Three-year clinical evaluation of two ceramic crown systems: a preliminary study.
BACKGROUND
The clinical performance and failure mechanisms of recently introduced ceramic crown systems used to restore posterior teeth have not been adequately examined.


OBJECTIVE
The purpose of this prospective clinical study was to evaluate and compare the clinical performance of 2 new ceramic crown systems with that of metal ceramic crowns using modified United States Public Health Services (USPHS) criteria.


METHODS
Ninety posterior teeth requiring crown restorations in 48 patients were randomized into 3 equal groups (n=30) for which different crown systems were used: an experimental hot-pressed glass ceramic based on a modified lithium disilicate ceramic (IPS e.max Press), an alumina-coping-based ceramic (Procera AllCeram), and a metal ceramic (Simidur S 2 veneered with IPS Classic Porcelain). The crowns were assessed over 3 years using the modified USPHS criteria. Crowns that developed visible cracks were sectioned and removed, and the surfaces were analyzed using a scanning electron microscope (SEM). The data were analyzed using the Kruskal-Wallis nonparametric statistical test, followed by the Mann-Whitney test with Bonferroni correction (alpha=.05).


RESULTS
USPHS evaluation showed that the IPS e.max Press and metal ceramic crowns experienced fewer clinical changes than Procera AllCeram. Visible roughness, wear, and deformity were noticed in occlusal contact areas of Procera AllCeram crowns. SEM images showed well defined wear facets in both ceramic crown systems. Kruskal-Wallis tests showed a significant difference (P<.05) in Alpha scores among the 3 crown systems. Mann-Whitney tests showed significant differences among groups.


CONCLUSIONS
IPS e.max Press crowns demonstrated clinical behavior comparable to Procera AllCeram and metal ceramic crowns, but the wear resistance of this crown type was superior to the Procera AllCeram crowns, according to modified USPHS criteria.
Etman
Maged K
MK
Division of Prosthodontics, College of Dentistry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Woolford
M J
MJ
D000134:Acid Etching, Dental; D000328:Adult; D000537:Aluminum Oxide / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D003442:Crowns; D045662:Dental Etching; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain / Q000737:chemistry*; D019554:Dental Restoration Wear; D004955:Esthetics, Dental; D005500:Follow-Up Studies; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D010165:Palladium / Q000737:chemistry; D017060:Patient Satisfaction; D017680:Potassium Compounds / Q000737:chemistry; D011446:Prospective Studies; D019279:Resin Cements / Q000737:chemistry; D013499:Surface Properties; D019246:Tooth Preparation / Q000379:methods; D055815:Young Adult
C105314:AllCeram; D000538:Aluminum Silicates; D006047:Gold Alloys; C508050:IPS e.max Press; D016876:Metal Ceramic Alloys; C438843:Panavia-Fluoro; D017680:Potassium Compounds; D019279:Resin Cements; C493120:lithia disilicate; D003776:Dental Porcelain; C016447:feldspar; D010165:Palladium; C023506:Glass ceramics; D000537:Aluminum Oxide