Divergent trajectories of structural accrual and matrix-level mechanical properties during alveolar bone maturation.

Abstract

Alveolar bone, a highly dynamic tissue supporting dentition, undergoes a poorly characterized transition from growth to maturity that is critical for orthodontic treatment and periodontal risk assessment. We integrated micro‑CT (μCT), nanoindentation creep modeling, and RNA sequencing to define structural, mechanical, and transcriptomic signatures of this transition in rats at 12 and 24 weeks, using the molar‑bearing alveolar region (M1) and the mandibular notch as a non‑alveolar reference. μCT revealed progressive cortical and trabecular bone accrual at 24 weeks, with trabeculae shifting from rod‑like to plate‑like configurations via lateral expansion. Nanoindentation revealed a site-specific decreasing trend in elastic modulus at M1, which was absent at the mandibular notch, suggesting a regional divergence of local mechanics from bulk mineralization. Time‑dependent creep analysis demonstrated that fast retardation time τ₁ tended to increase at the notch but remained stable at M1, while long‑timescale τ₂ showed a similar upward tendency at the notch, suggesting a viscosity‑related shift in viscoelastic behavior confined to the notch. Transcriptomically, 24‑week alveolar bone exhibited downregulation of genes related to bone matrix assembly and mineralization, alongside observed enrichment of senescence and inflammatory pathways. These molecular changes offer biological context for the observed divergence between continued structural bone accrual and altered matrix-level mechanical quality. Collectively, our findings demonstrate that alveolar bone maturation involves distinct trajectories of structural accrual and site-specific matrix alterations, providing important considerations for the biomechanical assessment of dynamic skeletal tissues.