Enamel Bond Durability of Universal Adhesives to Intact Surfaces

Objectives:
The aim of this study was to determine the bond durability of universal adhesives to unground and ground enamel surfaces in different etching modes.
Methods:
Two universal adhesives and a two-step self-etch adhesive were used: Clearfil Universal Quick (CUQ, Kuraray Noritake Dental), Scotchbond Universal (SBU, 3M ESPE), and Clearfil Mega Bond (CMB, Kuraray Noritake Dental). Human lower anterior enamel specimens were divided into four groups and subjected to the following treatments: (1) unground (UE) and (2) ground (GE) enamel in the self-etch (SE) mode, and (3) UE and (4) GE in the etch-and-rinse mode (ER). Bonded assemblies were either stored in distilled water at 37°C for 24 hours or subjected to 30,000 times thermal cycling (TC) between 5 and 55°C before SBS testing. The SBS to enamel was measured by the notched-edge SBS test, as described by ISO 29022.
Results:
Although all the adhesives in SE mode showed significantly lower SBS values in UE than in GE, all the adhesives did not show any significant differences between UE and GE in ER mode, regardless of the storage condition. The results are shown in the table below.
Conclusions: Phosphoric acid pre-etching before applying universal adhesives to unground enamel surfaces is essential to enhance initial and long-term of enamel bond strength.