Parametric analysis of the influence of texture on human dental surface hardness.

Tooth wear is one of the dental abnormalities commonly found in different populations. The objective of this work is to conduct a parametric analysis to evaluate the texture influence on the human dental surface hardness, considered here as the ratio between contact force and contact area, obtained through homogenization procedure. A code was implemented using the statistical package R for parametric analysis. The computational approach consists of three routines: numerical generation of surfaces, based on Pearson system; the second, a script coupled to the Finite Element program Abaqus, for the modelling of the micro-contacts; the third for homogenization and statistical analysis of results. The average curvature of the roughness exerts the greatest influence on the surface hardness. The parameters that most influence the development of contact forces are kurtosis followed by skewness.

Spatiotemporal pattern of glucose in a microfluidic device depend on the porosity and permeability of the medium: A finite element study.

BACKGROUND: Glucose plays an important role as a source of nutrients and influence cellular processes such as differentiation, proliferation and migration. In vitro models based on microfluidic devices represent an alternative to study several biological processes in a more reproducible and controllable method compared to in vivo models. Glucose concentration across a microfluidic chip and its behavior in experimental conditions is not completely understood. OBJECTIVE: This paper investigated the spatiotemporal distribution of glucose across the hydrogel inside a microfluidic chip. The influence of different parameters, boundary and initial conditions of experiments on glucose concentration was studied. METHODS: A finite element model using a two dimensional geometry was developed. With this model, patterns of glucose concentration were investigated for different combinations of flow rate of culture medium, permeability and porosity of the medium. Patterns were also studied for two hydrogels made of collagen type I and fibrin with different initial and boundary conditions for pressure and glucose concentration. RESULTS: Porosity influenced significantly on the chemical gradients generated when interstitial fluid flow was null or neglectable. A difference in concentration lower than 15% was obtained at the input of microchamber and after 90 min, when porosity changed from 0.5 to 0.99. In addition, no significant effects of modifications in permeability were observed. Regarding the collagen and fibrin matrices, in the presence of a pressure gradient of 40 Pa, the permeability significantly influenced on the concentration gradients generated. CONCLUSIONS: Porosity influences importantly on patterns when diffusion is the main transport mechanism. Permeability is the most influencing parameter when a fluid flow is present. Common insertion rates of culture medium does not significantly modify the patterns of glucose inside the chips. Thus, new experiments must consider the impact of such parameters on the distribution and the time span that nutrients occupy the medium. To better contribute with experimental trials, other studies involving cell-cell and cell-extracellular matrix interactions, and different chip geometries should be developed. The results of the present work could assist to develop specific systems for experimentation, to design new experiments and to improve the analysis of the obtained results.