The impact of luting agents and stiffness of implant-abutments on marginal adaptation, chipping, and fracture resistance of zirconia crowns.

OBJECTIVES: This in vitro study evaluated the impact of cements and implant analogs with different e-moduli on marginal adaptation, chipping, and the fracture resistance of zirconia crowns.

METHODS: 80 crowns (Cercon, DeguDent) were manufactured for 40 polyoxymethylene (POM) and 40 titanium (Ti) one-piece implant analogs and divided into 10 groups: A, zinc oxide phosphate (Hoffmann׳s Cement, Richter&Hoffmann, Berlin, D); B, zinc oxide eugenol (Temp Bond, KerrHawe, Bioggio, CH); C, resin (Variolink II, Ivoclar-Vivadent, Schaan, FL); D, zinc oxide without eugenol (Temp Bond NE, KerrHawe, Bioggio, CH); E, glass ionomer (Ketac Cem, 3M ESPE, Seefeld, D). All samples were thermally mechanically loaded (1.2 × 10(6)× 50 N; 3000 × 5°C/55°C). Marginal adaptation was semiquantitatively evaluated before and after ageing with a scanning electron microscope. After ageing, intact samples underwent a fracture resistance test.

RESULTS: The best sealed margins before ageing were achieved with resin and zinc oxide cement and with resin after ageing. Zinc oxide samples showed the most discontinuously sealed margins after ageing and the difference between POM and Ti samples was significant only for zinc oxide. The numbers of samples failing during TCML were as follows: A(Ti - POM)=0-1; B(Ti - POM)=0-5; C(Ti - POM)=1/1; D(Ti - POM)=2-2; E (Ti - POM)=0-2. Fracture resistance test [N]: A(Ti - POM)=1181-801; B(Ti - POM)=1469-1517; C(Ti - POM)=1704-1408; D(Ti - POM)=1992-883; E (Ti - POM)=2750-1015.

CONCLUSIONS: TCML reduced the number of perfectly sealed samples and increased the number of chipped samples cemented onto POM implants with zinc oxide. This study could not show any significant impact on the fracture resistance of zirconia when different cements and implant analogs were used.