Influence of nano-hydroxyapatite coating implants on gene expression of osteogenic markers and micro-CT parameters. An in vivo study in diabetic rats

Clinical challenges in bone tissue engineering - A narrative review

Bone tissue engineering (BTE) has emerged as a promising approach to address large bone defects caused by trauma, infections, congenital malformations, and tumors. This review focuses on scaffold design, cell sources, growth factors, and vascularization strategies, highlighting their roles in developing effective treatments. We explore the complexities of balancing mechanical properties, porosity, and biocompatibility in scaffold materials, alongside optimizing mesenchymal stem cell delivery methods. The critical role of growth factors in bone regeneration and the need for controlled release systems are discussed. Vascularization remains a significant hurdle, with strategies such as angiogenic factors, co-culture systems, and bioprinting under investigation. Mechanical challenges, tissue responses, and inflammation management are examined, alongside gene therapy's potential for enhancing osteogenesis and angiogenesis via both viral and non-viral delivery methods. The review emphasizes the impact of patient-specific factors on bone healing outcomes and the importance of personalized approaches. Future directions are described, emphasizing the necessity of interdisciplinary cooperation to advance the field of BTE and convert laboratory results into clinically feasible solutions.

Survival analysis of dental implants placed in horizontally severely resorbed maxillae after reconstruction with xenogeneic graft: a case series

PURPOSE

To evaluate the survival rates of dental implants with a hybrid macrostructure and the surface biomimetically coated with nanohydroxyapatite, placed in horizontally atrophic maxillae previously submitted to the guided bone regeneration (GBR) procedure, associated with the use of a deproteinized bovine bone graft (DBB).

METHODS

Twenty-five patients who received 196 implants were involved in this study. First, these patients were submitted to GBR procedures and maxillary sinus lift, where DBB was used as the grafting material. The dental implants were placed after a minimum period of 6 months of the grafting procedures. The patients were followed up every six months and clinical/radiographic examinations were performed to assess the implants, using the following indicators as a reference: (1) Absence of mobility; (2) Absence of pain. Data about the age, surgery time, smoking status, implant size, and time between the grafting procedure and implant placement were correlated with implant failures.

RESULTS

Twelve implants failed, generating a survival rate of 94.23%. None of the variables analysed correlated with the implant failures.

CONCLUSION

Implants with a hybrid macrostructure and surface biomimetically coated with nanohydroxyapatite present good survival rates in horizontally atrophic maxillae grafted with DBB.

Biomedical Approach of Nanotechnology and Biological Risks: A Mini-Review

Nanotechnology has played a prominent role in biomedical engineering, offering innovative approaches to numerous treatments. Notable advances have been observed in the development of medical devices, contributing to the advancement of modern medicine. This article briefly discusses key applications of nanotechnology in tissue engineering, controlled drug release systems, biosensors and monitoring, and imaging and diagnosis. The particular emphasis on this theme will result in a better understanding, selection, and technical approach to nanomaterials for biomedical purposes, including biological risks, security, and biocompatibility criteria.

Hydroxyapatite coatings versus osseointegration in dental implants: A systematic review

STATEMENT OF PROBLEM

Knowledge of the effectiveness of hydroxyapatite coatings on the surface of titanium dental implants is lacking because of difficulties in standardizing their thickness, roughness, and effect on osseointegration. The selection of articles describing this coating in osseointegration will be of great relevance to implant dentistry.

PURPOSE

This systematic review aimed to answer the question, "How effective is hydroxyapatite on titanium surfaces for osseointegration?"

MATERIAL AND METHODS

The Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 guidelines were followed, and the protocol was registered on the international prospective register of systematic reviews (PROSPERO) database (CRD42023422601). The PubMed, Scopus, Web of Science, and Embase databases were searched, and articles were selected manually in 2 steps by 2 blinded investigators according to the previously selected eligibility criteria. The risk of bias was assessed using the systematic review center for laboratory animal experimentation (SYRCLE) tool.

RESULTS

Initially, 671 results were found. After analysis of eligibility criteria and full reading, 15 articles were included in the present review. Of these, 12 reported favorable osseointegration results for hydroxyapatite-coated surfaces, and 3 found no significant long-term difference between the coated and uncoated groups.

