Dental caries is the localized destruction of susceptible dental hard tissues by acidic by-products from the bacterial fermentation of dietary carbohydrates . The disease process is initiated within the bacterial biofilm (dental plaque) that covers the tooth surface . The development of dental plaque involves the adhesion of bacteria and subsequent colonization. The influence of the adsorbed proteins on bacteria adhesion has been suggested as playing a major role in bacteria–tooth interactions . Compared to coronal caries (dental caries development in the tooth crown), the prevalence of root caries (dental caries development in the tooth root) is increasing. This can be due to extended root exposure time by increased life expectancy and the special anatomical location of the root in the oral cavity . A systematic review concluded that about 40% of elderly people aged 70 suffered from untreated root caries . Dentine on the root surface is soft and porous. Bacteria penetrate further into the tissue at an earlier stage of lesion development in root caries . Thus, control of bacterial initial adhesion to the root surface is critical for the prevention of root caries .