Calcium Phosphate Cement Research Articles

Effect of porosity and phase composition in 3D printed calcium phosphate scaffolds on bone tissue regeneration in vivo

Highly porous calcium phosphate (CaP) scaffolds with multiple phases were fabricated through combination of material extrusion type 3D printing process, salt-leaching, and bone cement chemistry under physiological conditions. Scaffolds with nano-sized calcium deficient hydroxy apatite (CDHA) in the core and large crystals of dicalcium phosphate dihydrate (DCPD or brushite) on the outer surface were fabricated by immersing the 3D ceramic scaffold in aqueous ‘cement solution’. In contrast to conventional CaP cement reactions where a single product is obtained, here we could achieve a composite of apatite-brushite. The composite scaffolds showed improved compressive strength without loss of porosity which was suitable for efficient bone tissue regeneration. With 65 % porosity, these scaffolds showed compressive strength of 15 MPa. The porosity of CaP scaffold was increased by applying salt-leaching technique to 3D printing, which greatly influenced the biodegradation of the scaffold in vivo. Composite scaffolds with fast degrading brushite shell showed better and faster scaffold-to-bone integration compared to apatite based scaffold. In vivo studies verified that multi-phase CaP scaffolds with bimodal pore structure induced good new bone formation behavior (85 % of coverage rate on calvaria defect site after 11 weeks of implantation) with good biodegradability (76.6 % of degradation in rabbit subdermal model after 12 weeks of implantation).

Self-assembling of fibers inside an injectable calcium phosphate bone cement: a feasibility study

Calcium phosphate cements are biocompatible, bioactive, and osteogenic systems which have the potential to mimic the mineral phase of native bone and the ability to be molded into bone defects and implant sites, then harden in situ to provide stability. However, their mechanical strength needs to be improved. In the last few decades, the incorporation of preformed fibers into a brittle cement matrix has been proven to increase the mechanical properties. To obtain a better cohesion between the fibers and the cement paste thus improving the mechanical performances, in this work, we attempted the formation of self-assembling fibers in a single step during the setting of our calcium phosphate cement formulations.The formation of fibers was achieved by introducing a low-molecular-weight gelator (MW < 1000 Da) derived from l-Dopa: Boc-l-Dopa (Bn)2-OH. This molecule can form supramolecular structures, owing to weak interactions, and chelate Ca2+ ions to arrange into a fibrous network. The morphological analysis revealed that the gel was able to form fibers even inside such a dense matrix and their presence provided mechanical reinforcement both when tested in compression and in bending. Micro-CT analyses showed no variation in the total porosity, but an increase of pores diameter was observed when fibers are present. Moreover, the reinforced cements were able to ensure good cell viability and to express the main gene markers that are necessary for bone formation.

Application of a Cryo-FIB-SEM-μRaman Instrument to Probe the Depth of Vitreous Ice in a Frozen Sample

The development of instruments combining multiple characterization and imaging tools drove huge advances in material science, engineering, biology, and other related fields. Notably, the coupling of SEM with micro-Raman spectrometry (μRaman) provides the means for the correlation between structural and physicochemical properties at the surface, while dual focused ion beam (FIB)-scanning electron microscopes (SEMs) operating under cryogenic conditions (cryo-FIB-SEM) allow for the analysis of the ultrastructure of materials in situ and in their native environment. In cryo-FIB-SEM, rapid and efficient methods for assessing vitrification conditions in situ are required for the accurate investigation of the original structure of hydrated samples. This work reports for the first time the use of a cryo-FIB-SEM-μRaman instrument to efficiently assess the accuracy of cryo-fixation methods. Analyses were performed on plunge-freezed highly hydrated calcium phosphate cement (CPC) and a gelatin composite. By making a trench of a defined thickness with FIB, μRaman analyses were carried out at a specific depth within the frozen material. Results show that the μRaman signal is sensitive to the changes in the molecular structures of the aqueous phase and can be used to examine the depth of vitreous ice in frozen samples. The method presented in this work provides a reliable way to avoid imaging artifacts in cryo-FIB-SEM that are related to cryo-fixation and therefore constitutes great interest in the study of vitreous materials exhibiting high water content, regardless of the sample preparation method (i.e., by HPF, plunge freezing, and so on).

