The effect of surface roughening of orthodontic elastomers on hydrophobicity and in vitro adherence of Streptococcus gordonii.

Objectives: Biofilm formation around orthodontic appliances causes gingivitis, enamel decalcification and caries. Bacteria adhere less readily to superhydrophobic surfaces. The aim of this study was to determine whether a superhydrophobic surface could be generated on orthodontic elastomers by surface modification in order to reduce bacterial adhesion.

Materials And Methods: Orthodontic elastomers were modified with sandpapers of various grit sizes (80-600 grit). Surface roughness of the modified and unmodified surfaces was assessed qualitatively with scanning electron microscopy and quantitatively with confocal microscopy. Water contact angles were measured with a goniometer to quantify hydrophobicity. Measurements were performed on unextended elastomers (100% original length) and elastomers extended to 150%, and 200% of the original length. Adhesion of Streptococcus gordonii to saliva coated elastomers was measured by counting colony forming units on agar plates.

Results: Abrasion with different sandpapers produced elastomers with surface roughness (R) ranging from 2 to 12 μm. Contact angles followed a quadratic trend with a maximum contact angle of 104° at an R of 7-9 μm. Average water contact angles, when viewed perpendicular to the direction of extension, decreased from 99° to 90° when the extension was increased from 100% to 200% and increased from 100° to 103° when viewed parallel to the direction of extension. Bacterial adhesion increased as roughness increased and this effect was more pronounced with elastomer extension.

Conclusion: The surface roughness of orthodontic elastomers influences both their hydrophobicity and bacterial adhesion. Superhydrophobicity of elastomers could not be achieved with sandpaper abrasion.