Mean Roughness Values Research Articles

Analysis of Biofilm Adhesion on CAD/CAM Lithium Disilicates Under Different Types of Intraoral Polishing.

To evaluate the adhesion of Streptococcus mutans (S. mutans) on lithium disilicate ceramics, submitted to different intraoral polishing protocols, and the degree of surface smoothness obtained. Fifty lithium disilicate specimens were divided into 5 groups (n=10): G1-Glaze Group (positive control); G2-Glaze Group + Wear + Glaze; G3-Wear Group (negative control); G4-Ceramisté Wear Group; G5-Optrafine Wear Group. Surface roughness (Ra - μm) was evaluated and the surface characteristics were assessed using a scanning electron microscope (SEM); to assess S. mutans biofilm, the number of cultured cells was evaluated by counting colony-forming units (CFU/mL). The data underwent one-way ANOVA followed by Tukey's test (P⟨.05). There was a significant difference in the surface roughness of all groups compared with G3. There was no significant difference between the G4 and G5 groups that received polishing. G1 group had the lowest mean roughness values. There was a difference in Log values (CFU/mL) between the G3 group and the groups that received glaze (G1 and G2). The G3 group had the highest adhesion of S. mutans (4.53 Log). The most effective polishing protocol after wear is glazing, presenting the lowest roughness and CFU/mL values.

INFLUENCE OF SURFACE ROUGHNESS ON THE DYNAMIC STALL OF A ROTARY WING SECTION IN SUBSONIC FLOW

Wear involves the losses of some material from the surface and leads to the surface roughness. In the present work, the influence of surface roughness on the dynamic stall of a rotary wing section in subsonic flow has been investigated with different degree of surface roughness. The airfoil surface roughness was estimated using arithmetic mean roughness value (ISO-4287/1). For this purpose an indicial response method for unsteady, two dimensional flow is used to calculating the unsteady lift and pitching moment of NACA 0012 airfoil undergoing a pitching oscillation in the deep dynamic stall regime. Using the ANSYS-5.8 software as a source for the preliminary static data that required by the indicial method. The investigation is done through a number of test cases with different mean angles of attack, amplitude and reduced frequencies for airfoil oscillating around its quarter chord axis. The results include the time dependent behaviour and hysteresis loops of the lift and pitching moment for the airfoil with different degree of surface roughness. For rough airfoil an aerodynamic characteristic showed a reduction in the lift coefficient, separation point moved forward to the leading edge, the boundary layer reattachment take place at smaller angle of attack, the stall angle decrease and the pitching moment coefficient decrease as compared with smoother airfoil. So the periodic test must be done and re-coating the rotary wing if the surface roughness increased.

Experimental Investigation of Surface Roughness in Milling of DuralcanTM Composite.

In today’s developing aircraft and automotive industry, extremely durable and wear-resistant materials, especially in high temperatures, are applied. Due to this practical approach, conventional materials have been superseded by composite materials. In recent years, the application of metal matrix composites has become evident in industry 4.0. A study has been performed to analyze the surface roughness of aluminum matrix composites named Duralcan® during end milling. Two roughness surface parameters have been selected: arithmetical mean roughness value Ra and mean roughness depth Rz regarding the variable cutting speed. Due to the classification of aluminum matrix composites as hard-to-cut materials concerning excessive tool wear, this paper describes the possibility of surface roughness prediction using machine learning algorithms. In order to find the best algorithm, Classification and Regression Tree (CART) and pattern recognition models based on artificial neural networks (ANN) have been compared. By following the obtained models, the experiment shows the effectiveness of roughness prediction based on verification models. Based on experimental research, the authors obtained the coefficient R2 for the CART model 0.91 and the mean square error for the model ANN 0.11.

Fractal analysis of the martian landscape: A study of kilometre-scale topographic roughness

