Purpose: To assess the effectiveness of a one-step and a two-step system with diamond pastes for polishing packable and flowable nanofilled resin composites.
Methods and materials: Thirty discs per material tested, a packable (Filtek Supreme XT, 3M ESPE) and a flowable nanofilled resin composite (Filtek Supreme XT Flow, 3M ESPE), were prepared pouring the materials into silicon molds (depth 2 mm, diameter 4 mm). The top surface of the specimens was covered with a Mylar strip and light-cured with a halogen lamp at 600 mW/cm2 for 60 s. Ten specimens of each material did not undergo polishing and were used as controls. Spec- imens to be polished were finished with 1200P sandpaper and assigned to two polishing protocols: one-step diamond paste (Unigloss, Intensive) (n = 10) and two-step diamond paste (Diamond Polishing Mint, Ultradent Products) (n=10). A lin- ear rugosimetric parameter (Ra) was measured three times on randomly selected areas of the top surface of all specimens. The arithmetic mean of the readings was calculated and con- stituted the statistical unit. Data were subjected to statistical analysis with Kruskal–Wallis and Mann–Whitney tests with Bonferroni correction (p<0.05). The morphology of top sur- faces of representative polished specimens was assessed by scanning electron microscopy.
Results: Both control and experimental groups never exceeded the 0.20-μm Ra threshold that can inhibit bacterial adhesion. The mean surface roughness and standard devia- tion of polished specimens were: packable/one-step system, 0.058 ± 0.006 μm; packable/two-step system, 0.048 ± 0.005 μm; flowable/one-step system 0.044 ± 0.006 μm; flowable/two-step system 0.049±0.006μm. The surface of the packable com- posite polished with the one-step system was significantly rougher than its Mylar control (p < 0.01) and flowable compos- ite polished with the same protocol (p < 0.05). Observation by scanning electron microscopy did not detect relevant surface irregularities. The surface of polished specimens appeared similarly smooth regardless of composite type or polishing system.
Conclusion: Both tested systems effectively polished both the flowable and packable nanofilled composites. A two-step system appears preferable for polishing the packable com- posite. The resin Filtek Supreme XT Flow can be efficiently polished with the one-step system.
