Dynamic mechanical properties of oral mucosa: comparison with polymeric soft denture liners.

The purpose of this work was to characterize the viscoelastic behaviour of oral mucosa and compare it with the dynamic mechanical properties of different soft liners. For this purpose, a sample of pig oral mucosa and six commercialized soft liner samples have been investigated. A comparison was also carried with the first suitable hard rubber for dental prosthetics: vulcanite. Creep recovery (CR) and dynamic mechanical analysis (DMA)have been used to determine the mechanical modulus of oral mucosa and soft liners respectively. The Poisson ratio is used to compare mucosa bulk modulus and soft liner shear modulus. The biomechanical concept of conventional complete dentures needs a good adjustment of dynamic mechanical impedance between the base and oral mucosa. The viscoelastic mechanical property of the oral mucosa as a referent biopolymer has been confirmed in vitro. The modulus value, adjusted for old patients in physiological conditions, is in the order of 3 MPa. This study underlines the plasticization effect of absorbed water on the mechanical properties of the underlying tissue. This study allows us to define some characteristics of the most adapted biomaterial according to the clinical exigency. The required biomaterial must display the following properties: compatibility and chemical resistance with biological environment perpetuated mechanical properties during physiological conditions and clinical use, good adjustment of dynamic mechanical impedance with supporting mucosa and easy sample processing

L’écosystème buccal chez le patient âgé

La bouche est une cavité naturelle complexe qui forme le segment initial du tube digestif. Elle est un acteur essentiel des fonctions vitales que sont la nutrition, le langage et la communication. L’ensemble de la bouche (dents, parodonte, muqueuses, langue) est constamment hydraté et lubrifié par la salive. À tout âge, un équilibre s’établit entre la prolifération bactérienne, le flux salivaire et la réponse tissulaire : c’est l’écosystème buccal. La régulation de cet écosystème participe à la protection du complexe buccal contre les pathologies inflammatoires et infectieuses courantes (caries, gingivites, parodontopathies,candidoses). Chez les patients âgés, la modification du flux salivaire, l’apparition de pathologies spécifiques (caries radiculaires, absence de dents, parodontopathies. . .), les conditions locales (présence de prothèses amovibles), le développement de pathologies générales telles que le diabète, l’hypertension, la baisse des défenses immunitaires, la négligence de l’hygiène quotidienne sont autant d’éléments qui vont déséquilibrer l’écosystème buccal, favoriser la formation du biofilm (plaque bactérienne) et fragiliser les tissus bucco-dentaires. Le maintien de cet écosystème est essentiel pour le patient âgé : il lui permet de s’alimenter dans de bonnes conditions et ainsi prévenir les risques de dénutrition. Les auteurs décrivent la physiopathologie buccale (flore buccale, sécrétion salivaire) et les stratégies à adopter pour préserver l’équilibre buccal chez le patient âgé

Conformational and thermal characterization of a synthetic peptidic fragment inspired from human tropoelastin: Signature of the amyloid fibers

Objectives : This work deals with the conformational and thermal characterization of a synthetic peptide (S4) released during the proteolysis of human tropoelastin by the matrix metalloproteinase-12 that was shown to form amyloid-like fibres under certain conditions. Materials and methods : S4 peptides were synthesized by solid-phase methodology and aggregated in solution at 80 8C. Fourier transform–infrared spectroscopy (FT–IR) was used to access the secondary structure. Thermal characterization was performed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results : The DSC study of the soluble linear peptide S4 in solution in TBS reveals the irreversible aggregation into amyloid fibres. FT–IR, DSC and TGA analyses performed on freeze-dried samples evidence differences between the linear peptide and its associated amyloid-like fibres, both on the conformation and the physical structure. When S4 peptides are aggregated, the prominent conformation scanned by FT–IR is the cross b-structure, corresponding to TGA to an increase of the thermal stability. Moreover, the DSC thermograms of S4 fibres are characteristic of a highly ordered structure, in contrast to the DSC thermograms of S4 linear peptides, characteristic of an amorphous structure. Finally, the DSC analysis of differently hydrated S4 fibres brings to the fore the specific thermal answer of the wet interfaces of the cross b-fibres. Conclusion : FT–IR and thermal techniques are well suited to evidence conformational and structural differences between the soluble peptide and its amyloid form