Automatic computation of bone defective volume from tomographic images

One of the most difficult aims of modern biomaterial science is predicting the shape and volume of a bone defect and adjusting the implementation of a bone substitute. Prior to implantation, practitioners must carefully identify the architecture and volume of the defective bone to be filled. This information is often accessed via imaging techniques. The defective bone is frequently confused with its surroundings and the image background. The use of conventional segmentation for the selection and isolation of the cavity to be filled proves to be difficult. In this work, a defect in a dead bone is created and then imaged with the microtomography technique (343 cuts generated). The goal is to separate the defect's shape and volume from both the bone and the background image. An adaptive morphological operation technique was employed to complete these tasks. The proposed method allows for exact segmentation and calculation of the volume of the cavity to be filled. Using several calculated phantoms, the approach is subjectively and quantitatively evaluated: Compared to the high error value of the conventional method, the error value of the proposed one has no bearing on the overall data. The method's accuracy was also confirmed by comparing the calculated volume of the bone defect (0.91 cm3) and the volume of prepared calcium phosphate cement paste necessary for its filling (0.87 cm3). To challenge the method even further, another direct application on a mandibular bone is realized with an advanced number of cuts (1236 cuts). The result of this application proved that the proposed algorithm overcomes the performance of the classical approaches of segmentation with a gain of 2 min on average. A comparison study between the proposed method and other classical segmentation approaches is also presented. The effectiveness of the method is proved by the various reports and metrics generated.The automated procedure can be beneficial in implantology for realizing and guiding surgical acts, as well as in computer-aided scaffolding techniques.

Fabrication of Radio-Opaque and Macroporous Injectable Calcium Phosphate Cement.

The aim of this work was the development of injectable radio-opaque and macroporous calcium phosphate cement (CPC) to be used as a bone substitute for the treatment of pathologic vertebral fractures. A CPC was first rendered radio-opaque by the incorporation of zirconium dioxide (ZrO2). In order to create macroporosity, poly lactic-co-glycolic acid (PLGA) microspheres around 100 μm were homogeneously incorporated into the CPC as observed by scanning electron microscopy. Physicochemical analyses by X-ray diffraction and Fourier transform infrared spectroscopy confirmed the brushite phase of the cement. The mechanical properties of the CPC/PLGA cement containing 30% PLGA (wt/wt) were characterized by a compressive strength of 2 MPa and a Young's modulus of 1 GPa. The CPC/PLGA exhibited initial and final setting times of 7 and 12 min, respectively. Although the incorporation of PLGA microspheres increased the force necessary to inject the cement and decreased the percentage of injected mass as a function of time, the CPC/PLGA appeared fully injectable at 4 min. Moreover, in comparison with CPC, CPC/PLGA showed a full degradation in 6 weeks (with 100% mass loss), and this was associated with an acidification of the medium containing the CPC/PLGA sample (pH of 3.5 after 6 weeks). A cell viability test validated CPC/PLGA biocompatibility, and in vivo analyses using a bone defect assay in the caudal vertebrae of Wistar rats showed the good opacity of the CPC through the tail and a significant increased degradation of the CPC/PLGA cement a month after implantation. In conclusion, this injectable CPC scaffold appears to be an interesting material for bone substitution.

Bioactivity evaluation of printable calcium polyphosphate/alginoplast cement for bone tissue engineering; In vitro study

By developing the three-dimensional (3D) printing technology and patient-specific medicine, 3D calcium phosphate cement, designed for every complex defect, remains a new challenge. This study developed a novel printable calcium polyphosphate (CPP) powder by adding alginoplast (ALG) to fabricated 3D cement using low-temperature binder jetting-based 3D printing without any sintering. The powder flowability and 3D cement biological properties were analyzed using Freeman technology, immersion in simulated body fluid (SBF) solution, and MG63 human osteoblast-like cells culture. According to the Freeman technology, adding 10 wt% of ALG in CPP showed better powder flowability. Together with the SEM, XRD, and FTIR results, the high bioactivity potential of 3D cement containing ALG was recorded by the cauliflower-like carbonate apatite formation on the 3D cement surface after 21 days of immersion. Furthermore, the 3D cement porous microstructure provided a cell attachment. The number of cells showed the 3D cement biocompatibility increased by increasing the cell culture time in 3D cement extraction through the MTT result.

