RESUMO
Recently as the esthetic concerns about dental prosthesis have been increased, the nonmetallic post and core systems have been introduced clinically to improve the color and the low optical transmittance of conventional casting metal post and core systems. The purpose of this study was to compare and analyze the optical transmittance and the shade changes of all-ceramic crowns with two nonmetallic post and core systems. The experimental groups were classified as follows: Total 27 specimens(9 samples in each group) were evaluated. Group I: Natural teeth as a control group. Group II: CosmoPost and Empress(R) core (Ivoclar-Vivadent, Liechtenstein). Group III: LIGHT-POST(TM) and LIGHT-CORE(TM)(Bisco, U.S.A.). In all groups, all-ceramic crowns were fabricated with the same shade of IPS Empress(R)II(Ivoclar-Vivadent, Liechtenstein) after abutment preparation, and then two kinds of spectrophotometers, UV 3101 PC(Shimadzu,Japan) and CM 503i(Minolta Co., Ltd., Japan), were used to measure the optical transmittance and the color value. The following results were obtained: 1. The optical transmittance of each group without all-ceramic crowns, was siginificantly decreased in order of Group III, I and II(p<0.05). 2. The optical transmittance of each group with all-ceramic crowns cemented, were siginificantly decreased in order of Group I, II and III(p<0.05). 3. In comparison with the shade of all-ceramic crowns, there were no significant differences between groups regardless of the cementation. 4. In comparison with the shade changes in each group after the cementation of all-ceramic crowns, there were no significant differences between groups. From the above results, it is thought that the selection among materials used in this study doesn't influence greatly the esthetic restoration, because the differences of optical transmittance were so small that those were clinically insignificant.