The effects of crown venting or pre-cementing of CAD/CAM-constructed all-ceramic crowns luted on YTZ implants on marginal cement excess.

The purpose of this study was to analyze the cement excess produced when cementing CAD/CAM-fabricated lithium disilicate (L) or zirconium dioxide (Z) crowns using adhesive cement (A) or resin-modified glass ionomer cement (B). Three different cementation techniques were applied: palatal venting (PV), pre-cementation with custom analogs (CA), and conventional standard procedure (SP). Seventy-two crowns (36 each material) were assigned to 12 experimental groups depending on the restoration material (L, Z), type of cement (A, B), and cementation technique (PV, CA, SP). Weight measurements were taken during cementation, and the amounts of excess cement, cement retained in crown, and relative excess cement were calculated and statistically analyzed. A significant direct relation between the amounts of cement applied and excess cement was observed in groups CA and SP. Vented crowns showed least amounts of marginal excess cement (0.8 ± 0.3 μl) followed by CA (4.2 ± 1.1 μl) and SP (8.8 ± 2.5 μl; p < .001). In CA, 32.1% less excess cement (95%CI: 28.4, 35.7) was produced than in the SP group (p < .001), but 27.4% more than in the PV group (95%CI: 23.8,31.0; p < .001). Overall, slightly smaller amounts of adhesive cement (A) than of glass ionomer cement (B) were retained in crowns. Using crown venting was the most effective measure to reduce the amount of marginal excess cement, followed using a pre-cementation device. To keep the marginal excess cement of one-piece zirconia implants to a minimum, both techniques should be considered for clinical application.