A novel strategy for calcium magnesium phosphate/carboxymethyl chitosan composite bone cements with enhanced physicochemical properties, excellent cytocompatibility and osteogenic differentiation.

Artificial bone substitutes for bone repair and reconstruction still face enormous challenges. Previous studies have shown that calcium magnesium phosphate cements (CMPCs) possess an excellent bioactive surface, but its clinical application is restricted due to short setting time. This study aimed to develop new CMPC/carboxymethyl chitosan (CMCS) comg of mixed powders of active MgO, calcined MgO and calcium dihydrogen phosphate monohydrate. With this novel strategy, it can adjust the setting time and improve the compressive strength. The results confirmed that CMPC/CMCS composite bone cements were successfully developed with a controllable setting time (18-70 min) and high compressive strength (87 MPa). In addition, the composite bone cements could gradually degrade in PBS with weight loss up to 32% at 28 d. They also promoted the proliferation of pre-osteoblasts, and induced osteogenic differentiation. The findings indicate that CMPC/CMCS composite bone cements hold great promise as a new type of bone repair material in further and in-depth studies.

In Vivo Investigation of 3D-Printed Calcium Magnesium Phosphate Wedges in Partial Load Defects.

Bone substitutes are ideally biocompatible, osteoconductive, degradable and defect-specific and provide mechanical stability. Magnesium phosphate cements (MPCs) offer high initial stability and faster degradation compared to the well-researched calcium phosphate cements (CPCs). Calcium magnesium phosphate cements (CMPCs) should combine the properties of both and have so far shown promising results. The present study aimed to investigate and compare the degradation and osseointegration behavior of 3D powder-printed wedges of CMPC and MPC in vivo. The wedges were post-treated with phosphoric acid (CMPC) and diammonium hydrogen phosphate (MPC) and implanted in a partially loaded defect model in the proximal rabbit tibia. The evaluation included clinical, in vivo µ-CT and X-ray examinations, histology, energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) for up to 30 weeks. SEM analysis revealed a zone of unreacted material in the MPC, indicating the need to optimize the manufacturing and post-treatment process. However, all materials showed excellent biocompatibility and mechanical stability. After 24 weeks, they were almost completely degraded. The slower degradation rate of the CMPC corresponded more favorably to the bone growth rate compared to the MPC. Due to the promising results of the CMPC in this study, it should be further investigated, for example in defect models with higher load.

Development of cell-laden photopolymerized constructs with bioactive amorphous calcium magnesium phosphate for bone tissue regeneration via 3D bioprinting.

The synthesis of ideal bioceramics to guide the fate of cells and subsequent bone regeneration within the chemical, biological, and physical microenvironment is a challenging long-term task. This study developed amorphous calcium magnesium phosphate (ACMP) bioceramics via a simple co-precipitation method. The role of Mg2+ in the formation of ACMP is investigated using physicochemical and biological characterization at different Ca/Mg molar ratio of the initial reaction solution. Additionally, ACMP bioceramics show superior cytocompatibility and improved osteogenic differentiation of co-cultured MC3T3-E1 cells. Regulation of the microenvironment with Mg2+ can promote early-stage bone regeneration. For this, bioprinting technology is employed to prepare ACMP-modified 3D porous structures. Our hypothesis is that the incorporation of ACMP into methacrylated gelatin (GelMA) bioink can trigger the osteogenic differentiation of encapsulated preosteoblast and stimulate bone regeneration. The cell-laden ACMP composite structures display stable printability and superior cell viability and cell proliferation. Also, constructs loading the appropriate amount of ACMP bioceramic showed significant osteogenic differentiation activity compared to the pure GelMA. We demonstrate that the dissolved Mg2+ cation microenvironment in ACMP-modified composite constructs plays an effective biochemical role, and can regulate cell fate. Our results predict that GelMA/ACMP bioink has significant potential in patient-specific bone tissue regeneration.

Development of guar gum reinforced calcium magnesium phosphate-based bone biocement.

This study aims at developing a calcium magnesium phosphate-based bone biocement that combines a natural polymer and regenerative properties of bone bonding materials. The formulation of this biocement consists of oxidized guar gum, polydopamine, and calcium magnesium phosphate. The oxidized guar gum is easily soluble in water and has a slightly basic pH, unlike unmodified guar gum, thus allowing a homogenous paste to form in the alkaline environment of calcium magnesium phosphate. Three different oxidized degrees of guar gum were made, and the impact on the biocement properties was studied. The modified guar gum-reinforced biocement (OGG C2) displayed higher mechanical strength and lower degradation rates than OGG B1 and OGG A0. Furthermore, samples with polydopamine exhibited better results, thus, improving the already reinforced biocement. Morphological studies of the biocement displayed a highly porous structure with porosity varying among biocement containing different oxidized guar gum and polydopamine levels.

