Objective. This study tested whether the two-body wear of monolithic zirconia and their corresponding enamel antagonists was higher compared to monolithic alloy and veneered zirconia. Materials and methods. Cylindrical specimens (N = 36, n = 6) were prepared out of (A) veneered zirconia (VZ), (B) glazed zirconia using a glaze ceramic (GZC), (C) glazed zirconia using a glaze spray (GZS), (D) manually polished monolithic zirconia (MAZ), (E) mechanically polished monolithic zirconia (MEZ) and (F) monolithic base alloy (control group, MA). Wear tests were performed in a chewing simulator (49 N, 1.7 Hz, 5°C/50°C) with enamel antagonists. The wear analysis was performed using a 3D profilometer before and after 120,000, 240,000, 640,000 and 1,200,000 masticatory cycles. SEM images were used for evaluating wear qualitatively. The longitudinal results were analysed using linear mixed models ( = 0.05). Results. Materials (p < 0.001) and number of masticatory cycles (p < 0.001) had a significant effect on the wear level. The least enamel antagonist wear was observed for MAZ and MEZ (27.3 ± 15.2, 28 ± 11.1 m, respectively). GZC (118 ± 30.9 m) showed the highest wear of enamel antagonists. The highest wear rate in the material was observed in GZS (91.3 ± 38.6 m). While in the groups of MA, VZ, GZC and GZS 50% of the specimens developed cracks in enamel, it was 100% in MAZ and MEZ groups. Conclusion. Polished monolithic zirconia showed lower wear rate on enamel antagonists as well as within the material itself but developed higher rates of enamel cracks. AbstractObjective. This study tested whether the two-body wear of monolithic zirconia and their corresponding enamel antagonists was higher compared to monolithic alloy and veneered zirconia. Material and methods. Cylindrical specimens (N=36, n=6) were prepared out of A) veneered zirconia (VZ), B) glazed zirconia using a glaze ceramic (GZC), C) glazed zirconia using a glaze spray (GZS), D) manually polished monolithic zirconia (MAZ), E) mechanically polished monolithic zirconia (MEZ) and F) monolithic base alloy (control group, MA). Wear tests were performed in a chewing simulator (49N, 1.7 Hz, 5°C/50°C) with enamel antagonists. The wear analysis was performed using a 3D profilometer before and after 120.000, 240.000, 640.000, and 1.200.000 masticatory cycles. SEM images were used for evaluating wear qualitatively. The longitudinal results were analysed using linear mixed models (α=0.05). Results. Materials (p<0.001) and number of masticatory cycles (p<0.001) had a significant effect on the wear level. The least enamel antagonist wear was observed for MAZ and MEZ (27.3±15.2, 28±11.1 µm, respectively). GZC (118±30.9 µm) showed the highest wear of enamel antagonists. The highest wear rate in the material was observed in GZS (91.3±38.6 µm). While in the groups of MA, VZ, GZC and GZS 50% of the specimens 2 developed cracks in enamel, it was 100% in MAZ and MEZ groups. Conclusion. Polished monolithic zirconia showed lower wear rate on enamel antagonist as well ...

This study determined the discoloration of five CAD/CAM resins, four manually polymerized resins, and glass-ceramic as control group. Specimens were divided into three groups (N=300, n=30) to be stored in coffee, black tea and red wine (n=10). The discoloration was measured using a spectrophotometer after 1, 7, 29, 90, 180 days storage. All tested groups showed color change (ΔE) at all time points. The manually polymerized resin composites GD (Gradia) and CM (CronMix K), and the CAD/CAM resin composite HC (Blanc High-class) showed significantly higher ΔE compared to all other groups in all tested media. The discoloration was extrinsic and decreased after polishing for the majority of the tested materials. Except CAD/CAM resin HC (Blanc High-class), all CAD/CAM resins showed similar color stability compared to the control group.

