Microtensile bond strength testing of luting cements to prefabricated CAD/CAM ceramic and composite blocks.
OBJECTIVE
To investigate the Microtensile bond strength (microTBS) and failure mode of resin cements bonded to composite and ceramic CAD/CAM blocks following various surface treatments.


METHODS
Paradigm composite blocks and Cerec Vitablocs received three surface treatments following the control treatment of surface grinding with 600 SiC grit. (1) Application of adhesive resin (Adh), (2) etching with hydrofluoric acid and silanization (HF+S) or (3) combination of the previous two treatments (HF+S+Adh). Three resin cements (Tetric Flow, Nexus 2, RelyX ARC) were applied to these surfaces and built-up in layers. After 24 h water storage at 37 degrees C, the non-trimming version of microTBS test was used to produce 1 mm(2) microbars. The Microbars were subjected to a tensile load using a modified testing device. The broken specimens were examined with a stereomicroscope and SEM to determine the failure mode.


RESULTS
All control and adhesive treated groups of the ceramic substrate showed premature debonding during cutting. The overall mean microTBS for the three resin cements bonded to ceramic following HF+S and HF+S+Adh surface treatment, was 27 and 29.2 MPa and for the resin cements bonded to composite substrate was 42.3 and 54.2 MPa, respectively. The mode of failure was 98% adhesive with composite as a substrate and 68% mixed failures with ceramic as a substrate.


CONCLUSIONS
CAD/CAM restorations fabricated from processed composite blocks may have advantage over the ceramic blocks with regard to the higher bond strength with resin cements.
El Zohairy
Ahmed A
AA
Department of Dental Materials Science, Academic Center for Dentistry Amsterdam (ACTA), Louwesweg 1, 1066 EA Amsterdam, The Netherlands. a.el-zohairy@acta.nl
De Gee
Anton J
AJ
Mohsen
Mohamed M
MM
Feilzer
Albert J
AJ
D000269:Adhesives; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D017076:Computer-Aided Design; D001840:Dental Bonding; D045662:Dental Etching; D003775:Dental Polishing; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D008422:Materials Testing; D011092:Polyethylene Glycols; D011109:Polymethacrylic Acids; D019279:Resin Cements; D013499:Surface Properties; D013718:Tensile Strength
D000269:Adhesives; D003188:Composite Resins; C433206:Nexus; D011109:Polymethacrylic Acids; C462240:RelyX ARC; D019279:Resin Cements; C452226:tetric flow composite resin; D003776:Dental Porcelain; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate