Tensile bond strength of ceramic crowns to dentin using resin cements.
OBJECTIVE
This study measured the bond strength of the self-adhesive resin cements and a bonded resin cement for crowns bonded to extracted teeth with preparations having a total taper greater than 30 degrees. A crown pull-off test was used with direction of pull along the path of insertion. The CAD/CAM system Cerec was used to create crowns with the pull-off loop as an integral part of the crown structure.


METHODS
One hundred extracted human molars were prepared for all-ceramic crowns with a 1.5-mm shoulder, greater than 30-degree axial wall convergence, a flat occlusal surface and 3 to 5 mm occlusal/ gingival height. All-ceramic crowns were cemented with five different self-adhesive cements (Rely X Unicem, Maxcem Elite, BisCem, SmartCem 2, and G-Cem) and one bonded resin cement (Multilink). Forfour cements (excluding GCem and Multilink) there were 2 groups, one with HF etching and one without ceramic surface treatment. The crowns were then subject to tensile stress until either the crown fractured or the crown was lifted off from the tooth.


RESULTS
For several cements, the bond strength exceeded the tensile strength of the all-ceramic crown; thus, the crown fractured, leaving the cemented part of the crown on the tooth. The effect of ceramic surface etching was not statistically significant at p = 0.05; however, for each cement, the treated crowns showed a lower coefficient of variance (COV). For this study, the COV ranged from 24.9 % to 97.9 %. Loads ranged from 41.3 to 190.3 N.


CONCLUSIONS
Some of the new self-etching resin cements can create bonds to non-retentive crown preparations that are stronger than the strength of a ceramic crown; however, these high bond strengths may not be able to be achieved consistently.
Department of Restorative Dentistry, University of Tennessee College of Dentistry, Memphis, 38163,USA. jsimon2@uthsc.edu
James F
JF
Simon
Waldemar G
WG
de Rijk
Jennifer
J
Hill
Nathaniel
N
Hill
D000134:Acid Etching, Dental / Q000379:methods; D003188:Composite Resins / Q000737:chemistry; D017076:Computer-Aided Design; D003442:Crowns; D001840:Dental Bonding; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000648:ultrastructure*; D006801:Humans; D006858:Hydrofluoric Acid / Q000737:chemistry; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D019231:Tooth Preparation, Prosthodontic / Q000145:classification
C542562:BisCem cement; D003188:Composite Resins; C528107:G-Cem resin cement; C515955:Maxcem; C483701:Rely X Unicem; D019279:Resin Cements; C502351:multilink adhesive system; D003776:Dental Porcelain; D006858:Hydrofluoric Acid