XT 3M Research Articles

The Effect of Three Polishing Systems on the Surface Rugosity of One Composite Resin

Direct restorations in composite resin require superficial rugosity appropriate to guarantee a surface free of biofilm buildup, which interferes with the durability of the restoration, its properties and the aesthetic aspect. Thus, it is relevant to know the behaviour of the finishing and polishing systems. The in vitro study aimed to compare the polishing efficiency of three different polishing systems in promoting the surface smoothness of a nanocomposite resin. Sixty specimens of the nanocomposite resin Filtek Z350 XT (3M) were made, randomly divided into three groups (n=20), according to the tested polishing systems: Enhance (Dentsply), DFL Polishers, and Sof-Lex Spiral (3M). The surface rugosity of the samples was measured by means of the rugosimeter equipment. The data were analysed through statistical tests: ANOVA two-way and post-hoc Tukey. The results indicated Sof-Lex (3M) polishing discs as the ones with the lowest average surface rugosity (0.13µm), presenting statistically significant results (p<0.05); followed by the abrasive rubbers of the DFL system (0.17 µm) and the Enhance system (Dentsply), which showed greater average surface rugosity (0.30 µm). The lowest surface rugosity of the composite resin evaluated in this study (Z350 XT- 3M) was obtained after polishing with the multi-step system (Sof-Lex), from the same manufacturer.

Bond Strength of Brackets Bonded with Chemically and Light Activated Materials after Thermal Cycling

The aim of this study was to evaluate the bond strength of orthodontic brackets bonded to tooth enamel with different polymer composites after simulated clinical aging, and analyze the enamel/ bond system fracture interface. 80 human premolars, were randomly divided into five groups (n = 16). G1: CO (Concise Ortodontica—3M ESPE), G2: SB (SuperBond—Ortho Source), G3: FMO (Fill Magic Ortodontico—Vigodent), G4: TXT (Transbond XT—3M ESPE) and G5: TP (Transbond Plus Self Etching Primer + Transbond Plus Color Change—3M ESPE). In all groups, the metal orthodontic bracket was bonded to the tooth enamel surface. The specimens were submitted to 3000 thermal cycling baths for 30 s, at temperatures of 5°C, 37°C and 55°C (±1°C). Afterwards they were subjected to shear testing and the results were analyzed by the Student’s-t test (p G5 > G2 > G3. In all groups the majority of the fractures at the interface of the specimens were cohesive, except in G3, which presented the largest number of adhesive fractures. After clinical aging, the chemically activated material (CO) showed higher bond strength than the light activated types (FMO, TXT and TP). The self-etching adhesive system (TP) showed similar bond strength to that of conventional systems (FMO and TXT).