CONCLUSIONS

Hydroxyapatite surface treatment is effective in the osseointegration of titanium dental implants because it favors the absorption of proteins, adhesion, and proliferation of bone cells when obtained by methods that ensure proper adhesion. (J Prosthet Dent xxxx;xxx:xxx-xxx).

Nanohydroxyapatite in dentistry: A comprehensive review

Enamel, being the hardest and the highest mineralized tissue of the human body, contains nearly 96% inorganic components and 4% organic compounds and water. Dentin contains 65% inorganic components and 35% organic and water content. The translucency and white appearance of enamel are attributed to Hydroxyapatite (HA), which constitutes the major part of the inorganic component of dental hard tissue. With the advent of nanotechnology, the application of Nanohydroxyapatite (nHA) has piqued interest in dentistry due to its excellent mechanical, physical, and chemical properties. Compared to HA, nHA is found to have superior properties such as increased solubility, high surface energy and better biocompatibility. This is due to the morphological and structural similarity of nanosized hydroxyapatite particles to tooth hydroxyapatite crystals. These nanoparticles have been incorporated into various dental formulations for different applications to ensure comprehensive oral healthcare. To prevent dental caries, several nHA based dentifrices, mouth rinsing solutions and remineralizing pastes have been developed. nHA-based materials, such as nanocomposites, nano impression materials, and nanoceramics, have proven to be very effective in restoring tooth deformities (decay, fracture, and tooth loss). The nHA coating on the surface of the dental implant helps it bind to the bone by forming a biomimetic coating. A recent innovative strategy involves using nHA to reduce dentinal hypersensitivity and to reconstruct periodontal bone defects. The purpose of the present review is to discuss the different applications of nHA in dentistry, especially in preventive and restorative dentistry, dental implantology, bleaching and dentine hypersensitivity management.

Evaluation of Implant Surface Modification with Nanohydroxyapatite Associated with the Use of L-PRF: In Vivo Study in Rats

Leukocyte-platelet-rich fibrin (L-PRF) contains growth factors that stimulate bone regeneration. This study evaluated the bone repair in a tibia rat model around two implant surfaces in combination or not with L-PRF by assessing microtomographic and histomorphometric parameters. A total of 48 female rats were used in the study, in which 24 received implants with two types of surface treatments (dual acid etched-DAE or nanohydroxyapatite-nanoHA), and the other 24 received the same mini implants with L-PRF, which was collected by cardiac puncture, centrifugated, and inserted in the bone bed. The animals were euthanized 7 and 30 days after implant placement, and the retrieved samples were prepared for microtomographic and histomorphometric (bone-to-implant contact-BIC; and Bone Area Fraction Occupancy-BAFO) analyses. The adhesion of the nanoHA surface onto the implant surface was investigated by insertion and removal in simulated bone medium (Sawbones). The adhesion evaluation revealed that the loss of nanoHA after this procedure (as measured with SEM) from the implant surface was less than 1%. Overall, the nanoHA surface presented more bone in contact and in proximity to the implant, a higher bone surface/tissue volume fraction, a higher number of bone trabeculae, as well as trabecular separation relative to the DAE surface. Such results were more evident when the nanoHA surface was combined with L-PRF and after 30 days in vivo. The nanoHA surface presented higher BAFO when compared to DAE, with or without association with L-PRF. Therefore, implants with a nanoHA surface potentially benefit from the association to L-PRF.

Micro Computed Tomography and Immunohistochemistry Analysis of Dental Implant Osseointegration in Animal Experimental Model: A Scoping Review

Osseointegration is a complex process that involves the interaction of dental implants, bone, and the immune system. Preclinical testing was carried out to develop a better understanding of the mechanism. Micro-computed tomography (micro-CT) imaging techniques and immunohistochemistry are excellent tools for this objective as both enable quantitative assessment of bone microarchitecture and intercellular interaction. An extensive literature search was conducted using the databases PubMed, Science Direct, Wiley Online, Proquest and Ebscohost from January 2011 to January 2021. Among the publications retrieved, the rat model was the most frequently used experimental protocol, with the tibia being the most frequently implanted site. The region of interest demonstrates a high degree of homogeneity as measured by trabecula but varies in size and shape. The most frequently mentioned micro-CT bone parameter and immunohistochemistry bone markers were bone volume per total volume (BV/TV) and runt-related transcription factors (RUNX). Animal models, micro-CT analysis methods, and immunohistochemistry biomarkers yielded a variety of results in the studies. Understanding bone architecture and the remodeling process will aid in the selection of a viable model for a specific research topic.

