Aspects of adhesion between CAD/CAM ceramics and resin cements

Abstract

Glass ceramics are one of the preferred choices in the case for preservation of tooth structure. They also exhibit excellent aesthetic outcomes, and life-like translucency. Moreover, glass ceramics can provide better adhesion to the underlying tooth preparation, compared with metal-bonded ceramics and oxide ceramics. This is achieved by application of HF etching and silanization, followed by bonding with resin cement. The resin cement is applied as the means to provide a seal, adhesion and ‘filler’ in the small space that exists between a restoration and prepared tooth. These unique properties have given rise to expanded restoration designs for glass ceramics in comparison to other ceramics, e.g., veneers, inlays or onlays. Hence, durable and stable adhesion is strongly required for the long-term success of these restorations.

The aim of this project was to evaluate the durability of adhesion between CAD/CAM ceramics and resin cements as well as the effect of different factors on long-term ceramic adhesion.

In the first experiment, two bonding models were compared and contrasted using a microtensile bond strength test. Two surface treatments and two resin cements were also examined. Ceramic to ceramic, as a bonding model, was found to be better than a ceramic to resin composite model. Surface treatments and resin cements had a significant effect on the microtensile bond strength.

The second experiment aimed to evaluate the stability of long-term adhesion using six resin luting cements when bonded to three different CAD/CAM ceramics in water over 12 months. According to the outcomes of this study, VITA Suprinity® and VITA Enamic® demonstrated better long-term adhesion compared to IPS e.max® CAD. Furthermore, the microtensile bond strengths of ceramic and resin cement decreased up to 3 months but thereafter became relatively stable. Different resin cements showed different bonding behaviour during prolonged storage time.

The third study examined the effect of two etching times on long-term ceramic adhesion and the effect of six resin luting cements on durability of adhesion. This study indicated that prolonged etching time could increase the microtensile bond strength of glass ceramics in the short-term, however, different etching times did not have an obvious influence on the long-term adhesion.

In the fourth experiment, an evaluation of sorption, solubility and dimensional change of six resin luting cements immersed in various storage media was undertaken. Significant differences were observed in the sorption, solubility and dimensional change of the cements when exposed to the different storage media over time.

The objective of the last experiment was to evaluate the effect of immersion time and media on fracture toughness of six resin cements. It was concluded that fracture toughness varied among the cements and the value decreased over time.

Furthermore, the three storage media evaluated in this study seemed to not have had a significant effect on the fracture toughness.

It was concluded that, in general, lower sorption, solubility and dimensional change in resin cements seems to produce a higher fracture toughness and microtensile bond strength to glass ceramics.