Double Etching Research Articles

Morphological and Chemical Characterization of Titanium and Zirconia Dental Implants with Different Macro- and Micro-Structure

Background: The aim of this study was to evaluate the macro- and micro-structure and the chemical composition of the surface of 5 different commercially available dental implants. Roughness values were also calculated. Materials and Methods: 1 zirconia implant (NobelPearl of Nobel Biocare) and 4 titanium implants, Syra (Sweden&Martina), Prama (Sweden&Martina), T3 (Biomet 3i), and Shard (Mech&Human), were analyzed through SEM-EDX analysis and quantitative evaluation of surface roughness (1 sample), and XPS chemical analysis (1 sample). Surface roughness was quantitatively assessed using the stereo-SEM method (SSEM). The following area roughness parameters were calculated, according to ISO25178: Sa, Sz, and Sdr. Results: From the SEM observations, all the implants analyzed presented modern well-developed micro-structures as the result of the specific process of double acid etching alone or combined with other additional treatments. Roughness values were generally greater at the level of the implant body and lower at the collar. The chemical characterization of the implant surfaces exhibited excellent results for all of the implants and indicated good care in the production processes. Conclusions: All the samples were well-conceived in terms of topography and surface roughness, and clean in terms of chemical residues.

Insights into the structural and surface characteristics of microporous carbide derived carbons obtained through single and double halogen etching

Carbide derived carbons CDC are prepared from polymeric preceramic precursors by incorporating different amounts of a divinylbenzene and heat treated at different temperatures. The effects of a single (Cl 2 ) and double (HF + Cl 2 ) etching treatment have been studied. The amount of divinlylbenzene incorporated into the preceramic precursor will determine the relative amount of linear to highly crosslinked silica units therefore the sensitivity to the etching process. The obtained microporous materials possess a self-similar surface and different microstructure depending on the temperature and the etching treatment which inevitably affect the electrochemical characteristics. Wet etching reduced the amount of zigzag edges in the microporous carbon thus contributing to the decrease of the areal capacitance. In the case of a single etching, the capacitance increases with the relative number of armchair to armchair + zigzag edges only when the materials were treated at high temperature. On contrary, by double etching treatment, the electrochemical characteristics are strongly related to the pore anisotropy independently on the temperature of the treatment. In this study we provide several clues for the design of highly capacitive microporous carbons from preceramic polymers with a view in the pore architecture, surface characteristics, defects, disorder and reactivity of the carbon edges. • Microporous carbide derived carbons with SSA up to 1900 m 2 /g synthesized from preceramic polymers. • Wet and dry etching is applied to modify the surface and structural properties. • Wet etching reduced the amount of defective sites in carbon thus decreasing the areal capacitance. • Rising the specific capacitance is achieved by increasing the pore anisotropy and double etching.

Controllable growth of Ga2O3 hexagonal prism with pyramid end and monitoring size-dependent electron transfer process in perylene/Ga2O3 conjugate system via FLIM

Hexagonal prisms with hexagonal pyramid end of Ga2O3 microstructures were successfully prepared on gallium arsenide substrate by double cell electrochemical etching method under various growth conditions. The field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and fluorescence lifetime imaging microscopy (FLIM) were used to characterize the hexagonal prisms. The EDS analysis confirmed that the prepared prisms were composed dominantly of gallium (Ga) and oxygen (O) with atomic ratio of ~ 2:3. The binding energy of the Ga 2p and Ga 3d XPS peaks revealed that the formation of Ga–O bonding with the highest oxidation state of Ga (Ga3+) and the formed hexagonal microstructures were Ga2O3. The PL spectra at room temperature under excitation at 290 nm exhibit a strong blue emission peak located at about 470 nm. The origin of this PL peak can be attributed to exciton recombination at different intrinsic defect sites such as O vacancies and Ga vacancies. Moreover, FLIM technique has been employed to probe time-resolved photoluminescence properties of individual Ga2O3 prisms with hexagonal tip. FLIM images provide two-dimensional spatial maps of the carrier recombination lifetime which considered the most critical parameter to improve the performance of optoelectronic devices. It has been concluded that the carrier recombination lifetime was strongly sensitive to the size of the hexagonal prism-shaped structures due to surface-related defects. Additionally, a quantitative analysis of a conjugate system prepared by functionalizing hexagonal Ga2O3 prisms with perylene organic dye molecules was reported in this work. The size-dependent electronic coupling between the conduction band level of gallium oxide and excited states of perylene molecules was investigated. We observed that highly efficient electron transfer process occurs for aggregated molecules due to excimer trap states. The grown prism structures seem to be interesting for applications in optoelectronic devices as well as to be used as an effective host medium for organic dye molecules in solar cell applications.