Natural and engineered surfaces can be modelled as fractal objects described by a non-integer dimension (i.e., their fractal dimension). This approach has been used extensively to characterize surface complexity in terms of rugosity or roughness. In this paper, the local fractal dimension is proposed as a means of mapping the spatial variability of the surface roughness of the Martian landscape. The local fractal dimension complements measures of topographic roughness proposed by other authors and provides new images of the Martian surface texture at the kilometric scale that can be used to interpret geological events, geological processes and geological formations. It can also assist in geological mapping and in the detection and prioritisation of sites that merit further exploration. Mars Orbiter Laser Altimeter data were used to characterize the kilometre-scale terrain roughness of Mars. The procedure is general and can also be applied to digital elevation models with higher resolution (for example, digital elevation models generated by stereo-pair HiRISE images) to assess roughness at the metric scale. Sixteen test sites were selected and used to illustrate the patterns of the spatial variability of landscape roughness (local fractal dimension maps) at the kilometric scale. The results show that the mean of the local fractal dimension ranges from 2.036 in Argyre Planitia to 2.403 at the North Pole. The results also show that the mean roughness values of the Martian landscapes are less than those of the Earth's continents. Basically, the roughness of the Martian terrain at the kilometric scale depends, inter alia, on the number of kilometric-scale landforms present on the terrain. It is thus logical that the local fractal dimension is higher on Earth, a geologically active planet, than on Mars. Only the North Pole test site (an area larger than the North polar ice cap) shows a roughness histogram similar to those of terrestrial sites. The abundance of information embedded in the spatial variability patterns in the roughness maps provides a significant resource for planetary geology research.

Analysis of AM Parameters on Surface Roughness Obtained in PLA Parts Printed with FFF Technology.

Fused filament fabrication (FFF) 3D printing technology allows very complex parts to be obtained at a relatively low cost and in reduced manufacturing times. In the present work, the effect of main 3D printing parameters on roughness obtained in curved surfaces is addressed. Polylactic acid (PLA) hemispherical cups were printed with a shape similar to that of the acetabular part of the hip prostheses. Different experiments were performed according to a factorial design of experiments, with nozzle diameter, temperature, layer height, print speed and extrusion multiplier as variables. Different roughness parameters were measured—Ra, Rz, Rku, Rsk—both on the outer surface and on the inner surface of the parts. Arithmetical mean roughness value Ra and greatest height of the roughness profile Rz are usually employed to compare the surface finish among different manufacturing processes. However, they do not provide information about the shape of the roughness profile. For this purpose, in the present work kurtosis Rku and skewness Rsk were used. If the height distribution in a roughness profile follows a normal law, the Rku parameter will take a value of 3. If the profile distribution is symmetrical, the Rsk parameter will take a value of 0. Adaptive neural fuzzy inference system (ANFIS) models were obtained for each response. Such models are often employed to model different manufacturing processes, but their use has not yet been extended to 3D printing processes. All roughness parameters studied depended mainly on layer height, followed by nozzle diameter. In the present work, as a general trend, Rsk was close to but lower than 0, while Rku was slightly lower than 3. This corresponds to slightly higher valleys than peaks, with a rounded height distribution to some degree.

Grinding efficiency and profile accuracy of diamond grinding wheels dressed with wire electrical discharge conditioning (WEDC)

Super abrasive diamond grinding wheels are the most promising tools for the precision machining of advanced ceramics and carbide materials. However, the efficiency of conventional conditioning of these tools is limited owing to high dressing tool wear, long process time, low form flexibility, and induced damage to the abrasive grains. Wire electrical discharge machining (WEDM) is an alternative method for conditioning of superabrasive grinding wheels with electrically conductive bonding materials. In this study, cylindrical plunge grinding of an alumina ceramic with a resin-bonded diamond grinding wheel is investigated. The assigned type of resin bond contains copper particles and is accordingly electrically conductive for wire electrical discharge conditioning (WEDC). Conventional (mechanical) and WEDC methods are used for generating the same profile on two similar diamond grinding wheels. As a result, the specific grinding energy was reduced up to 26% and 29% during rough and finish plunge grinding, respectively. Reduced specific grinding energy and forces, along with more effective grain protrusion and sharpness by using WEDC for profiling of grinding wheels, have contributed positively to the ground surface conditions despite the relatively rougher wheel surface topography in comparison to the conventional profiling. The more considerable reduction in the mean roughness depth (Rz) than in the arithmetical mean roughness value (Ra) (11% smaller Rz values in WEDC versus mechanical conditioning) verifies that the workpiece surface underwent less surface degradation in case of WEDC because of smaller grinding forces. Furthermore, the profile wear behavior of the workpiece ground with the WED conditioned grinding wheel was superior to the conventionally conditioned one.

