Uncoated Titanium Research Articles

Reprint of "Biological characteristics of human fetal skin fibroblasts and MG-63 human osteosarcoma cells on tantalum-doped carbon films"

Tantalum is considered a highly biocompatible metal with high corrosion resistance. Metal-doped amorphous carbon films are gaining interest as an effective surface modifier for medical devices. In this study, tantalum (Ta), TaC/amorphous carbon (a-C), and Ta-containing amorphous hydrogenated carbon films (Ta-C:H) were synthesized using a twin-gun magnetron sputtering system to improve biological properties and explore potential applications for surgical implants or devices. Reactive C2H2, activated by the tantalum plasma in the magnetron sputtering process, was used to deposit the Ta-C:H coatings. The deposited TaC/a-C coatings, in which TaC was embedded in the amorphous carbon matrix as a nanocomposite film, exhibited favorable cell viability of the human osteosarcoma cell line (MG-63), similar to uncoated titanium. Among the examined materials, Ta-C:H coatings exhibited the highest biocompatibility for WS1 human fetal skin fibroblast cells derived from soft tissues and demonstrated the highest biological performance.

Determination of Surface and Hole Quality in Drilling of AISI D2 Cold Work Tool Steel Using MPMR, MARS and LSSVM

This paper adopts Minimax Probability Machine Regression (MPMR), Multivariate Adaptive Regression Spline (MARS), and Least Square Support Vector Machine (LSSVM) for prediction of surface and hole quality in drilling of AISI D2 cold work tool steel with uncoated titanium nitride (TiN) and titanium aluminum nitride (TiAlN) monolayer- and TiAlN/TiN multilayer-coated-cemented carbide drills. MPMR is a probabilistic model. MARS is a nonparametric regression technique. LSSVM is developed based on statistical learning algorithm. Cutting tool (t), Feed rate (fr)(mm/rev), and Cutting speed (v)(m/min) have been adopted as inputs of MPMR, MARS, and LSSVM. The output of MPMR, MARS, and LSSVM is Surface roughness (rs) (μm) and Roundness error (re) (μm). A comparative study has been presented between the developed models. The results show that the developed model gives excellent performance.

Fabrication, ultra-structure characterization and in vitro studies of RF magnetron sputter deposited nano-hydroxyapatite thin films for biomedical applications

A series of nanostructured low-crystalline hydroxyapatite (HA) coatings averaging 170, 250, and 440nm in thickness were deposited onto previously etched titanium substrates through radio-frequency (RF) magnetron sputtering. The HA coatings were analyzed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM). Cross sections of the thin specimens were prepared by FIB to study the microstructure of the coatings by TEM. The deposition process formed nano-scale grains, generating an amorphous layer at the substrate/coating interface and inducing the growth of a columnar grain structure perpendicular to the substrate surface. A microstructural analysis of the film confirmed that the grain size and crystallinity increased when increasing the deposition time. The nanostructured HA coatings were not cytotoxic, as proven by in vitro assays using primary dental pulp stem cells and mouse fibroblast NCTC clone L929 cells. Low-crystallinity HA coatings with different thicknesses stimulated cells to attach, proliferate and form mineralized nodules on the surface better than uncoated titanium substrates.

