The new ceramics material (OCC) was developed for the purpose of aesthetic restration which can be fabricated by an usual lost wax process and it produces accurate marginal fit. OCC possesses mechanical, chemical, and physical properties. This article is discussed utility and security of OCC complete crown on the clinical application from Dec, 1986 to Jun, 1989. The results may be summarized as follows: 1) 2 of 69 cases were broken down in the period from Dec, 1986 to Jun, 1989. These reasons are caused by the lack of occlusal thickness and unsuitable fit of crown. 2) Although 4 of 69 cases are stained by tobacco tar and 5 of 69 cases are suffered from plaque accumulation, these staining and plaque accumulation are improved by plaque control. 3) An allergic reaction or an abnormality of oral tissues haven't been recognized during test period of clinical use. Consequently OCC crown showed itself about safety and usefulness.