Journal of Prosthodontics News
Impact of Endodontic Access Design on the Fracture Resistance of Zirconia Mandibular Molar Crowns
Now online in the Journal of Prosthodontics, a study on the fracture resistance of zirconia mandibular molar crowns co-authored by ACP Fellows Salahaldeen Abuhammoud, DDS, MS, FACP, and Damian J. Lee, DDS, MS, FACP.
It is generally recommended to place a full-coverage crown on posterior teeth after endodontic treatment. A recent study showed that endodontically treated posterior teeth without a crown have a six-times greater rate of failure. Clinicians have proposed various access cavity designs for the mandibular first molar in clinical reports, but no studies have evaluated the fracture resistance of crowns fabricated with different endodontic access designs for the mandibular first molar.
This study sought to evaluate and compare the fracture resistance of zirconia mandibular molar crowns with the traditional trapezoidal (TT) shaped access and three novel conservative access designs: conservative trapezoidal (CT), ultraconservative circular (UC), and two conservative single accesses (TC).
A mandibular right first molar typodont tooth was prepared for a full coverage zirconia crown. The preparation was scanned, and a total of 56 monolithic zirconia crowns were milled. Resin dies were printed for each restoration. Crowns were cemented with dual curing resin cement to the printed dies. The specimens were artificially aged with 10,000 thermal cycles between 5°C and 55°C with a dwell time of 30 s and were loaded to failure using a universal testing machine.
Zirconia crowns with single conservative or ultraconservative access showed significantly higher fracture resistance than those with traditional access. Crowns with two conservative accesses were weaker than those with a single access, regardless of design.
Clinicians must carefully balance conservative cavity access, which preserves tooth structure but may limit effective canal debridement, against traditional cavity access, which involves greater removal of tooth structure or the existing crown.
Abuhammoud S, Jurado CA, Rojas-Rueda S, Garcia-Contreras R, Vegh D, Lee D. Impact of endodontic access design on the fracture resistance of zirconia mandibular molar crowns. J Prosthodont. 2025; 1–7. https://doi.org/10.1111/jopr.70047
Previous
Next
Back to News