Design and fabrication of a Nb/NiTi superelastic composite with high critical stress for inducing martensitic transformation and large recoverable strain for biomedical applications.

A novel Nb/NiTi superelastic composite with a shell-core structure was designed and fabricated to achieve a combination of biocompatibility and superelasticity (large recoverable strain ε accompanied by high critical stress for inducing martensitic transformation σSIM). The good biocompatibility is mainly attributed to the outer non-cytotoxic Nb shell that prevents inner NiTi core from direct contact with cells. Meanwhile, the inner NiTi core endows the composite with superelasticity through a fully reversible stress-induced martensitic transformation between B2 parent phase and B19' martensite. These results might shed some light on design and development of novel superelastic composites for biomedical applications.

Does the antioxidant treatment affect the shear bond strength of orthodontic brackets: An in vitro study.

OBJECTIVE: To determine the shear bond strength of orthodontic brackets after anti-oxidant treatment on previously bleached teeth.. METHODS: The experimental in-vitro study was conducted in Saudi Arabiaat Qassim University, Al-Qassim, and King Saud University, Riyadh, from December 2016 to March 2017, and comprised extracted maxillary and mandibular premolars which were divided randomly into three groups. In Group A, which was the control group, the teeth were etched and bonded, while those in Group B were bleached, etched and bonded. Group C was subjected to bleaching, followed by treatment with anti-oxidant 10% sodium ascorbate solution, then etched and bonded. All three groups were then tested and analysed for bond strength using the Instron, Universal testing machine. SPSS 23 was used for data analysis.. RESULTS: There were 60 teeth with 20(33.3%) in each of the three groups. Group C had the maximum mean shear bond strength of 12.231}2.1Mpa, followed by Group A with 10.948+/-2.1Mpa and Group B with 7.621}1.8Mpa. CONCLUSIONS: Anti-oxidant treatment had a positive effect on the shear bond strength of orthodontic brackets after tooth bleaching. Keywords: Anti-oxidant. Bleaching, Brackets, Extracted premolars, Shear bond strength.

In vitro biocompatibility of orthodontic miniscrews with human gingival fibroblast and SAOS-2 osteoblast cultures.

PURPOSE: Miniscrews are an important choice for orthodontic anchorage. Yet reports on failures do exist, and attempts have been made to elucidate the causes. Clinical outcomes may be compromised not only by the mechanical implications of miniscrew design and the location of anchorage but also by poor biocompatibility. Hence, this study deals with the surface roughness and elemental composition of miniscrews and how these properties may affect the in vitro biocompatibility of four commercially available miniscrews. METHODS: Most of the currently available miniscrews are made of TiAl6V4, an alloy widely considered to be biocompatible. The samples tested in this study included four similarly dimensioned TiAl6V4 products from different manufacturers: tomas® by Dentaurum, OrthoEasy® by Forestadent®, Dual Top™ by Jeil Medical/Promedia, and LOMAS by Mondeal®. The surface properties of these products were characterized by scanning electron microscopy (SEM) and energy-dispersive X­ray spectroscopy (EDX). Cytotoxicity was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and agar overlay assays according to ISO 10993-5. RESULTS: The miniscrew products were found to show variations in surface-finish quality pertaining to topography and chemical composition, with the latter departing slightly from the manufacturers' specifications. MTT assays yielded rates of cell culture viability in excess of 90%, and agar overlay assays did not reveal decoloration beyond the specimen outlines in any of the experimental groups tested. CONCLUSIONS: The four miniscrew products exhibited some minor, but statistically significant, differences in microtopography, alloy composition, and biological inertness. Cytotoxicity testing revealed that all four products should be considered non-cytotoxic, thus, ruling out poor biocompatibility as a cause of miniscrew failure.

Study of Two-Body Wear Performance of Dental Materials.

