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Atraumatic, well-directed, and efficient tooth movement is interrelated with the therapeutic application of adequately dimensioned forces and moments in all three dimensions. The lack of appropriate monitoring tools inspired the development of an orthodontic bracket with an integrated microelectronic chip equipped with multiple piezoresistive stress sensors. Such a 'smart bracket' was constructed (scale of 2.5:1) and calibrated. To evaluate how accurately the integrated sensor system allowed for the quantitative determination of three-dimensional force-moment systems externally applied to the bracket, we exerted 396 different force-moment combinations with dimensions within usual therapeutic ranges (+/- 1.5 N and +/- 15 Nmm). Comparison between the externally applied force-moment components and those reconstructed on the basis of the stress sensor signals revealed very good agreement, with standard deviations in the differences of 0.037 N and 0.985 Nmm, respectively. We conclude that our methodological approach is generally suitable for monitoring the relatively low forces and moments exerted on individual teeth with fixed orthodontic appliances.

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This paper reports on a novel silicon-on-insulator (SOI) based low-temperature fabrication process to realize microelectromechanical high-frequency resonators. Key features of the devices are single-crystal silicon resonant beams, 400-nm or 600-nm thin transducer gaps, and gold electrodes. The fabrication process combines bulk silicon micromachining applying deep reactive ion etching, low-temperature deposition of a thin sacrificial oxide layer, and electroplating of the lateral electrodes. The resonant behavior of devices with resonance frequencies res between 420 kHz and 4.11 MHz was characterized as a function of the bias voltage bias applied to the beam. Measurements were performed at ambient pressures between 5 10 3 Pa and 0.5 Pa.values up to 52 000 at res = 420 kHz and 6 000 at res = 4 11 MHz were obtained. The interaction of resonator and measurement setup were simulated using an electrical network simulation program combined with a finite element analysis using ANSYS.Index Terms-High-frequency resonator, low-temperature processing, microresonator, sacrificial oxide, silicon-on-insulator (SOI).