The influence of endodontic access preparation on the mechanical strength of zirconia crowns: A literature review

As the use of monolithic zirconia crowns continues to increase in clinical practice, understanding the impact of post-cementation endodontic intervention is essential for long-term restorative success. This review aims to evaluate the impact of endodontic access on the fracture resistance of monolithic zirconia crowns to guide evidence-based clinical decisions. An electronic search was conducted in PubMed, Scopus, Web of Science, and Embase for in-vitro studies published between 2010 and 2024. Studies were included if they assessed fracture resistance of zirconia crowns before and after endodontic access. Data on zirconia type, cavity design, bur type, cementation method, and crown design were extracted and analyzed descriptively. Eight studies met the inclusion criteria. Fracture resistance was reduced following access preparation, with variations depending on zirconia type, cavity size, and cementation. 3Y-TZP zirconia demonstrated higher resistance than 5Y-TZP. Adhesive resin cement preserved strength better than glass ionomer. Monolithic crowns performed better than layered designs, and conservative cavity design with increased occlusal thickness showed improved outcomes. Endodontic access cavity preparation compromises the fracture resistance of zirconia crowns. However, the negative impact can be minimized by selecting appropriate materials and techniques.