This study investigated the effects of two different light curing units and two staining solutions on the color stability of a hybrid composite and a nanohybrid composite after different immersion periods. Thirty disk-shaped specimens (10 mm in diameter, 2-mm thick) were fabricated for each of the resin composites, Clearfil AP-X and Filtek Supreme. The specimens were randomly divided into two groups according to the curing unit used: Group I specimens (n = 15) were cured with a quartz-tungsten-halogen (QTH) light for 40 seconds, and Group II specimens (n = 15) were cured with a light-emitting diode (LED) unit in standard mode for 40 seconds. The specimens were incubated in 100% humidity at 37 degrees C for 24 hours. Then, the baseline color values (L*, a*, b*) of each specimen were measured with a spectrophotometer according to the CIELab color scale. After baseline color measurements, five randomly selected specimens from each group (Groups I and II) were immersed in one of two staining solutions (tea or coffee) or distilled water (control). After 1, 7 and 30 days of immersion, the color values of each specimen were remeasured and the color change value (deltaE*ab) calculated. Color changes caused by immersion in tea and coffee for 30 days were only perceptible in the Clearfil AP-X specimens cured with QTH or LED. In the Filtek Supreme specimens, coffee perceptibly stained the teeth after all immersion periods and tea stained after 30 days. Polymerization with QTH or LED did not cause any significant difference in the color stability of Clearfil AP-X or Filtek Supreme. While there were no significant differences between staining solutions in the Clearfil AP-X specimens cured with LED after one and seven days of storage and one day of storage in the QTH cured specimens, significant differences were observed between water and coffee after seven days of storage. In the Filtek Supreme specimens cured with QTH or LED, there were statistically significant differences between the staining solutions after one and seven days of storage. After 30 days of storage, no significant difference was found between tea and coffee in either resin composite cured with QTH or LED. The effect of the staining solutions (tea, coffee) on color changes in composites was immersion time and resin-material dependent.

The purpose of this study was to evaluate the effect of various finishing and polishing procedures on the surface roughness of three new tooth-coloured restorative materials. The materials included a hybrid composite resin (Filtek Z250), a packable composite resin (Filtek P60), and an ormocer (organically modified ceramic) (Definite). Thirty-two specimens of each material were prepared and randomly divided into four finishing and polishing groups (n = 8): (i) diamond bur/silicone polishers, (ii) diamond bur/Sof-Lex discs, (iii) carbide bur/silicone polishers, (iv) carbide bur/Sof-Lex discs. Average surface roughness (Ra) in micrometers was measured with a Mitutoyo Surftest-402 Surface Roughness Tester and the data compared using anova, at P < or = 0.05. Surface topography was also assessed using the scanning electron microscope (s.e.m) from samples of each group. The Mylar strip produced the smoothest surface and finishing/polishing procedures; (ii) and (iv) were significantly smoother than (i) and (iii). The lowest variability in initial surface roughness between materials was also observed with ormocer group.

The fracture resistance values of endodontically treated teeth restored with either bulk fill/bulk fill flowable or fiber-reinforced composite were not different from those restored with conventional nanohybrid resin composite.

©Operative Dentistry, 2007, 32, 166-172 SUMMARYThis study compared the shear bond strengths of different adhesive systems to enamel and dentin of different depths. The adhesive systems used were: Single Bond one-bottle total-etch; AQ Bond one-step self-etching, Clearfil SE Bond two-step self-etching and Tyrian SPE/One-step Plus two-step self-etching.Eighty extracted non-carious human mandibular molars were mounted in self-curing resin and the occlusal surfaces were ground with a mechanical grinder to obtain flat occlusal enamel surfaces. After applying the adhesive systems, a plastic tube was attached to the enamel surfaces. The tube was filled with a universal hybrid resin composite, which was then polymerized. The specimens were stored in water at 37°C for 24 hours. Shear bond testing was carried out using an Instron Universal testing machine with a crosshead speed of 1 mm/minute. The occlusal enamel of the 80 teeth was removed to determine the bond strengths of the adhesives to superficial dentin. To obtain deep dentin, the same teeth were ground deep towards the pulp, with the remaining dentin thickness approximately 0.7 mm. The adhesives and restorative material were then applied to the prepared dentin surfaces following the methodology described above. For occlusal enamel surfaces, the bond strength of Single Bond was significantly higher than the other adhesives. Single Bond, Clearfil SE Bond and Tyrian SPE/One-step Clinical RelevanceBond strength to dental hard tissues was dependent upon the type of adhesive system used and varied with respect to tooth regions.

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