SUMMARY Statement of the Problem:The color stability of resin cements plays a major role in the esthetic performance of porcelain laminate veneers. Some dual-polymerizable resin cements used to bond porcelain laminates were shown to undergo color changes during service. Some recently produced cements are described as being color stable, but scientific data are not available. Clinical RelevanceWhile the studied cements behaved acceptably according to the color change index (∆E), they functioned differently in regards to opacity, especially the self-cure ones.

Aim: To assess the effect of adding zinc oxide nanoparticles to dental adhesives on their anti-microbial and bond strength properties. Methods: 45 human premolars were cut at the cement enamel junction (CEJ) and the crowns were sliced into buccal and lingual halves. The specimens were classified into three groups, etched with 37% phosphoric acid for 15 s and rinsed for 30 s. Single Bond, Single Bond+5% zinc oxide and Single Bond+10% zinc oxide were used in the first, second and third groups. A cylinder of Z250 composite was bonded and cured for 40 s. For anti-bacterial testing, 10 samples of each group were assessed by direct contact test; 10 μL of bacterial suspension was transferred into tubes containing adhesives and incubated for one hour; 300 μL of brain heart infusion (BHI) broth was added to each tube and after 12 h, 50 μL of bacteria and broth were spread on blood agar plates and incubated for 24 h. Results: The colony count decreased significantly in the second and third groups compared to the first. Conclusions: Incorporation of zinc oxide nanoparticles into dental adhesives increases their anti-microbial properties without affecting their bond strength.

Aim: The purpose of this study was to evaluate of the effects of modified 45S5 bioglass (BG) before, after, and during the bleaching procedure with 35% hydrogen peroxide (HP) on the tooth colour change and physicochemical and morphological properties of human enamel. Methods: Forty-two human premolar enamel samples were prepared and randomly divided into six groups as G1: control (deionized distilled water for 20 min), G2: BG (Bioglass suspension for 20 min), G3: HP (hydrogen peroxide 35% for 20 min), G4: BG before HP (Bioglass suspension for 20 min followed by hydrogen peroxide 35%) , G5: BG after HP (hydrogen peroxide 35% followed by Bioglass suspension for 20 min), and G6: BG during HP (Bioglass in hydrogen peroxide 35% suspension for 20 min). The treatment procedure was performed on the whole enamel surface. Colorimetry was done before and after the treatment procedure. Two specimens from each group were selected for morphological analysis with scanning electron microscope (SEM). Microhardness analysis was performed after the treatment procedure and chemical analysis of BG dissolution was done for BG+DDW and BG+HP suspensions. Results: No statistically significant difference in colour was observed among different groups (P= 0.073133) and the yellowness index decreased in all of the four HP groups. The greatest reduction in microhardness occurred in groups HP and BG before HP (P<0.001) while the BG group showed increased microhardness measurements (P<0.001). Statically significant differences in microhardness were found among the groups. Elemental analysis showed significantly increased levels of Ca and P in BG after HP and BG before HP groups when compared to the HP group. Ionic release of BG was significantly greater in HP when compared to DDW. Conclusion: Using BG before HP had a greater protective effect since it increased microhardness more effectively, decreased mineral loss, and retained the integrity of the enamel surface. The HP group had the lowest microhardness and BG during HP showed less protective effects compared to BG before HP.

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To compare Modulation Transform Function (MTF) between standard monofocal spherical hydrophobic acrylic Alcon SA60AT (Bausch and Lomb) and hydrophilic acrylic Rayner Superflex (620H) (Rayner) intra-ocular lenses (IOLs). This cross-sectional study was conducted on 68 patients who underwent cataract surgery. The hydrophobic Alcon SA60AT IOL was implanted in 39, and the hydrophilic Rayner Superflex (620H) was implanted in 29 eyes. The OPD Scan III (Nidek) was used to assess MTF in normal pupils under mesopic light conditions 1 and 3 months after the surgery. t-test showed no significant difference in mean MTF between the two IOLs in the 2 follow-ups (P=0.788). The results of repeated measure ANOVA for each type of IOL indicated that MTF increased significantly in the hydrophilic group versus the hydrophobic group in the 3rd month (P=0.033). Moreover, the results of repeated measure ANOVA showed that MTF was affected by the type of IOL and refractive error in the 3rd month (P=0.029, P=0.025). It seems that the material of IOL and post-surgical residual refractive error can affect the visual acuity of pseudophakic patients. Although the hydrophilic IOL provided a better MTF three months after the surgery, studies with longer follow-ups are required to confirm the results.