Alcohol and light-polymerizing glaze effect on the physical and mechanical properties of a bisacrylate composite resin before and after immersion in chlorhexidine gluconate

Statement of problemThe use of 0.12% chlorhexidine gluconate (CHX) may damage bisacrylate composite resin interim restorations, but whether they can be protected with an application of alcohol and/or the use of a glaze is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of applying a 70% alcohol solution on the physical and mechanical properties of a bisacrylate composite resin, with and without the application of a light-polymerizing glaze subjected to 0.12% CHX twice a day for 7 days. Material and methodsForty specimens of an autopolymerized bisacrylate composite resin were divided into 4 groups (n=10): Group C (without alcohol, without glaze), Group G (without alcohol, with glaze), Group A (with alcohol, without glaze), and Group AG (with alcohol, with glaze). All specimens were submitted to in vitro treatment with 0.12% CHX for 7 days, and tests of color alteration (ΔE00), microhardness, roughness, and surface were performed initially and after treatment. Data were submitted to analysis of variance (ANOVA) and the Tukey HSD test (α=.05). ResultsGroup A had the lowest mean value of ΔE00 with a significant statistical difference from Group C. The groups with alcohol presented higher microhardness mean values compared with groups without alcohol in both periods of analysis, except for the groups with glaze in the final period. Group C showed higher mean roughness values in comparison with Group A in both periods. Group AG presented higher mean roughness values than Group G. Surface energy values did not vary significantly among groups, except between Groups C and A in the final period. ConclusionsThe application of alcohol optimized the properties of the autopolymerized bisacrylate composite resin analyzed, with and without the application of glaze. Overall, the use of CHX changed the microhardness and roughness when the glaze was applied.

Topographic characterization of cp-Ti implants with machined and modified surface by LASER

This study characterized the topography osseointegrated implants (cp-Ti) with machined surface (MS), laser beam surface (LS) and laser beam surface followed by deposition of sodium silicate (SS) by means SEM-EDX, roughness measurements, cross-sectional roughness, contact angle, X-ray diffraction (XRD) and laser confocal optical perfilometry. The SEM of MS showed smooth surface, contaminated with machining residues, while LS and SS rough surfaces with a more regular and homogeneous morphological pattern. The EDX showed Ti peaks for MS and Ti and oxygen for LS and SS. The mean roughness values of LS and SS were statistically higher (p <0.05) than MS. The contact angle of LS and SS was 0º. The XRD of MS showed only Ti peaks, while LS and SS showed the presence of oxides and nitrides and presence of sodium silicate. The surface treatment performed in the LS and SS promoted important modifications in the topography and physical-chemical properties.

Effect of silica coating and laser treatment on the flexural strength, surface characteristics, and bond strength of a dental zirconia.

This study investigated the effect of irradiation with an erbium-doped yttrium aluminium garnet (Er:YAG) laser and coating with silica on the surface characteristics, bond strength, and flexural strength of dental zirconia. Three hundred and forty-three standard zirconia specimens were created, and 49 were assigned to each of seven surface treatment groups: (i) no treatment; Er:YAG laser (80mJ/2Hz) with pulse widths of 50μs (ii), 100μs (iii), 300μs (iv), or 600μs (v); or tribochemical silica coating at the partially sintered stage (vi) or after sintering was complete (vii). All specimens were sintered after the surface treatments, except for the group in which specimens were sintered before treatment. The study outcomes were roughness, surface loss, microshear bond strength (μSBS), and biaxial flexural strength (BFS). Mean roughness and surface loss values were significantly higher in specimens from irradiated groups than in those from silica-coated groups. Regarding μSBS, after aging, specimens from all experimental groups presented very low and similar μSBS values, irrespective of the surface treatment. Silica coating after sintering yielded the highest BFS (1149.5 ± 167.6MPa), while coating partially sintered specimens with silica resulted a BFS (826.9±60.9MPa) similar to that of the untreated control group (794.9±101.7MPa). Laser treatments, irrespective of pulse width used, significantly decreased the BFS. In the group treated with laser at 300μs pulse width, specimens exhibited the lowest BFS value (514.1±71.5MPa). Adhesion to zirconia was not stable after aging, regardless of the surface treatment implemented.

Comparison of the optical and morphological properties of CdO thin films obtained by different methods

In the present work, transparent cadmium oxide (CdO) thin films prepared by using different methods (spray pyrolysis and sol–gel techniques) on the glass substrate. Optical and morphological properties of these films were compared. For this reason, X-ray diffraction (XRD), scanning electron microscopy (SEM),atomic force microscopy(AFM) and UV–VIS spectrometry were used. TheXRDanalysis reveals that thefilmswere polycrystalline with cubicstructure. The optical band gap of the films was obtained 2.46 eV and 2.13 eV for spray pyrolysis and Sol-Gel methods, respectively. AFM micrographs is evident that the surface is highly uniform and show very low mean roughness values for the CdO surface. Surface roughness values were calculated 39.1 nm and 64.9 nm for spray pyrolysis and sol–gel method, respectively.

