Evaluation of Various Polishing Systems for Lithium Disilicate Glass-Ceramics.

OBJECTIVE: The aim of this study was to investigate the surface roughness of lithium disilicates (LS2s) polished using various polishing systems. MATERIALS AND METHODS: Two types of LS2 (A, Amber Mill and E, IPS e.max CAD) were polished using LS2-specific polishing systems (L-Edenta, L-Jota), a zirconia-specific polishing system (Z-Jota), and a conventional ceramic polishing system (P-Shofu) (n = 8 per group). The compositions of different polishing systems were analyzed using EDS. Surface roughness was measured using confocal laser scanning microscopy and analyzed using EDS and SEM. ANOVA and Tukey's tests were used for the statistical analyses (p = 0.05). RESULTS: The polishing systems were mainly composed of C, O, and Si. The L-Jota group exhibited rougher surfaces than the other groups. Amber Mill exhibited higher surface roughness than IPS e.max CAD (p⟨0.001). Among the polishing systems, the L-Jota group presented the highest roughness value (pp⟨0.001). The surface roughness of the AL-Jota group was higher than that of the other groups. CONCLUSIONS: A sufficiently smooth surface can be achieved without a LS2-specific polishing system. Further, the same polishing system can have different effects depending on the type of LS2.

An abutment screw loosening study of a Diamond Like Carbon-coated CP titanium implant.

The aim of this study was to quantify the extent of abutment screw loosening and thus understand the role of frictional and wear factors in abutment screw loosening by using a cyclic loading device to compare Diamond Like Carbon (DLC)-coated and non-coated implants. The properties of DLC films, including hardness, wear resistance, chemical stability, and biocompatibility, are similar to those of real diamond materials. In this study, a 1-mum thick DLC film served to protect and lubricate a layer of commercially-pure titanium affixed to the top of a dental implant (external hexagon-shaped implant). A cyclic loading force was then applied to the top of the prosthetic portion of the implants in order to determine the difference in looseness of the titanium abutment screw between ten DLC-coated implants and ten non-coated implants. The abutment screw loosening tests were performed with 100 N of force at a frequency of 20 Hz. Data indicate that implants with a DLC coating are more resistant to an applied force (P = 0.002) than are those without the coating. We hope these results will be useful for preventing implant abutment screw loosening.

Effect of tooth brushing and thermal cycling on a surface change of ceromers finished with different methods.

This in vitro study evaluated the effect of tooth brushing and thermal cycling on the surface lustre and surface roughness of three ceromer systems treated with different surface finishing methods. The ceromers studied were: (1). Artglass, (2). Targis, (3). Sculpture and (4). the control group, Z 100. Half of the Targis and Sculpture groups were polished and the rest were coated with staining and glazing solution, respectively. All specimens were subjected to thermocycling 10000 times. Tooth brushing abrasion tests were performed in a customized tooth-brushing machine with 500 g weight applied on a back-and-forth cycle for 20000 repetitions. The lustre determined by measuring the light reflection area and the average roughness was compared between groups and between pre- and post-test values. All materials showed a lower lustre and rougher surface after thermocycling and tooth brushing (P < 0.05). All ceromer specimens, except glazed Sculpture, showed a higher lustre and similar roughness to the control group. The post-brushing results revealed that glazed Sculpture presented discretely fallen out glaze coatings and had maximum change. However, stained Targis showed minimum change (P < 0.05) and polished Targis presented more changes than that of the staining treatment. It is therefore concluded that the glaze coatings for Sculpture don't exhibit long-term durability, while stain coatings for Targis acted like a protective layer.