Effect of biphasic calcium phosphate on human macrophage functions in vitro

Immunomodulatory effects of calcium phosphate microspheres: influences of particle size on macrophage polarization and secretion patterns

This study investigated the immunomodulatory effects of calcium phosphate (CaP) microspheres, focusing on how particle size influenced macrophage polarization and cytokine secretion patterns. SEM analysis revealed that HA microspheres predominantly exhibited a spherical shape with distinct sizes and sub-micro-sized pores. The average particle sizes for the S1, S2, and S3 groups were 17.36 μm, 27.59 μm, and 47.14 μm, respectively. In vitro experiments demonstrated that small-sized S1 microspheres were more readily phagocytosed by macrophages, leading to a pro-inflammatory M1 phenotype characterized by increased gene expression of iNos and inflammatory cytokines (IL-1β, IL-6, TNF-α), and a higher proportion of CCR7+ M1 macrophages. In contrast, the larger S2 and S3 microspheres favored an anti-inflammatory M2 phenotype, with higher expression of Arg and anti-inflammatory cytokines (IL-10), and greater proportions of CD206+ M2 macrophages. Additionally, HA microspheres were injected into mouse quadriceps muscles, revealing significant differences in immune cell infiltration and tissue response. The S1 microspheres induced a prolonged and more severe inflammatory response, while the S2 and S3 microspheres were embedded in cell-rich tissue with minimal inflammation or fibrosis. It indicated the potential of larger microspheres (S2 and S3) to create a more favorable immune microenvironment that supported faster and more effective tissue healing. These findings underscore the importance of optimizing microsphere size to achieve desired immunomodulatory effects, thereby enhancing their clinical efficacy.

Investigation of the combustion process of fish scales from Northeast Brazil in a drop tube furnace (DTF)

The waste generated by the global fishing industry, such as fish scales, is mostly considered useless and discarded in a disorderly and/or unplanned way in inappropriate places, posing serious risks to both the environment and human health. This study proposes the use of fish scales in combustion processes as an alternative for such residues and to avoid their exposure in urban areas. Combustion experiments were conducted in a drop tube furnace (DTF), and the factors temperature, residence time, and sample particle size were investigated. The main atmospheric pollutants (CO, NO, CO₂, and SO₂) and the residues generated from the combustion processes were characterized by FTIR, EDS and ICP-OES analyses, and SEM images. The samples showed better performance at 1100 °C and 500 -ms residence time, when the burnout reached 96%, and particle size greater than 300-μm and 300-ms residence time led to the worst combustion performance (24.45% burnout), with the highest CO and NO peaks, indicating incomplete combustion of the fish scales. The analysis of the residues revealed total decomposition of the organic matter at temperatures above 700 °C and formation of hydroxyapatite. According to the DTF results, the use of fish scales in firing processes is a viable treatment of the residues, generating energy and avoiding environmental problems caused by inadequate disposal.

Applying extrusion-based 3D printing technique accelerates fabricating complex biphasic calcium phosphate-based scaffolds for bone tissue regeneration

•

Biphasic calcium phosphates offer a chemically similar biomaterial to the natural bone, which can significantly accelerate bone formation and reconstruction.

•

Robocasting is a suitable technique to produce porous scaffolds supporting cell viability, proliferation, and differentiation.

•

This review discusses materials and methods utilized for BCP robocasting, considering recent advancements and existing challenges in using additives for bioink preparation.

•

Commercialization and marketing approach, in-vitro and in-vivo evaluations, biologic responses, and post-processing steps are also investigated.

•

Possible strategies and opportunities for the use of BCP toward injured bone regeneration along with clinical applications are discussed.

•

The study proposes that BCP possesses an acceptable level of bone substituting, considering its challenges and struggles.