Evaluation of bond strength of resin cement to Er:YAG laser-etched enamel and dentin after cementation of ceramic discs.

The purpose of this study was to investigate the shear bond strength (SBS) of ceramic discs luted to differently etched enamel and dentin surfaces. Occlusal surfaces of 64 carious-free human molars and vestibule surfaces of 64 first maxillary incisors were ground to get flat superficial dentin and flattened enamel respectively. After generating 4 groups according to the surface etching method (37% orthophosphoric acid, Er:YAG laser-contact handpiece/scanning handpiece (1 or 2 times of scanning)), ceramic discs were luted to the surfaces with adhesive resin cement (Variolink N, Vivadent Ets., Schaan/Liechtenstein). After etching and cementation, thermocycling of 5000cycles (Sd Mechatronık Gmbh, Feldkirchen-Westerham, Germany) and SBS test (Servopulser EHFFD1; Shimadzu, Kyoto, Japan) were performed respectively. The surface morphologies of 2 specimens, etched enamel and dentin, prepared for each group were examined with SEM analysis. Failure modes were determined under a USB digital microscope. Data were analyzed with one-way analysis of variance (ANOVA) and Tukey HSD test (α = 0.05). SBS values in dentin surfaces showed statistically significant differences (p < 0.05) among tested groups. The highest SBS among dentin groups was determined in the group which had 2 times etching by Er:YAG laser (11.42MPa) by a scanning handpiece. No statistical differences were observed in the other dentin or enamel groups. Laser etching seems to be a viable alternative to acid etching on both enamel and dentin surfaces while double etching of dentin with a scanning handpiece can improve the adhesion.

Osteoblastic Cell Behavior and Early Bacterial Adhesion on Macro-, Micro-, and Nanostructured Titanium Surfaces for Biomedical Implant Applications.

Surface treatments may significantly affect physical-chemical properties and surface biologic responses. This study aimed to investigate the influence of alterations in the physical-chemical properties of pure titanium with different surface topographies on biocompatibility and early microbiologic response. Titanium disks were exposed to five different surface treatments created through acid etching and anodizing methods. Surface morphology, 2D and 3D roughness, wettability, biocompatibility, and cell viability were evaluated. Osteoblast adhesion and bacterial adhesion tests were also executed. Data were statistically analyzed using analysis of variance followed by Tukey test, roughness (P < .05), and bacterial proliferation (P < .05). Five different surface morphologies were developed; double acid etching was shown to be significantly rougher than the others. The 2D roughness measurements were shown to be less consistent than the 3D measurements. All surfaces presented biocompatibility to allow cell behavior and differentiation. Osteoblasts presented better evolution in terms of adhesion and behavior in the nanomorphologies. High roughness significantly increased bacterial adhesion. Surface treatments may critically alter titanium properties and morphology. Therefore, roughness measurements with a wide area should be used in their evaluation. Nanotextured surfaces show a positive effect on bone cells and antibacterial response; their application is suggested when considering surface texturization for biomedical implants.

Improved osteointegration by SEW2871-encapsulated multilayers on micro-structured titanium via macrophages recruitment and immunomodulation

The main task for medical-used titanium researches is to improve the in vivo osteointegration. In addition to mesenchymal stromal cells (MSCs)-osteoblasts lineage, macrophages also undertake irreplaceable roles in the osteointegration process of a titanium implant. The timely recruitment and efficient immunomodulation of macrophages is important. In this work, to firstly endow macrophages recruitment ability and immunomodulation effects to titanium, we fabricated a micro-structured titanium via a double acid etching method. Then a gelatin-chitosan multilayer contained SEW2871 (a macrophage recruitment agent) was constructed on the micro-structured titanium by a layer-by-layer (LBL) self-assembly technique. According to our results, the prepared samples effectively induced macrophages migration when SEW2871 was slowly released. The anti-inflammatory response of macrophages was enhanced and the pro-inflammatory response was alleviated, which were attributed to the changed surface roughness and wettability. This immunomodulation effects of macrophages further improved the osteogenic differentiation of MSCs in vitro and obtained a better osteointegration in vivo after 6 weeks of implantation. Therefore, this study demonstrated that a favorable osteointegration of titanium materials could also be achieved by regulating macrophages recruitment and immunomodulation, which implying a potential strategy for titanium implants amelioration.

