Are adhesive technologies needed to support ceramics? An assessment of the current evidence.

Despite large variations in the reported fracture strengths of dispersion strengthened, glass infiltrated, castable, pressable and machinable ceramics utilised for the construction of all-ceramic crowns, the annual clinical failure rate reported for these materials in the dental literature is remarkably consistent at ca 3%. These results emphasise that there may be little correlation between the average fracture strength and resultant clinical performance. Consequently, if ceramics are to be used for dental applications, then clearly more detailed information on the statistical variations in strength combined with the influence of cementation media are required. The effect of adhesive technology has been examined in laboratory and clinical studies. The laboratory studies focused on the effect of cement lute on crown performance, whilst surface degradation and strengthening effects with different systems were examined utilising conventional materials science techniques. Clinical studies focused on the failure rates of conventionally luted and adhesively luted crowns and inlays. There would appear to be evidence from clinical studies that crowns luted with a resin cement and with the placement procedure incorporating a dentine bonding stage have enhanced rates of survival. It is therefore concluded that the available research strongly suggests that the use of resin as a luting material for ceramic restorations is indicated, given the research from three differing sources - laboratory fracture studies comparing restorations luted with resin vs other materials, clinical studies, and laboratory studies examining the surface sealing/strengthening effect of resin on ceramic. Laboratory studies also confirm the enhanced resistance to fracture of crowns cemented with an adhesive procedure.