Objective
This in‐vitro study measured the differences in surface roughness for computer assisted design/computer assisted manufacturing (CAD/CAM) resilient ceramic and CAD/CAM composite materials.
...Materials and Methods
The materials included Lava Ultimate (3 M), Cerasmart (GC America), Vita Enamic (Vita Zahnfabrik), and Brilliant Crios (Coltene). One calibrated operator polished each material with three polishing sytems: spiral polishers (Diacomp FeatherLite/Brasseler), rubbercup polishers (Enhance/DentsplyCaulk), and brush‐paste (Diashine/VH Technologies). Surface roughness was assessed using a confocal laser microscope (Lext OLS4000/Olympus).
Results
A two‐way ANOVA revealed statistically significant differences in mean surface roughness values (Sa) among materials and polishers. Tukey multiple comparisons showed that mean Sa values for Lava Ultimate, Enamic, Cerasmart and Brilliant Crios polished with brush‐paste as well as Lava Ultimate and Cerasmart values polished with spiral polishers were not significantly different from each other.
Conclusions
The finished surfaces were significantly smoother than milled surfaces for all materials. The brush‐paste polishing technique created the lowest surface roughness values for all CAD/CAM materials and values were comparable to what was achieved by spiral polishers for Lava Ultimate and Cerasmart. Rubber polishers did not provide a clinically smooth surface for CAD/CAM resilient ceramic/composite materials.
Clinical significance
The results of the study indicate that polishing creates smooth surfaces for CAD/CAM resilient ceramic and CAD/CAM composite restorations.
This in vitro study evaluated the surface roughness (Sa) of two high-strength silicate ceramics, lithium disilicate IPS e.max CAD, Ivoclar Vivadent (LDS group), and zirconia-reinforced lithium ...silicate Vita Suprinity, VITA Zahnfabrik (ZLS group). The surface roughness was investigated before and after milling using different polishing systems and timings relative to the final crystallization of the ceramics. Forty-eight samples per group were polished by a single calibrated operator using two polishing systems: Dialite LD (Brasseler) and Lithium Silicate Polishers (Meisinger) for the LDS group and Dialite LD (Brasseler) and Vita Suprinity Polishing Set Technical (VITA Zahnfabrik) for the ZLS group, both pre- and post-crystallization. Surface roughness was measured using a confocal laser microscope (OLS4000 LEXT/Olympus), with scanning electron microscopy (SEM) used to evaluate surface morphological changes. Significant differences in Sa values were found between baseline groups, with ZLS exhibiting lower values. All polishing methods significantly reduced surface roughness compared to baseline (p ≤ 0.05). No significant differences were found in LDS samples when polishing pre- or post-crystallization (p = 0.129), while for ZLS samples, post-crystallization polishing achieved significantly smoother surfaces (p < 0.001). The study concluded that the choice of polishing system and timing did not significantly affect surface roughness for LDS. However, it is recommended that post-crystallization polishing be performed for the optimal smoothness of ZLS. This study aimed to evaluate the post-milling polishing procedures of CAD/CAM high-strength restorations, emphasizing the importance of an optimal surface roughness to prevent issues such as increased risk of abrasion on opposing teeth, enhanced plaque adhesion, and mechanical failures. Investigating these polishing techniques enables clinicians to optimize clinical performance, thereby improving the quality and longevity of high-strength silicate ceramics.
Oxidation-reduction reactions involve electron exchanges that require optimal balance for proper cell function. This balance is measured via redox potential and reflects oxidative stress. Despite the ...critical role of oxidative stress in critical illness and injury, little is known regarding redox potential. We hypothesize redox potential measurements will correlate with accumulation of O2 debt produced by hemorrhage over time.
Ten swine were studied using a polytrauma hemorrhagic shock model. Whole blood and plasma redox potential measures were obtained at defined stages of O2 debt (20 mL/kg, 40 mL/kg, 60 mL/kg, 80 mL/kg), and through resuscitation. Redox potential was determined by measuring open circuit potential using novel gold nanoporous electrodes with Ag/AgCl reference.
Whole blood redox potential showed negative change as O2 debt accumulated, exhibiting positive response during resuscitation, and correlated with O2 debt across all animals (P < 0.001). Redox potential changes throughout O2 debt accrual were significant compared with baseline (P≤0.05), and at end resuscitation compared with O2 debt 60 mL/kg (P = 0.05) and 80 mL/kg (P = 0.02). Whole blood redox potential measures also correlated with oxygen extraction ratio, ScvO2, and lactic acid, appearing very sensitive to acute changes. Plasma redox potential showed no correlation with O2 debt.
Whole blood redox potential demonstrates significant correlation to O2 debt at all stages in this model. These results set the stage for further study of redox potential as a direct measure of oxidative stress and potential clinical tool. Given redox potential plasma performance, these measures should be made in whole blood versus plasma.
