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Force Application (force + application)

Distribution by Scientific Domains

Medical Sciences	71%
Chemistry	28%

Selected Abstracts

The Response of Skin to Applied Stress: Investigation of Bitemark Distortion in a Cadaver Model,

JOURNAL OF FORENSIC SCIENCES, Issue 1 2010
Mary A. Bush D.D.S.
Abstract:, Knowledge of distortional properties of skin is important in bitemark analysis. Thus, the response of skin to stress from bites was investigated. Four sets of models were created from the dentition of one individual. Anterior teeth were systematically removed to vary contact surface area. A biting apparatus was constructed with an integrated load cell. Forty-six bites were created perpendicular to Langer lines on six cadavers. Rate of force application and bite pressure were controlled. Metric/angular measurement and hollow volume overlays were employed. Distortion produced by each dentition was calculated and assessed. Results showed that as teeth impressed loose tissue, mesial/distal distance increased, angles of rotation flattened, and inter-canine distance lengthened. An opposite effect was seen in tight tissue. When the surface area of the dentition was reduced, a mixture of these effects was observed. Conclusions indicated that stiffness of the tissue was the most important variable in bitemark distortion. [source]

Sensory-motor function of human periodontal mechanoreceptors,

JOURNAL OF ORAL REHABILITATION, Issue 4 2006
M. TRULSSON
summary, Natural teeth are equipped with periodontal mechanoreceptors that signal information about tooth loads. In the present review, the basic force-encoding properties of human periodontal receptors will be presented along with a discussion about their likely functional role in the control of human mastication. Microneurographic recordings from single nerve fibres reveal that human periodontal receptors adapt slowly to maintained tooth loads. Most receptors are broadly tuned to the direction of force application, and about half respond to forces applied to more than one tooth. Populations of periodontal receptors, nevertheless, reliably encode information about both the teeth stimulated, and the direction of forces applied to the individual teeth. Information about the magnitude of tooth loads is made available in the mean firing rate response of periodontal receptors. Most receptors exhibit a markedly curved relationship between discharge rate and force amplitude, featuring the highest sensitivity to changes in tooth load at very low force levels (below 1 N for anterior teeth and 4 N for posterior teeth). Thus, periodontal receptors efficiently encode tooth load when subjects contact and gently manipulate food using the teeth. It is demonstrated that signals from periodontal receptors are used in the fine motor control of the jaw and it is clear from studies of various patient groups (e.g. patients with dental implants) that important sensory-motor functions are lost or impaired when these receptors are removed during the extraction of teeth. [source]

Expression of c-Fos protein in the trigeminal nuclear complex resulting from quantified force application to the rat molar

JOURNAL OF ORAL REHABILITATION, Issue 11 2003
M. Watanabe
summary, This study was conducted to investigate the expression and distribution of c-Fos-like immunoreactive neurones (Fos-neurones), in the rat trigeminal sensory nuclear complex, produced by mechanical forces with various magnitudes and durations applied to the left upper first molar. The magnitudes of forces applied to the tooth were 25, 50 and 100 g and the duration was 2 h. A quantified force of 100 g was also applied to the upper molar for varying durations [short-time (1,2 min)], 2, 4, 8 and 12 h. Fos-neurones distributed in the bilateral superficial laminae of the subnucleus caudalis, and the ipsilateral dorsomedial part of subnucleus oralis (Sp5Odm). The number of Fos-neurones increased in the subnucleus caudalis (Sp5C) according to the force magnitude. In the Sp5C, the number of Fos-neurones exhibited maximum level, 2 or 4 h after the application. In the Sp5Odm, however, the number of Fos-neurones reached the maximum level at 8 h. These data suggest that the change in the number of nociceptive neurones in Sp5C reflect changes in encoding the magnitude of force to tooth, and that the nature of pain response to orthodontic forces might have some relation to the delayed expression of c-Fos protein in the Sp5Odm. [source]

Differentiation and functions of osteoclasts and odontoclasts in mineralized tissue resorption