INTRODUCTION: The purpose of this study was to evaluate the two-body wear resistances of natural enamel and four dental materials in vitro. METHODS: The testing machine was modified to form a type of pin-on-disk wear test apparatus. Four dental material specimens (Au-Pd alloy, Ag-Pd alloy, FiltekTMP60 and FiltekTMZ350 composite resins) and enamel were used as the pins, and a steatite ceramic grinding wheel was used as the abrasive counter face. The wear volume loss and the rigidity value was measured. The worn surface and the element analysis of the debris were analyzed. RESULT: The wear volume loss of Au-Pd alloy and its steatite antagonists were the nearest to those of the dental enamel. SEM microphotographs showed that, the main wear mechanism of the dental materials was abrasive and adhesive wear. CONCLUSIONS: Au-Pd alloy had good wear resistance and was more suitable for dental applications than other three dental materials.

Effect of preconditioning cobalt and nickel based dental alloys with Bacillus sp. extract on their surface physicochemical properties and theoretical prediction of Candida albicans adhesion.

Biofilm formation on dental biomaterials is implicated in various oral health problems. Thus the challenge is to prevent the formation of this consortium of microorganisms using a safe approach such as antimicrobial and anti-adhesive natural products. Indeed, in the present study, the effects of an antifungal extract of Bacillus sp., isolated from plant rhizosphere, on the surface physicochemical properties of cobalt and nickel based dental alloys were studied using the contact angle measurements. Furthermore, in order to predict the adhesion of Candida albicans to the treated and untreated dental alloys, the total free energy of adhesion was calculated based on the extended Derjaguin-Landau-Verwey-Overbeek approach. Results showed hydrophobic and weak electron-donor and electron-acceptor characteristics of both untreated dental alloys. After treatment with the antifungal extract, the surface free energy of both dental alloys was influenced significantly, mostly for cobalt based alloy. In fact, treated cobalt based alloy became hydrophilic and predominantly electron donating. Those effects were time-dependent. Consequently, the total free energy of adhesion of C. albicans to this alloy became unfavorable after treatment with the investigated microbial extract. A linear relationship between the electron-donor property and the total free energy of adhesion has been found for both dental alloys. Also, a linear relationship has been found between this latter and the hydrophobicity for the cobalt based alloy. However, the exposure of nickel based alloy to the antifungal extract failed to produce the same effect.

Screening on binary Ti alloy with excellent mechanical property and castability for dental prosthesis application.

In the present study, the microstructure, mechanical property, castability, corrosion behavior and in vitro cytocompatibility of binary Ti-2X alloys with various alloying elements, including Ag, Bi, Ga, Ge, Hf, In, Mo, Nb, Sn and Zr, were systematically investigated, in order to assess their potential applications in dental field. The experimental results showed that all binary Ti‒2X alloys consisted entirely α-Ti phase. The tensile strength and microhardness of Ti were improved by adding alloying elements. The castability of Ti was significantly improved by separately adding 2 wt.% Bi, Ga, Hf, Mo, Nb, Sn and Zr. The corrosion resistance of Ti in both normal artificial saliva solution (AS) and extreme artificial saliva solution (ASFL, AS with 0.2 wt.% NaF and 0.3 wt.% lactic acid) has been improved by separately adding alloying elements. In addition, the extracts of studied Ti‒2X alloys produced no significant deleterious effect to both fibroblasts L929 cells and osteoblast-like MG63 cells, indicating a good in vitro cytocompatibility, at the same level as pure Ti. The combination of enhanced mechanical properties, castability, corrosion behavior, and in vitro cytocompatibility make the developed Ti‒2X alloys have great potential for future stomatological applications.

Preventing Implant-Associated Infections by Silver Coating.

