Morphological and Rheological Analysis of an Injectable Calcium Hydroxylapatite Dermal Filler with Lattice-Pore Surface Architecture.

Abstract

Background: Hydroxylapatite is a biocompatible calcium-phosphate ceramic used in regenerative biomaterials. Calcium hydroxylapatite (CaHA) fillers combine immediate mechanical support with subsequent extracellular matrix remodeling, and their material behavior depends on microsphere morphology, mineral composition, carrier interactions, and rheology. Objectives: To determine whether a CaHA formulation prepared using Lattice Pore Formation technology (Facetem) exhibits a distinct and internally consistent material profile across microsphere geometry, lattice-pore surface architecture, mineral composition, formulation-level sedimentation, and rheological behavior across dilution ratios, with selected morphology and sedimentation characteristics compared with Radiesse. Methods: Facetem (marketed in the Republic of Korea as DCLASSY) was evaluated as the test product, with Radiesse used as the comparator product. Microspheres were examined using field-emission scanning electron microscopy and laser-diffraction particle-size analysis. Surface morphology was assessed before and after 12 weeks of phosphate-buffered saline (PBS) incubation. Mineral composition was evaluated using X-ray diffraction and inductively coupled plasma optical emission spectroscopy. Extrusion continuity and sedimentation after saline dilution were evaluated, and rheological properties were measured across eight dilution ratios using saline, non-cross-linked hyaluronic acid, and semi-cross-linked hyaluronic acid. Results: Facetem had a mean particle diameter of 34.60 μm, with higher circularity (0.95 versus 0.88) and roundness (0.96 versus 0.85), a lower aspect ratio, and fewer particles below 20 μm (2.10% versus 14.50%) than Radiesse. Micrograin domains formed a lattice-pore surface that showed morphological changes after 12 weeks of PBS incubation while the spherical contour remained recognizable. Hydroxylapatite represented 99.09% of the mineral phase, with a Ca/P ratio of 1.67. Facetem extruded as a continuous strand and showed greater supernatant clarification after dilution. Storage modulus declined with dilution, and semi-cross-linked hyaluronic acid retained more elastic resistance than saline at equivalent ratios. Conclusions: Facetem demonstrated a consistent microsphere population, an organized lattice-pore surface, hydroxylapatite stoichiometry, and diluent-dependent rheology. The integrated analysis defines its physicochemical profile; the PBS findings should be interpreted as morphological stability under non-biological buffer conditions rather than in vivo degradation.