Multifunctional Scaffold for Osteoporotic Pathophysiological Microenvironment Improvement and Vascularized Bone Defect Regeneration.

Osteoporosis is a degenerative bone disease resulting from bone homeostasis imbalance regulated by osteoblasts and osteoclasts. Treating osteoporotic bone defects tends to be more difficult due to suppressed osteogenic differentiation, hyperactive osteoclastogenesis, and impaired angiogenesis. Hence, a drug carrier system composed of gelatin-coated hollow mesoporous silica nanoparticles (HMSNs/GM) loaded with pro-osteogenic parathyroid (PTH) and anti-osteoclastogenic alendronate (ALN) is constructed and compounded into calcium magnesium phosphate cement (MCPC). The spatial-temporal release of ions and drugs, controllable degradation rate, and abundant pore structure of MCPC composites enhance osteoporotic bone regeneration in ovariectomized rats by accelerating vascularization, promoting osteogenic differentiation and mineralization, and inhibiting osteoclastogenesis and bone resorption. The MCPC/HMSNs@ALN-PTH/GM demonstrates a synergistic threefold effect on osteogenesis, osteoclastogenesis, and angiogenesis. It improves the osteoporotic pathophysiological microenvironment and promotes osteoporotic vascularized bone defect regeneration, holding huge potential for other functional biomaterials design and clinical management.

Bone regeneration capacity of newly developed spherical magnesium phosphate cement granules.

OBJECTIVES: Magnesium phosphate-based cements begin to catch more attention as bone substitute materials and especially as alternatives for the more commonly used calcium phosphates. In bone substitutes for augmentation purposes, atraumatic materials with good biocompatibility and resorbability are favorable. In the current study, we describe the in vivo testing of novel bone augmentation materials in form of spherical granules based on a calcium-doped magnesium phosphate (CaMgP) cement. MATERIALS AND METHODS: Granules with diameters between 500 and 710 µm were fabricated via the emulsification of CaMgP cement pastes in a lipophilic liquid. As basic material, two different CaMgP formulations were used. The obtained granules were implanted into drill hole defects at the distal femoral condyle of 27 New Zealand white rabbits for 6 and 12 weeks. After explantation, the femora were examined via X-ray diffraction analysis, histological staining, radiological examination, and EDX measurement. RESULTS: Both granule types display excellent biocompatibility without any signs of inflammation and allow for proper bone healing without the interposition of connective tissue. CaMgP granules show a fast and continuous degradation and enable fully adequate bone regeneration. CONCLUSIONS: Due to their biocompatibility, their degradation behavior, and their completely spherical morphology, these CaMgP granules present a promising bone substitute material for bone augmentation procedures, especially in sensitive areas. CLINICAL RELEVANCE: The mostly insufficient local bone supply after tooth extractions complicates prosthetic dental restoration or makes it even impossible. Therefore, bone augmentation procedures are oftentimes inevitable. Spherical CaMgP granules may represent a valuable bone replacement material in many situations.

[Interaction and Mechanism Between Conditioning Agents and Two Elements in the Soil Enriched with Phosphorus and Cadmium].

Focusing on agricultural soil enriched in phosphorus and cadmium (total Cd=0.94 mg·kg-1 and total P=0.86g·kg-1), indoor cultivation experiments were conducted according to the length of the middle rice growth period and the following crop planting period in Hubei. The bioavailability of soil phosphorus and cadmium were examined along with their morphological changes and coupling effect under the influence of material biochar (BC), calcium magnesium phosphate fertilizer (CMP), and fly ash (FA). The results showed that:① When cultured for 140 days, the content of available phosphorus in the soil treated with the conditioning agents was significantly increased compared with the control soil, available phosphorus reached 22.47-37.81mg·kg-1, and the optimal growth requirements of rice were met without additional application of phosphate fertilizer, and adding BC had the best effect. ② The phosphorus in the test soil is mainly inorganic orthophosphate, and the content of different forms of inorganic phosphorus increased under the action of the conditioning agents. The fixed O-P and Ca10-P in the soil gradually changed to more active forms (Ca2-P, Ca8-P, Al-P and Fe-P) over time. ③ The effective Cd content of the soil treated with the conditioning agents was significantly reduced by 8.74%-17.48% relative to the control treatment, which was mainly related to the effect of the three conditioning agents on soil pH. At the same time, compared with the control, the addition of a conditioning agent significantly reduced the exchangeable Cd, and the carbonate-bound Cd and the residual Cd were increased. The abundance of active groups at the surface is related to the adsorption and chelation of Cd2+. The results showed that the three conditioners have the dual functions of phosphorus activation and cadmium passivation in phosphorus-and cadmium-enriched soil, and the effect of biomass carbon and calcium magnesium phosphate fertilizer was greatest, which persisted across the entire rice growth period to the sowing date of the next crop.