The effects of initial temperature and pressure on the mechanical properties of reinforced calcium phosphate cement with magnesium nanoparticles: A molecular dynamics approach

Reinforcing cement with nanoparticles is a way to reduce porosity and enhance the initial strength of cement. In this work, the calcium phosphate cement is reinforced with magnesium ion nanoparticles using the molecular dynamics simulation method. This work investigates the mechanical and thermal properties of simulated samples. In this approach, the ultimate strength, Young's modulus, and thermal stability are studied. The effects of different initial temperature values and pressures will be researched next. As the initial temperature increased from 300 to 400 K, the ultimate strength and Young's modulus decreased from 0.879 and 0.171 MPa to 0.843 and 0.154 MPa. Also, the thermal stability reduced from 1321 to 1294 K. This material has more strength at lower than higher temperatures. With increasing temperature, the materials become softer and lose their strength. As the initial temperature in the atomic samples increases, the mobility intensifies, and as a result, the stability of the structures decreases. Increasing the initial pressure from 1 to 5 bar, the ultimate strength and Young's modulus enhanced from 0.879 and 0.171 MPa to 0.889 and 0.178 MPa. Also, the thermal stability increased from 1321 K to 1371 K by increasing the initial pressure to 5 bar. As the pressure increases, the amplitude of the particle oscillation decreases. The nanoparticle-reinforced cement matrix shows more appropriate behavior in high-pressure environments. It is expected that the addition of Mg nanoparticles will increase the strength of calcium phosphate cement and be used for use in bone lesions.

Novel degradable super-paramagnetic bone cement with self-controlled hyperthermia ability

Hyperthermia treatment with magnetic bone cement can not only realize the highly targeted treatment of the deep-seated bone tumor but also repair the weakened bone tissue. However, the potential risk of overheating limits the use of this material. Herein, we report a novel super-paramagnetic injectable radiopaque bone cement (MSBC) that can control hyperthermia temperature by itself. The injectable MSBC was prepared by incorporating SiO2-modified nano Mn-Zn-Cu-Gd ferrites into an acidic calcium phosphate cement matrix. The SiO2 layer on the ferrites protects the oxides from reacting with the acid matrix vigorously to keep the good magnetic property. The acid matrix allows the ferrites to degrade gradually and almost one-tenth of MSBC degrades after soaking in phosphate buffer solution for 28 days. Moreover, MSBC can realize self-controlled hyperthermia around Curie temperature (65 ℃) in vitro under an alternating magnetic field. The X-ray transmission results show that the radiopacity of MSBC is significantly enhanced in comparison to the matrix. Furthermore, MSBC shows no cytotoxicity and can promote the mineralization ability of osteoblasts. Overall, this novel magnetic bone cement provides a new avenue for improving the thermal safety of magnetic hyperthermia treatment of bone tumors.

Enhancement in the osteogenesis and angiogenesis of calcium phosphate cement by incorporating magnesium-containing silicates

Based on the good osteogenic and angiogenic effects of silicon and magnesium elements, three types of micro-nano magnesium-containing silicates (MS), including akermanite (Ake, Ca2MgSi2O7), diopside (Dio, CaMgSi2O6) and forsterite (For, Mg2SiO4), were incorporated into calcium phosphate cement (CPC) to improve its osteogenic and angiogenic performances for clinical application. In this present work, the physicochemical properties, osteogenesis and angiogenesis of MS/CPCs (Ake/CPCs, Dio/CPCs and For/CPCs) were investigated systematically and comparatively. The results showed that all MS/CPCs had good biomineralization and significantly stimulated the osteogenic differentiation of mBMSCs and angiogenic differentiation of HUVECs, respectively. Besides, the stimulating effects were related to not only the category of MS, but also the content of MS. The For/CPCs had a good angiogenic property but their initial setting times were beyond 60 min. The Dio/CPCs showed the lowest biological performance among the three groups of MS/CPCs due to the lower ion release (Si and Mg). The Ake was the ideal modifier that could provide CPC with appropriate physicochemical properties, better osteogenesis and angiogenesis. Simultaneously, a higher addition (10 wt%) of akermanite resulted in the best potential to bone regeneration. Taken together, this research provides an effective approach to improve the overall performance of CPC, and 10Ake/CPC is of great promising prospect in bone repair.

