HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Full Text (PDF) Appendix Services Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Lapatki, B.G. Articles by Paul, O. Search for Related Content PubMed PubMed Citation Articles by Lapatki, B.G. Articles by Paul, O.

Smart Bracket for Multi-dimensional Force and Moment Measurement

¹ Department of Orthodontics, School of Dental Medicine, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg i.Br., Germany; and
² Department of Microsystems Engineering (IMTEK), University of Freiburg, Germany

View larger version (79K): [in this window] [in a new window]   Figure 1. Numerically simulated stress distributions within an orthodontic bracket resulting from 3D force and moment application. (A) Finite-element model of an orthodontic bracket with inserted wire and underlying (cubic) tooth crown. The model was constructed with 87,253 elements (ANSYS element Solid 92) leading to a total number of 126,673 nodes. These tetrahedral structural elements having 10 degrees of freedom are highly suitable for structural mechanical simulations. The model was selectively loaded at the cube’s center with the 6 force and moment components by exertion of adequate couples of forces with equal or opposite directions on opposing cube surfaces, while keeping both wire ends fixed. Black arrows: spatial orientation of the x, y, and z axes. (B) Illustration of the 2 stress components (shear stress xy and normal stress difference xx-yy) extractable from piezoresistive microsensors positioned in the xy-plane. Grey: Unloaded form. Black: Forces and resulting deformations. (C) Shear and normal stress fingerprints in the xy-plane, resulting from selective application of each of the 6 force or moment components. Red: Positive stress. Blue: Negative stress.

View larger version (76K): [in this window] [in a new window]   Figure 2. Microsystem chip before and after encapsulation into a smart bracket. (A) (left) Micrograph of the sensor chip (used for construction of the smart bracket) with 32 stress sensors distributed over the chip area, analogue signal conditioning, and digital control unit. Center: sensor element with switches. Right: octagonal sensor with 8 contacts allowing for application of the spinning-current method. (B) Schematic illustration (cross-section) of the smart bracket model. The sensor chip was wire-bonded to a printed circuit board and encapsulated in a plastic bracket. (C) Photograph of the manufactured smart bracket with a base of 8 x 8 mm2 (scale of approximately 2.5:1 compared with normal bracket size). For the mechanical experiments, the archwire was adhesively attached.

View larger version (12K): [in this window] [in a new window]   Figure 3. Comparison of applied force components Fx, Fy, and Fz and corresponding values inferred from the stress sensor signals for the second sequence of 396 load cases. (A) Component Fx. (B) Component Fy. (C) Component Fz. Applied force values (blue line) were registered by the calibration system. Smart bracket values (red triangles) were inferred from the 24 most relevant sensor signals.

View larger version (15K): [in this window] [in a new window]   Figure 4. Comparison between applied moment components Mx, My, and Mz and corresponding values inferred from the stress sensor signals for the second sequence of 396 load cases. (A) Component Mx. (B) Component My. (C) Component Mz. Applied moment values (blue line) were registered by the calibration system. Smart bracket values (red triangles) were inferred from the 24 most relevant sensor signals.