Calcium hydroxylapatite (CaHA): what the term means
Medically reviewed by Dr Sin Yong · Last reviewed · 3 min read
Published 13 October 2026 · Reviewed by Dr Sin Yong
Calcium hydroxylapatite (CaHA) is a biocompatible mineral, chemically similar to the mineral in bone and teeth, used in aesthetic medicine as microspheres of 25 to 45 µm suspended in a gel carrier. CaHA is the material in Radiesse. Undiluted, it gives volume on the day and stimulates collagen afterwards; diluted, it becomes a skin-quality treatment for the face, neck and body. Hyaluronidase does not dissolve either form.
Key facts
Material
About 30% CaHA microspheres of 25–45 µm in about 70% aqueous gel of sodium carboxymethylcellulose, glycerin and water
Product
Radiesse (Merz); Radiesse (+) adds lidocaine
Two uses
Undiluted for volume and contour; diluted for skin quality on face, neck and body
Dissolvable?
Not by hyaluronidase; intralesional sodium thiosulfate has been reported for CaHA nodules as a management option
Where it fits
CaHA is the firmest of the three collagen biostimulators Dr Sin Yong uses and the one with the most immediate effect, which is why it is chosen where support rather than diffuse volume is wanted. The Radiesse page covers both forms. In acne scar work it is the filler support step of his 4D Scar Reconstruction, placed beneath a released scar so the floor can rise; the pairing is described on subcision with filler. For nose refinement he usually chooses CaHA or PCL rather than a hyaluronic acid-only product. As with the other non-HA materials, nothing here dissolves, so ultrasound mapping and a conservative plan come first; the wider class is defined under biostimulator.
Frequently Asked Questions
Both, depending on how it is used. Undiluted, the gel and microspheres fill on the day and collagen forms afterwards; diluted with saline or lidocaine, the volume effect is slight and it is used for skin quality.
Not by hyaluronidase, which acts only on hyaluronic acid. Intralesional sodium thiosulfate has been reported for CaHA nodules; it is a management option, not an equivalent of dissolving.
References
Kadouch JA. Calcium hydroxylapatite: a review on safety and complications. J Cosmet Dermatol. 2017;16(2):152-161. doi:10.1111/jocd.12326. source
Wollina U, Goldman A. Spontaneous and induced degradation of dermal fillers: a review. J Cutan Aesthet Surg. 2024;17(4):273-281. doi:10.4103/JCAS.JCAS_137_23. source
