Bond durability of self-adhesive composite cements to dentine

Clinically, the most easy-to-use composite cements are the so-called self-adhesive composite cements (SAC's). Hardly any data is however today available on the long-term bonding effectiveness of such luting composites. The purpose of this study was to evaluate the bond durability of different composite cements used to lute feldspathic ceramic blocks onto dentine.

Four SAC's (Clearfil SA Cement, Kuraray; G-CEM, GC; SmartCem2, Dentsply; Unicem 3M ESPE), one 'self-etch' (Clearfil Esthetic Cement, Kuraray) and one 'etch-and-rinse' (Variolink ll, Ivoclar-Vivadent) multi-step composite cement were used to lute feldspathic ceramic blocks (Vita Mark II, Vita) onto dentine surfaces. Teeth were distributed randomly in 24 experimental groups according to two different surface-preparation techniques ('SMEAR-COVERED' versus 'SMEAR-FREE') and storage conditions ('IMMEDIATE' versus 'AGED'). Failure patterns were evaluated with a stereomicroscope, and afterwards imaged using Feg-SEM. Two additional specimens were processed for cement-dentine interfacial analysis using TEM.

A linear mixed effects statistical model revealed significant differences for the variables 'composite cement', 'surface preparation' and 'ageing'. All self-adhesive composite cements, except Unicem (3M ESPE), did bond less favourably to fractured dentine. TEM revealed an ultra-structurally different interaction of the composite cements with 'SMEAR-COVERED' and 'SMEAR-FREE' dentine.

All SAC's suffered most when luted to 'SMEAR-FREE' (fractured) dentine, fortunately of no clinical relevance and most likely due to enhanced water sorption through the open tubules. When luted to 'SMEAR-COVERED' dentine, all SACs appeared equally effective and durable as the 'etch-and-rinse' and 'self-etch' multi-step composite cements. Solely the SAC SmartCem2 (Dentsply) appeared clearly less favourable and consistent.