Fracture Resistance of Endocrown Restorations: An Integrative Literature Review

Abstract

Introduction: Endocrown restorations have been established as a minimally invasive alternative for the rehabilitation of endodontically treated teeth with extensive coronal loss. However, different restorative materials exhibit distinct biomechanical behaviors, which may influence fracture resistance and clinical longevity. Objective: To conduct an integrative literature review assessing the mechanical performance and failure mode of endocrown restorations fabricated with different restorative materials. Methods: An integrative review was carried out in the PubMed/MEDLINE, SciELO, and LILACS databases, including in vitro studies published between 2015 and 2025, in English, that evaluated the fracture resistance of endocrowns in permanent teeth. Reviews, meta-analyses, case reports, opinion articles, studies in other languages, and research on deciduous teeth were excluded. Results: of 681 articles identified, five studies were included, evaluating lithium disilicate, zirconia, polyether-ether-ketone (PEEK), polymer-infiltrated ceramics, and resin composites. Zirconia and lithium disilicate recorded high fracture resistance values, frequently exceeding physiological masticatory loads, but were associated with catastrophic failures. Resilient materials such as PEEK, resin composites, and polymer-infiltrated ceramics showed more favorable and potentially repairable failure patterns; in the studies comparing PEEK and lithium disilicate, PEEK exhibited superior fracture resistance. Cavity design and artificial aging protocols significantly influenced the results. Conclusion: no single material demonstrated superiority in all clinical situations. Although zirconia and lithium disilicate present high fracture resistance, resilient materials — particularly PEEK — achieved fracture resistance superior to lithium disilicate, with the additional benefit of failure patterns more favorable to the preservation of the remaining tooth structure. Thus, the mechanical performance of endocrowns depends on the interaction between material properties, elastic modulus, adhesive capacity, and cavity design, with fracture resistance alone being an insufficient parameter to predict clinical success.