Limitations and modifications in the clinical application of calcium sulfate

Calcium sulfate and calcium sulfate-based biomaterials have been widely used in non-load-bearing bone defects for hundreds of years due to their superior biocompatibility, biodegradability, and non-toxicity. However, lower compressive strength and rapid degradation rate are the main limitations in clinical applications. Excessive absorption causes a sharp increase in sulfate ion and calcium ion concentrations around the bone defect site, resulting in delayed wound healing and hypercalcemia. In addition, the space between calcium sulfate and the host bone, resulting from excessively rapid absorption, has adverse effects on bone healing or fusion techniques. This issue has been recognized and addressed. The lack of sufficient mechanical strength makes it challenging to use calcium sulfate and calcium sulfate-based biomaterials in load-bearing areas. To overcome these defects, the introduction of various inorganic additives, such as calcium carbonate, calcium phosphate, and calcium silicate, into calcium sulfate is an effective measure. Inorganic materials with different physical and chemical properties can greatly improve the properties of calcium sulfate composites. For example, the hydrolysis products of calcium carbonate are alkaline substances that can buffer the acidic environment caused by the degradation of calcium sulfate; calcium phosphate has poor degradation, which can effectively avoid the excessive absorption of calcium sulfate; and calcium silicate can promote the compressive strength and stimulate new bone formation. The purpose of this review is to review the poor properties of calcium sulfate and its complications in clinical application and to explore the effect of various inorganic additives on the physicochemical properties and biological properties of calcium sulfate.

Oriented attachment and aggregation as a viable pathway to self-assembled organic/inorganic hybrid materials

The intrinsic particle-based mechanisms of calcium sulfate crystallisation are exploited to incorporate specific organic polymers in the emerging mineral phase and thus obtain biomimetic organic/inorganic hybrid structures via self-organisation.

In vivo bioresorbability and bone formation ability of sintered highly pure calcium carbonate granules

Calcium carbonate-based bone substitutes derived from natural coral exoskeleton (aragonite) are resorbed and remodeled faster than calcium phosphate-based substitutes. However, coral species with structures appropriate for use as bone substitutes are very limited. Therefore, it is important to evaluate potential of artificial calcium carbonate ceramics as a bone substitute. In this study, calcium carbonate granules with various porosities and pore sizes were prepared by sintering a highly pure (>99.98%) calcium carbonate powder (calcite), and their resorption properties and bone formation abilities were examined in vivo for the first time. The sintered calcium carbonate was resorbed faster than β-tricalcium phosphate, which has a similar structure. However, sintered calcium carbonate did not promote new bone formation during long-term implantation. Furthermore, both resorption and new bone formation were affected by the pore structure. The optimal structures of the artificially sintered calcium carbonate bone substitute were also discussed.

Dual role of tannic acid and pyrogallol incorporated in plaster of Paris: Morphology modification and release for antimicrobial properties

The design of bioactive plasters is of major interest for the amelioration of dental and bone cements. In this article, a one pot and environmentally friendly strategy based on the addition of a cheap polyphenol-tannic acid (TA) or the main phenolic constituent of TA, namely pyrogallol (PY)- able to interact with calcium sulfate is proposed. Tannic acid and pyrogallol not only modify the morphology of the obtained plaster+TA/PY composites but a part of it is released and provides strong-up to twenty fold- antibacterial effect against Staphylococcus aureus. It is shown that the higher antibacterial efficiency of PY is related to a greater release compared to TA even if in solution the antibacterial effect of PY is lower than that of TA when reported on the basis of the molar concentration in PY units.

Effect of Dehydrothermal Treatment on the Mechanical Properties and Biocompatibility of Plaster of Paris–CaCO3 Hydrogel Loaded With Cinnamaldehyde for Biomedical Purposes

CaCO3 hydrogel incorporation into Plaster of Paris (POP) formulations decreased the resorption rate of the POP after implantation in the body. Although an inflammatory process is required as part of wound healing, the accumulation and activation of inflammatory cells in the POP–hydrogel CaCO3 implant area needs to be controlled. Therefore, cinnamaldehyde, as an anti-inflammatory agent with a unique α, β-unsaturated aldehyde, was incorporated into the CaCO3 hydrogel. During the incorporation, both the lipophilic and hydrophilic sides of the cinnamaldehyde molecule can influence the physical and mechanical properties of the CaCO3 hydrogel, in which mechanical properties of a tissue engineering scaffold are important to fine tune cellular activity during implantation. On the other hand, as a 3-dimensional polymeric structure, crosslinking is needed for the CaCO3 hydrogel to stabilize and increase its molecular weight for better mechanical strength, and more resistance to heat, wear, and solvent attack. For that purpose, dehydrothermal treatment (DHT) was applied to the crosslink hydrogel system as a favorable crosslinking method to avoid the use of a chemical agent. In this study, 3 groups of hydrogels of CaCO3, namely DHT crosslinked, loaded with cinnamaldehyde, and loaded with cinnamaldehyde followed by DHT crosslinking were developed before being combined with POP in 50 wt%. To evaluate the effect of DHT to the final POP-cinnamaldehyde-loaded CaCO3 hydrogel properties and biocompatibility, scanning electron microscopy, contact angle, surface roughness, hardness, diametral tensile strength, and in vivo biocompatibility studies were conducted. It was observed that cinnamaldehyde with DHT treatment improved the POP–hydrogel CaCO3 properties and had good biocompatibility. Thus, POP-cinnamaldehyde-loaded CaCO3 hydrogel can be a promising bone substitute containing an anti-inflammatory agent.