The Evaluation of Osteoblastic Cell Behavior on Treated Titanium Surface

Background: There are several potential advantages in optimizing the initial events of osseointegration in the benefit of clinical outcome. Objective: The objective of the present study was to evaluate the behavior of osteoblastic cells on surfaces treated by double acid etching using HNO3 and H2SO4. Methods: Commercially pure titanium (grade 4) discs measuring 6 mm in diameter and 2 mm in thickness were used. The discs were divided into two groups: machined group and double acid-etched discs (HNO3 and H2SO4). Surface characteristics were assessed using Scanning Electron Microscopy. Pre-osteoblastic MC3T3-E1 cells were used for cell culture on the tested surfaces to assess proliferation, viability (MTT), as well as secretion (ELISA) and cytoplasmic expression (Western blot) of type I collagen. Results: The data obtained were analyzed using t-test or two-way ANOVA followed by Bonferroni’s test at 95% significance. The titanium surfaces showed average roughness values for the machined and treated surfaces of 0.29 and 1.16, respectively (p&lt;0.05). An increase in cell proliferation was observed, which was corroborated by the viability assay. Both type I collagen secretion and intracellular expression were higher on the double acid-etched surface compared to the machine surfaces (p&lt;0.05). Conclusion: Implant surfaces treated by double acid etching positively affected the early events of the interaction between titanium and osteoblastic cells, suggesting optimization of osseintegration.

The Evaluation of Osteoblastic Cell Behavior on Treated Titanium Surface

Background: There are several potential advantages in optimizing the initial events of osseointegration in the benefit of clinical outcome. Objective: The objective of the present study was to evaluate the behavior of osteoblastic cells on surfaces treated by double acid etching using HNO3 and H2SO4. Methods: Commercially pure titanium (grade 4) discs measuring 6 mm in diameter and 2 mm in thickness were used. The discs were divided into two groups: machined group and double acid-etched discs (HNO3 and H2SO4). Surface characteristics were assessed using Scanning Electron Microscopy. Pre-osteoblastic MC3T3-E1 cells were used for cell culture on the tested surfaces to assess proliferation, viability (MTT), as well as secretion (ELISA) and cytoplasmic expression (Western blot) of type I collagen. Results: The data obtained were analyzed using t-test or two-way ANOVA followed by Bonferroni’s test at 95% significance. The titanium surfaces showed average roughness values for the machined and treated surfaces of 0.29 and 1.16, respectively (p&lt;0.05). An increase in cell proliferation was observed, which was corroborated by the viability assay. Both type I collagen secretion and intracellular expression were higher on the double acid-etched surface compared to the machine surfaces (p&lt;0.05). Conclusion: Implant surfaces treated by double acid etching positively affected the early events of the interaction between titanium and osteoblastic cells, suggesting optimization of osseintegration.

Anodization as a promising surface treatment for drug delivery implants and a non-cytotoxic process for surface alteration: a pilot study.

Aim Surface treatments use industrial processes in which surface contamination can occur. In this context, this study aimed to demonstrate a surface treatment process, from laboratory samples and clinical implants, named anodizing, analyze their tendencies to surface contamination as well as their properties.Materials and Methods Laboratorial samples of pure titanium were anodized. Investigated by scanning microscopy (SEM), dispersive energy spectroscopy (EDS) and wettability tests. Four implant systems available in the current market were chosen by different surface treatments (anodizing, double acid etching and particle blasting) and investigated by SEM/EDS.Results Laboratory samples showed a nanomorphology surface, free of contaminants and good liquid/surface interaction. The implant system with anodization treatment did not present elements outside the standards. However, the implants treated with acid attack and blasting were found different chemical elements like aluminum and magnesium.Conclusions Anodizing proved to be a contaminant-free surface treatment both in the laboratory and clinical implants. In addition, its promising property of owning TiO2 nanotubes suggests an inherent evolution to biomedical implants for drug delivery systems other than all surface treatments developed to date.

