Comparative Rheology of Hyaluronic Acid Fillers, Poly-l-lactic Acid, and Varying Dilutions of Calcium Hydroxylapatite.

ABSTRACT

Background: This study examines the rheological properties of various dermal fillers, including hyaluronic acid (HA) fillers, poly-L-lactic acid (PLLA), and calcium hydroxylapatite-carboxymethylcellulose (CaHA-CMC) gels, with a particular focus on the impact of aqueous dilution on CaHA-CMC's rheology and potential clinical implications. Methods: Using standardized rheological analysis, we measured and compared the elastic modulus (G'), viscous modulus (G″), and the tan δ values of different dilutions of CaHA-CMC against published values of HA and PLLA fillers. The study aimed to determine the potential clinical use of application-specific CaHA-CMC hydrogel dilutions along a range of gel strength and cohesion for hydrogel fillers in current use. Results: The findings demonstrate that CaHA-CMC's rheological properties can be tailored across a broad spectrum of viscoelastic parameters through titrated dilution, ranging from high elasticity to low cohesion. Varying the aqueous volume allows for the rheomodulation of CaHA-CMC, potentially matching the entire rheological spectrum of HA fillers and suggesting an expanded range of clinical applications. Conclusions: The versatility of CaHA-CMC through dilution may offer a customizable approach for clinical applications, providing practitioners with the ability to fine-tune the properties of fillers to meet specific patient needs and treatment goals. This study lays the groundwork for the potential future use of filler dilutional rheomodulation in clinical practice, tailored to patient- and application-specific needs.