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Bone tissue is a nanocomposite consisting of an organic and inorganic matrix, in which the collagen component and the mineral phase are organized into complex and porous structures. Hydroxyapatite (HA) is the most used ceramic biomaterial since it mimics the mineral composition of the bone in vertebrates. However, this biomimetic material has poor mechanical properties, such as low tensile and compressive strength, which make it not suitable for bone tissue engineering (BTE). For this reason, HA is often used in combination with different polymers and crosslinkers in the form of composites to improve their mechanical properties and the overall performance of the implantable biomaterials developed for orthopedic applications. This review summarizes recent advances in HA-based biocomposites for bone regeneration, addressing the most widely employed inorganic matrices, the natural and synthetic polymers used as reinforcing components, and the crosslinkers added to improve the mechanical properties of the scaffolds. Besides presenting the main physical and chemical methods in tissue engineering applications, this survey shows that HA biocomposites are generally biocompatible, as per most in vitro and in vivo studies involving animal models and that the results of clinical studies on humans sometimes remain controversial. We believe this review will be helpful as introductory information for scientists studying HA materials in the biomedical field.

Hydroxyapatite (HA) bioceramic scaffolds were fabricated by using digital light processing (DLP) based additive manufacturing. Key issues on the HA bioceramic scaffolds, including dispersion, DLP fabrication, sintering, mechanical properties, and biocompatibility were discussed in detail. Firstly, the effects of dispersant dosage, solid loading, and sintering temperature were studied. The optimal dispersant dosage, solid loading, and sintering temperature were 2 wt%, 50 vol%, and 1250 °C, respectively. Then, the mechanical properties and biocompatibility of the HA bioceramic scaffolds were investigated. The DLP-prepared porous HA bioceramic scaffold was found to exhibit excellent mechanical properties and degradation behavior. From this study, DLP technique shows good potential for manufacturing HA bioceramic scaffolds.

Objective: Root canals treated with bioceramic sealers that need retreatment present a clinical challenge. The presented study assessed 20% citric acid (with and without activation) in removing bioceramic sealer remnants. Material and Methods: Thirty extracted human lower premolars teeth were obturated with gutta-percha using bioceramic sealer, and have been split into three groups, each consisting of ten teeth: (1) 20% citric acid without activation, (2) 20% citric acid with ultrasonic activation, and (3) control group utilizing ProTaper Universal retreatment files exclusively. A scanning electron microscope (SEM) was used to investigate the remaining sealer remnants at the coronal, middle and apical thirds. The percentage of the uncleaned canal areas was determined quantitatively with the use of ImageJ software. Results: One-Way ANOVA had shown a significant difference between groups (p less than 0.001). At 64.8% ± 3.1, the control group had the greatest mean residual debris. While ultrasonic activation further improved cleaning efficacy (44.0% 2.6), irrigation with citric acid greatly reduced remnants (50.8% 4.9). Applying ultrasonic activation had the biggest cleaning impact in the apical third. In the apical third, the lowest debris was observed in the activation group (41.1% ± 0.9) vs. 45.3% (citric alone) and 65.7% (control). In the middle third, respective values were 44.1%, 51.5%, and 64.1%. In the coronal third, results were 64.8%, 55.5%, and 64.5%, respectively. Conclusion: According to our results, citric acid irrigation significantly enhances the removal of bioceramic sealer remnants from root canal walls, particularly when combined with ultrasonic activation. Compared to mechanical retreatment alone, the combination of chemical irrigation and activation resulted in a greater reduction of residual material. Citric acid significantly enhances the removal of bioceramic sealer remnants, particularly in the middle and apical thirds. Ultrasonic activation further improves efficacy, with the apical third showing the most notable improvement (41.1% vs. 65.7% in control). This protocol demonstrates a clinically effective and practical approach to improving the efficiency of endodontic retreatment procedures.

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.

The repair of large cranial defects with bone is a major clinical challenge that necessitates novel materials and engineering solutions. Three-dimensionally (3D) printed bioceramic (BioCer) implants consisting of additively manufactured titanium frames enveloped with CaP BioCer or titanium control implants with similar designs were implanted in the ovine skull and at s.c. sites and retrieved after 12 and 3 mo, respectively. Samples were collected for morphological, ultrastructural, and compositional analyses using histology, electron microscopy, and Raman spectroscopy. Here, we show that BioCer implants provide osteoinductive and microarchitectural cues that promote in situ bone regeneration at locations distant from existing host bone, whereas bone regeneration with inert titanium implants was confined to ingrowth from the defect boundaries. The BioCer implant promoted bone regeneration at nonosseous sites, and bone bonding to the implant was demonstrated at the ultrastructural level. BioCer transformed to carbonated apatite in vivo, and the regenerated bone displayed a molecular composition indistinguishable from that of native bone. Proof-of-principle that this approach may represent a shift from mere reconstruction to in situ regeneration was provided by a retrieved human specimen, showing that the BioCer was transformed into well-vascularized osteonal bone, with a morphology, ultrastructure, and composition similar to those of native human skull bone.

