This stdy made an in vitro comparison of the shear strength in a corrosive solution, the scanning electron microscopy of the processing steps, and the x-ray powder diffraction analyses of a newly developed opaque system (Biopaque) with a traditional opaque-system (Opaque P). Clinically, two traditional opaque systems (Opaque P and Vita-VMK-Paint-On 88 opaque) were compared to Biopaque over a 4 year period. A total of 218 metal ceramic units were placed for 29 patients. One hunded ten were veneered with Biopaque, 50 with Opaque P, and 58 with Vita-VMK-Paint-On 88. The technical failure rate of the metal ceramic restorations was 9.6%, and the biological failure rate 5.5%. There was no significant difference of the shear strength in a corrosive solution between Biopaque and the traditional opaque system (Opaque). The x-ray powder diffraction analyses revealed that only the base paste of Biopaque was a newly developed material. In this study, the new opaque system (Biopaque) showed the same in vitro and in vivo results as the other conventional opaque systems. However, at least 5 years of clinical evaluation are necessary before this new opaque system can be completely recommended.