03 June 2020

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Is it necessary to apply an adhesive layer on glass ceramics when bonding with resin-based materials?

Edoardo Mancuso

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In the era of adhesive dentistry, glass-ceramics, including feldspathic-reinforced, leucite-reinforced, and lithium disilicate reinforced materials, are widely used mainly due to their ability to be adhesively bonded to tooth structure. However, to achieve a durable adhesion of resin-based materials to glass-ceramics, a scrupulous surface treatment of the ceramics is required. Numerous research have indeed established the need for HF etching and silanization in bonding procedures involving ceramics.   Since the resin cements are viscous materials, in recent years has been discussed their capability to completely infiltrate the irregularities of the conditioned and silanized glass ceramic surface. To enhance the wettability of the surface, it has been suggested to use, prior to the application of the resin cement, an intermediate adhesive layer in order to allow a better surface infiltration. Bond strength studies on glass ceramics regarding the use of an adhesive layer in association with HF etching and a silane-coupling agent have, however, provided contradictory results.  

MATERIALS AND METHODS
A recent systematic review and meta-analysis, authored by Lara de Oliveira Nogueira and hers team, has analyzed different in vitro studies to determine whether adhesive layer application after etching and silanization influences the bond strength values of glass ceramics to resin-based materials. 5250 relevant studies published between 1987 and 2018 were identified in the review using several electronic databases.  

RESULTS
 From the titles yielded, just 15 articles met the eligibility criteria and were included into the qualitative analysis while 14 to the quantitative analysis. Non-aged specimens without an adhesive layer (n=152) presented statistically significant higher microtensile bond strength than the non-aged specimens with an adhesive layer (Mean Difference: -1.49). The statistically significant superiority of the group without an adhesive layer (n=65) compared to the group with an adhesive layer (n=65) have been shown also within the aged specimens (Mean Difference: -3.87)

CONCLUSION
Based on the findings of the above mentioned systematic review and meta-analysis, the author concludes that an adhesive layer application do not improve the bond strength of etched and silanized glass ceramics to resin-based materials.  

For additional information: Does the application of an adhesive layer improve the bond strength of etched and silanized glass ceramics to resin-based materials? A systematic review and meta-analysis