Improving dental epithelial junction on dental implants with bioengineered peptides

Introduction: The functionalization of titanium (Ti) and titanium alloys (Ti6Al4V) implant surfaces via material-specific peptides influence host/biomaterial interaction. The impact of using peptides as molecular linkers between cells and implant material to improve keratinocyte adhesion is reported. Results: The metal binding peptides (MBP-1, MBP-2) SVSVGMKPSPRP and WDPPTLKRPVSP were selected via phage display and combined with laminin-5 or E-cadherin epithelial cell specific peptides (CSP-1, CSP-2) to engineer four metal-cell specific peptides (MCSPs). Single-cell force spectroscopy and cell adhesion experiments were performed to select the most promising candidate. In vivo tests using the dental implant for rats showed that the selected bi functional peptide not only enabled stable cell adhesion on the trans-gingival part of the dental implant but also arrested the unwanted apical migration of epithelial cells. Conclusion: The results demonstrated the outstanding performance of the bioengineered peptide in improving epithelial adhesion to Ti based implants and pointed towards promising new opportunities for applications in clinical practice.

Novel nano-hydroxyapatite coating of additively manufactured three-dimensional porous implants improves bone ingrowth and initial fixation

Electron beam melting (EBM) has been used to fabricate three-dimensional (3D) porous Ti-6Al-4V surfaces for acetabular cups in total hip arthroplasty. However, there are radiographic concerns regarding poor implant fixation and bone ingrowth around electron beam melted (EBMed) 3D porous cups. We hypothesize that nano-hydroxyapatite (nHA) coating can promote bone ingrowth and thus decrease the occurrence of radiolucent lines around EBMed 3D porous cups. This study aimed to investigate the effect of a novel nHA coating on the biological performance of EBMed 3D porous implants in a beagle transcortical model. Low-porosity (control) and high-porosity 3D porous Ti-6Al-4V implants were manufactured using EBM. Half of the high-porosity implants were coated with nHA without clogging the 3D pores. Implants were inserted into the femoral diaphysis of the beagles. The beagles were euthanized at 4, 8, and 12 weeks postoperatively, and push-out testing was performed. Bone ingrowth was evaluated by histological analysis. Although the increase in porosity alone had no effect on biological behavior, the addition of nHA to high-porosity 3D implants significantly improved early bone fixation and bone ingrowth into the deep region of porous structures compared to low-porosity implants. This is the first report of a novel nHA coating that improved bone ingrowth into the deeper regions of 3D porous implants, which can prevent the occurrence of radiolucent lines around EBMed 3D porous cups.

Effect of Smoke Exposure on Gene Expression in Bone Healing around Implants Coated with Nanohydroxyapatite

This study evaluated the effect of smoke exposure on the expression of genes related to bone metabolism in implants coated with nanohydroxyapatite (NHA). A total of 36 rats were exposed to cigarette smoke for 60 days. The animals were allocated into three groups: machined implants (MAC), dual acid-etched implants (DAE), and NHA-coated implants (NHA). Implants were installed in the left tibia of the rats after 30 days of smoke exposure. The implants were retrieved 7 and 30 days after implantation, and the adjacent bone analyzed using a real-time polymerase chain reaction for gene expression of alkaline phosphatase (ALP), osteopontin (OPN), receptor activator of the nuclear factor kappa ligand (RANKL), osteoprotegerin (OPG), the RANKL/OPG ratio, osteocalcin (OCN) and runt-related transcription factor 2 (Runx2). After 7 days, Runx2, OPN and OPG expression demonstrated significantly higher levels for the NHA surface treatment relative to DAE and MAC surfaces. NHA presented the lowest RANKL and RANKL/OPG levels. After 30 days, NHA-coated implants showed significantly higher levels of Runx2, ALP, OPN, OPG, OC, RANKL and RANKL/OPG relative to DAE and MAC implants. The results indicated a greater osteogenic and high osteoclastic activity around NHA implants, in comparison to DAE and MAC implants.

