The linear and nonlinear rheology of viscoelastic mixed anionic-zwitterionic surfactant solutions has been systematically investigated. In the linear viscoelastic regime, these systems display nearly Maxwellian behavior with a unique relaxation time, tau0, and a characteristic elastic plateau modulus, G0. Linear rheological data were used to calculate the repitation and breaking times of the micelles, tau(rep) and tau(b), respectively. Surprisingly, the elastic modulus G0 significantly increases with salt concentration c(s), whereas tau(b) decreases by 1 order of magnitude. The strong effect of c(s) on the material parameters and microstructure of rodlike micelles allowed for the systematic investigation of the effect of these parameters on nonlinear flow. For samples with relatively long tau(b), the quasi-static flow diagram (stress vs shear rate) shows a stress peak followed by a metastable branch (a region of decreasing shear stress), whereas for samples with relatively short tau(b), this phenomenon is not observed. Transient flow responses corroborate quasi-static flow findings and further reveal the significance of microscopic dynamic parameters on flow behavior. Shear stress time series were recorded at constant shear rates, and above a critical shear rate, gamma(c2), stress fluctuations are observed. The amplitude of these stress fluctuations, Delta sigma, was found to scale as Delta sigma approximately equal to G0(tau(b)| gamma - gamma(c2)|)beta with beta approximately 0.5. This scaling is observed for micellar systems with tau(b) ranging from 0.12 to 0.01 s and G0 ranging from 1 x 10(3) to 7 x 10(3) dyn/cm2.

Background and Objective Goal was to evaluate the potential of in vivo optical coherence tomography (OCT) imaging to determine the response of patients with xerostomia to a dry mouth toothpaste versus fluoride tooth-paste placebo. Study Design/Materials and Methods Ten subjects with xerostomia participated in this double-blind, crossover, placebo-controlled study. After examination and OCT imaging, subjects used the first product for 15 days, followed by a 7-day washout period, and then they used the second product for 15 days. Data were acquired at 5-day intervals, also before and after the washout. Results Visual examination and tongue blade adhesion test did not reflect response to the product. Two imaging-based markers were identified: (i) In OCT images, epithelial thickness increased significantly (P < 0.05) after use of the dry mouth toothpaste, but did not change significantly (P > 0.05) after the use of a fluoride toothpaste and (2) Optical backscattering data showed progressive characteristic changes from baseline with use of the active product. Conclusions In this pilot study using in vivo OCT imaging, it was possible to detect and measure oral epithelial response to the dry mouth product versus placebo in patients with xerostomia. Clinical Implications This approach may permit site-specific assessment of xerostomia, individualized treatment planning and monitoring, and sequential mucosal mapping in patients with dry mouth.

White teeth can give confidence and tend to be associated with a healthier lifestyle in modern society. Therefore, modern tooth bleaching strategies have been developed, including the use of hydrogen peroxide and peroxymonosulfate. Although both molecules are oxidizing agents, their effects on the molecular composition of the stained teeth are yet to be determined. In this study, the molecular profiles of teeth bleached with these two different bleaching procedures were compared using liquid chromatography followed by tandem mass spectrometry (LC-MS/MS). GNPS spectral libraries and SIRIUS were used to perform metabolite annotation. The analysis revealed amino acids, dipeptides, and derivatives in peroxymonosulfate and H2O2 treated samples were altered compared to non-bleached sample controls. Additionally, the two bleaching methods led to distinct molecular profiles. For example, diterpenoids were more prevalent after peroxymonosulfate treatment, while treatment with H2O2 resulted in a greater abundance of alkaloids. This work elucidates the biochemical changes resulting from different tooth-whitening strategies.

A mechanical tooth brushing device coupled to an atmosphere pressure ionization ion trap mass spectrometer (API-IT-MS) combination has been developed to study the influence of time and dilution on aroma release from a model dentifrice system. API-IT-MS response to nine commonly used dentifrice flavor components was initially studied. Linear regression models were developed based on an exponential dilution method (EDA) to permit quantification of these compounds. Good linear fits were generated for the majority of compounds (R(2) > 0.92). The threshold detection limits were also calculated, and they greatly depended on the type of aroma compound. A brushing device was then coupled to the API-IT-MS and used to monitor the release profile of three aroma components from a model dentifrice system at flavor concentrations ranging from 0.1 to 20 mg g(-1). Large differences in the aroma release patterns were observed for different compounds (limonene, menthone and cinnamic aldehyde) that depended on their physicochemical characteristics (vapor pressure and log P), and on additional factors such as aroma-matrix interactions. In addition, a linear increase in API-IT-MS response with increased flavor concentration up to 1 mg g(-1) flavor was observed, while at higher concentrations, e.g. between 1 and 20 mg g(-1), a plateau in response was noticed. This suggests that at concentrations above 1 mg g(-1) a transition from a purely dissolved state to an emulsified state occurred. This fact influenced the time-dependent characteristics of the release curve (I(max) and t(max)) for the three assayed flavor compounds.