Nano-scale modification of titanium implant surfaces to enhance osseointegration

Surface modification strategies to improve titanium hemocompatibility: a comprehensive review

Titanium and its alloys are widely used in different biomaterial applications due to their remarkable mechanical properties and bio-inertness. However, titanium-based materials still face some challenges, with an emphasis on hemocompatibility. Blood-contacting devices such as stents, heart valves, and circulatory devices are prone to thrombus formation, restenosis, and inflammation due to inappropriate blood-implant surface interactions. After implantation, when blood encounters these implant surfaces, a series of reactions takes place, such as protein adsorption, platelet adhesion and activation, and white blood cell complex formation as a defense mechanism. Currently, patients are prescribed anticoagulant drugs to prevent blood clotting, but these drugs can weaken their immune system and cause profound bleeding during injury. Extensive research has been done to modify the surface properties of titanium to enhance its hemocompatibility. Results have shown that the modification of surface morphology, roughness, and chemistry has been effective in reducing thrombus formation. The main focus of this review is to analyze and understand the different modification techniques on titanium-based surfaces to enhance hemocompatibility and, consequently, recognize the unresolved challenges and propose scopes for future research.

Osteoblast Response to Copper-Doped Microporous Coatings on Titanium for Improved Bone Integration

Due to their excellent mechanical properties and good biocompatibility, titanium alloys have become a popular research topic in the field of medical metal implants. However, the surface of the titanium alloy does not exhibit biological activity, which may cause poor integration between the interface of the titanium implant and the interface of the bone tissue and subsequently may cause the implant to fall off. Therefore, surface biological inertness is one of the problems that titanium alloys must overcome to become an ideal orthopedic implant material. Surface modification can improve the biological properties of titanium, thereby enhancing its osseointegration effect. Copper is an essential trace element for the human body, can promote bone formation and plays an important role in maintaining the physiological structure and function of bone and bone growth and development. In this study, a microporous copper-titanium dioxide coating was prepared on the surface of titanium by microarc oxidation. Based on the evaluation of its surface characteristics, the adhesion, proliferation and differentiation of MC3T3-E1 cells were observed. A titanium rod was implanted into the rabbit femoral condyle, and the integration of the coating and bone tissue was evaluated. Our research results show that the microporous copper-titanium dioxide coating has a nearly three-dimensional porous structure, and copper is incorporated into the coating without changing the structure of the coating. In vitro experiments found that the coating can promote the adhesion, proliferation and differentiation of MC3T3-E1 cells. In vivo experiments further confirmed that the titanium copper-titanium dioxide microporous coating can promote the osseointegration of titanium implants. In conclusion, copper-titanium dioxide microporous coatings can be prepared by microarc oxidation, which can improve the biological activity and biocompatibility of titanium, promote new bone formation and demonstrate good osteoinductive properties. Therefore, the use of this coating in orthopedics has potential clinical application.

Anodic TiO2 Nanotubes: Tailoring Osteoinduction via Drug Delivery

TiO₂ nanostructures and more specifically nanotubes have gained significant attention in biomedical applications, due to their controlled nanoscale topography in the sub-100 nm range, high surface area, chemical resistance, and biocompatibility. Here we review the crucial aspects related to morphology and properties of TiO₂ nanotubes obtained by electrochemical anodization of titanium for the biomedical field. Following the discussion of TiO₂ nanotopographical characterization, the advantages of anodic TiO₂ nanotubes will be introduced, such as their high surface area controlled by the morphological parameters (diameter and length), which provides better adsorption/linkage of bioactive molecules. We further discuss the key interactions with bone-related cells including osteoblast and stem cells in in vitro cell culture conditions, thus evaluating the cell response on various nanotubular structures. In addition, the synergistic effects of electrical stimulation on cells for enhancing bone formation combining with the nanoscale environmental cues from nanotopography will be further discussed. The present review also overviews the current state of drug delivery applications using TiO₂ nanotubes for increased osseointegration and discusses the advantages, drawbacks, and prospects of drug delivery applications via these anodic TiO₂ nanotubes.

Microbial Decontamination and Antibacterial Activity of Nanostructured Titanium Dental Implants: A Narrative Review

Peri-implantitis is the major cause of the failure of dental implants. Since dental implants have become one of the main therapies for teeth loss, the number of patients with peri-implant diseases has been rising. Like the periodontal diseases that affect the supporting tissues of the teeth, peri-implant diseases are also associated with the formation of dental plaque biofilm, and resulting inflammation and destruction of the gingival tissues and bone. Treatments for peri-implantitis are focused on reducing the bacterial load in the pocket around the implant, and in decontaminating surfaces once bacteria have been detached. Recently, nanoengineered titanium dental implants have been introduced to improve osteointegration and provide an osteoconductive surface; however, the increased surface roughness raises issues of biofilm formation and more challenging decontamination of the implant surface. This paper reviews treatment modalities that are carried out to eliminate bacterial biofilms and slow their regrowth in terms of their advantages and disadvantages when used on titanium dental implant surfaces with nanoscale features. Such decontamination methods include physical debridement, chemo-mechanical treatments, laser ablation and photodynamic therapy, and electrochemical processes. There is a consensus that the efficient removal of the biofilm supplemented by chemical debridement and full access to the pocket is essential for treating peri-implantitis in clinical settings. Moreover, there is the potential to create ideal nano-modified titanium implants which exert antimicrobial actions and inhibit biofilm formation. Methods to achieve this include structural and surface changes via chemical and physical processes that alter the surface morphology and confer antibacterial properties. These have shown promise in preclinical investigations.

Tantalum and its derivatives in orthopedic and dental implants: Osteogenesis and antibacterial properties

Implant-associated infections and aseptic loosening are some of the main reasons for implant failure. Therefore, there is an urgent need to improve the osseointegration and antibacterial capabilities of implant materials. In recent years, a large number of breakthroughs in the biological application of tantalum and its derivatives have been achieved. Owing to their corrosion resistance, biocompatibility, osseointegration ability, and antibacterial properties, they have shown considerable potential in orthopedic and dental implant applications. In this review, we provide the latest progress and achievements in the research on osseointegration and antibacterial properties of tantalum as well as its derivatives, and summarize the surface modification methods to enhance their osseointegration and antibacterial properties.

Iodine-Loaded Calcium Titanate for Bone Repair with Sustainable Antibacterial Activity Prepared by Solution and Heat Treatment

In the orthopedic and dental fields, simultaneously conferring titanium (Ti) and its alloy implants with antibacterial and bone-bonding capabilities is an outstanding challenge. In the present study, we developed a novel combined solution and heat treatment that controllably incorporates 0.7% to 10.5% of iodine into Ti and its alloys by ion exchange with calcium ions in a bioactive calcium titanate. The treated metals formed iodine-containing calcium-deficient calcium titanate with abundant Ti-OH groups on their surfaces. High-resolution XPS analysis revealed that the incorporated iodine ions were mainly positively charged. The surface treatment also induced a shift in the isoelectric point toward a higher pH, which indicated a prevalence of basic surface functionalities. The Ti loaded with 8.6% iodine slowly released 5.6 ppm of iodine over 90 days and exhibited strong antibacterial activity (reduction rate >99%) against methicillin-resistant Staphylococcus aureus (MRSA), S. aureus, Escherichia coli, and S. epidermidis. A long-term stability test of the antibacterial activity on MRSA showed that the treated Ti maintained a >99% reduction until 3 months, and then it gradually decreased after 6 months (to a 97.3% reduction). There was no cytotoxicity in MC3T3-E1 or L929 cells, whereas apatite formed on the treated metal in a simulated body fluid within 3 days. It is expected that the iodine-carrying Ti and its alloys will be particularly useful for orthopedic and dental implants since they reliably bond to bone and prevent infection owing to their apatite formation, cytocompatibility, and sustainable antibacterial activity.

The resin-matrix cement layer thickness resultant from the intracanal fitting of teeth root canal posts: an integrative review

OBJECTIVE

The aim of this study was to perform an integrative review on the layer thickness and microstructure of resin-matrix cements around custom-made or standard teeth root intracanal posts.