OBJECTIVE: This study tested the fracture load of milled and conventionally fabricated polymeric and glass-ceramic three-unit fixed dental prostheses (FDPs) after aging. MATERIALS AND METHODS: FDPs were fabricated (N = 1,050) from four computer-aided design and computer-aided manufacturing (CAD/CAM) resins: (1) AT (artBlock Temp); (2) TC (Telio CAD); (3) ZP (ZENO PMMA); (4) CT (CAD-Temp); two conventionally fabricated resins, (5) IES (integral esthetic press), (6) CMK (CronMix K), and a glass-ceramic (control) (7) PG (IMAGINE PressX). Specimens of each group were tested immediately after fabrication (n = 15 per material). Seventy-five FDPs per material type were stored in artificial saliva (37°C) and 15 of them were randomly selected after aging (1, 7, 28, 90, and 180 days) for fracture load measurement. The remaining specimens (n = 60 per material) were subjected to chewing simulation (×120.000-1.200.000, 49 N, 5°C/50°C). The data were analyzed using two-way and one-way ANOVA followed by Scheffé test. RESULTS: The interactions between FDP materials and aging time in both storage media showed a significant impact on the results (p < 0.001). Among saliva storage groups, TC and ZP showed the highest, and PG the lowest fracture load (p < 0.05). AT and CT were not affected from chewing simulation. TC, ZP, and AT presented the highest in ascending order (p < 0.05), PG and CMK showed the lowest fracture load after chewing simulation (p < 0.001). CONCLUSIONS: Aging did not influence the fracture load of FDPs made of CAD/CAM resins. FDPs made of glass-ceramic showed significantly lower fracture load than those of all resin FDPs. Clinical relevance: Considering fracture load measurements, CAD/CAM resins tested could be alternative materials to glass-ceramic for FDP construction.

OBJECTIVES: Thermal misfit is discussed as one reason for chipping of veneered zirconia restorations. The aim of the investigation was to assess the effect of thermal misfit on the shear strength of zirconia/veneering ceramic composites. METHODS: Shear strengths of 12 different veneering ceramic/zirconia composites were measured (n=10). The veneering ceramics were fired onto polished Y-TZP. In order to create a strong thermal mismatch, one of the veneering ceramics was intended for use on alumina and one for the metal-ceramic technique. The glass transition temperatures of the veneering ceramics and the coefficients of thermal expansion of all ceramics were measured (n=6). Statistical analysis was performed with one-way ANOVA and a post hoc Bonferroni test (p<0.05). RESULTS: Shear strength ranged from 21.9+/-6.2 to 31.0+/-7.1MPa. The ceramic for the metal-ceramic technique showed spontaneous debonding. The differences in the coefficients of thermal expansion of core and veneer (Deltaalpha) were calculated. In addition the differences between glass transition temperatures of the veneering ceramics and room temperature (DeltaT) as the effective temperature range for stress formation were calculated. Highest shear strength was observed when DeltaalphaDeltaT approximately 1000x10(-6). CONCLUSIONS: Thermal expansion and glass transition temperature of the veneering ceramic have an impact on the shear strength of veneer/zirconia composites. AbstractObjectives: Thermal misfit is discussed as one reason for chipping of veneered zirconia restorations. The aim of the investigation was to assess the effect of thermal misfit on the shear strength of zirconia / veneering ceramic composites. Methods

STATEMENT OF PROBLEM: Computer-aided design and computer-aided manufacturing (CAD/CAM) resins exhibit good mechanical properties and can be used as long-term restorations. The wear rate of such resins and their enamel antagonists is unknown. PURPOSE: The purpose of this study was to test and compare the 2-body wear rate of CAD/CAM resin blocks. MATERIAL AND METHODS: Wear specimens (N=42, n=6) were made from 5 CAD/CAM resins: ZENO PMMA (ZP), artBloc Temp (AT), Telio CAD (TC), Blanc High-class (HC), CAD-Temp (CT); 1 manually polymerized resin: Integral esthetic press (negative control group, IEP); and 1 glass-ceramic: VITA Mark II (positive control group, VM2). The specimens for the wear resistance were aged in a thermomechanical loading machine (49 N, 1.67 Hz, 5/50°C) with human enamel antagonists. The material loss of all specimens before, during, and after aging was evaluated with a 3DS profilometer. The measured material loss data of all tested groups were statistically evaluated with linear mixed model analysis (a=.05). RESULTS: Manually polymerized resin showed significantly higher material wear (P<.001) than all other tested groups. Glass-ceramic showed significantly lower wear values (P<.001) than CAD/CAM resins ZP, AT, HC, CT, and IES. CAD/CAM resin TC was not significantly different from the positive control group. Glass-ceramic showed the highest enamel wear values (P<.001) of all tested resins. No differences were found in the enamel wear among all resins. The glass-ceramic group showed damage in the form of cracks on the worn enamel surface in 50% of specimens. CONCLUSIONS: CAD/CAM resins showed lower wear rates than those conventionally polymerized. Only one CAD/CAM resin, TC, presented material wear values comparable with glass-ceramic. The tested glass-ceramic developed cracks in the enamel antagonist and showed the highest enamel wear values of all other tested groups. DOI: https://doi.org/10.1016/S0022-3913 (13) Purpose. This study tested and compared the 2-body wear rate of CAD/CAM resin blocks. CAD/CAM resins with lower wear than conventionally polymerized resins may be an appropriate choice for long-term use because they showed lower wear on enamel antagonists than glass-ceramic. Material