Microtensile Bond Strength Between Composite Resin and Discolored Dentin After Amalgam Replacement Using Different Universal Adhesives

Background: It is common to replace amalgam with composite resins for different reasons. Changes in the dentin substrate after amalgam restorations might affect the bond strength between composite resin and dentin. This study evaluated the microtensile bond strength of composite resin to discolored dentin following amalgam replacement with universal adhesives. Methods: In this in vitro study, thirty-two sound human premolar teeth were collected. After preparing classic class I amalgam cavities measuring 2 mm in depth, 3 mm mesiodistally, and 2.4 mm buccolingually, half of the samples were randomly selected and restored with high-copper amalgam and underwent a thermocycling procedure (5000 cycles). They were stored at 37 ºC and 100% humidity for six months to form amalgam corrosion products. After removing the amalgam, each half was divided into four subgroups based on adhesive type (G-Premio Bond/All-Bond Universal) and bonding technique (self-etch/etch-and-rinse). Then, all samples were restored with composite resin. The microtensile bond strength was calculated, and data analysis was conducted using SPSS 25 and t-tests. Results: The bond strength values in the amalgam-affected subgroups were significantly (P<0.05) lower than normal dentin. In all groups, the bond strength of the All-Bond Universal was higher than that of the G-Premio Bond. However, the bond strength in the etch-and-rinse technique in normal dentin was significantly (P<0.05) higher than the self-etch technique. The bond strength in the amalgam-affected dentin subgroups with the All-Bond Universal was comparable to the bond strength of this adhesive to normal dentin with the self-etch technique. Conclusion: All-Bond Universal is suggested for both self-etch and etch-and-rinse techniques in amalgam replacement with composite resin. However, the self-etch technique is recommended if the G-Premio Bond is used.