Exploring the Rheology and Clinical Potential of Calcium Hydroxylapatite‐Hyaluronic Acid Hybrids

ABSTRACT Background Combining calcium hydroxylapatite‐carboxymethylcellulose (CaHA‐CMC) with hyaluronic acid (HA) products using Cohesive Polydensified Matrix (CPM) technology leverages the volumizing and hydrating effects of HA and draws upon the regenerative properties of CaHA‐CMC, providing a potentially synergistic approach in aesthetic filling treatments. Despite this potential, the rheological and physical properties of these hybrid fillers remain unreported. Objective To characterize the rheological properties of CaHA‐CMC blended with various CPM‐HA products and identify factors influencing their physical and clinical behavior. Methods Hybrid fillers were prepared by mixing CaHA‐CMC with different CPM‐HA products at varying ratios (1:1 to 1:4 syringe CaHA:syringe CPM). Rheological properties, including storage modulus ( G ′), loss modulus ( G ″), complex shear modulus ( G *), tan delta (tan δ ), and complex viscosity ( η *), were measured using an oscillatory rheometer. Extrusion force, cohesivity, stability, and axial strain ( ε a ) were also evaluated. Results The rheological properties of the hybrid fillers varied with the type of HA, mixing ratio, and crosslinking degree. Higher HA concentrations increased G ′, G ″, and η *, enhancing gel stiffness and resistance to deformation, while increased HA dilution and lower crosslinking favored spread and injectability. The addition of CaHA‐CMC to CPM‐HA products always increased the G ′ in a volume‐dependent manner. These properties were closely correlated with the fillers' performance in different tissue planes. Conclusions The properties of CaHA‐CMC and CPM‐HA hybrids influence their injection behavior and clinical outcomes. Understanding these factors can guide filler selection and application techniques to maximize safety, efficacy, and patient satisfaction in aesthetic treatments.