Effect of two types of charcoal toothpaste on the enamel surface roughness of permanent teeth.

Background: Charcoal in the composition of some kinds of toothpaste has created concerns regarding abrasiveness and subsequent complications. Considering the popularity of charcoal toothpaste, and the manufacturers' claims that no porosity is caused by activated carbon, this study aimed to compare the effects of two charcoal kinds of toothpaste and three conventional tubes of toothpaste on enamel surface roughness of permanent primary teeth. Materials and Methods: This in vitro experimental study evaluated 75 teeth mounted in acrylic resin. Teeth were divided into five groups (n = 15). The primary surface roughness of teeth was measured by a profilometer. The teeth were then subjected to wear test in a V8 cross-brushing machine with Bencer and RP charcoal toothpaste, Crest 7, Colgate Optic White, and Bencer fresh mint toothpaste. After rinsing and drying specimens, their secondary surface roughness was measured. The mean changes in the roughness profile of specimens were analyzed by a one-sample Kolmogorov-Smirnov test at a 0.05 significance level. Results: There was no significant difference in the mean surface roughness of specimens before and after the wear test (P > 0.05). The difference in the mean wear of five types of toothpaste was not significant either (P = 0.597). The mean changes in surface roughness were 0.0685 µm for Bencer charcoal, -0.0620 µm for RP charcoal, 0.0765 µm for Crest 7, 0.1137 µm for Colgate Optic White, and 0.1052 µm for Bencer fresh mint toothpaste. Conclusion: Numerous kinds of toothpaste investigated in this study did not reveal any difference in terms of wear index; however, more studies are needed to evaluate the effectiveness and efficiency of these types of toothpaste.

Protocol for mapping the variability in cell wall mechanical bending behavior in living leaf pavement cells.

Mechanical properties, size and geometry of cells, and internal turgor pressure greatly influence cell morphogenesis. Computational models of cell growth require values for wall elastic modulus and turgor pressure, but very few experiments have been designed to validate the results using measurements that deform the entire thickness of the cell wall. New wall material is synthesized at the inner surface of the cell such that full-thickness deformations are needed to quantify relevant changes associated with cell development. Here, we present an integrated, experimental-computational approach to analyze quantitatively the variation of elastic bending behavior in the primary cell wall of living Arabidopsis (Arabidopsis thaliana) pavement cells and to measure turgor pressure within cells under different osmotic conditions. This approach used laser scanning confocal microscopy to measure the 3D geometry of single pavement cells and indentation experiments to probe the local mechanical responses across the periclinal wall. The experimental results were matched iteratively using a finite element model of the experiment to determine the local mechanical properties and turgor pressure. The resulting modulus distribution along the periclinal wall was nonuniform across the leaf cells studied. These results were consistent with the characteristics of plant cell walls which have a heterogeneous organization. The results and model allowed the magnitude and orientation of cell wall stress to be predicted quantitatively. The methods also serve as a reference for future work to analyze the morphogenetic behaviors of plant cells in terms of the heterogeneity and anisotropy of cell walls.

Real-time conversion of tissue-scale mechanical forces into an interdigitated growth pattern.

The leaf epidermis is a dynamic biomechanical shell that integrates growth across spatial scales to influence organ morphology. Pavement cells, the fundamental unit of this tissue, morph irreversibly into highly lobed cells that drive planar leaf expansion. Here, we define how tissue-scale cell wall tensile forces and the microtubule-cellulose synthase systems dictate the patterns of interdigitated growth in real time. A morphologically potent subset of cortical microtubules span the periclinal and anticlinal cell faces to pattern cellulose fibres that generate a patch of anisotropic wall. The subsequent local polarized growth is mechanically coupled to the adjacent cell via a pectin-rich middle lamella, and this drives lobe formation. Finite element pavement cell models revealed cell wall tensile stress as an upstream patterning element that links cell- and tissue-scale biomechanical parameters to interdigitated growth. Cell lobing in leaves is evolutionarily conserved, occurs in multiple cell types and is associated with important agronomic traits. Our general mechanistic models of lobe formation provide a foundation to analyse the cellular basis of leaf morphology and function.