Pulp Chamber Depth Effect on Mandibular Molar EndoCrown Retention

Objectives: To evaluate the effect of pulp chamber depth with retention of adhesively-luted mandibular molar CADCAM Endocrowns.
Methods: Recently-extracted mandibular third molars were randomly divided into 3 groups (n=12) with the coronal tooth structure removed perpendicular to the root long axis approximately 2mm above the CEJ with a water-cooled, slow-speed diamond saw. The pulp chamber was exposed using a diamond bur in a high speed handpiece. Pulpal remnants were removed and canals instrumented using endodontic hand instruments. The chamber floor was adhesively (Optibond Fl) based with a flowable resin (TetricEvo Flow) and photopolymerized with a visible light curing unit (Bluephase G2) to create endocrown preparation depths of 2, 3 and 4mm. Completed preparation surface area was determined using a digital measuring microscope (Hirox). Scanned preparations (CEREC) were fitted with e.max CAD crowns and luted with RelyX Unicem after HF acid etching and silanation. All manufacturer recommendations were followed. Specimens were stored at 37C/98% humidity and tested to failure after 24 hours at a 45-degree angle on a universal testing machine. Failure load was converted in MPa using the available bonding surface area with mean data analyzed using ANOVA/ Tukey’s post hoc test (p=0.05).
Results: Results are listed in the table. 2 and 4mm pulpal depth Endocrown preparations demonstrated the greatest failure resistance.
Conclusions: Under the conditions of this study, mandibular molars restored with Endocrowns consisting of 2- and 4mm pulp chamber depths displayed greater failure resistance. There was no significant difference noted between the 3- and 4mm groups. These results may not be clinically significant.