Biomechanics of the Keles Slider appliance for maxillary molar distalization--in-vitro analysis of force systems

The aim of this in-vitro study was to analyze the forces and moments acting in the first molar region induced by the Keles Slider appliance for maxillary molar distalization, thereby investigating this appliance's suitability for translatory distalization of the upper molars.

Over a working section of 3 mm with reactivation of the loaded spring systems, we analyzed the force systems of three laboratory-fabricated appliances of identical design using 3D measuring equipment.

The force systems registered in-vitro exhibited complex biomechanics. Regular reactivation of the loaded coils resulted in consistent distalizing forces and uprighting moments, in forces and moments toward buccal and weak extrusive forces, and increasing mesial-inward rotating moments.

The Keles Slider nearly achieves translatory molar distalization on a typodont in the sagittal plane. As a result, no uprighting activation is necessary for treatment. Because force application occurs palatally from the molars' center of resistance, there is a mesial-inward rotating moment that increases as distalization progresses, and this may lead to unwanted friction during clinical application. This is why regular reactivation of the coil spring systems, as well as subsequent measures for molar derotation, are indispensable. In the vertical plane, the molars are exposed to weak extrusive forces combined with moderate buccal rotating moments. These effects confirm that this appliance is indicated in patients with deep overbite.