Influence of Titanium Oxide Pillar Array Nanometric Structures and Ultraviolet Irradiation on the Properties of the Surface of Dental Implants-A Pilot Study.

Aim: Titanium implants are commonly used as replacement therapy for lost teeth and much current research is focusing on the improvement of the chemical and physical properties of their surfaces in order to improve the osseointegration process. TiO2, when it is deposited in the form of pillar array nanometric structures, has photocatalytic properties and wet surface control, which, together with UV irradiation, provide it with superhydrophilic surfaces, which may be of interest for improving cell adhesion on the peri-implant surface. In this article, we address the influence of this type of surface treatment on type IV and type V titanium discs on their surface energy and cell growth on them. Materials and methods: Samples from titanium rods used for making dental implants were used. There were two types of samples: grade IV and grade V. In turn, within each grade, two types of samples were differentiated: untreated and treated with sand blasting and subjected to double acid etching. Synthesis of the film consisting of titanium oxide pillar array structures was carried out using plasma-enhanced chemical vapor deposition equipment. The plasma was generated in a quartz vessel by an external SLAN-1 microwave source with a frequency of 2.45 GHz. Five specimens from each group were used (40 discs in total). On the surfaces to be studied, the following determinations were carried out: (a) X-ray photoelectron spectroscopy, (b) scanning electron microscopy, (c) energy dispersive X-ray spectroscopy, (d) profilometry, (e) contact angle measurement or surface wettability, (f) progression of contact angle on applying ultraviolet irradiation, and (g) a biocompatibility test and cytotoxicity with cell cultures. Results: The application of ultraviolet light decreased the hydrophobicity of all the surfaces studied, although it did so to a greater extent on the surfaces with the studied modification applied, this being more evident in samples manufactured in grade V titanium. In samples made in grade IV titanium, this difference was less evident, and even in the sample manufactured with grade IV and SLA treatment, the application of the nanometric modification of the surface made the surface optically less active. Regarding cell growth, all the surfaces studied, grouped in relation to the presence or not of the nanometric treatment, showed similar growth. Conclusions. Treatment of titanium oxide surfaces with ultraviolet irradiation made them change temporarily into superhydrophilic ones, which confirms that their biocompatibility could be improved in this way, or at least be maintained.

Microtomographic evaluation of a nanometric implant surface associated to L‐PRF: Study in osteoporotic rats

Background Osteoporosis is associated to decrease of bone mineral density, leading to an increase of skeletal frailty and fracture risk. Surface characteristics of dental implants may influence bone response, modulating cell proliferation and differentiation. Nanostructures applied to biomaterials may contribute to a higher bone to implant contact. Previous studies have shown that Leukocyte platelet rich fibrin (L-PRF) can increase the amount and formation rate of new bone around implants. Aim/Hypothesis To micro-tomographically evaluate, in osteoporotic rats, the bone repair around two implant surfaces, associated of not to L-PRF, analyzing Bone to Implant Contact (IS TS,%), Bone Volume Fraction (BV TV,%), Bone Surface Volume (BS BV,%) Trabecular Thickness (Tb.Th,mm), and Total Porosity (To.Po,%). Materials and Methods Mini implants with 2 types of surface (double acid etched=DAE, or with the addition of nano-hydroxyapatite = NHA + 24 implants of each type) were installed in the tibias of osteoporotic rats. In 24 rats, L-PRF was obtained with blood collection by means of cardiac puncture and posterior centrifugation, and inserted in the prepared bone site before implant insertion. The 48 rats were randomly divided into 4 experimental groups of 12 rats each- G1- DAE implants installed+ G2- NHA implants installed+ G3- DAE implants installed in association to L-PRF+ G4- NHA implants installed in association to L-PRF. All the mini implants were prepared for the study, measured 2.7 mm in length x 1.4 mm in diameter, and had the same macrostructure. The animals were euthanized 7 and 30 days (7d and 30d) after implants placement (6 from each group period). The tibias were removed for microtomographic evaluation of the bone between the threads of the implants, analyzing the previously described parameters. Results Inter-groups differences were assessed using One-way Analysis of Variance (P < 0.05 was considered). For IS TS, statistically significant differences were found in L-PRF treated rats between DAE (45.31 ± 5.06) versus NHA (52.81 ± 4.43) implants. For BV TV, there were statistically significant differences between G3 7d (44.08 ± 6.98) versus G4 7d (58.95 ± 5.53) and between G3 30d (54.33 ± 4.18) versus G4 30d (68.09 ± 6.56) + for the NHA surface, there were also statistical differences between rats without (49.57 ± 4.94) or with (63.52 ± 5.09) L-PRF treatment association. The results of BS BV showed statistically significant differences between DAE (36.71 ± 3.31) and NHA (32.13 ± 2.95) implant surfaces in L-PRF treated animals. For Tb.Th, there were statistically significant differences between G3 30d (0.093 ± 0.010) versus G4 30d (0.115 ± 0.012). For To.Po, statistically significant differences were found in L-PRF treated rats between DAE (53.69 ± 5.80) versus NHA (45.25 ± 4.98) implants. Conclusion and Clinical Implications Microtomographic analysis showed that the nano-hydroxyapatite implant surface presented more tridimensional bone to implant contact, bone volume fraction and trabecular thickness, and also less bone surface volume and porosity, when compared to DAE surface. Furthermore, the NHA surface was the most benefited by the association to L-PRF treatment. These results suggest that this treatment protocol (NHA + L-PRF) should be tested in humans, in trials evaluating challenging clinical situations.

