Objectives: The effects of reduced functional loads on mechanical integrity of interradicular bone (IB) within dentoalveolar joints (DAJ) in rats are investigated.

Methods: Four-week-old Sprague Dawley rats (N = 60) were divided into two groups; rats were either fed normal diet, which is hard-pellet food (HD) (N = 30) or soft-powdered chow (SD) (N = 30). DAJ biomechanics in situ and mechanical strains within IBs from 8 through 24 week old rats fed HD or SD were performed. Tension and compression-based mechanical strain profiles were mapped by correlating digital volumes of IBs at no load with the same IBs under load. IB material heterogeneity was identified by mapping IB cement lines and TRAP-positive multinucleated cells using histology, and site-specific mechanical properties using nanoindentation technique.

Results: Significantly decreased interradicular functional space, IB volume fraction and elastic modulus in the SD group compared with HD group were observed, and these trends varied with an increase in age. The elastic modulus values of IB from respective groups also illustrated significant heterogeneity. Both compressive and tension-based strains were localized at the coronal portion of the IB and the variation in strain profiles complemented material heterogeneity observed using histology and nanoindentation techniques.

Significance: Interradicular space and IB material-related mechanoadaptations in a DAJ are optimized to meet age-related functional demands albeit being pathologic. Results provided insights into regulation of functional loads as a plausible “therapeutic dose” to reverse adaptations in an attempt to regain functional competence of a dynamic DAJ with age.

Keywords: dentoalveolar joint; biomechanics; digital volume correlation; functional adaptation; interradicular bone, mechanoadaptation

Highlights:

• Reduced functional loads affect interradicular (IR) bone.
• Biomechanics in situ with X-ray and DVC can identify differences in functional adaptation of the DAJ.
• Form- and material-related adaptations of IR bone are age-specific.
• “Prescribed mechanical dose” could maintain functional competence of the DAJ.