Identification of ageing biomarkers in human dermis biopsies by thermal analysis (DSC) combined with Fourier transform infrared spectroscopy (FTIR/ATR)

Background/purpose : The purpose of this clinical study was to identify suitable biomarkers for a better understanding of the molecular and organizational changes in human dermis during intrinsic and extrinsic ageing. Methods : Sun-exposed and non-exposed skin biopsies were collected from twenty-eight women devised in two groups (20-30 and ≥60 years old). The hydric organization and thermal transitions were determined by Differential Scanning Calorimetry (DSC). Fourier Transform Infrared spectroscopy (FTIR) was used to identify the absorption bands of the dermis and to quantify the different absorbance ratio. Results : The amounts of total, freezable and unfreezable water were determined. A significant increasing amount of freezable water is evidenced in sun-exposed area skin of aged group compared with young group (P=.0126). Another significant effect of extrinsic ageing (P=.0489) is the drastic decrease of fibrillary collagen, the main protein component of dermis. The only significant effect of intrinsic ageing (P=.0184) is an increase of the heat-stable fraction of collagens in dermis. Conclusion : DSC and FTIR are well-suited techniques to characterize human skin, giving accurate results with a high reproducibility. The combination of these techniques is useful for a better understanding of human skin modifications with intrinsic and extrinsic ageing

Thermal and vibrational biomarkers of porcine oral mucosa

The aim of this study was to develop an experimental protocol to determine specific and reproducible biomarkers of the oral mucosa using a combination of thermal and vibrational techniques. This works deals with the characterization of mandible and maxilla biopsies, 4 mm by diameter, from porcine mucosa in both the hydrated and lyophilized state. Thermogravimetric analysis was carried out to measure hydration level of these tissues and to define the onset of proteins degradation. By differential scanning calorimetry, thermal transitions of water and proteins were evidenced and used to quantify the hydric organization (unfreezable/freezable waters) and to evaluate collagen thermal stability (through denaturation parameters). To complete this protocol, Fourier transform infrared spectroscopy was also used to identify specific vibrational signatures of the main layers of oral mucosa. Total and freezable water amounts are significantly higher in maxilla, due to morphological differences at the macroscopic level, while unfreezable water amount is independent upon localization. Denaturation temperature (in peculiar the temperature corresponding to 50% of collagen denaturation) largely increases with dehydration. This temperature denaturation is also dependent upon localization whatever the hydration, possibly due to differences in cross-links or interactions with other proteins of oral mucosa. The acquisition of thermal and vibrational biomarkers of oral mucosa will contribute to a better knowledge of these soft tissues for further studies on aging

Evaluation of functional arterial spin labeling data using a perfusion template

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Using remote sensing to map larval and adult populations of Anopheles hyrcanus (Diptera: Culicidae) a potential malaria vector in Southern France

Although malaria disappeared from southern France more than 60 years ago, suspicions of recent autochthonous transmission in the French Mediterranean coast support the idea that the area could still be subject to malaria transmission. The main potential vector of malaria in the Camargue area, the largest river delta in southern France, is the mosquito Anopheles hyrcanus (Diptera: Culicidae). In the context of recent climatic and landscape changes, the evaluation of the risk of emergence or re-emergence of such a major disease is of great importance in Europe. When assessing the risk of emergence of vector-borne diseases, it is crucial to be able to characterize the arthropod vector's spatial distribution. Given that remote sensing techniques can describe some of the environmental parameters which drive this distribution, satellite imagery or aerial photographs could be used for vector mapping.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe