Effect of cement type and CAD-CAM material on the retention of ceramic crowns supported by zirconia abutments.

Objectives: The purpose of this in-vitro study was to investigate the effect of cement type and CAD-CAM restorative material on the retention properties of ceramic crowns supported by zirconia abutments.
Methods: A total of 128 crowns were milled from four different restorative materials (IPS e-max CAD-IPS, Vita Suprinity-VS, Vita Enamic-VE and Vita YZ ST-ST)(n=32/group). Crowns were cemented on custom zirconia abutments with either interim cement (Temp Bond-TP), resin-modified glass-ionomer cement (FujiCEM II- FC), self-adhesive cement (RelyX Unicem 2-RX) or adhesive cement (Panavia F 2-PF) (n=8/subgroup), under a load of 5 kg. Test specimens were thermally cycled (5-55°C) for 500 cycles with a dwell time of 30s. The retention properties of the crowns were tested in a universal testing machine by applying a separation force at a cross-head speed of 1.0 mm/min in vertical direction and the maximum force leading to decementation was determined. The obtained data were statistically compared using two-way analysis of variance (ANOVA) and Post-Hoc Tukey HSD tests. Statistical significance was determined at p<.05.
Results: Significant interactions between cement type and CAD/CAM restorative material were observed (p<.05, Table 1). Adhesive cements (RX and PF) showed higher retention values than interim (TB) or resin-modified glass-ionomer cement (FC). The VS crowns presented the highest retention values while ST crowns showed the lowest values (p < 0.05, Table 2).
Conclusions: The retentive properties of implant supported crowns were affected by the type of CAD-CAM restorative material used for prosthetic restoration and cement selection.