Marginal adaptation of lithium disilicate ceramic crowns cemented with three different resin cements.

OBJECTIVES: The cementation process and cementation materials have an influence on the marginal adaptation of restorations. The gap could be affected by thermal and mechanical loading (TCML). The computerized x-ray microtomography (muCT) method offers the possibility of measuring the marginal gap without destruction of the restoration. The aim of this study was to evaluate the marginal gap (MG) and the absolute marginal discrepancy (AMD) before and after TCML. MATERIALS AND METHODS: Thirty-nine human premolars were prepared for full ceramic crowns made of lithium disilicate. The crowns were cemented by three different resins-Panavia F 2.0, Variolink II, and Relyx Unicem. The MG and AMD were evaluated by muCT before and after TCML. RESULTS: Panavia F 2.0 had the lowest MG (before 118 mum-after TMCL 124 mum) and AMD (before 145 mum-after TMCL 154 mum), followed by Relyx Unicem (MG: before 164 mum-after TCML 155 mum; AMD: before 213 mum-after TMCL 209 mum) and Variolink II (MG: before 317 mum-after TMCL 320 mum; AMD: before 412 mum-after TMCL 406 mum). The differences were statistically significant before and after TCML. Rather than TCML, it appeared the resin cement was responsible for differences between the MG and AMD before and after TCML. CONCLUSIONS: muCT is an accurate technique for assessing cemented restorations. Panavia F 2.0 has the lowest MG and AMD before and after TCML. CLINICAL RELEVANCE: The resin material that features a three-step protocol (Variolink II) produced higher MG and AMG values than the Panavia or Relyx Unicem varieties with less or no intermediate steps at all.