Influence of margin design on the fit of high-precious alloy restorations in patients

Objective It was the objective of this study, to analyze the influence of the marginal design on the marginal accuracy of a casting in a clinical setup in patients. Methods Ninety volunteer patientsʹ teeth—which were intended for extraction due to medical reasons—were prepared prior to extraction. Three different types of finishing line—chamfer, 135° shoulder and 90° shoulder—were employed. Two each c-silicone and pvs impressions were taken of each tooth using either a two-stage or a one-stage putty-wash technique. After preparation and impression taking the teeth were extracted. Gypsum casts were poured from the impressions and high precious alloy castings fabricated on the dies and marginal discrepancies were determined on the extracted teeth. Results The median value of marginal discrepancies was lower than 150 μm for all groups. The difference between the three different preparation types was significant (H-test, p<0.05). The lowest median values were obtained for the chamfer preparations, while the 90° shoulders always produced the highest median values. Preparations at gingva level exhibited more accurate marginal fit than subgingival preparations. No significant differences could be observed between the pvs and c-silicone materials or the one-step and two-step putty-wash techniques. Conclusions The marginal designs of the preparations had much less influence on the marginal fit of high precious alloy castings than expected. There is considerable reason to assume that technical but clinical parameters influence the quality of fixed prosthodontics much more than has been believed in the past.