Ice Adhesion Mechanisms of Erosion-Resistant Coatings

The physical mechanism responsible for impact ice adhesion variations for different coatings is not well understood. This research examines the effects of surface characteristics on ice adhesion strength for three erosion-resistant materials. The materials tested were titanium grade 2, titanium aluminum nitride coated on titanium grade 2, and titanium nitride coated on titanium grade 2. The surface roughness of the material contributed to the ice adhesion strength but did not explain the variation in ice adhesion strength for materials at similar surface roughness values. To compare the materials, the ice adhesion strength was divided by the environmental temperature to allow for the comparison of ice adhesion measured at varying temperature conditions. The new quantity was called temperature-adjusted adhesion strength. When the surface roughness of the titanium grade 2 substrate increased from 26.4 to , the temperature-adjusted adhesion strength increased 29%. The titanium nitride temperature-adjusted adhesion strength increased 63% when the surface roughness increased from 23.2 to , and the titanium aluminum nitride temperature-adjusted adhesion strength increased by a factor of four. At the lowest surface roughness values tested, the temperature-adjusted adhesion strength of titanium nitride was 31% higher than the uncoated titanium grade 2 substrate, and the titanium aluminum nitride was 40% lower than the uncoated titanium grade 2. The temperature-adjusted adhesion strength of the coatings was 58% higher than the uncoated substrate across the three surface roughness values. Mechanical clamping was determined to be the primary mechanism for ice adhesion strength. Macrostructures with “cliff”-like structures, observed on the coatings via scanning electron microscope visualization, increased the ice adhesion strength over what would be predicted from a surface roughness characterization. These structures also explained the 40% increase in ice adhesion strength of a material subjected to oxidation.

Effect of zirconium nitride physical vapor deposition coating on preosteoblast cell adhesion and proliferation onto titanium screws

Titanium has long been used to produce dental implants. Problems related to its manufacturing, casting, welding, and ceramic application for dental prostheses still limit its use, which highlights the need for technologic improvements. The aim of this invitro study was to evaluate the biologic performance of titanium dental implants coated with zirconium nitride in a murine preosteoblast cellular model. The purpose of this study was to evaluate the chemical and morphologic characteristics of titanium implants coated with zirconium nitride by means of physical vapor deposition. Chemical and morphologic characterizations were performed by scanning electron microscopy and energy dispersive x-ray spectroscopy, and the bioactivity of the implants was evaluated by cell-counting experiments. Scanning electron microscopy and energy dispersive x-ray spectroscopy analysis found that physical vapor deposition was effective in covering titanium surfaces with zirconium nitride. Murine MC-3T3 preosteoblasts were seeded onto titanium-coated and zirconium nitride-coated screws to evaluate their adhesion and proliferation. These experiments found a significantly higher number of cells adhering and spreading onto zirconium nitride-coated surfaces (P<.05) after 24 hours; after 7 days, both titanium and zirconium nitride surfaces were completely covered with MC-3T3 cells. Analysis of these data indicates that the proposed zirconium nitride coating of titanium implants could make the surface of the titanium more bioactive than uncoated titanium surfaces.

Improved Bone Formation in Osteoporotic Rabbits with the Bone Morphogenetic Protein-2 (rhBMP-2) Coated Titanium Screws Which Were Coated By Using Plasma Polymerization Technique

Delaying of bone fusion in osteoporotic patients underwent spinal stabilization surgery leads to screw loosening, and this causes pseudoarticulation, mobility and fibrosis at vertebral segments. To prevent these complications, the screws coated with recombinant bone morphogenetic protein-2 (rhBMP-2) could be used. To verify this hypothesis, we coated 5 Titanium screws with rhBMP-2 using plasma polymerization method, and also used 10 uncoated screws for making comparison between coated and uncoated screws in different groups. And 15 skeletally mature white New Zealand female rabbits were assigned into three different groups: Group 1(N = 5): No osteoporosis induction and insertion of uncoated Titanium screw into right sacrum of each rabbit in group 1; group 2 (N = 5): Osteoporosis induction and insertion of uncoated Titanium screw into right sacrum of each rabbit in group 2; group 3 (N = 5) rhBMP-2 coated Titanium screw inserted into right sacrum of each rabbit in group 3. In summary, using of these coated screws provides new bone formation, but causes less fibrosis and less inflammation than uncoated screws at the interface between the coated screw and bone. Then the plasma polymerization technique provides controlled releasing of rhBMP-2 from the screw to the bone tissue in osteoporotic rabbits.

