Rocking and twisting moments in extraction of teeth in the upper jaw.

The purpose of this study was to investigate with the strain gauge method the rocking moments needed during the extraction of upper jaw teeth. In addition to the buccal and palatinal rocking moments, the twisting moment was also measured. The highest mean value of both the average and highest buccal and palatinal movements was measured during the extraction of canines. The mean value of the average buccal moments for the first and second molars was significantly higher than for premolars, but the mean value of the average palatinal moments was significantly lower for the first and second molars than for incisors and almost significantly lower than for premolars. The longest extraction times were used during the extraction of molars and canines. There was no difference in the magnitude of the moments for the upper and lower jaw canines. The extraction of the upper jaw incisors required significantly more rocking moment than the extraction of the lower jaw incisors. There was no difference between the upper and lower jaws in the mean values of the total rocking moments for premolars. The mean values of the total and highest rocking moments for molars in the lower jaw were significantly higher than the corresponding values in the upper jaw. The difference was due to the different bone structures of the upper and lower jaw and to different roots of molars in the upper and lower jaw. The extraction times for the canines and molars were significantly higher in the upper jaw than in the lower jaw.