Histomorphometric and histologic evaluation of titanium–zirconium (<Emphasis Type="Italic">a</Emphasis>TiZr) implants with anodized surfaces

The choice of implant surface has a significant influence on osseointegration. Modification of TiZr surface by anodization is reported to have the potential to modulate the osteoblast cell behaviour favouring more rapid bone formation. The aim of this study is to investigate the effect of anodizing the surface of TiZr discs with respect to osseointegration after four weeks implantation in sheep femurs. Titanium (Ti) and TiZr discs were anodized in an electrolyte containing dl-α-glycerophosphate and calcium acetate at 300 V. The surface characteristics were analyzed by scanning electron microscopy, electron dispersive spectroscopy, atomic force microscopy and goniometry. Forty implant discs with thickness of 1.5 and 10 mm diameter (10 of each-titanium, titanium–zirconium, anodized titanium and anodized titanium–zirconium) were placed in the femoral condyles of 10 sheep. Histomorphometric and histologic analysis were performed 4 weeks after implantation. The anodized implants displayed hydrophilic, porous, nano-to-micrometer scale roughened surfaces. Energy dispersive spectroscopy analysis revealed calcium and phosphorous incorporation into the surface of both titanium and titanium–zirconium after anodization. Histologically there was new bone apposition on all implanted discs, slightly more pronounced on anodised discs. The percentage bone-to-implant contact measurements of anodized implants were higher than machined/unmodified implants but there was no significant difference between the two groups with anodized surfaces (P > 0.05, n = 10). The present histomorphometric and histological findings confirm that surface modification of titanium–zirconium by anodization is similar to anodised titanium enhances early osseointegration compared to machined implant surfaces.     

Osseointegration of Titanium Implants by Addition of Recombinant Bone Morphogenetic Protein 2 (rhBMP‐2)

The osseointegration of long‐term implants is often incomplete such that gaps remain between the implant surface and the surrounding hard tissue. This study examines the effect of soluble recombinant human bone morphogenic protein 2 (rhBMP‐2) on gap healing and osseous integration. The effect of a single, intraoperative application of soluble rhBMP‐2 on the formation of new bone around titanium implants was studied. A total of 8 titanium‐alloy cylinders (Ti‐6Al‐4V) with a plasma spray coating (TPS; 400 μm thickness) were implanted into femoral condyles of mature sheep: rhBMP‐2 solution (1 μg) was pipetted into the 1 mm wide cleft around 4 implants; 4 further implants served as rhBMP‐2‐free controls. Two of these controls exhibited an additional calciumphosphate‐coating. The cleft around the implants served as testing zone to study the formation of new bone by microradiographical and histological analyses. The follow‐up periods were 4 and 9 weeks, respectively. A significant amount of new bone contacting the implants' surface was detected where rhBMP‐2‐solution had been used: In 50% a circumferential osseoinduction occurred within 4 weeks and a nearly complete osseointegration was observed after 9 weeks. In all cases bone formation was exaggerated and filled the spongiosa with compact bone. Time matched TPS‐controls and controls with calciumphosphate coating showed no notable formation of new bone. The results suggest that a single administration of soluble rhBMP‐2 into a bone cavity can augment bone formation and also osseointegration of titanium implants. Further investigations based on these findings are necessary to develop long‐term implants (e. g. joint replacements) with rhBMP‐2‐biocoating for humans.     

Correlation between primary stability and bone healing of surface treated titanium implants in the femoral epiphyses of rabbits

The aim of this study was to analyse the stability and osseointegration of surface treated titanium implants in rabbit femurs. The implants were either grit-blasted and acid-etched (BE Group), calcium phosphate (CaP) coated by using the electrodeposition technique, or had bioactive molecules incorporated into the CaP coatings: either cyclic adenosine monophosphate (cAMP) or dexamethasone (Dex). Twenty four cylindrical titanium implants (n = 6/group) were inserted bilaterally into the femoral epiphyses of New Zealand White, female, adult rabbits for 4 weeks. Implant stability was measured by resonance frequency analysis (RFA) the day of implantation and 4 weeks later, and correlated to histomorphometric parameters, bone implant contact (BIC) and bone growth around the implants (BS/TS 0.5 mm). The BIC values for the four groups were not significantly different. That said, histology indicated that the CaP coatings improved bone growth around the implants. The incorporation of bioactive molecules (cAMP and Dex) into the CaP coatings did not improve bone growth compared to the BE group. Implant stability quotients (ISQ) increased in each group after 4 weeks of healing but were not significantly different between the groups. A good correlation was observed between ISQ and BS/TS 0.5 mm indicating that RFA is a non-invasive method that can be used to assess the osseointegration of implants. In conclusion, the CaP coating enhanced bone formation around the implants, which was correlated to stability measured by resonance frequency analysis. Furthers studies need to be conducted in order to explore the benefits of incorporating bioactive molecules into the coatings for peri-implant bone healing.     

