PubMed · 13965108
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G ASBOE-HANSEN. 1963. Connective tissue.. https://doi.org/10.1146/annurev.ph.25.030163.000353
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A dual-indentation creep and stress relaxation methodology was developed and validated for the material characterization of very soft biological tissue within the framework of the biphasic poroviscoelastic (BPVE) constitutive model. Agarose hydrogel, a generic porous medium with mobile fluid, served as a mechanical tissue analogue for validation of the experimental procedure. Indentation creep and stress relaxation tests with a solid plane-ended cylindrical indenter were performed at identical sites on a gel sample with dimensions large enough with respect to indenter size in order to satisfy an infinite layer assumption. A finite element (FE) formulation coupled to a global optimization algorithm was utilized to simultaneously curve-fit the creep and stress relaxation data and extract the BPVE model parameters for the agarose gel. A numerical analysis with artificial data was conducted to validate the uniqueness of the computational procedure. The BPVE model was able to successfully cross-predict both creep and stress relaxation behavior for each pair of experiments with a single unique set of material parameters. Optimized elastic moduli were consistent with those reported in the literature for agarose gel. With the incorporation of appropriately-sized indenters to satisfy more stringent geometric constraints, this simple yet powerful indentation methodology can provide a straightforward means by which to obtain the BPVE model parameters of biological soft tissues that are difficult to manipulate (such as brain and adipose) while maintaining a realistic in situ loading environment.
Periodontal plastic surgical techniques have evolved to meet the demands of today's dental patient. Free gingival grafts (FGGs), pedicle flaps, subepithelial connective tissue grafts (SCTGs), acellular dermal matrix (ADM) grafts, and guided tissue regeneration (GTR) have all been used to cover denuded root surfaces. FGGs have demonstrated inconsistent results. Pedicle flaps have provided consistent results, but adequate tissue must be present initially. ADM grafts have also demonstrated success, but long-term stability may be a problem. Presently, SCTGs and GTR should be considered the treatment of choice for root coverage. They are the most predictable with average root coverage as high as 98.9% and 92.3%, respectively.
The term internal neurolysis means removal of fibrotic tissue inside a nerve trunk. Unfortunately the term was used for procedures with complete isolation of fascicles with all consequences like damage of links between the fascicle and impairment of blood supply. The conclusion based on some negative experiences that all surgery within a nerve trunk has to be avoided cannot be accepted. Neurolysis within a nerve trunk, id est within the epineurium, is a step-wise procedure to decompress fascicles from a constricting fibrosis. It stops immediately if this aim is achieved or continues with resection and reconstruction if an irreparable damage is present. It is better to use terms that describe exactly what was done and abandon the ill-defined term "internal neurolysis". Fibrosis of the paraneurium remains outside the epineurium but causes the same consequences as fibrosis of the epineurium.