Improved Bone Formation in Osteoporotic Rabbits with the Bone Morphogenetic Protein-2 (rhBMP-2) Coated Titanium Screws Which Were Coated By Using Plasma Polymerization Technique

Delaying of bone fusion in osteoporotic patients underwent spinal stabilization surgery leads to screw loosening, and this causes pseudoarticulation, mobility and fibrosis at vertebral segments. To prevent these complications, the screws coated with recombinant bone morphogenetic protein-2 (rhBMP-2) could be used. To verify this hypothesis, we coated 5 Titanium screws with rhBMP-2 using plasma polymerization method, and also used 10 uncoated screws for making comparison between coated and uncoated screws in different groups. And 15 skeletally mature white New Zealand female rabbits were assigned into three different groups: Group 1(N = 5): No osteoporosis induction and insertion of uncoated Titanium screw into right sacrum of each rabbit in group 1; group 2 (N = 5): Osteoporosis induction and insertion of uncoated Titanium screw into right sacrum of each rabbit in group 2; group 3 (N = 5) rhBMP-2 coated Titanium screw inserted into right sacrum of each rabbit in group 3. In summary, using of these coated screws provides new bone formation, but causes less fibrosis and less inflammation than uncoated screws at the interface between the coated screw and bone. Then the plasma polymerization technique provides controlled releasing of rhBMP-2 from the screw to the bone tissue in osteoporotic rabbits.

Characterization and antibacterial performance of electrodeposited chitosan–vancomycin composite coatings for prevention of implant-associated infections

Orthopaedic implant-associated infections are one of the most serious complications in orthopaedic surgery and a major cause of implant failure. In the present work, drug-eluting coatings based on chitosan containing various amounts of vancomycin were prepared by a cathodic electrophoretic deposition process on titanium foils. A three-step release mechanism of the antibiotic from the films in a phosphate-buffered saline solution was noticed. At the early stage, physical encapsulation of the drug in the hydrogel network controlled the release rate. At the late stage, however, in vitro degradation/deattachment of chitosan was responsible for the controlled release. Cytotoxicity evaluation of the drug-eluting coatings via culturing in human osteosarcoma cells (MG-63 osteoblast-like cell line) showed no adverse effect on the biocompatibility. Antibacterial tests against Gram-positive Staphylococcus aureus also demonstrated that the infection risk of titanium foils was significantly reduced due to the antibiotic release. Additionally, in vitro electrochemical corrosion studies by polarization technique revealed that the corrosion current density was significantly lower for the titanium foils with drug-eluting coatings compared to that of uncoated titanium.

Fabrication of titanium bipolar plates by rubber forming and performance of single cell using TiN-coated titanium bipolar plates

In this study, a rubber forming method is used to fabricate titanium bipolar plates for proton exchange membrane fuel cells. A titanium blank with a thickness of 0.1 mm is compressed using a stamping mold equipped with a 200-ton hydraulic press to fabricate bipolar plates. A forming experiment is carried out by changing different parameters such as the punch velocity, punch pressure, rubber thickness, rubber hardness, and draft angle of the channel. The optimum forming conditions are found to be a rubber thickness of 10 mm, rubber hardness equivalent to that of Shore A 20, punch velocity of 30 mm s−1, punch pressure of 55 MPa, and punch draft angle of 30°. The fabricated titanium bipolar plate is coated with a TiN layer. A single cell with a TiN-coated titanium bipolar plate is examined and compared to those with uncoated titanium and graphite bipolar plates. The initial performances (in terms of current densities) of the single cells with the uncoated titanium, TiN-coated titanium, and graphite bipolar plates are 396, 799, and 1160 mA cm−2, respectively, at a cell voltage of 0.6 V.

