Technology developments to initiate a next generation of cochlear implants.

In the framework of the EU-supported research project Healthy Aims, we developed a range of novel electrode arrays and related technologies for use in hearing prosthesis. This paper summarizes our ongoing research activities on alternative electrode manufacturing routes, functional electrode interfaces and smart intra-cochlear and intra-modiolus electrode arrays.

Location of the centers of resistance for anterior teeth during retraction using the laser reflection technique.

The location of the centers of resistance for various symmetric units of the anterior maxillary dentition for a lingually directed force was studied in two dry human skulls. The units investigated were composed of two incisors, four incisors, and six anterior teeth. In addition, the effect of change in force magnitude on the location of the centers of resistance of these units was investigated. The laser reflection technique was used to study both the direction and magnitude of the initial displacement of the consolidated teeth under loading. The results indicated that the center of resistance shifted apically with the incorporation of a greater number of teeth into an anterior segment. With a unit of six anterior teeth, the apical shift of the center of resistance was the greatest. Increasing force levels had little effect on the location of the center of resistance of a given unit. This phenomenon was observed in both the skulls tested, suggesting that general trends may exist in the displacement characteristics of the dentition when subject to controlled force systems.

The center of resistance of anterior teeth during intrusion using the laser reflection technique and holographic interferometry.

The aim of this investigation was to define the location of the center of resistance of various consolidated units of the maxillary anterior dentition using a dry human skull when subject to intrusive forces. The laser reflection technique and the holographic interferometric technique were employed to measure the displacement of the dentition to the applied forces. The units studied consisted of two central incisors, four incisors, and six anterior teeth. The incorporation of the lateral incisors into the upper incisor segment resulted in a small distal shift of the center of resistance (+/- 2 mm). However, when the canines were included into this unit, the center of resistance shifted distally by a significantly larger amount (+/- 7 mm). Increasing the magnitude of intrusive forces applied to the various units appeared to have no effect on the location of the center of resistance.

Evaluation of intrusive mechanics of the type "segmented arch" on a macerated human skull using the laser reflection technique and holographic interferometry.

Twelve different systems of intrusion, based on the principle of the "segmented arch," were evaluated on a macerated human skull. The number of teeth involved in the anterior unit and the location of the application points of intrusive force were considered to be variables. Initial displacements of the anterior teeth after loading were registered by means of the laser reflection technique and double exposure holographic recordings. An attempt was made to define "this" intrusive system, achieving the most genuine intrusion (for definition, see text) without flaring of the teeth. When two central incisors were incorporated in the sectional wire, strong torque forces appeared, especially when the intrusive forces seized more distally. When four or six anterior teeth were pinned in the sectional wire, tooth movement seemed to be under better control. When the six front teeth were incorporated in the sectional wire, the center of resistance (for definition, see text) was located more to the distal side of the canines. It seemed more difficult, however, to define the center of resistance of the four incisors; it was situated approximately distal to the lateral incisors. In some of the intrusive systems, the teeth underwent independent mesial or distal rotations. This was easily observed with the laser measuring techniques used.