The effect of surface roughness, produced by ultrasonic scaling, on biofilm formation and integrity on selected restorative materials

Aims: The aim of this research was to compare the effects of ultrasonic scaling on the surface roughness of various dental materials, subsequent biofilm formation, and biofilm integrity challenged by brushing. Methods: Specimens of each material were fabricated according to the manufacturers’ instructions, with a smooth surface simulating a clinically acceptable finish. Each specimen was divided into halves: one half (damaged) was evaluated for bacterial adherence and integrity after ultrasonic scaling; and the other half (undamaged) was evaluated without scaling. The first series of specimens (one specimen from each material) were analysed for surface roughness by a computer-assisted scanning confocal laser microscope (SCLM) prior to bacterial adhesion. The second series (two specimens of each material) was incubated with the bacterium, Streptococcus mutans. After 6 hours cultivation, one sample of each material was cleaned by a toothbrush to analyse the biofilm integrity. Surface characterisation and bacterial adhesion were assessed by scanning electron microscopy (SEM). The data from SLCM and SEM were analysed to compute the surface roughness (Ra value: Arithmetical mean deviation) and the biofilm coverage respectively. Results: Ultrasonic scaling produced various patterns of surface alteration, including microcracks, scratches and loss of material. Damaging the surfaces of most materials resulted in increased surface roughness (Ra). Greater biofilm coverage was found on the damaged surfaces of most materials compared to the respective undamaged surfaces. After standardised brushing, higher biofilm remained on the damaged surfaces than undamaged surfaces of most materials. Conclusion: Ultrasonic scaling resulted in damage (visualised by SEM) to all the tested materials. Surface roughness did not appear to significantly influence biofilm formation. Abrasion with a toothbrush was an effective way to remove biofilm, but there was no significant correlation between surface roughness and bacterial integrity