[Study on improvement of adaptation for inlay made by dental CAD/CAM CEREC 2 system]

The purpose of this study was to evaluate the effect of changes in the tapering angle of inlay casting, adhesive gap and cavosurface margin on the cavity wall adaptability of the inlay made by the dental CAD/CAM CEREC 2 system. Designed inlay castings were fabricated at three different tapering angles: 0, 3, and 6 degrees. Adhesive gap of 0, -50, -100 microns and adhesive gap of 0 micron combined with the adjustment of cavosurface margin at 2 and 4 pixels were also evaluated. The difference between the direct method with powder and the indirect method without powder were compared under all conditions. The gap between the castings and cavity walls were assessed under a telescopic microscope. Internal adaptation of castings was determined to measure the cement thickness on the surfaces sectioned in the central portion of the cavity. It was found that inlays fabricated at 3 or 6 degree taper exhibited less gap at the side wall of the cavity than those without taper. The indirect method without powder also showed less gap when compared with the direct method with powder. Marginal gap and the cement width at the side wall of the cavity were reduced when the adhesive gap was modified to -50 or -100 microns or the cavosurface margin was adjusted at 2 or 4 pixels in the outer margin. The results suggested that the indirect method with the taper of 3 or 6 degrees of inlay casting, or with adjustment of adhesive gap to -50 microns provided the best adaptability between the castings and cavity walls.