Optical Properties of Five Esthetic Ceramic Materials Used for Monolithic Restorations: A Comparative In Vitro Study

Abstract

Zirconia has generated tremendous interest in the esthetic materials used for dental restorations. However, using conventional zirconia has some limitations especially in highly esthetically demanding situations, as it lacks the translucency that other ceramic materials possess. This study aimed to evaluate and compare the optical properties (shade, translucency, and opalescence) of three CAD-CAM monolithic multilayer zirconia ceramics (GNX; Ceramill Zolid® Gen-X, ZCP; IPS e.max® ZirCAD, and UPC; Upcera® Esthetic Explore Prime) and one CAD-CAM monolithic multilayer polymer-infiltrated hybrid ceramic (ENM; Vita® Enamic) with a CAD-CAM monolithic lithium disilicate ceramic as control (EMX; IPS e.max® CAD). 200 discs (GNX = 40, ZCP = 40, UPC = 40, ENM = 40, and EMX = 40) were cut, polished, and fully crystallized. Half of the samples for each group were subjected to hydrothermal aging. Descriptive analysis and ANOVA tests were used to compare the groups. Zirconia GNX, ZCP, and UPC groups showed significantly lower optical properties than ENM and EMX groups for both the non-aged and aged samples (p < 0.05). UPC and ENM groups showed a significant decrease in translucency and opalescence after aging (p < 0.05). The optical properties of monolithic multilayer zirconia ceramics were lower than monolithic multilayer polymer-infiltrated hybrid ceramic and lithium disilicate ceramic. Polymer-infiltrated hybrid ceramic was significantly affected by aging.

In-Vitro Evaluation of Strain Induced by Various Extra Coronal Attachment Materials in Removable Partial Dentures Restoring Mandibular Kennedy Class I Following Clinical Simulation for One Year

“…Statistical analysis revealed a notable discrepancy in the strain caused by the three examined materials for extra-coronal attachments, with PEEK (BioHPP) exhibiting the least amount of strain induced in comparison to both metal and zirconia groups during loading both unilaterally and bilaterally. This observation could be clarified by considering the modulus of elasticity for BioHPP (3-4 GPa) [63] in contrast to the significantly higher moduli of zirconia with value higher than 200 GPa [64] and nickel-chromium approximately 190 GPa [65] . The elevated moduli of zirconia and nickelchromium, in comparison to the modulus of cortical bone in humans nearly 14 GPa [63] could contribute to the increased induced strain observed.…”

Flexural Strength and Morphological Study of Different Multilayer Zirconia Dental Materials

“…Recently, the new generations of monolithic zirconia ceramic systems have also increased the Y 3+ content to approximately 4 and 5 mol%. These ceramics systems contain a higher portion of c-ZrO 2 polycrystals, which contribute to enhanced optical properties [ 11 ]. A type of this ceramics system is called “multilayer” as it has layers of polychromatic and translucent zirconia that produce a gradient effect, ranging from enamel to dentin shades in the single disc before milling.…”