Experimental study of eigenstrains in temporomandibular joint discs using digital image analysis

Area of Science:

• Biomechanics
• Biomaterials Science
• Tissue Engineering

Background:

• The temporomandibular joint (TMJ) is crucial for daily function, and its disc is vital for load distribution.
• Dysfunction of the TMJ disc significantly impacts patient well-being.
• Understanding the TMJ disc's mechanical properties under physiological conditions is essential.

Purpose of the Study:

• To reveal and quantify residual stresses and eigenstrains within the temporomandibular joint disc.
• To evaluate the internal mechanical state of intact TMJ discs under hydrated, 37°C conditions.
• To analyze the effect of extraction on the disc's mechanical state.

Main Methods:

• Utilized global specimen size measurements and local digital image correlation (DIC) on porcine TMJ discs.
• Recorded approximately 30 images per disc over an hour to quantify deformation.
• Employed a backward time approach combined with an analytical model to assess eigenstrains.

Main Results:

• Quantified complex initial strain fields within TMJ disc specimens for the first time.
• Observed partial internal stress release via specimen self-deformation, with radial strain reaching ~13% in the outer ring.
• Deduced radial compression in the central disc area under physiological conditions to counteract daily loading stresses.

Conclusions:

• This research enhances the understanding of temporomandibular joint disc mechanics in vivo.
• Demonstrated the presence and quantification of residual stresses and eigenstrains.
• Highlighted the impact of tissue extraction on the mechanical state of TMJ discs.