Marginal and flexural integrity of three classes of luting cement, with early finishing and water storage

Objectives. The aims of this investigation were to clarify the effects of finishing-time and 24 h water-storage on mechanical properties and marginal adaptation to dentin of seven modern luting cements, representing three chemical types. Methods. Bistite II, Chemiace II, Compolute, XenoCem, PermaCem, Fuji Cem and Fuji Plus were investigated with specimen sub-groups (N=10) for each property measured. The principal series of experiments was conducted in dentin cavities with interfacial polishing either immediately (3 min) after setting or after 24 h water-storage. After the finishing procedure, the maximum marginal gap width and the opposing width (if any) per cavity were measured microscopically, and summed. Then the overall sum of gap-widths (per group; N=10) was calculated. Marginal gaps were similarly measured in Teflon cavities, together with shear-bond-strengths to dentin and early flexural strengths, moduli and swelling data. Results. For specimen-sets polished immediately after setting, summed marginal gaps of 23-121 μm were observed, for all luting cements except Compolute. A significantly different (p<0.05) result of either no gap or 6-28 μm summed gap-widths occurred in specimens polished after 24 h. For all materials, their shear-bond-strengths, flexural strength and moduli significantly increased after 24 h storage. Significance. The marginal behavior can be interpreted in terms of the contributions of bonding, shrinkage, swelling and compliance of components, along with compositional features of the cements. With these types of cement it is generally inadvisable to polish the interfacial luting surface immediately after cementing. The polishing procedures should be carried out not less than 24 h later. One resin-cement was able to withstand immediate finishing.