09 September 2022

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Evaluation of Endocrown preparation and fracture resistance in endodontically treated teeth

Simona Chirico

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Lateral-posterior teeth, after endodontic therapy, require adequate restorations to re-establish masticatory function and minimize the risk of fracture, as well as ensure a perfect seal to prevent bacterial contamination. Endodontically treated teeth may be restored using various methods, including direct and indirect restorations, with indirect full-coverage methods being preferred by

many clinicians. Computer aided design/computer assisted manufacturing (CAD/CAM) proponents proffer that adhesive technology afforded by the endocrown restoration may provide clinicians

with additional treatment options that may be more efficient and conservative for the restoration of endodontically treated teeth. Several literature studies suggest a central retentive preparation of 2 mm to provide optimal retention and resistance characteristics of the restoration.

Materials and Methods
In an in vitro study, published on Journal of Prosthodontics  January 2019, the authors assessed how the ferrule effect in circumferential preparation can influence the fracture resistance of mandibular molars treated endodontically with endocrown preparation.
Extracted mandibular third molars were randomly divided into 3 groups (n = 12). Two groups received ferrule preparation features to the external coronal surface consisting of 1 and 2 mm placed circumferentially apical to the endocrown occlusal table. The third group did not receive additional preparation features. The preparations were then scanned and rehabilitated with lithium disilicate restorations cemented with a self-adhesive resin according to the CAD / CAM method. The samples were stored at 37 ° C / 98% humidity and after 24 hours the authors tested the fracture strength at a 45° angle to the tooth long axis using a universal test machine.

Results
Endocrown specimens prepared without ferrule design had significantly lower fracture load resistance than samples prepared with ferrule design. Failure mode analysis identified that all preparations demonstrated a high number of catastrophic failures.

Conclusions
Based on the data reported in this in vitro study, ferrule design in endocrown preparations of endodontically treated teeth is an important aid for fracture resistance. This study found that all endocrown restorations suffered a high proportion of catastrophic failures but at loads greater than reported under normal masticatory function.

Clinical implications
Dentists can use endocrown preparations with additional  ferrule design to avoid the long-term fracture resistance of the  prosthetic restoration of endodontically treated teeth. Future studies should further investigate both restoration adaptation to the preparation surface and fatigue studies.