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Wattanasirmkit K, Srimaneepong V et al. Dent Mater J 2015; 34: 302–309

Glass joining can use an intermediate ceramic layer. Such an approach is used in decorative stained glass and fuel cell technology. Could an intermediate ceramic layer prevent 'chipping' of laminate all-ceramic restorations? This somewhat confusing paper reports in vitro experiments investigating, among other characteristics, the shear bond strengths of all-ceramic restorations comprising veneered feldspathic porcelain on a lithium disilicate glass-ceramic liner that in turn is joined to the zirconia substructure. With no theromocyling, the shear bond strengths of the test specimens were improved with the intermediate glass-ceramic layer, compared with the controls with no intermediate layer. A possible explanation for these observations is that the intermediate lithium disilicate ceramic layer reduces the stresses caused by the different coefficients of thermal expansion between the zirconia substructure and veneering porcelain. But after thermocycling, the shear bond strengths of the test specimens were reduced, so much so that the mean value for 'the 'control group...was significantly higher than the thermocycled specimens (p <0.05)'.