Oxidation Resistance of AlPO4 Bonded Ceramic Coating Formed on Titanium Alloy for High‐Temperature Applications

AlPO4 based coatings were prepared on Ti‐6Al‐2Zr‐1Mo‐1V titanium alloy using aluminum phosphate as a binder and Al2O3/Cr2O3 based mixing particles as the fillers. The microstructure, phase and chemical composition of the coatings were analyzed by SEM, XRD and EDS techniques. The high temperature infrared emissivity values of coated and uncoated titanium samples were tested. The results show that the coating had a higher infrared emissivity value (&gt;0.8) than titanium substrate (0.15–0.3) in the wide wavelength range of 5–20 mm, which is attributed to the uniform dispersion of high emissivity Al2O3 and Cr2O3 particles in the AlPO4 binder matrix. The coated titanium samples exhibited excellent oxidation resistance performance with significantly decreased oxidation rates at 600 and 800°C. The mass gain of the coated sample kept at a low and stable constant of 0.15 mg/cm2, significantly lower than that of titanium substrate (0.54 mg/cm2) when oxidized at 600°C up to 100 h.

Design optimization of cementless hip prosthesis coating through functionally graded material

Many metals and its alloys that have been used in biomedical applications which carry the most applied load from the natural bone to the artificial joint. Consequently, this leads to causing stress shielding and bone osteoporotic. Therefore the optimization of the artificial hip materials is one of the challenging opportunities in prosthetic design. It is found from literature that there are contradictions due to the use of hydroxyapatite (HAP) as a coating material. In this study a finite element analysis and optimization method have been carried out in order to find a new design of the hip stem coating using functionally graded material (FGM). The using of FGM coating leads to diminishing stress shielding at the medial proximal region of the femur. In addition, it reduces the interface shear stress between the coating and bone that affects the long term stability of the hip implant. In this study the gradation of the Young’s modulus of the coating material changed through the vertical direction. Then the optimal design is compared with HAP coating and with homogenous uncoated titanium stem. The optimal design, in the case of a coating material which consists of HAP at the upper layer of the coating graded to collagen at the lower layer, is increase the maximum von Mises stress in bone at the medial proximal region of the femur by 65% and 19% compared to homogeneous titanium stem and titanium coated with HAP, respectively. The maximum lateral shear stress is reduced by 23% and 12%. However, the maximum medial shear stress is reduced by 39% and 14% compared to homogeneous titanium stem and titanium coated with HAP, respectively.

Biological characteristics of human fetal skin fibroblasts and MG-63 human osteosarcoma cells on tantalum-doped carbon films

Tantalum is considered a highly biocompatible metal with high corrosion resistance. Metal-doped amorphous carbon films are gaining interest as an effective surface modifier for medical devices. In this study, tantalum (Ta), TaC/amorphous carbon (a-C), and Ta-containing amorphous hydrogenated carbon films (Ta-C:H) were synthesized using a twin-gun magnetron sputtering system to improve biological properties and explore potential applications for surgical implants or devices. Reactive C2H2, activated by the tantalum plasma in the magnetron sputtering process, was used to deposit the Ta-C:H coatings. The deposited TaC/a-C coatings, in which TaC was embedded in the amorphous carbon matrix as a nanocomposite film, exhibited favorable cell viability of the human osteosarcoma cell line (MG-63), similar to uncoated titanium. Among the examined materials, Ta-C:H coatings exhibited the highest biocompatibility for WS1 human fetal skin fibroblast cells derived from soft tissues and demonstrated the highest biological performance.

Increased bone remodelling around titanium implants coated with chondroitin sulfate in ovariectomized rats