Calcium Phosphate Cement Promotes Odontoblastic Differentiation of Dental Pulp Cells In Vitro and In Vivo

In the case of pulp injury, odontoblastic differentiation of dental pulp cells (DPCs) at the site of the exposed pulp is necessary for a successful direct pulp capping treatment. Calcium phosphate cement (CPC), a kind of hydroxyapatite-like bone cement, exhibits therapeutic potential in osteogenesis by regulating cell cycle progression and promoting osteoblastic differentiation. Based on the similar biological process of osteo/odontoblastic differentiation, the present study evaluated the effects of CPC on odontoblastic differentiation of DPCs in vitro and in vivo, respectively. The morphology of CPC was observed by scanning electron microscopy. Colony-forming units were used to assess the antibacterial activity. The effects of CPC on cell proliferation and odontoblastic differentiation of human dental pulp cells (hDPCs) were also measured. Histological staining was performed to observe the reparative dentin formation in rat molars. In vitro, results of antibacterial studies showed that CPC significantly inhibited the growth of Streptococcus mutans. The appropriate concentration of CPC extract showed low cytotoxicity on hDPCs. Furthermore, CPC extract also promoted odontoblastic differentiation and mineralization compared with the control group, as shown by a dynamic increase in the expression of odontogenic marker genes and the increased number of mineralized nodules at 21 days. The pulpotomy models with CPC facilitated the formation of dentin bridge with the highly expressed dentin matrix protein 1 (DMP1) in odontoblast-like cells. In conclusion, the favorable biocompatibility, antibacterial property and bio-inductivity of CPC suggest that CPC can be used as a promising direct pulp capping material.

Accelerated bone regeneration through rational design of magnesium phosphate cements

Results of several studies during past years suggested that magnesium phosphate cements (MPCs) not only show excellent biocompatibility and osteoconductivity, but they also provide improved regeneration capacity due to higher solubility compared to calcium phosphates. These findings also highlighted that chemical similarity of bone substitutes to the natural bone tissue is not a determinant factor in the success of regenerative strategies. The aim of this study was to further improve the degradation speed of MPCs for a fast bone ingrowth within a few months. We confirmed our hypothesis, that decreasing the powder-liquid ratio (PLR) of cement results in an increased content of highly soluble phases such as struvite (MgNH4PO4⋅6H2O) as well as K-struvite (MgKPO4⋅6H2O). Promising compositions with a low PLR of 1 g ml−1 were implanted in partially-loaded tibia defects in sheep. Both cements were partially degraded and replaced by bone tissue after 4 months. The degradation speed of the K-struvite cement was significantly higher compared to the struvite cement, initially resulting in the formation of a cell-rich resorption zone at the surface of some implants, as determined by histology. Overall, both MPCs investigated in this study seem to be promising as an alternative to the clinically well-established, but slowly degrading calcium phosphate cements, depending on defect size and desired degradation rate. Whereas the K-struvite cement might require further modification towards a slower resorption and reduced inflammatory response in vivo, the struvite cement appears promising for the treatment of bone defects due to its continuous degradation with simultaneous new bone formation. Statement of significanceCold setting bone cements are used for the treatment of bone defects that exceed a critical size and cannot heal on their own. They are applied pasty into the bone defect and harden afterwards so that the shape adapts to the individual defect. Magnesium phosphates such as magnesium ammonium phosphate hexahydrate (struvite) belong to a new class of these cold setting bone cements. They degrade much faster than the clinically established calcium phosphates. In this study, a magnesium phosphate that has hardly been investigated so far was implanted into partially-loaded defects in sheeps: Potassium magnesium phosphate hexahydrate. This showed even faster resorption compared to the struvite cement: after 4 months, 63% of the cement was already degraded.

Effect of sodium silicate concentration on the physico-chemical properties of dual-setting bone-like apatite cements

