Surface roughness mediates its effects on osteoblasts via protein kinase A and phospholipase A2

A study on the effect of bioactive glass and hydroxyapatite-loaded Xanthan dialdehyde-based composite coatings for potential orthopedic applications

The most important challenge faced in designing orthopedic devices is to control the leaching of ions from the substrate material, and to prevent biofilm formation. Accordingly, the surgical grade stainless steel (316L SS) was electrophoretically deposited with functional composition of biopolymers and bioceramics. The composite coating consisted of: Bioglass (BG), hydroxyapatite (HA), and lawsone, that were loaded into a polymeric matrix of Xanthan Dialdehyde/Chondroitin Sulfate (XDA/CS). The parameters and final composition for electrophoretic deposition were optimized through trial-and-error approach. The composite coating exhibited significant adhesion strength of "4B" (ASTM D3359) with the substrate, suitable wettability of contact angle 48°, and an optimum average surface roughness of 0.32 µm. Thus, promoting proliferation and attachment of bone-forming cells, transcription factors, and proteins. Fourier transformed infrared spectroscopic analysis revealed a strong polymeric network formation between XDA and CS. scanning electron microscopy and energy dispersive X-ray spectroscopy analysis displayed a homogenous surface with invariable dispersion of HA and BG particles. The adhesion, hydrant behavior, and topography of said coatings was optimal to design orthopedic implant devices. The said coatings exhibited a clear inhibition zone of 21.65 mm and 21.04 mm with no bacterial growth against Staphylococcus aureus (S. Aureus) and Escherichia coli (E. Coli) respectively, confirming the antibacterial potential. Furthermore, the crystals related to calcium (Ca) and HA were seen after 28 days of submersion in simulated body fluid. The corrosion current density, of the above-mentioned coating was minimal as compared to the bare 316L SS substrate. The results infer that XDA/CS/BG/HA/lawsone based composite coating can be a candidate to design coatings for orthopedic implant devices.

Osteoblastic and Bacterial Response of Hybrid Dental Implants

Bacterial infections in dental implants generate peri-implantitis disease that causes bone loss and the mobility of the dental implant. It is well known that specific ranges of roughness favor the proliferation of bacteria, and it is for this reason that new dental implants called hybrids have appeared. These implants have a smooth area in the coronal part and a rough surface in the apical part. The objective of this research is the physico-chemical characterization of the surface and the osteoblastic and microbiological behavior. One-hundred and eighty discs of titanium grade 3 with three different surfaces (smooth, smooth-rough, and completely rough) were studied. The roughness was determined by white light interferometry, and the wettability and surface energy by the sessile drop technique and the application of Owens and Wendt equations. Human osteoblast SaOS-2 was cultured to determine cell adhesion, proliferation, and differentiation. Microbiological studies were performed with two common bacterial strains in oral infection, E. faecalis and S. gordonii, at different times of culture. The roughness obtained for the smooth surface was Sa = 0.23 and for the rough surface it was 1.98 μm. The contact angles were more hydrophilic for the smooth surface (61.2°) than for the rough surface (76.1°). However, the surface energy was lower for the rough surface (22.70 mJ/m²) in both its dispersive and polar components than the smooth surface (41.77 mJ/m²). Cellular activity in adhesion, proliferation, and differentiation was much higher on rough surfaces than on smooth surfaces. After 6 h of incubation, the osteoblast number in rough surfaces was more than 32% higher in relation to the smooth surface. The cell area in smooth surfaces was higher than rough surfaces. The proliferation increased and the alkaline phosphatase presented a maximum after 14 days, with the mineral content of the cells being higher in rough surfaces. In addition, the rough surfaces showed greater bacterial proliferation at the times studied and in the two strains used. Hybrid implants sacrifice the good osteoblast behavior of the coronal part of the implant in order to obstruct bacterial adhesion. The following fact should be considered by clinicians: there is a possible loss of bone fixation when preventing peri-implantitis.

Relevant Aspects of Titanium Topography for Osteoblastic Adhesion and Inhibition of Bacterial Colonization

The influence of the surface topography of dental implants has been studied to optimize titanium surfaces in order to improve osseointegration. Different techniques can be used to obtain rough titanium, however, their effect on wettability, surface energy, as well as bacterial and cell adhesion and differentiation has not been studied deeply. Two-hundred disks made of grade 4 titanium were subjected to different treatments: machined titanium (MACH), acid-attacked titanium (AE), titanium sprayed with abrasive alumina particles under pressure (GBLAST), and titanium that has been treated with GBLAST and then subjected to AE (GBLAST + AE). The roughness of the different treatments was determined by confocal microscopy, and the wettability was determined by the sessile drop technique; then, the surface energy of each treatment was calculated. Osteoblast-like cells (SaOs-2) were cultured, and alkaline phosphatase was determined using a colorimetric test. Likewise, bacterial strains S. gordonii, S. oralis, A. viscosus, and E. faecalis were cultured, and proliferation on the different surfaces was determined. It could be observed that the roughness of the GBLAST and GBLAS + AE was higher, at 1.99 and 2.13 μm of Ra, with respect to the AE and MACH samples, which were 0.35 and 0.20 μm, respectively. The abrasive treated surfaces showed lower hydrophilicity but lower surface energy. Significant differences could be seen at 21 days between SaOS-2 osteoblastic cell adhesion for the blasted ones and higher osteocalcin levels. However, no significant differences in terms of bacterial proliferation were observed between the four surfaces studied, demonstrating the insensitivity of bacteria to topography. These results may help in the search for the best topographies for osteoblast behavior and for the inhibition of bacterial colonization.