Coating titanium implants with artificial extracellular matrices based on collagen and chondroitin sulfate (CS) has been shown to enhance bone remodelling and de novo bone formation in vivo. The aim of this study was to evaluate the effect of estrogen deficiency and hormone replacement therapy (HRT) on the osseointegration of CS-modified Ti implants. 30 adult female, ovariectomized Wistar rats were fed either with an ethinyl-estradiol-rich diet (E) to simulate a clinical relevant HRT or with a genistein-rich diet (G) to test an alternative therapy based on nutritionally relevant phytoestrogens. Controls (C) received an estrogen-free diet. Uncoated titanium pins (Ti) or pins coated with type-I collagen and CS (Ti/CS) were inserted 8weeks after ovarectomy into the tibia. Specimens were retrieved 28days after implantation. Both the amount of newly formed bone and the affinity index (P<0.05) were moderately higher around Ti/CS implants as compared to uncoated Ti. The highest values were measured in the G-Ti/CS and E-Ti/CS groups, the lowest values for the E-Ti and G-Ti controls. Quantitative synchrotron radiation micro-computed tomography (SRμCT) revealed the highest increase in total bone formation around G-Ti/CS as compared to C-Ti (P<0.01). The effects with respect to direct bone apposition were less pronounced with SRμCT. Using scanning nanoindentation, both the indentation modulus and the hardness of the newly formed bone were highest in the E-Ti/CS, G-Ti/CS and G-Ti groups as compared to C-Ti (P<0.05). Coatings with collagen and CS appear to improve both the quantity and quality of bone formed around Ti implants in ovarectomized rats. A simultaneous ethinyl estradiol- and genistein-rich diet seems to enhance these effects.

Evaluation of Osseointegration of Titanium Alloyed Implants Modified by Plasma Polymerization

By means of plasma polymerization, positively charged, nanometre-thin coatings can be applied to implant surfaces. The aim of the present study was to quantify the adhesion of human bone cells in vitro and to evaluate the bone ongrowth in vivo, on titanium surfaces modified by plasma polymer coatings. Different implant surface configurations were examined: titanium alloy (Ti6Al4V) coated with plasma-polymerized allylamine (PPAAm) and plasma-polymerized ethylenediamine (PPEDA) versus uncoated. Shear stress on human osteoblast-like MG-63 cells was investigated in vitro using a spinning disc device. Furthermore, bone-to-implant contact (BIC) was evaluated in vivo. Custom-made conical titanium implants were inserted at the medial tibia of female Sprague-Dawley rats. After a follow-up of six weeks, the BIC was determined by means of histomorphometry. The quantification of cell adhesion showed a significantly higher shear stress for MG-63 cells on PPAAm and PPEDA compared to uncoated Ti6Al4V. Uncoated titanium alloyed implants showed the lowest BIC (40.4%). Implants with PPAAm coating revealed a clear but not significant increase of the BIC (58.5%) and implants with PPEDA a significantly increased BIC (63.7%). In conclusion, plasma polymer coatings demonstrate enhanced cell adhesion and bone ongrowth compared to uncoated titanium surfaces.

In vitro Assessment of Photocatalytic Titanium Oxide Surface-modified Stainless Steel and Nickel Titanium Orthodontic Wires for its Antiadherent and Antibacterial Properties against Streptococcus mutans

Objective: To assess the antiadherent and antibacterial pro­ perties of surface-modified stainless steel and nickel titanium orthodontic wires with photocatalytic titanium oxide against Streptococcus mutans (S. mutans). Materials and methods: This study was done on 80 specimens of orthodontic wires each of 5 cm in length. The specimens were divided into eight test groups, four groups were used for anti ­ adherent test, and other four groups were used for antibacterial test. Each group consisted of 10 specimens. The groups contain­ ing uncoated stainless steel and uncoated nickel titanium wires acted as control group for their respective experimental group, containing coated stainless steel and nickel titanium wires. Surface modification of both stainless steel and nickel titanium orthodontic wires with photocatalytic titanium oxide was carried out by sol gel thin film dip coating method. Orthodontic wires were then subjected to microbiological tests for assessment of the antiadherent and antibacterial properties of photocatalytic titanium oxide coating against S. mutans. Results: Photocatalytic TiO2 coating on the wires prevented the adhesion of S. mutans to the orthodontic wires, hence demonstrating antiadherent property against S. mutans. Also, photocatalytic TiO2 coating on the surface of orthodontic wires demonstrated antibacterial effect against S. mutans. Conclusion: Surface modification of orthodontic wires with photocatalytic titanium oxide was found to have antiadherent and antibacterial properties against S. mutans.