Modell zur Analyse des knöchernen Anwachsverhaltens auf bioaktiv beschichteten Implantatoberflächen

Model to analyse the bone on‐growth on bioactive coated implant surfaces Especially on the field of bone regeneration, transient and permanent implants are an important method of therapy in the Orthopaedic Surgery. In this context, bioactive surfaces on metallic implants provide an improved contact to the surrounding bone. The goal of our study was to establish an in‐vitro test system to evaluate the on‐growth of bone‐derived cells on different surface coatings. Therefore, we invented a special kind of clamps made of commercially‐pure (c‐p) titanium and blasted with hydroxyapatite particles followed by electrochemically coating with calcium phosphate (BONIT®‐HA, BONIT®). Definite pieces of human cancellous bone were attached to these clamps, inserted onto tissue culture plates and cultivated in DMEM for ten days. Finally, the contact area between human cancellous bone and the implant surface was analyzed and the spreading of osteoblast‐like cells evaluated by scanning electron microscopy (SEM). A well‐spread morphology of bone cells was observed on the implant surfaces coated with calcium phosphate (CaP). In comparison the clamps without CaP coatings showed only a marginal growth of bone cells on the clamp surface. The presented newly in‐vitro test setup using titanium clamps coated with bioactive layers attached to human cancellous bone represents a well‐functioning model for qualitative evaluation of bone on‐growth.     

Comparison of early osseointegration between laser-treated/acid-etched and sandblasted/acid-etched titanium implant surfaces

This study was designed to compare the early osseointegration of titanium surfaces prepared via laser-treated/acid-etched (LA) and sandblasted/acid-etched (SLA) in dogs. Titanium implants were divided into two groups: Surfaces of the experimental group were treated via LA, while in the control group, surfaces were treated via SLA. The physical and chemical properties of LA and SLA surfaces were tested and compared. Sixteen implants with LA or SLA surfaces were placed into the tibias of four beagle dogs, each treatment group received two implants per single tibia. The dogs were sacrificed two and four weeks after implant placement. Scanning electron microscopy showed that both the LA and SLAs surface exhibited rough structures with micro pores sized 1–3?μm. In the LA surface, regular melting points were observed. However, in the SLA surface, the structure was irregular and few oxide aluminum particles still remained. Only titanium and a small amount of titanium compounds were detected on LA surfaces, while Al was found of SLA surfaces. The LA surface roughness was above that of SLA surfaces (LA: Ra: 2.1?μm; SLA: Ra :1.53?μm; P?<?0.01). Both groups exhibited good osseointegration and no significant differences were found in the BIC% at two or four weeks between both groups (P?>?0.05). Both groups exhibited good osseointegration; however, the LA surface was cleaner and more uniform than the SLA surface, and no significant differences were found between both groups.     

Beschichtung von Implantaten mit Hydroxylapatit: Die Option auf eine stoffschlüssige Verbindung zwischen Knochen und Metall

Implants Coated with Hydroxyaptit: The Option for Joining Metal to Hard Tissue Load bearing components for artificial joints are made of bioinert alloys. These implants can only be joint to bone by form closure or frictional connection. Coating bioinert implants with bioactive hydroxyaptite ceramics (HA) offers the option to have a biological interaction between the bone and the coated implant. This way tensile forces can be transfered to the implant. This papers reviews material properties and recommendations how to design plasma sprayed HA-coatings for total hip replacement. There is clinical proof that due to the enhanced interaction between the HA-coating and the implants an excellent bonding can be achieved, i. e. long-term osseointegration or biological/chemical interaction between inert anorganic materials and vital tissue. There are no technical problems coating implants with HA. Clinical results based on more than 10 years are available.     