The friction and wear behavior of seven space lubricants was investigated under boundary lubrication conditions using a vacuum four-ball tribometer. Three of the lubricants were perfluo-ropolyethers ...(143AC, S-200, and Z-25). Three were synthetic hydrocarbons (a multiply alkylated cyclopentane, 2001a), and a formulated version with an antiwear and an antioxidant additive (2001). The third hydrocarbon was an unformulated polyal-phaolefin (PAO-100). An unformulated silahydrocarbon (SiHC) was also evaluated. Test conditions included: a pressure <6.7 × 10
−4
Pa, a 200N load, a sliding velocity of 28.8 mm/sec (100 rpm), and room temperature (∼23°C). The wear rate for each lubricant was determined from the slope of wear volume as a function of sliding distance. The lowest wear rate (0.033 × 10
−9
mm
3
/mm) was obtained with the silahydrocarbon. The formulated synthetic hydrocarbon had a wear rate of 0.037 × 10
−9
mm
3
/mm, which was a 36 percent reduction compared to the unformulated fluid. The polyalphaolefin had the highest wear rate of the non-PFPE fluids. Of the perfluoropolyethers (PFPEs), wear rates decreased by about 50 percent from Z-25 (1.7 × 10
−9
mm
3
/mm) to S-200 (0.70 × 10
−9
mm
3
/mm) to 143AC (0.21 × 10
−9
mm
3
/mm).
Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 26-28, 1998
Six additives were synthesized and evaluated as boundary lubrication enhancers for perfluoropolyalkylethers. These additives included a phosphate, a thiophosphate, a β-diketone, a benzothiazole, an ...amide/thiol and a sulfite. These additives were evaluated in a vacuum four-ball apparatus, at a one weight percent concentration in a perfluoropolyalkylether based on hexafluoropropene oxide. Tests were performed in vacuum (<6.7 × 10
−4
Pa), at room temperature (∼23°C), at an initial Hertzian stress of 3.5 GPa (200N load), and a sliding velocity of 28.8 mm/sec (100 rpm). Infrared (IR) and Raman spectroscopies were used to analyze the steel (AISI 52100) specimens after testing. Wear rates for each formulation were determined from the slope of wear volume as a function of sliding distance. All additives yielded reductions in mean wear rates of at least 50 percent, with the exception of the benzothiazole which had no effect. Two of the additives, an amide/thiol and a sulfite, reduced the mean wear rate by at least 80 percent. IR and Raman analysis indicated the severity of wear can be correlated to the amount of surface fluorinated polymeric acid species (R
f
COOH) and graphitic amorphous carbon, in and around the wear scar.
Presented as a Sociey of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 8-12, 1997
Pin-on-disk tribology experiments were conducted on a perfluoro-polyalkylelher (PFPE) liquid lubricant with and without a new PFPE lubricant antiwear additive material: a silane. It was found that ...the silane provided moderate improvement in the antiwear performance of the PFPE lubricant when applied to the metallic surface as a surface coating or when added to the PFPE as a dispersion (emulsion). Slightly belter results were obtained by using the combination of a surface coating and an emulsion of the silane. The silane emulsions or coalings did not affect the friction properties of the lubricant. Micro-Fourier transformation infrared (μFFIR) spectroscopy analysis was performed to study silane transfer films and the degradation of the PFPE. The silane was found to mitigate degradation of the PFPE which may have been the major reason for the improved antiwear performance, observed.
Presented at the 50th Annual Meeting in Chicago, Illinois May 14-19, 1995
The adsorption of carbon dioxide on potassium-dosed Ag(111) has been investigated with temperature-programmed desorption (TPD), work function measurements, and Auger electron (AES), X-ray ...photoelectron (XPS), and high-resolution electron energy loss (HREELS) spectroscopies. Unlike the behavior observed for other K-modified single-crystal metal surfaces, the TPD spectra of near-saturation coverages of CO sub 2 on K/Ag(111) for potassium coverages in the range 0.13 < theta sub K < 0.47, where the close-packed monolayer corresponds to theta sub K = 1/3, exhibit a sharply defined m/e = 44 peak at 796 plus/minus 6K with no evidence for the desorption of cobalt at any temperature. Similar TPD experiments involving mixtures of natural and exp 18 O-labeled CO sub 2 indicate the the O atoms undergo partial scrambling, suggesting that the overall process cannot be represented in terms of a simple adsorption/desorption of CO sub 2 . The HREELS spectra of CO sub 2 -saturated K/Ag(111) show, in addition to very minor features, a sharp peak at approx 1480 cm exp --1 , and XPS spectra of the same interface display a C(1s) peak with a binding energy characteristic of an electron-rich carbon species. This information is consistent with the presence of a C-bound CO species on the surface. Evidence against the complete dissociation of CO sub 2 was obtained from TPD, which failed to reveal features associated with carbonate (decomposition) expected to be formed via the reaction of CO sub 2 and adsorbed O. On the basis of these results, it is proposed that CO sub 2 on K/Ag(111) binds through the C to the surface, leading to the "partial" dissociation (or activation) of each Co sub 2 molecule into adsorbed CO and O. Within this model, such adsorbed O would serve as a bridge between the C atoms of neighboring "activated" CO sub 2 molecules and therefore undergo exchange prior or during thermal desorption. Adventitious water or O in the system and/or defect sites on the surface give rise to an additional m/e = 44 TPD peak at a much higher temperature. The height of this new feature is increased significantly by predosing the K/Ag(111) surface with O sub 2 or H sub 2 O at coverages as low as 0.05 L. The XPS spectra for these purposely contaminated surfaces reveal features very different from those observed in the absence of such impurities, but consistent with the presence of an ordinary form of carbonate. Ag(111) surfaces which had been damaged prior to K deposition and subsequent CO sub 2 adsorption were found to yield significant amounts of CO in the TPD spectra at lower temperatures.
PDF
