Marginal adaptation of three-unit fixed partial dentures constructed from pressed ceramic systems

Purpose This study compares the marginal accuracy of posterior metal ceramic (MC), all-ceramic IPS Empress(R) 2 and experimental pressed ceramic (EPC-VP 1989/4) three-unit fixed partial dentures (FPD), before and after luting and after thermo-mechanical fatigue in a dual-axis chewing simulator. Materials and methods Caries-free human teeth (n=160) were used as abutments for the fabrication of eighty posterior three-unit FPD, divided into two test-groups, IPS Empress(R) 2 and EPC, of 32 samples each and one control group of 16 samples metal ceramic FPD. All FPD were cemented with Variolink(R) II dual-curing resin cement. Half of the samples in each group were exposed to a dual-axis chewing simulator. Results The geometric mean marginal gap values (mum, before cementation, after cementation and after thermo-mechanical fatigue) amounted to 53, 63 and 62 for the ceramic metal FPD, 57, 71 and 68 for the Empress(R) 2 FPD and 55, 67 and 68 for the EPC FPD. In all groups a statistically significant increase in marginal gap width was observed after cementation. The effect of functional loading in the chewing simulator on marginal gap was not significant. Marginal gap was lowest in the control group but differences with all-ceramic materials were small in all evaluation stages. Conclusion Within the limits of this investigation, it can be concluded that marginal gap values of these all-ceramic materials and conventional MC techniques are on a similar level. In particular, almost all marginal gap values observed in this study were within the limits of clinical acceptance.