Implant-associated infections (IAIs) are a dreaded complication mainly caused by biofilm-forming staphylococci. Implant surfaces preventing microbial colonization would be desirable. We examined the preventive effect of a silver-coated titanium-aluminum-niobium (TiAlNb) alloy. The surface elicited a strong, inoculum-dependent activity againstStaphylococcus epidermidisandStaphylococcus aureusin an agar inhibition assay. Gamma sterilization and alcohol disinfection did not alter the effect. In a tissue cage mouse model, silver coating of TiAlNb cages prevented perioperative infections in an inoculum-dependent manner and led to a 100% prevention rate after challenge with 2 × 10(6)CFU ofS. epidermidisper cage. InS. aureusinfections, silver coating had only limited effect. Similarly, daptomycin or vancomycin prophylaxis alone did not preventS. aureusinfections. However, silver coating combined with daptomycin or vancomycin prophylaxis thwarted methicillin-resistantS. aureusinfections at a prevention rate of 100% or 33%, respectively. Moreover, silver release from the surface was independent of infection and occurred rapidly after implantation. On day 2, a peak of 82 µg Ag/ml was reached in the cage fluid, corresponding to almost 6× the MIC of the staphylococci. Cytotoxicity toward leukocytes in the cage was low and temporary. Surrounding tissue did not reveal histological signs of silver toxicity.In vitro, no emergence of silver resistance was observed in several clinical strains of staphylococci upon serial subinhibitory silver exposures. In conclusion, our data demonstrate that silver-coated TiAlNb is potent for prevention of IAIs and thus can be considered for clinical application.

Microstructure, mechanical properties, castability and in vitro biocompatibility of Ti-Bi alloys developed for dental applications.

In this study, the microstructure, mechanical properties, castability, electrochemical behaviors, cytotoxicity and hemocompatibility of Ti-Bi alloys with pure Ti as control were systematically investigated to assess their potential applications in the dental field. The experimental results showed that, except for the Ti-20Bi alloy, the microstructure of all other Ti-Bi alloys exhibit single α-Ti phase, while Ti-20Bi alloy is consisted of mainly α-Ti phase and a small amount of BiTi2 and BiTi3 phases. The tensile strength, hardness and wear resistance of Ti-Bi alloys were demonstrated to be improved monotonically with the increase of Bi content. The castability test showed that Ti-2Bi alloy increased the castability of pure Ti by 11.7%. The studied Ti-Bi alloys showed better corrosion resistance than pure Ti in both AS (artificial saliva) and ASFL (AS containing 0.2% NaF and 0.3% lactic acid) solutions. The concentrations of both Ti ion and Bi ion released from Ti-Bi alloys are extremely low in AS, ASF (AS containing 0.2% NaF) and ASL (AS containing 0.3% lactic acid) solutions. However, in ASFL solution, a large number of Ti and Bi ions are released. In addition, Ti-Bi alloys produced no significant deleterious effect to L929 cells and MG63 cells, similar to pure Ti, indicating a good in vitro biocompatibility. Besides, both L929 and MG63 cells perform excellent cell adhesion ability on Ti-Bi alloys. The hemolysis test exhibited that Ti-Bi alloys have an ultra-low hemolysis percentage below 1% and are considered nonhemolytic. To sum up, the Ti-2Bi alloy exhibits the optimal comprehensive performance and has great potential for dental applications.

Effect of Nd:YAG laser parameters on the penetration depth of a representative Ni-Cr dental casting alloy.

The effects of voltage and laser beam (spot) diameter on the penetration depth during laser beam welding in a representative nickel-chromium (Ni-Cr) dental alloy were the subject of this study. The cast alloy specimens were butted against each other and laser welded at their interface using various voltages (160-390 V) and spot diameters (0.2-1.8 mm) and a constant pulse duration of 10 ms. After welding, the laser beam penetration depths in the alloy were measured. The results were plotted and were statistically analyzed with a two-way ANOVA, employing voltage and spot diameter as the discriminating variables and using Holm-Sidak post hoc method (a = 0.05). The maximum penetration depth was 4.7 mm. The penetration depth increased as the spot diameter decreased at a fixed voltage and increased as the voltage increased at a fixed spot diameter. Varying the parameters of voltage and laser spot diameter significantly affected the depth of penetration of the dental cast Ni-Cr alloy. The penetration depth of laser-welded Ni-Cr dental alloys can be accurately adjusted based on the aforementioned results, leading to successfully joined/repaired dental restorations, saving manufacturing time, reducing final cost, and enhancing the longevity of dental prostheses.

The effect of APH treatment on surface bonding and osseointegration of Ti-6Al-7Nb implants: an in vitro and in vivo study.