MATERIALS AND METHODS

An electronic search was conducted on the PubMed using a combination of the following scientific terms: intraradicular post, root intracanal post, resin cement, thickness, adaptation, endodontic post, layer thickness, fit, shape, and endodontic core. The literature selection criteria accepted articles published in the English language, up to May 2021, involving in vitro analyses, meta-analyses, randomized controlled trials, and prospective cohort studies.

RESULTS

The search identified 154 studies, of which 24 were considered relevant to this study. The selected studies provided important data considering cement layer thickness, tooth preparation, endodontic post, and type of resin-matrix cement. The anatomical variability of root canal systems, such as the oval- or C-shaped, represents a challenge in dental restoration with tooth root intracanal posts. The fitting of intracanal posts to different root regions is variable resulting in thick and irregular layers of resin-matrix cement. Defects like pores, micro-cracks, and micro-gaps were detected in the resin-matrix cement microstructure and represent spots of stress concentration and fracture. Custom-made tooth root intracanal posts provide a proper fitting and decrease the layer thickness of resin-matrix cement.

CONCLUSIONS

In fact, the layer thickness of resin-matrix cements depends on the fitting of endodontic posts to tooth root canals. An increase of resin cement thickness causes the appearance of defects like pores, micro-cracks, and micro-gaps that can induce stress concentration and fractures at interfaces.

CLINICAL RELEVANCE

The fitting of the endodontic post into the teeth root canal determine the layer thickness of the resin-matrix cement to establish an adequate retention. However, the increase in the thickness of the resin-matrix cement layer can lead to a high number of defects like pores or cracks and therefore decrease the strength of the interface.

Strontium-incorporated titanium implant surfaces treated by hydrothermal treatment enhance rapid osseointegration in diabetes: A preclinical vivo experimental study

OBJECTIVES

The aim of the current study was to explore effects of strontium-incorporated titanium implant surfaces by hydrothermal treatment on osseointegration in diabetic rats.

MATERIALS AND METHODS

The surface characteristics of SLA and SLA-Sr surfaces were detected by related instruments. Thirty-six male Sprague-Dawley rats were induced into diabetes, and thirty-six rats were normal. SLA and SLA-Sr implants were, respectively, inserted into bilateral tibial metaphysis of each rat. Percentage of bone-to-implant contact (BIC%) and percentage of bone area (BA%) were analyzed at 4 and 8 weeks after implantation. Immunohistochemistry of osteoprotegerin (OPG) and Wnt5a were conducted at 1 and 4 weeks. Gene expression levels of inflammatory cytokines and related signaling molecules in peri-implant bone tissue were detected at 3 and 7 days.

RESULTS

Strontium was uniformly distributed on SLA-Sr surfaces, and it was released in an effective concentration range. SLA-Sr surfaces showed significantly higher BIC% in diabetic rats at 4 (p < .05) and 8 weeks (p < .05). Besides, it displayed higher BIC% at 4 weeks (p < .05) in normal rats. Also, SLA-Sr surfaces upregulated expression of OPG at 4 weeks (p < .05) in diabetic rats. What's more, SLA-Sr surfaces downregulated inflammation (TNF-α, IL-1β, and IL-6; p < .01) in diabetic rats at 3 days. In addition, expression of Wnt5a and ROR2 was upregulated (p < .05) at 7 days after implantation under diabetes.

CONCLUSION

It is suggested that strontium-incorporated titanium implant surfaces by hydrothermal treatment could enhance implant osseointegration as compared with SLA implant surfaces in diabetic rats.

[Effects of femtosecond laser treatment on surface characteristics and flexural strength of zirconia]

OBJECTIVE

To evaluate the effects of femtosecond laser treated microgrooved surface on microscopic topography, phase transformation, and three-points flexural strength of zirconia, and to provide reference for surface microstructure optimization of zirconia implant.

METHODS

According to different surface treatment methods, 57 computer aided design/computer aided manufacture (CAD/CAM) zirconia bars (20.0 mm×4.0 mm×1.4 mm) were evenly divided into three groups: sintered group, no treatment after sintering, taken as control; sandblasted group, sandblasted with 110 μm aluminium oxide (Al₂O₃) after sintering; microgrooved group, femtosecond laser fabricated microgrooves with 50 μm width, 30 μm depth, and 100 μm pitch. Surface microscopic topography was observed with scanning electron microscope (SEM) and 3D laser microscope. Further, surface roughness in each group and microgroove size were measured. Crystal phase was analyzed with X-ray diffraction. Specimens were subjected to three- points flexural strength test, and Weibull distribution was used to analyze their strength characteristics.

RESULTS

SEM showed that sintered surface was flat with clear grain structure; sandblasted surface exihibited bumps and holes with sharp margins and irregular shape; microgrooves were regularly aligned without evident defect, and nano-scale particles were observed on the surface inside of the microgrooves. Ra value of microgrooved group [(9.42±0.28)] μm was significantly higher than that of sandblasted group [(1.04±0.03) μm] and sintered group [(0.60±0.04) μm], and there was statistical difference between sandblasted group and sintered group (P < 0.001). The microgroove size was precise with (49.75±1.24) μm width, (30.85±1.02) μm depth, and (100.58±1.94) μm pitch. Crystal phase analysis showed that monoclinic volume fraction of sandblasted group (18.17%) was much higher than that of sintered group (1.55%), while microgrooved group (2.21%) was similar with sintered group. The flexural strength of sandblasted group (986.22±163.25) MPa had no statistical difference with that of sintered group (946.46±134.15) MPa (P=0.847), but the strength in microgrooved group (547.92±30.89) MPa dropped significantly compared with the other two groups (P < 0.001). Weibull modulus of sintered, sandblasted, microgrooved groups were 7.89, 6.98, and 23.46, respectively.

CONCLUSION

Femtosecond laser was able to form micro/nanostructured microgrooves on zirconia surface, which deleteriously affected the flexural strength of zirconia.

Nano-hydroxyapatite coated TiO2 nanotubes on Ti-19Zr-10Nb-1Fe alloy promotes osteogenesis in vitro

Titanium and titanium alloys have broad applications in orthopedic implants due to their excellent mechanical properties and biocompatibility. The biological activity of the metallic implants can be improved by implementing a nano-hydroxyapatite (nano-HA) coating, while it is still challenging to synthesize uniform and stable nano-HA on the metallic materials. The characterization results confirmed that the nanotube array with a diameter of 87 ± 21 nm and a length of 8.1 ± 1.3 μm is achieved by using double anodic oxidation, and then microsphere-like nano-HA crystals are formed on the TiO₂ nanotube arrays. Through X-ray diffraction (XRD) and Fourier Transform Infrared Spectrometer (FT-IR) analysis, it is determined that the chemical composition of the coating is hydroxyapatite. in vitro cell experiments, compared to the TZNF metal surface, the TZNF-NTs/HA is beneficial to the proliferation and adhesion of osteoblasts, and the activity of ALP was 6.93 ± 0.47 DEA unit and the content of OCN was 7.04 ± 0.51 ng/L. In terms of the expression of osteogenic gene information as osterix, osteopontin, and osteonectin, the mRNA levels of TZNF-NTs/HA were 2.6-fold, 1.6-fold, and 4.3-fold higher than that of TZNF samples, respectively, at 14 days. The results suggested that the introduction of nano-HA improves osteoblast differentiation and local factor production, as well as indicates the potential for improved implant osseointegration.

Research to Clinics: Clinical Translation Considerations for Anodized Nano-Engineered Titanium Implants

Titania nanotubes (TNTs) fabricated on titanium orthopedic and dental implants have shown significant potential in "proof of concept" in vitro, ex vivo, and short-term in vivo studies. However, most studies do not focus on a clear direction for future research towards clinical translation, and there exists a knowledge gap in identifying key research challenges that must be addressed to progress to the clinical setting. This review focuses on such challenges with respect to anodized titanium implants modified with TNTs, including optimized fabrication on clinically utilized microrough surfaces, clinically relevant bioactivity assessments, and controlled/tailored local release of therapeutics. Further, long-term in vivo investigations in compromised animal models under loading conditions are needed. We also discuss and detail challenges and progress related to the mechanical stability of TNT-based implants, corrosion resistance/electrochemical stability, optimized cleaning/sterilization, packaging/aging, and nanotoxicity concerns. This extensive, clinical translation focused review of TNTs modified Ti implants aims to foster improved understanding of key research gaps and advances, informing future research in this domain.

