Effect of Surface Treatment and Cutting Orientation to the Changes in Stents Surface Roughness

The purpose of this study was to investigate the surface roughness and morphologic changes of pre-sintered ZrO 2 after sandblasting and erbium, chromium: Yttrium, scandium, gallium, garnet (Er, Cr: YSGG) laser application of different intensities. Eighty pre-sintered ZrO 2 cylinders (7 mm diameter, 3 mm height) were prepared and divided into eight groups. Specimens in the control group were not treated. The following treatments were applied: Er, Cr: YSGG laser irradiation with different energy intensities (1-6 W at 20 Hz, with air-water cooling proportion of 65%/55%) and air abrasion with Al 2 O 3 particles (120 μm). Then, all the specimens were sintered. The average surface roughness of each specimen was determined with a profilometer, and the morphology changes of a specimen from each group were evaluated with scanning electron microscope (SEM) analyses. The surface roughness data were analyzed through one-way analysis of variance and Tukey's honestly significant difference test (P < 0.05). There were significant differences between 2 and 6 W irradiations and control group. The highest surface roughness value was obtained with 6 W irradiation (8.14 ± 1.26 Ra), followed by the 5 W (7.60 ± 1.12 Ra), 4 W (7.50 ± 0.90 Ra), 3 W (5.86 ± 1.03 Ra), 2 W (4.54 ± 0.53 Ra) and sandblasting group (2.18 ± 0.92 Ra). 1 W laser irradiation (0.80 ± 0.06 Ra) presented Ra values similar to the control group (0.77 ± 0.03). The result of the statistical analyses and SEM images showed that Er, Cr: YSGG laser irradiation with 4-6 W/20 Hz presented significantly effect in surface roughness changes of zirconia than other surface treatments.

To compare the change in surface roughness of denture bases fabricated using three different techniques (additive manufacturing, subtractive manufacturing, and conventional heat-polymerizing) when immersed in two commonly available denture cleansers. One hundred and seventeen disc-shaped denture base specimens (39/group), were fabricated by subtractive manufacturing (Wieland), additive manufacturing (NextDent Denture 3D+), and conventional heat-polymerizing (Meliodent) techniques, following the manufacturers' instructions. Specimens were randomly divided into 3 groups and immersed in two effervescent denture cleansing solutions and distilled water to simulate 180 days of denture cleansing. A 3D optical noncontact surface profilometer was used to record the surface roughness of the tested denture base materials before and after immersion. Two-way ANOVA, followed by Bonferroni post hoc test, was used to assess the effects of denture cleansers on surface roughness of tested denture base resins. When immersed in Fixodent and Fittydent effervescent denture cleansing solutions, the highest change in absolute surface roughness (∆Sa, in μm) was observed in additively manufactured denture base material (0.181 ±0.018 and 0.079 ±0.008), followed by heat-polymerized denture base material (0.149 ±0.012 and 0.059 ± 0.011), while subtractively manufactured denture base material showed the least change (0.110 ±0.026 and 0.038 ±0.007), respectively. There was a difference in the extent of change in surface roughness between the denture cleansers. The change in surface roughness was much higher with the Fixodent denture cleanser as compared to the Fittydent denture cleanser. Subtractively manufactured denture base resin displayed the lowest change while additively manufactured denture base resin displayed the highest change in surface roughness in both denture cleansers, but the extent of change in surface roughness was variable.

Longevity of extrinsic stains on monolithic zirconia restorations: An in vitro study

Caries management by risk assessment (CAMBRA) and its effect on the surface roughness of various restorative materials

The response of turbulent boundary layers to sudden changes in surface roughness under adverse-pressure-gradient conditions has been studied experimentally. The roughness used was in the ‘d’ type array of Perry, Schofield &amp; Joubert (1969). Two cases of a rough-to-smooth change in surface roughness were considered in the same arbitrary adverse pressure gradient. The two cases differed in the distance of the surface discontinuity from the leading edge and gave two sets of flow conditions for the establishment and growth of the internal layer which develops downstream from a change in surface roughness. These conditions were in turn different from those in the zero-pressure-gradient experiments of Antonia &amp; Luxton. The results suggest that the growth of the new internal layer depends solely on the new conditions at the wall and scales with the local roughness length of that wall. Mean velocity profiles in the region after the step change in roughness were accurately described by Coles’ law of the wall-law of the wake combination, which contrasts with the zero-pressure-gradient results of Antonia &amp; Luxton. The skin-friction coefficient after the step change in roughness did not overshoot the equilibrium distribution but made a slow adjustment downstream of the step. Comparisons of mean profiles indicate that similar defect profile shapes are produced in layers with arbitrary adverse pressure gradients at positions where the values of Clauser's equilibrium parameter β (= δ*τ−10dp/dx) are similar, provided that the pressure-gradient history and local values of the pressure gradient are also similar.

