PREPARATION OF HARD TISSUES – BONE AND TEETH – 2
DECALCIFICATION
To obtain thin sections of bone and teeth with a regular microtome, these tissues can be subjected to a decalcification, procedure, meaning the removal of calcium salts deposited in their extracellular tissue.
This can be done in several ways. One of the most common is to immerse teeth or bone fragments for appropriate periods of time in solutions that remove calcium salts. Acid solutions solubilize the calcium crystals and calcium leaves the tissues and enters the solutions. However, acid solutions can, over a long period of time, damage the structure of the tissues and provide distorted images, therefore weak (diluted) acid solutions must be used.
A better way is to place the tissues in solutions of substances, such as ethylenediaminetetraacetic acid (EDTA), which have a chelating action. Chelators have a high affinity for certain ions, including calcium and lead, and bind to them. Ions present in the tissues are gradually displaced to the chelating solution.
The action of chelating agents is more delicate than that of acids and provides images that are closer to that of the tissues in vivo.
After decalcification, the consistency of the tissues decreases and they can be subjected to routine histological preparation procedures, embedded in paraffin and sectioned with regular microtomes. The sections can then be stained with routine staining mixtures.
To obtain thin sections of bone and teeth with a regular microtome, these tissues can be subjected to a decalcification, procedure, meaning the removal of calcium salts deposited in their extracellular tissue.
This can be done in several ways. One of the most common is to immerse teeth or bone fragments for appropriate periods of time in solutions that remove calcium salts. Acid solutions solubilize the calcium crystals and calcium leaves the tissues and enters the solutions. However, acid solutions can, over a long period of time, damage the structure of the tissues and provide distorted images, therefore weak (diluted) acid solutions must be used.
A better way is to place the tissues in solutions of substances, such as ethylenediaminetetraacetic acid (EDTA), which have a chelating action. Chelators have a high affinity for certain ions, including calcium and lead, and bind to them. Ions present in the tissues are gradually displaced to the chelating solution.
The action of chelating agents is more delicate than that of acids and provides images that are closer to that of the tissues in vivo.
After decalcification, the consistency of the tissues decreases and they can be subjected to routine histological preparation procedures, embedded in paraffin and sectioned with regular microtomes. The sections can then be stained with routine staining mixtures.
The image is of a histological section of a decalcified bone fragment. As can be seen, decalcification allows the histological structure of the tissue to be very well preserved. Details of the cells and the organic extracellular matrix can be clearly observed.
Decalcified bone. Hematoxylin and eosin staining.
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