Low-temperature particulate calcium phosphates for bone regeneration

Comparing the effect of using calcified autogenous nano dentin particles versus micro dentin particles in the healing of mandibular bony defects in New Zealand rabbits

OBJECTIVE

This study aimed to compare the regenerative effect of autogenous micro-dentin and nano-dentin particles on bone regeneration in rabbits' mandibular defects. Sixty adult New Zealand rabbits were randomly divided into three groups: a control group, a micro-dentin group, and a nano-dentin group. A critical-sized bony defect was created at the lower border of the mandible. Bone regeneration was evaluated at two, four, and eight weeks using light microscopy, cone beam computed tomography (CBCT) scans, and histomorphometric analysis.

RESULTS

Nano-dentin significantly enhanced bone density and defect closure, as evidenced by CBCT and histological analyses. At eight weeks, it promoted extensive new bone formation, nearly bridging the defect, with minimal residual graft material compared to the micro-dentin group. Histomorphometric analysis confirmed its superior osteogenic potential, demonstrating enhanced bone regeneration and graft resorption. These findings highlight nano-dentin as a highly effective biomaterial for mandibular bone repair.

Multiparametric influence of 3D-printed organo-mineral scaffolds on bone regeneration

The development of synthetic bone substitutes that equal or exceed the efficacy of autologous graft remains challenging. In this study, a rat calvarial defect model was used as a reference to investigate the influence of composition and architecture of 3D-printed cement, with or without bioactives, on tissue regeneration. Printable cement pastes were formulated by combining hyaluronic acid and cement precursors. Cementitious scaffolds were printed with 3 different patterns. After 7 weeks of implantation with or without bone marrow, multiparametric qualitative and quantitative assessments were performed using µCT, SEM, and histology. None of the set-up strategies was as efficient as autologous cancellous bone graft to repair calvarial defects. Nonetheless, the presence of scaffold improved the skull vault closure, particularly when the scaffold was soaked in total bone marrow before implantation. No significant effect of scaffold macro-architecture was observed on tissue mineralization. Magnesium phosphate-based scaffolds (MgP) seemed to induce higher bone formation than their calcium-phosphate-based counterparts. They also displayed a quicker biodegradation and sparse remaining material was found after 7 weeks of implantation. Although further improvements are required to reach clinical settings, this study demonstrated the potential of organo-mineral cements for bone regeneration and highlighted the peculiar properties of MgP-based cements.

Property and biological effects of the cuttlebone derived calcium phosphate particles, a potential bioactive bone substitute material

Cuttlebone (CB) is a marine waste-derived biomaterial and a rich source of calcium carbonate for the biosynthesis of the calcium phosphate (CaP) particles. The current study aimed to synthesize CB derived biphasic calcium phosphate (CB-BCP) and investigate biological activity of the CB-CaP: hydroxyapatite (CB-HA), beta-tricalcium phosphate (CB-b-TCP) and biphasic 60:40 (w/w) HA/b-TCP (CB-BCP) with the human dental pulp stem cells (hDPSCs). The particles were synthesized using solid state reactions under mild condition and properties of the particles were compared with a commercial BCP as a reference material. Morphology, particle size, physicochemical properties, mineral contents, and the ion released patterns of the particles were examined. Then the particle/cell interaction, cell cytotoxicity and osteogenic property of the particles were investigated in the direct and indirect cell culture models. It was found that an average particles size of the CB-HA was 304.73 ± 4.19 nm, CB-b-TCP, 503.17 ± 23.06 nm and CB-BCP, 1394.67 ± 168.19 nm. The physicochemical characteristics of the CB-CaP were consistent with the HA, b-TCP and BCP. The highest level of calcium (Ca) was found in the mineral contents and the preincubated medium of the CB-BCP and traces of fluoride, magnesium, strontium, and zinc were identified in the CB-CaP. The cell cytotoxicity and osteogenic property of the particles were dose dependent. The particles adhered on cell surface and were internalized into the cell cytoplasm. The CB-BCP and CB-HA indirectly and directly promote osteoblastic differentiations of the hDPSCs in stronger levels than other groups. The CB-BCP and CB-HA were potential bioactive bone substitute materials.

Injectable bone cements: What benefits the combination of calcium phosphates and bioactive glasses could bring?