Wettability and adhesion of nanotubes applied to the surface of titanium implants by anodic oxidation

Background: A good implant surface is crucial for osseointegration. Many types are described in literature like double acid etching, SLA and anodization.

An Evaluation of Er:YAG Laser in an Intact Enamel Treatment on Bonding to the Resin Cement Compared to Four Traditional Techniques

Evaluation of the bond strength of the resin cement after enamel conditioning with erbium-doped yttrium aluminum garnet laser compared to other four different techniques. The study consisted of 50 enamel specimens excluded from the smooth surfaces of newly extracted human 3rd molars. The specimens were randomly divided into five groups in terms of the enamel treatment technique. Each group (n = 10) was conditioned differently by bevel and acid etching group (I), acid etching technique group (II), double acid etching technique group (III), air abrasion followed by acid etching group (IV), and Er:YAG laser followed by acid etching group (V). After enamel treatment, a resin cylinder was installed using split Teflon matrix on each enamel specimen. Then the specimens were exposed to a shear strength device, and shear force was applied. The results were recorded with Newton. The required data were collected and statistically analyzed. A one-way ANOVA test was conducted to compare the five study groups using SPSS version 21 (p < 0.05). All groups showed high shear bond strength values ranging from 19.26 MPa (for group III) to 27.05 MPa (for group V). The enamel treatment with Er:YAG laser followed by acid etching gave the best results with significant differences compared to the other groups. Within the limitations of the present study, it can be concluded that the combination between the Er:YAG laser and the acid etching enhances the bond strength of resin cement with the enamel. The use of Er:YAG laser followed by acid etching can be a successful technique for enamel conditioning and the results showed their superiority over the other groups.

Effect of Different Morphology of Titanium Surface on the Bone Healing in Defects Filled Only with Blood Clot: A New Animal Study Design.

Background The objective of the present histologic animal study was to analyze whether roughness of the titanium surface can influence and/or stimulate the bone growth in defects filled with the blood using a rabbit tibia model. Materials and Methods Forty sets (implant and abutment), dental implant (3.5 mm in diameter and 7 mm in length) plus healing abutment (2.5 mm in diameter), were inserted in the tibiae of 10 rabbits. Moreover, twenty titanium discs were prepared. The abutment and discs were treated by 4 different methods and divided into 4 groups: (group A) machined abutments (smooth); (group B) double acid etching treatment; (group C) treatment with blasting with particles of aluminum oxide blasted plus acid conditioning; (group D) treatment with thorough blasting with particles of titanium oxide plus acid conditioning. The discs were used to characterize the surfaces by a profilometer and scanning electronic microscopy. Results After 8 weeks, the new bone formation around the sets of the samples was analyzed qualitatively and quantitatively in relation to bone height from the base of the implant and presence of osteocytes. Group C (1.50±0.20 mm) and group D (1.62±0.18 mm) showed bone growth on the abutment with higher values compared to group A (0.94±0.30 mm) and group B (1.19±0.23 mm), with significant difference between the groups (P < 0.05). In addition, osteocyte presence was higher in groups with surface treatment related to machined (P < 0.05). Conclusions Within the limitations of the present study, it was possible to observe that there is a direct relationship between the roughness present on the titanium surface and the stimulus for bone formation, since the presence of larger amounts of osteocytes on SLA surfaces evidenced this fact. Furthermore, the increased formation of bone tissue in height demonstrates that there is an important difference between the physical and chemical methods used for surface treatment.