This study investigated the effects of anodization-cyclic precalcification-heat (APH) treatment on the bonding ability of Ca-P coating to the parent metal and osseointegration of Ti-6Al-7Nb implants. Eighteen Ti-6Al-7Nb discs, 9 untreated and 9 APH-treated, were cultured with osteoblast cells in vitro, and the cellular differentiation ability was assayed at 1, 2, and 3 weeks. For in vivo testing, 28 Ti-6Al-7Nb implants (14 implants of each group) were inserted to rat tibias, and after each 4 and 6 weeks of implantation, bone bonding, and osseointegration were evaluated through removal torque and histological analysis. Osteoblast-culturing showed twice as much of the alkaline phosphatase activity on the treated surface at 3 weeks than on the untreated surface (p < 0.05). The treated implants exhibited higher removal torque values than the untreated ones (15.5 vs. 1.8 Ncm at 4 weeks and 19.7 vs. 2.6 Ncm at 6 weeks, p < 0.05). Moreover, the excellent bonding quality of coats was confirmed by the existence of cohesive fractures on the surface of removed APH implants (field emission scanning electron microscopy and histological observation). Within the limits of this study, it can be concluded that the APH treatment significantly enhanced osseointegration of the Ti-6Al-7Nb implant, with the stable bonding between the coating and the implant surface.

Experimental titanium alloys for dental applications.

STATEMENT OF PROBLEM: Although the use of titanium has increased, casting difficulties limit routine use. PURPOSE: The purpose of the present study was to compare the mechanical properties and biocompatibility of the experimental titanium alloys titanium-5-zirconium, titanium-5-tantalum, and titanium-5-tantalum-5-zirconium (in wt%) with those of commercially pure titanium. MATERIAL AND METHODS: Specimens of titanium alloys and commercially pure titanium were cast by using plasma. Their modulus of elasticity and ultimate tensile strength were determined in a universal testing machine. Biocompatibility was evaluated with SCC9 cells. In periods of 1, 4, 7, 10, and 14 days, cell proliferation was evaluated by the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium reduction assay, and cell viability was evaluated in the 7-day period. Cell morphology was evaluated at 2, 12, and 24 hours. Modulus of elasticity, ultimate tensile strength, and cell viability were analyzed by 1-way ANOVA and the Bonferroni test; cell proliferation data were compared by 2-way ANOVA (alloy versus time) and by the Bonferroni test; and the cell morphology data were analyzed by split-plot design. All statistical tests were performed at the 95% confidence level (P<.05). RESULTS: Titanium-5-tantalum presented the lowest modulus of elasticity and ultimate tensile strength, whereas titanium-5-zirconium and titanium-5-tantalum-5-zirconium were statistically similar to commercially pure titanium. Cell proliferation and viability were not affected by any alloy being similar to those observed for commercially pure titanium. No noticeably differences were found in the morphology of cells cultured on any alloy and commercially pure titanium. CONCLUSION: Experimental alloys, especially titanium-5-zirconium and titanium-5-tantalum-5-zirconium, presented promising mechanical results for future studies and clinical applications. In addition, these alloys, evaluated by cell proliferation, viability, and morphology, were found to be biocompatible in vitro.

The effect of the solute on the structure, selected mechanical properties, and biocompatibility of Ti-Zr system alloys for dental applications.

New titanium alloys have been developed with the aim of utilizing materials with better properties for application as biomaterials, and Ti-Zr system alloys are among the more promising of these. In this paper, the influence of zirconium concentrations on the structure, microstructure, and selected mechanical properties of Ti-Zr alloys is analyzed. After melting and swaging, the samples were characterized through chemical analysis, density measurements, X-ray diffraction, optical microscopy, Vickers microhardness, and elasticity modulus. In-vitro cytotoxicity tests were performed on cultured osteogenic cells. The results showed the formation essentially of the α' phase (with hcp structure) and microhardness values greater than cp-Ti. The elasticity modulus of the alloys was sensitive to the zirconium concentrations while remaining within the range of values of conventional titanium alloys. The alloys presented no cytotoxic effects on osteoblastic cells in the studied conditions.

Ti-Ga binary alloys developed as potential dental materials.