Human-osteoblast proliferation and differentiation on grit-blasted and bioactive titanium for dental applications

Physico-chemical and topographical surface quality of commercially pure titanium (c.p. Ti) dental implants is one of the most influencing factors in the improvement of their osseointegration. In this sense, previously, a two-step method (2S) for obtaining bioactive blasted-rough titanium surfaces was developed for improving short-term (due to its bioactivity) and long-term (due to its roughness) osseointegration. This 2S-method consists of: (1) Grit blasting on titanium surface in order to roughen it, and (2) thermo-chemical (TCh) treatment in order to obtain a bioactive surface with bone-bonding ability. The aim of the present work is to evaluate the in vitro human-osteoblast response (proliferation, differentiation – ALP activity- and cell morphology-studied by environmental scanning electron microscopy) of rough c.p. Ti (grit blasted), bioactive c.p. Ti (thermo-chemically treated) and rough-bioactive c.p. Ti (2S-treated). Different grit materials (Al₂O₃ and SiC) have been used in order to investigate their influence. The results showed that cell adhesion was statistically higher for the rough and bioactive surfaces, whatever the grit used. Cells proliferated very well on all the c.p. Ti surfaces. If comparing groups with and without TCh (all other treatments being equal) the ALP was always higher in the groups with TCh, indicating stimulation of osteoblast differentiation because of TCh, more significantlly in the groups that were first blasted. Those ALP results were accompanied by a decrease in the value of proliferation, which shows the good behavior of the cells. This results suggest that a rough and bioactive-titanium surface obtained by 2S-treatment enhances adhesion and differentiation activity of human osteoblasts cells.     

Biomimetic calcium phosphate coating on Ti-7.5Mo alloy for dental application

Titanium and its alloys have been used as bone-replacement implants due to their excellent corrosion resistance and biocompatibility. However, a titanium coating is a bioinert material and cannot bond chemically to bone tissue. The objective of this work was to evaluate the influence of alkaline treatment and heat treatment on the formation of calcium phosphate layer on the surface of a Ti-7.5Mo alloy after soaking in simulated body fluid (SBF). Thirty six titanium alloy plates were assigned into two groups. For group I, samples were immersed in a 5.0-M NaOH aqueous solution at 80°C for 72 h, washed with distilled water and dried at 40°C for 24 h. For group II, after the alkaline treatment, samples were heat-treated at 600°C for 1 h in an electrical furnace in air. Then, all samples were immersed in SBF for 7 or 14 days to allow the formation of a calcium phosphate coating on the surface. The surfaces were characterized using SEM, EDS, AFM and contact angle measurements.     

Bioactive glass and glass-ceramic-coated hip endoprosthesis: experimental study in rabbit

Co–Cr–Mo endoprostheses with a dual bioactive glass (BG) coating and titanium implants coated with a bioactive glass-ceramic (BGC) were studied under lead-bearing conditions in the rabbit hip. The dual BG coating contained an inner layer of high durability and an outer bioactive layer. Each type of coating improved the stabilization of prosthesis during the experiment period of 8 weeks compared to non-coated control implants. EDXA analysis confirmed the ability of BG and BGC coatings to bond chemically to bone. The BGC coating on titanium alloy proved superior to the dual BG coating on Co–Cr–Mo prosthesis with regard to bone formation on the surface of the implant. The bioactive top layer of the dual BG coating showed resorption, especially in the areas without direct bone contact. This is explained by partial crystallization of the glass during firing. Thermal discrepancy between BGC coating and titanium core caused cracking of the coating, which remains a major obstacle to its use as a bioactive coating.     