Cadmium uptake reduction in paddy rice with a combination of water management, soil application of calcium magnesium phosphate and foliar spraying of Si/Se.

A field experiment with 24 different treatments was carried out to study the effects of a combination of water management (WM), soil application of calcium magnesium phosphate (CMP), and foliar spraying of Si/Se on Cd uptake by paddy rice (Teyou 524). The water management modes included W1 (conventional water management) and W2 (flooding during the whole growth period). The application of CMP included P1 (1800 kg·hm-2) and P2 (3000 kg·hm-2). The leaf spraying regulations included LS (2.0 mmol·L-1 Na2SiO3), LX (25 µmol·L-1 Na2SeO3), and LSX (1.0 mmol·L-1 Na2SiO3 and 12.5 µmol·L-1 Na2SeO3). The results indicated that, compared to the control (W1), flooding and CMP reduced soil exchangeable Cd by 10.3, 21.5, 32.2, 27.6 and 36.9% under conditions of W2, P1, P2, W2P1 and W2P2, respectively; but the grain yield was reduced under W2 condition. Some individual treatments, including W2, P1, P2, LS, LX, and LSX, could reduce Cd concentration in the grain by 23.1-60.3%; but the combined regulations could reduce grain Cd concentrations up to 79.5%. Only the combined mode of CMP and leaf spraying of Si/Se could control grain Cd concentration below the Chinese National Food Safety Standard (0.2 mg·kg-1). Combined modes of fertilizer application (W2 and CMP) and foliar spraying (Si/Se), including W2P2LS, W2P2LX, W2P2LSX, were the most effective in reducing the Cd transport coefficients of both root-to-straw (RS) and straw-to-seed (SS). Considering Cd concentration in grain, treatments W2P2LS and W2P2LSX were the most effective ones, which could reduce Cd concentrations to 0.090 mg·kg-1 and 0.089 mg·kg-1 in grain, respectively. These results demonstrated that combined manipulation of the root zone (W2 and CMP) and foliar spraying (Si/Se) can effectively reduce grain Cd concentrations in rice.

[Effects of P fertilizer on female strobilus and needle N and P nutrition of Pinus massoniana clones with different fruiting abilities.] / ç£·è‚¥å¯¹ä¸åŒç»“å®žèƒ½åŠ›é©¬å°¾æ¾æ— æ€§ç³»é›ŒçƒèŠ±é‡åŠé’ˆå¶æ°®ç£·è¥å »çš„å½±å“.

In order to realize precise fertilization and high yield management of Pinus massoniana clonal seed orchard, clones with different fruiting abilities were used as the materials. Four P fertilization levels were at 0, 400, 800 and 1600 g per plant (P0, P4, P8 and P16 respectively). Fertilization was applied before floral primordia formation and after cone picked, respectively. The effects of P fertilizer on the female strobilus of P. massoniana clones and the changes of N, P contents in needles of different positions during floral primordia formation stage and early stage of flower bud differentiation were investigated. The results showed that compared with P0, the female strobilus of P8 and P16 were significantly increased by 67.4% and 61.2% in 2018 and 28.9% and 14.1% in 2019, respectively. There was a significant negative correlation between the female strobilus with the N content and N/P, a significant positive correlation between the female strobilus and the P content in needles. The responses of N and P contents in needles to P fertilization differed in clones with different fruiting abilities. In floral primordia formation stage, the N content of clones with weak fruiting ability was high, and the N/P was 11.5-12.5, while the P content of clones with strong fruiting abilities was high, and the N/P was 9.5-10.5. During this period, the P content of most clones under P8 treatment was the highest, while the N/P was lowest. In the early stage of flower bud differentiation, the N/P of two fruiting clones was 15.3-17.0 and 13.2-15.1, respectively. The P content in upside layer was significantly higher while N/P was significantly lower than that in middle and lower layers. In conclusion, the 800 g P fertilization per plant could increase the P content and reduce the N/P of needles during the floral primordia formation stage of clones with diffe-rent fruiting abilities, which was beneficial to the formation of female strobilus and promote the yield of clone seed orchards.

