Sex-related differences in response to zinc pyrithione shampoo vs. non-anti-dandruff shampoo.

OBJECTIVE: Sex-related differences in skin properties may be expected to impact dandruff formation and treatment. A meta-analysis approach was undertaken to investigate potential differences between males and females in response to zinc pyrithione (ZnPT) treatment vs. non-anti-dandruff (AD) shampoo. A separate pooled statistical analysis of ceramide and total protein loss endpoints was also undertaken to assess potential sex-related differences in stratum corneum properties that might influence response to ZnPT vs. non-AD shampoo in subjects with dandruff. METHODS: The meta-analysis approach included data from 17 half-head, double-blind, randomized studies (N = 2088) undertaken in Asia to assess the effectiveness of 1% ZnPT shampoo and/or non-AD shampoo in reducing dandruff severity, as assessed by Total Weighted Head Score Adherent Flake (TWHS-AF) methodology. Treatment duration was 4 weeks, with TWHS-AF measured at weekly intervals. Data from an additional three studies (N = 143) conducted in Asia were included in the pooled analysis of ceramide levels and protein loss from scalp skin of subjects with dandruff. RESULTS: Response to 1% ZnPT vs. non-AD shampoo was greater in males than in females at all time points; after 4 weeks, the between-treatment difference in TWHS-AF was -17.5 (95% confidence interval [CI] -19.5, -15.5) in males and -11.1 (-13.2, -8.9) in females. Sex-related differences were observed between males and females in response to both 1% ZnPT and non-AD shampoos. Males had a stronger response than females to treatment with 1% ZnPT shampoo, while dandruff decreased to a greater extent in females than in males when using non-AD shampoo. Statistically significant sex-related differences in ceramide levels and total protein loss were observed (both P < 0.01). Ceramide levels were 0.76 times lower (95% CI 0.60, 0.97) in males than in females, while total protein loss was 1.4 times greater (95% CI 1.1, 1.9) in males than in females. CONCLUSION: Males show a greater response than females to 1% ZnPT shampoo, while females show a greater response than males to non-AD shampoo. These findings may in part be explained by the sex-related differences observed in stratum corneum properties, which may make males more prone to dandruff than females.

Visualization of zinc pyrithione particles deposited on the scalp from a shampoo by tape-strip sampling and scanning electron microscopy/energy dispersive X-ray spectroscopy measurement.

OBJECTIVE: Zinc pyrithione (ZnPT) is widely used as an anti-fungal active in commercial anti-dandruff (AD) shampoos. The AD efficacy of ZnPT is highly dependent on the deposition of ZnPT particles onto the scalp during the process of shampoo application and rinse-off. Since ZnPT materials with different particle sizes and morphologies have different deposition behaviours, the measurement of the actual ZnPT deposition is critical to understand the AD performance delivered by different ZnPT shampoos. The aim of this study is to develop a robust and reliable method for visualizing the particle size and morphology of ZnPT deposited on the scalp from AD shampoos. METHODS: Hair was washed with a commercially available AD shampoo containing ZnPT and zinc carbonate (ZnCO3 ). Tape strips were applied to collect the deposited particles from the scalp after AD shampoo application and rinse-off. The scalp tape strip samples were subjected to scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) measurement. The morphology of the ZnPT particles was visualized by SEM imaging and identification of ZnPT particles was confirmed by EDX analysis. RESULTS: For the commercial shampoo studied it was observed that two zinc-containing particulates with different morphologies and composition remained on the scalp after shampoo application and rinse-off. As indicated by the EDX spectra, the ZnPT particles deposited onto the scalp surface had polygonal crystal structures. ZnCO3 was also deposited onto the scalp surface. This material was mainly present as aggregated particulates. CONCLUSION: An ex vivo method that combines tape strip sampling and SEM/EDX has been developed for measuring and visualizing the particle size, morphology and composition of ZnPT deposited on the scalp from AD shampoos. This ex vivo measurement method provides higher imaging resolution and more chemical specificity than reflectance confocal microscopy (RCM). To the best of our knowledge, this is the first time that ZnPT particles were distinguishable from other zinc particles on the scalp. Moreover, the new method allows the microstructures of both ZnPT and other zinc particles on the scalp to be imaged.

The effect of a calcium carbonate/perlite toothpaste on the removal of extrinsic tooth stain in two weeks.

OBJECTIVE: To assess the effect of a calcium carbonate/perlite toothpaste on the levels of extrinsic stain removed at two weeks compared to a silica control toothpaste. DESIGN: In this parallel group, double-blind study, subjects were stratified by natural baseline stain and tobacco use and allocated at random to one of the two study toothpastes. Subjects brushed with their allocated toothpaste twice daily for two weeks before extrinsic tooth stain was again assessed. SETTING: The study was performed at 4-Front Research UK Limited, Maldon, UK. PARTICIPANTS: 152 adult subjects with at least eight assessable incisors/ canines with natural extrinsic tooth stain completed the study. METHODS: The extrinsic tooth stain on the facial surfaces of incisors and canines was measured using the Macpherson modification of the Lobene Stain Index. RESULTS: Both of the toothpaste groups had significantly less stain after two weeks of use compared to the baseline value (p<0.001). Analysis of covariance on the sum of the whole mouth stain scores showed that the calcium carbonate/perlite toothpaste removed significantly more stain over the two week study than the silica control toothpaste (p<0.05). CONCLUSIONS: Twice daily brushing for two weeks with a calcium carbonate/perlite toothpaste removes more extrinsic stain than a silica control toothpaste.

The measurement of enamel and dentine abrasion by tooth whitening products using an in situ model.

OBJECTIVES: To determine the enamel and dentine wear of two whitening toothpastes using an in situ model with ex vivo brushing. METHODS: Human enamel/dentine (approximately 50:50) blocks (approximately 4 x 4mm) were placed in the upper buccal aspects of full or partial dentures of a group of 25 subjects. Subjects brushed the specimens ex vivo with either a calcium carbonate/perlite or silica containing whitening toothpaste under exaggerated conditions as compared to normal for 30 s, twice per day. Specimens were removed after 4, 8 and 12 weeks and the wear to the enamel and dentine was determined. Enamel wear was determined by change in Knoop indent length and dentine wear was determined from the enamel-dentine step height, measured using optical profilometry. RESULTS: The mean wear after 12 weeks was for enamel 0.27 and 0.19 microns, and for dentine 34.3 and 61.1 microns, for the calcium carbonate/perlite and silica toothpastes respectively. There were no significant differences between products after 12 weeks. The rate of wear was found to decrease throughout the duration of the study. CONCLUSION: There were no significant differences between the two whitening toothpastes in terms of enamel and dentine wear after 12 weeks brushing.