Osteoblastic Cell Behavior and Gene Expression Related to Bone Metabolism on Different Titanium Surfaces

The surface topography of titanium dental implants has a great influence on osseointegration. In this work, we try to determine the osteoblastic behavior and gene expression of cells with different titanium surfaces and relate them to the physicochemical properties of the surface. For this purpose, we have used commercial titanium discs of grade 3: as-received corresponds to machined titanium without any surface treatment (MA), chemically acid etched (AE), treated via sand blasting with Al₂O₃ particles (SB) and a sand-blasting treatment with acid etching (SB+AE). The surfaces have been observed using scanning electron microscopy (SEM) and the roughness, wettability and surface energy with dispersive and polar components have been characterized. Osteoblastic cultures were performed with SaOS-2 osteoblastic cells determining cell viability as well as alkaline phosphatase levels for 3 and 21 days, and osteoblastic gene expression was determined. The roughness values of the MA discs was 0.02 μm, which increases to 0.3 μm with acid attack and becomes the maximum for the sand-blasted samples, reaching values of 1.2 μm for SB and SB+AE. The hydrophilic behavior of the MA and AE samples with contact angles of 63° and 65° is superior to that of the rougher samples, being 75° for SB and 82° for SB+AE. In all cases, they show good hydrophilicity. GB and GB+AE surfaces present a higher polar component in the surface energy values, 11.96 and 13.18 mJ/m², respectively, than AE and MA, 6.64 and 9.79 mJ/m², respectively. The osteoblastic cell viability values at three days do not show statistically significant differences between the four surfaces. However, the viability of the SB and SB+AE surfaces at 21 days is much higher than that of the AE and MA samples. From the alkaline phosphatase studies, higher values were observed for those treated with sand blasting with and without acid etching compared to the other two surfaces, indicating a greater activity in osteoblastic differentiation. In all cases except in the Osterix (Ostx) -osteoblast-specific transcription factor-a decrease in gene expression is observed in relation to the MA samples (control). The most important increase was observed for the SB+AE condition. A decrease in the gene expression of Osteoprotegerine (OPG), Runt-related transcription factor 2 (Runx2), Receptor Activator of NF-κB Ligand (RANKL) and Alkaline Phosphatase (Alp) genes was observed in the AE surface.

Strategies to Mitigate and Treat Orthopaedic Device-Associated Infections

Orthopaedic device implants play a crucial role in restoring functionality to patients suffering from debilitating musculoskeletal diseases or to those who have experienced traumatic injury. However, the surgical implantation of these devices carries a risk of infection, which represents a significant burden for patients and healthcare providers. This review delineates the pathogenesis of orthopaedic implant infections and the challenges that arise due to biofilm formation and the implications for treatment. It focuses on research advancements in the development of next-generation orthopaedic medical devices to mitigate against implant-related infections. Key considerations impacting the development of devices, which must often perform multiple biological and mechanical roles, are delineated. We review technologies designed to exert spatial and temporal control over antimicrobial presentation and the use of antimicrobial surfaces with intrinsic antibacterial activity. A range of measures to control bio-interfacial interactions including approaches that modify implant surface chemistry or topography to reduce the capacity of bacteria to colonise the surface, form biofilms and cause infections at the device interface and surrounding tissues are also reviewed.

Biominerals Added Bioresorbable Calcium Phosphate Loaded Biopolymer Composites

Nanocrystalline calcium phosphate (CP) bioceramic coatings and their combination with biopolymers are innovative types of resorbable coatings for load-bearing implants that can promote the integration of metallic implants into human bodies. The nanocrystalline, amorphous CP particles are an advantageous form of the various calcium phosphate phases since they have a faster dissolution rate than that of crystalline hydroxyapatite. Owing to the biomineral additions (Mg, Zn, Sr) in optimized concentrations, the base CP particles became more similar to the mineral phase in human bones (dCP). The effect of biomineral addition into the CaP phases was thoroughly studied. The results showed that the shape, morphology, and amorphous characteristic slightly changed in the case of biomineral addition in low concentrations. The optimized dCP particles were then incorporated into a chosen polycaprolactone (PCL) biopolymer matrix. Very thin, non-continuous, rough layers were formed on the surface of implant substrates via the spin coating method. The SEM elemental mapping proved the perfect incorporation and distribution of dCP particles into the polymer matrix. The bioresorption rate of thin films was followed by corrosion measurements over a long period of time. The corrosion results indicated a faster dissolution rate for the dCP-PCL composite compared to the dCP and CP powder layers.

Scaffold Pore Curvature Influences ΜSC Fate through Differential Cellular Organization and YAP/TAZ Activity

Tissue engineering aims to repair, restore, and/or replace tissues in the human body as an alternative to grafts and prostheses. Biomaterial scaffolds can be utilized to provide a three-dimensional microenvironment to facilitate tissue regeneration. Previously, we reported that scaffold pore size influences vascularization and extracellular matrix composition both in vivo and in vitro, to ultimately influence tissue phenotype for regenerating cranial suture and bone tissues, which have markedly different tissue properties despite similar multipotent stem cell populations. To rationally design biomaterials for specific cell and tissue fate specification, it is critical to understand the molecular processes governed by cell-biomaterial interactions, which guide cell fate specification. Building on our previous work, in this report we investigated the hypothesis that scaffold pore curvature, the direct consequence of pore size, modulates the differentiation trajectory of mesenchymal stem cells (MSCs) through alterations in the cytoskeleton. First, we demonstrated that sufficiently small pores facilitate cell clustering in subcutaneous explants cultured in vivo, which we previously reported to demonstrate stem tissue phenotype both in vivo and in vitro. Based on this observation, we cultured cell-scaffold constructs in vitro to assess early time point interactions between cells and the matrix as a function of pore size. We demonstrate that principle curvature directly influences nuclear aspect and cell aggregation in vitro. Scaffold pores with a sufficiently low degree of principle curvature enables cell differentiation; pharmacologic inhibition of actin cytoskeleton polymerization in these scaffolds decreased differentiation, indicating a critical role of the cytoskeleton in transducing cues from the scaffold pore microenvironment to the cell nucleus. We fabricated a macropore model, which allows for three-dimensional confocal imaging and demonstrates that a higher principle curvature facilitates cell aggregation and the formation of a potentially protective niche within scaffold macropores which prevents MSC differentiation and retains their stemness. Sufficiently high principle curvature upregulates yes-associated protein (YAP) phosphorylation while decreased principle curvature downregulates YAP phosphorylation and increases YAP nuclear translocation with subsequent transcriptional activation towards an osteogenic differentiation fate. Finally, we demonstrate that the inhibition of the YAP/TAZ pathway causes a defect in differentiation, while YAP/TAZ activation causes premature differentiation in a curvature-dependent way when modulated by verteporfin (VP) and 1-oleyl-lysophosphatidic acid (LPA), respectively, confirming the critical role of biomaterials-mediated YAP/TAZ signaling in cell differentiation and fate specification. Our data support that the principle curvature of scaffold macropores is a critical design criterion which guides the differentiation trajectory of mesenchymal stem cells’ scaffolds. Biomaterial-mediated regulation of YAP/TAZ may significantly contribute to influencing the regenerative outcomes of biomaterials-based tissue engineering strategies through their specific pore design.