Calcium phosphate cements (CPCs) with their biocompatibility, osteoconductivity and injectability plays an important role in bone defects treatment. Dual-setting cement is a promising approach to improve the physicochemical and biological properties of CPCs in which the liquid phase contains dissolved monomers that polymerized during hardening process. In this study, a series of dual-setting cements were prepared by mixing dicalcium phosphate dihydrate (DCPD) as a solid phase and sodium silicate solution (SS) with different concentrations as hardening liquids. The idea was to evaluate the effect of SS concentration on the setting mechanism, physicochemical and mechanical properties of the formulated cements. The setting kinetics was attributed to the DCPD dissolution and calcium deficient hydroxyapatite (CDHA) precipitation in parallel to SS polymerization to form sodium silicate gel. This was responsible for the formation of an interpenetrating composite material in which the formed gel fills the micropores of the CPC cement. The results showed that the setting time can be modulated by varying the SS concentrates in the hardening liquid. It was shown, as the SS content in the cement liquid increased from 10 to 30 wt%, the setting time decreased from 56 to 5 min. Moreover, the DCPD dissolution and CDHA precipitation were accelerated by increasing the SS concentration. The bone-like apatite cement with the highest SS content exhibited an enhanced compressive strength and high resorption rates. Overall, the addition of sodium silicate gel is a promising approach to regulate the different properties of the apatite-forming cement to be used for bone fracture treatment.

Engineering 3D Printed Scaffolds with Tunable Hydroxyapatite.

Orthopedic and craniofacial surgical procedures require the reconstruction of bone defects caused by trauma, diseases, and tumor resection. Successful bone restoration entails the development and use of bone grafts with structural, functional, and biological features similar to native tissues. Herein, we developed three-dimensional (3D) printed fine-tuned hydroxyapatite (HA) biomimetic bone structures, which can be applied as grafts, by using calcium phosphate cement (CPC) bioink, which is composed of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA), and a liquid [Polyvinyl butyral (PVB) dissolved in ethanol (EtOH)]. The ink was ejected through a high-resolution syringe nozzle (210 µm) at room temperature into three different concentrations (0.01, 0.1, and 0.5) mol/L of the aqueous sodium phosphate dibasic (Na2HPO4) bath that serves as a hardening accelerator for HA formation. Raman spectrometer, X-ray diffraction (XRD), and scanning electron microscopy (SEM) demonstrated the real-time HA formation in (0.01, 0.1, and 0.5) mol/L Na2HPO4 baths. Under those conditions, HA was formed at different amounts, which tuned the scaffolds’ mechanical properties, porosity, and osteoclast activity. Overall, this method may pave the way to engineer 3D bone scaffolds with controlled HA composition and pre-defined properties, which will enhance graft-host integration in various anatomic locations.

Bioactive Film-Guided Soft-Hard Interface Design Technology for Multi-Tissue Integrative Regeneration.

Control over soft‐to‐hard tissue interfaces is attracting intensive worldwide research efforts. Herein, a bioactive film‐guided soft–hard interface design (SHID) for multi‐tissue integrative regeneration is shown. Briefly, a soft bioactive film with good elasticity matchable to native ligament tissue, is incorporated with bone‐mimic components (calcium phosphate cement, CPC) to partially endow the soft‐film with hard‐tissue mimicking feature. The hybrid film is elegantly compounded with a clinical artificial ligament to act as a buffer zone to bridge the soft (ligament) and hard tissues (bone). Moreover, the bioactive film‐decorated ligament can be rolled into a 3D bio‐instructive implant with spatial‐controllable distribution of CPC bioactive motifs. CPC then promotes the recruitment and differentiation of endogenous cells in to the implant inside part, which enables a vascularized bone growth into the implant, and forms a structure mimicking the biological ligament–bone interface, thereby significantly improving osteointegration and biomechanical property. Thus, this special design provides an effective SHID‐guided implant‐bioactivation strategy unreached by the traditional manufacturing methods, enlightening a promising technology to develop an ideal SHID for translational use in the future.

Treatment of Critical Size Femoral Bone Defects with Biomimetic Hybrid Scaffolds of 3D Plotted Calcium Phosphate Cement and Mineralized Collagen Matrix.

To treat critical-size bone defects, composite materials and tissue-engineered bone grafts play important roles in bone repair materials. The purpose of this study was to investigate the bone regenerative potential of hybrid scaffolds consisting of macroporous calcium phosphate cement (CPC) and microporous mineralized collagen matrix (MCM). Hybrid scaffolds were synthetized by 3D plotting CPC and then filling with MCM (MCM-CPC group) and implanted into a 5 mm critical size femoral defect in rats. Defects left empty (control group) as well as defects treated with scaffolds made of CPC only (CPC group) and MCM only (MCM group) served as controls. Eight weeks after surgery, micro-computed tomography scans and histological analysis were performed to analyze the newly formed bone, the degree of defect healing and the activity of osteoclasts. Mechanical stability was tested by 3-point-bending of the explanted femora. Compared with the other groups, more newly formed bone was found within MCM-CPC scaffolds. The new bone tissue had a clamp-like structure which was fully connected to the hybrid scaffolds and thereby enhanced the biomechanical strength. Together, the biomimetic hybrid MCM-CPC scaffolds enhanced bone defect healing by improved osseointegration and their differentiated degradation provides spatial effects in the process of critical-bone defect healing.

