Vertical misfit of laser-sintered and vacuum-cast implant-supported crown copings luted with definitive and temporary luting agents

Abstract

Objectives: This study aimed to evaluate the vertical discrepancy of implant-supported crown structures constructed with vacuum-casting and Direct Metal Laser Sintering (DMLS) technologies, and luted with different cement types.

Study design: Crown copings were fabricated using: (1) direct metal laser sintered Co-Cr (LS); (2) vacuum-cast Co-Cr (CC); and (3) vacuum-cast Ti (CT). Frameworks were luted onto machined implant abutments under constant seating pressure. Each alloy group was randomly divided into 5 subgroups (n = 10 each) according to the cement system utilized: Subgroup 1 (KC) used resin-modified glass-ionomer Ketac Cem Plus; Subgroup 2 (PF) used Panavia F 2.0 dual-cure resin cement; Subgroup 3 (RXU) used RelyX Unicem 2 Automix self-adhesive dual-cure resin cement; Subgroup 4 (PIC) used acrylic/urethane-based temporary Premier Implant Cement; and Subgroup 5 (DT) used acrylic/urethane-based temporary DentoTemp cement. Vertical misfit was measured by scanning electron microscopy (SEM). Two-way ANOVA and Student-Newman-Keuls tests were run to investigate the effect of alloy/fabrication technique, and cement type on vertical misfit. The statistical significance was set at α = 0.05.

Results: The alloy/manufacturing technique and the luting cement affected the vertical discrepancy (p < 0.001). For each cement type, LS samples exhibited the best fit (p < 0.01) whereas CC and CT frames were statistically similar. Within each alloy group, PF and RXU provided comparably greater discrepancies than KC, PIC, and DT, which showed no differences.

Conclusions: Laser sintering may be an alternative to vacuum-casting of base metals to obtain passive-fitting implant-supported crown copings. The best marginal adaptation corresponded to laser sintered structures luted with glass-ionomer KC, or temporary PIC or DT cements. The highest discrepancies were recorded for Co-Cr and Ti cast frameworks bonded with PF or RXU resinous agents. All groups were within the clinically acceptable misfit range.

Figure 1

Laser sintered cobalt-chromium structure luted with DentoTemp. There is a vertical discrepancy of 27.9 µm with some washout of the temporary cement (×200; bar 300 µm).

Figure 2

Vacuum-cast cobalt-chromium specimen bonded with RelyX Unicem 2 Automix. A vertical misfit of 150 µm completely filled by the self-adhesive agent is evident (×300; bar 200 µm).

Figure 3

Vacuum-cast titanium coping bonded with Panavia F 2.0. A vertical discrepancy of 132 µm is observable. The resin cement appears almost intact at the marginal area and sparse, scattered porosities are present (×300; bar 200 µm).