Adesão microbiana à superfície restauradora: influência das características do material na formação de biofilme

Abstract

The present thesis was divided into two studies, presented in form of articles, that evaluated the effect of materials characteristics on bacteria adhesion and biofilm formation. The first article aimed to evaluate the effect of grinding with diamond burs and low temperature aging on the material surface characteristics and bacteria adhesion on a Y-TZP surface. Y-TZP specimens were assigned into 6 groups according to two factors: grinding (3 levels: as-sintered; grinding with extra-fine diamond bur [25 μm grit] and grinding with coarse diamond bur [181 μm grit]), and hydrothermal aging to promote low temperature degradation (2 levels: presence/absence). Phase transformation (X-ray diffractometer), surface roughness, micromorphological patterns (atomic force microscope), and contact angle (goniometer) were analyzed. Bacterial adhesion (CFU/biofilm) was quantified using an in vitro polymicrobial biofilm model. Both the surface treatment and hydrothermal aging promoted an increase in m-phase content. Roughness values increased as a function of increasing bur grit sizes. Grinding with a coarse diamond bur resulted in significantly lower values of contact angle (P<0.05) when compared with the Xfine and control groups, while there were no differences (P<0.05) after hydrothermal aging simulation. The CFU/biofilm results showed that neither the surface treatment nor hydrothermal aging simulation significantly affected the bacteria adherence (P>0.05). Thus, based on the data of the first article we concluded that grinding with diamond burs and hydrothermal aging modified the Y-TZP surface properties; however, these properties had no effect on the amount of bacteria adhesion on the material surface. Later, the second article summarized the available data about how finishing and polishing methods affect the surface properties of different restorative materials with regard to bacterial adhesion and biofilm formation through a systematic review. Searches were carried out in MEDLINE-PubMed, EMBASE, Cochrane-CENTRAL and LILACS databases. From 2,882 potential articles found in the initial searches, only 18 met the eligible criteria and were included in this review (12 with in vitro design; 4 in situ; 2 clinical trials). Risk of bias analysis showed that only two studies presented low-risk (while 11 high, 5 medium). Thus, only descriptive analyses considering study design, materials, intervention (finishing/polishing), surface characteristics (roughness and SFE), and protocol for biofilm formation (bacterial adhesion) could be executed. Some conclusions could be drawn: the impact of roughness on bacterial adhesion seems not to be not fully related to a roughness threshold, especially in laboratory studies; the range of surface roughness among different polishing methods is wide and material dependent; finishing invariably creates a rougher surface and should be always followed by a polishing method; in vitro design seems not to be a powerful tool to draw clinical relevant evidences about the studies field, while in vivo and in situ designs are more recommended.