Fractal Dimension and Texture Analysis in the Assessment of Experimental Laser-Induced Periodic Surface Structures (LIPSS) Dental Implant Surface-In Vitro Study Preliminary Report

Laser-induced periodic surface structures (LIPSS) are the sub-wavelength periodic nanostructures generated by the femtosecond laser. Implant topography and its nanostructural changes can be important for biomedical applications. In order to compare the surface topography of different implants, appropriate mathematical and physical descriptive methods should be provided. The aim of the study was to evaluate the experimental LIPSS-based—Low Spatial Frequency LIPSS (LSFL) dental implant surfaces. Novel methods of surface analysis, such as Fractal Dimension Analysis and Texture Analysis, were compared to the standard surface roughness evaluation. Secondary, cell viability, and attachment tests were applied in order to evaluate the biological properties of the new titanium surface and to compare their correlation with the physical properties of the new surfaces. A Normal Human Dermal Fibroblast (NHDF) cytotoxicity test did not show an impact on the vitality of the cells. Our study has shown that the laser LIPSS implant surface modifications significantly improved the cell adhesion to the tested surfaces. We observed a strong correlation of adhesion and the growth of cells on the tested surface, with an increase in implant surface roughness with the best results for the moderately rough (2 μm) surfaces. Texture and fractal dimension analyses are promising methods to evaluate dental implants with complex geometry.

Bone and Cartilage Interfaces With Orthopedic Implants: A Literature Review

The interface between a surgical implant and tissue consists of a complex and dynamic environment characterized by mechanical and biological interactions between the implant and surrounding tissue. The implantation process leads to injury which needs to heal over time and the rapidity of this process as well as the property of restored tissue impact directly the strength of the interface. Bleeding is the first and most relevant step of the healing process because blood provides growth factors and cellular material necessary for tissue repair. Integration of the implants placed in poorly vascularized tissue such as articular cartilage is, therefore, more challenging than compared with the implants placed in well-vascularized tissues such as bone. Bleeding is followed by the establishment of a provisional matrix that is gradually transformed into the native tissue. The ultimate goal of implantation is to obtain a complete integration between the implant and tissue resulting in long-term stability. The stability of the implant has been defined as primary (mechanical) and secondary (biological integration) stability. Successful integration of an implant within the tissue depends on both stabilities and is vital for short- and long-term surgical outcomes. Advances in research aim to improve implant integration resulting in enhanced implant and tissue interface. Numerous methods have been employed to improve the process of modifying both stability types. This review provides a comprehensive discussion of current knowledge regarding implant-tissue interfaces within bone and cartilage as well as novel approaches to strengthen the implant-tissue interface. Furthermore, it gives an insight into the current state-of-art biomechanical testing of the stability of the implants. Current knowledge reveals that the design of the implants closely mimicking the native structure is more likely to become well integrated. The literature provides however several other techniques such as coating with a bioactive compound that will stimulate the integration and successful outcome for the patient.

Osteogenic activity of a titanium surface modified with silicon-doped titanium dioxide

Titanium and its alloys are the most widely used implants in clinical practice. However, their bioactivity is unsatisfactory, and the effect of osteogenesis on the bonding interface between the implant and bone needs to be further improved. In this study, a coating consisting of microporous titanium doped with silicon (Si-TiO₂) was successfully created by microarc oxidation (MAO), and Si was evenly distributed on the surface of the coating. The surface morphology, roughness, and phase composition of the Si-TiO₂ microporous coating were similar to those of the Si-free doped MAO coatings. The Si-TiO₂ microporous coating can promote osteoblast adhesion, spreading, proliferation and differentiation. More importantly, the integrin β1-FAK signaling pathway may be involved in the regulatory effect of the coating on osteoblasts. Further studies in vivo indicated that the Si-TiO₂ microporous coating could improve early stage osseointegration. In conclusion, the Si-TiO₂ microporous coating is a feasible way to improve the osteogenic abilities of Ti implants to potentially promote clinical performance.

Laser-Based Hybrid Manufacturing of Endosseous Implants: Optimized Titanium Surfaces for Enhancing Osteogenic Differentiation of Human Mesenchymal Stem Cells

Additive manufacturing (AM) is becoming increasingly important in the orthopedic and dental sectors thanks to two major advantages: the possibility of custom manufacturing and the integration of complex structures. However, at smaller scales, surface conditions of AM products are not mastered. Numerous non-fused powder particles give rise to roughness values (Sa) greater than 10 μm, thus limiting biomedical applications since the surface roughness of, e.g., metal implants plays a major role in the quality and rate of osseointegration. In this study, an innovative hybrid machine combining AM and a femtosecond laser (FS) was used to obtain Ti6Al4V parts with biofunctional surfaces. During the manufacturing process, the FS laser beam "neatly" ablates the surface, leaving in its path nanostructures created by the laser/matter interaction. This step decreases the Sa from 11 to 4 μm and increases the surface wettability. The behavior of human mesenchymal stem cells was evaluated on these new AM+FS surfaces and compared with that on AM surfaces and also on polished surfaces. The number of cells attached 24 h after plating is equivalent on all surfaces, but cell spreading is higher on AM+FS surfaces compared with their AM counterparts. In the longer term (days 7 and 14), fibronectin and collagen synthesis increase on AM+FS surfaces as opposed to AM alone. Alkaline phosphatase activity, osteocalcin production, and mineralization, markers of osteogenic differentiation, are significantly lower on raw AM surfaces, whereas on the AM+FS specimens they display a level equivalent to that on the polished surface. Overall, these results indicate that using an FS laser beam during the fabrication of AM parts optimizes surface morphology to favor osteoblastic differentiation. This new hybrid machine could make it possible to produce AM implants with functional surfaces directly at the end of AM, thereby limiting their post-treatments.

Bioinspired surface modification of orthopedic implants for bone tissue engineering

Biomedical implants have been widely used in various orthopedic treatments, including total hip arthroplasty, joint arthrodesis, fracture fixation, non-union, dental repair, etc. The modern research and development of orthopedic implants have gradually shifted from traditional mechanical support to a bioactive graft in order to endow them with better osteoinduction and osteoconduction. Inspired by structural and mechanical properties of natural bone, this review provides a panorama of current biological surface modifications for facilitating the interaction between medical implants and bone tissue and gives a future outlook for fabricating the next-generation multifunctional and smart implants by systematically biomimicking the physiological processes involved in formation and functioning of bones.

