Multivariate analysis of surface physico-chemical properties controlling biofilm formation on orthodontic adhesives prior to and after fluoride and chlorhexidine treatment

Biofilm formation on orthodontic adhesives is a serious clinical problem, as it leads to enamel demineralization around fixed orthodontic appliances, often leaving white spot lesions after their removal. The aim of this work was to determine the influence of surface physico-chemical properties of four commonly used orthodontic adhesives (Concise (TM)), Fuji ORTHO (TM) LC, Ketac Cem mu, and Transbond (TM) XT) on early bacterial biofilm formation. In addition, effects of two commercially available mouthrinses (0.05% sodium fluoride and 0.2% chlorhexidine gluconate) on these properties and biofilm formation were determined. Water contact angles on the adhesives decreased after fluoride and chlorhexidine treatment, concurrent with an increase in carbon and a decrease in oxygen surface concentrations, except for Transbond, as determined by X-ray photoelectron spectroscopy. No fluorine was detected on any of the adhesive surfaces after fluoride treatment, while all surfaces showed chlorine after chlorhexidine treatment. Surface roughness of the adhesives measured using three-dimensional optical profilometry was around 4 mu m and found not to be a factor governing early biofilm formation. Multiple linear regression analysis indicated that early biofilm formation by Streptococcus sanguis could be explained in a model comprising hydrophobicity and the prevalence of oxygen- and nitrogen-rich components on the adhesive surfaces. (c) 2006 Wiley Periodicals, Inc.