Osteoblast proliferation on neat and apatite-like calcium phosphate-coated titanium foam scaffolds

The biocompatibility and the load-bearing ability of lightweight titanium made it possible to be used as a biomaterial, especially in hip revision and fixation surgery. It was initially shown that sand-blasted or surface-roughened titanium implants had an improved bone-bonding ability over the bioinert metallic surfaces. Plasma-spraying of a phase mixture of loosely-attached calcium phosphates on titanium implants further improved their in vivo bone-bonding ability. However, stoichiometric calcium hydroxyapatite ceramic of high crystallinity is known to have poor in vivo resorbability, and is shy of taking part in bone remodeling and of being resorbed by the osteoclasts. Supersaturated calcium phosphate (CaP) solutions, such as synthetic body fluids (SBF), on the other hand, are able to form “carbonated, hydrophilic and apatite-like” CaP nanoaggregates on titanium surfaces. A Tris-buffered SBF solution with an HCO₃⁻ concentration of 27 mM was used in this study. Neat, NaOH-etched, and SBF-coated (biomimetic coating) titanium foams were compared with in vitro cell culture experiments by using rat osteoblasts. SBF-coated foams were found to yield the highest protein concentration at the end of the in vitro culture tests. Such biomimetic coatings were easily formed on flat strips, springs, or 3D foams of titanium, without any geometric constraints. The coated titanium springs and foams were characterized by using XRD, SEM, and FTIR.     

Influence of acid-etching after grit-blasted on osseointegration of titanium dental implants: in vitro and in vivo studies

Rough implant surfaces have shown improved osseointegration rates. In a majority of dental implants, the microrough surfaces are obtained by grit blasting and/or acid-etching. The aim of this contribution was to evaluate the effects of acid-etching, after the grit-blasted treatment in titanium dental implants, on surface wettability, surface energy, osteoblast responses and its osseointegration behavior. Four surfaces were studied: as-machined, acid-etched, micro-rough by grit-blasting and the combination grit-blasted surface with acid-etched. The surfaces with increasing roughness show more osteoblastic adhered cells. This effect was most pronounced on samples blasted and blasted with acid-etching. The roughness obtained by grit-blasting is the main factor in comparison with the acid etching treatment in the biological response. These results were confirmed in vivo tests and histological analysis. The results demonstrated that the combination of the grit-blasted and acid-etched accelerated lightly bone regeneration at the different periods of implantation in comparison with the grit-blasted implants.     

Effect of microstructural evolution on wettability of laser coated calcium phosphate on titanium alloy

Surface engineering of synthetic implant materials provides an exciting opportunity to mimic natural biomaterials. Surface that are bioactive and textured at multi-scale have the potential for easier osseointegration. Ti alloy surfaces known for their biocompatibility are coated with bioactive calcium phosphate using a laser source at multiple processing speeds. The resulting surface has multi-scale morphology and multi-phase chemical nature. Faster processing speeds showed improved wettability to water along with higher degree of crystallinity in the phases present. Furthermore, decreased laser processing speeds induced formation of increased amount of glassy phases that are expected to provide increased biocompatibility. The combination of these opposing effects suggested that optimum crystallinity leading to optimum wettability can be produced at intermediate speeds for improved biocompatibility.     

3D-printed surface promoting osteogenic differentiation and angiogenetic factor expression of BMSCs on Ti6Al4V implants and early osseointegration in vivo

Three-dimensional-printed (3D-P) titanium implants display many advantages, such as design flexibility, higher efficiency, the capability to easily construct complex or customized structures, etc., and is believed to potentially replace traditional implants. However, the biological performance of the 3D-P titanium surface has not been investigated systematically. Herein, we analyzed the surface characteristics of 3D-P Ti6Al4V implants and evaluated the biological responses of bone marrow derived mesenchymal stromal cells (BMSCs) to the 3D-P surface in vitro. Moreover, after implantation into the rat femoral condyle for 3 and 6 weeks, the osseointegration performance was evaluated. The results showed the 3D-P Ti6Al4V implant presented distinct fluctuant macroscale rough surface and relatively better hydrophilicity which enhanced the adhesion, proliferation, osteogenic differentiation and angiogenetic factor expression of BMSCs. Moreover, the in vivo osseointegration performance was also better than that of the control group at the early stage. The present study suggested the 3D-P titanium alloy is a promising candidate to be used as implant material.     

