Papers by Keyword: Bone

Abstract: Coral reefs face significant damage from factors such as climate change, pollution, and careless tourism. Although vertebrates and corals differ in substance, their skeletal formation mechanisms are very similar. Titanium (Ti) and its alloys are widely utilised as biomedical materials for orthopaedic and dental implants due to their excellent mechanical properties, biocompatibility, and corrosion resistance. Various surface modifications have been developed to enhance cell adhesion and bone formation. This study aimed to investigate polyp adhesion and skeletal formation on Ti nonwoven materials after chemical surface modifications. Polyps were isolated by increasing the salinity of artificial seawater (viesalt, MARINETECH) in which coral fragments were immersed. Ti nonwoven fabric was anodised. The polyp adhered to the substrate on Day1 and expanded along the fibres over a period of about Day15. The moderate roughness and the oxide film formed on the surface improved the wettability of the substrate.

Abstract: In the context of this numerical study is particularly to analyze and observe the effect of mechanical properties and masticatory efforts on the intensity and distribution of biomechanical stresses induced in the mandibular bone (the cortical bone, the spongy bone) and in the elements which constitute the structure of the dental bridge (abutments, implants, bridge). The 3D model studied is subjected to loading in the three directions of space (corrono-apical, disto-medial, bucolingual). The numerical analysis allowed us to highlight the localization of the stress concentration zones, on the one hand, at the level of the regions of contact between the elements of the dental bridge structure and on the other hand, at the level of the mandibular bone. This parametric approach for the mechanical properties of bridges is used to better visualize and quantify the biomechanical behavior of dental bridges.

Abstract: The need to develop surviving implants and bone substitutes with good biocompatibility, mechanical strength and bioactivity, without causing toxicity, immune rejection and cancer had attracted the attention of many researchers over the years. Hydroxyapatite (HA) is one of the excellent calcium phosphates and major mineral component of vertebrate bone and teeth, which considerably enhances the biocompatibility, mechanical strength and bioactivity of artificial biomaterials in the body system. In addition, it creates porous and rough coated surface that aids the cell attachment, proliferation and the growth of tissue on the bone implants. Due to its high demand in biomedical applications, scientists had developed several, simple and efficient techniques to produce HA. This review outlines several techniques of manufacturing HA and summarizes the merits and demerits of each technique. Keywords: Biomaterials, calcium phosphate, hydroxyapatite, preparation techniques and bone

Abstract: Estimated 30 percent or more of coral reefs are now in danger of extinction by coastal construction increases and global temperatures rise. Several restoration techniques such as fragmentation, forming, Biorock have been developed in the past few years. In vertebrates such as mammals, osteoblast is known to form the bones composed of hydroxyapatite. Therefore, bone substitutional devices are generally surface modified to improve the adhesion of osteoblasts on the surfaces. Titanium dioxide film is often employed as the surface material for hard tissue substitutes made of titanium and its alloys. In hard corals, on the other hand, the soft tissue covered on the skeletons made of calcium carbonate has osteoblasts as well. The purpose of this work was to investigate the potential of titanium (Ti) and titanium dioxide (TiO₂) as scaffolds for proliferating coral reefs by analysing the several interfacial reactions. The rods of pure Ti were anodised in aqueous phosphoric acid at a constant voltage of 80 V. The surfaces were confirmed to be anatase type TiO₂. The coral fragments were kept in contact with the rods in a lab-scale aquarium with artificial seawater for several days. The colony of polyps vigorously expanded on the surfaces. Fragments of coral were placed on pure Ti, TiO₂ coated pure Ti in Petri dishes and were reared in artificial seawater. Fine spherical precipitates of calcium carbonate with aragonite structure, which is the same inorganic substance as corals, were observed radially and regularly on the surfaces of TiO₂. In addition, the adherence of planula larva to the sputtered TiO₂ film was observed by using a QCM (Quartz Crystal Microbalance) method. The approach and adhesion of planula larva to the surface could be detected by monitoring the resonance frequency and resistance. The surfaces might have a great potential in coral reef regenerations.

Abstract: Biomaterials can be used in several areas of regenerative bioengineering, and is a viable option in the repair of bone injuries. A number of different types of biomaterials have been studied in relation to bone repair. Ceramics such as α-TCP have low fracture toughness compared to natural bone, so reinforcements such as wollastonite whiskers are developed so that they can be used in places with greater overload. This study aimed to evaluate the biocompatibility and bone neoformation of α-TCP plus 10% wollastonite whiskers, in vivo. To obtain the cement, α-TCP powders with or without 10% wollastonite whiskers were added to an aqueous solution containing 2.5% by weight of Na2HPO4 (anhydrous bibasic sodium phosphate). The biomaterial then became a paste, which was molded into the critical 5 mm defect made in the parietal bone of Wistar rats. Ten rats were divided into two groups. The animals from each group were euthanized within 30 days. Calvaries were removed and subjected to histological processing with Eosin and Hematoxylin. The implementation of the whisker biomaterial revealed the formation of intensely vascularized connective tissue in the implemented region; however, animals with the biomaterial α-TCP showed the formation of this tissue around the implemented region. On the other hand, intense bone resorption was observed only in the animals with Wollastonite Whiskers, but new bone formation in both groups. The biomaterial evaluated was shown to be non-cytotoxic, resorbable, and capable of inducing bone neoformation; however, more studies should be carried out to assess the application of this biomaterial in bone injuries.

