The effect of preparation design on the fracture resistance and adaptation of the CEREC ceramic endocrowns

Abstract

Objective: The purpose of this experimental in vitro study was to assess the effect of having one or two intact axial walls on the improvement of the fracture resistance, and marginal and internal adaptation of computer-aided design/computer-aided manufacturer fabricated ceramic endocrowns.Materials and Methods: Thirty-six endodontically treated mandibular molars were divided into three groups (n = 12). Group A, represented teeth that all of their axial walls were reduced till they all had 3 mm height. In group B, the buccal wall had 5 mm height and the others were reduced to 3 mm. Specimens of the group C had 5-mm-height buccal and one 5 mm-height proximal wall, with all other walls of 3 mm height. All teeth were scanned using intraoral scanner, and endocrowns were milled from zirconia lithium silicate ceramics blocks. The marginal and internal discrepancy of restorations were evaluated with the replica technique. Fracture resistance was also measured after cementation and modes of failure were observed. One-way analysis of variance and Tukey HSD multiple comparisons were used to analyze the data (α = .5).Results: Significant differences were observed within the groups in terms of the axial discrepancy (p = .022); group A had significantly higher amounts of axial discrepancy compared to group B (p = .001) and group C (p = .003). Preservation of the intact axial walls did not result in a statistically significant decrease in marginal (p = .21) and pulpal (p = .31) discrepancy values. Also, concerning the fracture resistance no significant difference was observed among the groups (p = .51). Conclusion:Preservation of at least one of the axial walls could reduce the amount of the axial discrepancy and, therefore, improves the adaptation of the restoration.However, based on this study, it did not improve fracture resistance.

A Comparative Analysis of Marginal Adaptation Values between Lithium Disilicate Glass Ceramics and Zirconia-Reinforced Lithium Silicate Endocrowns: A Systematic Review of In Vitro Studies

“…Overall, and based on the outcomes of the in vitro studies included in this systematic review, the recorded values of the marginal fitting, gap, and marginal adaptation of both LDGC and zirconia endocrowns were within the clinically acceptable value of <120 μm [ 40 , 41 ]. Some in vitro studies documented equal or slightly higher marginal gap values, as documented by Jalali et al, with 160 μm for zirconia CAD/DAM [ 14 ], and by Shin et al, with 138 μm for LDGC CAD/CAM [ 23 ]. An equal value of marginal adaptation or slightly lower values were obvious in laboratory studies conducted by Sağlam et al for both LDGC and zirconia CAD/CAM [ 27 ], LDGC endocrowns constructed with CAD/CAM or heat-press systems [ 25 ], and LDGC manufactured by CAD/CAM [ 22 ].…”

“…Endocrowns can be fabricated by CAD/CAM or heat-press techniques using various ceramic systems, such as lithium silicates and zirconia-reinforced lithium silicates [ 14 , 48 , 49 ]. A variety of the products are used in dental practice and produce prostheses with better accuracy of marginal variation [ 13 , 19 , 21 ].…”

“…Likewise, the software model, record managing, and image triangulation technique affect the resolution and surface features of the last digital impression generated [ 54 ]. Other studies have shown that the 5-axis CAM element offered outstanding accuracy compared with the 4-axis element [ 12 , 14 , 55 ]. Moreover, the marginal adaptations of endocrowns are increased with additional preparation features and increased cavity height and divergence; therefore, declaring the preparation as simple as cavity design lead is proposed [ 56 ].…”

“…Various ceramic systems are used for endocrown fabrications, such as feldspathic ceramics [ 26 , 27 ], lithium disilicate glass ceramics (LDGC) [ 13 , 15 – 19 , 22 , 23 , 25 ], and different types of zirconia [ 13 , 14 , 21 ], which have high mechanical strength and can be acid-etched. Zirconia and LDGC are considered the best choices owing to their mechanical and aesthetic features, including good anti-abrasion, anti-aging, and anti-corrosion properties, translucency, and biocompatibility with natural teeth.…”