Nanofilled composite resin is one of restorative materials with some weaknesses, such as changes of colour and surface roughness. These weaknesses are attributed to some factors, including frequent consumption some beverages, including yoghurt drinks. This study aims to determine the effect of long immersion of nanofilled composite resin in guava yogurt drink on discoloration and changes in surface roughness. Subjects of the study were nanofilled composite resin materials (3M Filtek Z350XT shade A3) in cylindrical shape with a diameter of 10 mm and 2 mm thickness. Study was conducted by immersing nanofilled resin composites in 10 mL of guava yogurt drink at 37 °C. Twelve specimens were divided into 3 groups with immersion duration of 12 hours, 24 hours, and 36 hours. Surface roughness measurements were carried out using a profilometer Starrett SR300 surface roughness tester, while the colour measurement parameters according to the system L * a * b * was measured using chromameter Konica Minolta CR-400 before and after treatment. Data of changes in surface roughness and colour changes data (ΔE) were calculated and analysed using one-way ANOVA. The results showed insignificant surface roughness changes but significant colour changes in nanofilled composite resin in the groups of 12 hours, 24 hours, and 36 hours. It is concluded that immersion duration in guava yoghurt drink significantly affects the colour of nanofilled composite resin.

The physical properties of the stent surface influence the effectiveness of vascular disease treatment after stent deployment. During the expanding process, the stent acquires high-level deformation that could alter either its microstructure or the magnitude of surface roughness. This paper constructed a finite element simulation to observe the changes in surface roughness during the stenting process. Structural transient dynamic analysis was performed using ANSYS, to identify the deformation after the stent is placed in a blood vessel. Two types of bare metal stents are studied: a Palmaz type and a Sinusoidal type. The relationship between plaque length and the changes in surface roughness was investigated by utilizing three different length of plaque; plaque length longer than the stent, shorter than the stent and the same length as the stent. In order to reduce computational time, 3D cyclical and translational symmetry was implemented into the FE model. The material models used was defined as a multilinear isotropic for stent and hyperelastic for the balloon, plaque and vessel wall. The correlation between the plastic deformation and the changes in surface roughness was obtained by intermittent pure tensile test using specimen whose chemical composition was similar to that of actual stent material. As the plastic strain is achieved from FE simulation, the surface roughness can be assessed thoroughly. The study found that the plaque size relative to stent length significantly influenced the critical changes in surface roughness. It was found that the length of stent which is equal to the plaque length was preferable due to the fact that it generated only moderate change in surface roughness. This effect was less influential to the Sinusoidal stent.

Objectives To assess the influence of cigarette smoke (CS) on the color and surface roughness of 3D printed, milled, and traditionally fabricated provisional crown and bridge (PC&B) materials. Materials and methods 112 disc-shaped samples were made employing four techniques and materials (28 per group) to fabricate PC&B prostheses. Specimens were fabricated using standard protocols, such as 3D printing, milling, conventional bis-acrylic resin, and traditional autopolymerizing polymethyl methacrylate (PMMA) resin. After preliminary color and surface roughness recording, each group specimen was divided randomly into two subgroups (14 each). The artificial saliva acted as the storage media for the control group specimens for 30 days, and test group specimens were subjected to CS in a customized smoking chamber (10 minutes twice daily, for 30 minutes). Final color and surface roughness measurements were made. The change in color (∆E00) and surface roughness (∆Sa) were calculated, and the data was tabulated for analysis. Statistical analysis One-way analysis of variance was used to analyze the change in color and surface roughness. Post-hoc Tukey HSD test was used for comparison between groups. Results The mean ΔE00 and ∆Sa were higher among groups exposed to CS than those exposed to artificial saliva. The maximum change in color was recorded in the autopolymerizing PMMA, whereas the 3D printed resins recorded the minimal change.The traditional bis-acrylic resin recorded the maximum mean surface roughness change, while the milled resin recorded the least change. Conclusions Within the study limitations, it can be inferred that when exposed to CS, 3D printed and milled PC&B materials have superior color stability and displayed less change in surface roughness when equated with traditional bis-acrylic and autopolymerizing PMMA resins.

