Repair Bond Strength of Aged Composites Using Different Bonding Techniques

Purpose: To determine bond strength between an existing aged composite and a new added composite using different combinations of surface treatments and bonding agents. Methods: Composite blocks (6x5x3mm) were prepared from Z100 A2 (3M/ESPE). Blocks were finished on one surface using Soflex discs (3M/ESPE). Blocks were randomly divided into four groups (n=12). Gr1: no aging(control), Gr2: 24h aging, Gr3: 1 month aging and Gr4: 3 months aging in artificial saliva at 37 °C. Groups 2, 3, 4 were then subdivided into 4 subgroups according to the surface treatment and bonding system; A: diamond bur roughening + acid-etching + Scotchbond Plus (3M/ESPE), B: diamond bur roughening + Clearfil SE (Kuraray), C: acid-etching + Scotchbond and D: Clearfil SE. Control blocks were not polished, aged, surface treated or bonded. Bonding was carried out according to manufacturers' instructions. Z100 build-ups shade A4 were bonded to the above aged and surface-treated blocks. Bonded blocks were then stored for 24h at 370C and then sectioned to provide 1x1x6mm sticks for micro-tensile bond strength testing. Results: Subgroups A,B (composite blocks with surfaces roughened using diamond bur) showed higher micro-tensile bond strength compared with composites repaired only using bonding systems (groups C,D). Groups that were repaired after 3 month did not show any drop in their micro tensile bond strength values except with the Clearfil subgroup. Conclusions: Roughening of the composite surface to be repaired using diamond burs is recommended, in particular, when self-etching bonding system is used. Acknowledgments: Materials provided by 3M and Kuraray.