PLLA and PDLLA Fillers: Linking Crystallinity and Mechanical Stability to Aggregation, Redispersion, and Collagen Formation.

BACKGROUND/AIM: outcomes. MATERIALS AND METHODS: Poly lactic acid/sodium hyaluronate composite fillers were analyzed by scanning electron microscopy, nuclear magnetic resonance, differential scanning calorimetry, and micro-compression. Dispersion-aggregation-redispersion in saline was quantified over 3 days by optical microscopy with circularity-based analysis. In SKH mice, 100 μl filler was injected subcutaneously. Projection volume was measured at baseline (day 0) and at 2, 4, 8, and 12 weeks post-injection using phase-shift rapid in vivo measurement of skin (PRIMOS). Tissue response was observed at the same time points using hematoxylin and eosin, Masson's trichrome, and macrophage immunofluorescence. RESULTS: , volume declined through week 4 then recovered. PLLA rebounded more uniformly with greater collagen area and weaker inflammatory and macrophage signals than PDLLA. CONCLUSION: PLLA crystallinity and mechanical robustness support re-dispersibility and more homogeneous collagen remodeling, whereas PDLLA aggregation is linked to heightened inflammation and reduced collagen deposition. Collectively, these findings suggest that maintaining microsphere integrity and dispersion is a key, actionable determinant of more uniform biostimulatory outcomes in PLA-based fillers.