Provisional fixed dental prosthesis (FDP) plays an important role during fixed prosthodontic therapy till the definitive. Discoloration of materials used for provisional FDPs can cause patient dissatisfaction and may create doubt about the color stability of the definitive FDP. Surface roughness is the other major property to be taken into consideration for provisional FDP materials. Smokeless tobacco is reported to affect the color stability and surface roughness of different prosthetic materials. The aim of the current study was to evaluate the effect of two types of smokeless tobacco (black and white) on color stability and surface roughness of 3D printed, CAD/CAM milled, and conventional provisional FDP resin materials. A total of 144 disc-shaped specimens were fabricated using four techniques CAD/CAM subtractive technique (milling), CAD/CAM additive technique (3D Printing), and conventional technique using autopolymerized PMMA, and autopolymerized Bis-acrylic resins. Each group was subdivided into three subgroups of twelve specimens each, and were submerged into three solutions (artificial salivary substitute, black smokeless tobacco, white smokeless tobacco). The change in color and surface roughness was evaluated and the data collected were statistically analyzed. It was observed that black smokeless tobacco caused the maximum color change and the effect was highest in autopolymerized PMMA resin specimens (ΔE = 9.343 ± 0.489), followed by 3D printed (ΔE = 7.187 ± 0.391), autopolymerized Bis-acryl (ΔE = 6.464 ± 0.453) and milled (ΔE = 4.978 ± 0.227). White smokeless tobacco was found to cause a maximum change in surface roughness and the effect was highest in autopolymerized Bis-acryl specimens (ΔRa = 0.321 ± 0.015 μm), followed by autopolymerized PMMA (ΔRa = 0.297± 0.015 μm), 3D printed (ΔRa = 0.191 ± 0.019 μm), and milled (ΔRa = 0.168 ± 0.014 μm). Statistically significant (p-value < 0.05) differences were observed among all techniques and solutions. The change in color and surface roughness were maximum in the case of FDPs prepared using autopolymerizing resins, followed by 3D printed, and CAD/CAM milled reins.

Event Abstract Back to Event Factors that affect the behavior of CoCrMo taper junctions under cyclic loading Matthew A. Di Prima1, Oleg Vesnovsky1, L D Timmie Topoleski1, 2 and Paul Kovacs3 1 FDA, CDRH/OSEL, United States 2 UMBC, Mechanical Engineering, United States 3 Consultant, Electrochemistry/Biocompatibility, United States Introduction: Artificial joints are one of the most successful treatments for arthritis; however, artificial joint failure is still a critical issue. For example, wear and corrosion at different modular junctions are thought to be instigators of artificial joint failure[1]. To achieve uniform and predictable contact between the stem and head, it is important to optimize the surface structure and properties, along with the angle mismatch, straightness, and conicity of the taper and trunnion[2],[3]. The purpose of our work was to investigate geometric parameters of four different Co-Cr taper junction designs: A, B, and C with fine-machined tapers and coarse-machined trunnions; and D with ground tapers and trunnions. Design A had a negative taper angle mismatch (taper angle > trunnion angle), while C had a positive one. B and D had no taper angle mismatch. Methods: Cyclic fatigue tests (n=3 for each design) were conducted in PBS solution at 37°C at 10Hz with a loading range from 280 N (minimum) to 2800 N (maximum). Tests were run for 10 million cycles. Displacements between the taper and trunnion were measured at each million cycles with digital extensometers during loading cycles. After 10 million cycles, the force required to separate the head and stem was measured. A head welded to a stem, preventing relative motion, was tested as a control. A composite digital image of each component was created using a Hirox digital microscope and a Bruker optical profilometer[1], through 360o over the trunnion and taper surfaces. Co and Cr ion concentrations in the test fluid were measured by ICP-MS. Results and Discussion: The changes in average surface roughness and visual appearance showed different trends and magnitudes for tapers and trunnions (Fig. 1). Changes in surface roughness should reflect assembly deformation/damage to, and in-use wear on, the machining marks, as well as metal removal by corrosion and material buildup due to corrosion product deposition. At the minimum load, all four designs showed "pistoning" while at the maximum load design A exhibited a much higher level of “rocking” relative motion (Fig. 2). The measured micromotion did not appear to reflect changes in surface roughness. The separation force was lower for design B only (Fig.3), which was the smooth taper – rough trunnion combination without any angle mismatch. The trends in Co ion concentrations and Co/Cr ratios (Fig. 3) suggest that design A exhibited the greatest overall corrosion. The change in the Co/Cr ratio is likely a change in mechanism from wear and fretting corrosion to predominantly crevice corrosion. Conclusions: A combination of experimental techniques can provide a better understanding of taper junction performance. Our results show that the geometry of the taper junction can affect wear and corrosion; however, more study is needed to assess the details of the optimum design parameters. Ideally, taper-trunnion interfaces should neither move relatively to each other while in physical contact nor undergo accelerated corrosion due to the presence of a liquid. It is essential to identify physical contact points, surface roughness changes, types of locking and loosening due to mechanical forces/damage, as well as the source(s) of soluble and insoluble corrosion products.