Out of the wide range of calcium phosphate (CaP) biomaterials, calcium phosphate bone cements (CPCs) have attracted increased attention since their discovery in the 1980s due to their valuable properties such as bioactivity, osteoconductivity, injectability, hardening ability through a low-temperature setting reaction and moldability. Thereafter numerous researches have been performed to enhance the properties of CPCs. Nonetheless, low mechanical performance of CPCs limits their clinical application in load bearing regions of bone. Also, the in vivo resorption and replacement of CPC with new bone tissue is still controversial, thus further improvements of high clinical importance are required. Bioactive glasses (BGs) are biocompatible and able to bond to bone, stimulating new bone growth while dissolving over time. In the last decades extensive research has been performed analyzing the role of BGs in combination with different CaPs. Thus, the focal point of this review paper is to summarize the available research data on how injectable CPC properties could be improved or affected by the addition of BG as a secondary powder phase. It was found that despite the variances of setting time and compressive strength results, desirable injectable properties of bone cements can be achieved by the inclusion of BGs into CPCs. The published data also revealed that the degradation rate of CPCs is significantly improved by BG addition. Moreover, the presence of BG in CPCs improves the in vitro osteogenic differentiation and cell response as well as the tissue-material interaction in vivo.

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Properties of injectable calcium phosphate bone cements and bioactive glasses are discussed.

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Benefits that BG addition to CPC could bring are highlighted.

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Desirable injectable properties of bone cements can be achieved by the inclusion of BGs into CPCs.

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The presence of BG in CPC advances in vitro and in vivo response of the composites.

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Future research direction of BG containing injectable CPC composites are provided.

Bone regeneration of a polymeric sponge technique-Alloplastic bone substitute materials compared with a commercial synthetic bone material (MBCP+TM technology): A histomorphometric study in porcine skull

Background

Polymeric sponge technique is recommended for developing the desired porosity of Biphasic calcium phosphate (BCP) which may favor bone regeneration.

Purpose

To investigate the healing of BCP with ratio of HA30/β‐TCP70 (HA30) and HA70/β‐TCP30 (HA70) polymeric sponge preparation, compare to commercial BCP (MBCP+TM).

Materials and Methods

Materials were tested X‐ray diffraction (XRD) pattern and scanning electron microscope (SEM) analysis. In eight male pigs, six calvarial defects were created in each subject. The defects were the filled with 1 cc of autogenous bone, MBCP+TM (MBCP), HA30, HA70, and left empty (negative group). The new bone formations, residual material particles and bone‐to‐graft contacts were analyzed at 4, 8, 12 and 16 weeks.

Results

Fabricated BCP showed well‐distributed porosity. At 16 weeks, new bone formations were 45.26% (autogenous), 33.52% (MBCP), 24.34% (HA30), 19.43% (HA70) and 3.37% (negative). Residual material particles were 1.88% (autogenous), 17.58% (MBCP), 26.74% (HA30) and 37.03% (HA70). These values were not significant differences (Bonferroni correction <0.005). Bone‐to‐graft contacts were 73.68% (MBCP), which was significantly higher than 41.68% (HA30) and 14.32% (HA70; Bonferroni correction <0.017).

Conclusions

Polymeric sponge technique offers well‐distributed porosity. The new bone formation and residual material particles were comparable to MBCP+TM, but the bone‐to‐graft contact was lower than MBCP+TM.

Evaluation of the effect of a gamma irradiated DBM-pluronic F127 composite on bone regeneration in Wistar rat

Demineralized bone matrix (DBM) is widely used for bone regeneration. Since DBM is prepared in powder form its handling properties are not optimal and limit the clinical use of this material. Various synthetic and biological carriers have been used to enhance the DBM handling. In this study we evaluated the effect of gamma irradiation on the physical-chemical properties of Pluronic and on bone morphogenetic proteins (BMPs) amount in DBM samples. In vivo studies were carried out to investigate the effect on bone regeneration of a gamma irradiated DBM-Pluronic F127 (DBM-PF127) composite implanted in the femur of rats. Gamma irradiation effects (25 kGy) on physical-chemical properties of Pluronic F127 were investigated by rheological and infrared analysis. The BMP-2/BMP-7 amount after DBM irradiation was evaluated by ELISA. Bone regeneration capacity of DBM-PF127 containing 40% (w/w) of DBM was investigated in transcortical holes created in the femoral diaphysis of Wistar rat. Bone porosity, repaired bone volume and tissue organization were evaluated at 15, 30 and 90 days by Micro-CT and histological analysis. The results showed that gamma irradiation did not induce significant modification on physical-chemical properties of Pluronic, while a decrease in BMP-2/BMP-7 amount was evidenced in sterilized DBM. Micro-CT and histological evaluation at day 15 post-implantation revealed an interconnected trabeculae network in medullar cavity and cellular infiltration and vascularization of DBM-PF127 residue. In contrast a large rate of not connected trabeculae was observed in Pluronic filled and unfilled defects. At 30 and 90 days the DBM-PF127 samples shown comparable results in term of density and thickness of the new formed tissue respect to unfilled defect. In conclusion a gamma irradiated DBM-PF127 composite, although it may have undergone a significant decrease in the concentration of BMPs, was able to maintains bone regeneration capability.

