Compressive Failure of All-Ceramic Crowns Luted with Four Different Cements

Objectives: to determine the mode and mean loads of failure of teeth restored with All-Ceramic Crowns (ACC's) cemented with dual-cured self-adhesive resin (DSAR), dual-cured (DC) or light-cured (LC) composite resin, or resin-modified glass ionomer (RMGI) luting cements following longterm storage in water. Method: Forty sound, extracted, human, premolar teeth underwent a standardised preparation for ACC's. IPS Empress I (Ivoclar Vivadent, Liechtenstein) crowns of standard dimensions were fabricated and cemented as per manufacturer's instructions, with ten in each cement group and stored for 10 mth in water at 22 0C. Each specimen was thermocycled (5 - 55 0C, 15s dwell, 2000 cycles in total) and subjected to compressive load to failure at a crosshead speed of 0.017 mm/sec. The mode of failure was classified I-V where I=minimal fracture or crack in crown; II=less than half of crown lost; III=crown fracture through midline; IV=more than half of crown lost; V=severe fracture of crown and/or tooth. Results: mean loads at failure N (+/- s.d.): DSAR=747.3 (265.6); DC=730.7 (167.6); LC=689.4 (202.9); RMGI=511.2 (172.6) (p<0.05). The percentage of ACC's failing in Modes I-V were: DSAR I=0, II=10, III=0, IV=0, V=90; DC I=10, II=20, III=0, IV=0, V=70; LC I=0, II=40, III=20, IV=0, V=40; RMGI I=0, II=50, III=30, IV=0, V=20. Conclusions: Crowns with Mode V failure had catastrophic fracture of the dentine and would render the tooth very difficult to restore. RMGI=RelyX Luting Plus, 3M ESPE; DSAR=RelyX Unicem, 3M ESPE; DC=RelyX ARC, 3M ESPE; LC=RelyX Veneer, 3M ESPE. Study sponsored by 3M ESPE.