Background

Aim of review

Key scientific concepts of review

Synergistic Effect of Biphasic Calcium Phosphate and Platelet-Rich Fibrin Attenuate Markers for Inflammation and Osteoclast Differentiation by Suppressing NF-κB/MAPK Signaling Pathway in Chronic Periodontitis

Background: Periodontitis is characterized by excessive osteoclastic activity, which is closely associated with inflammation. It is well established that MAPK/NF-kB axis is a key signaling pathway engaged in osteoclast differentiation. It is stated that that biphasic calcium phosphate (BCP) and platelet-rich fibrin (PRF) have significant antiostoeclastogenic effects in chronic periodontitis. Objective: We aimed to elucidate the synergetic effect of PRF/BCP involvement of the nuclear factor kappa–light–chain–enhancer of activated B cells (NF-kB) and the mitogen-activated protein kinase (MAPK) signaling pathway in osteoclast differentiation in chronic periodontitis. Methods: We induced osteoclast differentiation in vitro using peripheral blood mononuclear cells (PBMCs) derived from patients with chronic periodontitis. We assessed osteoclast generation by tartrate-resistant acid phosphatase (TRAP) activity, proinflammatory cytokines were investigated by ELISA and NF-κB, and IKB by immunoblot, respectively. MAPK proteins and osteoclast transcription factors were studied by Western blot analysis and osteoclast transcriptional genes were assessed by RT-PCR. Results: The results showed that the potent inhibitory effect of PRF/BCP on osteoclastogenesis was evidenced by decreased TRAP activity and the expression of transcription factors, NFATc1, c-Fos, and the osteoclast marker genes, TRAP, MMP-9, and cathepsin-K were found to be reduced. Further, the protective effect of PRF/BCP on inflammation-mediated osteoclastogenesis in chronic periodontitis was shown by decreased levels of proinflammatory cytokines, NF-kB, IKB, and MAPK proteins. Conclusions: PRF/BCP may promote a synergetic combination that could be used as a strong inhibitor of inflammation-induced osteoclastogenesis in chronic periodontitis.

Novel titanium-apatite hybrid scaffolds with spongy bone-like micro architecture intended for spinal application: In vitro and in vivo study

Titanium alloy scaffolds with novel interconnected and non-periodic porous bone-like micro architecture were 3D-printed and filled with hydroxyapatite bioactive matrix. These novel metallic-ceramic hybrid scaffolds were tested in vitro by direct-contact osteoblast cell cultures for cell adhesion, proliferation, morphology and gene expression of several key osteogenic markers. The scaffolds were also evaluated in vivo by implanting them on transverse and spinous processes of sheep's vertebras and subsequent histology study. The in vitro results showed that: (a) cell adhesion, proliferation and viability were not negatively affected with time by compositional factors (quantitative MTT-assay); (b) the osteoblastic cells were able to adhere and to attain normal morphology (fluorescence microscopy); (c) the studied samples had the ability to promote and sustain the osteogenic differentiation, matrix maturation and mineralization in vitro (real-time quantitative PCR and mineralized matrix production staining). Additionally, the in vivo results showed that the hybrid scaffolds had greater infiltration, with fully mineralized bone after 6 months, than the titanium scaffolds without bioactive matrix. In conclusion, these novel hybrid scaffolds could be an alternative to the actual spinal fusion devices, due to their proved osteogenic performance (i.e. osteoinductive and osteoconductive behaviour), if further dimensional and biomechanical optimization is performed.

Three-Dimensional Architecture and Mechanical Properties of Bovine Bone Mixed with Autologous Platelet Liquid, Blood, or Physiological Water: An In Vitro Study

In recent years, several techniques and material options have been investigated and developed for bone defect repair and regeneration. The progress in studies of composite graft materials and autologous platelet-derived growth factors for bone regeneration in dentistry and their biological and biomechanical properties has improved clinical strategies and results. The aim of this study was to evaluate the three-dimensional architecture and mechanical properties of three different combinations of composite bovine graft, adding autologous platelet liquid (APL), blood, or physiological water. One experimental group for each combination of biomaterials was created. In particular, in Group I, the bovine graft was mixed with APL; in Group II, it was mixed with blood, and in Group III, the biomaterial graft was combined with physiological water. Then, the composite biomaterials were evaluated by scanning electron microscopy (SEM), and a compression-loading test was conducted. The evaluation showed a statistical significance (p < 0.01) of the elastic regime of deformation resistance, in which the combination of APL with bone graft resulted in an 875% increase in the mechanical resistance. The protocol of APL mixed with bovine bone graft produced a composite sticky graft block that was capable of increasing the mechanical properties in order to improve its clinical use in the treatment of the maxillary bone defects.

