The rhythms of human premolar eruption: a study using continuous observation.

New optical technology now allows for precise observation of erupting human premolars. Continuous overnight tracking of an erupting tooth with a video microscope system shows that eruption occurs almost exclusively during the early evening. During the day, slight intrusion is likely to occur. When Moiré magnification is used to provide extremely high resolution (0.05 micrometer), slight movements of the erupting tooth in concert with the arterial pulse can be observed, and a previously unknown cyclic movement with a period of 20 to 50 seconds is seen consistently. Rhythms in skeletal growth and tooth eruption suggest that treatment to influence jaw growth and move teeth may be most effective at specific times of the day.

High-resolution observations of human premolar eruption.

Using an optical instrument based on the principle of Moire magnification to obtain resolution of less than 0.1 mu m, eruption of maxillary second premolars was observed during the prefunctional phase of eruption in 10 children. The participants were observed on four occasions for approx. 30 min each, once in the afternoon and once in the evening on two consecutive days. For all participants, a pulsatile movement of the erupting tooth was noted in concert with the arterial pulse. Significant variations in short-term eruption rates and patterns were observed, 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 eruption occurred, but in several of the 30-min periods there was little movement or intrusion. An unexplained cyclic phenomenon was observed consistently, which had a period of 20-50 s and a range of magnitudes from 0.12 to 2.22 mu m. It seems clear that a discontinuous pattern of eruption occurs in short-term as well as longer-term observations.

The application of Moire magnification to high-resolution studies of human premolar eruption.

The optical phenomenon of Moire magnification can be used to provide real-time measurements of the position of an erupting human premolar, with a resolution of 0.1 micron or better. A new instrument for this purpose, which allows repeated measurements in the same individual, is described. Cyclic changes in the position of the erupting tooth in concert with the heartbeat, with a magnitude of 0.05-0.35 micron, can be discerned. An unusual cyclic rhythm, with a period of 20-50 s, was observed.

The effect of treatment on facial attractiveness.

Pretreatment and posttreatment frontal and profile slides of 13 orthodontic camouflage and 13 orthognathic surgery patients were shown to three panels of judges: an orthodontic, an oral surgery, and a "lay" panel of first-semester dental students. Each judge rated the facial attractiveness of the pretreatment and posttreatment views of each patient using a visual analog scale. A mean pretreatment and posttreatment score was then calculated for each treatment group for each judge. Paired t tests were used to compare the treatment groups and time periods. The orthodontic camouflage group was rated as significantly more attractive than the orthognathic surgery patients before treatment. There was no significant change in the facial attractiveness mean score for the orthodontic group, whereas the orthognathic surgery group was rated as showing a significant improvement. However, the orthognathic surgery group was still rated as being significantly less attractive after treatment than the orthodontics-only group.