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2003
Takahisa Sasaki
Abstract The differentiation and functions of osteoclasts (OC) are regulated by osteoblast-derived factors such as receptor activator of NFKB ligand (RANKL) that stimulates OC formation, and a novel secreted member of the TNF receptor superfamily, osteoprotegerin (OPG), that negatively regulates osteoclastogenesis. In examination of the preosteoclast (pOC) culture, pOCs formed without any additives expressed tartrate-resistant acid phosphatase (TRAP), but showed little resorptive activity. pOC treated with RANKL became TRAP-positive OC, which expressed intense vacuolar-type H+ -ATPase and exhibited prominent resorptive activity. Such effects of RANKL on pOC were completely inhibited by addition of OPG. OPG inhibited ruffled border formation in mature OC and reduced their resorptive activity, and also induced apoptosis of some OC. Although OPG administration significantly reduced trabecular bone loss in the femurs of ovariectomized (OVX) mice, the number of TRAP-positive OC in OPG-administered OVX mice was not significantly decreased. Rather, OPG administration caused the disappearance of ruffled borders and decreased H+ -ATPase expression in most OC. OPG deficiency causes severe osteoporosis. We also examined RANKL localization and OC induction in periodontal ligament (PDL) during experimental movement of incisors in OPG-deficient mice. Compared to wild-type OPG (+/+) littermates, after force application, TRAP-positive OC were markedly increased in the PDL and alveolar bone was severely destroyed in OPG-deficient mice. In both wild-type and OPG-deficient mice, RANKL expression in osteoblasts and fibroblasts became stronger by force application. These in vitro and in vivo studies suggest that RANKL and OPG are important regulators of not only the terminal differentiation of OC but also their resorptive function. To determine resorptive functions of OC, we further examined the effects of specific inhibitors of H+ -ATPase, bafilomycin A1, and lysosomal cysteine proteinases (cathepsins), E-64, on the ultrastructure, expression of these enzymes and resorptive functions of cultured OC. In bafilomycin A1-treated cultures, OC lacked ruffled borders, and H+ -ATPase expression and resorptive activity were significantly diminished. E-64 treatment did not affect the ultrastructure and the expression of enzyme molecules in OC, but significantly reduced resorption lacuna formation, by inhibition of cathepsin activity. Lastly, we examined the expression of H+ -ATPase, cathepsin K, and matrix metalloproteinase-9 in odontoclasts (OdC) during physiological root resorption in human deciduous teeth, and found that there were no differences in the expression of these molecules between OC and OdC. RANKL was also detected in stromal cells located on resorbing dentine surfaces. This suggests that there is a common mechanism in cellular resorption of mineralized tissues such as bone and teeth. Microsc. Res. Tech. 61:483,495, 2003. © 2003 Wiley-Liss, Inc. [source]

Pressure simulation of orthodontic force in osteoblasts: a pilot study

ORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 1 2004
U. Baumert
Structured Abstract Authors , Baumert U, Golan I, Becker B, Hrala BP, Redlich M, Roos HA, Reichenberg E, Palmon A, Müßig D Objectives , To elucidate the RUNX2 gene expression induction in human osteoblasts after mechanical loading. Design , Using a stringent pulse-chase protocol human osteoblasts were exposed to centrifugal pressure force for 30 and 90 min. Untreated control cells were processed in parallel. Before, and at defined times after centrifugation, total RNA was isolated. RUNX2 gene expression was measured using real-time quantitative reverse transcriptase polymerase chain reaction. The stress/control ratio was used to illustrate possible stimulatory or diminishing effects of force application. Results , Immediately after 30 min of force application the RUNX2 gene expression was induced by a factor of 1.7 ± 0.14 as compared with the negative control. This induction decreased rapidly and reached its pre-load levels within 30 min. Longer force applications (up to 90 min) did not change the RUNX2 gene expression. Conclusion , In mature osteoblasts centrifugal pressure force stimulates RUNX2 gene expression within a narrow time frame: loading of mature cells results in a temporary increase of RUNX2 expression and a fast downregulation back to its pre-load expression level. With this pilot study the gene expression behavior after mechanical stimuli could be determined with a simple laboratory setup. [source]

Polymeric Actuators for Biological Applications

CHEMPHYSCHEM, Issue 12 2007
Avishay Pelah Dr.
Abstract To shed light on the role of cell rheology and mechanotransduction in various physiological and disease states, different techniques of force application, such as optical tweezers and deformable substrates, are employed. In this present paper we describe a new approach for the deformation of cells based on the temperature-sensitive polymer poly(N-isopropylacrylamide), PNIPAM. In response to temperature changes, PNIPAM gels undergo extensive and reversible changes in volume that allow them to be used as actuators for stretching and compressing cells and tissues. Herein we focus mainly on our experience with the deformation of red blood cells as proof of principle, and demonstrate the wealth of possibilities such stimuli-responsive materials may offer as actuators. [source]