In situ evaluation of cigarette smoke on dentin bond strength

Objective: The aim of this in situ study was to evaluate the cigarette smoke influence on the bond strength between resin composite and dentin. Methods: Twelve volunteers were assigned to 3 groups with 4 individuals each: Control Group (non-smokers); Group F10 (volunteers that smoked about 10 cigarettes a day); Group F20 (volunteers that smoked about 20 cigarettes a day). Each volunteer worn an intraoral device with dentin blocks fixed in the acrylic portion of the device with the dentin surface faced to the oral cavity. Each volunteer worn the intraoral device for 20 days. After that, the dentin blocks were removed from the intraoral device and the dentin surfaces were restored with resin composite (Z350, 3M ESPE) using the adhesive systems Scotchbond Multi-Purpose (three-step etch-and-rinse) or Clearfil SE Bond (two-steps self-etch). The restored blocks were cross-sectioned to 0.8 mm thick that resulted in sticks with 0.8 mm2 cross sectional areas. The sticks were submitted to microtensile test in an Instron Machine with crosshead speed of 0.5 mm/min. Results: Representative blocks of each group were analysed in Scanning Electron Microscope (SEM) showing partial removal of the smear layer after etching with phosphoric acid 35%, which suggests that cigarette smoke contaminated dentin surfaces appeared to be more resistant to etching. The statistics analysis (Student t tests) showed that cigarette smoke did not influence significantly the Scotchbond Multi-Purpose bond strength results, but, decreased significantly the bond strength of Clearfil SE Bond. Conclusion: The three-step etch-and-rinse adhesive system showed better adhesion performance in a cigarette smoke contaminated dentin.