A two-year clinical study of metal-ceramic and metal-polymer crowns

The purpose of this study was to compare full metal crowns with two different types of veneering material - ceramics and polymer after a two-year period in a function. The aim was to evaluate the changes of occlusal relief, marginal adaptation, break of material, changes of shape and color and gingival status. One hundred and two crowns were examined in 34 patients immediately after cementation, and they were reviewed within two years of crown placement. These fixed restorations were checked according two modified US Public Health Service System criteria. After two years the crowns were found clinically intact in 94% for metal-ceramics versus 98% for metal-polymer. No crown was lost. There were found significant differences in positions of a crown margin between both materials and marginal adaptation between initial (baseline) and follow-up results. Gingival health at baseline was related in optimal in 67% versus 77%, after two years in 43% versus 71%. Slight mismatch in color occurred in 0 versus 60% crowns, obvious mismatch was apparent in 0 versus 21% crowns after two years. Within the limitations of this study, it was found that the examined metal crowns with two different veneerings are very stable fixed restorations, mechanical resistance and integrity of polymer material was surprisingly good but its color stability presented mismatch after two-years period. Ceramic veneering was excellent in color match but there were three visible cracks of the ceramic layer.