Mitigation of Cd accumulation in rice with water management and calcium-magnesium phosphate fertilizer in field environment.

Pollution of Cd has seriously threatened environmental safety and human health. The field experiment was conducted to investigate the effects of calcium-magnesium phosphate fertilizer and water management on bioavailability of Cd in soils and its accumulation in rice. The results revealed that continuous flooding has enhanced soil pH from 5.10 to 5.72 and reduced soil redox potential (Eh) from 164 to - 60 mV. Application of calcium-magnesium phosphate fertilizer has significantly raised soil pH from 5.10 to 6.45 (P < 0.05). The treatment of calcium-magnesium phosphate fertilizer and continuous flooding has reduced available content of Cd in soils by 28.57%. The content of Cd in brown rice was significantly diminished by 51.36% (P < 0.05). The continuous flooding has promoted formation of residual Cd in soil with application of calcium-magnesium phosphate fertilizer. The biomass and grain production of rice was not significantly decreased compared with control.

[Effects of the Immobilization of Cadmium in Soil Alone or Combined with Foliar Application of Selenium on Cadmium Accumulation in the Plants of Different Genotypes of Tsai-tai].

To explore the safe utilization of technology in mildly and moderately cadmium (Cd)-contaminated farmland and realize the safe production of agricultural products, two different cadmium-accumulating genotypes of Tsai-tai were used as test crops, using the pot experiment method. The same six treatments were set on the soil where the two test crops were planted:control (CK), addition of 3% (mass fraction) biochar (BC), addition of 0.17% calcium magnesium phosphate fertilizers (CMP), foliar application of 3 mg·L-1 Na2SeO3 aqueous solution (Se), BC+Se, and CMP+Se, to study the changes in available cadmium in soil under different treatments and the characteristics of cadmium accumulation in different parts of the plant. The results showed that:① Under the same treatment, the content of available cadmium in soil near the root of the low-cadmium-accumulating genotype of Tsai-tai of Jinqiuhong Ⅲ was significantly lower than that of the high-cadmium-accumulating genotype of Shiyuehong. BC and CMP had a significant passivating effect on cadmium in the soil near the root of Jinqiuhong Ⅲ, and the passivating effect of BC was better than that of CMP; the effect of passivating treatment was significantly better than that of foliar application of selenium. ② The root system of Tsai-tai of Jinqiuhong Ⅲ had a stronger ability to accumulate cadmium than that of Shiyuehong, and the accumulated cadmium tended to be stored in the root. There were no synergistic effects between the foliar application of selenium and the two kinds of passivants on inhibiting the transfer and enrichment of cadmium to the edible parts of Tsai-tai. ③ Under the treatments of BC and CMP, the content of cadmium in the edible part of Tsai-tai of Jinqiuhong Ⅲ was lower than the limit value of cadmium in GB 2762-2017 (0.10 mg·kg-1). This study shows that for mildly and moderately cadmium-contaminated farmland, applying green passivants such as biochar, calcium magnesium phosphate fertilizers, and planting crops with weak absorption and low accumulation can achieve the safe use of the cadmium-contaminated farmland and safe production of agricultural products.

Effects of calcium magnesium phosphate fertilizer, biochar and spent mushroom substrate on compost maturity and gaseous emissions during pig manure composting.

This study used a laboratory-scale system to investigate the effects of calcium magnesium phosphate fertilizer (CaMgP), biochar, and spent mushroom substrate (SMS) on compost maturity and gasous emissions during pig manure composting. The results showed that the addition of CaMgP, Biochar or SMS had no negative effect on the quality and maturity of compost, and all three additives could reduce the emissions of ammonia (NH3), hydrogen sulfide (H2S), dimethyl sulfide (Me2S) and dimethyl disulfide (Me2SS). Among them, the effect of adding CaMgP on NH3 emission reduction was the most obvious, reduced 42.90%. The emission reduction of CaMgP to H2S was similar to that of SMS, which decreased by 34.91% and 32.88% respectively. The emission reduction effects of the three additives on Me2S and Me2SS were obvious, all of which were over 50%. However, only adding SMS reduced the N2O emission by 37.08%.

