抄録
Jacket Crowns with castable-ceramics and porcelain do not impede the natural appearance even if their margins are set up supragingivally or at the gingiva, because there is no metalic color for the conventional porcelain fused to metal crowns. Nevertheless, if the abutment teeth are stained or discolored, the margin should be set up subgingivally.
In this study, influences of the changes of the vertical positions of the cervical lines on the depth of the Finish Line was examined concerning clinical experiences of dentists, using three different artificial gingivas.
As the result, regardless of one's clinical experiences, there were tendencies of insufficiency in preparation subgingivally around the deepest part of the cervical lines, and of excess around the proximal interdentium. And when the deepest part of the cervical line is deeper, insufficiency of preparation is seen also around the Mesio and Disto-Facial Line Angle, and the operation of teeth preparations becomes more difficult. And then the cases of margin exposure of restorations on the facial side and inflammation of periodontal tissue at the proximal interdentium would have already existed at teeth preparations.
As a conclusion, it would be necessary to reconsider imperfection of teeth preparations including human errors, and to reexamine the approach through human engineering.
