Reliability and mode of failure of bonded monolithic and multilayer ceramics.

Objectives: To evaluate the reliability of monolithic and multilayer ceramic structures used in the CAD-on technique (Ivoclar), and the mode of failure produced in ceramic structures bonded to a dentin analog material (NEMA-G10).

Methods: Ceramic specimens were fabricated as follows (n=30): CAD-on- trilayer structure (IPS e.max ZirCAD/IPS e.max Crystall./Connect/IPS e.max CAD); YLD- bilayer structure (IPS e.max ZirCAD/IPS e.max Ceram); LDC- monolithic structure (IPS e.max CAD); and YZW- monolithic structure (Zenostar Zr Translucent). All ceramic specimens were bonded to G10 and subjected to compressive load in 37°C distilled water until the sound of the first crack, monitored acoustically. Failure load (L) values were recorded (N) and statistically analyzed using Weibull distribution, Kruskal-Wallis test, and Student-Newman-Keuls test (α=0.05).

Results: L values of CAD-on and YZW structures were statistically similar (p=0.917), but higher than YLD and LDC (p<0.01). Weibull modulus (m) values were statistically similar for all experimental groups. Monolithic structures (LDC and YZW) failed from radial cracks. Failures in the CAD-on and YLD groups showed, predominantly, both radial and cone cracks.

Significance: Monolithic zirconia (YZW) and CAD-on structures showed similar failure resistance and reliability, but a different fracture behavior.