Post-treatments of polydopamine coatings influence cellular response

Polydopamine (PDA) is the final oxidation product of dopamine or other catecholamines. Since the first reports of PDA coatings starting around 2007, these coatings have been widely studied as a versatile and inexpensive one-step coating option for biomaterial functionalization. The coating attach to a wide range of materials and can subsequently be modified with biomolecules or nanoparticles. However, as a strong candidate for biomaterial research and even clinical use, it is important to unravel the changes in physico-chemical properties and the cell-PDA interaction as a function of heat sterilization procedures and shelf storage periods. Four groups were examined in this study: titanium (Ti), PDA-coated Ti samples and PDA-coated Ti samples either stored for up to two weeks at room temperature or heated at 121 °C for 24 h, respectively. We used X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Water contact angle (WCA) to characterize chemical composition and surface properties of the groups. Cell adhesion and proliferation was examined by three different cell types: human primary dermal fibroblasts (hDF), human epidermal keratinocytes (HaCaTs) and a murine preosteoblastic cell line (MC3T3-E1), respectively. Cells were cultured on PDA coated samples for 4 h, 3 days and 5 days. Both thermal treatment of PDA at 121℃ for 24 h and storage of the samples for 2 weeks increased the amount of quinone groups at the surface and decreased the amount of primary amine groups as detected by XPS and ToF-SIMS. Even though these surface reactions increased the WCA of the PDA coating, we found that the post-treatments increased cell proliferation for both hDFs, HaCaTs and MC3T3-E1 s as compared to pristine PDA. This emphasizes the importance of post-treatment and shelf-time for PDA coatings.

Femtosecond laser-induced nanoporous layer for enhanced osteogenesis of titanium implants

The osteogenic activity of medical metal can be improved by lowering its surface stiffness and elastic modulus. However, it is very difficult to directly reduce the elastic modulus of medical metal surfaces. In this paper, with selected parameters, the titanium surface was treated via femtosecond laser irradiation. Micro indentation revealed that the femtosecond laser ablation can effectively reduce the surface Young's modulus and Vickers hardness of titanium. Besides, In order to explain the mechanical properties of degradation of titanium surface, Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) was used to simulate the process of laser ablation process of titanium surface, and it was found that after the ablation of titanium surface, voids were produced in the subsurface layer. The simulation showed that the voids are formed by the cavitation of metastable liquid induced by high tensile stress and high temperature during femtosecond laser irradiation. Subsurface voids with a thickness of about 40 nm were observed under the oxide layer in the experiment. Cell experiments showed that the surface with low Young's modulus was more conducive to cell proliferation and osteogenic differentiation.

mTORC2 regulates hierarchical micro/nano topography-induced osteogenic differentiation via promoting cell adhesion and cytoskeletal polymerization

Surface topography acts as an irreplaceable role in the long‐term success of intraosseous implants. In this study, we prepared the hierarchical micro/nano topography using selective laser melting combined with alkali heat treatment (SLM‐AHT) and explored the underlying mechanism of SLM‐AHT surface‐elicited osteogenesis. Our results show that cells cultured on SLM‐AHT surface possess the largest number of mature FAs and exhibit a cytoskeleton reorganization compared with control groups. SLM‐AHT surface could also significantly upregulate the expression of the cell adhesion‐related molecule p‐FAK, the osteogenic differentiation‐related molecules RUNX2 and OCN as well as the mTORC2 signalling pathway key molecule Rictor. Notably, after the knocked‐down of Rictor, there were no longer significant differences in the gene expression levels of the cell adhesion‐related molecules and osteogenic differentiation‐related molecules among the three titanium surfaces, and the cells on SLM‐AHT surface failed to trigger cytoskeleton reorganization. In conclusion, the results suggest that mTORC2 can regulate the hierarchical micro/nano topography‐mediated osteogenesis via cell adhesion and cytoskeletal reorganization.

The effect of fluid shear stress on fibroblasts and stem cells on plane and groove topographies

In this study, we aimed to study the effect of fluid shear stress on fibroblasts and BMSCs on plane and groove topographies. The results showed that 0.6-Hz stress had the greatest influence on the alignment, polarity, migration and adhesion of fibroblasts on plane by increasing the expression of reoriented actin and vinculin; whereas 1.0-Hz stress promoted differentiation of fibroblasts into myofibroblasts by increasing Col-I and α-SMA expression. Interestingly, under the given frequency stress, the groove structure strengthened the above characteristics of fibroblasts beyond adhesion, and promoted differentiation of BMSCs into myofibroblasts. The above results indicate that 0.6 Hz may improve the implant-tissue sealing, while 1.0-Hz stress probably causes the disordered fiber deposition around implants.

Innovative Surface Modification Procedures to Achieve Micro/Nano-Graded Ti-Based Biomedical Alloys and Implants

Due to the growing aging population of the world, and as a result of the increasing need for dental implants and prostheses, the use of titanium and its alloys as implant materials has spread rapidly. Although titanium and its alloys are considered the best metallic materials for biomedical applications, the need for innovative technologies is necessary due to the sensitivity of medical applications and to eliminate any potentially harmful reactions, enhancing the implant-to-bone integration and preventing infection. In this regard, the implant’s surface as the substrate for any reaction is of crucial importance, and it is accurately addressed in this review paper. For constructing this review paper, an internet search was performed on the web of science with these keywords: surface modification techniques, titanium implant, biomedical applications, surface functionalization, etc. Numerous recent papers about titanium and its alloys were selected and reviewed, except for the section on forthcoming modern implants, in which extended research was performed. This review paper aimed to briefly introduce the necessary surface characteristics for biomedical applications and the numerous surface treatment techniques. Specific emphasis was given to micro/nano-structured topographies, biocompatibility, osteogenesis, and bactericidal effects. Additionally, gradient, multi-scale, and hierarchical surfaces with multifunctional properties were discussed. Finally, special attention was paid to modern implants and forthcoming surface modification strategies such as four-dimensional printing, metamaterials, and metasurfaces. This review paper, including traditional and novel surface modification strategies, will pave the way toward designing the next generation of more efficient implants.

Behavior of rat bone marrow stem cells on titanium surfaces modified by laser-beam and deposition of calcium phosphate

OBJECTIVES

The aim of this study was to evaluate the behavior of rat bone marrow stem cells seeded on a Ti-15Mo alloy surface modified by laser-beam irradiation followed by calcium phosphate deposition.

MATERIALS AND METHODS

A total of four groups were evaluated: polished commercially pure titanium (cpTi): Ti-P; laser irradiation + calcium phosphate deposition on cpTi: Ti-LCP; polished Ti-15Mo alloy: Ti15Mo-P; and laser irradiation + calcium phosphate deposition on Ti-15Mo alloy: Ti15Mo-LCP. Before and after laser irradiation and calcium phosphate deposition on the surfaces, physicochemical and morphological analyses were performed: Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDX). The wettability of the samples was evaluated by contact angle measurement. In addition, the behavior of osteoblast-like cells to these surfaces was evaluated for cell morphology, adhesion, proliferation and viability, evaluation of alkaline phosphatase formation and gene expression of osteogenesis markers.

RESULTS

Surfaces wet-abrade with grit paper (P) showed oriented groves, while the laser irradiation and calcium phosphate deposition (LCP) produced porosity on both cpTi and Ti15Mo alloy groups with deposits of hydroxyapatite (HA) crystals (SEM). EDX showed no contamination after surface modification in both metal samples. A complete wetting was observed for both LCP groups, whereas P surfaces exhibited high degree of hydrophobicity. There was a statistical difference in the intragroup comparison of proliferation and viability (p < 0.05). The ALP activity showed higher values in the Ti15Mo alloy at 10 days of culture. The gene expression of bone related molecules did not present significant differences at 7 and 14 days among different metals and surface treatments.

CONCLUSION

Ti15-Mo seems to be an alternative alloy to cpTi for dental implants. Surface treatment by laser irradiation followed by phosphate deposition seems to positively interact with bone cells.

CLINICAL RELEVANCE

Ti-15Mo alloy surface modified by laser-beam irradiation followed by calcium phosphate deposition may improve and accelerate the osseointegration process of dental implants.

