Effects of Taper, Cement Space and Consistency of Luting Agents on the Fitness of Crowns Fabricated with a Dental CAD/CAM

Abstract

Purpose: The effects of the consistency of luting agents, axial wall taper of abutment tooth and cement space between crown and tooth on the fitness of the crown after luting were assessed. Crowns were fabricated with a dental CAD/CAM.
Materials and Methods: 2, 7 and 12 degrees were used as convergence angle of the axial wall. With the 12 degree taper, the cement space setting was 0 μm; with the 2 and 7 degree tapers, the cement space setting was 0, 60, and 120μm. All full-veneer crowns were fabricated with a dental CAD/CAM. Three types of seating agent in different consistencies were used; they included zinc phosphate and adhesive resin cements. After luting the crown and setting the seating agent, the gap between the crown and the die was measured on the vertical cross section under each condition.
Results: The gap increased as the taper diminished. The gap was on average 175 μm at the margin position with the 2 degree taper with a low-consistency luting agent, which is quite a large value. With the 12 degree taper, the gap in the marginal position after seating with each luting agent was on average 16 μm, and there was no significant difference among the various luting agents. With the 2 degree taper and 60μm space using the zinc-phosphate cement, the gap at the marginal position was 70 μm, which was larger. Furthermore, with the 120 μm space, the gap distance with all luting agents was on average 7 μm, and there was no significant difference among the luting agents.
Conclusion: 1) The marginal elevations in a full-veneer crown increased as the taper decreased and the consistency of the luting agent increased. 2) With the 12 degree taper, the marginal adaptation of crowns was good with each luting agent. 3) The addition of a cement space resulted in good marginal adaptation.