Evaluation of surface characteristics of direct composite resins after finishing and polishing using fractal analysis

Surface characteristics of two composite resins (Filtek Ultimate Universal Restorative, 3M ESPE and Filtek Ultimate Flowable Restorative, 3M ESPE) after finishing and polishing procedure using three systems: two steps Sof-Lex system, 3M ESPE, multi-steps Super Snap system, Shofu, Inc. Kyoto, Japan and multi-steps OptiDisc system, KerrHawe SA were analyse using SEM and AFM investigations. Fractal analysis was performed on SEM and AFM images and the mean fractal dimension was calculated for each sample using FracLac software. For both tested materials decreased fractal dimension with the increase of SEM magnification was observed. Multi-steps OptiDisc system determined the biggest decrease of fractal dimension for both materials, followed by Sof-Lex system and Super Snap. Fractal analysis seems to be an appropriate method to investigate the complex structure of composite resins.