A Randomized Clinical Trial Comparing Pure Hyaluronic Acid to the Hyaluronic Acid–Calcium Hydroxylapatite Combination for Temporal Volumization

Abstract Background Hyaluronic acid (HA) and calcium hydroxylapatite (CaHA) are commonly used for facial volumization, with HA offering hydration and reversibility, whereas CaHA provides structural support and collagen biostimulation. Recently, a combination of HA and CaHA has been proposed to enhance both immediate volumization and long-term tissue remodeling. However, its efficacy for volume retention remains unclear. Objectives In this study, the authors aim to compare the volumetric retention and clinical outcomes of HA alone vs a manually prepared HA–CaHA mixture in the temporal region over a 90-day follow-up. Methods A randomized controlled trial included 20 patients (40 hemifaces) treated with either 0.5 mL of HA alone (G1) or a 40% HA and 60% CaHA mixture (G2). Fillers were injected subcutaneously using a 22 G cannula with a fan technique. Volumetric changes were assessed through 3-dimensional stereophotogrammetry, and the Allergan Temple Scale (ATS) evaluated qualitative outcomes. Results Both groups showed significant ATS score improvements over time (P < .001), but volumetric analysis demonstrated greater retention in G1 (0.231 ± 0.255 mL) compared with G2 (0.028 ± 0.135 mL, P = .016). Conclusions The hypothesized synergy of the HA–CaHA combination was not observed. HA alone provided superior long-term volumization, suggesting that manual HA–CaHA mixing may alter filler performance. Further studies should explore premixed formulations and optimize treatment protocols. Level of Evidence: 2 (Therapeutic)