ABSTRACTObjective:This study aimed to evaluate the effect of various sugary drinks and a denture cleanser on the color stability and surface roughness of two tested denture teeth materials (3D printed and CAD/CAM milled).Materials and Methods:CAD/CAM additive and subtractive techniques were used to fabricate 160 custom disc-shaped specimens from two commercially available denture teeth resins. Specimens were randomly divided into 16 groups (n = 10) based on the immersion media used: a control group (artificial salivary substitute), sugary drinks groups (Pepsi, Gatorade, and ice tea), and denture cleanser groups after exposure to sugary drinks. These immersion cycles were repeated for 180 days, and the changes in color and surface roughness measurements were recorded. The data related to change in color and surface roughness was tabulated, and the statistical analysis was performed.Results:When exposed to sugary drinks, the change in color for both milled and 3D-printed materials was maximum when tested specimens were exposed to ice tea (ΔE = 3.548 and 4.055), followed by a carbonated drink (Pepsi) (ΔE = 2.334 and 3.503) and sports drink (Gatorade) (ΔE = 1.272 and 1.443), respectively. Whereas the change in surface roughness was highest after exposure to carbonated drink (ΔRa = 0.052 μm and 0.074 μm), followed by ice tea (ΔRa = 0.043 μm and 0.061 μm) and sports drink (ΔRa = 0.039 μm and 0.049 μm) for milled and 3D-printed materials, respectively.Conclusion:The 3D-printed denture tooth resins have poor color stability and are prone to more changes in surface roughness when exposed to different sugary drinks as compared to CAD/CAM milled denture teeth.

The influence of plasma nitriding and gas nitriding processes on the change of surface roughness and dimensional accuracy of 42CrMo4 steel was investigated in this paper. Both processes almost always led to changes in the surface texture. After plasma nitriding, clusters of nitride ions were formed on the surface of steel, while gas nitriding very often led to the new creation of a formation of a “plate-like” surface texture. In both cases of these processes, a compound layer in specific thickness was formed, although the parameters of the processes were chosen with the aim of suppressing it. After the optimizing of nitriding parameters during nitriding processes, it was found that there were no changes in the surface roughness evaluated using the Ra parameter. However, it turned out that when using a multi-parameter evaluation of roughness (the parameters Rz, Rsk and Rku were used), there were presented some changes in roughness due to nitriding processes, which affect the functional behavior of the components. Roughness changes were also detected by evaluating surface roughness profiles, where nitriding led to changes in peak heights and valley depths. Nitriding processes further led to changes in dimensions in the form of an increase of 0.032 mm on average. However, the magnitude of the change has some context on chemical composition of material. A larger increase in dimensions was found with gas nitriding. The change in the degree of IT accuracy is closely related to the change in dimension. For both processes, there was a change of one degree of IT accuracy compared to the ground part (from IT8 to IT9). On the basis of the achieved dimensional accuracy results, a coefficient of change in the degree of accuracy IT was created, which can be used to predict changes in the dimensional accuracy of ground surfaces after nitriding processes in degrees of accuracy IT3–IT10. In this study, a tool for predicting changes in degrees of accuracy of ground parts after nitriding processes is presented.