In this study, the microstructure, mechanical properties, castability, electrochemical behaviors and cytotoxicity of as-cast Ti-Ga alloys with pure Ti as control were systematically investigated to assess their potential application in dental field. The results of OM and XRD showed that the microstructure of all experimental as-cast Ti-Ga alloys exhibited single α-Ti phase at room temperature. Mechanical tests indicated that the tensile strength, Young's modulus, microhardness and wear resistance were improved monotonically with the increase of Ga content. The castability test showed that Ti-2Ga alloy increased the castability value of pure Ti by 14.2(±3.8)% (p<0.05). The electrochemical behaviors in both artificial saliva solutions indicated that the studied Ti-Ga alloys showed better corrosion resistance than pure Ti. The cytotoxicity test suggested that the studied Ti-Ga alloys produced no significant deleterious effect to L929 fibroblast cells and MG63 osteosarcoma cells, similar to pure Ti, indicating an excellent in vitro biocompatibility. The cell morphology test showed that both L929 and MG63 cells process excellent cell adhesion ability on all experimental materials. Considering all these results, Ti-2Ga alloy exhibits the optimal comprehensive performance and has potential for dental applications.

Oral factors affecting titanium elution and corrosion: an in vitro study using simulated body fluid.

OBJECTIVES: Ti, which is biocompatible and resistant to corrosion, is widely used for dental implants, particularly in patients allergic to other materials. However, numerous studies have reported on Ti allergy and the in vitro corrosion of Ti. This study investigated the conditions that promote the elution of Ti ions from Ti implants. METHODS: Specimens of commercially pure Ti, pure nickel, a magnetic alloy, and a gold alloy were tested. Each specimen was immersed in a simulated body fluid (SBF) whose pH value was controlled (2.0, 3.0, 5.0, 7.4, and 9.0) using either hydrochloric or lactic acid. The parameters investigated were the following: duration of immersion, pH of the SBF, contact with a dissimilar metal, and mechanical stimulus. The amounts of Ti ions eluted were measured using a polarized Zeeman atomic absorption spectrophotometer. RESULTS: Eluted Ti ions were detected after 24 h (pH of 2.0 and 3.0) and after 48 h (pH of 9.0). However, even after 4 weeks, eluted Ti ions were not detected in SBF solutions with pH values of 5.0 and 7.4. Ti elution was affected by immersion time, pH, acid type, mechanical stimulus, and contact with a dissimilar metal. Elution of Ti ions in a Candida albicans culture medium was observed after 72 h. SIGNIFICANCE: Elution of Ti ions in the SBF was influenced by its pH and by crevice corrosion. The results of this study elucidate the conditions that lead to the elution of Ti ions in humans, which results in implant corrosion and Ti allergy.

In-vitro assessment of oxidative stress generated by orthodontic archwires.

INTRODUCTION: Several metals undergo redox cycling, producing free radicals and generating oxidative stress. The purpose of this study was to investigate in-vitro oxidative stress of orthodontic archwires made of various alloys. METHODS: Mouse fibroblast cells L929 were exposed to 6 types of archwires, and the concentration of the oxidative stress marker 8-hydroxy-2'-deoxyguanosine in DNA was evaluated. Trypan blue dye was used in the determination of cell viability and numbers. RESULTS: Standard nickel-titanium archwires generated the highest oxidative stress, significantly higher than all other wires and the controls (P <0.05), and coated nickel-titanium, copper-nickel-titanium, and cobalt-chromium were lower than nickel-titanium (P <0.05), but higher than titanium-molybdenum and the negative and absolute controls (P <0.05). Titanium-molybdenum and stainless steel generated the lowest stress. Nickel-titanium induced the lowest viability, lower than the negative and absolute controls and all other wires (P <0.05) except titanium-molybdenum. Stainless steel showed the highest viability. Nickel-titanium produced the highest inhibition of cell growth, higher than all samples (P <0.05) except the positive control and cobalt-chromium. The lowest inhibition was observed in stainless steel and titanium-molybdenum, lower than nickel-titanium, cobalt-chromium, and the positive control (P <0.05). CONCLUSIONS: All orthodontic archwires generate oxidative stress in vitro. Stainless steel archwires have the highest and nickel-titanium the lowest biocompatibility.

