Biomechanical and biochemical outcomes of porcine temporomandibular joint disc deformation

Abstract

Objective The structure-function relationship in the healthy temporomandibular joint (TMJ) disc has been well established, however the changes in dysfunctional joints has yet to be systematically evaluated. Due to the poor understanding of the etiology of temporomandibular disorders (TMDs) this study evaluated naturally occurring degenerative remodeling in aged female porcine temporomandibular joint (TMJ) discs in order to gain insight into the progression and effects on possible treatment strategies of TMDs. Design Surface and regional biomechanical and biochemical properties of discal tissues were determined in grossly deformed (≥ Wilkes Stage 3) and morphologically normal (≤ Wilkes Stage 2) TMJ discs. Results Compared to normal disc structure the deformed discs lacked a smooth biconcave shape and characteristic ECM organization. Reduction in tensile biomechanical integrity and increased compressive stiffness and cellularity was found in deformed discs. Regionally, the posterior and intermediate zones of the disc were most frequently affected along with the inferior surface. Conclusions The frequency of degeneration observed on the inferior surface of the disc (predominantly posterior), suggests that a disruption in the disc-condyle relationship likely contributes to the progression of joint dysfunction more than the temporodiscal relationship. As such, the inferior joint space may be an important consideration in early clinical diagnosis and treatment of TMDs, as it is overlooked in techniques performed in the upper joint space, including arthroscopy and arthrocentesis. Furthermore, permanent damage to the disc mechanical properties would limit the ability to successfully reposition deformed discs, highlighting the importance of emerging therapies such as tissue engineering.

Catabolic changes of rat temporomandibular joint discs induced by unilateral anterior crossbite

“…Normally, the TMJ disc has functions in absorbing and redistributing stress . The degraded disc, like those observed in the present study and those in the rat with a surgical malocclusion or in patients with internal derangement, should be poorly qualified that are less flexible when under compression thus are less adaptable when reposition or rebound during movements . That makes the structural and functional relationship of the disc‐condyle complex easier to be broken down, which is often observed in TMJs with disc displacement …”

Tensile biomechanical properties of human temporomandibular joint disc: Effects of direction, region and sex

“…Compared to the available literature, human TMJ discs have a lower Young’s Modulus compared to bovine tissue and porcine tissue from older breeder sows (Matuska et al, 2016; Tanaka et al, 2001). Young’s Modulus for human TMJ discs was most similar to bovine TMJ discs, compared to older breeder sows, suggesting the proposed porcine ageing model for TMJDs may not be appropriate (Matuska et al, 2016).…”

“…Compared to the available literature, human TMJ discs have a lower Young’s Modulus compared to bovine tissue and porcine tissue from older breeder sows (Matuska et al, 2016; Tanaka et al, 2001). Young’s Modulus for human TMJ discs was most similar to bovine TMJ discs, compared to older breeder sows, suggesting the proposed porcine ageing model for TMJDs may not be appropriate (Matuska et al, 2016). Instantaneous and Relaxed Moduli were similar to that reported for typical porcine TMJ discs (Detamore and Athanasiou, 2003), however Instantaneous and Relaxed Moduli were an order of magnitude lower from the present study compared to the only other study using human TMJ disc specimens (Tanaka et al, 2000).…”

“…However, it has been reported that strain rate effects for collagen tissues, including the TMJ disc, are negligible (Beatty et al, 2001; Fung, 1993). It is expected that the strain rate used in this study is similar to physiologic strain rates, and has been used previously (Beatty et al, 2001; Detamore and Athanasiou, 2003; Matuska et al, 2016). The range of strain implemented in this study may be beyond physiologic limits suggested for the TMJ disc, less than 20% (Beek et al, 2001; Koolstra and van Eijden, 2005, 2007).…”

“…Detamore and Athanasiou (2003) reported increased elastic moduli, toughness and strength in varying directions and regions of porcine disc, corresponding to differences in collagen fiber orientation. Young’s Modulus also shows direction and region dependent affects (Matuska et al, 2016; Shengyi and Xu, 1991; Tanne et al, 1991). However, the available literature provides an incomplete tensile profile of the TMJ disc, relying heavily upon animal tissue and reporting a wide range of properties.…”