The purpose of this study is to evaluate and compare the clinical and radiographic performance of zirconia and stainless steel crowns on permanent molar

Zirconia and stainless steel crowns will be placed on at least two permanent molars, in a split mouth design. 100 patients will be included in the study. The teeth will be randomized into two groups according to the crown type.

Group 1: Zirconia crown 2: Stainless steel crown. Plaque index, gingival index, crown retention, presence of restoration failure, gingival margin extension and pulpal health of the teeth will be clinically evaluated at baseline and 1., 6., 12., 18., 24. months. The restorations will be evaluated radiographically at 6., 12. and 18. months. Intra-oral photos will be taken directly after treatment and at control appointments.

The data will be analysed statistically using Fisher's Exact Test and pearson's chi-square test; and Log-rank and the Kaplan-Meier will be used to estimate survival percentages.

Inclusion Criteria:

• Patients and parent of the patients who accept to participate and sign the informed consent
• Patients who have at least two permanent molars with caries that require crown restoration
• Patients that have good cooperation to the procedure

Exclusion Criteria:

• Patients and parent of the patients who don't accept to participate and sign the informed consent
• Teeth that doesn't have opposing permanent molars
• Patients who have bruxism or deep-bite
• Patient who are allergic to nickel