Purpose: To study the influences on microstructure characteristic and bonding strength of acetone-based wet bonding systems when bonding on dry or wet dentin surface.
Methods: Three acetone-based wet bonding systems, Gluma One-Bond, Bond-1 and One-Step, were used to bond Chrisma composite resin to dry or moist dentin surface, and the bonding interface was observed with HITACHI S-2700 scanning electron microscope. Microtensile strengths of different groups were measured with Instro 1195.
Results: All three bonding systems can infiltrate well into dentin bonding interface in the wet groups. A hybrid layer of about 5microm could be observed with resin tags traversing from the resin layer above into the undemineralized dentin below and the lateral branch of dentinal tubule. In the dry groups, three zones, a surface and a basal hybrid layer sandwiching a middle hybridoid region, could be observed. The hybrid layer was very thinner. Microtensile strength had significantly decreased while bonding on dry dentin surface with acetone-based wet bonding systems, with the maximum decrease of 39% in Bond-1.
Conclusion: Incompletely infiltrated adhesive on dentin bonding interface could be observed and microtensile strength had significantly decreased while bonding on dry dentin surface with acetone-based wet bonding systems. Moist dentin surface, which can maintain collagen-rich fibrous network of demineralized dentin, is necessary when bonding with acetone-based wet bonding systems. Microtensile strength approaches to the real dentin bonding strength.