Radiopacity is an essential physical property to measure the quality of the filling, and whether the association of bioceramic sealers with gutta-percha cones increases the radiopacity of the filling was not previously assessed. Material and methods: Sixty transparent resin blocks with simulated root canals were prepared and X-rayed with a gutta-percha cone. The blocks were divided into five groups and filled with the single-cone technique using AH Plus (Dentsply Sirona, Ballaigues, Switzerland), AH Plus Bioceramic (Dentsply Sirona, Ballaigues, Switzerland), Bio-C Sealer (Angelus, Londrina, Brazil), BioRoot RCS (Septodont, Saint Maur-des[1]Fosses, France), or Sealer Plus BC (MK Life, Porto Alegre, Brazil). New radiographs were taken, and the images were analyzed using the Adobe Photoshop software (Adobe Systems Inc., San Jose, USA). Results: There was no difference (p>0.05) in the radiopacity of the gutta-percha cones used in the five groups. The epoxy resin-based AH Plus and AH Plus Bioceramic showed the highest increase in radiopacity (p<0.05). Sealer Plus BC, BioRoot RCS, and Bio-C Sealer showed similar radiopacity y (p<0.05). Conclusion: All sealers showed increased radiopacity (p<0.05) when associated with the gutta-percha cone.

Successful materials design for bone-tissue engineering requires an understanding of the composition and structure of native bone tissue, as well as appropriate selection of biomimetic natural or tunable synthetic materials (biomaterials), such as polymers, bioceramics, metals and composites. Scalable fabrication technologies that enable control over construct architecture at multiple length scales, including three-dimensional printing and electric-field-assisted techniques, can then be employed to process these biomaterials into suitable forms for bone-tissue engineering. In this Review, we provide an overview of materials-design considerations for bone-tissue-engineering applications in both disease modelling and treatment of injuries and disease in humans. We outline the materials-design pathway from implementation strategy through selection of materials and fabrication methods to evaluation. Finally, we discuss unmet needs and current challenges in the development of ideal materials for bone-tissue regeneration and highlight emerging strategies in the field. Design of bone-tissue-engineering materials involves consideration of multiple, often conflicting, requirements. This Review discusses these considerations and highlights scalable technologies that can fabricate natural and synthetic biomaterials (polymers, bioceramics, metals and composites) into forms suitable for bone-tissue-engineering applications in human therapies and disease models.

Tissue engineering is approach of replacing or regeneration of biological functions of tissues or organs by using combination of biomaterials, biomolecules and cells. Tissue engineering mainly depends scaffold biomaterials and scaffold fabrication methods. Therefore, there have been progressive investigation and development of new biomaterials with different formulations to help and achieve necessary requirements in the tissue engineering applications. This review is briefly representing necessary features associated with biomaterial type and design required for tissue regeneration applications, and presenting earlier research in tissue engineering field and new trends for future implementation. It is mainly focusing on generations of biomaterials and discovery tissue engineering field. As well as, different types of biomaterials, such as bioceramics, bioactive glasses, synthetic and natural polymers and their derived composites, used in fabrication of scaffolds (as a main part of tissue engineering) are demonstrated in this review. Scaffold fabrication methods are also reviewed here. Moreover, it is showing the recent achievements in tissue engineering field for bone, skin, cartilage, neural, and cardiac regeneration as a pre-clinical procedure for repair of injured and diseased tissues and organs. Finally, recent trends and challenges of biomaterials for tissue regeneration are presented also in this review. Graphical abstract

Synthetic biopolymers are effective cues to replace damaged tissue in the tissue engineering (TE) field, both for in vitro and in vivo application. Among them, poly-l-lactic acid (PLLA) has been highlighted as a biomaterial with tunable mechanical properties and biodegradability that allows for the fabrication of porous scaffolds with different micro/nanostructures via various approaches. In this review, we discuss the structure of PLLA, its main properties, and the most recent advances in overcoming its hydrophobic, synthetic nature, which limits biological signaling and protein absorption. With this aim, PLLA-based scaffolds can be exposed to surface modification or combined with other biomaterials, such as natural or synthetic polymers and bioceramics. Further, various fabrication technologies, such as phase separation, electrospinning, and 3D printing, of PLLA-based scaffolds are scrutinized along with the in vitro and in vivo applications employed in various tissue repair strategies. Overall, this review focuses on the properties and applications of PLLA in the TE field, finally affording an insight into future directions and challenges to address an effective improvement of scaffold properties.

Hydroxyapatite (HA), the principal mineral of bone tissue, can be fabricated as an artificial calcium phosphate (CaP) ceramic and potentially used as bioceramic material for bone defect treatment. Nevertheless, the production method (including the applied sintering temperature) of synthetic hydroxyapatite directly affects its basic properties, such as its microstructure, mechanical parameters, bioabsorbability, and osteoconductivity, and in turn influences its biomedical potential as an implantable biomaterial. The wide application of HA in regenerative medicine makes it necessary to explain the validity of the selection of the sintering temperature. The main emphasis of this article is on the description and summarization of the key features of HA depending on the applied sintering temperature during the synthesis process. The review is mainly focused on the dependence between the HA sintering temperature and its microstructural features, mechanical properties, biodegradability/bioabsorbability, bioactivity, and biocompatibility.