The purpose of this study is to compare three different core build-up materials for dental use. The study hypothesis is that there is no differences in survival rate of the different core build-ups.

Core build-ups replace dental structures which are decayed through caries or tooth fractures. Often there are necessary before insertion of dental restorations. In clinical practice, there are two main material groups: glass ionomer cements and composites. Because of there good physical properties the composite materials claimed to fulfill the expected criteria of core build-ups. However, some of these composite core build-ups get lost before insertion of definite prosthetic restorations. The current prospective, randomized controlled study should investigate the survival rate of three different composite materials: "Rebilda DC", "Clearfil Core DC / Plus" and "Multicore Flow". The statistical analysis will performed with logistic regression performed by the institute of institute of Medical Biometry and Informatics, university of heidelberg. The study hypothesis is that there is no differences in the survival rate.

Inclusion Criteria:

• patients need a single crown or fixed dental prostheses
• patients are able to signed inform consent form, more than 18 years,

Exclusion Criteria:

• no pregnant women
• insufficient oral hygiene

Patients of the department of porsthodontics, university of heidelberg