Enhanced bone regeneration with a novel synthetic bone substitute in combination with a new natural cross-linked collagen membrane: radiographic and histomorphometric study

OBJECTIVES

4Bone is a fully synthetic bioactive bone substitute composed of 60% hydroxyapatite (HA) and 40% beta-tricalcium phosphate (ß-TCP). This study aimed to investigate the effect of resorbable collagen membranes (RCM) on critical size defects in rabbit tibiae filled with this novel biphasic calcium phosphate at 15, 30, 45, and 60 days by radiological and histomorphometric analysis.

MATERIAL AND METHODS

Three critical size defects of 6 mm diameter were created in both tibiae of 20 New Zealand rabbits and divided into three groups according to the filling material: Group A (4Bone), Group B (4Bone plus RCM), and Group C (unfilled control group). At each of the four study periods, five rabbits were sacrificed. Anteroposterior and lateral radiographs were taken. Samples were processed for observation under light microscopy.

RESULTS

At the end of treatment, radiological analysis found that cortical defect closure was greater in Group B than Group A, and radiopacity was clearly lower and more heterogeneous in Group A cortical defects than in Group B. There was no cortical defect closure in Group C. Histomorphometric evaluation showed significant differences in newly formed bone and cortical closure in Group B compared with Groups A and C, with the presence of higher density newly formed bone in cortical and medullar zones.

CONCLUSIONS

Biphasic calcium phosphate functioned well as a scaffolding material allowing bone ingrowth and mineralization. The addition of absorbable collagen membranes enhanced bone gain compared with non-membrane-treated sites. This rabbit study provides radiological and histological evidence confirming the suitability of this new material for guided tissue regeneration of critical defects.

Sequential identification of a degradable phosphate glass scaffold for skeletal muscle regeneration

Tissue engineering has the potential to overcome limitations associated with current management of skeletal muscle defects. This study aimed to sequentially identify a degradable phosphate glass scaffold for the restoration of muscle defects. A series of glass compositions were investigated for the potential to promote bacterial growth. Thereafter, the response of human craniofacial muscle-derived cells was determined. Glass compositions containing Fe4- and 5 mol% did not promote greater Staphylococcus aureus and Staphylococcus epidermidis growth compared to the control (p > 0.05). Following confirmation of myogenicity, further studies assessed the biocompatibility of glasses containing Fe5 mol%. Cells seeded on collagen-coated disks demonstrated comparable cellular metabolic activity to control. Upregulation of genes encoding for myogenic regulatory factors (MRFs) confirmed myofibre formation and there was expression of developmental MYH genes. The use of 3-D aligned fibre scaffolds supported unidirectional cell alignment and upregulation of MRF and developmental MYH genes. Compared to the 2-D disks, there was also expression of MYH2 and MYH7 genes, indicating further myofibre maturation on the 3-D scaffolds and confirming the importance of key biophysical cues.

Biodegradation and in vivo biocompatibility of a degradable, polar/hydrophobic/ionic polyurethane for tissue engineering applications

A degradable, polar/hydrophobic/ionic polyurethane (D-PHI) scaffold was optimized in in vitro studies to yield mechanical properties appropriate to replicate vascular graft tissue while eliciting a more wound-healing phenotype macrophage when compared to established materials. The objectives of this study were to characterize the biodegradation (in vitro and in vivo) and assess the in vivo biocompatibility of D-PHI, comparing it to a well-established, commercially-available scaffold biomaterial, polylactic glycolic acid (PLGA), recognized as being degradable, non-cytotoxic, and showing good biocompatibility. PLGA and D-PHI were formed into 6 mm diameter disk-shaped scaffolds (2 mm thick) of similar porosity (∼82%) and implanted subcutaneously in rats. Both PLGA and D-PHI scaffolds were well-tolerated at the 7 d time point in vivo. In vitro D-PHI scaffolds degraded slowly (only 12 wt% in PBS in vitro after 120 d at 37 °C). In vivo, D-PHI scaffolds degraded at a more controlled rate (7 wt% loss over the acute 7 d implant phase and subsequently a linear profile of degradation leading to a 21 wt% mass loss by 100 d (chronic period)) than PLGA scaffolds which showed an initial more rapid degradation (14 wt% over 7 d), followed by minimal change between 7 and 30 d, and then a very rapid breakdown of the scaffold over the next 60 d. Histological examination of D-PHI scaffolds showed tissue ingrowth into the pores increased with time whereas PLGA scaffolds excluded cells/tissue from its porous structure as it degraded. The results of this study suggest that D-PHI has promising qualities for use as an elastomeric scaffold material for soft TE applications yielding well integrated tissue within the scaffold and a controlled rate of degradation stabilizing the form and shape of the implant.