Reliability and failure behavior of CAD-on fixed partial dentures

• This study evaluates the reliability of ceramic fixed partial dentures prepared using the CAD-on technology.
• This study tested the hypothesis that cyclic fatigue influences the reliability and failure behavior of the FPDs when compared to fast fracture testing.
• Porcelain chipping was the predominant (60%) mode of failure for FPDs tested in fast fracture and connector failure was predominant (67%) under fatigue.
• When chipping and connector fracture data were analyzed separately, the β values were 7.9 and 2.9.
• The test method (fast fracture or fatigue) significantly influenced the reliability of FPDs fabricated using the CAD-on technique, but it did not influence their failure behavior.

ObjectivesTo estimate the reliability and failure behavior of fixed partial dentures (FPDs) fabricated using the CAD-on technique.MethodsFPDs (n = 25) were fabricated using a CAD/CAM system: IPS e.max ZirCAD – Crystall./Connect and IPS e.max CAD (Ivoclar). The restoration type (“three-unit bridge”) and design method (“multilayer”) based on Biogenerics were used. Framework and porcelain structures were united using a fusion ceramic (Crystall./Connect, Ivoclar). Mechanical fatigue was tested in a servohydraulic load frame machine at a cyclic loading (frequency: 2 Hz; load ratio: 0.1). Based on previous data from specimens tested in fast fracture, three different stress profiles were used. The lifetime data were analyzed using an inverse power law-Weibull cumulative damage model (ALTA PRO, Reliasoft). All failed specimens were examined under a field emission scanning electron microscope.ResultsPorcelain chipping was the predominant (60%) mode of failure for FPDs tested in fast fracture and connector failure was predominant (67%) under fatigue. For fast fracture data, the Weibull modulus (β) of FPDs was 7.8 combining the two failure modes. When chipping and connector fracture data were analyzed separately, β values were 7.9 and 2.9. For the step stress fatigue test, β values were lower than estimated using fast fracture, being 1.6 for connector fracture and 1.3 for porcelain chipping.SignificanceThe test method (fast fracture or fatigue) significantly influenced the reliability of FPDs fabricated using the CAD-on technique, but it did not influence their failure behavior.