HIGH-RESOLUTION OBSERVATIONS OF HUMAN PREMOLAR ERUPTION

Using an optical instrument based on the principle of Moire magnificat ion to obtain resolution of less than 0.1 mu m, eruption of maxillary second premolars was observed during the prefunctional phase of erupti on in 10 children. The participants were observed on four occasions fo r approx. 30 min each, once in the afternoon and once in the evening o n two consecutive days. For all participants, a pulsatile movement of the erupting tooth was noted in concert with the arterial pulse. Signi ficant variations in short-term eruption rates and patterns were obser ved, with a mean rate of 0.28 mu m/min over continuous 20-min periods but a range from -0.91 to 2.29 mu m/min. During most sessions net erup tion occurred, but in several of the 30-min periods there was little m ovement or intrusion. An unexplained cyclic phenomenon was observed co nsistently, which had a period of 20-50 s and a range of magnitudes fr om 0.12 to 2.22 mu m. It seems clear that a discontinuous pattern of e ruption occurs in short-term as well as longer-term observations.