Response of rice and bacterial community to phosphorus-containing materials in soil-plant ecosystem of rare earth mining area.

The effects of phosphate rock (PR), bone charcoal (BC), single superphosphate (SSP) and calcium magnesium phosphate (CMP) on rice growth and bacterial community structure in mining area of heavy and light rare earth elements(REEs) were studied by pot experiment, field experiments were conducted with CMP and BC as restorative materials. The pot experiment showed that BC, SSP and CMP improved dry weight of rice (especially grains) in two places by 84.23%, 116.97%, 81.83%, 1630.77%, 1817.95% and 902.56% respectively; and reduced REE content of rice (especially roots) in two places by 28.19%, 81.67%, 90.58%, 67.87%, 81.72% and 94.81%; PR had little effect on dry weight and REE content of rice in both places, but reduces Bacillusabundance in both places, while BC significantly improved the abundance of Perlucidibaca and Bacillus; CMP had little effect on bacterial community, two-year field experiments showed that dry weight of rice grain treated with BC was 100% and 43.0% higher than that treated with CK and CMP, and the content of REEs was 91.8% and 16.8% lower than that with CK and CMP. The results of pot and field experiments both show BC is the most potential material for restoring soil-plant ecosystem in REE mining area.

[Improvement effects of quicklime and calcium magnesium phosphate fertilizer on acidified soil cultivating Codonopsis tangshen.] / ç”ŸçŸ³ç°å’Œé’™é•ç£·è‚¥å¯¹é ¸åŒ–å·å šå‚åœŸå£¤çš„æ”¹è‰¯æ•ˆæžœ.

To solve the problem of soil acidification in the cultivation of Codonopsis tangshen, laboratory experiments were carried out to investigate C. tangshen seed germination, seedling growth and soil exchangeable acid, microbial community structure after applying quicklime (QL) and calcium magnesium phosphate fertilizer (CMP). The results showed that QL and CMP treatments significantly improved the survival rate of C. tangshen seedlings from 147.7% to 326.7% and from 270.1% to 311.2%, respectively. The maximum increase rates of the height of C. tangshen seedlings were 516.7% and 546.3%, and that of root length were 798.0% and 679.2% in the treatments of QL and CMP, respectively. 1‰-4‰ QL or CMP treatments increased the relative chlorophyll content, antioxidant enzyme activity and the content of soluble protein of C. tangshen seedlings, decreased the content of malondialdehyde and superoxide anion radical of seedlings, increased soil pH by 0.88-2.02 units and 0.23-1.19 units, and decreased the exchangeable aluminum content in soil by 53.0%-95.3% and 17.6%-81.3%, respectively. Soil bacterial and actinomycetic abundances were significantly higher in 2‰-4‰ QL or CMP treatments than that in the control. Soil fungal abundance was significantly lower in the QL treatment of 2‰ and CMP treatment of 4‰. 1‰-4‰ QL or CMP treatments significantly increased fresh weight of C. tangshen tubers by 40.5%-78.5% and 28.4%-78.8%, respectively. In conclusion, the suitable quantity of QL and CMP for acidified soil (pH=4.12, ρb=1.15 g·cm-3, tillage layer=15 cm) amendment were 1.73-3.45 t·hm-2 and 3.45-6.90 t·hm-2, and QL and CMP amendment could fit the optimum soil pH (5.5-6.5) for the growth of C. tangshen seedlings.

Performance of phosphogypsum and calcium magnesium phosphate fertilizer for nitrogen conservation in pig manure composting.

This study investigated the performance of phosphogypsum and calcium magnesium phosphate fertilizer for nitrogen conservation during pig manure composting with cornstalk as the bulking agent. Results show that phosphogypsum increased nitrous oxide (N2O) emission, but significantly reduced ammonia (NH3) emission and thus enhanced the mineral and total nitrogen (TN) contents in compost. Although N2O emission could be reduced by adding calcium magnesium phosphate fertilizer, NH3 emission was considerably increased, resulting in an increase in TN loss during composting. By blending these two additives, both NH3 and N2O emissions could be mitigated, achieving effective nitrogen conservation in composting. More importantly, with the addition of 20% TN of the mixed composting materials, these two additives could synergistically improve the compost maturity and quality.