Effect of surface treatment on cell responses to grades 4 and 5 titanium for orthodontic mini-implants.

INTRODUCTION: Mini-implants are used to improve orthodontic anchorage, but optimal composition and surface characteristics have yet to be determined. We investigated the behavior of osteoblast-like cells on grade 4 commercially pure titanium and grade 5 titanium alloy with different surface treatments for mini-implants. METHODS: MC3T3 cells were plated on machined, acid-etched, or acid-etched grade 4 titanium enriched with calcium phosphate, or machined, anodized, or anodized and calcium phosphate-enriched grade 5 titanium disks. Surface and cell morphologies were assessed by scanning electron microscopy. Cell viability was measured by chemiluminescence, cytoskeletal organization was investigated by immunofluorescence, and real-time polymerase chain reaction for osteoblast-specific genes was performed to measure cell differentiation. RESULTS: Flattened shapes and strong stress fibers were observed on the machined surfaces; cells on the rough surfaces had a spindle shape, with lower cytoskeletal polarization. Cell proliferation was highest on smooth grade 4 titanium surfaces, whereas cells quickly reached a plateau on rough grade 4 titanium; no difference was observed after 72 hours in the grade 5 titanium groups. Calcium phosphate enrichment on grade 4 titanium significantly increased the messenger RNA levels for alkaline phosphatase and osteocalcin. Osteoblastic markers were higher on the grade 5 titanium machined surfaces than on the rough surfaces, and comparable with acid-etched grade 4 titanium. CONCLUSIONS: Although the grade 4 titanium enriched with calcium phosphate had the highest level of differentiation in vitro, the grade 5 titanium machined surfaces supported cell proliferation and matrix synthesis, and induced high expression of early differentiation markers. Increased mechanical resistance of grade 5 titanium makes it a potential candidate for orthodontic mini-implants.

In vitro oxidative stress induced by conventional and self-ligating brackets.

OBJECTIVE: To determine the in vitro oxidative stress induced by conventional and self-ligating brackets made of different materials. MATERIALS AND METHODS: The concentration of oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) in DNA of murine fibroblast cells L929 after in vitro exposure to three types of conventional and four types of self-ligating brackets was assessed. To determine viability and changes in the number of cells before and after exposure, trypan blue dye was used. Analysis of variance (ANOVA) was used for statistical analysis. RESULTS: No significant difference in cell viability was noted between metal, ceramic, and polymeric conventional brackets, and self-ligating brackets made of combinations of those materials, but viability was significantly higher compared with positive controls (P < .05). The conventional sapphire ceramic bracket (Inspire Ice) showed high viability, the largest increase in the number of cells, and the lowest oxidative stress. A higher concentration of markers of oxidative stress was observed in full metal conventional and self-ligating brackets (MiniSprint and Speed) and in conventional polyurethane brackets (Quantum) compared with negative controls (P < .05). CONCLUSION: All types of orthodontic brackets, regardless of the constituent materials, are a source of oxidative stress in vitro, but the highest stress was induced in the full metal and polyurethane brackets. Conventional ceramic brackets show the highest degree of biocompatibility compared with polymeric and metal brackets and self-ligating brackets made from combinations of these materials.

Oral mucosa tissue response to titanium cover screws.

BACKGROUND: Titanium is the most widely used metal in dental implantology. The release of particles from metal structures into the biologic milieu may be the result of electrochemical processes (corrosion) and/or mechanical disruption during insertion, abutment connection, or removal of failing implants. The aim of the present study is to evaluate tissue response of human oral mucosa adjacent to titanium cover screws. METHODS: One hundred fifty-three biopsies of the supra-implant oral mucosa adjacent to the cover screw of submerged dental implants were analyzed. Histologic studies were performed to analyze epithelial and connective tissue as well as the presence of metal particles, which were identified using microchemical analysis. Langerhans cells, macrophages, and T lymphocytes were studied using immunohistochemical techniques. The surface of the cover screws was evaluated by scanning electron microscopy (SEM). RESULTS: Forty-one percent of mucosa biopsies exhibited metal particles in different layers of the section thickness. Particle number and size varied greatly among specimens. Immunohistochemical study confirmed the presence of macrophages and T lymphocytes associated with the metal particles. Microchemical analysis revealed the presence of titanium in the particles. On SEM analysis, the surface of the screws exhibited depressions and irregularities. CONCLUSIONS: The biologic effects seen in the mucosa in contact with the cover screws might be associated with the presence of titanium or other elements, such as aluminum or vanadium. The potential long-term biologic effects of particles on soft tissues adjacent to metallic devices should be further investigated because these effects might affect the clinical outcome of the implant.

