Gender-specific differences in temporomandibular retrodiscal tissues of the goat

Neurobiology of estrogen status in deep craniofacial pain

Pain in the temporomandibular joint (TMJ) region often occurs with no overt signs of injury or inflammation. Although the etiology of TMJ-related pain may involve multiple factors, one likely risk factor is female gender or estrogen status. Evidence is reviewed from human and animal studies, supporting the proposition that estrogen status acts peripherally or centrally to influence TMJ nociceptive processing. A new model termed the "TMJ pain matrix" is proposed as critical for the initial integration of TMJ-related sensory signals in the lower brainstem that is both modified by estrogen status, and closely linked to endogenous pain and autonomic control pathways.

A Surface–Regional and Freeze–Thaw Characterization of the Porcine Temporomandibular Joint Disc

The temporomandibular joint (TMJ) disc is a central element in several TMJ disorders. Tissue-engineered TMJ disc replacements may alleviate discomfort associated with TMJ disorders; however, prior to developing a replacement, a thorough understanding of the native disc must be attained. Toward this end, we developed an unconfined compression, incremental stress relaxation viscoelastic model which simultaneously incorporates the strain increment magnitude and total deformation in the stress relaxation solution. This multiple strain step model was fit to stress relaxation data from (i) 80 test sites from eight porcine TMJ discs for the purposes of a surface-regional characterization and (ii) 30 test sites from five porcine TMJ discs for the purposes of a freeze-thaw characterization. The model estimated viscoelastic parameters accurately and surface-regional variations were detected throughout the TMJ disc. Regionally, the medial and anterior regions have the largest relaxation moduli, and the posterior and anterior regions have the largest instantaneous moduli. The inferior surface was found to have higher instantaneous modulus values than the superior surface. Furthermore, material properties were retained over five freeze-thaw cycles. The results of this study allow for the creation of design and validation criteria for future engineering efforts and shed light on the disc's role in TMJ function and dysfunction.

Viscoelastic properties of bovine retrodiscal tissue under tensile stress-relaxation

To test the hypothesis that the condylar part of the retrodiscal tissue of the temporomandibular joint exhibits resistance to tensile force, we investigated its viscoelastic properties and stress-relaxation behavior under tension. Ten specimens were tested. Stress-relaxation tests were conducted from four different initial stress levels. The tissue exhibited a non-linear stress-strain relationship, which could be represented by a bilinear relation of two line segments. The stress-relaxation curves showed a marked drop in load during the initial 10 s and after 2 min the stress reached an almost steady non-zero level. This feature can be well represented by Kelvin's model. It is concluded that the condylar part of the retrodiscal tissue (a) exhibits a non-linear strain-dependent viscoelastic behavior (b), has a great capacity for energy dissipation and resistance to tensile forces, and (c) contributes to maintain the position of the disc relative to the condyle during jaw closing.