Biphasic calcium phosphate ceramics for bone reconstruction: A review of biological response

Autologous bone graft is considered as the gold standard in bone reconstructive surgery. However, the quantity of bone available is limited and the harvesting procedure requires a second surgical site resulting in severe complications. Due to these limits, scientists and clinicians have considered alternatives to autologous bone graft. Calcium phosphates (CaPs) biomaterials including biphasic calcium phosphate (BCP) ceramics have proven efficacy in numerous clinical indications. Their specific physico-chemical properties (HA/TCP ratio, dual porosity and subsequent interconnected architecture) control (regulate/condition) the progressive resorption and the bone substitution process. By describing the most significant biological responses reported in the last 30years, we review the main events that made their clinical success. We also discuss about their exciting future applications as osteoconductive scaffold for delivering various bioactive molecules or bone cells in bone tissue engineering and regenerative medicine.

STATEMENT OF SIGNIFICANCE

Nowadays, BCPs are definitely considered as the gold standard of bone substitutes in bone reconstructive surgery. Among the numerous clinical studies in literature demonstrating the performance of BCP, Passuti et al. and Randsford et al. studies largely contributed to the emergence of the BCPs. It could be interesting to come back to the main events that made their success and could explain their large adhesion from scientists to clinicians. This paper aims to review the most significant biological responses reported in the last 30years, of these BCP-based materials. We also discuss about their exciting future applications as osteoconductive scaffold for delivering various bioactive molecules or bone cells in bone tissue engineering and regenerative medicine.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Effects of titanium surfaces on the developmental profile of monocytes/macrophages

Due to the critical role of monocytes/macrophages (Mϕ) in bone healing, this study evaluated the effects of bio-anodized, acid-etched, and machined titanium surfaces (Ti) on Mϕ behavior. Cells were separated from whole human blood from 10 patients, plated on Ti or polystyrene (control) surfaces, and cultured for 72 h. At 24, 48 and 72 h, cell viability, levels of IL1β, IL10, TNFα, TGFβ1 inflammatory mediators, and nitric oxide (NO) release were analyzed by mitochondrial colorimetric assay (MTT assay) and immunoenzymatic assays, respectively. Real-time PCR was used to verify the expression of TNFα and IL10 at 72 h. The data were subjected to a Kruskal-Wallis analysis. IL1β, TNFα and TGFβ1 release were not significantly different between the Ti surfaces (p>0.05). The presence of NO and IL10 was not detected in the samples. Cell viability did not differ between the samples cultivated on Ti and those cultivated on control surfaces, except at 24 h (p=0.0033). With respect to the mediators evaluated, the surface characteristics did not induce a typical Th1 or Th2 cytokine profile, although the cell morphology and topography were influenced by the Ti surface during the initial period.

OsteoMacs: Key players around bone biomaterials

Osteal macrophages (OsteoMacs) are a special subtype of macrophage residing in bony tissues. Interesting findings from basic research have pointed to their vast and substantial roles in bone biology by demonstrating their key function in bone formation and remodeling. Despite these essential findings, much less information is available concerning their response to a variety of biomaterials used for bone regeneration with the majority of investigation primarily focused on their role during the foreign body reaction. With respect to biomaterials, it is well known that cells derived from the monocyte/macrophage lineage are one of the first cell types in contact with implanted biomaterials. Here they demonstrate extremely plastic phenotypes with the ability to differentiate towards classical M1 or M2 macrophages, or subsequently fuse into osteoclasts or multinucleated giant cells (MNGCs). These MNGCs have previously been characterized as foreign body giant cells and associated with biomaterial rejection, however more recently their phenotypes have been implicated with wound healing and tissue regeneration by studies demonstrating their expression of key M2 markers around biomaterials. With such contrasting hypotheses, it becomes essential to better understand their roles to improve the development of osteo-compatible and osteo-promotive biomaterials. This review article expresses the necessity to further study OsteoMacs and MNGCs to understand their function in bone biomaterial tissue integration including dental/orthopedic implants and bone grafting materials.