Refined isolation techniques for GaN-based high electron mobility transistors

This work investigates the Ar+/N+ based ion implantation and Ar based reactive ion etching (RIE) techniques for device isolation. A comparison of ion implantation technique with three ion energies (20/35/65 keV) and 4 energies (20/35/65/160 keV) of Ar+ and N+ with different ion doses for isolation was reported. Use of 4 energy ion implantation provided better isolation. Ar based single and dual step reactive ion etching process was also explored for the mesa isolation of GaN HEMTs. The etch rate increases (44.7%) significantly after mixing of Ar gas directly with BCl3: Cl2 combination. Hence, the Ar addition in the single step etching proved to be more beneficial as compared to the double step etching technique.

Characterization of chemically treated Ti-Zr system alloys for dental implant application

Materials and surfaces developed for dental implants need to withstand degradation processes that take place in the oral cavity. Therefore, the aim of the study was to develop and evaluate the topographical, mechanical, chemical, electrochemical and biological properties of Ti-xZr alloys (x = 5, 10, and 15 wt%) with two surface features (machined and double acid etched). Commercially pure titanium (cpTi) and Ti-6Al-4V alloy were used as controls. Surface characterization was performed using dispersive energy spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy, profilometry and surface energy. The mechanical properties were assessed using Vickers microhardness, elastic modulus and stiffness. The electrochemical behavior analysis was conducted in a body fluid solution (pH 7.4). In addition, MC3T3-E1 cells were used to determine the impact of material and surface treatment on cell morphology by SEM analysis. Data were analyzed by two-way ANOVA and Bonferroni test (α = 0.05). Ti-Zr alloys showed lower surface roughness, elastic modulus and stiffness, as well as higher hardness and surface energy when compared to cpTi. Ti-Zr system increased the polarization resistance values and significantly decreased the capacitance, corrosion current density (icorr), and passivation current density (ipass) values. The acid treatment increased the resistance and corrosion potential of the oxide layer. SEM data analysis demonstrated that Ti-Zr alloys displayed normal cell attachment/spreading and slightly changed cell morphology in the double etched surface. In conclusion, Zr addition and surface treatment altered surface, mechanical, biological and electrochemical properties of Ti material.

Plasma Etch Variation Control in Double Patterning Based Metal Hard Mask Open Process

At Cu/low-K interconnection based BEOL etch technology with double patterning scheme, metal hard mask (MHM) etch process is the key step to define final physical structure of Cu line. Gap fill and reliability performance are highly related with MHM pattern CD and profile. During double patterning-based MHM etch process, tri-layers (including organic and inorganic nonmetallic materials) and HM film (e.g. TiN metalloid material) etch processes are involved. Precondition, by-product and etch stop layers are different for each etch flow in double patterning-based MHM open process, which could easily induce final CD variation in first wafer and both trench patterns. First wafer effect with large CD variation in MHM etch process could induce interconnection fail and poor WAT/RE property. In this paper, we investigate double patterning-based MHM etch performance with different etch flow and wafer-less auto clean (WAC)/season process from the viewpoints of CD variation control. Variation control method and mechanism for double patterning-based MHM etch process are also addressed.

Evaluation of a Titanium Surface Treated with Hydroxyapatite Nanocrystals on Osteoblastic Cell Behavior: An In Vitro Study.

