Bone decalcification

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Bone decalcification is the removal of calcium ions from the bone through histological process thereby making the bone flexible and easy for pathological investigation.

This is necessary in order to obtain soft sections of the bone using the microtome. Every thin section cut can be processed like any other soft tissue of the body. Calcium ions found in the bones are responsible for its rigid posture, people suffering from diseases like osteomalacia and rickets have an unusually low amounts of calcium ions in their bones thereby rendering their bones flexible and most times unable to carry their body weight. There are two categories of decalcifying agents namely, chelating agents and acids. The acids are further divided into weak (picric, acetic and formic acid) and strong acids (nitric and hydrochloric acid). The acids make up a solution of calcium ions while the chelating agents take up the calcium ions. Most frequently used chelating agent is Ethylenediaminetetraacetic acid (EDTA). Acids have some effects on the stainability of the tissue.

Decalcification is a lengthy procedure, as bone pieces have to be left in the decalcifying agent for several days or even weeks, depending on the size of the bone. Traditional methods of handling hard tissues, i.e. bone and teeth, usually present a problem to both the pathologist and histotechnologist. Many of the grossing and cutting-in techniques in current usage for these tissues dictate the use of gross sectioning procedures with a high-speed saw and/or long periods in a decalcifying solution, prior to reducing the specimen to a size that can be easily processed, embedded and sectioned. Frequently the poor quality thin sections obtained when these methods are employed contribute to the already difficult task of evaluating the pathology and making a correct diagnosis. With the introduction of Low Speed Saws, it is now possible to routinely and rapidly reduce undecalcified surgical specimens of hard tissue, to a thickness of 2–3 mm, without compromising the integrity of the tissue.

There are numerous tests which can be done to ensure that decalcification is complete. These tests are physical which involves simply bending the specimen, x-ray examination and chemical means.

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