PURPOSE: The most common failure seen in restorations with a zirconia core is total or layered delamination of the ceramic veneer. In the present study, the shear bond strengths between veneering ceramics and colored zirconia oxide core materials were evaluated. MATERIALS AND METHODS: Zirconia discs (15 x 12 x 1.6 mm) were divided into 11 groups of 12 discs each. Groups were colored according to the Vita Classic scale: A3, B1, C4, D2, and D4. Each group was treated with the recommended shading time for 3 s, or with prolonged shading for 60 s, except for the control group. Samples were veneered with 3 mm thick and 3.5 mm in diameter translucent ceramic and subjected to shear test in a universal testing machine with a crosshead speed of 1 mm/min. One-way analysis of variance (ANOVA) and Tukey's HSD tests were used for comparisons of the groups having the same shading times. A paired t-test was used for groups of the same color (3 s/60 s). RESULTS: Among the 11 groups investigated C4 (3 s) had the highest bond strength with a value of 36.40 MPa, while A3 (3 s) showed the lowest bond strength with a value of 29.47 MPa. CONCLUSION: Coloring procedures can affect zirconia/ceramic bond strength. However, the results also showed that bond strengths of all the investigated groups were clinically acceptable.
Ceramics*

PURPOSE: The aim of this study was to compare the translucency of two different laminate ceramic veneers with and without glazing. MATERIALS AND METHODS: Ten millimeter side square-shaped specimens in 0.3 mm and 0.6 mm thick were fabricated for the following materials with and without glazing (n=80): A1 shade IPS e.maxPress (IEM) and Styleveneers (STV). The color coordinates (CIE L* a* b*) of the specimens were measured with a colorimeter. The Translucency parameter (TP) was calculated from the color difference of the material on a black versus a white background. For comparisons between materials and between the' not glazed'and' glazed'groups, unpaired t-test was used to analyze the data (P=.05). RESULTS: The TP (Mean +/- SD) of' not-glazed'and' glazed'group of IEM specimens at 0.3 mm thickness were 45.99 +/- 3.00 and 49.53 +/- 2.28 and the TP at 0.6 mm thickness were 32.82 +/- 2.59 and 43.02+/-0.98, respectively. Likewise, the TP of' not-glazed'and' glazed'group of STV specimens at 0.3 mm thickness were 47.03 +/- 3.65 and 50.95 +/- 3.05 and the TP at 0.6 mm thickness group were 34.48 +/- 1.28 and 43.39 +/- 1.20, respectively. As the glazing of ceramic veneer differed, the TP of each ceramic veneer showed statistically significant difference. But, the result between the products was not statistically different. CONCLUSION: Within the limitations of this study, we are concluded that the glazing process changed translucency of laminate ceramic veneers and the TP would not be affected by products.
Ceramics*

No abstract available.
Ceramics* ; Metals*

PURPOSE: The aims of the study were to evaluate the fracture load of zirconia core material after dipping in coloring liquid at different time intervals and to compare the color of dipped blocks with that of prefabricated shaded blocks. MATERIALS AND METHODS: 3-unit bridge frameworks were designed digitally. Sixty frameworks were fabricated using uncolored zirconia blocks by CAD/CAM and divided into 4 groups randomly (n = 15). Group 2 (G2) was subjected to coloring liquids for 2 minutes, Group 4 (G4) for 4 minutes, and Group 6 (G6) for 6 minutes. CFS group was not subjected to any coloring procedure. After coloring, color differences between the test groups and a prefabricated shaded zirconia group (CPZ, n = 15) were evaluated by using a spectrophotometer. Fracture test was conducted immediately after shade evaluation with a Testometric test device at a cross-head speed of 1 mm/sec. Statistical analysis for evaluating color and fracture load was performed by using one way ANOVA followed by Tukey HSD test (P ≤ .05). Weibull analysis was conducted for distribution of fracture load. RESULTS: There was no difference in terms of fracture load and color between CFS (1176.681 N) and G2 (985.638 N) group and between CPZ (81.340) and G2 (81.140) group, respectively. Fracture load values of G4 (779.340 N) and G6 (935.491 N) groups were statistically significantly lower than that of CFS group (P ≤ .005). The color values of G4 (79.340) and G6 (79.673) groups were statistically different than that of CPZ group (P ≤ .005). CONCLUSION: Prolonged immersion of zirconia in coloring liquid not only negatively affected the fracture load of the zirconia being tested in the current study but also deteriorated the desired shade of the restoration.
Ceramics* ; Immersion

