In Vitro Evaluation of Structural Factors Favouring Bacterial Adhesion on Orthodontic Adhesive Resins

Abstract: Bacterial adhesion to the surface of orthodontic materials is an important step in theformation and proliferation of plaque bacteria, which is responsible for enamel demineralization andperiodontium pathologies. With the intent of investigating if adhesive resins used for bracket bondingare prone to bacteria colonization, the surface roughness of these materials has been analyzed,combining information with a novel methodology to observe the internal structures of orthodonticcomposites. Scanning electron microscopy, combined with focus ion bean micromachining andstylus profilometry analyses, were performed to evaluate the compositional factors that can influencespecific pivotal properties facilitating the adhesion of bacteria to the surface, such as surfaceroughness and robustness of three orthodontic adhesive composite resins. To confirm these findings,contact angle measurements and bacteria incubation on resin slide have been performed, evaluatingsimilarities and differences in the final achievement. In particular, the morphological features thatdetermine an increase in the resins surface wettability and influence the bacterial adhesion are thesubject of speculation. Finally, the focused ion beam technique has been proposed as a valuabletool to combine information coming from surface roughness with specific the internal structures ofthe polymers.