Abstract
The aim of this is was evaluate the vertical and horizontal marginal adaptation of 3-unit fixed partial denture frameworks fabricated using different techniques and CAD/CAM systems. A total of 40 framework specimens were fabricated and divided into four groups as follows: lost-wax casting (G1); lost-wax casting with welding (G2); extraoral optical scanning of models (3S/DWOS) (G3); intraoral optical scanning (Cerec Bluecam/Sirona) (G4). A reference model was used to simulate a fixed partial denture with three elements (with a central pontic). The frameworks of G1 and G2 were cast in nickel-chromium (NiCr) alloy, whereas those of G3 and G4 were milled in zirconia. In all groups, vertical and horizontal marginal adaptation (over-contour and under-contour) was evaluated using a three-dimensional optical microscope (Quick Scope, Mitutoyo). The results showed higher vertical marginal misfit in G1 than in the other groups (p<0.001). Regarding horizontal marginal misfit, higher over-contour values occurred in G3 than in the other groups (p<0.001). G3 did not show under-contour at all, whereas the other groups did not differ from each other in this regard (p>0.05). Within the limitations of this study, it can be concluded that lost-wax casting with welding is a viable alternative to the use of CAD/CAM systems to fabricate frameworks of three-unit FPDs, since the techniques yielded similar vertical misfit values. Extra-oral CAD/CAM systems showed the highest horizontal misfit (over-contour) compared to other groups.
Highlights
The marginal misfit of fixed partial dentures (FPDs) corresponds to the marginal gap between the edge of the prosthetic restoration and the limit of the tooth preparation [1]
The specific correlation test (r) showed an agreement of r=0.98 for the vertical marginal misfit, in the systematic error no difference observed between the samples in the analyzed periods, the random error test (Dahlberg) ± 10 μm
In the vertical marginal analysis, highest vertical misfit was observed for G1, being significantly different to other groups (p
Summary
The marginal misfit of fixed partial dentures (FPDs) corresponds to the marginal gap between the edge of the prosthetic restoration and the limit of the tooth preparation [1]. Marginal misfit contributes to cement exposure in the oral environment, with the possibility of dissolution, plaque accumulation [2], and secondary caries. These effects compromise both the longevity of the prosthesis and periodontal health [2]. The lost-wax casting technique was considered the gold standard in dentistry in the 20th century [4]. Some authors have recommended minimizing these distortions in FPDs by welding the framework joints. This can improve the fit and passivity of prostheses [7]. In a systematic review, Abduo et al [8] reported that welding the frameworks corrects the discrepancies yielded by the lost-wax casting technique
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