New chemical treatment for bioactive titanium alloy with high corrosion resistance

It was recently claimed that titanium metal and its alloys can bond to the living bone, without being coated by apatite (VPS coatings), but by being chemically and heat-treated. The bioactivity of treated titanium is of interest because of the opportunity to obtain orthopaedic or dental implants presenting, at the same time, high toughness, strength and fatigue resistance as well as bone-bonding ability. The bioactive behaviour of the treated implants is due to the presence of a modified surface, which, during soaking in body fluid, promotes the precipitation of apatite. The apatite formed is strongly bonded to the substrate and promotes living bone bonding. In this work were characterised samples of Ti-6Al-7Nb alloy with surfaces presenting a different chemical and mechanical state. The aim of the research was twofold. The first objective was to characterise chemically and heat-treated samples with different surface topography, in order to define the best conditions for osteogenic integration. The second aim was to assess the corrosion behaviour of the bioactive implants, because they expose a microporous and quite thin modified surface layer. No-treated and passivated samples, with a surface state closed to that nowadays used on implants, were used as reference. The surface structure, morphology, electrochemical behaviour and bioactivity of the different samples were assessed by means of XRD, SEM-EDS, anodic polarizations, open circuit measurements and in-vitro tests. Results evidence that it is possible to modify the surface of the Ti-6Al-7Nb alloy in order to obtain the formation of a bioactive layer and that the substrate roughness influences the characteristics of the surface layer formed. It was also evidenced that the as treated surfaces present inadequate corrosion behaviour, so a new two-step chemical treatment has been developed in order to obtain a bioactive material with good corrosion resistance.     

Variation of roughness and adhesion strength of deposited apatite layers on titanium dental implants

It is known that surface roughness and chemical composition of the titanium surface influence the osseointegration of titanium implants. Most commercial dental implants offer a shot-blasted rough surface. It is also known that apatite layers coating the surface of titanium implants improve bone response, but the adhesion of the layer to the substrate poses some problems.In this study the roughness and adhesion strength to a titanium dental implant surface of an apatite layer deposited via wet chemistry after a thermochemical treatment were compared with those of plasma-sprayed apatite layers and machined titanium surfaces. Different surface conditions have been studied: (a) as-received machined dental implant surface; (b) grit-blasted titanium surface; (c) grit-blasted and thermochemically-treated titanium surface; (d) titanium surfaces coated with plasma-sprayed apatite. The morphology and roughness of the samples were measured and compared. The adhesion of the apatite layers to the titanium was compared by means of a scratch test.Measured roughness showed that the deposition of an apatite layer did not affect roughness but plasma-sprayed apatite produced a decrease on roughness values when compared to control samples. Both roughness and adhesion strength of the deposited apatite layer to the titanium substrate were higher than those of the plasma-sprayed apatite.     

Unravelling the effect of macro and microscopic design of dental implants on osseointegration: a randomised clinical study in minipigs

Several dental implants are commercially available and new prototype design are constantly being fabricated. Nevertheless, it is still unclear what parameters of the design affect most the osseointegration of dental implants. The purpose of this study is to assess the effects of the microscopic and macroscopic design of dental implants in the osseointegration by comparing three macroscopic designs (Straumann tissue level (STD), essential cone (ECD) and prototype design (PD)) and six surface treatments. A total of 96 implants were placed in 12 minipigs. The implant stability quotient (ISQ), was assessed at the time of implantation, as well as at 2, 4 and 8 weeks. Histomorphometric and statistical analyses were conducted at the different sacrifice times, being 2, 4 and 8 weeks, to analyse the bone to implant contact (BIC), the bone area density (BAT) and the density of bone outside the thread region (ROI). The macroscopic design results showed higher ISQ values for the ECD, whereas the histomorphometric analysis showed higher ossoeintegration values for the STD. Regarding the microscopic design, both Sandblasted plus acid etching (hydrochloric/sulphuric acid) in a nitrogen atmosphere (SLActive) and Shot-blasted or bombarded with alumina particles and posterior alkaline immersion and thermal treatment (ContacTi) showed superior results in terms of osseointegration and reduced the osseointegration times from 8 weeks to 4 weeks compared to the other analysed surfaces. In conclusion, each of the macroscopic and microscopic designs need to be taken into account when designing novel dental implants to enhance the osseointegration process.     