Surface modification and its effect on attachment, spreading, and proliferation of human gingival fibroblasts.

PURPOSE: The purpose of this study was to exploit potential methods of surface modification for improving the seal between the neck portion of a dental implant and the surrounding soft tissue. MATERIALS AND METHODS: Titanium surfaces were modified by machining (SM-Ti group); machining and acid etching (AE-Ti group); or machining, acid etching, and depositing 4.5 collagen/hyaluronic acid (col/HA) polyelectrolyte bilayers (CHC-Ti group). These were analyzed using scanning electron microscopy, scanning force microscopy, x-ray photoelectron spectroscopy, contact angle measurement, and quartz crystal microbalance measurement. The degradation behavior of the col/HA multilayer coating was measured. Next, human gingival fibroblasts (HGFs) were cultured on the different surfaces, and cell morphology and spreading were observed using fluorescence microscopy and a shape factor measurement. Cell proliferation was examined by fluorometric quantification of the amount of cellular DNA. Matrix formation of HGFs was determined via enzyme-linked immunosorbent assay. Gene expression was analyzed via reverse transcriptase polymerase chain reaction. RESULTS: Similar surface topology for these three groups was observable on a microscopic scale, and morphologic differences were apparent on the nanoscale. Both acid etching and col/HA deposition improved the hydrophilicity of the titanium surface, in contrast to machining alone. Each col/HA bilayer was about 5 nm thick. The col/HA coating degraded in about a week. Attachment and spreading of HGFs was better on the CHC-Ti surface than on the SM-Ti or AE-Ti surfaces. Moreover, the proliferation and differentiation of HGFs were greatly stimulated when cultured on CHC-Ti. CONCLUSION: In contrast to two control surfaces (one machined, one machined and acid-etched), col/HA treatment of Ti improved the attachment, spreading, proliferation, and differentiation of HGFs.

The influence of different implant materials on human gingival fibroblast morphology, proliferation, and gene expression.

PURPOSE: The aim of this study was to investigate the cellular response of human gingival fibroblasts (HGFs) cultured on smooth or rough zirconia (Zr) or titanium (Ti) disks. MATERIALS AND METHODS: Disks fabricated from four different materials--smooth Zr (Zr-S), rough Zr (Zr-R), smooth Ti (Ti-S), and rough Ti (Ti-R)--were used, and surface roughness was analyzed by atomic force microscopy. After HGFs were cultured on these disks, cell morphology was examined by scanning electron microscopy, cell proliferation activity was evaluated by a monotetrazolium assay, and gene expression levels of various collagens and integrins were measured by real-time polymerase chain reaction. RESULTS: The Ti-R disks were the roughest, followed by Zr-R, Ti-S, and Zr-S, in that order. The cells cultured on the Zr-S and Ti-S disks appeared to be more aligned with the fine irregularities at later time points, whereas the cells cultured on the Zr-S showed the weakest spreading compared to the other surfaces after 3 hours of culture. With respect to proliferation, cells proliferated significantly faster on the Zr-S surface than on the other surfaces. Gene expression of integrin α2 at 3 hours and integrin α5 and type I collagen at 48 hours on Zr-S was significantly up-regulated compared to Ti. Conversely, the expression of integrins ß1 and ß3 and type III collagen was significantly decreased on Zr-S at 1 hour compared to the other materials. CONCLUSION: These data indicate that different surface materials and topographies may induce a distinct HGF morphology, proliferation, and gene expression.