Microbial changes in biofilms on composite resins with different surface roughness: An in vitro study with a multispecies biofilm model

Abstract

Statement of problemThe single-species biofilm method cannot represent the interaction and complex functions of microorganisms associated with oral biofilms. PurposeThe purpose of this in vitro study was to investigate microbial changes in biofilms on composite resins of varying surface roughness by using a multispecies biofilm model with early-colonizing streptococci, middle colonizer, and late-colonizing gram-negative anaerobes. Material and methodsComposite resin disks were prepared with different roughness: SR180, SR400, SR1500, and SRGlass roughened with 180-, 400-, and 1500-grit silicon carbide paper and glass (control surface without surface roughening). Surface roughness was analyzed by confocal laser scanning and scanning electron microscopy. After multispecies biofilms had been grown on the composite resin surfaces, the adhesion of Streptococcus mutans, Streptococcus sobrinus, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and of total bacteria was determined after 1 (T1) and 4 (T2) days. Differences in surface roughness among the 4 groups were tested with 1-way ANOVA. Multifactorial analysis of variance was used to determine the time-related differences in the bacterial composition with respect to surface roughness (α=.05). ResultsThe order of SR, from highest to lowest, was SR180 (1.45 ±0.11 μm), SR400 (0.62 ±0.05 μm), SR1500 (0.35 ±0.02 μm), and SRGlass (0.15 ±0.01 μm) (SR180>SR400>SR1500>SRGlass, P<.001). Increased surface roughness was not proportional to bacterial adhesion. Significant differences in the adhesion of total bacteria was only found between SRGlass and SR180 (SR180>SRGlass, P=.029). The adhesion of S. mutans and S. sobrinus to SR180 and SR400 was higher than that to SRGlass (SR180=SR400>SRGlass; S. mutans, P=.003; S. sobrinus, P=.002). However, the adhesion of A. actinomycetemcomitans and P. gingivalis to composite resin was not significantly influenced by surface roughness. Adhesion of total bacteria, S. mutans, and S. sobrinus increased from T1 to T2 (T1<T2, P<.001), whereas the adhesion of periodontal pathogens decreased from T1 to T2 (T1>T2; A. actinomycetemcomitans, P<.001; P. gingivalis, P=.013). ConclusionsDecreased adhesion of cariogenic streptococci and total bacteria was observed at surface roughness values of around 0.15 μm. Periodic finishing of surface roughness should be considered to minimize the adhesion of cariogenic streptococci to composite resin surfaces.