The Effects of Various Polishing Procedures on Surface Topography of CAD/CAM Resin Restoratives.

PURPOSE: To investigate the effects of different polishing procedures on surface properties of CAD/CAM resin blocks. MATERIALS AND METHODS: In this study, three different CAD/CAM restorative materials (Cerasmart, Lava Ultimate and Shofu Block HC) were used. CAD/CAM blocks were cut in 3-mm-thick slabs and divided into 5 groups. Group-1: Glaze; Group-2: Two-step Diamond Polisher; Group-3: One-step Diamond Polisher; Group-4: Three-step Diamond Polisher; Group-5: Polishing Discs+Diamond Paste. After polishing, top surfaces of the samples were prepared to screen by noncontact laser profilometer (Nanovea) for measurements. Data were analyzed using two-way analysis of variance (ANOVA). RESULTS: The arithmetical mean deviation of the profile was defined as Ra. The extension of Ra (a line's arithmetical mean height) to a surface was defined as Sa. Compared to the arithmetical mean of the surface, Sa expresses the difference in terms of each point's height as an absolute value. Sa was commonly used to assess surface roughness. The highest surface roughness (Ra) values in this study were 0.313 ± 0.05 for Cerasmart, 0.433 ± 0.10 for Lava Ultimate and 0.320 ± 0.05 for Shofu Block HC. The specimens in Group-4 displayed higher Ra values than other groups for each CAD/CAM material. According to surface topography (Sa) values, highest values were 2.936 ± 1.25 for Cerasmart, 2.633 ± 1.28 for Lava Ultimate and 3.489 ± 0.57 for Shofu Block HC. For Cerasmart, LAVA Ultimate and Shofu blocks, Group-1 exhibited significantly higher Sa values than other groups (p < 0.001). CONCLUSION: Optiglaze Color, Sof-Lex Diamond and Identoflex Diamond Ceramic Polisher create smooth CAD/CAM resin surfaces. However, surface roughness values of Cosmedent Nano/Microhybrid Diamond and Diapolisher Paste applied specimens were high. According to Sa values, highest roughness values belong to Optiglaze Color.

The effect of glazing and aging on the surface properties of CAD/CAM resin blocks.

PURPOSE: To investigate the effect of accelerated aging on surface properties of glazed CAD/CAM resin blocks using a 2D surface profilometer and a 3D non-contact optical profilometer. MATERIALS AND METHODS: Three types of CAD/CAM resin restorative materials, LAVA Ultimate (3M ESPE, St Paul, MN, USA), VITA Enamic (Vita Zahnfabrik H. Rauter, Bad Säckingen, Germany), and Cerasmart (GC Corparation, Tokyo, Japan) were used for this study. CAD/CAM blocks were cut in 3-mm thickness slabs and divided into three groups; Group 1: control group (specimens polished with 600 grit SCI paper); Group 2: specimens sandblasted, silanized, and glazed with Optiglaze Color (GC); Group 3: glazed specimens subjected to 5000 thermocycles (n=15). The surface roughness (Ra and Rz) was evaluated using a profilometer and a 3D scanning instrument. Data were analyzed using two-way ANOVA and Tukey's post-hoc test (P<.05). RESULTS: LAVA, VITA, and Cerasmart exhibited statistically similar Ra and Rz values for each group (P>.05). For VITA and Cerasmart, the specimens in Group 1 exhibited significantly higher Ra values than Group 2 (P<.05). Group 1 (0.502 Ra), Group 2 (0.384 Ra), and Group 3 (0.431 Ra) exhibited statistically similar Ra values for LAVA (P=.062). After 5000 thermocycles, surface roughness values did not change significantly for glazed LAVA, VITA, and Cerasmart (P>.05). CONCLUSION: Glaze material Optiglaze Color makes CAD/CAM resin surfaces smooth and glazed CAD/CAM surfaces seem resistant to deterioration under 5000 thermocycles.

Thermal, viscoelastic and mechanical properties' optimization of polyphenylene sulfide via optimal processing parameters using the Taguchi method.

Thermal, viscoelastic and mechanical properties of polyphenylene sulfide (PPS) were optimized as a function of extrusion and injection molding parameters. For this purpose, design of experiments approach utilizing Taguchi's L27 (37) orthogonal arrays was used. Effect of the parameters on desired properties was determined using the analysis of variance. Differential scanning calorimeter (DSC) tests were performed for the analysis of thermal properties such as melting temperature (Tm) and melting enthalpy (ΔHM). Dynamic mechanical analysis (DMA) tests were performed for the analysis of viscoelastic properties such as damping factor (tan δ) and glass transition temperature (Tg). Tensile tests were performed for the analysis of mechanical properties such as tensile strength and modulus. With optimized process parameters, verification DSC, DMA and tensile tests were performed for thermal, viscoelastic and mechanical properties, respectively. The Taguchi method showed that 'barrel temperature' and its level of '340°C' were seen to be the most effective parameter and its level; respectively. It was suggested that PPS can be reinforced for further improvement after optimized thermal, viscoelastic and mechanical properties.