Analysis of a device for assessment of abutment and prosthesis screw loosening in oral implants.

Screw loosening is an irritating problem in implant dentistry. Loosened abutment screws and prosthesis screws are often found at yearly examinations. Loosened screws may cause costly complications, such as screw fractures and fracture of the framework, and methods to prevent them would be welcome. The purpose of this study is firstly to describe a mechanical protractor device designed to fit the electrical Torque Controller (Nobel Biocare, DEA 020, Gothenburg, Sweden) and measure the number of degrees necessary to retighten the abutment screw or the prosthesis screw to reach the target torque value. A second purpose is to analyse the precision and validity of the device. The results of the study indicate that the degree of preset loosening of abutment and prosthesis screws can be well reflected in the number of degrees necessary for retightening. It was also shown that it is possible to retighten the abutment and prosthesis screws with a precision of 1.7 degrees and 1.3 degrees, respectively. The study shows that the device has good precision and validity. By using this device, we hope to be able to evaluate various parameters for screw stability, such as the type of implant system, the number of fixtures, the type of abutments, the type of bridge material and the need for retightening of the abutment and prosthesis screws.