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

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 (εa) 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.