An Evaluation Of Bacterial Dynamic Adhesion On Resin Infiltration By Using SEM

[Objectives]Resin infiltration is a new product for curing early enamel caries. When it infiltrate into the pores of the center of demineralization,it can be cured with enamel and become a composite structure,which stop the early caries and protect normal enamel below.Whether a kind of dental material has a long-term retention in the special oral environment is the most concern.The formation of dental plaque on surface of materials are closely related to the stability of materials in oral,as well as secondary caries,periodontitis.The aim of this study was to establish a model in situ to collect intact natural dental plaque biofilm.and evaluated the dynamic forming process of the biofilm on resin infiltration (Icon,DMG) using scanning electron microscope (SEM).versus that of composite resin(Z350,3M ESPE).[Methods]18 enamel slabs prepared from third molars freshly extracted, were divided into two groups randomly, separately with resin infiltrated and composite resin filled. Specimens were fixed on the buccal sites of maxillary molars with individual splints for 2.4,6,12,18h and 1,2,3,7d to allow biofilm formation.The surfaces of all specimens were evaluated under a scanning electron microscope (SEM).[Results]Bacterias and extracelluler polymer substances (EPS) of dental biofilms were clearly visible.Compared to Z350,Icon had a more smoother surface after polishing.On the Icon surfaces,bacterial adherence and aggregation were fast between 4 to 24h mainly of coccus. In 12-18h extracellular matrix appeared more, some cells blurred, slightly thickened and continuously to be connected between the colonies. Dental biofilms matured around 24h with bacillus could be seen.In 2-7d the biofilms thickend,and showed a decline of coccus in the proportion,forming more matured biofilms of more complex compositions, and three-dimensional structures with filamentous, rod-shaped bacteria as scaffolds.Compared to Icon,Z 350 had a more amount of bacterial adhesion and a higher degree of bacterial aggregation.Coccus aggregated as plexiforms on resin infiltration in 12～18h,while coccus grow as chains of unseparated cells and interwoven into a network in composite resin, with coccus continued to attached. At 24 h filamentous bacterias and the "corn con" could be seen on surfaces of Z350,while which could also be seen at 2-3d in Icon samples. No significant differences of biofilms morphology could be seen at 3-7d.[Conclusions]The model in this study could form a intact natural dental plaque biofilm in situ.and observed the dynamic forming process of biofilms at different time points.The initial adherence rate and the types of bacteria of these two resins are different,which might be associated with that resin filtration might get a more smooth surface.