Short-term effects of mineral particle sizes on cellular degradation activity after implantation of injectable calcium phosphate biomaterials and theconsequences for bone substitution

This in vivo study investigated the influence of two calcium phosphate part icle sizes (40-80 mu m and 200-500 mu m) on the cellular degradation activi ty associated with the bone substitution process of two injectable bone sub stitutes (IBS), The tested biomaterials were obtained by associating a biph asic calcium phosphate (BCP) ceramic mineral phase and a 3% aqueous solutio n of a cellulosic polymer (hydroxypropylmethylcellulose). Both were injecte d into osseous defects at the distal end of rabbit femurs for 2- and 3-week periods. Quantitative results for tartrate-resistant acid phosphatase (TRA P) cellular activity, new bone formation, and ceramic resorption were studi ed for statistical purposes. Positive TRAP-stained degradation cells were s ignificantly more numerous for IBS 40-80 than IBS 200-500, regardless of im plantation time. BCP degradation was quite marked during the first 2 weeks for IBS 40-80, and bone colonization occurred more extensively for IBS 40-8 0 than for IBS 200-500, The resorption-bone substitution process occurred e arlier and faster for IBS 40-80 than IBS 200-500, Both tested IBS displayed similar biological efficiency, with conserved in vivo bioactivity and bone -filling ability. Differences in calcium phosphate particle sizes influence d cellular degradation activity and ceramic resorption but were compatible with efficient bone substitution, (Bone 25:71S-74S; 1999) (C) 1999 by Elsev ier Science Inc, All rights reserved.