Fracture strength of non-invasively reinforced MOD cavities on endodontically treated teeth
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ORIGINAL ARTICLE
Fracture strength of non‑invasively reinforced MOD cavities on endodontically treated teeth René Daher1 · Stefano Ardu1 · Enrico Di Bella2 · Giovanni T. Rocca1 · Albert J. Feilzer3 · Ivo Krejci1 Received: 22 July 2020 / Accepted: 23 August 2020 © The Author(s) 2020
Abstract The purpose of this in-vitro study was to evaluate the fracture resistance and failure mode of non-invasively reinforced endodontically treated mandibular molars. Sixty freshly extracted defect-free mandibular molars were divided into four experimental groups with extensive MOD cavities on endodontically treated teeth with different restoration types and one control group with intact teeth (n = 12). The groups were as follows: “Normal”: direct resin composite; “Ring”: glass fiberreinforced strip (Dentapreg) wrapped around buccal and lingual walls followed by direct resin composite; “Inlay”: indirect CAD/CAM resin composite inlay; “Onlay”: indirect CAD/CAM resin composite onlay; “Intact”: Intact teeth (Control). Tetric EvoCeram and Adhese Universal (Ivoclar Vivadent) were used for direct restorations and Tetric CAD (Ivoclar Vivadent) adhesively luted with Adhese Universal and Variolink Esthetic LC (Ivoclar Vivadent) were used for indirect restorations. All teeth were submitted to thermo-mechanical cyclic loading. All samples were then submitted to a compressive load until fracture. Fracture load was noted and teeth were analyzed to classify the failure mode as either catastrophic (C) or noncatastrophic (NC). No statistically significant difference was found between fracture strength of the five groups when all specimens were considered (p = 0.1461). Intact group showed the lowest percentage of catastrophic failures (41.67%). Ring group presents less catastrophic failures (75%) than Normal group (83.34%), and failures of indirect restorations—Inlay and Onlay—were almost all catastrophic (91.67% and 100%, respectively). Keywords Inlay · Onlay · Cusp coverage · Endodontically treated teeth · Fiber-reinforced strip
* René Daher [email protected] Stefano Ardu [email protected] Enrico Di Bella [email protected] Giovanni T. Rocca [email protected] Albert J. Feilzer [email protected] Ivo Krejci [email protected] 1
Department of Cariology and Endodontology, University of Geneva, 1 rue Michel‑Servet, 1211 Geneva, Switzerland
2
Department of Political Sciences, University of Genoa, Genoa, Italy
3
Department of Dental Materials Sciences, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit Van Amsterdam and Vrije Universiteit, Gustav Mahlerlaan 3004, 1081 LA Amsterdam, The Netherlands
Introduction Fragility of endodontically treated teeth (ETT) is mostly due to accumulated tissue loss resulting from carious lesions, endodontic access cavities and canal preparation [1]. The first reason has been shown to be the most detrimental [2], since hard tissue removal at the coronal level is associated with a reduction in stiffness of up to 60% and an increase in deflection of the remaining cusps, which
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