Structure-Function Relationships of the Temporomandibular Joint in Response to Altered Loading

Area of Science:

• Biomedical Engineering
• Oral and Maxillofacial Surgery
• Musculoskeletal Research

Background:

• The mandibular condylar fibrocartilage is crucial for jaw function and adapts to mechanical loads.
• Understanding the effects of altered loading on this tissue is vital for treating temporomandibular joint disorders.

Purpose of the Study:

• To investigate the impact of decreased occlusal loading (DOL) and subsequent reloading (RL) on mandibular condylar fibrocartilage structure and bite force in mature male mice.

Main Methods:

• Skeletally mature male mice underwent normal loading (NL), DOL, or DOL followed by RL.
• Histomorphometry, cell metabolic activity, chondrogenic marker gene expression, and bite force tests were conducted.

Main Results:

• DOL led to increased apoptosis, reduced fibrocartilage thickness, and decreased expression of hypertrophic chondrocyte markers (Indian hedgehog, collagen type X).
• A significant decrease in bite force was observed following DOL.
• RL partially restored chondrogenic markers and bite force to levels comparable to NL, but did not recover fibrocartilage thickness.

Conclusions:

• Decreased occlusal loading induces atrophy in the mandibular condylar fibrocartilage's hypertrophic cell layer in mature mice.
• This atrophy is associated with a reduction in bite force.
• While reloading can partially reverse functional deficits, it does not fully restore cartilage thickness.