 0.432, p = 0.012, Spearman test). A direct correlation was found between OPN expression in ABB particles and in mono- cytes and macrophages (CD68-positive cells; rho coefficient = 0.583, p = 0.009, Spearman test). OPN expression in osteocytes was in- versely correlated with the number of os- teoblasts (CD56-positive cells) per mm2 (rho coefficient  =  -0.828, p =  0.042, Spearman test). Avascularbedwasformedinthenonminer- alized tissue by vessels of different calibers in the graft area and by capillary vessels among the adipocytes in the bone marrow area, with a mean in the biopsies of 86.28 ± 56.6 CD34- positive vessels per mm2 . OPN expression in osteocytes was directly correlated with the number of vessels per mm2 (rho coeffi- cient = 0.828, p = 0.042, Spearman test). TRAP expression was directly correlated with the count per mm2 of osteoclasts (rho co- efficient = 0.532, p = 0.015, Spearman test), monocytes and macrophages (rho coeffi- cient = 0.622, p = 0.008, Spearman test), and osteoblasts (rho coefficient = 0.391, p = 0.048, Spearman test). TRAP expression was corre- lated with the local and diffuse expression of OPN(rhocoefficient = 0.439,p= 0.022,Spear- man test; Fig. 3). Discussion In this study of bone xenografts in a clinical series of maxillary sinus lift, immunohisto- chemical OPN expression was detected not only in osteocytes and on ABB particles, but also within the lacuno-canalicular system of ABB particles and close to osteoclast-like cells on their surface. Bone formation or resorption requires ad- hesion molecules (arginine–glycine–asparagine sequences), such as fibronectin, fibrinogen, vit- ronectin,TypeIcollagen,OPNorbonesialopro- tein, to attach osteoblasts or osteoclasts to surfaces for remodeling.43 Because ABB parti- cles are free of proteins,44 protein expression on the particles must derive from proteins ab- sorbed from the environment. The above chemotactic factors may have stimulated and directed the migration of cells to the foreign material.13 Microchannel pores (< 10 μm) of ABB may be relevant for osteogenic cell attachment, mi- gration, proliferation and differentiation.45 At the same time, the inner surface of ABB parti- cles becomes considerably enlarged, favoring the formation of newvessels and therefore the inward growth of new bone within the parti- cles.31 A greater microporosity also expands Os teopon tin expres s io n i n ano rgani c bovi ne bo ne Fig. 2 Fig. 2 Immunohistochemical expression of OPN. (a) OPN location on boundary of ABB particles with trabecular bone (micropolymer-peroxidase- based method, 20×). (b) Detail of OPN deposits in lacuno-canalicular network and location on boundary of ABB particles near to osteoclast (micropolymer- peroxidase-based method, 60×). a b

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