Characterization of Calcium Phosphate with an Anodic TiO&lt;sub&gt;2&lt;/sub&gt; Nanotube Layer on Titanium Screw for Biomedical Application

The present paper reports a novel solution to develop a calcium phosphates (CaPs) coating with an anodic nanotubular TiO2layer on titanium screw by electrochemical disposition (ECD). The elemental composition of coatings was examined by energy dispersive spectroscopy (EDS), the surface mopholoy was characterized with scanning electron microscopy (SEM), and the functional groups and crystalline phase were analyzed using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Furthermore, the bioactivity was tested by immersion in simulated body fluid (SBF) for 7 days. The results showed that a nanotubular TiO2layer was established which has about 100 mm diameter and the calcium phosphate coatings have higher bioactivity and porosity compared with uncoated titanium screws, which make the coating more conductive to cell adhesion. Using alkaline treatment, the calcium phosphate coating could transform into hydroxyapatite (HAp), making the coating closer to the biological complement. This provides a valuable tool for biomedical applications.

Blood compatibility and adhesion of collagen/heparin multilayers coated on two titanium surfaces by a layer-by-layer technique

This paper investigates the blood compatibility and adhesion of collagen/heparin multilayers coated on cp-Ti substrates with a layer-by-layer self-assembly technique. Two surface polishing processes were used for the titanium samples: one was mechanical polishing (MP) and the other, electropolishing (EP). These samples were pretreated by being immersed in NaOH solution to obtain a negatively charged surface with hydroxyl groups and then positively charged in poly-l-lysine solution. The repeated treatment of the samples by applying heparin and collagen alternately determined the number and thickness of the multilayers. The surface topography, chemical composition, and hydrophilicity of the films were investigated by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and water contact angle measurement. The study of the adhesion of the multilayer was conducted by a nano-scratch test. The blood compatibility was evaluated by measuring the hemolysis ratio and platelet-covered area in vitro. The uncoated titanium surface was used as the benchmark. The results indicated that the anticoagulation performance of collagen/heparin multilayers on the titanium surface was superior to that of the uncoated titanium surface. The hemolysis ratios of samples with an EP Ti substrate, a relatively rougher one, were essentially lower than those of samples with an MP substrate. The increase in the multilayers' thickness enhanced their adhesion to the Ti substrate.

Ultraviolet radiation and nanoparticle induced intracellular free radicals generation measured in human keratinocytes by electron paramagnetic resonance spectroscopy

Several nanoparticle-based formulations used in cosmetics and dermatology are exposed to sunlight once applied to the skin. Therefore, it is important to study possible synergistic effects of nanoparticles and ultraviolet radiation. Electron paramagnetic resonance spectroscopy (EPR) was used to detect intracellular free radicals induced by ultraviolet B (UVB) radiation and amorphous silica nanoparticle and to evaluate the influence of nanoparticle surface chemistry on particle cytotoxicity toward HaCaT cells. Uncoated titanium dioxide nanoparticles served as positive control. In addition, particle intracellular uptake, viability, and induction of interleukin-6 were measured. We found that photo-activated titanium dioxide particles induced a significant amount of intracellular free radicals. On the contrary, no intracellular free radicals were generated by the investigated silica nanoparticles in the dark as well as under UVB radiation. However, under UVB exposure, the non-functionalized silica nanoparticles altered the release of IL-6. At the same concentrations, the amino-functionalized silica nanoparticles had no influence on UVB-induced IL-6 release. EPR spectroscopy is a useful technique to measure nanoparticle-induced intracellular free radicals. Non-toxic concentrations of silica particles enhanced the toxicity of UVB radiation. This synergistic effect was not mediated by particle-generated free radicals and correlated with particle surface charge and intracellular distribution.

