Nowadays, bleaching of the teeth within the dental office is one of the most widespread techniques to correct tooth discoloration. Variability of the materials and techniques accompanied with the trend toward esthetic restorations with minimally invasive approaches are increasing. The use of laser in this regard has also been taken into consideration. The aim of this study was to evaluate the effects of in-office versus laser bleaching on surface roughness of enamel. Fifteen freshly extracted human molars were sectioned mesiodistally to produce 30 lingual and buccal enamel blocks. Samples were mounted in transparent acrylic resin blocks and polished before treatment. Samples were randomly assigned to laser bleaching (LB) and office bleaching (OB) groups (n = 15 each). Pretreatment evaluation of microroughness was carried out for all samples using profilometer. Samples were treated twice in the OB group with Opalescent Xtra Boost and in the LB group using a laser-activated gel. Microroughness was evaluated after bleaching in both groups. Data were analyzed using repeated measure ANOVA. Both methods increased enamel surface roughness. Microroughness changes were significantly different between the two groups (p < 0.05). Microroughness significantly increased in the OB group (p > 0.05), but there was no significant difference in pre- and post-treatment roughness evaluation in the LB group (p < 0.05). Laser was considered a safer technique because it demonstrated a less surface roughness increase in comparison with the conventional office bleaching procedure.

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Roughness-induced hydrophobicity is an area of rapid growth which can be achieved through surface texture or surface porosity. Characterizing the effect of surface roughness on wetting behavior of surfaces with irregular shapes has always been a challenging problem. In this work, changing the environmental conditions during electrospinning of hydrophilic cellulose acetate solutions produced highly porous ribbon like fibers, differed widely in their surface morphologies. All samples showed apparent hydrophobicity with water contact angles between 1218 and 1468. The specific surface area was introduced for the first time, as a comprehensive parameter to predict contact angles of noncircular fibers. Statistical modeling revealed that the log-linear models would better fit the data in comparison with the other linear forms. These results confirmed that the specific surface area could be an appropriate single variable for predicting the contact angles of multiscale porous and wrinkled structures of electrospun fibers. Moreover, the membrane produced at 20 8C temperature and the relative humidity of 60% revealed surprisingly high specific surface area (276.63 m 2 /g) that seems very promising for industrial applications such as separation technologies.

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