Investigation of the effects of current adhesives in application on delays on the success of dentin bonding

Objective: One of the most important stages affecting the long-term clinical success of composite restorations is the adhesive application step. The aim of our study is to investigate how a delay during the application of the adhesive to the cavity will affect the bonding to the dentin. Method: In the micro tensile bond strength tests of our study, a total of 45 teeth were used. Teeth were randomly distributed into three groups of 15 teeth in each. The first group was determined as Clearfil Se Bond (Kuraray Noritake Dental Inc., Japan), the second group was G-Premio Bond (GC, Tokyo, Japan) and the third group was Singlebond Universal Bond (3M ESPE, St. Paul, MN, USA). Then, three more subgroups were formed for different application times: immediate application, application after 3 minutes in the bonding dish, and application after 5 minutes in the bonding dish (n=5). Bonding agents were applied to the occlusal dentin surfaces in accordance with the manufacturer's instructions, and composite resin was placed on the teeth using the 2 mm layering technique. Each layer is cured for 20 seconds with Valo Cordless (Ultradent, South Jordan, Utah, USA) broad spectrum LED light device. Sticks of 1x1 mm were obtained from the prepared samples. The bond strengths of the sticks were tested in a micro tension tester (Micro Tensile Tester, Bisco Inc., Schaumburg, IL, USA). The crack patterns of the pieces that broke off as a result of the test were examined with a light microscope. Representative samples were also analyzed by Scanning Electron Microscopy SEM (Leo 1430, Zeiss, Germany). Results: The highest mean micro tensile bond strength values were obtained as 35.14±7.75 MPa in the group in which Clearfil SE Bond was used and there was no waiting period in the adhesive application (p<0.001). The lowest mean micro tensile bond strength value was found to be 13.43±4.69 MPa in the group where G-Premio Bond was applied by keeping it in the godet for 5 minutes (p<0.001). Adhesive failure rates were above 85% in all groups that were bonded after 5 minutes of waiting. In the SEM examinations of the fracture interfaces, smear layer-like images were detected on the composite surface of the Universal adhesive groups, which were kept for 5 minutes. Conclusion: Within the limitations of our study, it was noticed that the failure rates of the adhesive groups kept in the godet for 5 minutes were increased significantly. Bonding agents should be applied as soon as possible in accordance with the manufacturer's instructions. Key words: bonding agent, bond strength, adhesive bond.