Marginal accuracy of different CAD/CAM monolithic crowns cemented on implant abutments

Purpose: The aim of this study was to evaluate the marginal adaptation of four monolithic CAD/CAM all-ceramic crowns cemented on implant abutments after fatigue loading.
Materials and methods: A lower right first molar was designed in CAD/CAM software and twenty crowns were machine milled using four different monolithic ceramic blocks (n=5): Group I: Vita Enamic (V.enamic), GroupII: IPS E-max CAD(e.max), GroupIII: Celtra Duo(CD), GroupIV: Functional explore (f.explore). The crowns were fabricated using CAD/CAM system. All crowns were cemented on implant abutments using self adhesive resin cement. Vertical margin gap distance of all crowns was measured using a digital microscope. All the samples were subjected to fatigue cyclic loading for 75.000 cycles. The vertical marginal gap distance for all samples were subsequently remeasured after the fatigue loading testing. Data were collected, tabulated and statistically analyzed.
Results: The highest marginal gap mean value was for CD group followed by f. Explore group then V. Enamic group while the lowest marginal gap mean value was recorded with e.max group and this was statistically significant between the groups (P=0.0013< 0.05). The total marginal gap mean values with all types of ceramics were higher after aging than before with significant difference (P=<0.0001< 0.05).
Conclusions: all-ceramic crown materials that are used for chair-side CAD/CAM systems demonstrated clinically acceptable marginal adaptations. V. Enamic and LD provided better marginal fit than CD and f.explore zirconia. Fatigue loading had a detrimental influence in the vertical marginal gap distance for all ceramic types except f.explore zirconia.