Dentine Wettability with Different Resin Adhesive Systems

Objectives: To determine the relative degree of hydrophobicity/hydrophilicity of the dentine surface after application of the bonding agent and prior to the application of the composite resin. Methods: 12 teeth were embedded individually in cold curing resin. The crowns were ground flat with 600-SC paper under running water to expose superficial dentine. The teeth were randomly divided into 4 groups. Each group was assigned to one of the four conditions; Gp1) Untreated dentine surface, Gp2) Dentine surface bonded with Adper Prompt L-Pop (3M ESPE), Gp3) Dentine surface bonded with APLP and a layer of bonding resin from Scotchbond Multi-Purpose Plus (3M ESPE), Gp4) Dentine surface bonded with Scotchbond 1XT (3M ESPE). Five measurements of the advancing and receding water contact angles (è) were taken for each of three drops per tooth, by Contact Angle Goniometer using consecutive sessile drops. Results: ANOVA and Tukey's test showed significant differences between the mean è values for the four testing conditions. The data for the advancing è in degrees were as follows: Gp1 21.5 ±4.2, Gp2 30.9 ±3.5, Gp3 44.9 ±3.1 and Gp4 56.0 ±3.7. The contact angle (è) was found to increase from Gp1 to Gp4, indicating increasing hydrophobicity of the surface. Untreated dentine showed the lowest mean è indicating a hydrophilic surface, whereas bonding with SB1XT displayed the highest è indicating a relatively much more hydrophobic surface. After application of the self-etching primer the surface was considerably more hydrophilic compared with the total-etch adhesive. Adding the bonding resin to the APLP resulted in an increased hydrophobicity, which should facilitate bonding with the hydrophobic composite resin. Conclusion: Dentine surface hydrophobicity is highly dependent on the wetting characteristics of the resin adhesive material.