A review of nanostructured surfaces and materials for dental implants: surface coating, patterning and functionalization for improved performance

The emerging field of nanostructured implants has enormous scope in the areas of medical science and dental implants. Surface nanofeatures provide significant potential solutions to medical problems by the introduction of better biomaterials, improved implant design, and surface engineering techniques such as coating, patterning, functionalization and molecular grafting at the nanoscale. This review is of an interdisciplinary nature, addressing the history and development of dental implants and the emerging area of nanotechnology in dental implants. After a brief introduction to nanotechnology in dental implants and the main classes of dental implants, an overview of different types of nanomaterials (i.e. metals, metal oxides, ceramics, polymers and hydrides) used in dental implant together with their unique properties, the influence of elemental compositions, and surface morphologies and possible applications are presented from a chemical point of view. In the core of this review, the dental implant materials, physical and chemical fabrication techniques and the role of nanotechnology in achieving ideal dental implants have been discussed. Finally, the critical parameters in dental implant design and available data on the current dental implant surfaces that use nanotopography in clinical dentistry have been discussed.

Inhibition of osteogenesis surrounding the titanium implant by CGRP deficiency

Previous studies have suggested one of the neurotransmitters, calcitonin gene-related peptide (CGRP), modulates local regulation of bone metabolism; however, the regulating signaling pathway is still being explored. The objective of this study was to determine whether CGRP deficiency affects the osteogenesis surrounding titanium implants in vivo. Titanium screws were implanted in 72 adult rats, which were divided into three groups randomly: Sham, inferior alveolar neurectomy (IAN), and IAN+CGRP. Saline solution containing CGRP (concentration: 100 nmol/L) was injected into the area surrounding the implants in the IAN+CGRP group every day post operation. According to histological observations and Micro-CT, osteogenesis surrounding the implant was suppressed in the IAN group compared to that in the Sham and IAN+CGRP groups; the highest degree of osteogenesis was observed in the Sham group. This effect was also proved via the gene expressions of osteocalcin and runt-related transcription factor 2 surrounding the implant by real-time (RT) PCR analysis. In addition, through immunofluorescence staining and RT-PCR analysis, levels of CGRP and β-catenin were also reduced in the IAN group, while the highest expression was observed in the Sham group (p < 0.05). Our results collectively suggest that the titanium implant bone model established by IAN exhibited CGRP deficiency and reduced osteogenesis surrounding the implant. Additionally, the expression analyses suggest that the canonical Wnt signaling pathway could be involved in this process of bone metabolism in vivo.

Tantalum-coated pedicle screws enhance implant integration

Because titanium alloy (Ti) has the natural advantage of a low elastic modulus, it has become the most commonly used material for the manufacturing of pedicle screws. However, its poor shear strength and osteogenic ability are undesirable properties. The superior osteoinductivity demonstrated by tantalum (Ta) in oral and maxillofacial surgery and joint surgery leads us to assume that the tantalum-coated pedicle screws may have better osteogenic properties and bone anchoring strength. To verify this hypothesis, MC3T3-E1 cells and human mesenchymal stem cells (hBMSCs) were seeded on the surface of Ta and Ti disks to compare the effects of two different metals on cell adhesion, proliferation, and differentiation. At the same time, we observed the inhibitory effect of Ta on osteoclasts. As an in vivo study, conventional Ti pedicle screws and Ta-coated screws were implanted in bilateral pedicles of Bama pigs. The results showed that compared to titanium, tantalum promoted greater cell adhesion and proliferation and improved the level of hBMSC mineralization, and Ta-coated screws exerted an inhibitory effect on osteoclasts. More importantly, we found that the effect of tantalum on osteogenic differentiation was mediated through the Wnt/β-catenin and TGF-β/smad signaling pathways. Ta-coated screws significantly promoted trabecular bone growth compared with Ti as evidenced by micro-CT, histology and biomechanical examination. Our study clearly indicated that tantalum was a superior promoter of osteogenesis and proved that tantalum coating is an effective improvement for titanium alloy implants.

Peptide-functionalized poly[oligo(ethylene glycol) methacrylate] brushes on dopamine-coated stainless steel for controlled cell adhesion

The modification of the surface of surgical implants with cell adhesion ligands has emerged as a promising approach to improve biomaterial-host interactions. However, these approaches are limited by the non-specific adsorption of biomolecules and uncontrolled presentation of desired bioactive ligands on implant surfaces. This leads to sub-optimal integration with host tissue and delayed healing. Here we present a strategy to grow non-fouling polymer brushes of oligo(ethylene glycol) methacrylate by atom transfer radical polymerization from dopamine-functionalized clinical grade 316 stainless steel. These brushes prevent non-specific adsorption of proteins and attachment of cells. Subsequently, the brushes can be modified with covalently tethered adhesive peptides that provide controlled cell adhesion. This approach may therefore have broad application to promote bone growth and improvements in osseointegration.

STATEMENT OF SIGNIFICANCE

Stainless steel (SS) implants are widely used clinically for orthopaedic, spinal, dental and cardiovascular applications. However, non-specific adsorption of biomolecules onto implant surfaces results in sub-optimal integration with host tissue. To allow controlled cell-SS interactions, we have developed a strategy to grow non-fouling polymer brushes that prevent protein adsorption and cell adhesion and can be subsequently functionalized with adhesive peptides to direct cell adhesion and signaling. This approach has broad application to improve osseointegration onto stainless steel implants in bone repair.

Biomaterial strategies for engineering implants for enhanced osseointegration and bone repair

Bone tissue has a remarkable ability to regenerate and heal itself. However, large bone defects and complex fractures still present a significant challenge to the medical community. Current treatments center on metal implants for structural and mechanical support and auto- or allo-grafts to substitute long bone defects. Metal implants are associated with several complications such as implant loosening and infections. Bone grafts suffer from donor site morbidity, reduced bioactivity, and risk of pathogen transmission. Surgical implants can be modified to provide vital biological cues, growth factors and cells in order to improve osseointegration and repair of bone defects. Here we review strategies and technologies to engineer metal surfaces to promote osseointegration with the host tissue. We also discuss strategies for modifying implants for cell adhesion and bone growth via integrin signaling and growth factor and cytokine delivery for bone defect repair.

