Clinical examination of leucite-reinforced glass-ceramic crowns (Empress) in general practice: a retrospective study

The purpose of this study was to retrospectively evaluate leucite reinforced-glass ceramic crowns (Empress) placed in patients who regularly visit general practices.

One hundred ten Empress crowns, placed in 29 patients who visited a general practice on a regular basis, were evaluated according to the California Dental Association's (CDA) quality evaluation system. In addition, the occurrence of plaque and certain gingival conditions was evaluated. All crowns were luted with resin composite cement. The mean and median years in function for the crowns were 3.6 and 3.9 years, respectively.

Based on the CDA criteria, 92% of the 110 crowns were rated "satisfactory." Eighty-six percent were given the CDA rating "excellent" for margin integrity. Fracture was registered in 6% of the 110 crowns. Of the remaining 103 crowns, the CDA rating excellent was given to 74% for anatomic form, 86% for color, and 90% for surface. No significant differences (P > 0.05) were observed regarding fracture rates between anterior and posterior crowns. With regard to the occurrence of plaque and bleeding on probing, no significant differences (P > 0.05) were observed between the Empress crowns and the controls.

Most of the fractured crowns had been placed on molars or premolars. Although the difference between anterior and posterior teeth was not statistically significant with respect to the fracture rates obtained, the number of fractured crowns placed on posterior teeth exceeded that of those placed on anterior teeth. The difference between the fracture rates may have clinical significance, and the risk of fracture has to be taken into consideration when placing crowns on teeth that are likely to be subjected to high stress levels.