SummaryThe response of turbulent boundary layer to sudden change in surface roughness have been studied experimentally. Mean velocity measurements have been made in the boundary layer on a flat plate, downstream of a small step change in surface roughness under 3 different pressure gradients. The surface upstream of the step consisted of ‘k* type ‘large roughness’ wall (or ‘small roughness’ wall) and downstream of the step consisted of smooth surface (or ‘small roughness’ wall). Velocity profiles after the step change have been analysed on the basis of the two layer model. The inner region responds very quickly to the new boundary condition while the outer region takes more time to attain equilibrium or a state of local self-preservation. The skin-friction coefficient initially increased after the step change and gradually reached towards a constant value except for a particular roughness combination under adverse pressure gradient wherein the change in the roughness function is gradual over the transition.

Modification of a turbulent flow upstream of a change in surface roughness has been studied by means of a stream function-vorticity model. A flow reduction is found upstream of a step change in surface roughness when a fluid flows from a smooth onto a rough surface. Above that layer and above the region of flow reduction downstream of a smooth-rough transition, a flow acceleration is observed. Similar flow modification can be seen at a rough-smooth transition with the exception that flow reduction and flow acceleration are reversed. Within a fetch of −500 < x/z 0< + 500 (z 0 is the maximum roughness length, the roughness transition is located at x/z 0 = 0), flow reduction (flow acceleration) upstream of a roughness transition is one order of magnitude smaller than the flow reduction (flow acceleration) downstream of a smooth-rough (rough-smooth) transition. The flow acceleration (flow reduction) above that layer is two orders of magnitude. The internal boundary layer (IBL) for horizontal mean velocity extends to roughly 300z 0 upstream of a roughness transition, whereas the IBL for turbulent shear stress as well as the distortion of flow equilibrium extend almost twice as far. For the friction velocity, an undershooting (overshooting) with respect to upstream equilibrium is predicted which precedes overshooting (undershooting) over new equilibrium just behind a roughness transition. The flow modification over a finite fetch of modified roughness is weaker than over a corresponding fetch downstream of a single step change in roughness and the flow stays closer to upstream equilibrium. Even in front of the first roughness change of a finite fetch of modified roughness, a distortion of flow equilibrium due to the second, downwind roughness change can be observed.

To evaluate the effects of commonly consumed staining beverages on the color stability and surface roughness of two additively manufactured permanent resin restorative materials. Sixty disk-shaped specimens (10mm × 2mm) were fabricated from two additively manufactured resin materials (Saremco Print Crowntec and VarseoSmile Crown Plus). Specimens were finished with standardized polishing procedures and color values (CIE L*a*b*) and baseline surface roughness (Ra) were recorded. Samples were randomly assigned to three immersion media (tea, coffee, distilled water; n = 10 per subgroup) and stored at 37°C for 14 days with daily solution renewal. Color measurements were repeated after 24h and 14 days, and color differences were calculated using the CIEDE2000 formula (ΔE₀₀). Surface roughness was re-measured after 14 days. Data were analyzed using mixed-model ANOVA and correlation tests (α = 0.05). Staining solution significantly affected color change at both evaluation periods (p < 0.001), while material type had no significant influence (p > 0.05). Tea produced the highest discoloration values, followed by coffee, whereas water groups remained below acceptability thresholds. Color change increased significantly over time in tea and coffee groups. Surface roughness showed only minimal changes after immersion, with Ra values ranging from 0.438 to 0.559μm at baseline and 0.444-0.567μm after 14 days, with no significant effects of material or staining solution (p > 0.05). No significant correlation was found between baseline surface roughness and final color change (p > 0.05). A significant positive correlation was observed between the change in surface roughness (ΔRa) and color change (ΔE00) (p < 0.05). Discoloration of additively manufactured permanent resin materials was primarily influenced by exposure to staining beverages. Tea and coffee caused clinically noticeable color changes, while surface roughness showed limited changes during short-term aging. However, a significant positive correlation between surface roughness change and color change suggests that surface degradation may contribute to staining susceptibility.