Simple coating with fibronectin fragment enhances stainless steel screw osseointegration in healthy and osteoporotic rats

Metal implants are widely used to provide structural support and stability in current surgical treatments for bone fractures, spinal fusions, and joint arthroplasties as well as craniofacial and dental applications. Early implant-bone mechanical fixation is an important requirement for the successful performance of such implants. However, adequate osseointegration has been difficult to achieve especially in challenging disease states like osteoporosis due to reduced bone mass and strength. Here, we present a simple coating strategy based on passive adsorption of FN7-10, a recombinant fragment of human fibronectin encompassing the major cell adhesive, integrin-binding site, onto 316-grade stainless steel (SS). FN7-10 coating on SS surfaces promoted α5β1 integrin-dependent adhesion and osteogenic differentiation of human mesenchymal stem cells. FN7-10-coated SS screws increased bone-implant mechanical fixation compared to uncoated screws by 30% and 45% at 1 and 3 months, respectively, in healthy rats. Importantly, FN7-10 coating significantly enhanced bone-screw fixation by 57% and 32% at 1 and 3 months, respectively, and bone-implant ingrowth by 30% at 3 months compared to uncoated screws in osteoporotic rats. These coatings are easy to apply intra-operatively, even to implants with complex geometries and structures, facilitating the potential for rapid translation to clinical settings.

Protein-mediated hydroxyapatite composite layer formation on nanotubular titania

Realising controllable interactions at the bio-nanomaterial interfaces are vital in developing next-generation engineered implant materials. Titanium-based implants are key materials in biomedical engineering due to excellent bulk mechanical properties and biocompatibilities. Advanced bio-interfaces resolving nanostructured modulated surfaces that allow manipulation with the biological molecules is one of the keys to enhance favourable interactions with the surrounding biological species. Here, we developed a protein-mediated hydroxyapatite composite layer on nanotubular titania surface. Green fluorescence protein, engineered to contain hydroxyapatite binding peptides (GFPuv-HABP), was co-deposited with the hydroxyapatite precursors onto the titania nanotubes that are formed by anodisation. Ordered titanium dioxide nanotubular surfaces were coated with hydroxyapatite at physiological pH and temperature using simulated body fluid and pulsed electrochemical cathodisation. The hydroxyapatite deposit interdigitated into the nanotubes, producing a metal oxide-mineral composite. The engineered GFPuv-HABP protein was then self-assembled on the hydroxyapatite, forming a bio-modulated interface. Additionally, the engineered proteins were co-deposited with the precursor ions of hydroxyapatite mineral on the nanotubular titania plate. Bio-mediated assembly resulted in formation of a hybrid composite as an integrated interface on the nanotubular surface. Biomolecular assisted fabrication of hybrid composite interface on metal oxide substrate offers wide range of opportunities to design novel interfaces.

MULTIFUNCTIONAL TITANIUM: SURFACE MODIFICATION PROCESS AND BIOLOGICAL RESPONSE

A proper stimulation of the cell activity is the last request to the new biomaterials, intended for bone substitution and osseointegration. In this regard, the scientific literature suggests that the surface modification on a nanoscale is a major source of innovation. The nano features and multiscale topographies can stimulate cell differentiation and activity. Moreover, the presence of specific biological molecules grafted onto the biosurfaces can properly stimulate cells to tissue regeneration. The final aim is to promote a fast and physiological bone healing, at the implant site. In order to be suitable for implantation, the modified surfaces must sustain the implantation and working load/friction without damages. Two different innovative surface modifications of the Ti6Al4V alloy were tested in this research. The first one is an inorganic modification and it is aimed at inducing in vivo apatite precipitation (inorganic bioactivity) and cell interaction through nano features. The modified surface shows a complex topography (micro and nanoroughness), a modified surface chemistry (high density of hydroxyls groups), high wettability and protein absorption. Moreover, an additional biological modification by grafting of alkaline phosphatase (ALP) was tested. The modified surfaces were compared with the traditional polished and blasted ones, in terms of osteoblast adhesion, proliferation and morphology. A significant increase in the cell proliferation rate was observed on the modified materials. Moreover, the osteoblasts showed a more differentiated aspect and filopodia exploring the nanotextures on both the treated materials.

Cellular responses evoked by different surface characteristics of intraosseous titanium implants

The properties of biomaterials, including their surface microstructural topography and their surface chemistry or surface energy/wettability, affect cellular responses such as cell adhesion, proliferation, and migration. The nanotopography of moderately rough implant surfaces enhances the production of biological mediators in the peri-implant microenvironment with consequent recruitment of differentiating osteogenic cells to the implant surface and stimulates osteogenic maturation. Implant surfaces with moderately rough topography and with high surface energy promote osteogenesis, increase the ratio of bone-to-implant contact, and increase the bonding strength of the bone to the implant at the interface. Certain features of implant surface chemistry are also important in enhancing peri-implant bone wound healing. It is the purpose of this paper to review some of the more important features of titanium implant surfaces which have an impact on osseointegration.

Role of α2β1 integrins in mediating cell shape on microtextured titanium surfaces

Surface microroughness plays an important role in determining osteoblast behavior on titanium. Previous studies have shown that osteoblast differentiation on microtextured titanium substrates is dependent on alpha-2 beta-1 (α2β1) integrin signaling. This study used focused ion beam milling and scanning electron microscopy, combined with three-dimensional image reconstruction, to investigate early interactions of individual cells with their substrate and the role of integrin α2β1 in determining cell shape. MG63 osteoblast-like cells on sand blasted/acid etched (SLA) Ti surfaces after 3 days of culturing indicated decreased cell number, increased cell differentiation, and increased expression of mRNA levels for α1, α2, αV, and β1 integrin subunits compared to cells on smooth Ti (PT) surfaces. α2 or β1 silenced cells exhibited increased cell number and decreased differentiation on SLA compared to wild-type cells. Wild-type cells on SLA possessed an elongated morphology with reduced cell area, increased cell thickness, and more apparent contact points. Cells on PT exhibited greater spreading and were relatively flat. Silenced cells possessed a morphology and phenotype similar to wild-type cells grown on PT. These observations indicate that surface microroughness affects cell response via α2β1 integrin signaling, resulting in a cell shape that promotes osteoblastic differentiation.