Bioceramics for Clinical Application in Regenerative Dentistry

Bioceramics represent functional ceramics with significant interest in regenerative medicine area. In orthopedics as well as in oral and maxillofacial surgery, bioceramics have been widely used as bone reconstructive materials. The most common one is hydroxyapatite which have been in the market and clinical applications since the mid of 1970s. Nowadays, a lot of works have been being in the pipeline to develop bioceramics for various clinical applications in regenerative medicine area, including dentistry. Bioceramics have been used and considered promising candidate for periodontal treatment, prevention of relapse, nerve regeneration, vaccine adjuvant, drug delivery technology, even for esthetic medicine and cosmetics. In this chapter, the advantages of bioceramics for regenerative therapy especially in dentistry is discussed. The overview of bioceramics classification is also explained. The future perspective and challenges on the use of bioceramics for next generation regenerative therapy is also discussed.

Analysis of the Osteogenic Effects of Biomaterials Using Numerical Simulation

We describe the development of an optimization algorithm for determining the effects of different properties of implanted biomaterials on bone growth, based on the finite element method and bone self-optimization theory. The rate of osteogenesis and the bone density distribution of the implanted biomaterials were quantitatively analyzed. Using the proposed algorithm, a femur with implanted biodegradable biomaterials was simulated, and the osteogenic effects of different materials were measured. Simulation experiments mainly considered variations in the elastic modulus (20–3000 MPa) and degradation period (10, 20, and 30 days) for the implanted biodegradable biomaterials. Based on our algorithm, the osteogenic effects of the materials were optimal when the elastic modulus was 1000 MPa and the degradation period was 20 days. The simulation results for the metaphyseal bone of the left femur were compared with micro-CT images from rats with defective femurs, which demonstrated the effectiveness of the algorithm. The proposed method was effective for optimization of the bone structure and is expected to have applications in matching appropriate bones and biomaterials. These results provide important insights into the development of implanted biomaterials for both clinical medicine and materials science.

Simple and economic elaboration of high purity CaCO3 particles for bone graft applications using a spray pyrolysis technique

CaCO₃ particles obtained using spray pyrolysis possess all the requirements to constitute promising multi-purpose materials for bone graft applications.

Synchronization of calcium sulphate cement degradation and new bone formation is improved by external mechanical regulation

A major challenge faced in the bone materials of weight-bearing without internal fixture support is the mismatch of material degradation and new bone formation, leading to weakening or even failure of the overall bony structure. This study demonstrated in the rat femur model that calcium sulphate cement degradation and new bone formation could be better synchronized by external mechanical force. An ascending force in line with calcium sulphate cement degradation could achieve bone healing in 37 days with ultimate load to failure of 87.00 ± 7.30 N, similar to that of intact femur (80.46 ± 2.79 N, p = 0.369). In contrast, the healing process under either a constant force or no force illustrated significant residual defect volumes of 1.47 ± 0.44 and 4.08 ± 0.89 mm(3) (p < 0.001), and weaker ultimate loads to failure of 69.56 ± 4.74 and 59.17 ± 7.48 N, respectively (p < 0.001). Our results suggest that the mechanical regulation approach deserves further investigation and may potentially offer a clinical strategy to improve synchronization.

Chlamydia caviae infection alters abundance but not composition of the guinea pig vaginal microbiota

In humans, the vaginal microbiota is thought to be the first line of defense again pathogens including Chlamydia trachomatis. The guinea pig has been extensively used as a model to study chlamydial infection because it shares anatomical and physiological similarities with humans, such as a squamous vaginal epithelium as well as some of the long-term outcomes caused by chlamydial infection. In this study, we aimed to evaluate the guinea pig-C. caviae model of genital infection as a surrogate for studying the role of the vaginal microbiota in the early steps of C. trachomatis infection in humans. We used culture-independent molecular methods to characterize the relative and absolute abundance of bacterial phylotypes in the guinea pig vaginal microbiota in animals non-infected, mock-infected or infected by C. caviae. We showed that the guinea pig and human vaginal microbiotas are of different bacterial composition and abundance. Chlamydia caviae infection had a profound effect on the absolute abundance of bacterial phylotypes but not on the composition of the guinea pig vaginal microbiota. Our findings compromise the validity of the guinea pig-C. caviae model to study the role of the vaginal microbiota during the early steps of sexually transmitted infection.

The vaginal microbiota of the guinea pig differs from that of humans and cannot prevent chlamydial infections efficiently.

Mechanical force enhanced bony formation in defect implanted with calcium sulphate cement

To improve the osteogenic property of bone repairing materials and to accelerate bone healing are major tasks in bone biomaterials research. The objective of this study was to investigate if the mechanical force could be used to accelerate bone formation in a bony defect in vivo. The calcium sulfate cement was implanted into the left distal femoral epiphyses surgically in 16 rats. The half of rats were subjected to external mechanical force via treadmill exercise, the exercise started at day 7 postoperatively for 30 consecutive days and at a constant speed 8 m·min⁻¹ for 45 min·day⁻¹, while the rest served as a control. The rats were scanned four times longitudinally after surgery using microcomputed tomography and newly formed bone was evaluated. After sacrificing, the femurs had biomechanical test of three-point bending and histological analysis. The results showed that bone healing under mechanical force were better than the control with residual defect areas of 0.64±0.19 mm² and 1.78±0.39 mm² (P<0.001), and the ultimate loads to failure under mechanical force were 69.56±4.74 N, stronger than the control with ultimate loads to failure of 59.17±7.48 N (P=0.039). This suggests that the mechanical force might be used to improve new bone formation and potentially offer a clinical strategy to accelerate bone healing.

Electrical stimulation of human mesenchymal stem cells on biomineralized conducting polymers enhances their differentiation towards osteogenic outcomes

Tissue scaffolds allowing the behaviour of the cells that reside on them to be controlled are of particular interest for tissue engineering.