Bioactive Ibuprofen-Loaded PLGA Coatings for Multifunctional Surface Modification of Medical Devices

To modulate the biofunctionality of implantable medical devices commonly used in clinical practice, their surface modification with bioactive polymeric coatings is an attractive and successful emerging strategy. Biodegradable coatings based on poly(lactic acid-co-glycolic acid), PLGA, represent versatile and safe candidates for surface modification of implantable biomaterials and devices, providing additional tunable ability for topical delivery of desired therapeutic agents. In the present study, Ibuprofen-loaded PLGA coatings (PLGA/IBUP) were obtained by using the dip-coating and drop-casting combined protocol. The composite materials demonstrated long-term drug release under biologically simulated dynamic conditions. Reversible swelling phenomena of polymeric coatings occurred in the first two weeks of testing, accompanied by the gradual matrix degradation and slow release of the therapeutic agent. Irreversible degradation of PLGA coatings occurred after one month, due to copolymer's hydrolysis (evidenced by chemical and structural modifications). After 30 days of dynamic testing, the cumulative release of IBUP was ~250 µg/mL. Excellent cytocompatibility was revealed on human-derived macrophages, fibroblasts and keratinocytes. The results herein evidence the promising potential of PLGA/IBUP coatings to be used for surface modification of medical devices, such as metallic implants and wound dressings.

An Experimental Investigation of Controlled Changes in Wettability of Laser-Treated Surfaces after Various Post Treatment Methods

In this paper, a quick nanosecond laser micro structuring process was employed to change the surface wettability of Ti6Al4V alloy. The same laser structuring method was used throughout, but with varying input fluence. The laser processing parameters resulted in high surface melting. After laser treatment, four post-processing methods were used, namely high vacuum, low temperature annealing, storage in a polyethylene bag, and storage in ambient air. Subsequently, the water droplet contact angle was measured over a long time period of 55 days. The results show that the sample stored in ambient air remained hydrophilic. On the other hand, the sample post-processed in a vacuum chamber behaved hydrophobically with a contact angle of approximately 150°. Other post-processing did not lead to specific wettability behavior. After wettability testing, all samples were cleaned ultrasonically in distilled water. This cleaning process led to annulation of all obtained properties through post-processing. In summary, this paper shows that it is more important to study surface chemistry than topography in terms of effects on wettability. Moreover, surface wettability can be controlled by laser structuring, post-processing, and surface cleaning.

The early loading of different surface-modified implants: a randomized clinical trial

BACKGROUND

Various surface treatment options have been adopted with the aim to improve osseointegration, reducing the overall treatment time. Implant stability of early loaded implants with different modified surfaces was compared in the present study.

METHODS

Patients were selected from the Department of Oro-Maxillofacial Surgery and Stomatology at Semmelweis University. Patients randomly received SA (alumina sandblasted and acid-etched), NH (bioabsorbable apatite nanocoating) or SLA (large-grit sandblasted and acid-etched) surface implants. Outcome measures were: implant success, implant stability, and periodontal parameters. The implant stability was measured at the time of implant placement (primary stability) and six weeks after (prothesis delivery, secondary stability). Osstell and Periotest were applied to take all the measurements. The primary and secondary stability were compared in the three study groups Finally the periimplant probing depth appearing after three months of loading was checked on 6 points around to the implant-supported prostheses. Shapiro-Wilk and Mann-Whitney tests were used for the comparison between the study groups.

RESULTS

A total of 75 implants with different length and diameter were inserted into various positions. One implant failed spontaneously at the fourth week after implant placement. The survival rate was 98,7%. Comparing the primary and secondary stability values, the data were significantly improved in every groups. The difference was the highest in the NH group, however, this difference was not significant compared to the two other groups. Good periodontal parameters were experienced in all the tested implants, independently by the groups.

CONCLUSIONS

With the limitation of the present study, all the implants showed improved stability six weeks after implant placement. A trend of higher result was found for the NH group. Further studies with longer follow-up are needed to confirm this preliminary results.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN13181677; the date of registration: 04/03/2021. Retrospectively registered.

Surface modifications to enhance osseointegration-Resulting material properties and biological responses

As life expectancy and the age of the general population increases so does the need for improved implants. A major contributor to the failure of implants is poor osseointegration, which is typically described as the direct connection between bone and implant. This leads to unnecessary complications and an increased burden on the patient population. Modification of the implant surfaces through novel techniques, such as varying topography and/or applying coatings, has become a popular method to enhance the osseointegration capability of implants. Recent research has shown that particular surface features influence how bone cells interact with a material; however, it is unknown which exact features achieve optimal bone integration. In this review, current methods of modifying surfaces will be highlighted, and the resulting surface characteristics and biological responses are discussed. Review of the current strategies of surface modifications found that many coating types are more advantageous when used in combination; however, finding a surface modification that utilizes the mutual beneficial effects of important surface characteristics while still maintaining commercial viability is where future challenges exist.

Antimicrobial and enzyme-responsive multi-peptide surfaces for bone-anchored devices

Functionalization of dental and orthopedic implants with multiple bioactivities is desirable to obtain surfaces with improved biological performance and reduced infection rates. While many approaches have been explored to date, nearly all functionalized surfaces are static, i.e., non-responsive to biological cues. However, tissue remodeling necessary for implant integration features an ever-changing milieu of cells that demands a responsive biomaterial surface for temporal synchronization of interactions between biomaterial and tissue. Here, we successfully synthesized a multi-functional, dynamic coating on titanium by co-immobilizing GL13K antimicrobial peptide and an MMP-9 - a matrix metalloproteinase secreted by bone-remodeling osteoclasts - responsive peptide. Our co-immobilized peptide surface showed potent anti-biofilm activity, enabled effective osteoblast and fibroblast proliferation, and demonstrated stability against a mechanical challenge. Finally, we showed peptide release was triggered for up to seven days when the multi-peptide coatings were cultured with MMP-9-secreting osteoclasts. Our MMP-9 cleavable peptide can be conjugated with osteogenic or immunomodulatory motifs for enhanced bone formation in future work. Overall, we envisage our multifunctional, dynamic surface to reduce infection rates of percutaneous bone-anchored devices via strong anti-microbial activity and enhanced tissue regeneration via temporal synchronization between biomaterial cues and tissue responses.

An integrative review on the toxicity of Bisphenol A (BPA) released from resin composites used in dentistry

The main aim of this study was to perform an integrative review on the release of bisphenol A (BPA) from resin-matrix composites and potential toxic effects. A bibliographic search was performed on the PubMed platform using the following keywords: "Bisphenol A" OR "BPA" AND "resin composite" OR "composite resin" AND "toxicity" OR "cytotoxicity" OR "release". Inclusion criteria involved in vitro and in vivo studies on the release and toxicity of BPA. Results highlighted the release of BPA from resin-matrix composites due to insufficient polymerization and/or degradation of the polymeric matrix. BPA is part of the organic matrix of resin-matrix composites and may be hydrolysed in human saliva, although studies report that low doses might not be detected by traditional chemical analysis. Studies exposing zebrafish embryos to different concentrations of Bis-GMA, showed 55% mortality at 10 μM Bis-GMA while 30% mortality was recorded at 1 μM Bis-GMA. In patients, a BPA concentration of around 2.09 × 10^-2 μg/ml was found in the saliva after placement of lingual orthodontic retainers with resin-matrix composites. Also, the BPA molecule can be swallowed and absorbed by the oral/gastrointestinal mucosa, which might result in systemic toxicity. The degradation of resin-matrix composites and release of BPA in oral environment are dependent on the organic matrix content and on the polymerization method. A increased release of BPA can lead to the absorption into oral and gastrointestinal mucosa with high risks of local and systemic toxicity.

The influence of zirconia veneer thickness on the degree of conversion of resin-matrix cements: an integrative review

OBJECTIVE

The main aim of this study was to conduct an integrative review on the influence of the zirconia veneer thickness on the degree of conversion of resin-matrix cements.

