Influence of Preparation Reconstruction on the Compressive Strength of CAD/CAM Ceramic Inlays

Abstract

The aim of this study was to evaluate whether the compressive strength of lithium dissilicate ceramic inlays is influenced by the substrate (dentin or composite resin build-up) and to compare it to nonrestored teeth. Thirty freshly extracted human maxillary third molars were selected and randomly ascribed to three groups (n=10). Standardized Class II MOD preparations were made (bucco-palatal width = 2/3 of the intercuspal width and 2/3 of the width at the tooth equator for the proximal boxes), varying the extension of the preparations (Group 2: preparation limited to tooth structure; Group 3: pulpal floor of the preparation rebuilt with composite resin, IPS Empress Direct, restored with lithium dissilicate CAD/CAM ceramic inlays (e.max CAD) and cemented with a resin cement (Variolink II)). All groups were subjected to compressive strength test (1mm/min crosshead speed). The results showed that the fracture strength of G1 (control group) was significantly higher than G2 and G3, while within these groups there were no statistically significant differences. Both groups restored with lithium dissilicate restorations did not reach the fracture strength of the sound teeth but were statistically equivalent and sufficient to withstand physiologic masticatory forces.

Effect of Inlays, Onlays and Endocrown Cavity Design Preparation on Fracture Resistance and Fracture Mode of Endodontically Treated Teeth: An In Vitro Study

“…4 The quantity and quality of the remaining tooth structure should be considered in order to define the best restorative option for each case, since extensive restorations weaken the remaining tooth structure. 5 Moreover, tooth weakening is caused by the loss of strategic internal tooth architecture at the center of the tooth and the marginal ridges. 6 A wide range of cavity designs for mesio-occlusal-distal (MOD) preparations were proposed for the posterior teeth dependent on the caries extent and residual tooth intact walls.…”

“…9 According to the cusp coverage, the types of restorations can be classified as inlays, which are preparations with no covered cusps, onlays, where at least one cusp is covered, or overlays, where all cusps are covered. [2][3][4][5][6][7][8][9][10] Cuspal coverage results in increasing the longevity of indirect posterior restorations. Endocrown assemble the intraradicular post, the core, and the crown in one component leading to a monoblock restoration.…”

“…In fact, endodontic access cavity preparation was reported as the second largest cause of loss of tooth structure 4 . The quantity and quality of the remaining tooth structure should be considered in order to define the best restorative option for each case, since extensive restorations weaken the remaining tooth structure 5 . Moreover, tooth weakening is caused by the loss of strategic internal tooth architecture at the center of the tooth and the marginal ridges 6 .…”

“…According to the cusp coverage, the types of restorations can be classified as inlays, which are preparations with no covered cusps, onlays, where at least one cusp is covered, or overlays, where all cusps are covered 2–10 . Cuspal coverage results in increasing the longevity of indirect posterior restorations.…”

Microleakage Assessment of CAD/CAM Endo Crown Restorations (an in vitro Study)

“…This restoration can be used to restore teeth with large restorations, fractured cusps, or teeth with extensive caries. The endocrown provides a conservative approach to restoring endodontically treated teeth and can help to improve fracture resistance (Salamoni Sinhori et al, 2019).…”