Effect of two self-adhesive cements on marginal adaptation and strength of esthetic ceramic CAD/CAM molar crowns.
OBJECTIVE
This study evaluated the effects of adhesive cements on marginal adaptation and fracture resistance of ceramic molar crowns.


METHODS
Seventy-five extracted maxillary molars were selected. The occlusal morphology of 15 molars (control) was scanned and transferred to the crowns in the test groups by CAD/CAM. Sixty molars received full-coverage crown preparations with 6-degree axial taper, 1.0-mm shoulder, and 2.0-mm occlusal reduction. They were assigned to four groups, and pulpal pressure was simulated. The 15 crowns in each test group were seated with resin-based self-adhesive cements, Rely-X (RX) and Multilink (MS), one multistep bonded adhesive luting composite resin, Variolink (VL), and glass-ionomer cement, Ketac Cem (KC). Test and control molars were subjected to thermal and mechanical fatigue stress (TMS: 12,000 x 5 degrees C to 50 degrees C; 2.4 million x 49 N) for 18 days in a masticator. Marginal adaptation ["continuous margin%" (CM%)] of the crowns was determined by scanning electron microscopy (200x). Finally, molars were occlusally loaded until fracture in a testing machine, and fracture load (N) was recorded. Marginal adaptation and strength data were statistically analyzed.


RESULTS
TMS significantly (p < 0.001) reduced CM% in all groups. After TMS, CM% at the cement-dentin interface was significantly (p < 0.001) higher for RX than for all other cements. At the crown-cement interface both self-adhesive cements MS and RX had significantly better CM% than VL (p < 0.05) and KC (p < 0.001). Fracture resistance of natural untreated molars was significantly (p < 0.001) higher than that of experimental crowns. Fracture resistance of RX cemented crowns was significantly (p < 0.05) higher than that of other crowns. Occlusal morphology significantly influenced fracture resistance (p < 0.05).


CONCLUSIONS
Self-adhesive cement RX offers a valid alternative to multistep resin-based luting composite with respect to marginal adaptation to dentin and fracture resistance. The latter is also influenced by occlusal morphology, necessitating careful monitoring of occlusal contacts.
Division of Computer Restorations, Department of Preventive Dentistry, Periodontology and Cariology, Center for Dental and Oral Medicine, University of Zurich, Switzerland. werner.moermann@zzmk.uzh.ch
Werner
W
Mörmann
Daniel
D
Wolf
Andreas
A
Ender
Andreas
A
Bindl
Till
T
Göhring
Thomas
T
Attin
D003442:Crowns; D001840:Dental Bonding / Q000379:methods*; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents; D006801:Humans; D008277:Magnesium Oxide; D011076:Polycarboxylate Cement; D019279:Resin Cements; D013314:Stress, Mechanical; D015034:Zinc Oxide
D017220:Dentin-Bonding Agents; D011076:Polycarboxylate Cement; C528569:Rely-X; D019279:Resin Cements; C502351:multilink adhesive system; C103502:Variolink; D008277:Magnesium Oxide; C040235:Ketac-cem; D015034:Zinc Oxide