MATERIALS AND METHOD

An electronic search was performed on PubMed using a combination of the following search items: zirconia, thickness, veneer, degree of conversion, resin cement, light curing, and polymerization. Articles published in the English language, up to July 2020, were included regarding the influence of ceramic veneer thickness on the degree of conversion of resin-matrix cements. Randomized controlled trials and prospective cohort studies were also evaluated.

RESULTS

Of the 21 selected studies, 9 investigated the light-curing effect, while five other articles evaluated the ceramic translucency. Three studies evaluated the degree of conversion of the resin-matrix cement while four articles assessed the veneer thickness. Results revealed a significant decrease of light transmission through the zirconia with a thickness ranging from 0.1 up to 1.5 mm. However, the ultra-thin thickness around 0.1 and 0.3 mm allowed a full polymerization of the dual-curing resin-matrix cement resulting in the integrity of the interface properties. The light-curing process of resin-matrix cements is also affected by the shade, chemical composition, and microstructure of zirconia and resin cement. Optimal conditions of light-curing are required to reach the threshold intensity of light and energy for polymerization of resin-matrix cements.

CONCLUSIONS

The increase in zirconia veneer thickness negatively affects the degree of conversion of resin-matrix cements. Also, shade and microstructure are key factor to improve the light curing of resin cements.

CLINICAL RELEVANCE

Clinicians should consider the zirconia thickness on resin-based cementation since a higher veneer thickness can negatively affect the light irradiation intensity towards the dual-curing resin-matrix cement. Thus, the degree of conversion of the resin-matrix cement can decrease leading to a low chemical stability (e.g., color instability) and poor mechanical properties.

The Influence of Nanometals, Dispersed in the Electrophoretic Nanohydroxyapatite Coatings on the Ti13Zr13Nb Alloy, on Their Morphology and Mechanical Properties

In this work, nanohydroxyapatite coatings with nanosilver and nanocopper have been fabricated and studied. The presented results concern coatings with a chemical composition that has never been proposed before. The present research aims to characterize the effects of nanosilver and nanocopper, dispersed in nanohydroxyapatite coatings and deposited on a new, non-toxic Ti13Zr13Nb alloy, on the physical and mechanical properties of coatings. The coatings were obtained by a one-stage electrophoretic process. The surface topography, and the chemical and phase compositions of coatings were examined with scanning electron microscopy, atomic force microscopy, X-ray diffractometry, glow discharge optical emission spectroscopy, and energy-dispersive X-ray spectroscopy. The mechanical properties of coatings were determined by nanoindentation tests, while coatings adhesion was determined by nanoscratch tests. The results demonstrate that copper addition increases the hardness and adhesion. The presence of nanosilver has no significant influence on the adhesion of coatings.

Characterization and evaluation of a femtosecond laser-induced osseointegration and an anti-inflammatory structure generated on a titanium alloy

Cell–material interactions during early osseointegration of the bone–implant interface are critical and involve crosstalk between osteoblasts and osteoclasts. The surface properties of titanium implants also play a critical role in cell–material interactions. In this study, femtosecond laser treatment and sandblasting were used to alter the surface morphology, roughness and wettability of a titanium alloy. Osteoblasts and osteoclasts were then cultured on the resulting titanium alloy disks. Four disk groups were tested: a polished titanium alloy (pTi) control; a hydrophilic micro-dislocation titanium alloy (sandblasted Ti (STi)); a hydrophobic nano-mastoid Ti alloy (femtosecond laser-treated Ti (FTi)); and a hydrophilic hierarchical hybrid micro-/nanostructured Ti alloy [femtosecond laser-treated and sandblasted Ti (FSTi)]. The titanium surface treated by the femtosecond laser and sandblasting showed higher biomineralization activity and lower cytotoxicity in simulated body fluid and lactate dehydrogenase assays. Compared to the control surface, the multifunctional titanium surface induced a better cellular response in terms of proliferation, differentiation, mineralization and collagen secretion. Further investigation of macrophage polarization revealed that increased anti-inflammatory factor secretion and decreased proinflammatory factor secretion occurred in the early response of macrophages. Based on the above results, the synergistic effect of the surface properties produced an excellent cellular response at the bone–implant interface, which was mainly reflected by the promotion of early ossteointegration and macrophage polarization.

Synergistic Effect of rhBMP-2 Protein and Nanotextured Titanium Alloy Surface to Improve Osteogenic Implant Properties

One of the major limitations during titanium (Ti) implant osseointegration is the poor cellular interactions at the biointerface. In the present study, the combined effect of recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) and nanopatterned Ti6Al4V fabricated with Directed irradiation synthesis (DIS) is investigated in vitro. This environmentally-friendly plasma uses ions to create self-organized nanostructures on the surfaces. Nanocones (≈36.7 nm in DIS 80°) and thinner nanowalls (≈16.5 nm in DIS 60°) were fabricated depending on DIS incidence angle and observed via scanning electron microscopy. All samples have a similar crystalline structure and wettability, except for sandblasted/acid-etched (SLA) and acid-etched/anodized (Anodized) samples which are more hydrophilic. Biological results revealed that the viability and adhesion properties (vinculin expression and cell spreading) of DIS 80° with BMP-2 were similar to those polished with BMP-2, yet we observed more filopodia on DIS 80° (≈39 filopodia/cell) compared to the other samples (<30 filopodia/cell). BMP-2 increased alkaline phosphatase activity in all samples, tending to be higher in DIS 80°. Moreover, in the mineralization studies, DIS 80° with BMP-2 and Anodized with BMP-2 increased the formation of calcium deposits (>3.3 fold) compared to polished with BMP-2. Hence, this study shows there is a synergistic effect of BMP-2 and DIS surface modification in improving Ti biological properties which could be applied to Ti bone implants to treat bone disease.

Laser surface texturing of zirconia-based ceramics for dental applications: A review

Laser surface texturing is widely explored for modifying the surface topography of various materials and thereby tuning their optical, tribological, biological, and other surface properties. In dentistry, improved osseointegration has been observed with laser textured titanium dental implants in clinical trials. Due to several limitations of titanium materials, dental implants made of zirconia-based ceramics are now considered as one of the best alternatives. Laser surface texturing of zirconia dental implants is therefore attracting increasing attention. However, due to the brittle nature of zirconia, as well as the metastable tetragonal ZrO₂ phase, laser texturing in the case of zirconia is more challenging than in the case of titanium. Understanding these challenges requires different fields of expertise, including laser engineering, materials science, and dentistry. Even though much progress was made within each field of expertise, a comprehensive analysis of all the related factors is still missing. This review paper provides thus an overview of the common challenges and current status on the use of lasers for surface texturing of zirconia-based ceramics for dental applications, including texturing of zirconia implants for improving osseointegration, texturing of zirconia abutments for reducing peri-implant inflammation, and texturing of zirconia restorations for improving restoration retention by bonding.

Correlation between LncRNA Profiles in the Blood Clot Formed on Nano-Scaled Implant Surfaces and Osseointegration

Implant surfaces with a nanoscaled pattern can dominate the blood coagulation process resulting in a defined clot structure and its degradation behavior, which in turn influence cellular response and the early phase of osseointegration. Long non-coding (Lnc) RNAs are known to regulate many biological processes in the skeletal system; however, the link between the LncRNA derived from the cells within the clot and osseointegration has not been investigated to date. Hence, the sequence analysis of LncRNAs expressed within the clot formed on titania nanotube arrays (TNAs) with distinct nano-scaled diameters (TNA 15 of 15 nm, TNA 60 of 60 nm, TNA 120 of 120 nm) on titanium surfaces was profiled for the first time. LncRNA LOC103346307, LOC103352121, LOC108175175, LOC103348180, LOC108176660, and LOC108176465 were identified as the pivotal players in the early formed clot on the nano-scaled surfaces. Further bioinformatic prediction results were used to generate co-expression networks of LncRNAs and mRNAs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed that distinct nano-scaled surfaces could regulate the biological functions of target mRNAs in the clot. LOC103346307, LOC108175175, and LOC108176660 upregulated mRNAs related to cell metabolism and Wnt, TGF-beta, and VEGF signaling pathways in TNA 15 compared with P-Ti, TNA 60, and TNA 120, respectively, whereas LOC103352121, LOC103348180, and LOC108176465 downregulated mRNAs related to bone resorption and inflammation through negatively regulating osteoclast differentiation, TNF, and NF-kappa signaling pathways. The results indicated that surface nano-scaled characteristics can significantly influence the clot-derived LncRNAs expression profile, which affects osseointegration through multiple signaling pathways of the targeted mRNAs, thus paving a way for better interpreting the link between the properties of a blood clot formed on the nano-surface and de novo bone formation.

