• The Color Stability of 3D-Printed and Milled Zirconia Crowns

      Spatz, Harrison; Masri, Radi, 1975-; 0000-0002-3583-7674 (2021)
      Purpose: 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 Manufacturing

      Triana, Frank James; Masri, Radi, 1975- (2021)
      Purpose – 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.