Microtensile-bond Strength of Composite to Enamel Exposed to Soft Drinks

Objective: To determine if soft drink exposure on human molar teeth affects the microtensile bond strength of composite to enamel. Methods: Sixteen crowns of extracted human molars were sectioned mesiodistally and mounted in stone. The middle-third enamel of the buccal and lingual surfaces was flattened slightly. The flattened enamel specimens were exposed to soft drinks (Coca-cola, Mountain Dew) at room temperature for 15 minutes then artificial saliva at 37°C for 2 hours. This sequence was repeated 3 times a day for twenty-eight days. The soft drinks were changed after each exposure to the specimens and the artificial saliva was changed daily. The specimens were kept in artificial saliva at 37°C for the remaining time. The control group specimens were kept in 37°C artificial saliva without exposure to soft drinks. A two-step, self-etch adhesive (Clearfil SE, Kuraray) was applied to the flattened enamel surfaces per manufacturer's instructions and light cured (Bluephase 16i, Ivoclar). Composite (Z-250, 3M/ESPE) was incrementally placed and cured to approximately 4-5 mm. The specimens were sectioned into 1 x 1 mm beams (Isomet, Buehler). One to four beams were created from each specimen and a total of fourteen beams were used per group (n=14). The beams were separated in tension by a universal testing machine (Instron Model 5543) at a crosshead speed of 1 mm/min. A mean (MPa) and standard deviation were determined per group. Data was analyzed with an ANOVA (alpha=0.05). Results: Artificial saliva (control): 26.7 ± 11.0 MPa; Coca-Cola: 20.2 ± 14.3 MPa; Mountain Dew: 20.8 ± 8.0 Mpa. There was no significant difference between groups (p=0.261). Conclusions: Twenty-eight -day exposure of the soft drinks (Coca-cola, Mountain Dew) had no significant effect on the microtensile-bond strength of Z250 composite resin to enamel using Clearfil SE, a two-step self-etching bonding agent.