Nanosurfacing Ti alloy by weak alkalinity-activated solid-state dewetting (AAD) and its biointerfacial enhancement effect

Nanoscale manipulation of material surfaces can create extraordinary properties, holding great potential for modulating the implant-bio interface for enhanced performance. In this study, a green, simple and biocompatible nanosurfacing approach based on weak alkalinity-activated solid-state dewetting (AAD) was for the first time developed to nano-manipulate the Ti6Al4V surface by atomic self-rearrangement. AAD treatment generated quasi-periodic titanium oxide nanopimples with high surface energy. The nanopimple-like nanostructures enhanced the osteogenic activity of osteoblasts, facilitated M2 polarization of macrophages, and modulated the cross-talk between osteoblasts and macrophages, which collectively led to significant strengthening of in vivo bone-implant interfacial bonding. In addition, the titanium oxide nanopimples strongly adhered to the Ti alloy, showing resistance to tribocorrosion damage. The results suggest strong nano-bio interfacial effects, which was not seen for the control Ti alloy processed through traditional thermal oxidation. Compared to other nanostructuring strategies, the AAD technique shows great potential to integrate high-performance, functionality, practicality and scalability for surface modification of medical implants.

Carbon fiber-reinforced PEEK in implant dentistry: A scoping review on the finite element method

Objective: The aim of the present study was to perform an integrative systematic review on the stress distribution assessed by finite element analysis on dental implants or abutments composed of carbon fiber-reinforced PEEK composites.Method: An electronic search was performed on PUBMED and ScienceDirect using a combination of the following search terms: PEEK, Polyetheretherketone, FEA, FEM, Finite element, Stress, Dental implant and Dental abutment.Results: The findings reported mechanical properties and the stress distribution through implant and abutment composed of PEEK and its fiber-reinforced composites. Unfilled PEEK revealed low values of elastic modulus and strength that negatively affected the stress distribution through the abutment and implant towards to the bone tisues. The incorporation of 30% carbon fibers increased the elastic modulus and strength of the PEEK-matrix composites although some studies reported no statistic differences in stress magnitude when compared to unfilled PEEK. However, an increase in short carbon fibers up to 60% revealed an enhancement on the stress distribution through abutment and implants towards to the bone tissues. PEEK veneering onto titanium core structures can also be a strategy to control the stress distribution at the implant-to-bone interface.Conclusions: The stiffness and strength of PEEK-matrix composites can be increased by the improvement of the carbon fibers' network. Thus, the content, shape, dimensions, and chemical composition of fibers are key factors to improve the stress distribution through abutment and implants composed of PEEK-matrix composites.

Osseointegration of a novel dental implant in canine

This study aimed to compare and verify the osseointegration performance of a novel implant (NI) in vivo, which could provide a useful scientific basis for the further development of NIs. Thirty-two NIs treated with hydrofluoric acid and anodization and sixteen control implants (CIs) were placed in the mandibles of 8 beagles. Micro-CT showed that the trabecular number (Tb.N) significantly increased and trabecular separation (Tb.Sp) significantly decreased in the NIs at 2 weeks. Significant differences were found in the trabecular thickness, Tb.N, Tb.Sp, bone surface/bone volume ratio, and bone volume/total volume ratio between the two groups from the 2nd–4th weeks. However, there were no significant differences between the two groups in the bone volume density at 2, 4, 8, or 12 weeks or bone-implant contact at 2 or 4 weeks, but the BIC in the CIs was higher than that in the NIs at the 8th and 12th weeks. Meanwhile, the histological staining showed a similar osseointegration process between the two groups over time. Overall, the NIs could be used as new potential implants after further improvement.

Dental Implants Loaded With Bioactive Agents Promote Osseointegration in Osteoporosis: A Review

Implant-supported dentures are widely used in patients with defect or loss of dentition because these have higher chewing efficiency and do not damage the adjacent teeth compared with fixed or removable denture. An implant-supported denture carries the risk of failure in some systemic diseases, including osteoporosis, because of a non-ideal local microenvironment. Clinically common physical and chemical modifications are used to change the roughness of the implant surface to promote osseointegration, but they have limitations in promoting osteoinduction and inhibiting bone resorption. Recently, many researchers have focused on the study of bioactive modification of implants and have achieved promising results. Herein we have summarized the progress in bioactive modification strategy to promote osseointegration by regulating the local osteoporotic microenvironment.

Bioactive Coatings Based on Hydroxyapatite, Kanamycin, and Growth Factor for Biofilm Modulation

The occurrence of opportunistic local infections and improper integration of metallic implants results in severe health conditions. Protective and tunable coatings represent an attractive and challenging selection for improving the metallic devices' biofunctional performances to restore or replace bone tissue. Composite materials based on hydroxyapatite (HAp), Kanamycin (KAN), and fibroblast growth factor 2 (FGF2) are herein proposed as multifunctional coatings for hard tissue implants. The superior cytocompatibility of the obtained composite coatings was evidenced by performing proliferation and morphological assays on osteoblast cell cultures. The addition of FGF2 proved beneficial concerning the metabolic activity, adhesion, and spreading of cells. The KAN-embedded coatings exhibited significant inhibitory effects against bacterial biofilm development for at least two days, the results being superior in the case of Gram-positive pathogens. HAp-based coatings embedded with KAN and FGF2 protein are proposed as multifunctional materials with superior osseointegration potential and the ability to reduce device-associated infections.

Optimizing citric acid protocol to control implant-related infections: An in vitro and in situ study

OBJECTIVE

The present study aimed to establish an optimized protocol for biofilm removal from titanium (Ti) surfaces using citric acid (CA) solutions.

BACKGROUND

Biofilm accumulation is the main factor to trigger peri-implant infections and to increase the risk of treatment failures. Although CA has been suggested as the anti-infective agent with highest potential for biofilm removal on Ti, there is no consensus that CA could improve the anti-infective treatment and its effect.

METHODS

Physical and chemical alterations, electrochemical behavior, cytotoxicity, and antimicrobial effect of CA on Ti discs were evaluated using four concentrations (1, 10, 20, and 40%) and two application methods (immersion and rubbing). Negative control using 0.9% NaCl was used in all experiments. To evaluate whether different application times can have similar response, polymicrobial biofilm (microcosm model) was formed on Ti and treated with CA for 1, 2, 4, and 8 min. An in situ study was conducted to verify whether the established protocol is equally effective in biofilms formed on machined and sandblasted, large-grit, and acid-etched (SLA) Ti surfaces.

RESULTS

CA 40% induced significantly higher surface alterations observed by confocal images and profilometry. In general, rubbing protocol decreased the surface roughness and increased the wettability (p < 0.05), exhibiting better surface cleaning by biofilm removal. CA 10% presented no indirect cytotoxicity and, when applied by rubbing for 8 min, presented proper in vitro antibacterial action and potential corrosion inhibition. When CA 10% was rubbed on Ti surfaces for 4 min, it displayed optimum cleaning ability as 8 min, working equally to remove in situ biofilm on machined and SLA surfaces.

CONCLUSIONS

The application of CA 10% by rubbing for at least 4 min demonstrated to be a promising protocol to eliminate biofilms formed in smooth and rougher surfaces, which could improve implant-related infection therapies.

Nanostructured Coating of Non-Crystalline Tantalum Pentoxide on Polyetheretherketone Enhances RBMS Cells/HGE Cells Adhesion

PURPOSE

As a dental material, polyetheretherketone (PEEK) is bioinert that does not induce cellular response and bone/gingival tissues regeneration. This study was to develop bioactive coating on PEEK and investigate the effects of coating on cellular response.

MATERIALS AND METHODS

Tantalum pentoxide (TP) coating was fabricated on PEEK surface by vacuum evaporation and responses of rat bone marrow mesenchymal stem (RBMS) cells/human gingival epithelial (HGE) were studied.

