Synthesis of ß-tricalcium phosphate by modifying the heating process of a dental casting mold.

This study investigated a novel method for artificial synthesis of ß-tricalcium phosphate (ß-TCP). The binder of the phosphate-bonded investment was replaced with calcium oxide instead of magnesium oxide and sintered in an electric furnace. The water/powder mixing ratio for hardening was determined using preliminary experiments. Thermal analysis was performed to check the thermal behavior of the sample tested. In addition, the fired sample was analyzed using an X-ray diffraction apparatus to identify the compounds after sintering. The hardened sample exhibited multiple compounds, including unreacted components, post which, new compounds were generated by heating. Peaks of calcium pyrophosphate and ß-TCP were confirmed at 800ºC and 1,300ºC, respectively. ß-TCP could be easily synthesized within the limited study by sintering at 1,300ºC both monoammonium phosphate and calcium oxide. Experimental results suggest that ß-TCP can be easily synthesized by simulating the conventional dental casting process.

Bone forming ability of recombinant human collagen peptide granules applied with ß-tricalcium phosphate fine particles.

Recombinant human collagen peptide, developed based on human collagen type I, contains an arginyl-glycyl-aspartic acid (RGD)-rich motif to enhance cell behavior and is anticipated as a xeno-free polymer material for use in tissue engineering. We fabricated granules containing recombinant human collagen peptide (RCP) applied with beta-tricalcium phosphate fine particles (RCP/ß-TCP) as bone filling scaffold material and assessed the bone forming ability of RCP/ß-TCP. Recombinant peptide was thermal crosslinked and freeze-dried to prepare RCP. An aqueous dispersion of ß-TCP fine particles was added to RCP to obtain RCP/ß-TCP. Subsequently, RCP/ß-TCP were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), and cell culture assessments. Furthermore, RCP/ß-TCP were implanted into rat cranial bone defects for radiographic and histological evaluations. In SEM and EDX analyses of RCP/ß-TCP, ß-TCP particles dose-dependently covered the surface of RCP. Cell culture tests showed that RCP/ß-TCP remarkably promoted proliferation and mRNA expression of various genes, such as integrin ß1 and osteogenic markers, of osteoblastic MC3T3-E1 cells. Histomorphometric assessment at 4 weeks showed that RCP/ß-TCP significantly promoted new skull bone formation compared to RCP (p < 0.05) and control (no application) (p < 0.01). Accordingly, these findings suggest RCP/ß-TCP possess bone forming capability and would be beneficial for bone tissue engineering therapy.

Xenogeneic bone filling materials modulate mesenchymal stem cell recruitment: role of the Complement C5a.

OBJECTIVES: When bone filling materials are applied onto the periodontal tissues in vivo, they interact with the injured periodontal ligament (PDL) tissue and modulate its activity. This may lead to mesenchymal stem cells (MSCs) recruitment from bone marrow and initiate bone regeneration. Our hypothesis is that the filling materials affect PDL cells and MSCs functional activities by modulating PDL C5a secretion and subsequent MSCs proliferation and recruitment. MATERIALS AND METHODS: Materials' extracts were prepared from 3 bone-grafting materials: Gen-Os® of equine and porcine origins and bovine Bio-Oss®. Expression and secretion of C5a protein by injured PDL cells were investigated by RT-PCR and ELISA. MSCs proliferation was analyzed by MTT assay. C5a binding to MSCs C5aR and its phosphorylation was studied by ELISA. C5a implication in MSCs recruitment toward injured PDL cells was investigated using Boyden chambers. RESULTS: MSCs proliferation significantly increased with Gen-Os® materials but significantly decreased with Bio-Oss®. C5a secretion slightly increased with Bio-Oss® while its level doubled with Gen-Os® materials. C5a fixation on MSCs C5aR and its phosphorylation significantly increased with Gen-Os® materials but not with Bio-Oss®. MSCs recruitment toward injured PDL cells increased with the three materials but was significantly higher with Gen-Os® materials than with Bio-Oss®. Adding C5a antagonist inhibited MSCs recruitment demonstrating a C5a-mediated migration. CONCLUSIONS: Injured PDL cells secrete C5a leading MSCs proliferation and recruitment to the PDL injured cells. Gen-Os® materials enhanced both C5a secretion by injured PDL cells and MSCs recruitment. Bio-Oss® inhibited MSCs and was less efficient than Gen-Os® materials in inducing MSCs recruitment. CLINICAL RELEVANCE: Within the limits of this study in vitro, Gen-Os® filling materials have a higher potential than Bio-Oss® on MSCs proliferation and C5a-dependent recruitment to the PDL injury site and the subsequent bone regeneration.

Pre-Registration Assessment of Bone-Filling Products.

The use of bone-filling material to repair bone defects and fix implanted bone grafts is a developing area in medicine. Investigators can evaluate bone-filling materials through use of several indices to make comparisons and to determine suitability for application in humans1 . However, it is quite difficult to transform their discovery into practical use, because the viability of the studied material might require examination of all aspects of properties. In addition, for a material to become a product, a complete procedure involving a declaration, registration, and approval is necessary. This article introduces the technical indices that the investigators and reporters should provide in their declaration and registration data to meet the relevant standards in China. The indices include physical and chemical properties, biocompatibility, biosecurity, pre-clinical animal model tests, sterilization and disinfection, product duration, and packaging. Full consideration of all possible indices is crucial to realize the transformation from a designed product to a commercial medical device, which requires effective interaction between clinicians and engineers.

Magnesium phosphate based cement with improved setting, strength and cytocompatibility properties by adding Ca(H2PO4)2·H2O and citric acid.

Inorganic phosphate cements have become prevalent as bone filling materials in clinical applications, owing to beneficial properties such as self-setting, biodegradability and osteoconductivity. However, the further development of phosphate cements with higher strength and improved cytocompatibility is expected. In this paper, we reported the preparation of a novel magnesium phosphate based cement (MPBC), which has similar compositions with magnesium phosphate cement (MPC) but Ca(H2PO4)2·H2O and citric acid were additionally added to modulate the performance. The physicochemical and biological properties of MPBC were investigated, the influences of the added Ca(H2PO4)2·H2O and citric acid on the performances of MPBC were analyzed, and the differences of performance between MPBC and MPC were discussed. Experimental results show that the setting time and compressive strength of MPBC were effectively enhanced by the addition of citric acid. In vitro biological degradation indicates that about 15 wt% of MPBC was reduced in 4 weeks. Compared with MPC, MPBC has weaker alkalinity and less dissolution of phosphate, leading to better suitability for cell proliferation and adhesion. These results suggest that as a bone filling material, MPBC shows better performance than MPC in many key indicators and has promising application prospects.