Under the conditions of this study, ferrule-containing endocrown preparations demonstrated significantly greater failure loads than standard endocrown restorations; however, calculated failure stress based on available surface area for adhesive bonding found no difference between the groups. Lower instances of catastrophic failure were observed with the endocrown preparations containing 1 mm of preparation ferrule design; however, regardless of the presence of ferrule, this study found that all endocrown restorations suffered a high proportion of catastrophic failures but at loads greater than reported under normal masticatory function.

Under the conditions of this study, mandibular molars restored with the endocrown technique with 2- and 4-mm pulp chamber extensions displayed greater tooth fracture resistance force as well as stress. All groups demonstrated a high number of catastrophic fractures, but these results may not be clinically significant because the fracture force results are higher than normal reported values of masticatory function.

The purpose of this study was to compare the shear bond strengths to dentin of two dual-cure resin cements, one with a unique initiator, NX3 (Kerr Corp), and the other with a traditional redox-initiator system, Calibra (Dentsply), when used in combination with simplified or nonsimplified adhesive agents. The two dual-cure resin cements, in either self- or dual-cure activation modes, were bonded to human dentin with four dental adhesives to create 16 subgroups of 10 specimens each. After 24 hours of storage in distilled water at 37°C, the specimens were tested in shear in a universal testing machine. With both NX3 and Calibra, bond strengths significantly increased when the specimens were dual cured. In addition, with either cement in either mode, the nonsimplified adhesives performed significantly better than did the simplified adhesive bonding agents. When used specifically with simplified adhesives in either cure mode, NX3 did not produce significantly higher bond strengths than did Calibra. In general, lower dentin bond strengths were found with simplified adhesives or self-cure activation with either resin cement.

These in vitro results suggest that adhesive CAD/CAM technology may compensate for less than optimal AWH.

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