Mechanistic study to investigate the injection of surfactant assisted smart water in carbonate rocks for enhanced oil recovery: An experimental approach

More than half of the world's discovered oil is held in carbonate reservoirs, most of which are naturally oil-wet fractured reservoirs. Oil Recovery efficiency can be improved noticeably if the rock wettability is changed from an oil-wet to a water-wet state. However, what factors control the wettability alteration are not clearly specified. In this study, a comprehensive mechanistic study is performed using different experimental tools to investigate the effects of active ions, non-active ions, CTAB, and different combinations of ions and CTAB on the sample rock's wettability. The results indicate that using CTAB and a smart water solution, in which the sodium and chloride ions are eliminated and the concentration of sulfate ions is increased, (SW-0NaCl-4SO42− + 1CTAB) reduced the contact angle to 43.58°. The zeta potential value of the oil-wet calcite powder increased from −61.12 to −7.6 mV after treatment with SW-0NaCl-4SO42− + 1CTAB. Moreover, the mean roughness value of oil-wet calcite powder increased from 5.02 to 25.89 nm after treatment with SW-0NaCl-4SO42− + 1CTAB. In fact, sulfate ions are capable of removing the strongly adsorbed carboxylic groups from the surface and changing the wettability of the calcite surface to a more water-wet state. Also, the cationic surfactant monomers tend to ionically react with carboxylic groups and separate them from the calcite surface. Moreover, the removal of sodium and chloride ions also leads to significant changes in the wettability. The imbibition results showed that the change of wettability from an oil-wet to a more water-wet state results in a critical increase in oil recovery efficiency during imbibition of distilled water into the calcite rock slice. High oil recovery efficiency can be obtained by optimizing the smart water solution composition and using a proper concentration of surfactant.

Rain droplet erosion behavior of a thermoplastic based leading edge protection system for wind turbine blades

This paper discusses the rain droplet erosion mechanisms of an acrylonitrile butadiene styrene (ABS). Rain droplet impingement was modeled based on a coupled smoothed particle hydrodynamics and finite element method (SPH/FEM). Using linear elastic material parameters at low strain rates, the dynamic stress behavior was studied and the location of damage initiation was predicted. Experiments using a pulsating jet erosion tester were performed and the resulting erosion behavior was analyzed using confocal microscopy. The damage was expected to initiate at the surface and remain superficial during propagation. It was shown that a pitting behavior occurred at the surface after the first few impacts. This pitting continued until 100.000 impacts. After this, the pits connected through a cracking mechanism and finally, at 300.000 impacts, cratering was observed which led to the onset of material loss. The depth of these craters was observed to be approximately 80µm, which was relatively low as compared to the material thickness of 4mm, indicating superficial damage. The resulting volume loss curve showed an initial period where no volume loss occurred, called the incubation period, followed by a linear relation between the volume loss and the number of impacts. This behavior agreed well with behavior found for other materials in literature. The surface roughness parameters were determined for each amount of impacts and the mean roughness value corresponded well to the volume loss behavior. Earlier stages of damage could be detected by analyzing the skewness value.

Measurement of surface roughness of the stone cast poured on different impression materials

The aim of this study was to determine the mean roughness values of the stone casts Surfaces that were poured from two different gypsum products (ZETA and QD) dental stones on the three different impression materials (Supersil,Neogenate and Xanthano). Ten patients were selected to perform this study, for each patient six impressions were recorded. Sixty stone casts were poured and examined to evaluate surface roughness values. The stone casts were tested for surface roughness values with surface-roughness-measuring instrument,Profilometer(Perthometer). The data were statistically analyzed using ANOVA and Duncan's multiple range test. The results of this study showed that there were a significant differences in the mean roughness values of the stone casts among the three different impression materials and two different dental stones used at alevel of (P≤0.05). It was concluded that the smoothest surface of the stone cast were obtained from poured ZETA stone on Supersil impressions, while roughness surface were observed on the stone casts produced from poured QD dental stone on Xanthano impressions.

