Effect of rapidly resorbable bone substitute materials on the temporal expression of the osteoblastic phenotype in vitro

Abstract

Ideally, bioactive ceramics for use in alveolar ridge augmentation should possess the ability to activate bone formation and, thus, cause the differentiation of osteoprogenitor cells into osteoblasts at their surfaces. Therefore, in order to evaluate the osteogenic potential of novel bone substitute materials, it is important to examine their effect on osteoblastic differentiation. This study examines the effect of rapidly resorbable calcium-alkali-orthophosphates on osteoblastic phenotype expression and compares this behavior to that of beta-tricalcium phosphate (TCP) and bioactive glass 45S5. Test materials were three materials (denominated GB14, GB9, GB9/25) with a crystalline phase Ca(2)KNa(PO(4))(2) and with a small amorphous portion containing either magnesium potassium phosphate (GB14) or silica phosphate (GB9 and GB9/25, which also contains Ca(2)P(2)O(7)); and a material with a novel crystalline phase Ca(10)[K/Na](PO(4))(7) (material denominated 352i). SaOS-2 human bone cells were grown on the substrata for 3, 7, 14, and 21 days, counted, and probed for an array of osteogenic markers. GB9 had the greatest stimulatory effect on osteoblastic proliferation and differentiation, suggesting that this material possesses the highest potency to enhance osteogenesis. GB14 and 352i supported osteoblast differentiation to the same or a higher degree than TCP, whereas, similar to bioactive glass 45S5, GB9/25 displayed a greater stimulatory effect on osteoblastic phenotype expression, indicating that GB9/25 is also an excellent material for promoting osteogenesis.

Bioactivity: Mechanisms

“…These studies showed that several calcium-alkali orthophosphates supported osteoblast differentiation to a greater extent than TCP. 40,87,88 Recently, it was demonstrated that the glassy-crystaline calcium-alkali orthophosphate material GB9, which contains the crystalline phase Ca 2 KNa(PO 4 ) 2 and a small amorphous portion containing silica phosphate, had a significantly greater stimulatory effect on osteoblastic proliferation and differentiation compared to b-TCP, 42,87 preconditioned BG45S5, 42 and other calcium-alkali orthophosphate materials of varying composition 42,87 (see Chapter 6.620, Dental Graft Materials for more details).…”

“…4,21,22,24,27,33,34,54 Bioactive calcium phosphate ceramics stimulate bone formation. 4,24,27,32,42,43,54,86 This requires the ability to differentiate osteoprogenitor cells into osteoblasts at their surfaces. Thus, in order to evaluate the stimulatory potential of bioactive ceramics on osteogenesis, it is logical to examine the effect of these materials on osteoblastic differentiation.…”

“…Consequently, over the last 15 years, various assays have been developed and used, which permit studying the effect of bioceramics on the expression of osteogenic markers in vitro. 40,42,52,70,76,[87][88][89] Osteoblast differentiation is defined by three principal biological periods: cellular proliferation, cellular maturation, and matrix mineralization. [90][91][92] Differentiating osteoblasts are known to synthesize type I collagen, alkaline phosphatase (ALP), and other noncollagenous extracellular bone matrix proteins such as osteonectin, osteocalcin, osteopontin, and bone sialoprotein.…”

“…[37][38][39][40][41][42][43][44][45][46][47] These are glassy crystalline calcium-alkali orthophosphates that exhibit stable crystalline Ca 2 KNa(PO 4 ) 2 phases. 37,38,47,48 These materials have a higher solubility than TCP and therefore they are designed to exhibit a higher degree of biodegradability than TCP.…”

“…37,38,47 On this basis, they are considered as excellent candidate materials for alveolar ridge augmentation. [39][40][41][42][43][44][45][46] Furthermore, various calcium phosphate materials with addition of silicon have been developed with the intent to enhance their bioactivity and mechanical stability. [49][50][51] As outlined above, bioactive calcium phosphate ceramics and glasses are known to stimulate bone tissue formation at their surfaces.…”