In the context of macrostructural and microstructural modifications to the design of dental implants, surface topography changes with different treatments have the purpose of accelerating bone formation. The aim of this study was to evaluate in vitro the influence of aggregated hydroxyapatite nanocrystals to surfaces treated with double acid etching (Nano) on osteoblastic cell behavior compared with a conventional double acid-etched surface (DE). Commercially pure Grade 4 titanium discs (6 × 2 mm) were selected, and both cell proliferation and viability were assessed at 24, 48, and 72 hours using Trypan blue vital dye and MTT, respectively. The expression of type I collagen and osteopontin on such surfaces was evaluated using ELISA. Immunostaining for fibronectin was also performed. Quantitative data were analyzed statistically using two-way analysis of variance (ANOVA) followed by Bonferroni post-test with a 5% significance level. The results showed that in all evaluated time periods, cells expressed fibronectin on both surfaces. The cells presented greater morphologic spreading on the Nano surface when compared with the conventional DE surface in all assessed times. Increased cell proliferation and viability were detected in the Nano surface (P < .05) when compared with the conventional DE surface, especially after 72 hours. Osteopontin expression was higher after 24 hours in the Nano surface when compared with the conventional DE surface (P < .05). For type I collagen, a higher expression was observed with the Nano surface than with the DE surface, again after 72 hours (P < .05). This in vitro study showed that the treated Nano surface tested promoted increased cell proliferation and viability when compared with the control surface. Additionally, increased cell spreading as well as type I collagen and osteopontin secretion were observed, favoring the early events of osseointegration.

Double acid etching treatment of dental implants for enhanced biological properties.

The topographical features on the surface of dental implants have been considered as a critical parameter for enhancing the osseointegration of implants. In this work, we proposed a surface obtained by a combination of shot blasting and double acid etching. The double acid etching was hypothesized to increase the submicron topography and hence further stimulate the biological properties of the titanium implant. The topographical features (surface roughness and real surface area), wettability and surface chemical composition were analyzed. The results showed that the proposed method produced a dual roughness, mainly composed of randomly distributed peaks and valleys with a superimposed nanoroughness, and hence with an increased specific surface area. Despite the fact that the proposed method does not introduce significant chemical changes, this treatment combination slightly increased the amount of titanium available on the surface, reducing potential surface contaminants. Furthermore, the surface showed increased contact angle values demonstrating an enhanced hydrophobicity on the surface. The biological behavior of the implants was then assessed by culturing osteoblast-like cells on the surface, showing enhanced osteoblast adhesion, proliferation and differentiation on the novel surface. Based on these results, the described surface with dual roughness obtained by double acid etching may be a novel route to obtain key features on the surface to enhance the osseointegration of the implant. Our approach is a simple method to obtain a dual roughness that mimics the bone structure modified by osteoclasts and increases surface area, which enhances osseointegration of dental implants.

Minimizing cross-axis sensitivity in grating-based optomechanical accelerometers.

Cross-axis sensitivity of single-axis optomechanical accelerometers, mainly caused by the asymmetric structural design, is an essential issue primarily for high performance applications, which has not been systematically researched. This paper investigates the generating mechanism and detrimental effects of the cross-axis sensitivity of a high resoluion single-axis optomechanical accelerometer, which is composed of a grating-based cavity and an acceleration sensing chip consisting of four crab-shaped cantilevers and a proof mass. The modified design has been proposed and a prototype setup has been built based on the model of cross-axis sensitivity in optomechanical accelerometers. The characterization of the cross-axis sensitivity of a specific optomechanical accelerometer is quantitatively discussed for both mechanical and optical components by numerical simulation and theoretical analysis in this work. The analysis indicates that the cross-axis sensitivity decreases the contrast ratio of the interference signal and the acceleration sensitivity, as well as giving rise to an additional optical path difference, which would impact the accuracy of the accelerometer. The improved mechanical design is achieved by double side etching on a specific double-substrate-layer silicon-on-insulator (SOI) wafer to move the center of the proof mass to the support plane. The experimental results demonstrate that the modified design with highly symmetrical structure can suppress the cross-axis sensitivity significantly without compromising the sensitivity and resolution. The cross-axis sensitivity defined by the contrast ratio of the output signal drops to 2.19% /0.1g from 28.28%/0.1g under the premise that the acceleration sensitivity of this single-axis optomechanical accelerometer remains 1162.45V/g and the resolution remains 1.325μg.