ABSTRACT
Dr. Youn-Sic Chun and coworkers invented the new machine for getting information about the relative effectiveness of the orthodontic appliances and we named it Calorific machine. The author and colleagues used this machine to compare with tooth moving mechanism by 3 types of the insertion method of precision-TPA for derotating the posterior teeth. We measured the distance of tooth movement and found out the rotational center on the occlusal X-ray film and the tooth movement on the occlusogram and then processed paired t-test by SAS program. The results were as follow : 1. In the intermolar width, the mesial insertion method showed the loss of distance, and the other methods(-distal insertion method, mesial expansion method-) showed the increase of distance. 2. In the arch length, the distal insertion method was exhibited as most recommandable way for increasing the arch length. 3. The rotation center of the mesial insertion method for derotating the molar, was located between mesial pit and central pit of the lower 2nd molar. and, in the distal insertion method, it was located between distal pit and distolingual cusp, and in the mesial expansion method was located at distal pit.