Abstract :
Strength and biocompatibility of any restoration is an important criterion for success and function of any
prosthesis. Despite the high fracture resistance of traditional metal ceramic crowns, limitations are imposed
by esthetic concerns. The objective of this study is to determine whether zirconium dioxide or nickel
chromium copings had better strength when used with two resin based luting cements namely RelyX U100
and Variolink II.
Materials and Methods: A total of 40 copings were fabricated, of which 20 were zirconium oxide copings
made using CAD/CAM technology. The remaining 20 were nickel-chromium copings obtained using Lost
Wax technique. Two resin cements were selected i.e, RelyX U100 universal selfadhesive resin luting cement
(RelyXTM U100, 3M ESPE, Sumar´e, SP, Brazil) and Variolink II resin luting cement (Ivoclar Vivadent,
Schann, Liechtenstein). These cements were mixed and luted on the copings. The copings were seated onto
the steel die using finger pressure for 1 minute and placed under a 2.2 kg standard load for 15 minutes. A
compressive load was applied through a 1/8-inch diameter hardened steel sphere attached to the moving
head of universal testing machine (LR 50K, Lloyds instruments, UK). Load was applied at a crosshead
speed of 0.5 mm per minute until fracture occurred.
Results: It was found that Nickel-Chromium yielded a higher fracture load compared to Zirconia and the
difference in mean fracture load between them was found to be statistically significant (P
Copings are found to be a significant factor influencing fracture load. No statistically significant difference
was observed between RelyX and Variolink II cements (P>0.05). Slightly higher mean fracture load was
recorded in Variolink II compared to RelyX.
Keyword :
Variolink II, RelyX U100, Nickel-Chromium, Zirconium dioxide.