A comparison of the marginal and internal fit of porcelain laminate veneers fabricated by pressing and CAD-CAM milling and cemented with 2 different resin cements

Statement of problem. The marginal and internal adaptations of porcelain laminate veneers (PLVs) are key elements in their long-term success. However, the marginal and internal fit obtained with a pressable material compared with computer-aided design and computer-aided manufacturing (CAD-CAM) needs further investigation as does the choice of cement used. Purpose. The purpose of this in vitro study was to evaluate the marginal and internal fit of PLVs fabricated using pressing and CAD-CAM milling and cemented using 2 types of composite resin cement. Materials and Methods. Twenty PLVs were fabricated from VITA PM9 pressable material, and 20 veneers were milled using VITA Blocs Mark II. Veneers were cemented to composite resin dies using either RelyX Veneer cement or Variolink-N cement. Specimens were embedded in clear resin and sectioned incisogingivally and mesiodistally. Marginal discrepancy at the incisal and cervical positions and the internal gap at 6 different locations were evaluated by using a scanning electron microscope. Two-way ANOVA followed by Tukey multiple comparisons were used to examine difference among groups (alpha=.05). Results. The cement and fabrication methods did not show any significant effect for absolute marginal gap (AMG) at the incisal edge, AMG at the cervical margin or marginal gap at the incisal edge. However, both had a significant effect on marginal gap at the cervical margin (P=.038 for the fabrication method and P=.050 for the cement used). Also, both cement and fabrication methods had a significant effect on internal gap average (P<.001). The lowest gap values were reported for veneers fabricated from VITA PM9 by using the press technique and cemented with RelyX Veneer cement. When the position of gap measurements was taken into consideration, it was the only significant factor (P<.001 for the effect of position on AMG and P<.001 for the effect of position on marginal gap). Gaps at the cervical position were significantly lower than gaps at the incisal position. Conclusions. Smaller marginal and internal discrepancies were recorded for PLVs fabricated by using the pressing technique and cemented using RelyX Veneer cement compared with milled veneers and Variolink-N cement. Larger discrepancies were present incisally than cervically.