Evaluation of Bone Response to a Nano HA Implant Surface on Sinus Lifting Procedures: Study in Rabbits

The aim of this study was to evaluate the bone response to two different implant surfaces on sinus lift procedures in rabbits. Bilateral sinus lifting with inorganic bovine bone associated with collagen membrane and immediate implantation were performed in 16 rabbits. Custom mini-implants were randomly installed in the prepared sites: one side received a double acid-etched (DAE) surface and the other a nano-hydroxyapatite (NHA) surface. The animals were euthanized 30 and 60 days after surgery, and biopsies were collected for microtomographic and histomorphometric analysis. After 30 days, no intra- and inter-group statistical differences were observed in microtomographic analysis, while at 60 days, bone analysis showed statistically significant differences between groups (p < 0.05) for all the evaluated parameters. Histomorphometric analysis showed, after 30 days, mean % of Bone-to-Implant Contact (BIC) for DAE and NHA of 31.70 ± 10.42% vs. 40.60 ± 10.22% (p > 0.05), respectively; for % of Bone Area Fraction Occupancy (BAFO), mean values were 45.43 ± 3.597% for DAE and 57.04 ± 5.537% for NHA (p < 0.05). After 60 days, mean %BIC and %BAFO for DAE and NHA implants were statistically significant (p < 0.05). The NHA surface showed superior biological features compared to the DAE treatment, promoting higher bone formation around the implants in an experimental model of bone repair in a grafted area.

Biomimetic Inorganic Nanoparticle-Loaded Silk Fibroin-Based Coating with Enhanced Antibacterial and Osteogenic Abilities

Poor osseointegration and infection are the main reasons leading to the failure of hard tissue implants; especially, in recent years, the failure rate has been increasing every year owing to the continuously increasing conditions such as injury, trauma, diseases, or infections. Therefore, the development of a biomimetic surface coating of bone tissues with antibacterial function is an effective means to improve bone healing and inhibit bacterial infection. Mimicking the natural bone, in this study, we have designed a silk fibroin (collagen-like structure)-based coating inlaid with nanohydroxyapatite (nHA) and silver nanoparticles (AgNPs) for promoting antibacterial ability and osteogenesis, especially focusing on the bone mimetic structure for enhancing bone health. Observing the morphology and size of the composite nanoparticles by transmission electron microscope (TEM), nHA provided nucleation sites for the formation of AgNPs, forming an nHA/AgNP complex with a size of about 100-200 nm. Characterization of the nHA/Ag-loaded silk fibroin biomimetic coating showed an increased surface roughness with good density and compact performances. The silk fibroin-based coating loaded with uniformly distributed AgNPs and nHA could effectively inhibit the adhesion of Staphylococcus aureus on the surface and, at the same time, quickly kill planktonic bacteria, indicating their good antibacterial ability. In vitro cell experiments revealed that the biomimetic silk fibroin-based coating was beneficial to the adhesion, spreading, and proliferation of osteoblasts (MC3T3-E1). In addition, by characterizing LDH and ROS, it was found that the nHA/Ag complex could significantly reduce the cytotoxicity of AgNPs, and the osteoblasts on the coating surface maintained the structure intact.

Biomimetic Calcium Phosphate Coatings for Bioactivation of Titanium Implant Surfaces: Methodological Approach and In Vitro Evaluation of Biocompatibility

Ti6Al4V as a common implant material features good mechanical properties and corrosion resistance. However, untreated, it lacks bioactivity. In contrast, coatings with calcium phosphates (CaP) were shown to improve cell-material interactions in bone tissue engineering. Therefore, this work aimed to investigate how to tailor biomimetic CaP coatings on Ti6Al4V substrates using modified biomimetic calcium phosphate (BCP) coating solutions. Furthermore, the impact of substrate immersion in a 1 M alkaline CaCl2 solution (pH = 10) on subsequent CaP coating formation was examined. CaP coatings were characterized via scanning electron microscopy, x-ray diffraction, energy-dispersive x-ray spectroscopy, and laser-scanning microscope. Biocompatibility of coatings was carried out with primary human osteoblasts analyzing cell morphology, proliferation, collagen type 1, and interleukin 6 and 8 release. Results indicate a successful formation of low crystalline hydroxyapatite (HA) on top of every sample after immersion in each BCP coating solution after 14 days. Furthermore, HA coating promoted cell proliferation and reduced the concentration of interleukins compared to the uncoated surface, assuming increased biocompatibility.