Effect of cold working on biocompatibility of Ni-free high nitrogen austenitic stainless steels using Dalton's Lymphoma cell line

The aims of the present work are to explore the effect of cold working on in-vitro biocompatibility of indigenized low cost Ni-free nitrogen containing austenitic stainless steels (HNSs) and to compare it with conventionally used biomedical grade, i.e. AISI 316L and 316LVM, using Dalton's Lymphoma (DL) cell line. The MTT assay [3-(4,5-dimethythiazol 2-yl)-2,5-diphenyltetrazolium bromide] was performed on DL cell line for cytotoxicity evaluation and cell adhesion test. As a result, it was observed that the HNS had higher cell proliferation and cell growth and it increases by increasing nitrogen content and degree of cold working. The surface wettability of the alloys was also investigated by water contact angle measurements. The value of contact angles was found to decrease with increase in nitrogen content and degree of cold working. This indicates that the hydrophilic character increases with increasing nitrogen content and degree of cold working which further attributed to enhance the surface free energy (SFE) which would be conducive to cell adhesion which in turn increases the cell proliferation.

Topographical and chemical effects of electrochemically assisted deposited hydroxyapatite coatings on osteoblast-like cells

A recently commercialised hydroxyapatite electrochemically assisted chemical deposition technique (BoneMaster) has been shown to induce increased bone apposition; whether this response is caused by the surface topography or chemistry is unknown. An in-vitro examination using human osteoblast-like cells was performed on a series of BoneMaster-coated surfaces. The chemistry was separated from the topography using a thin gold coating; Thermanox coverslips were used as a control. BoneMaster surfaces showed significantly greater alkaline phosphatase activity and osteocalcin production compared with controls; however, no difference was found between the gold-coated and uncoated BoneMaster samples, indicating topography is the main contributing factor.

Tissue growth into three-dimensional composite scaffolds with controlled micro-features and nanotopographical surfaces

Controlling topographic features at all length scales is of great importance for the interaction of cells with tissue regenerative materials. We utilized an indirect three-dimensional printing method to fabricate polymeric scaffolds with pre-defined and controlled external and internal architecture that had an interconnected structure with macro- (400-500 μm) and micro- (∼25 μm) porosity. Polycaprolactone (PCL) was used as model system to study the kinetics of tissue growth within porous scaffolds. The surface of the scaffolds was decorated with TiO2 and bioactive glass (BG) nanoparticles to the better match to nanoarchitecture of extracellular matrix (ECM). Micrometric BG particles were also used to reveal the effect of particle size on the cell behavior. Observation of tissue growth and enzyme activity on two-dimensional (2D) films and three-dimensional (3D) scaffolds showed effects of nanoparticle inclusion and of surface curvature on the cellular adhesion, proliferation, and kinetics of preosteoblastic cells (MC3T3-E1) tissue growth into the pore channels. It was found that the presence of nanoparticles in the substrate impaired cellular adhesion and proliferation in 3D structures. Evaluation of alkaline phosphate activity showed that the presence of the hard particles affects differentiation of the cells on 2D films. Notwithstanding, the effect of particles on cell differentiation was not as strong as that seen by the curvature of the substrate. We observed different effects of nanofeatures on 2D structures with those of 3D scaffolds, which influence the cell proliferation and differentiation for non-load-bearing applications in bone regenerative medicine.

Phospholipases of mineralization competent cells and matrix vesicles: roles in physiological and pathological mineralizations

The present review aims to systematically and critically analyze the current knowledge on phospholipases and their role in physiological and pathological mineralization undertaken by mineralization competent cells. Cellular lipid metabolism plays an important role in biological mineralization. The physiological mechanisms of mineralization are likely to take place in tissues other than in bones and teeth under specific pathological conditions. For instance, vascular calcification in arteries of patients with renal failure, diabetes mellitus or atherosclerosis recapitulates the mechanisms of bone formation. Osteoporosis—a bone resorbing disease—and rheumatoid arthritis originating from the inflammation in the synovium are also affected by cellular lipid metabolism. The focus is on the lipid metabolism due to the effects of dietary lipids on bone health. These and other phenomena indicate that phospholipases may participate in bone remodelling as evidenced by their expression in smooth muscle cells, in bone forming osteoblasts, chondrocytes and in bone resorbing osteoclasts. Among various enzymes involved, phospholipases A₁ or A₂, phospholipase C, phospholipase D, autotaxin and sphingomyelinase are engaged in membrane lipid remodelling during early stages of mineralization and cell maturation in mineralization-competent cells. Numerous experimental evidences suggested that phospholipases exert their action at various stages of mineralization by affecting intracellular signaling and cell differentiation. The lipid metabolites—such as arachidonic acid, lysophospholipids, and sphingosine-1-phosphate are involved in cell signaling and inflammation reactions. Phospholipases are also important members of the cellular machinery engaged in matrix vesicle (MV) biogenesis and exocytosis. They may favour mineral formation inside MVs, may catalyse MV membrane breakdown necessary for the release of mineral deposits into extracellular matrix (ECM), or participate in hydrolysis of ECM. The biological functions of phospholipases are discussed from the perspective of animal and cellular knockout models, as well as disease implications, development of potent inhibitors and therapeutic interventions.

Spatial and temporal evaluation of cell attachment to printed polycaprolactone microfibres

Surface topography plays a crucial role in influencing cellular responses and has therefore been utilized in the development of numerous implantable devices. Whilst numerous studies have either investigated cell attachment or migration post-attachment, few have looked at the early-stages of this process temporally. The aim of this study was to evaluate the use of time-lapse microscopy to study the behaviour of fibroblasts cultured with polycaprolactone microfibres and to assess spatially and temporally the cell-structure interaction over a 24h period. Ordered polymeric structures were printed (predetermined) onto glass substrates using an electrohydrodynamic direct write process to produce fine (3-5 μm wide) structures. Fibroblast attachment and migration were characterized as a function of distance perpendicular from structures (∼17.3, 34.6 and 51.9 μm). The use of time-lapse microscopy revealed a gradual decrease in cell attachment as the distance from the microfibres was increased. The technique also revealed that some cells were attaching and detaching from the microfibre multiple times. Our findings demonstrate that time-lapse microscopy is a useful technique for evaluating early-stage cell-biomaterial interaction that is capable of recording important events that might otherwise be overlooked.

