Micropore closure time is longer following microneedle application to skin of color

Microneedles (MNs) allow transdermal delivery of skin-impermeable drugs by creating transient epidermal micropores, and micropore lifetime directly affects drug diffusion timeframes. Healthy subjects (n = 111) completed the study, self-identifying as Asian (n = 32), Bi-/multi-racial (n = 10), Black (n = 22), White (n = 23), Latino (n = 23), and Native American/Hawaiian (n = 1). L* was measured with tristimulus colorimetry to objectively describe skin lightness/darkness. MNs were applied to the upper arm; impedance and transepidermal water loss (TEWL) were measured at baseline and post-MN to confirm micropore formation. Impedance was repeated for 4 days to determine micropore lifetime. Post-MN changes in TEWL and impedance were significant in all groups (p < 0.05), confirming micropore formation regardless of skin type. Micropore lifetime was significantly longer in Blacks (66.5 ± 19.5 h) versus Asians (44.1 ± 14.0 h), Bi-/multi-racial (48.0 ± 16.0 h), and Whites (50.2 ± 2.6 h). Latinos (61.1 ± 16.1 h) had significantly longer micropore closure time versus Asians (44.1 ± 14.0 h). When categorizing data according to L*, micropore lifetime was significantly longer in darker skin. We report for the first time that micropore lifetime differences are present in human subjects of different ethnic/racial backgrounds, with longer micropore lifetime in skin of color. These results also suggest that objectively measured skin color is a better predictor of micropore lifetime than self-identified race/ethnicity.

Effect of 10% Strontium Chloride and 5% Potassium Nitrate with Fluoride on Bleached Bovine Enamel

Background: Dental whitening has been increasingly sought out to improve dental aesthetics, but may cause chemical and morphological changes in dental enamel surfaces. Objective: This study evaluated in vitro the effect of 10% strontium chloride and 5% potassium nitrate with fluoride on bovine enamel, through tristimulus colorimetry, Knoop microhardness (KHN), and roughness after bleaching with 35% hydrogen peroxide (HP). Methods: The specimens were divided into three groups (n=15): GControl received bleaching treatment with 35% HP; GNitrate received bleaching with 35% HP followed by the application of 5% potassium nitrate with 2% sodium fluoride; and GStrontium received bleaching with 35% HP followed by the application of 10% strontium chloride on the enamel. Next, five specimens of each experimental group were subjected to KHN and tristimulus colorimetry tests, and 10 specimens were subjected to surface roughness (SR) tests. The values obtained for the different groups were compared through analysis of variance (ANOVA) followed by a post-hoc Tukey-Kramer test in addition to Student’s T-test for paired data. Results: In the intergroup comparison, KHN final differed statistically (p<0.05). The mean SR final of the experimental groups differed statistically from the GControl group (p<0.05). In addition, the groups did not differ in color variation (p>0.05). Conclusion: 10% strontium chloride and 5% potassium nitrate combined with 2% fluoride downplayed morphological changes to the enamel, without interfering with the effectiveness of the bleaching process.

In situ Effect of Nanohydroxyapatite Paste in Enamel Teeth Bleaching

ABSTRACT Aim Evaluate in situ the effect of nanohydroxyapatite paste (nano-HAP) before bleaching with hydrogen peroxide 35% (HP35%) by ion chromatography (IC) Knoop hardness number (KHN) and tristimulus colorimetry (TC). Materials and methods A total of 60 fragments were obtained from third molars included (3 mm × 3 mm × 3 mm) and the specimens were divided into three groups (n = 20): Gas chromatography (CG) (negative control group) = no bleaching; HP35% (positive control group) = HP35% whitening (whiteness HP35%); nano-HAP = application for 10 minutes before bleaching treatment + HP35%. The specimens were fixed to the volunteers’ molars. The KHN and TC were measured before and after bleaching. For IC, the dentin layer was removed, leaving the enamel that was crushed, and autoclaved for chemical quantification (calcium, fluorine, and phosphorus). The results of KHN and TC were analyzed statistically by analysis of variance (ANOVA) followed by Tukey test (p < 0.05). Results The HP35% group showed reduction of the Ca, F, and P ions. The initial and final KHN mean of the CG and nano-HAP did not differ statistically; however, the group of HP35% did differ statistically. The mean ∆E of the HP35% and nano-HAP groups did not differ statistically from each other. However, they differed from the CG. Conclusion The nano-HAP paste preserved the KHN, promoted the lower loss of Ca and P ions and an increase of F ions when compared with the CG, but did not influence the effectiveness of the bleaching treatment. Clinical significance Nano-HA is a biomaterial that has shown positive results in the prevention of deleterious effects on the enamel by the action of the office bleaching treatment. How to cite this article Gomes YSBL, Alexandrino LD, Alencar CDM, Alves EB, Faial KCF, Silva CM. In situ Effect of Nanohydroxyapatite Paste in Enamel Teeth Bleaching. J Contemp Dent Pract 2017;18(11):996-1003.