Structure and solubility behaviour of zinc containing phosphate glasses

The structure of phosphate glasses of general composition 10Na₂O : (20 + x/2)ZnO : (20 + x/2)CaO : (50 -x)P₂O₅ (0 ≤x≤ 20) has been investigated using IR spectroscopy, 1D ³¹P and ⁴³Ca MAS Bloch decay, ³¹P-³¹P double quantum MAS-NMR and ⁴³Ca and ⁶⁷Zn static NMR techniques, as well as neutron diffraction analysis. Zinc is shown to aid glass formation in this system. Glass transition temperature and density increase with increasing cation : phosphate ratio. However, free volume calculations show structures becoming significantly more compact from x = 5 to x = 10. The structural data confirm depolymerisation of the glasses with increasing cation : phosphate ratio. Zinc oxide is found to act in a network forming role in the system, with ⁶⁷Zn NMR and neutron diffraction analysis confirming zinc exhibits predominantly four-coordinate geometry. Solubility in deionised water and tris/HCl buffer solution is seen to decrease significantly with increasing x-value. This is discussed in terms of water ingress and the degree of structural openness, associated with increased cross-linking and a decrease in concentration of P-O-P linkages. pH measurements confirm invert phosphate compositions maintain physiological pH levels on immersion in water and buffer solutions for up to four weeks.

Platelet-rich plasma in bone regeneration: engineering the delivery for improved clinical efficacy

Human bone is a tissue with a fairly remarkable inherent capacity for regeneration; however, this regenerative capacity has its limitations, and defects larger than a critical size lack the ability to spontaneously heal. As such, the development and clinical translation of effective bone regeneration modalities are paramount. One regenerative medicine approach that is beginning to gain momentum in the clinical setting is the use of platelet-rich plasma (PRP). PRP therapy is essentially a method for concentrating platelets and their intrinsic growth factors to stimulate and accelerate a healing response. While PRP has shown some efficacy in both in vitro and in vivo scenarios, to date its use and delivery have not been optimized for bone regeneration. Issues remain with the effective delivery of the platelet-derived growth factors to a localized site of injury, the activation and temporal release of the growth factors, and the rate of growth factor clearance. This review will briefly describe the physiological principles behind PRP use and then discuss how engineering its method of delivery may ultimately impact its ability to successfully translate to widespread clinical use.

Cell-mediated degradation of strontium-doped calcium polyphosphate scaffold for bone tissue engineering

Bio-ceramic porous scaffolds used in bone tissue engineering are incorporated in vivo by a process of cellular in-growth, followed by cell-mediated degradation and replacement of these scaffolds, in which macrophages and osteoclasts play the key role. Calcium polyphosphate (CPP) is an inorganic polymeric bioceramic which has been increasingly studied as a bone graft. The solution-mediated chemical degradation of strontium-substituted calcium polyphosphate (SCPP) scaffolds is well established in vitro, but an in vitro model of cell-mediated SCPP scaffold degradation has not been investigated. Herein, RAW264.7 (a murine monocyte/macrophage cell line) and osteoclasts were cultured on CPP and SCPP scaffolds. The weight loss and release amount of Sr(2+), Ca(2+) and PO(4)(3-) in a degradation medium indicated that macrophages could accelerate the degradation of SCPP. According to the results from MTT assay and scanning electron microscopy, it was found that a low dose of strontium was beneficial to the proliferation of macrophages, while strontium inhibited the activity of osteoclasts. This study will aid in developing SCPP scaffolds for in vivo bone tissue engineering.

In vitro and in vivo evaluation of the biocompatibility of a calcium phosphate/poly(lactic-co-glycolic acid) composite

This study assess the effects of bioceramic and poly(lactic-co-glycolic acid) composite (BCP/PLGA) on the viability of cultured macrophages and human dental pulp fibroblasts, and we sought to elucidate the temporal profile of the reaction of pulp capping with a composite of bioceramic of calcium phosphate and biodegradable polymer in the progression of delayed dentine bridge after (30 and 60 days) in vivo. Histological evaluation of inflammatory infiltrate and dentin bridge formation were performed after 30 and 60 days. There was similar progressive fibroblast growth in all groups and the macrophages showed viability. The in vivo study showed that of the three experimental groups: BCP/PLGA composite, BCP and calcium hydroxide (Ca(OH)(2)) dentin bridging was the most prevalent (90 %) in the BCP/PLGA composite after 30 days, mild to moderate inflammatory response was present throughout the pulp after 30 days. After 60 days was observed dentine bridging in 60 % and necrosis in 40 %, in both groups. The results indicate that understanding BCP/PLGA composite is biocompatible and by the best tissue response as compared to calcium hydroxide in direct pulp capping may be important in the mechanism of delayed dentine bridge after 30 and 60 days.

