Mechanical properties of human oral mucosa tissues are site dependent: A combined biomechanical, histological and ultrastructural approach.

To investigate load-deformation properties of Thiel-embalmed human oral mucosa tissues and to compare three different anatomical regions in terms of mechanical, histological and ultrastructural characteristic with focus on the extracellular matrix. Thirty specimens from three different regions of the oral cavity: attached gingiva, buccal mucosa and the hard palate were harvested from two Thiel-embalmed cadavers. Mechanical properties were obtained, combining strain evaluation and digital image correlation in a standardised approach. Elastic modulus, tensile strength, strain at maximum load and strain to failure were computed and analysed statistically. Subsamples were also analysed using scanning electron microscopy (SEM) and histological analysis. The highest elastic modulus of 37.36 ± 17.4 MPa was found in the attached gingiva group, followed by the hard palate and buccal mucosa. The elastic moduli of attached gingiva differed significantly to the buccal mucosa (p = .01) and hard palate (p = .021). However, there was no difference in the elastic moduli between the buccal mucosa and hard palate (p > .22). The tensile strength of the tissue samples ranged from 1.54 ± 0.5MPa to 3.81 ± 0.9 MPa, with a significant difference between gingiva group and buccal mucosa or hard palate (p = .001). No difference was found in the mean tensile strength between the buccal mucosa and hard palate (p = .92). Ultrastructural imaging yielded a morphological basis for the various mechanical properties found intraorally; the attached gingiva showed unidirectional collagen fibre network whereas the buccal mucosa and hard palate showed multi-directional network, which was more prone to tension failure and less elasticity. This is the first study assessing the various morphological-mechanical relationships of intraoral soft tissues, utilising Thiel-embalmed tissues. The findings of this study suggest that the tissues from different intraoral regions showed various morphological-mechanical behaviour which was also confirmed under the SEM and in the histological analysis.

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