On the machinability of the Ni-30 high-temperature iron-based superalloy

Superalloys are high-performance materials which combine high tensile, creep and fatigue strength, besides good ductility, toughness and resistance to corrosion, properties that are also responsible for their low machinability. The VAT 30® alloy contains an austenitic stainless steel base with additions of chromium, nickel, titanium and aluminum, and it is mainly applied on the manufacture of valves of combustion engines, due to its advantageous characteristics. This alloy exhibits both high ductility and abrasiveness, features that may promote both attrition and abrasion wear mechanisms on the tool used to cut it. This work contains some investigations about the effect of cooling condition, tool rake angle and cutting speed on the machinability of Ni-30 alloy in terms of cutting power consumption, surface roughness and tool life, besides the tool wear mechanisms. Conventional and high-pressure coolant injected toward the tool rake face was compared, as well as negative rake angle and neutral tooling, besides two different cutting speeds. Results show that high-pressure coolant may reduce cutting power consumption and even increase the volume of material removed during tool life up to 45% in some cases, but this same influence has not been verified regarding the workpiece arithmetical mean roughness value. Negative and neutral rake angle tools did not present very different results in terms of power and roughness, but negative tools provided considerably higher volume of material removed per tool life (up to 75% in one condition). Cutting speed showed strong effect on the cutting power, as expected, but no reasonable effect on workpiece surface roughness; regarding tool life, the cutting speed increase typically reduced the volume of material removed per tool life with conventional cooling, but when high-pressure coolant was used, this effect was attenuated. Abrasion and attrition were the main tool wear mechanisms in any tested condition.

Evaluating the Abrasivity of a Nanosized Eggshell-Titanium Dioxide on Tooth Enamel Using Atomic Force Microscopy.

Objectives This study aimed to evaluate nanosized eggshell–titanium dioxide (EB@TiO 2 ) abrasiveness in comparison with calcium carbonate and hydrated silica-containing toothpaste. Material and Methods Thirty-five bovine tooth enamels were prepared, and specimens randomly assigned to a sample group of five ( n = 7), namely, Colgate regular, Colgate pro-relief, Sensodyne rapid relief, Sensodyne repair, and EB@TiO 2 . Half of the enamel surface was brushed with each respective sample group, while the other half was covered with a tap. Statistical Analysis The mean roughness value (Ra) of the brushed and covered halves were measured using an atomic force microscope (AFM). To assess the surface morphology and changes, a scanning electron microscope (SEM) was performed. Using pair sample test and ANOVA, the Ra for the entire specimens were analyzed. A Bonferroni correction was used to identify the mean differences among the five groups (α=.05). Results The findings from this analysis show that all the tested toothpaste abraded the enamel significantly ( p < 0.05). The abrasive value contained in toothpaste comprising calcium carbonate was lower than the silica toothpaste hydrated. Conclusion Overall, Colgate regular had the lowest toothpaste abrasivity, followed by EB@TiO2, while Sensodyne rapid relief had the most enamel wear. The prominent feature of this study suggests that EB@TiO2 is suitable for oral use, as its abrasivity is comparable with calcium carbonate-containing toothpaste.

Surface Quality Evaluation of Removable Thermoplastic Dental Appliances Related to Staining Beverages and Cleaning Agents

(1) Background: Thermoplastic materials are not inert and subject to changes in the oral environment, which affect their surface quality. Color stability and topographic characteristics of clear thermoplastic appliances are critical considerations. The study aimed to evaluate the optical changes and surface topography of different thermoplastic materials related to staining beverages and cleaning agents. (2) Methods: Thermoplastic polyethylene terephthalate glycol (PET-G) material specimens were selected for the study: S (Duran, Scheu-Dental GmbH, Iserlohn, Germany), D (Biolon, Dreve Dentamid GmbH, Unna, Germany), and B (Crystal, Bio Art Dental Equipment, Sao Carlos, Brazil). Four different media were involved for immersion: coffee (C) and black tea (T) at 55 °C, Coca-Cola (K) at 5 °C, and distilled water (W) at 22 °C. As for cleaning, chemical options and mechanical brushing were selected (P-powder, T-tablets, and X-brushing). Color changes, and mean surface roughness were measured at 24 h, 48 h, and after 7 days. Statistical analysis was performed. After the testing period, atomic force microscopy (AFM) analyses and SEM images were registered in order to characterize the surface topography. (3) Results: Quantitative color change evaluations revealed a slight change in color after 24 h and an extremely marked change after 48 h, respective 7 days. Mean roughness values are kept below the clinically acceptable limit of 0.20 µm for all samples. Related to mean nanoroughness values Sa, and 3D evaluations of the surface quality, Biolon samples have demonstrated the most constant behavior, while Crystal samples are visibly influenced by water immersion. Related to the cleaning method, the topography of Duran samples was influenced by mechanical brushing. (4) Conclusions: Nanoscale investigations provided high accuracy and more realistic surface quality examinations of the examined samples compared to profilometry. Both SEM and AFM should be used for a more detailed description of the surface topography.

