American journal of dentistry

Ceramic bond durability and degradation mechanism of commercial gamma-methacryloxypropyl trimethoxysilane-based ceramic primers.

PMID 23082388


To investigate the bond durability and degradation mechanism of various commercial ceramic primers that are based on gamma-methacryloxypropyl trimethoxysilane (gamma-MPTS) and contain various organic additives. The null hypotheses tested were that (1) the type of ceramic primer had no effect on the bond strength after thermocycling and (2) the type of ceramic primer had no effect on the water contact angle after rinsing with THF. The adherent was a silica-based ceramic block used for computer-aided design/computer-aided manufacturing (CAD-CAM). Four commercial ceramic primers, Clearfil Mega Bond Porcelain Bonding kit (CM), Tokuso ceramic primer (TC), GC ceramic primer (CP), and Porcelain Liner M (PL), were compared with a simplified experimental ceramic primer (EP) that comprised gamma-MPTS and an inorganic acid (hydrochloric acid) but no other organic additives. The specimens for the adhesion test were prepared after a dual-curing type resin cement (Link Max) had adhered to the ceramic surfaces treated with each ceramic primer. The bonded specimens were then stored in water at 37 degrees C for 1 day. Then, the bonded specimens were thermocycled between 5 degrees C and 55 degrees C in water baths for 5000 or 10,000 cycles. The dwell time in each water bath and the transfer time were 60 and 7 seconds, respectively. The shear bond strength of resin to the ceramic surface was measured under a crosshead speed of 1.0 mm/minute by a conventional testing machine. Thereafter, the fracture mode for each specimen was determined. In addition, the water contact angle on the treated ceramic surfaces was measured before and after THF using a cotton pellet. As a control, the contact angle on the ground ceramic surface was measured without any ceramic primer. For all samples, thermocycling led to an increase in the frequency of interfacial failure, reflecting reduced mean bond strength of the resin to the treated ceramic surfaces. However, the bond degradation behavior differed among commercial ceramic primers; in particular, PL exhibited different ceramic bond durability from the others. However, the mean bond strength of PL was only 11.8 MPa and over half the specimens exhibited interfacial failure. In contrast, EP provided significantly higher mean bond strength of 17.2 MPa and most specimens exhibited cohesive failure of the ceramic. Furthermore, the contact angle measurements clearly demonstrated that the commercial ceramic primers created a multilayer consisting of gamma-MPTS species and the organic additives on the ceramic surface.