Objective To evaluate the effect of different root canal irrigants and cements on coronal microleakage and the interaction effects after cementing metal post-cores.Methods Ninety newly extracted single-rooted mandibular human premolars were endodontically treated. Post spaces were prepared in the root canals, and Co-Cr post-cores were cast routinely. The specimens were randomly divided into six groups (n=15) via a two-way factorial design method. The irrigant factors (A) included A1: no irrigant (75% alcohol wiping), A2: 3% H2O2+0.9% NaCl, and A3: 15% ethylenediamine tetraacetic acid (EDTA)+5.25% NaClO. The cement factors (B) included B1: zinc polycarboxylate cement, and B2: glass ionomer cement. The specimens received treatments based on the grouping of A1B1, A1B2, A2B1, A2B2, A3B1, and A3B2. All samples were sectioned longitudinally after being immersed in India ink for three weeks. The microleakages were observed using a ste-reomicroscope. The SPSS 13.0 software package was used for factorial analysis.Results The mean microleakage scores and standard deviations were as follows: Group A1B1: (1 192.59±417.84) μm, Group A1B2: (1 317.38±527.35) μm, Group A2B1: (1 429.33±482.68) μm, Group A2B2: (1 026.79±459.49) μm, Group A3B1: (1 448.29±561.02) μm, and Group A3B2: (1 922.47±678.86) μm. The A2B2 group showed minimum microleakage, whereas the A3B2 group showed maximum microleakage. The microleakage degrees among different irrigants presented significant statistical difference (P0.05). An interactive effect on the microleakage existed between the irrigants and the cements after cementing the metal post-cores (PConclusion When cementing metal post-cores, the coronal microleakage following 3% H2O2+0.9% NaCl irrigation combined with glass ionomer cement can be reduced. The combined application of 15% EDTA+5.25% NaClO and glass ionomer cement significantly aggravates microleakage.