Study on the improvement of compressive strength and fracture toughness of calcium phosphate cement

Calcium phosphate cement (CPC) has superior properties, such as excellent bioactivity, biocompatibility, osteoconductivity and degradability, since its hydration product is hydroxyapatite (HA). As a novel cement material, CPC also shows injectable and self-setting properties. However, the compressive strength (CS) and fracture toughness of most CPCs are far lower than that of human weight-bearing bones, which largely limit their applications in the repairment of weight-bearing bones. To improve the CS and fracture toughness of CPC, several methods, including in-situ reinforcement by Ca4(PO4)2O (TTCP) ceramic particles, suitable nanofibers are introduced in this study. The maximal CS of CPC prepared with TTCP (average particle size of 22.3 ± 0.4 μm) reached to 98.4 MPa, which is close to the strength of human long bones. The enhanced CS of CPC was attributed to the in-situ reinforcing effect of residual TTCP particles. Tendon collagen slices and HA nanofibers were used to improve the fracture toughness of CPC. The flexural strength (FS) and the work of facture (WOF) of CPC were slightly increased by adding HA nanofibers but was significantly increased by the addition of tendon collagen slices. With 1.000 wt% tendon collagen slices, the FS and WOF of CPC were increased by 61.3% and 22.6 times, respectively.

Adsorption of Inositol Phosphate on Hydroxyapatite Powder with High Specific Surface Area.

Chelate-setting calcium-phosphate cements (CPCs) have been developed using inositol phosphate (IP6) as a chelating agent. However, the compressive strength of the CPC fabricated from a commercially available hydroxyapatite (HAp) powder was approximately 10 MPa. In this study, we miniaturized HAp particles as a starting powder to improve the compressive strength of chelate-setting CPCs and examined the adsorption properties of IP6 onto HAp powders. An HAp powder with a specific surface area (SSA) higher than 200 m2/g (HApHS) was obtained by ultrasonic irradiation for 1 min in a wet synthesis process, greatly improving the SSA (214 m2/g) of the commercial powder without ultrasonic irradiation. The HApHS powder was found to be a B-type carbonate-containing HAp in which the phosphate groups in apatite were replaced by carbonate groups. Owing to the high SSA, the HApHS powder also showed high IP6 adsorption capacity. The adsorption phenomena of IP6 to our HApHS and commercially available Hap powders were found to follow the Freundlich and Langmuir models, respectively. We found that IP6 adsorbs on the HApHS powder by both physisorption and chemisorption. The fine HapHS powder with a high SSA is a novel raw powder material, expected to improve the compressive strength of chelate-setting CPCs.

A Comparative Evaluation of Fracture Resistance of Teeth Obturated with a Novel Sealer: Chitra CPC with Endosequence BC Sealer, MTA Fillapex and AH Plus

Background: Bonding of sealer to root canal walls is likely to increase the integrity of the sealer-dentin interface during mechanical stresses, thus increasing resistance to fracture. Chitra-CPC sealer is an indigenously manufactured bioceramic material and has been used as bone graft and perforation repair material. When used as a sealer, it has good potential to reinforce the root strength in addition to excellent biocompatibility.&#x0D; Aim: To compare the fracture resistance of teeth obturated with novel Calcium phosphate cement-based sealer viz. Chitra CPC with Endosequence BC sealer, MTA Fillapex and AH Plus&#x0D; Methods and Material: The study was carried out in 100 single rooted extracted, decoronated mandibular premolars of length 11 mm. The teeth were randomly divided into 4 groups (n = 20 for each group). Other than Group 1A and group1B, all other groups were restored with various endodontic sealers and obturated with Gutta Percha. In group1A, the teeth were left unprepared and unfilled (negative control), in group 1B, the teeth were left unobturated (positive control) In group 2, Epoxy resin based sealer (AHPlus ) ;In group 3, mineral trioxide aggregate–based sealer (MTAFill apex); In group 4, Calcium phosphate cement based sealer (Chitra-CPC);in group 5,Bioceramic based sealer(Endosequence BC ) were used. After 2 weeks all specimens were tested for fracture resistance using Universal testing machine at a crosshead speed of 1.0 mm/min until the root fractured. The force required to fracture each specimen was recorded, and the data was analysed statistically.&#x0D; Results: The fracture resistance values of Chitra –CPC and Endosequence BC sealer were significantly higher than that of positive control and comparable to negative control.&#x0D; Conclusions: In contrast to MTA Fill apex and AH Plus, Chitra –CPC and Endosequence BC sealer increased the fracture resistance of teeth.

