Fracture Resistance of Zirconia-Reinforced Lithium Silicate Ceramic Crowns Cemented with Conventional or Adhesive Systems: An In Vitro Study

Abstract

In recent years, Zirconia-reinforced Lithium Silicate ceramic (ZLS), combining lithium-silicate and zirconia features, has shown to have excellent mechanical and aesthetic characteristics. Thus, the aim of this study was to compare the fracture strength of ZLS single crowns cemented with two different cementation techniques. Twenty crowns were realised and cemented on teeth replicas achieved from an extracted premolar human tooth. The samples were divided into two groups of 10 specimens each, Glass-ionomeric cement (GIC) group and Self-Adhesive Resin Cement (ARC) group. The mechanical test was performed using a universal testing machine. The specimens were then evaluated with a scanning electron microscope (SEM) to identify for all crowns and related abutments the pattern of fracture after the breaking point. The data obtained were statistically analysed. The mean fracture toughness values and standard deviations (±SD) were 2227 ± 382 N and 3712 ± 319 N respectively for GIC and ARC groups. In fact, t-test showed a statistically significant difference between the two groups (p < 0.001). Moreover, the SEM results demonstrated portions of abutments still attached to the crown fragments in the ARC group, whilst these were not present in the GIC group. Within the limitations of this study, these results suggest the use of adhesive cementation for ZLS crowns, which significantly increase the compressive strength of ZLS restorations compared to GIC.

Evaluation of Marginal/Internal Fit and Fracture Load of Monolithic Zirconia and Zirconia Lithium Silicate (ZLS) CAD/CAM Crown Systems

“…However, from a clinical standpoint, the findings need to be interpreted with caution, as the fracture loads do not completely represent failures in intra-oral use. The fracture resistance values (4677 ± 1742 N) found in this report for ZLS crowns were higher than the mean values of 3056 N to 3712 N reported in other recent papers [ 49 , 58 , 75 ] on ZLS crowns. However, the results of this study also matched the findings of some papers that found fracture strength values of 4570 ± 1242 N [ 76 ] and 4100 N [ 58 ], albeit with milled monolithic LDS crowns.…”

“…A self-adhesive resin cement was used in the current paper for cementation of crowns on the master dies. Notable differences in fracture loads of ZLS crowns have been reported by previous studies [ 29 , 49 ] when used with different types of cements, and the results might have also been different in this study, too, if other luting cements (glass ionomer or resin-modified glass ionomer) were used instead of or in comparison to self-adhesive resin. A single CAD/CAM system and 5-axis milling machine were used in this study for fabricating both types of crowns, thus providing standardization and eliminating the influence of software and milling unit differences on the final outcomes.…”

“…Subsequently, the metal dies were embedded in poly methyl methacrylate resin (PMMA) (Orthoplast acrylic resin, Vertex, Soesterberg, Netherlands), contained in a cylindrical brass mold, and vertically positioned until PMMA resin was set for easy handling and retention of the crown-abutment complex when subjected to fatigue and load-to-failure tests. Prior to the actual testing, all 32 samples (16 Zi and 16 ZLS crowns) cemented on abutment metal dies were stored by immersing in distilled water at room temperature for at least 1 week [ 32 , 48 , 49 ].…”

PICN Nanocomposite as Dental CAD/CAM Block Comparable to Human Tooth in Terms of Hardness and Flexural Modulus

“…In materials science, contemporary CAD/CAM blocks are categorized into three groups, namely metal-based (e.g., titanium alloy [ 4 ] and Co-Cr alloy [ 5 ]), ceramic-based (e.g., feldspathic porcelain [ 6 ], lithium disilicate glass [ 7 ] and zirconia [ 8 ]), or resin-based (e.g., acrylic resin [ 9 ] and resin composite (hereafter composite) [ 10 ]). An investigation of new composites already in use (e.g., poly(ether-ether-ketone) (PEEK) [ 11 ]) and some interesting research on new materials with hierarchized geometry [ 12 ] and biomechanical problems [ 13 , 14 , 15 ] (i.e., bruxism) have also been conducted thus far.…”

Influence of Dentine Pre-Treatment by Sandblasting with Aluminum Oxide in Adhesive Restorations. An In Vitro Study

“…The identification of defects at the tooth/restoration interface, represents an early sign of adhesive failure before the longevity of the restoration itself is compromised [ 12 ]. Over the years, different adhesion protocols, alternative materials, and substrate pretreatment procedures able to influence the degree of adhesion have been studied [ 13 , 14 , 15 , 16 ]. In this regard, chemical or mechanical dentin pretreatments are procedures that increase the roughness of the treated surface and may influence the adhesion strength of a bonding agent by increasing the contact area between the dentine and the adhesive surface [ 17 ].…”