HEAT IMPACT OF REVOLVING INSTRUMENTS ON VITAL DENTIN TUBULES

¹ New York City, N. Y.

Heat trauma from revolving instruments may be divided into parts—1. The generation of such frictional heat, of a sufficiently large caloric value, that although distributed over a large area, the sequellae may include pain, dessication of dentin tubules, hyperemia, and possible pulp death. 2. The generation of frictional heat over a relatively small area, of a caloric value sufficient to cause pain by the intensity of thermal impact per dentin tubule, but insufficient to endanger the pulp. The temperature of these small frictional areas exceeds the high tolerance zone limit of 130°F. and ranges from an estimated rise of 67.5°F. to 270°F., depending upon individual operating speed and pressure (1-4 lbs.). These figures are not intended to be accepted literally, but are estimates of potential thermal impact. Because of many variables, and experimental limitations, some of which have been mentioned, it is probable that more accurate figures would be considerably higher.

Since the second type of heat trauma occurs even with the gentlest use of the smallest burs, all cavity preparation by revolving instruments should be performed under a stream of warm water. Rubber dam is contra-indicated except for final observation and minor finishing touches. With "Thermal Control" pain is prevented and the need for anesthesia is appreciably decreased, while operative speed is enhanced and pulp safety from thermal trauma is complete. It should be considered malpractice to anesthetize away pain which need never have been caused.

The specific heat of dentin and of cortical bone may be considered to be 0.3. The work on "Thermal Control" applies not only to the cavity preparation of dentin, but to the use of revolving instruments in bone surgery.