Fracture strength of four different types of anterior 3-unit bridges afterthermo-mechanical fatigue in the dual-axis chewing simulator

The purpose of this study was to evaluate the fracture strength of four dif ferent types of anterior 3-unit bridges after thermo-mechanical fatigue in a dual-axis chewing simulator. Sixty-four human maxillary incisors were pre pared and 32 bridges fabricated. The four groups of eight bridges each were - (GC): AGC(R) galvano-ceramic bridges (CA): Celay(R) In-Ceram(R) Alumina bridges (E2): heat-pressed lithium disilicate glass-ceramic bridges and (CM ) ceramo-metal (control). Fracture loads were recorded after a dual-axis ch ewing simulator and in a universal testing machine. The survival rate after 5 years for the CM and the GC groups was 100%, for the E2 group 75% and fo r the CA group 37.5% (Kaplan-Mayer analysis). The mean fracture strengths ( N) were 681.52 +/- 151.90 (CM); 397.71 +/- 59.02 (GC); 292.92 +/- 46.45 (E2 ) and 239.95 +/- 33.39 (CA), respectively. The log-rank test showed a signi ficant difference between the CA and the GC or the CA and the CM groups. No significant differences between the E2 and the CA or the E2 and the GC gro ups were found. The study indicates that heat-pressed lithium disilicate gl ass-ceramic and AGC(R) galvano-ceramic bridges are alternatives to ceramo-m etal 3-unit anterior bridges.