In vitro testing of a measuring system for in vivo recording of orthodontically applied forces and moments in the multiband technique. Part II.

The aim of this study was to measure in vivo the forces and moments acting therapeutically on the individual tooth in connection with the multiband technique. Securing and evaluating the planned in vivo measurements involves analysing the measuring accuracy of the system as a whole by means of corresponding in vitro investigations. Errors in determining the therapeutically effective force system may result from the electrical measurement of the mechanical quantities by the sensor system and from the fixing of the archwire in therapeutic position. The precision of this fixing is influenced by displacements induced by elasticities and mechanical tensions in the measuring system. Calibration test series have shown the sensor system to have a margin of error of less than 2%. The displacements influencing precision fixing of the archwire were determined by means of a laser position measuring system. For a maximum orthodontic force of 1.5 N, they are 0.06 mm in the least favourable case. The resulting measuring accuracy was determined analytically or graphically, depending on the key parameters. Successful in vivo studies of the therapeutically applied force systems are to be expected on the basis of these results.