Fracture Resistance of Various Thickness e.max CAD Lithium Disilicate Crowns Cemented on Different Supporting Substrates: An In Vitro Study

Abstract

Purpose:To investigate the influence of abutment material properties on the fracture resistance and failure mode of lithium disilicate (IPS e.max) CAD/CAM (computeraided design/manufacturing) crowns on traditionally and minimally prepared simulated tooth substrates. Materials and Methods: Thirty lithium disilicate (IPS e.max) CAD/CAM crowns were divided into three groups (n = 10): TD: traditional thickness crowns cemented on Paradigm MZ100 abutments; MD: minimal thickness crowns cemented on Paradigm MZ100 abutments; ME: minimal thickness crowns cemented on e.max abutments. The 3Shape system was used to scan, design and mill all abutments and crowns with a die space set to 40 µm. Traditional thickness crowns were designed based on manufacturer guidelines with 1.5 mm occlusal thickness and 1.0 mm margins. Minimal thickness crowns were designed with 0.7 mm occlusal thickness and 0.5 mm margins. MZ100 composite and e.max abutments were selected to simulate dentin and enamel substrates, respectively, based on their elastic-modulus. Variolink Esthetic was used to cement all samples following manufacturer's instructions. A universal testing machine was used to load all specimens to fracture with a 3 mm radius stainless steel hemispherical tip at a crosshead speed 0.5 mm/minute along the longitudinal axis of the abutment with a 1 mm thermoplastic film placed between the loading tip and crown surface. Data was analyzed using ANOVA and Bonferroni post hoc assessment. Fractographic analysis was performed with scanning electron microscopy (SEM). Results: The mean fracture load (standard deviation) was 1499 (241) N for TD; 1228 (287) N for MD; and 1377 (96) N for ME. Statistically significant difference between groups did not exist (p = 0.157, F = 1.995). In groups TD and MD with low e-modulus abutments, the dispersion of a probability distribution (coefficient of variation: CV) was statistically higher than that of group ME with high e-modulus abutments. SEM illustrated larger micro-fracture dimensions in Group MD than Group ME. Conclusion: Minimal thickness e.max crowns did not demonstrate statistical difference in fracture resistance from traditional thickness crowns. Fracture mechanisms of minimal thickness e.max crowns may be affected by the e-modulus of the substrate. Minimal thickness e.max crowns may be a viable restorative option when supported by high e-modulus materials.

Fracture Resistance and Failure Mode of Mandibular Molar Restored by Occlusal Veneer: Effect of Material Type and Dental Bonding Surface

“…Their findings could be related to the different tooth type and the use of self-etch primer [5,9,36]. In addition, a high fracture resistance value was reported for lithium disilicate occlusal veneers, which could be attributed to the non-standardized protocol for cementation and difference in the thickness of the occlusal veneer [42,44,45].…”

“…The fracture resistance testing is crucial for determining how teeth react to highintensity loading [11,15,[42][43][44][45][46]. The aim of this research was to study how occlusal veneer materials (lithium disilicate, zirconia, and polymer-infiltrated ceramic) and dental bonding substrates (dentin, dentin with intra-coronal cavity, and dentin with composite filling) affected the fracture resistance and failure mode of mandibular molars restored with occlusal veneers.…”

Resistance to Fracture of Lithium Disilicate Feldspathic Restorations Manufactured Using a CAD/CAM System and Crystallized with Different Thermal Units and Programs

“…The digital flow allows the standardization of all samples from both crowns and dies. The fracture resistance values of ceramic materials with lithium disilicate reinforcement can be affected depending on the substrate [33]. Considering this, the dies were designed in a standardized way and were resin-printed to approximate the elastic modulus of dentin and to simulate the clinical setting where restorations are performed.…”

Effect of endodontic access simulation on the fracture strength of lithium‐disilicate and resin‐matrix ceramic CAD‐CAM crowns

“…Load-to-failure testing provides information at extreme conditions, therefore the findings of this in vitro study should not be directly related to clinical conditions. 21,22 The constant compressive load was applied until failure on the occlusal surface of the crowns in vertical direction to simulate the normal occlusal relationship of maxillary first premolar 23 for which a loading pattern that is vertical and along the long axis was demonstrated. 24,25 Regarding the effect of endodontic access cavity, differences in fracture strength of intact and repaired LD and RMC CAD/CAM crowns were not significant, suggesting that repair of the crown is feasible and replacement is not necessary.…”