Biphasic, triphasic and multiphasic calcium orthophosphates

Biphasic, triphasic and multiphasic (polyphasic) calcium orthophosphates have been sought as biomaterials for reconstruction of bone defects in maxillofacial, dental and orthopedic applications. In general, this concept is determined by advantageous balances of more stable (frequently hydroxyapatite) and more resorbable (typically tricalcium orthophosphates) phases of calcium orthophosphates, while the optimum ratios depend on the particular applications. Therefore, all currently known biphasic, triphasic and multiphasic formulations of calcium orthophosphate bioceramics are sparingly soluble in water and, thus, after being implanted they are gradually resorbed inside the body, releasing calcium and orthophosphate ions into the biological medium and, hence, seeding new bone formation. The available formulations have already demonstrated proven biocompatibility, osteoconductivity, safety and predictability in vitro, in vivo, as well as in clinical models. More recently, in vitro and in vivo studies have shown that some of them might possess osteoinductive properties. Hence, in the field of tissue engineering biphasic, triphasic and multiphasic calcium orthophosphates represent promising biomaterials to construct various scaffolds capable of carrying and/or modulating the behavior of cells. Furthermore, such scaffolds are also suitable for drug delivery applications. This review summarizes the available information on biphasic, triphasic and multiphasic calcium orthophosphates, including their biomedical applications. New formulations are also proposed.

In vitro: osteoclastic activity studies on surfaces of 3D printed calcium phosphate scaffolds

Various biomaterials have been developed for the use as bone substitutes for bone defects. To optimize their integration and functionality, they should be adapted to the individual defect. Rapid prototyping is a manufacturing method to tailor materials to the 3D geometry of the defect. Especially 3D printing allows the manufacture of implants, the shape of which can be designed to fit the bone defect using anatomical information obtained from the patient. 3D printing of calcium phosphates, which are well established as bone substitutes, involves a sintering step after gluing the granules together by a binder liquid. In this study, we analyzed if and how these 3D printed calcium phosphate surfaces can be resorbed by osteoclast-like cells. On 3D printed scaffold surfaces consisting of pure HA and β-TCP as well as a biphasic mixture of HA and TCP the osteoclastic cell differentiation was studied. In this regard, cell proliferation, differentiation, and activation were analyzed with the monocytic cell line RAW 264.7. The results show that osteoclast-like cells were able to resorb calcium phosphate surfaces consisting of granules. Furthermore, biphasic calcium phosphate ceramics exhibit, because of their osteoclastic activation ability, the most promising surface properties to serve as 3D printed bone substitute scaffolds.

Influence of recovering collagen with bioactive glass on osteoblast behavior

Bioactive ceramics have interesting properties from the biological standpoint, but their effects on cellular events remain partially unknown. In the current work, we investigated cellular viability, proliferation, and metabolic activity of rat primary osteoblasts in contact with four different samples: type I collagen, bioactive glass-coated collagen (GC), and both samples submitted to immersion for 5 days in a simulated body fluid. The bioactive glass coating was obtained from a sol-gel process. The cell viability, the alkaline phosphate, the collagen secretion, and the nitric oxide production by osteoblast were measured after 72 h of incubation in the presence of the samples. The GC that was immersed for 5 days in a simulated body fluid solution showed an increase in osteoblast viability and proliferation when it was compared with control and the other samples.