Bone‐derived titanium coating improves in vivo implant osseointegration in an experimental animal model

Coating of orthopaedic or dental Titanium (Ti) implants with extracellular bone matrix components (e.g., Type I collagen or hydroxyapatite) is usually performed to enhance their osseointegration. Aim of the present research is the evaluation of an innovative bone-derived Ti coating, containing bone apatite and Type I bone collagen preserved, in an experimental model. Coated and uncoated titanium implants were inserted into the extra-articular bone of the distal femur of twelve New Zealand White Rabbits. Labelling of bone formation was performed by sequential intraperitoneal administration of three stains. After 45 and 90 days animals were sacrificed. Bone specimens were embedded in a glycol methacrylate resin and sectioned along a plane parallel to the long axis of the implants for histomorphometric, scanning electron microscopy and energy dispersive X-ray analyses. Bone implant contact (BIC), trabecular thickness (Tb.Th) and calcium-phosphorus ratio were measured. Data were subjected to nonparametric Wilcoxon rank-sum test and Student's t test. All implants healed without adverse reactions. After 45 days from implant, significant (p < 0.05) differences in BIC (55.6 ± 17.1% vs. 29.2 ± 20.1%) and Tb.Th (108.7 ± 67.1 µm vs. 66.6 ± 48.6 µm) were observed between coated and uncoated implants. Significant (p < 0.05) differences in BIC (61.3 ± 2.1% vs. 35.7 ± 16.4%) and Tb.Th (211.4 ± 80.8 µm vs. 150.9 ± 61.5 µm) between coated and uncoated implants were also detected after 90 days. No differences were measured in calcium-phosphorous ratio. Our data indicate that Ti integration can be enhanced by the proposed surface coating. This could accelerate stable implant fixation and early or immediate loading of the device.

Salivary pellicles on titanium and their effect on metabolic activity in Streptococcus oralis

BackgroundTitanium implants in the oral cavity are covered with a saliva-derived pellicle to which early colonizing microorganisms such as Streptococcus oralis can bind. The protein profiles of salivary pellicles on titanium have not been well characterized and the proteins of importance for binding are thus unknown. Biofilm bacteria exhibit different phenotypes from their planktonic counterparts and contact with salivary proteins may be one factor contributing to the induction of changes in physiology. We have characterized salivary pellicles from titanium surfaces and investigated how contact with uncoated and saliva-coated titanium surfaces affects metabolic activity in adherent cells of S. oralis.MethodsSalivary pellicles on smooth titanium surfaces were desorbed and these, as well as purified human saliva, were subjected to two-dimensional gel electrophoresis and mass spectroscopy. A parallel plate flow-cell model was used to study binding of a fresh isolate of S. oralis to uncoated and saliva-coated titanium surfaces. Metabolic activity was assessed using the BacLight CTC Vitality Kit and confocal scanning laser microscopy. Experiments were carried out in triplicate and the results analyzed using Student’s t-test or ANOVA.ResultsSecretory IgA, α-amylase and cystatins were identified as dominant proteins in the salivary pellicles. Selective adsorption of proteins was demonstrated by the enrichment of prolactin-inducible protein and absence of zinc-α2-glycoprotein relative to saliva. Adherence of S. oralis to titanium led to an up-regulation of metabolic activity in the population after 2 hours. In the presence of a salivary pellicle, this effect was enhanced and sustained over the following 22 hour period.ConclusionsWe have shown that adherence to smooth titanium surfaces under flow causes an up-regulation of metabolic activity in the early oral colonizer S. oralis, most likely as part of an adaptation to the biofilm mode of life. The effect was enhanced by a salivary pellicle containing sIgA, α-amylase, cystatins and prolactin-inducible protein which was, for the first time, identified as an abundant component of salivary pellicles on titanium. Further studies are needed to clarify the mechanisms underlying the effect of surface contact on metabolic activity as well as to identify the salivary proteins responsible for enhancing the effect.