Overview
There is a common confusion between two very similar-sounding names: calcium hydroxyapatite and calcium hydroxylapatite. In chemistry and materials science, the correct and widely used term is calcium hydroxyapatite. The other spelling, calcium hydroxylapatite, is a misspelling that can cause confusion, but it refers to the same compound when people accidentally spell it that way.
What is calcium hydroxyapatite?
Calcium hydroxyapatite is a naturally occurring mineral and the main component of bone and tooth enamel. Its chemical formula is Ca10(PO4)6(OH)2, and it forms a crystalline structure that provides hardness and resilience in bone and teeth. It also has important roles in dentistry and orthopedics as an excellent biocompatible material.
Key features
- Chemical formula: Ca10(PO4)6(OH)2
- Primary component of bone mineral (bioapatite) and tooth enamel
- Biocompatible and osteoconductive, meaning it supports new bone growth
- Used in dental implants, bone grafts, and coatings for medical devices
Why the term calcium hydroxylapatite can cause confusion
The word "hydroxyl" and "hydroxylapatite" sound similar, and some people spell it as “hydroxylapatite.” However, the correct and accepted spelling in scientific literature is hydroxyapatite with an o after the h, not oh. Both refer to the same compound when used informally, but the formal name is calcium hydroxyapatite.
Bottom line
Calcium hydroxyapatite (Ca10(PO4)6(OH)2) is the correct name for the mineral that makes up bone and tooth enamel. "Calcium hydroxylapatite" is typically a misspelling of the same term. In academic writing and labs, use calcium hydroxyapatite for accuracy.