RESULTS

A dense coating (around 400 nm in thickness) of TP was closely combined with PEEK (PKTP). Moreover, the coating was non-crystalline TP, which contained many small humps (around 10 nm in size), exhibiting a nanostructured surface. In addition, the roughness, hydrophilicity, surface energy, and protein adsorption of PKTP were remarkably higher than that of PEEK. Furthermore, the responses (adhesion, proliferation, and osteogenic gene expression) of RBMS cells, and responses (adhesion and proliferation) of HGE cells to PKTP were remarkably improved in comparison with PEEK. It could be suggested that the nanostructured coating of TP on PEEK played crucial roles in inducing the responses of RBMS/HGE cells.

CONCLUSION

PKTP with elevated surface performances and outstanding cytocompatibility might have enormous potential for dental implant application.

Micro-Nano Surface Characterization and Bioactivity of a Calcium Phosphate-Incorporated Titanium Implant Surface

The surface topography of dental implants and micro-nano surface characterization have gained particular interest for the improvement of the osseointegration phases. The aim of this study was to evaluate the surface micro-nanomorphology and bioactivity (apatite forming ability) of Ossean^® surface, a resorbable blast medium (RBM) blasted surface further processed through the incorporation of a low amount of calcium phosphate. The implants were analyzed using environmental scanning electronic microscopy (ESEM), connected to Energy dispersive X-ray spectroscopy (EDX), field emission gun SEM-EDX (SEM-FEG) micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after immersion in weekly refreshed Hank’s balanced salt solution (HBSS) for 28 days. The analysis of the samples before immersion showed a moderately rough surface, with micropits and microgrooves distributed on all of the surface; EDX microanalysis revealed the constitutional elements of the implant surface, namely titanium (Ti), aluminum (Al) and vanadium (V). Limited traces of calcium (Ca) and phosphorous (P) were detected, attributable to the incorporated calcium phosphate. No traces of calcium phosphate phases were detected by micro-Raman spectroscopy. ESEM analysis of the implant aged in HBSS for 28 days revealed a significantly different surface, compared to the implant before immersion. At original magnifications <2000×, a homogeneous mineral layer was present on all the surface, covering all the pits and microgrooves. At original magnifications ≥10,000×, the mineral layer revealed the presence of small microspherulites. The structure of these spherulites (approx. 2 µm diameter) was observed in nanoimmersion mode revealing a regular shape with a hairy-like contour. Micro-Raman analysis showed the presence of B-type carbonated apatite on the implant surface, which was further confirmed by XPS analysis. This implant showed a micro-nano-textured surface supporting the formation of a biocompatible apatite when immersed in HBSS. These properties may likely favor bone anchorage and healing by stimulation of mineralizing cells.

Tanfloc/heparin polyelectrolyte multilayers improve osteogenic differentiation of adipose-derived stem cells on titania nanotube surfaces

In this study, a surface modification strategy using natural biopolymers on titanium is proposed to improve bone healing and promote rapid and successful osseointegration of orthopedic implants. Titania nanotubes were fabricated via an anodization process and the surfaces were further modified with polyelectrolyte multilayers (PEMs) based on Tanfloc (a cationic tannin derivative) and glycosaminoglycans (heparin and hyaluronic acid). Scanning electron microscopy (SEM), water contact angle measurements, and X-ray photoelectron spectroscopy were used to characterize the surfaces. Adipose-derived stem cells (ADSCs) were seeded on the surfaces, and the cell viability, adhesion, and proliferation were investigated. Osteogenesis was induced and osteogenic differentiation of human ADSCs on the surfaces was evaluated via mineralization and protein expression assays, immunofluorescent staining, and SEM. The Tanfloc/heparin PEMs on titania nanotubes improved the rate of osteogenic differentiation of ADSCs as well as the bone mineral deposition, and is therefore a promising approach for use in orthopedic implants.

Effects of Surface Modification on Adsorption Behavior of Cell and Protein on Titanium Surface by Using Quartz Crystal Microbalance System

Primary stability and osseointegration are major challenges in dental implant treatments, where the material surface properties and wettability are critical in the early formation of hard tissue around the implant. In this study, a quartz crystal microbalance (QCM) was used to measure the nanogram level amount of protein and bone marrow cells adhered to the surfaces of titanium (Ti) surface in real time. The effects of ultraviolet (UV) and atmospheric-pressure plasma treatment to impart surface hydrophilicity to the implant surface were evaluated. The surface treatment methods resulted in a marked decrease in the surface carbon (C) content and increase in the oxygen (O) content, along with super hydrophilicity. The results of QCM measurements showed that adhesion of both adhesive proteins and bone marrow cells was enhanced after surface treatment. Although both methods produced implants with good osseointegration behavior and less reactive oxidative species, the samples treated with atmospheric pressure plasma showed the best overall performance and are recommended for clinical use. It was verified that QCM is an effective method for analyzing the initial adhesion process on dental implants.

3D Printed Ti-6Al-4V Implant with a Micro/Nanostructured Surface and Its Cellular Responses

Three-dimensional (3D) printing technology has been proved to be a powerful tool for the free-form fabrication of titanium (Ti) implants. However, the surface quality of 3D printed Ti implants is not suitable for clinical application directly. Therefore, surface modification of 3D printed Ti implants is required in order to achieve good biocompatibility and osseointegration. In this study, a novel surface modification method of 3D printed Ti-6Al-4V implants has been proposed, which combined acid etching with hydrothermal treatment to construct micro/nanostructures. Polished TC4 sheets (P), electron beam melting Ti sheets (AE), and micro/nanostructured Ti sheets (AMH) were used in this study to evaluate the effects of different surface morphologies on cellular responses. The surface morphology and 3D topography after treatment were detected via scanning electron microscopy and laser scanning microscopy. The results illustrated that a hierarchical structure comprising micro-valleys and nanowires with a surface roughness of 14.388 μm was successfully constructed. Compared with group P samples, the hydrophilicity of group AMH samples significantly increased with a reduced water contact angle from 54.9° to 4.5°. Cell culture experiments indicated that the micro/nanostructures on the material surface could enhance the cell adhesion and proliferation of MC3T3s. The microstructure could enhance bone-to-implant contact, and the nanostructure could directly interact with some cell membrane receptors. Overall, this study proposes a new strategy to construct micro/nanostructures on the surface of 3D printed Ti-6Al-4V implants and may further serve as a potential modification method for better osteogenesis ability.

Cyclic Oxidation of Titanium Grade 2

This paper presents the results of research into the cyclic oxidation of titanium Grade 2. The value of titanium Grade 2 oxidation activation energy was determined based on an analysis of the Arrhenius diagram. The result was 205.3 kJ/mol. After cyclic oxidation at a temperature of 600 °C, the presence of oxides in an acicular system was observed on the surface. The specimen surface after oxidation at 650 °C was characterised by the presence of fine oxide particles, while after oxidation at 700 °C, the obtained oxide layer was composed of large oxide particles. The layers obtained after oxidation at 600 °C had the lowest thickness (1.26 and 2.12 µm), while those obtained at 700 °C had the highest thickness (5.17 and 9.45 µm). Examination of the phase composition after cyclic oxidation showed that the oxide layers obtained at temperatures of 600, 650 and 700 °C were composed of TiO₂ (rutile) only. No presence of other phases was found. The oxide layers formed in the cyclic oxidation process were characterised by different thicknesses, depending on the oxidation parameters. It was found that cyclic oxidation contributed to a considerable increase in the surface hardness of titanium Grade 2.

Protein repellent anti-coagulative mixed-charged cellulose derivative coatings

This study describes the formation of cellulose based polyelectrolyte charge complexes on the surface of biodegradable polycaprolactone (PCL) thin films. Anionic sulphated cellulose (CS) and protonated cationic amino cellulose (AC) were used to form these complexes with a layer-by-layer coating technique. Both polyelectrolytes were analyzed by charge titration methods to elucidate their pH-value dependent protonation behavior. A quartz crystal microbalance with dissipation (QCM-D) in combination with X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to follow the growth, stability and water content of up to three AC/CS bi-layers in aqueous environment. This was combined with coagulation studies on one, two and three bilayers of AC/CS, measuring the thrombin formation rate and the total coagulation time of citrated blood plasma with QCM-D. Stable mixed charged bilayers could be prepared on PCL and significantly higher masses of AC than of CS were present in these complexes. Strong hydration due to the presence of ammonium and sulphate substituents on the backbone of cellulose led to a significant BSA repellent character of three bilayers of AC/CS coatings. The total plasma coagulation time was increased in comparison to neat PCL, indicating an anticoagulative nature of the coatings. Surprisingly, a coating solely composed of an AC layer significantly prolonged the total coagulation time on the surfaces although it did not prevent fibrinogen deposition. It is suggested that these cellulose derivative-based coatings can therefore be used to prevent unwanted BSA deposition and fibrin clot formation on PCL to foster its biomedical application.

