Long-wave cycles in the position of erupting human premolars

Unusual long-wave cycles in the position of an erupting human premolar were first noted by Trentini et al. [Trentini CJ, Brown WH, Paterson RL, Proffit WR. The application of Moiré magnification to high precision studies of human premolar eruption. Arch Oral Biol 1995;40:623–9]. This report characterises them in detail and evaluates their significance relative to human tooth eruption. The magnitude and frequency of Trentini cycles were examined in high-resolution recordings of premolar eruption in patients without and with periapical infiltration of a vasoconstrictor or vasodilator, and the possibility of artifact due to the natural frequency of vibration of a tooth–PDL system or to building vibration was evaluated. The cycles are characterised by a magnitude of 1.3 ± 0.5 μm and a frequency of 1.8 ± 0.5 cycles per minute, with greater variation between than among subjects. They cannot be explained as a natural frequency phenomenon, and vibration from microseism is highly unlikely. The cycles disappear when blood flow to the periapical area of the tooth is interrupted and reappear when blood flow resumes. The cycles appear to reflect a physiologic rhythm, probably related to blood flow in the periodontal ligament. Because they are similar whether or not a tooth is erupting at a particular time, however, it appears that they are not a direct reflection of a blood flow-related eruption mechanism.