Tetracalcium Phosphate/Monetite/Calcium Sulfate Hemihdrate Biocement Powder Mixtures Prepared by the One-Step Synthesis for Preparation of Nanocrystalline Hydroxyapatite Biocement-Properties and In Vitro Evaluation

A modified one-step process was used to prepare tetracalcium phosphate/monetite/calcium sulfate hemihydrate powder cement mixtures (CAS). The procedure allowed the formation of monetite and calcium sulfate hemihydrate (CSH) in the form of nanoparticles. It was hypothesized that the presence of nanoCSH in small amounts enhances the in vitro bioactivity of CAS cement in relation to osteogenic gene markers in mesenchymal stem cells (MSCs). The CAS powder mixtures with 15 and 5 wt.% CSH were prepared by milling powder tetracalcium phosphate in an ethanolic solution of both orthophosphoric and sulfuric acids. The CAS cements had short setting times (around 5 min). The fast setting of the cement samples after the addition of the liquid component (water solution of NaH2PO4) was due to the partial formation of calcium sulfate dihydrate and hydroxyapatite before soaking in SBF with a small change in the original phase composition in cement powder samples after milling. Nanocrystalline hydroxyapatite biocement was produced by soaking of cement samples after setting in simulated body fluid (SBF). The fast release of calcium ions from CAS5 cement, as well as a small rise in the pH of SBF during soaking, were demonstrated. After soaking in SBF for 7 days, the final product of the cement transformation was nanocrystalline hydroxyapatite. The compressive strength of the cement samples (up to 30 MPa) after soaking in simulated body fluid (SBF) was comparable to that of bone. Real time polymerase chain reaction (RT-PCR) analysis revealed statistically significant higher gene expressions of alkaline phosphatase (ALP), osteonectin (ON) and osteopontin (OP) in cells cultured for 14 days in CAS5 extract compared to CSH-free cement. The addition of a small amount of nanoCSH (5 wt.%) to the tetracalcium phosphate (TTCP)/monetite cement mixture significantly promoted the over expression of osteogenic markers in MSCs. The prepared CAS powder mixture with its enhanced bioactivity can be used for bone defect treatment and has good potential for bone healing.

Tetracalcium Phosphate Treatment on Experimental Fracture Model in Rats

Background: Studies have shown that bioactive cements have beneficial bone-forming effects. Our objective in the present study is to investigate the efficacy of tetracalcium phosphate (TTCP) on fracture healing in rat femur.Materials and methods: Forty-two female Wistar Albino rats randomized into two groups (groups 1 and 2, n=21 for each). The left femur of all animals was fractured by osteotomy after deep anesthesia with ketamine. Additional procedure was not applied to the rats in group 1. Rats in Group 2, following osteotomy were applied to the fracture line approximately 2 cc TTCP. The animals were sacrificed on the 1st, 2nd and 3rd post-operative weeks (each week 7 animals were sacrificed from each group) and the broken femur were removed. The femur were examined first radiographically and second, histopathologically.Results: Radiologically, callus maturity and bone union increased with time in both groups. But no significant differences were found regarding callus maturity and bone union in weekly comparisons (Anteroposterior plain: p:0.53, p:0.37, p:0.42, Lateral plain p:0.26, p:0.42, p:0.87). Histopathologically, the fractures healed normally as the weeks progressed in both groups. In the comparison of both groups, no significant difference was found outside the 1st week, although the histological scores of group 2, who were treated for all weeks, were higher in terms of fracture healing (p:0,024, p:104,p:462).Conclusions: Although no significant difference was found in the comparison of both groups except for the first week, the histological scores of the group 2 who received TTCP in all weeks were higher in terms of fracture healing. According to the results of this study, we think that TTCP can be useful especially in the early stages of fracture healing.

Calcium Phosphate Cement Modified with Silicon Nitride/Tricalcium Phosphate Microgranules

Tetracalcium phosphate/monetite biocement was modified with 10 and 30 wt. % addition of highly porous silicon nitride/α-tricalcium phosphate (αTCP) microgranules with various content of αTCP. A composite cement powder mixture was prepared using mechanical homogenization of basic components. The accelerated release of dexamethasone from composite cement was revealed, which indicates their possible utilization for controlled drug release. The wet compressive strength of cements (<17 MPa) was significantly reduced (more than 30%) in comparison with the unmodified cement and both compressive strength and setting time were influenced by the content of αTCP in microgranules. The addition of microgranules caused a 20% decrease in final cement density. Microgranules with a higher fraction of αTCP showed good in vitro SBF bioactivity with precipitation of hydroxyapatite particles. Microstructure analysis of fractured cements demonstrated excellent interconnection between microgranules and cement calcium phosphate matrix, but also showed lower mechanical strength of microgranule cores.

Bioactive Tetracalcium Phosphate Scaffolds Fabricated by Selective Laser Sintering for Bone Regeneration Applications

Tetracalcium phosphate (TTCP), a potential biological scaffold material, has attracted increasing interest for bone regeneration applications due to its good biodegradability and biocompatibility. In this research, three-dimensional porous TTCP scaffolds were manufactured via selective laser sintering (SLS), and an in-depth and meticulous study on the influence of laser power on the microstructure and mechanical properties of TTCP scaffolds was performed. The results showed that the TTCP particles fused together and formed a solid object due to the decrease in the number of micro-pores in the scaffold as the laser power increased from 6 W to 9 W. The maximum compressive strength that the scaffold could withstand and the strength of the fracture toughness were 11.87 ± 0.64 MPa and 1.12 ± 0.1 MPa·m1/2, respectively. When the laser power increased from 9 W to 10 W, the TTCP grains grew abnormally, resulting in diminished mechanical properties. The bioactivity tests showed that the surfaces of the scaffolds were entirely covered by bone-like apatite layers after soaking in simulated body fluid (SBF) for three days, indicating that the scaffolds exhibit excellent bioactivity. Moreover, cell experiments showed that the TTCP scaffolds had good biocompatibility. This study indicated that SLS-fabricated TTCP scaffolds may be a promising candidate for bone regeneration applications.