Nanosurface design of dental implants for improved cell growth and function

A strategy was proposed for the topological design of dental implants based on an in vitro survey of optimized nanodot structures. An in vitro survey was performed using nanodot arrays with dot diameters ranging from 10 to 200 nm. MG63 osteoblasts were seeded on nanodot arrays and cultured for 3 days. Cell number, percentage undergoing apoptotic-like cell death, cell adhesion and cytoskeletal organization were evaluated. Nanodots with a diameter of approximately 50 nm enhanced cell number by 44%, minimized apoptotic-like cell death to 2.7%, promoted a 30% increase in microfilament bundles and maximized cell adhesion with a 73% increase in focal adhesions. An enhancement of about 50% in mineralization was observed, determined by von Kossa staining and by Alizarin Red S staining. Therefore, we provide a complete range of nanosurfaces for growing osteoblasts to discriminate their nanoscale environment. Nanodot arrays present an opportunity to positively and negatively modulate cell behavior and maturation. Our results suggest a topological approach which is beneficial for the design of dental implants.

The Otto Aufranc Award: Demineralized bone matrix around porous implants promotes rapid gap healing and bone ingrowth

BACKGROUND

Noncemented revision arthroplasty is often complicated by the presence of bone implant gaps that reduce initial stability and biologic fixation. Demineralized bone matrix has osteoinductive properties and therefore the potential to enhance gap healing and porous implant fixation.

QUESTIONS/PURPOSES

We determined at what times and to what extent demineralized bone matrix promotes gap healing and bone ingrowth around a porous implant.

METHODS

We inserted porous titanium implants into the proximal metaphyses of canine femora and humeri, with an initial 3-mm gap between host cancellous bone and implants. We left the gaps empty (control; n = 12) or filled them with either demineralized bone matrix (n = 6) or devitalized demineralized bone matrix (negative control; n = 6) and left them in situ for 4 or 12 weeks. We quantified volume healing of the gap with new bone using three-dimensional micro-CT scanning and quantified apposition and ingrowth using backscattered scanning electron microscopy.

RESULTS

The density of bone inside gaps filled with demineralized bone matrix reached 64% and 93% of surrounding bone density by 4 and 12 weeks, respectively. Compared with empty controls and negative controls at 4 and 12 weeks, gap healing using demineralized bone matrix was two to three times greater and bone ingrowth and apposition were up to 15 times greater.

CONCLUSIONS

Demineralized bone matrix promotes rapid bone ingrowth and gap healing around porous implants.

CLINICAL RELEVANCE

Demineralized bone matrix has potential for enhancing implant fixation in revision arthroplasty.

Silorane resin supports proliferation, differentiation, and mineralization of MLO-A5 bone cells in vitro and bone formation in vivo

Methyl methacrylate used in bone cements has drawbacks of toxicity, high exotherm, and considerable shrinkage. A new resin, based on silorane/oxirane chemistry, has been shown to have little toxicity, low exotherm, and low shrinkage. We hypothesized that silorane-based resins may also be useful as components of bone cements as well as other bone applications and began testing on bone cell function in vitro and in vivo. MLO-A5, late osteoblast cells, were exposed to polymerized silorane (SilMix) resin (and a standard polymerized bisGMA/TEGDMA methacrylate (BT) resin and compared to culture wells without resins as control. A significant cytotoxic effect was observed with the BT resin resulting in no cell growth, whereas in contrast, SilMix resin had no toxic effects on MLO-A5 cell proliferation, differentiation, nor mineralization. The cells cultured with SilMix produced increasing amounts of alkaline phosphatase (1.8-fold) compared to control cultures. Compared to control cultures, an actual enhancement of mineralization was observed in the silorane resin-containing cultures at days 10 and 11 as determined by von Kossa (1.8-2.0 fold increase) and Alizarin red staining (1.8-fold increase). A normal bone calcium/phosphate atomic ratio was observed by elemental analysis along with normal collagen formation. When used in vivo to stabilize osteotomies, no inflammatory response was observed, and the bone continued to heal. In conclusion, the silorane resin, SilMix, was shown to not only be non cytototoxic, but actually supported bone cell function. Therefore, this resin has significant potential for the development of a nontoxic bone cement or bone stabilizer.

Improvement of Bone Ingrowth on PEEK Surface Implant

It was demonstrated that microstructured surfaces improve cell spreading and bone ingrowth. Particularly, the surface roughness modulates the osseointegration of orthopaedic and dental implants. We have developed an innovative grit blasting process using Biphasic Calcium Phosphate, a Resorbable Biocompatible Blast Media (RBBM). PEEK is biocompatible but an inert material, involving no direct bone bonding. Implants coming from a rabbit experimental study, were processed for X-rays Micro tomography. Light microscopy and SEM were performed.It was demonstrated in this study that the surface treatment on PEEK improve the quality of bone architecture in direct contact with the sample surface, compared to the classical surface of PEEK. These data demonstrate that PEEK rough surface obtained by RBBM blasting maintain high biocompatibility and bone osteoconduction, and promote higher stability of the implant.

Computational modelling of biomaterial surface interactions with blood platelets and osteoblastic cells for the prediction of contact osteogenesis

Surface microroughness can induce contact osteogenesis (bone formation initiated at the implant surface) around oral implants, which may result from different mechanisms, such as blood platelet-biomaterial interactions and/or interaction with (pre-)osteoblast cells. We have developed a computational model of implant endosseous healing that takes into account these interactions. We hypothesized that the initial attachment and growth factor release from activated platelets is crucial in achieving contact osteogenesis. In order to investigate this, a computational model was applied to an animal experiment [7] that looked at the effect of surface microroughness on endosseous healing. Surface-specific model parameters were implemented based on in vitro data (Lincks et al. Biomaterials 1998;19:2219-32). The predicted spatio-temporal patterns of bone formation correlated with the histological data. It was found that contact osteogenesis could not be predicted if only the osteogenic response of cells was up-regulated by surface microroughness. This could only be achieved if platelet-biomaterial interactions were sufficiently up-regulated as well. These results confirmed our hypothesis and demonstrate the added value of the computational model to study the importance of surface-mediated events for peri-implant endosseous healing.

Relative influence of surface topography and surface chemistry on cell response to bone implant materials. Part 2: Biological aspects

A current medical challenge is the replacement of tissue which can be thought of in terms of bone tissue engineering approaches. The key problem in bone tissue engineering lies in associating bone stem cells with material supports or scaffolds that can be implanted in a patient. Beside bone tissue engineering approaches, these types of materials are used daily in orthopaedics and dental practice as permanent or transitory implants such as ceramic bone filling materials or metallic prostheses. Consequently, it is essential to better understand how bone cells interact with materials. For several years, the current authors and others have developed in vitro studies in order to elucidate the mechanisms underlying the response of human bone cells to implant surfaces. This paper reviews the current state of knowledge and proposes future directions for research in this domain.