Abstract: Background: Hydroxyapatite (HAP), as a common biomaterial in bone tissue engineering, can be fabricated in combination with other osteogenic agents. Pentoxifylline (PTX) is demonstrated to have positive roles in bone defect healing. Since local administration can diminish the systemic side effects of the drug, the objectives of the current in vitro study were to find the effects of PTX on the osteoblast functions for tissue engineering applications. Methods: a HAP scaffold was fabricated by casting the HAP slurry within polyurethane foam. The scaffold was enriched with 5 mg/mL PTX. Alginate (Alg) was used as drug carrier to regulate the PTX releasing rate. MG-63 osteosarcoma cells were cultured on 3D scaffolds and 2D Alg films in the presence or absence of PTX. Results: PTX did not affect the cell viability, attachment and phenotype. Also, the ultrastructure of the scaffolds was not modified by PTX enrichment. Alizarin red S staining showed that PTX has no effect on calcium deposition. Besides, Raman confocal microscopy demonstrated an increase in the organic matrix formation including proline, valine and phenylalanine deposition (represented collagen). Although PTX increased the total protein secretion, it led to a decrease in the alkaline phosphatase activity and vascular endothelial growth factor (VEGF) content. PTX reduced the hydration and degradation rates and it was released mainly at the first 24 hours of incubation. Conclusion: Based on our in vitro study, application of engineered PTX-loaded HAP scaffold in bone regeneration can act on behalf of organic matrix production, but not angiogenesis and mineralization.

Abstract: Bone is a rigid and constantly remodeling organ, a type of tissue which provides support and protects organs in the body, and together they form the skeleton [1]. Materials generally used for implants bear tissue rejection and produce toxins on degradation [2]. Our objective is to synthesize a biocompatible composite of Hydroxyapatite (HA) and Cellulose using Cellulose Acetate as a matrix which mimics the properties of natural bone that can be used for bone replacements. Bone is composed of calcium phosphate (HA) and collagen, which gives bone desired properties [3]. Hydroxyapatite is the inorganic mineral found in the bone and is preferred due to its mechanical properties, biocompatibility, slow degradation in physiological environment and bioactivity [4]. Cellulose, structural component in plants is similar in properties to collagen therefore the properties of cellulose [4], HA and cellulose acetate are exploited to achieve our results. The experimental procedure is divided into two major steps; extraction of cellulose microfibers (CMF) from cotton followed by dispersion of cellulose and HA in cellulose acetate then casting membranes of the composite.

Abstract: The number of supporting dental implants is an important criterion for the surgical outcome of dental bridge fixation, which has considerable impact on biomechanical load transfer characteristics. Excessive stress at the bone–implant interface by masticatory loading may result in implant failure. The aim of this study was to evaluate the impact of the number of implants supporting the dental bridge on stress in neighboring tissues around the implants. Results of the study will provide useful information on appropriate surgical techniques for dental bridge fixation. In this study, osseointegrated smooth cylindrical dental implants of same diameter and length were numerically analyzed, using three-dimensional bone–implant models. The effect of the number of supporting implants on biomechanical stability of dental bridge was examined, using two, three and four supporting implants. All materials were assumed to be linearly elastic and isotropic. Masticatory load was applied in coron-apical direction on the external part of dental bridge. Finite Element (FE) analyses were run to solve for von Mises stress. Maximum von Mises stresses were located in the cervical line of cortical bone around dental implants. Peak von Mises stress values decreased with an increase in the number of implants that support the dental bridge. Results of this study demonstrate the importance of using the correct number of supporting implants to for dental bridge fixation.

Abstract: Composite hydrogels on the basis of hydroxyapatite (HAp) and polyvinyl alcohol (PVA) has been proposed as a promising materials for bone and cartilage tissue engineering. HAp/PVA composite hydrogels with phase ratio 50:50wt% and 70:30wt% were obtained via in situ wet chemical precipitation technique in combination with the freeze-thawing approach. The XRD studies of sintered products revealed that HAp/PVA composite hydrogels synthesized from PVA with degree of hydrolysis (DH) 98% and molecular weights (MW) 25 kDa and 78 kDa are more suitable for biomedical purposes due to the formation of stoichiometric HAp. Swelling studies indicated that HAp/PVA 50:50 (78 kDa, 88% and 98%) hydrogels after 24h of immersion swell ~4.25-6.5 times less than identical samples with phase composition of 70:30wt%, which is accounted to different number of intermolecular hydrogen bonds formed. After 16 subsequent freeze-thawing cycles (FTC), HAp/PVA 50:50 (78 kDa, 88% and 98%) hydrogels contain ~1.2 times higher content of crosslinked PVA than HAp/PVA 70:30 (78 kDa, 88% and 98%) hydrogel samples.

Abstract: Two different approaches are proposed in this study to enhance the bioactivity of hydroxyapatite-based scaffolds for bone tissue regeneration. The first method consists in a structural modification of Hydroxyapatite (HA) through doping it with Magnesium (1,3% wt) while the second one in using HA in combination with a calcium silicate, i.e. Wollastonite (WS), to form a composite bioceramic. Scaffolds with high and strongly interconnected porosity (pores ranging from 300 to 800 µm) were produced throughout both procedures. Higher mechanical properties in compression were obtained when the composite Ws/HA bioceramic was adopted. That one showed a weight loss after 6 months in physiological solution seven times higher than doped HA. Preliminary in vitro tests highlighted that both kinds of scaffold allowed the adhesion of MG63, without significant differences in terms of vitality, indicating a good biocompatibility of both used biomaterials.