Influence of the Color of Adhesive Resin Cement and Type of Foundation Restoration on the Color of CAD/CAM Resin Crowns

This study aimed to investigate whether the type of resin cement influences the effect of the cast post-and-core on computer-aided design/computer-aided manufacturing (CAD/CAM) resin crown color. Sixteen artificial teeth of the left mandibular second premolars were prepared for post-space preparation. The specimens were divided into two groups : half had a composite resin core with a glass-fiber post, and the other half had a cast post-and-core with a gold-silver-palladium alloy. The CAD/CAM crowns were pressed onto the abutment tooth using two types of try-in paste (universal and opaque). The surface color of the crowns (occlusal side and central and cervical areas) was assessed using a dental spectrophotometer. Three groups were investigated : a group using the try-in paste (universal) for the resin core (resin＋universal group : RU) as the control, a group using the try-in paste (universal) for the cast post-and-core (metal＋universal group : MU), and a group using the try-in paste (opaque) (metal＋opaque group : MO). CIELAB color coordinates (L＊a＊b＊) and color difference (ΔE) from the control group were used for color measurement analysis. Significant differences were observed in L＊ and b＊ between the MU and other groups and a＊ between the control and the two metal groups. ΔE was significantly higher in the MU group than in the MO group. When metal is used for foundation restoration, opaque resin cement is considered clinically useful because of its masking effect on metal color.