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SUMMARYNanohybrid resin composites present conventional particles to be mixed with nanomeric fillers and, therefore, it is unknown whether they may perform similarly to nanofilled or microhybrid resins. The current study investigated the properties of nanohybrid resins (TPH 3 , Grandio, Premise, Concept Advanced) in comparison with a nanofilled (Supreme XT) and a microhybrid (Z250) composite. The inorganic fillers were characterized by SEM/EDS analysis. Diametral tensile strength (DTS), surface roughness before and after toothbrush abrasion, Knoop Hardness (KHN), water sorption and solubility were evaluated. The data were separately analyzed by ANOVA and the Student-Newman-Keuls' tests (p<0.05). The results of all analyses were material-dependent. Noticeable differences in filler size and shape were detected among the materials. Supreme XT generally showed higher DTS and KHN compared to all the nanohybrids and also showed lower surface roughness before and after toothbrush abrasion compared to most of the materials tested. Similar results were generally detected for the nanohybrids compared with the microhybrid material. In conclusion, the nanohybrid resins generally presented inferior properties compared with the nanofilled composite and either similar or slightly better properties com-

No technique or material, when individually considered, was capable of achieving the mechanical strength of the sound teeth; however, the association of reattachment technique Circumferential chamfer with bonding system Single Bond could approximate the immediate impact strength of the restored teeth to that observed in the sound teeth.

The gamma radiation had a significant detrimental effect on bond strength to human enamel and dentin when the adhesive restorative procedure was carried out after radiotherapy.

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Increased etching periods may impair the bond strength to ceramics, while the use of an unfilled resin after silane may improve bond strength. The application of a bonding resin may also provide better infiltration to the irregularities created on etched surfaces, irrespective of the conditioning time. LZ Naves • CJ Soares • RR Moraes LS Gonçalves • MAC Sinhoreti • L Correr-Sobrinho SUMMARYThis study evaluated the influence of etching periods on the surface/interface morphology and bond strength to glass ceramic with or without application of an unfilled resin after silane. Ceramic discs were divided into 12 groups, defined by etching time with 10% hydrofluoric acid: G1/G7 -etching for 10 seconds, G2/G8 -20 seconds; G3/G9 -40 seconds; G4/G10 -60 seconds; G5/G11 -120 seconds and G6/G12-60 + 60 seconds. All the groups were silanated after etching and G7 -G12 received a layer of unfilled resin after silane. Microshear testing using resin cement was performed, with 12 resin cylinders tested per group. The data was submitted to two-way ANOVA and the Student-Newman-Keuls' test (p<0.05). Evaluation of the etching pattern and bonding interfaces was conducted by SEM. The bond strength means (MPa) were: 19.4 ± 3.5, 22.3 ± 5.1, 22.2 ± 3.2, 17.8 ± 2.1, 15.3 ± 3.0 and 14.3 ± 1.8 for G1-G6 and 17.4 ± 4.8, 21.3 ± 2.1, 21.1 ± 2.3, 24.7 ± 5.8, 20.4 ± 2.2 and 18.5 ± 4.6 for G7-G12. Poor etching was detected after 10 seconds of conditioning; whereas deep channels were extensively 421 421 Naves & Others: Bonding to Ceramic Using Unfilled Resin observed on surfaces etched for 120 and 60 + 60 seconds. Unfilled voids underlying the ceramiccement interface were detected when only silane was applied. Full completion of the irregularities on G11 was detected using unfilled resin. When only silane was applied, the 60-second group and those etched for longer periods showed lower bond strengths. When both silane and unfilled resin were applied, all etching periods generally showed similar values. In conclusion, the etching period influenced the surface/interface topography and bond strength to ceramic. The application of unfilled resin was able to infiltrate all unfilled voids beneath the ceramic-cement interface, except on re-etched surfaces.