Magnesium substitution in the structure of orthopedic nanoparticles: A comparison between amorphous magnesium phosphates, calcium magnesium phosphates, and hydroxyapatites.

As biocompatible materials, magnesium phosphates have received a lot of attention for orthopedic applications. During the last decade multiple studies have shown advantages for magnesium phosphate such as lack of cytotoxicity, biocompatibility, strong mechanical properties, and high biodegradability. The present study investigates the role of Mg(+2) and Ca(+2) ions in the structure of magnesium phosphate and calcium phosphate nanoparticles. To directly compare the effect of Mg(+2) and Ca(+2) ions on structure of nanoparticles and their biological behavior, three groups of nanoparticles including amorphous magnesium phosphates (AMPs) which release Mg(+2), calcium magnesium phosphates (CMPs) which release Mg(+2) and Ca(+2), and hydroxyapatites (HAs) which release Ca(+2) were studied. SEM, TEM, XRD, and FTIR were used to evaluate the morphology, crystallinity, and chemical properties of the particles. AMP particles were homogeneous nanospheres, whereas CMPs were combinations of heterogeneous nanorods and nanospheres, and HAs which contained heterogeneous nanosphere particles. Cell compatibility was monitored in all groups to determine the cytotoxicity effect of particles on studied MC3T3-E1 preosteoblasts. AMPs showed significantly higher attachment rate than the HAs after 1 day and both AMPs and CMPs showed significantly higher proliferation rate when compared to HAs after 7days. Gene expression level of osteoblastic markers ALP, COL I, OCN, OPN, RUNX2 were monitored and they were normalized to GAPDH housekeeping gene. Beta actin expression level was monitored as the second housekeeping gene to confirm the accuracy of results. In general, AMPs and CMPs showed higher expression level of osteoblastic genes after 7 days which can further confirm the stimulating role of Mg(+2) and Ca(+2) ions in increasing the proliferation rate, differentiation, and mineralization of MC3T3-E1 preosteoblasts.

Fabrication and cytocompatibility of spherical magnesium ammonium phosphate granules.

Magnesium phosphate compounds, as for example struvite (MgNH4PO4·6H2O), have comparable characteristics to calcium phosphate bone substitutes, but degrade faster under physiological conditions. In the present work, we used a struvite forming calcium doped magnesium phosphate cement with the formulation Ca0.75Mg2.25(PO4)2 and an ammonium phosphate containing aqueous solution to produce round-shaped granules. For the fabrication of spherical granules, the cement paste was dispersed in a lipophilic liquid and stabilized by surfactants. The granules were characterized with respect to morphology, size distribution, phase composition, compressive strength, biocompatibility and solubility. In general, it was seen that small granules can hardly be produced by means of emulsification, when the raw material is a hydraulic paste, because long setting times promote coalescence of initially small unhardened cement droplets. Here, this problem was solved by using an aqueous solution containing both the secondary (NH4)2HPO4 and primary ammonium phosphates NH4H2PO4 to accelerate the setting reaction. This resulted in granules with 97 wt.% having a size in the range between 200 and 1,000 µm. The novel solution composition doubled the compressive strength of the cement to 37 ± 5 MPa without affecting either the conversion to struvite or the cytocompatibility using human fetal osteoblasts.

Control of in vivo mineral bone cement degradation.

The current study aimed to prevent the formation of hydroxyapatite reprecipitates in brushite-forming biocements by minimizing the availability of free Ca(2+) ions in the cement matrix. This was achieved by both maximizing the degree of cement setting to avoid unreacted, calcium-rich cement raw materials which can deliver Ca(2+) directly to the cement matrix after dissolution, and by a reduction in porosity to reduce Ca(2+) diffusion into the set cement matrix. In addition, a biocement based on the formation of the magnesium phosphate mineral struvite (MgNH4PO4·6H2O) was tested, which should prevent the formation of low-solubility hydroxyapatite reprecipitates due to the high magnesium content. Different porosity levels were fabricated by altering the powder-to-liquid ratio at which the cements were mixed and the materials were implanted into mechanically unloaded femoral defects in sheep for up to 10 months. While the higher-porosity brushite cement quantitatively transformed into crystalline octacalcium phosphate after 10 months, slowing down cement resorption, a lower-porosity brushite cement modification was found to be chemically stable with the absence of reprecipitate formation and minor cement resorption from the implant surface. In contrast, struvite-forming cements were much more degradable due to the absence of mineral reprecipitates and a nearly quantitative cement degradation was found after 10 months of implantation.