Impacts of a Nano-Laponite Ceramic on Surface Performance, Apatite Mineralization, Cell Response, and Osseointegration of a Polyimide-Based Biocomposite

INTRODUCTION

Polyimide (PI) exhibits good biocompatibility and high mechanical strength, but biological inertness that does not stimulate bone regeneration, while laponite possesses excellent bioactivity.

METHODS

In this study, to improve the bioactivity of PI, nano-laponite ceramic (LC)-PI composites (LPCs) were fabricated by melt processing as implantable materials for bone repair.

RESULTS

The compressive strength, hydrophilicity, and surface roughness of LPCs with 40 w% LC content (LPC40s) were higher than LPC20s, and LPC20s higher than pure PI. In addition, no apatite mineralization occurred on PI, while apatite mineralized on LPCs in simulated body fluid. Compared with LPC20, more apatite deposited on LPC40, indicating good bioactivity. Moreover, the adhesion, proliferation, and alkaline phosphatase activity of rat bone mesenchymal stem cells on LPCs significantly increased with LC content increasing in vitro. Furthermore, the evaluations of animal experiments (micro-CT, histology, and pushout load) revealed that compared with LPC20 and PI, LPC40 significantly enhanced osteogenesis and osseointegration in vivo.

DISCUSSION

Incorporation of LC into PI obviously improved not only surface physicochemical properties but also biological properties of LPCs. LPC40 with high LC content displayed good biocompatibility and bioactivity, which markedly promoted osteogenesis and osseointegration. Therefore, with its superior biocompatibility and bioactivity, LPC40 could be an alternative candidate as an implant for orthopedic applications.

Surface Modification Techniques of Titanium and its Alloys to Functionally Optimize Their Biomedical Properties: Thematic Review

Depending on the requirements of specific applications, implanted materials including metals, ceramics, and polymers have been used in various disciplines of medicine. Titanium and its alloys as implant materials play a critical role in the orthopedic and dental procedures. However, they still require the utilization of surface modification technologies to not only achieve the robust osteointegration but also to increase the antibacterial properties, which can avoid the implant-related infections. This article aims to provide a summary of the latest advances in surface modification techniques, of titanium and its alloys, specifically in biomedical applications. These surface techniques include plasma spray, physical vapor deposition, sol-gel, micro-arc oxidation, etc. Moreover, the microstructure evolution is comprehensively discussed, which is followed by enhanced mechanical properties, osseointegration, antibacterial properties, and clinical outcomes. Future researches should focus on the combination of multiple methods or improving the structure and composition of the composite coating to further enhance the coating performance.

Hyaluronic acid as a bioactive component for bone tissue regeneration: Fabrication, modification, properties, and biological functions

Hyaluronic acid (HA) is widely distributed in the human body, and it is heavily involved in many physiological functions such as tissue hydration, wound repair, and cell migration. In recent years, HA and its derivatives have been widely used as advanced bioactive polymers for bone regeneration. Many medical products containing HA have been developed because this natural polymer has been proven to be nontoxic, noninflammatory, biodegradable, and biocompatible. Moreover, HA-based composite scaffolds have shown good potential for promoting osteogenesis and mineralization. Recently, many HA-based biomaterials have been fabricated for bone regeneration by combining with electrospinning and 3D printing technology. In this review, the polymer structures, processing, properties, and applications in bone tissue engineering are summarized. The challenges and prospects of HA polymers are also discussed.

Hydrothermally grown TiO2-nanorods on surface mechanical attrition treated Ti: Improved corrosion fatigue and osteogenesis

Current bioactive modifications of Ti-based materials for promoting osteogenesis often decrease corrosion fatigue strength (σ_cf) of the resultant implants, thereby shortening their service lifespan. To solve this issue and accelerate the osteogenesis process, in the present study, a TiO₂ nanorods (TNR)-arrayed coating was hydrothermally grown on optimal surface mechanical attrition treated (SMATed) titanium (S-Ti). The microstructure, bond integrity, residual stress distribution, and corrosion fatigue of TNR-coated S-Ti (TNR/S-Ti) and the response of macrophages and bone marrow-derived mesenchymal stem cells (BMSCs) to TNR/S-Ti were investigated and compared with those of mechanically polished Ti (P-Ti), S-Ti, and TNR-coated P-Ti (TNR/P-Ti). S-Ti showed a nanograined layer and an underlying grain-deformed region with residual compressive stress, which was sustained even when it was hydrothermally coated with TNR. TNR on S-Ti showed nanotopography, composition, and bond strength almost identical to those of P-Ti. While TNR/P-Ti showed a considerable decrease in σ_cf compared to P-Ti, TNR/S-Ti exhibited an improved σ_cf which was even higher than that of P-Ti. Biologically, TNR/S-Ti enhanced adhesion, differentiation, and mineralization of BMSCs, and it also promoted adhesion and M1-to-M2 transition of macrophages as compared to S-Ti and P-Ti. With rapid phenotype switch of macrophages, the level of proinflammatory cytokines decreased, while anti-inflammatory cytokines were upregulated. In co-culture conditions, the migration, differentiation, and mineralization of BMSCs were enhanced by increased level of secretion factors of macrophages on TNR/S-Ti. The modified structure accelerated bone apposition in rabbit femur and is expected to induce a favorable immune microenvironment to facilitate osseointegration earlier; it can also simultaneously improve corrosion fatigue resistance of Ti-based implants and thereby enhance their service life.

Novel Bionic Topography with MiR-21 Coating for Improving Bone-Implant Integration through Regulating Cell Adhesion and Angiogenesis

Implant loosening is still the major form of the failure of artificial joints. Herein, inspired by the operculum of the river snail, we prepared a novel bionic micro/nanoscale topography on a titanium surface. This bionic topography promoted early cell adhesion through up-regulating the expression of ITG α5β1 and thus accelerated the following cell spreading, proliferation, and differentiation. Moreover, a miR-21 coating, which promoted the angiogenic differentiation of MSCs, was fabricated on the bionic topography. Benefiting from both bionic micro/nanoscale topography and miR-21, blood vessel growth and bone formation and mineralization around the implant, as well as bone-implant bonding strength, were significantly improved. Collectively, the present study highlights the combination of the bionic micro/nanoscale topography and miR-21 on promoting cell adhesion and angiogenic differentiation and improving in vivo angiogenesis and bone-implant osseointegration. This work provides a new train of thought propelling the development of implants for potential application in the orthopedics field.

Harnessing biomolecules for bioinspired dental biomaterials

Dental clinicians have relied for centuries on traditional dental materials (polymers, ceramics, metals, and composites) to restore oral health and function to patients. Clinical outcomes for many crucial dental therapies remain poor despite many decades of intense research on these materials. Recent attention has been paid to biomolecules as a chassis for engineered preventive, restorative, and regenerative approaches in dentistry. Indeed, biomolecules represent a uniquely versatile and precise tool to enable the design and development of bioinspired multifunctional dental materials to spur advancements in dentistry. In this review, we survey the range of biomolecules that have been used across dental biomaterials. Our particular focus is on the key biological activity imparted by each biomolecule toward prevention of dental and oral diseases as well as restoration of oral health. Additional emphasis is placed on the structure-function relationships between biomolecules and their biological activity, the unique challenges of each clinical condition, limitations of conventional therapies, and the advantages of each class of biomolecule for said challenge. Biomaterials for bone regeneration are not reviewed as numerous existing reviews on the topic have been recently published. We conclude our narrative review with an outlook on the future of biomolecules in dental biomaterials and potential avenues of innovation for biomaterial-based patient oral care.