Bone tissue response to titanium implant surfaces modified with carboxylate and sulfonate groups

The present study assessed in vivo new bone formation around titanium alloy implants chemically grafted with macromolecules bearing ionic sulfonate and/or carboxylate groups. Unmodified and grafted Ti–6Al–4V exhibiting either 100% carboxylate, or 100% sulfonate, or both carboxylate and sulfonate groups in the percent of 50/50 and 80/20 were bilaterally implanted into rabbit femoral condyle. Neither toxicity nor inflammation were observed for all implants tested. After 4 weeks, peri-implant new bone formation varied as a function of the chemical composition of the titanium surfaces. The percent bone-implant contact (BIC) was the lowest (13.4 ± 6.3%) for the implants modified with grafted carboxylate only. The value of BIC on the implants with 20% sulfonate (24.6 ± 5.2%) was significantly (P < 0.05) lower than that observed on 100% sulfonate (38.2 ± 13.2%) surfaces. After both 4 and 12 weeks post-implantation, the BIC value for implants with more than 50% sulfonate was similar to that obtained with the unmodified Ti–6Al–4V. The grafted titanium alloy exhibiting either 100% sulfonate or carboxylate and sulfonate (50% each) groups promoted bone formation. Such materials are of clinical interest because, they do not promote bacteria adhesion but, they support new bone formation, a condition which can lead to osseointegration of bone implants while preventing peri-implant infections.     

Hyrdoxyapatite Coatings on Titanium

Some ceramics, including calcium phosphates and certain glasses and glass‐ceramics, form an important class of bioactive materials that are used extensively in repair and reconstruction of diseased or damaged parts of the musculoskeletal system. The similarity between synthetic hydroxyapatite (HA) (Ca₁₀(PO₄)₆(OH)₂) and the mineral phase of bone and tooth made HA one of the earliest materials to be used to impart osteoconductive (bone‐bonding) properties to the surface of biocompatible, metallic implants. HA and other calcium phosphate surfaces are used primarily to cause early stabilization of the implant in the surrounding bone through the formation of a direct bond and enhanced bone apposition. Although bioactive ceramics are used in several compositions and forms, the focus here is on the use of HA coatings in metallic implants. The coatings made by commercially available plasma‐spray and other techniques are compared to those made recently by surface‐mediated biomimetic routes.     

Diatom‐Inspired Silica Nanostructure Coatings with Controllable Microroughness Using an Engineered Mussel Protein Glue to Accelerate Bone Growth on Titanium‐Based Implants

Silica nanoparticles (SiNPs) have been utilized to construct bioactive nanostructures comprising surface topographic features and bioactivity that enhances the activity of bone cells onto titanium‐based implants. However, there have been no previous attempts to create microrough surfaces based on SiNP nanostructures even though microroughness is established as a characteristic that provides beneficial effects in improving the biomechanical interlocking of titanium implants. Herein, a protein‐based SiNP coating is proposed as an osteopromotive surface functionalization approach to create microroughness on titanium implant surfaces. A bioengineered recombinant mussel adhesive protein fused with a silica‐precipitating R5 peptide (R5‐MAP) enables direct control of the microroughness of the surface through the multilayer assembly of SiNP nanostructures under mild conditions. The assembled SiNP nanostructure significantly enhances the in vitro osteogenic cellular behaviors of preosteoblasts in a roughness‐dependent manner and promotes the in vivo bone tissue formation on a titanium implant within a calvarial defect site. Thus, the R5‐MAP‐based SiNP nanostructure assembly could be practically applied to accelerate bone‐tissue growth to improve the stability and prolong the lifetime of medical implantable devices.     

NiTi shape memory alloys coated with calcium phosphate by plasma‐spraying. Chemical and biological properties

Plates of superelastic nickel‐titanium shape memory alloy (NiTi) were coated with calcium phosphate (hydroxyapatite) by high‐temperature plasma‐spraying. The porous layer of about 100 μm thickness showed a good adhesion to the metallic substrate that withstood bending of the plate but detached upon cutting the plate. The biocompatibility was tested by cultivation of blood cells (whole blood and isolated granulocytes [a subpopulation of blood leukocytes]). As substrates, pure NiTi, plasma‐spray‐coated NiTi and calcium phosphate‐coated NiTi prepared by a dip‐coating process were used. The adhesion of whole blood cells to all materials was not significantly different. In contrast, isolated granulocytes showed an increased adhesion to both calcium phosphate‐coated NiTi samples. However, compared to non‐coated NiTi or dip‐coated NiTi, the number of dead granulocytes adherent to plasma‐sprayed surfaces was significantly increased for isolated granulocytes (p<0.01).