PURPOSE: Polymer infiltrated ceramic network (PICN) materials, also called hybrid ceramics, are new materials in dental market. The manufacturer of the PICN material VITA Enamic suggests 3 different finishing procedures for this new material. In the present study, surface roughness and color differences caused from different finishing procedures of VITA Enamic were investigated. MATERIALS AND METHODS: 120 specimens were prepared in dimensions 2 x 10 x 12 mm from VITA Enamic hybrid ceramic blocks with 'high translucency' and 'translucency 2M2' shades. The specimens were divided into 8 groups. For each group, different finishing procedures suggested by the manufacturer were performed. Surface roughness values were determined by a tactile portable profilometer. Color changes were evaluated using a clinical spectrophotometer. The data were analyzed using one-way ANOVA and Tukey's post-hoc comparison. The significance level was set at alpha=0.05. RESULTS: The roughest surfaces were observed in Glaze Groups. Their surface roughness values were similar to that of the control group. Clinical Kit and Technical Kit groups did not show a statistically significant difference regarding surface roughness (P>.05). The largest color difference regarding DeltaE00 was observed in Clinical Kit finishing groups. There were also statistically significant color changes between the groups (P<.05). However, all the groups showed clinically acceptable color change (DeltaE(00)<2.25) except Clinical Kit Groups (DeltaE(00)>2.25). CONCLUSION: Within the limitations of the present study, it may be suggested that finishing the VITA Enamic restorations by Technical Kit instead of Glaze and Clinical Kit gives better clinical performance in regard to surface roughness and shade matching.
Ceramics* ; Polymers*

The effect of thermocycling and surface finishing on the marginal fidelity of copings for a metal ceramic crown was examined. Methods for minimizing the loss of marginal fidelity were evaluated. The results were as follows ; 1. Thermocycling of ceramic metal coping resulted in increased marginal gap. 2. The greatest marginal gap occurred during the first thermocycling of the copings. 3. No additional distortion of marginal fidelity occurred when surface finishing and second thermocycling were completed after initial thermocycling. 4. The gab increases according to various treatment methods showed group 1 to be the highest values. 5. There was no significant difference between group 2 and group 3(p>0.05). 6. There was significant difference between group 1 and group 2, 3(p<0.05). 7. There was no significant difference among the measurement sites.
Ceramics* ; Crowns

The effect of thermocycling and surface finishing on the marginal fidelity of copings for a metal ceramic crown was examined. Methods for minimizing the loss of marginal fidelity were evaluated. The results were as follows ; 1. Thermocycling of ceramic metal coping resulted in increased marginal gap. 2. The greatest marginal gap occurred during the first thermocycling of the copings. 3. No additional distortion of marginal fidelity occurred when surface finishing and second thermocycling were completed after initial thermocycling. 4. The gab increases according to various treatment methods showed group 1 to be the highest values. 5. There was no significant difference between group 2 and group 3(p>0.05). 6. There was significant difference between group 1 and group 2, 3(p<0.05). 7. There was no significant difference among the measurement sites.
Ceramics* ; Crowns

OBJECTIVETo investigate the microstructure of dental zirconia ceramics prepared by two-step sintering.

METHODSNanostructured zirconia powder was dry compacted, cold isostatic pressed, and pre-sintered. The pre-sintered discs were cut processed into samples. Conventional sintering, single-step sintering, and two-step sintering were carried out, and density and grain size of the samples were measured. Afterward, T1 and/or T2 of two-step sintering ranges were measured. Effects on microstructure of different routes, which consisted of two-step sintering and conventional sintering were discussed. The influence of T1 and/or T2 on density and grain size were analyzed as well.

RESULTSThe range of T1 was between 1450 degrees C and 1550 degrees C, and the range of T2 was between 1250 degrees C and 1350 degrees C. Compared with conventional sintering, finer microstructure of higher density and smaller grain could be obtained by two-step sintering. Grain growth was dependent on T1, whereas density was not much related with T1. However, density was dependent on T2, and grain size was minimally influenced.

CONCLUSIONTwo-step sintering could ensure a sintering body with high density and small grain, which is good for optimizing the microstructure of dental zirconia ceramics.

The purpose of this study comparatively analyzed the machinability of various dental hybrid blocks manufactured by using the CAD/CAM system. Three hybrid composite blocks (Vita enamic, Lava Ultimate, GC Cerasmart) were used for experimental groups and one conventional ceramic block (Vita Mark II) was used for control. The digital impression of the master model and abutment was taken by using a scanner, and then the CAD software program was used to design restorations. The four-axis milling machine (inLab MCXL; Sirona Dental Systems GmbH, Bensheim, Germany) was used four materials. The digitized data was superimposed with 3D inspection software to quantitatively obtain the machinability of a ceramic crown, and visual differences were confirmed with a color map. The root mean square (RMS) values of ceramic crown group were statistically analyzed with one-way ANOVA (α=0.05). While there was a significant difference in the machinability of the internal surface, among four groups, there was statistically significant difference between conventional (VM group) and hybrid ceramic (VE, LU, GC groups) (p<0.05). Consequently, the machinability of VM is lower than that of other hybrid ceramics, and the machinability of VE is better than that of LU and GC. For ceramics as final restorations, manufacturing of dental restorations using hybrid composite ceramic is recommended.
Ceramics ; Crowns

The purpose of this study was to investigate the possibility on recycling of IPS-Empress ceramic for the wide use of IPS-Empress ceramic in prosthodontic treatment. The frexure strength of first pressed, second pressed, and third pressed IPS-Empress ceramic were measured and compared. There was no ststistical difference among three groups, and the result of this study implied the recycled IPS-Empress ceramic has enough frexure strength for clinical use.
Ceramics* ; Prosthodontics ; Recycling