Browsing School, Graduate by Subject "zirconia"
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The Color Stability of 3D-Printed and Milled Zirconia CrownsPurpose: This is an in vitro study on the color stability of 3D-printed and milled zirconia crowns. Materials and Methods: A total of 18 samples were tested, 9 milled and 9 printed zirconia crowns. Change in color (ΔE) was assessed before and after samples were soaked in solutions of coffee, chlorhexidine and distilled water for a simulated period of 1 week. Two-way ANOVA was used to compare between the groups. Results: There was a significant difference (P = .003) between ΔE of samples soaked in chlorohexidine (4.24 ±3.62) versus coffee (8.84 ±7.48) and between ΔE of samples milled (1.64 ±1.12) versus printed (11.11 ±3.96, P ≤ .0001). Conclusion: Printed zirconia crowns are more susceptible to staining than milled crowns. Printed zirconia crowns appeared noticeably darker when soaked in coffee and lighter when soaked in distilled water and chlorohexidine.
Surface Roughness of Zirconia Produced by Additive and Subtractive ManufacturingPurpose – The purpose of this in vitro study was to compare surface roughness of full contour zirconia restorations produced by additive and subtractive manufacturing Materials and Methods – Full contour restorations were designed using 3Shape Dental System. The stl files were exported and utilized to guide production of all specimens. Zirconia samples were manufactured by two methods – additive manufacturing (n=10) and subtractive manufacturing (n=18). A two-step polishing protocol was used following sintering. All specimens were subject to profilometry to measure average Ra values. Ra values for both groups were compared. Statistical analysis was performed using t-test (p=0.05). Results – The average Ra value for zirconia restorations in the subtractive manufacturing group was 0.35 ±0.07µm while average Ra for additive manufacturing groups was 1.06 ±0.49 µm. Differences were statistically significant (p < 0.00001). Conclusions – Zirconia restorations produced by subtractive manufacturing were significantly smoother than those produced by additive manufacturing even after post-sintering polishing.