No abstract

Calcium phosphate cements can be handled in paste form and set in a wet medium after precipitation of calcium phosphate crystals in the implantation site. Depending on the products entering into the chemical reaction leading to the precipitation of calcium phosphates, different phases can be obtained with different mechanical properties, setting times and injectability. We tested a cement composed of a powder, containing beta-tricalcium phosphate (beta-TCP) and sodium pyrophosphate mixed with a solution of phosphoric and sulphuric acids. The cement set under a dicalcium phosphate dihydrate (DCPD)-based matrix containing beta-TCP particles. This was injected with a syringe into a defect drilled in rabbit condyles, the control being an identical defect left empty in the opposite condyle. The condyles were analysed histologically 2, 6 and 18 weeks after implantation. After injection into the bone defect the cement set and formed a porous calcium phosphate structure. Two different calcium phosphate phases with different solubility rates could be identified by scanning electron microscopy (SEM) observation. The less-soluble fragments could be degraded by cell phagocytosis in cell compartments of low pH or integrated in the newly formed bone matrix. The degradation rate of the material was relatively high but compatible with the ingrowth of bone trabeculae within the resorbing material. The ossification process was different from the creeping substitution occurring at the ceramic contact. Bone did not form directly at the cement surface following the differentiation of osteoblasts at the material surface. The trabeculae came to the material surface from the edges of the implantation site. Bone formation in the implantation site was significantly higher than in the control region during the first week of implantation. In conclusion, this material set in situ was well tolerated, inducing a mild foreign-body reaction, which did not impair its replacement by newly formed bone within a few weeks.

Purpose: Active immunotherapy is a promising antitumoral strategy; however its use in combination with chemotherapy in dogs with large B-cell lymphoma (DLBCL) remains largely untested. Heat shock proteins (HSP) bind the small peptides they chaperone (HSPPC), allowing for immunization of the host against a large repertoire of tumor-associated antigens. Hydroxylapatite vehicles HSPPCs and acts as an immunologic adjuvant. The aim of this study was to show that an autologous vaccine with hydroxylapatite and tumor-derived HSPPCs is safe and therapeutically effective in dogs with DLBCL.Experimental Design: Nineteen dogs with naturally occurring DLBCL were entered into a prospective randomized placebo-controlled double-blinded trial of HSPPCs-hydroxylapatite plus chemotherapy versus chemotherapy alone. Endpoints included time to progression (TTP), lymphoma-specific survival (LSS), and incidence of toxicoses.Results: Median first TTP after randomization to the vaccine arm was 304 days versus 41 days for the control arm (P ¼ 0.0004). There was also a statistically significant difference in duration of second remission between the two groups (P ¼ 0.02). Median LSS was 505 days for the vaccinated dogs versus 159 days for the unvaccinated dogs (P ¼ 0.0018). Six vaccinated dogs achieved molecular remission, as shown by clonal immunoglobulin H (IgH) rearrangement. Toxicoses were comparable between the two treatment arms.Conclusions: The results of this trial demonstrate that the autologous vaccine tested here is safe and efficacious in prolonging TTP and LSS in dogs with DLBCL when used in combination with dose-intense chemotherapy. On the basis of these results, additional evaluation of this novel therapeutic strategy is warranted in human DLBCL. Clin Cancer Res; 20(3); 668-77. Ó2013 AACR.

Calcium phosphate coatings on dental implants enhance integration of the material. Resorption of the ceramic coatings has raised some concern about the behavior of the bone-implant interfaces after the coating disappearance. Substitution of the OH- ions by fluoride in the hydroxylapatite (HA) lattice makes the calcium phosphate more stable. We investigated the degradation rate of dental implants with 50- and 100-microm coatings of HA, fluorapatite (FA), or fluorhydroxylapatite (FHA). The implants were inserted in dog jaws and retrieved for histological analysis after 3, 6, and 12 months. The thickness of the calcium phosphate coatings was evaluated using an image analysis device. A relative resorption index and its standard deviation were studied. HA and FA coatings (even at 100-microm thickness) were almost totally degraded within the implantation period. In contrast, the FHA coatings did not show significant degradation during the same period. The standard deviation showed that the resorption process for FHA with thicknesses of 50 or 100 microm was the same. Such a difference was not observed between the 50- and 100-microm thick coatings of FA and HA. In conclusion, the FHA coatings showed good integration in the bone tissue and lasted much longer than classic calcium phosphate coatings.