Abstract
Centrifuge has become a commonly used device in medical and dental clinics, especially for preparing platelet-rich plasma and platelet-rich fibrin. The preparation protocol depends on the centrifugal force generated by the centrifugation process, which is directly affected by the rotational speed of the centrifuge. Therefore, any less accuracy in the real rotational speed results in a change in the centrifugal force that can affect the properties of the resulting material. For this reason, this study aims to ascertain whether the selected rotational speed of the centrifuge can be relied upon as an actual speed and can be used in the calculation of the centrifugal force. Fifteen new centrifuges from different origins were randomly selected. Each centrifuge was set at a specified speed. Then, two tubes were placed inside each one. A thin, flexible piece of plastic was placed touching the cap of the tubes during their rotation to make a sound. Following that, the sound was recorded with a special recording device. Subsequently, the fifteen recorded audio files were analyzed using a software application. Finally, the number of waves per minute was counted, and the rotational speed was calculated. It was found that ten of fifteen devices showed significant differences between the selected speed and the actual speed. Moreover, the percentage difference for these ten centrifuges ranged from 15-43%. In conclusion, it is recommended to pre-assess and calibrate the centrifugal speed in the beginning, to obtain the required centrifugal force.

Key words: Actual rotational speed, centrifugal force, wave analyses, Calibration, Centrifuges.