Surface modification of biomedical and dental implants and the processes of inflammation, wound healing and bone formation

Bone adaptation or integration of an implant is characterized by a series of biological reactions that start with bone turnover at the interface (a process of localized necrosis), followed by rapid repair. The wound healing response is guided by a complex activation of macrophages leading to tissue turnover and new osteoblast differentiation on the implant surface. The complex role of implant surface topography and impact on healing response plays a role in biological criteria that can guide the design and development of future tissue-implant surface interfaces.

TiO2 nanotubes on Ti: Influence of nanoscale morphology on bone cell-materials interaction

Ti being bioinert shows poor bone cell adhesion with an intervening fibrous capsule. Ti could be made bioactive by several methods including growing in situ TiO2 layer on Ti-surface. TiO2 nanotubes were grown on Ti surface via anodization process and the bone cell-material interactions were evaluated. Human osteoblast cell attachment and growth behavior were studied using an osteoprecursor cell line for 3, 7, and 11 days. An abundant amount of extracellular matrix (ECM) between the neighboring cells was noticed on anodized nanotube surface with filopodia extensions coming out from cells to grasp the nanoporous surface of the nanotube for anchorage. To better understand and compare cell-materials interactions, anodized nanoporous sample surfaces were etched with different patterns. Preferential cell attachment was noticed on nanotube surface compare to almost no cells in etched Ti surface. Cell adhesion with vinculin adhesive protein showed higher intensity, positive contacts on nanoporous surface and thin focal contacts on the Ti-control. Immunochemistry study with alkaline phosphatase showed enhanced osteoblastic phenotype expressions in nanoporous surface. Osteoblast proliferation was significantly higher on anodized nanotube surface. Surface properties changed with the emergence of nanoscale morphology. Higher nanometer scale roughness, low contact angle and high surface energy in nanoporous surface enhanced the osteoblast-material interactions. Mineralization study was done under simulated body fluid (SBF) with ion concentration nearly equal to human blood plasma to understand biomimetic apatite deposition behavior. Although apatite layer formation was noticed on nanotube surface, but it was nonuniform even after 21 days in SBF.

Biodegradable Polymers in Bone Tissue Engineering

The use of degradable polymers in medicine largely started around the mid 20^th century with their initial use as in vivo resorbing sutures. Thorough knowledge on this topic as been gained since then and the potential applications for these polymers were, and still are, rapidly expanding. After improving the properties of lactic acid-based polymers, these were no longer studied only from a scientific point of view, but also for their use in bone surgery in the 1990s. Unfortunately, after implanting these polymers, different foreign body reactions ranging from the presence of white blood cells to sterile sinuses with resorption of the original tissue were observed. This led to the misconception that degradable polymers would, in all cases, lead to inflammation and/or osteolysis at the implantation site. Nowadays, we have accumulated substantial knowledge on the issue of biocompatibility of biodegradable polymers and are able to tailor these polymers for specific applications and thereby strongly reduce the occurrence of adverse tissue reactions. However, the major issue of biofunctionality, when mechanical adaptation is taken into account, has hitherto been largely unrecognized. A thorough understanding of how to improve the biofunctionality, comprising biomechanical stability, but also visualization and sterilization of the material, together with the avoidance of fibrotic tissue formation and foreign body reactions, may greatly enhance the applicability and safety of degradable polymers in a wide area of tissue engineering applications. This review will address our current understanding of these biofunctionality factors, and will subsequently discuss the pitfalls remaining and potential solutions to solve these problems.

Mechanisms regulating increased production of osteoprotegerin by osteoblasts cultured on microstructured titanium surfaces

Osteoblasts grown on microstructured Ti surfaces enhance osteointegration by producing local factors that regulate bone formation as well as bone remodeling, including the RANK ligand decoy receptor osteoprotegerin (OPG). The objective of this study was to explore the mechanism by which surface microstructure and surface energy mediate their stimulatory effects on OPG expression. Titanium disks were manufactured to present different surface morphologies: a smooth pretreatment surface (PT, Ra<0.2microm), microstructured sandblasted/acid etched surface (SLA, Ra=3-4microm), and a microstructured Ti plasma-sprayed surface (TPS, Ra=4microm). Human osteoblast-like MG63 cells were cultured on these substrates and the regulation of OPG production by TGF-beta1, PKC, and alpha2beta1 integrin signaling determined. Osteoblasts produced increased amounts of OPG as well as active and latent TGF-beta1 and had increased PKC activity when grown on SLA and TPS. Exogenous TGF-beta1 increased OPG production in a dose-dependent manner on all surfaces, and this was prevented by adding blocking antibody to the TGF-beta type II receptor or by reducing TGF-beta1 binding to the receptor by adding exogenous soluble type II receptor. The PKC inhibitor chelerythrine inhibited the production of OPG in a dose-dependent manner, but only in cultures on SLA and TPS. shRNA knockdown of alpha2 or a double knockdown of alpha2beta1 also reduced OPG, as well as production of TGF-beta1. These results indicate that substrate-dependent OPG production is regulated by TGF-beta1, PKC, and alpha2beta1 and suggest a mechanism by which alpha2beta1 signaling increases PKC, resulting in TGF-beta1 production and TGF-beta1 then acts on its receptor to increase transcription of OPG.

Bone growth enhancement in vivo on press-fit titanium alloy implants with acid etched microtexture

Early bone ongrowth secures long-term fixation of primary implants inserted without cement. Implant surfaces roughened with a texture on the micrometer scale are known to be osseoconductive. The aim of this study was to evaluate the bone formation at the surface of acid etched implants modified on the micro-scale. We compared implants with a nonparticulate texture made by chemical milling (hydrofluoric acid, nitric acid) (control) with implants that had a dual acid etched (hydrofluoric acid, hydrochloric acid) microtexture surface superimposed on the primary chemically milled texture. We used an experimental joint replacement model with cylindrical titanium implants (Ti-6Al-4V) inserted paired and press-fit in cancellous tibia metaphyseal bone of eight canines for 4 weeks and evaluated by histomorphometric quantification. A significant twofold median increase was seen for bone ongrowth on the acid etched surface [median, 36.1% (interquartile range, 24.3-44.6%)] compared to the control [18.4% (15.6-20.4%)]. The percentage of fibrous tissue at the implant surface and adjacent bone was significantly less for dual acid textured implants compared with control implants. These results show that secondary roughening of titanium alloy implant surface by dual acid etching increases bone formation at the implant bone interface.