Kidney essence is needed for healthy bones. Essence stored in the kidneys is transformed into bone marrow, which provides the nutrients for bone development and blood formation. When kidney essence is abundant, the bone cavities can be fully occupied with marrow and the bones become strong. Through this process the kidneys contribute to bone growth and reconstruction.
When depletion of kidney essence occurs, the bone cavity empties, as marrow is no longer able to fully occupy the space. This results in bone weakness or growth retardation. Clinical presentations include delayed closing of the fontanels (delayed fusing of the skull bones) in babies, difficulty walking, Osteoporosis, and fractures related to bone weakness or brittleness.
Teeth are considered to be remnants of bone in TCM and therefore are also dependent on kidney essence for their health. One particular TCM saying that illustrates this concept is: "Teeth are the manifestation of the kidneys, but their root is the bones." Teeth problems associated with a kidney deficiency include delayed growth of teeth in children or teeth falling out in early adulthood.