In-Vitro Comparison of Fracture Strength of Endocrowns and Overlays in Endodontically Treated Teeth Manufactured with Monolithic Lithium Disilicate and Zirconia

Abstract

To evaluate the fracture strength and the failure mode of endodontically treated molars restored with monolithic lithium disilicate and zirconia endocrowns and overlays. A total of 48 extracted mandibular molars were endodontically treated, decoronated 2 mm above the cementoenamel junction and divided into four 12-specimen groups. Group ELD: lithium disilicate endocrowns. Group EZ: monolithic zirconia endocrowns. Group OLD: lithium disilicate overlays. Group OZ: monolithic zirconia overlays. Overlays did not extend in the pulp chamber and endocrowns extended in the pulp chamber 2 mm. After adhesive bonding of the restorations, the specimens were subjected to thermocycling (×5000 cycles) and then to fracture resistance testing at lateral static loading (1 mm/min) at a universal testing machine. The failure mode of the specimens was qualitatively evaluated. Differences in means were compared using with t-tests for independent samples or Mann–Whitney test (p < 0.05). Weibull distribution analysis was also performed. Group ELD showed significantly higher fracture strength than all other groups (p = 0.001), and the highest Weibull modulus. Conclusions: Lithium disilicate endocrowns exhibit higher fracture strength and are more reliable compared to the other types of restorations examined. Endocrowns had more catastrophic failures compared to overlays.

Application of one-piece endodontic crowns fabricated with CAD-CAM system to molars

“…The classification of CAD-CAM endocrown materials by their types is shown in Table 1 [5] , [6] , [7] , [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] , [42] . Comparing each material, the maximum and minimum fracture resistance against a load to CAD-CAM endocrowns was the highest in resin composite, followed by ceramic and zirconia.…”

“…Table 2 shows the fracture modes for axial and lateral loading on each material type [5] , [6] , [8] , [9] , [10] , [12] , [16] , [17] , [18] , [20] , [22] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] , [40] , [42] . The resin composite type was the most frequently reported as repairable in terms of fracture mode [5] , [6] , [8] , [10] , [18] , [20] , [24] , [25] , [26] , [27] , [28] , [29] , [31] , [34] , [35] .…”