Biomaterials for bone regeneration: an orthopedic and dentistry overview

Because bone-associated diseases are increasing, a variety of tissue engineering approaches with bone regeneration purposes have been proposed over the last years. Bone tissue provides a number of important physiological and structural functions in the human body, being essential for hematopoietic maintenance and for providing support and protection of vital organs. Therefore, efforts to develop the ideal scaffold which is able to guide the bone regeneration processes is a relevant target for tissue engineering researchers. Several techniques have been used for scaffolding approaches, such as diverse types of biomaterials. On the other hand, metallic biomaterials are widely used as support devices in dentistry and orthopedics, constituting an important complement for the scaffolds. Hence, the aim of this review is to provide an overview of the degradable biomaterials and metal biomaterials proposed for bone regeneration in the orthopedic and dentistry fields in the last years.

Histological and Nanomechanical Properties of a New Nanometric Hydroxiapatite Implant Surface. An In Vivo Study in Diabetic Rats

Implant therapy is a predictable treatment to replace missing teeth. However, the osseointegration process may be negatively influenced by systemic conditions, such as diabetes mellitus (DM). Microtopography and implant surface developments are strategies associated to better bone repair. This study aimed to evaluate, in healthy and diabetic rats, histomorphometric (bone to implant contact = %BIC; and bone area fraction occupancy = %BAFO) and nanomechanical (elastic modulus = EM; and hardness = H) bone parameters, in response to a nanometric hydroxyapatite implant surface. Mini implants (machined = MAC; double acid etched = DAE, and with addition of nano-hydroxyapatite = NANO) were installed in tibias of healthy and diabetic rats. The animals were euthanized at 7 and 30 days. NANO surface presented higher %BIC and %BAFO when compared to MAC and DAE (data evaluated as a function of implant surface). NANO surface presented higher %BIC and %BAFO, with statistically significant differences (data as a function of time and implant surface). NANO surface depicted higher EM and H values, when compared to machined and DAE surfaces (data as a function of time and implant surface). Nano-hydroxyapatite coated implants presented promising biomechanical results and could be an important tool to compensate impaired bone healing reported in diabetics.

Osteoconductive and Osteoinductive Surface Modifications of Biomaterials for Bone Regeneration: A Concise Review

The main aim of bone tissue engineering is to fabricate highly biocompatible, osteoconductive and/or osteoinductive biomaterials for tissue regeneration. Bone implants should support bone growth at the implantation site via promotion of osteoblast adhesion, proliferation, and formation of bone extracellular matrix. Moreover, a very desired feature of biomaterials for clinical applications is their osteoinductivity, which means the ability of the material to induce osteogenic differentiation of mesenchymal stem cells toward bone-building cells (osteoblasts). Nevertheless, the development of completely biocompatible biomaterials with appropriate physicochemical and mechanical properties poses a great challenge for the researchers. Thus, the current trend in the engineering of biomaterials focuses on the surface modifications to improve biological properties of bone implants. This review presents the most recent findings concerning surface modifications of biomaterials to improve their osteoconductivity and osteoinductivity. The article describes two types of surface modifications: (1) Additive and (2) subtractive, indicating biological effects of the resultant surfaces in vitro and/or in vivo. The review article summarizes known additive modifications, such as plasma treatment, magnetron sputtering, and preparation of inorganic, organic, and composite coatings on the implants. It also presents some common subtractive processes applied for surface modifications of the biomaterials (i.e., acid etching, sand blasting, grit blasting, sand-blasted large-grit acid etched (SLA), anodizing, and laser methods). In summary, the article is an excellent compendium on the surface modifications and development of advanced osteoconductive and/or osteoinductive coatings on biomaterials for bone regeneration.