Characterization of Rough PTFE Surfaces by the Modified Wilhelmy Balance Technique

The wetting of rough polymer surfaces is of great importance for many technical applications. In this paper, we demonstrate the relationship between the mean roughness values and the fractal dimension of rough and self-affine PTFE surfaces. We have used white light interferometry measurements to obtain information about the complex topography of the technical surfaces having different height distributions. Two different methods for the calculation of the fractal dimension were used: The height difference correlation function (HDC) and the cube counting method. It was demonstrated that the mean roughness value (Ra) correlates better with the fractal dimension Df determined by the cube counting method than with the Df values obtained from HDC calculations. However, the HDC values show a stronger dependency by changing the surface roughness. The advancing and receding contact angles as well as the contact angle hysteresis of PTFE samples of different roughness were studied by the modified Wilhelmy balance technique using deionized water as a liquid. The modified Wilhelmy balance technique enables the possibility for future analysis of very rough PTFE surfaces which are difficult to investigate with the sessile drop method.

Effects of direct aging on near-alpha Ti–6Al–2Sn–4Zr–2Mo (Ti-6242) titanium alloy fabricated by selective laser melting (SLM)

This study reported for the first time the selective laser melting of Ti–6Al–2Sn–4Zr–2Mo (Ti-6242), a near-α titanium alloy specifically designed for high-temperature services. The microstructural stability under standard aging (595 °C/8 h) was assessed after fabrication. With increasing laser scan speeds, an increase of relative density to 99.5% was observed, followed by a dramatic decrease to around 95.7%. The arithmetic mean roughness value (Ra) evolved consistently with the density, achieving the lowest value at the laser scanning speed of 950 mm/s. The as-built sample consists mainly of martensitic α′ colonies separated by prior-β grain boundaries. Martensites partially decomposed into α laths and nano β precipitates after aging treatment, but still retained initial acicular morphologies. Despite the stress relief during aging treatment, the hardness still increased from 410 HV of the as-built sample to 450 HV. The as-built and aged Ti-6242, respectively, exhibited a maximum room-temperature tensile strength of 1437 MPa and 1510 MPa, while the ductility was reduced from 5% to 1.4%. The nanotwins within martensites contribute significantly to the relatively high ductility of the SLMed sample. The aging-induced reinforcement is mainly attributed to the precipitation hardening effects of nanosized β-phase particles.

Surface roughness alterations of zirconia implants after Er:YAG laser irradiation: a preliminary study

This study aimed to investigate the surface roughness parameters (Rp in μm) of zirconia implants (TAVDental) after erbium YAG (LiteTouchTM) laser irradiation. Implants were randomized into two groups according to the laser irradiation parameters (1.5 W/10 Hz and 1.5 W/30 Hz). The surface topography of each implant was analyzed before and after laser irradiation using laser-scanning microscopy. The roughness values from three different areas (cervical, middle, and apical) of each implant were registered. Irrespective of the different laser settings and implant surface areas, both groups showed a significant reduced mean and peak surface roughness values after laser irradiation. However, no signs of thermal defects were observed. Based on the conditions of this preliminary study, it can be concluded that the use of the Er, YAG (1.5 W, 10 and 30 Hz) is a safe tool for zirconia implant surface decontamination.

Surface free energy of 10 tropical woods species and their acrylic paint wettability

The surface free energy (SFE) of woods and their wettability are important characteristic for wood painting. No information is available regarding the SFE and wettability of Indonesian tropical woods. The purpose of the study was to determine the SFE and wettability of 10 Indonesian tropical woods. The woods tested in this study were fast-growing species from plantation of teak, sengon, jabon, pine, and species from natural forest of ramin, meranti, mahagony, camphor, keruing, and ebony. Surface roughness was measured by a profilometer, while wettability was determined by sessile drop method. The SFE values were calculated based on the Rabel method. Wettability was characterized by constant contact angle change rate (K) using the Shi and Gardner (S/G) model. The results showed that the mean roughness (Ra) value of fast-growing species from plantation was 13.58 μm and of species from natural forest was 10.73 μm. The SFE of woods varied from 36.00 mJ/m2 in the Meranti to 69.68 mJ/m2 in the Sengon. It was observed that the Meranti wood with the lowest value of SFE provided the lowest value of K (0.01) which indicated the poorest in wettability. The Sengon wood with the highest value of K (0.06) should provide the best wettability for the acrylic paint.