The Effect of Platelet-Rich Plasma on the Bone Healing around Calcium Phosphate–Coated and Non-coated Oral Implants in Trabecular Bone

The effect of local application of autologous platelet-rich plasma (PRP) on bone healing in combination with the use of titanium implants with 2 different surface configurations was investigated. PRP fractions were obtained from venous blood sample of 6 goats and applied via gel preparation and subsequent installation in the implant site or via dipping of the implant in PRP liquid before insertion. Thirty-six implants (18 non-coated and 18 calcium phosphate (CaP) coated) were placed into the goat femoral condyles (trabecular bone). The animals were sacrificed at 6 weeks after implantation, and implants with surrounding tissue were processed for light microscopical evaluation. In addition to subjective description of the histological findings, histomorphometrical variables were also evaluated (the bone-implant contact and the bone mass adjacent to the implant). Significantly more interfacial bone-to-implant contact was observed for all 3 groups of CaP-coated implants and the titanium / liquid group (non-coated implant with PRP liquid) than for the other 2 non-coated titanium groups (with PRP gel or without PRP). The evaluation of the bone mass close to implant surface indicated that all the groups induced a significant increase of the bone mass except the PRP gel groups. On the basis of the observations, it was concluded that magnetron-sputtered CaP coatings can improve the integration of oral implants in trabecular bone. The additional use of PRP did not offer any significant effect on the bone response to the CaP-coated implants, whereas PRP in a liquid form showed a significant effect on bone apposition to roughened titanium implants during the early post-implantation healing phase.

In vitro Evaluation of Potential Calcium Phosphate Scaffolds for Tissue Engineering

Nanocrystalline calcium phosphates are very interesting candidates as scaffolds for bone tissue engineering. These materials show excellent in vivo biocompatibility, cell proliferation, and resorption. In this work we have studied the osteoblast-like cell behavior seeded onto HA and BCP synthesized by controlled crystallization method and treated at different temperatures. In vitro cell attachment, proliferation, differentiation, spreading, and cytotoxicity tests have been carried out. The results can be explained as a function of the phase composition and microstructure. Under in vitro closed conditions, nanocrystalline HA depletes the calcium of the medium avoiding cell proliferation, whereas well-crystallized HA enhances high cell proliferation. On the other hand, nanocrystalline BCPs supply Ca(2+) to the medium due to the higher solubility of the beta-TCP component, allowing an excellent in vitro cellular response when osteoblast-like cells are seeded on it. These features make BCPs excellent candidates as scaffolds for bone tissue engineering.

The effect of ionic products from bioactive glass dissolution on osteoblast proliferation and collagen production

Bioactive ceramics developed during the past few decades have interesting properties from the biological standpoint, but their effects on cellular events remain partially unknown. In the current work, we investigated cellular viability, proliferation, morphology changes and metabolic activity of rat primary culture osteoblasts in contact with the ionic products from the dissolution of a bioactive glass with 60% of silica (BG60S) and a biphasic calcium phosphate (BCP). We observed that although osteoblasts cultured with BG60S showed vacuole formation, cell viability was increased when compared to BCP and control. The vacuole formation was not due to the presence of high calcium concentration in the ionic products from the dissolution of BG60S and was not related to nitric oxide production from the osteoblasts. We did find that high silicon concentration could induce cellular vacuole formation. Additionally, energy dispersive spectroscopy analysis indicated that vacuole contained 75% more silicon than other regions in the cell outside the vacuole. We further found that collagen production was higher in osteoblast cultured in the presence of BG60S compared to BCP and control, while alkaline phosphatase production was similar among cells incubated with BG60S, BCP and control. Together, our results indicate that osteoblast vacuole formation was due to high silicon contents in the dissolution of BG60S and we can suggest that despite the vacuole formation, there is no significant alteration in the bioceramic cell interaction.

In vivo behavior of three different injectable hydraulic calcium phosphate cements

Two dicalcium phosphate dihydrate (DCPD) hydraulic cements and one apatite hydraulic cement were implanted in epiphyseal and metaphyseal, cylindrical bone defects of sheep. The in vivo study was performed to assess the biocompatibility of the DCPD cements, using the apatite cement as control. After time periods of 2, 4 and 6 months the cement samples were clinically and histologically evaluated. Histomorphometrically the amount of new bone formation, fibrous tissue and the area of remaining cement were measured over time. In all specimens, no signs of inflammation were detectable either macroscopically or microscopically. All cements were replaced by different amounts of new bone. The two DCPD-cements showed the highest new bone formation and least cement remnants at 6 months, whereas the apatite was almost unchanged over all time periods.