A Mini-Pig Mandibular Defect Model for Evaluation of Craniomaxillofacial Bone Regeneration.

Craniomaxillofacial bone defects represent a clinical challenge in the fields of maxillofacial surgery and (implant) dentistry. Regeneration of these bone defects requires the application of bone graft materials that facilitate new bone formation in a safe, reliable, and predictive manner. In addition to autologous bone graft, several types of (synthetic) bone substitute materials have become clinically available, and still major efforts are focused on improving such bone substitute materials by optimizing their properties. Given the regulatory necessity to evaluate the performance of new bone substitute materials for craniomaxillofacial bone regeneration in a large animal model with similarity to human bone before clinical application, we here describe a mini-pig mandibular bone defect model that allows for the creation of multiple (critical-size) bone defects within the mandibular body of a single animal. As examples of bone substitute materials, we utilize both the clinically used BioOss granules and an experimental calcium phosphate cement for filling the created defects. Regarding the latter, its advantages are the injectable application within the defect site, in which the material rapidly sets, and the tailorable degradation properties via the inclusion of hydrolytically degrading polymeric particles. For both bone substitute materials, we show the suitability of the bone defect model to assess bone regeneration via histology and micro-computed tomography. Impact statement Given the regulatory necessity to evaluate the performance of new bone substitute materials for craniomaxillofacial bone regeneration in a large animal model with similarity to the human bone before clinical application, we here describe a mini-pig mandibular bone defect model that allows for the creation of multiple (critical-size) bone defects within the mandibular body of a single animal that can be used for the evaluation of the bone regenerative capacity of new bone grafting materials as well as tissue-engineered products for alveolar bone regeneration.

A New Augmentation Method for Improved Screw Fixation in Fragile Bone.

Pertrochanteric fractures (TF) due to osteoporosis constitute nearly half of all proximal femur fractures. TFs are treated with a surgical approach and fracture fixation is achieved using metallic fixation devices. Poor quality cancellous bone in osteoporotic patients makes anchorage of a fixation device challenging, which can lead to failure of the fracture fixation. Methods to reinforce the bone-implant interface using bone cement (PMMA) and other calcium phosphate cements in TFs have been described earlier but a clear evidence on the advantage of using such biomaterials for augmentation is weak. Furthermore, there is no standardized technique for delivering these biomaterials at the bone-implant interface. In this study, we firstly describe a method to deliver a calcium sulphate/hydroxyapatite (CaS/HA) based biomaterial for the augmentation of a lag-screw commonly used for TF fixation. We then used an osteoporotic Sawbones model to study the consequence of CaS/HA augmentation on the immediate mechanical anchorage of the lag-screw to osteoporotic bone. Finally, as a proof-of-concept, the method of delivering the CaS/HA biomaterial at the bone-implant interface as well as spreading of the CaS/HA material at this interface was tested in patients undergoing treatment for TF as well as in donated femoral heads. The mechanical testing results indicated that the CaS/HA based biomaterial increased the peak extraction force of the lag-screw by 4 times compared with un-augmented lag-screws and the results were at par with PMMA. The X-ray images from the patient series showed that it was possible to inject the CaS/HA material at the bone-implant interface without applying additional pressure and the CaS/HA material spreading was observed at the interface of the lag-screw threads and the bone. Finally, the spreading of the CaS/HA material was also verified on donated femoral heads and micro-CT imaging indicated that the entire length of the lag-screw threads was covered with the CaS/HA biomaterial. In conclusion, we present a novel method for augmenting a lag-screw in TFs, which could potentially reduce the risk of fracture fixation failure and reoperation in fragile osteoporotic patients.