Temporary anchorage devices (TADs) have been successfully used in the maxilla. However, in the mandible, lower success rates present achallenge in everyday clinical practice. Anew TAD design will be presented that is intended to demonstrate optimization of the coupling structure as well as in the thread area for use in the mandible. Three TADs were examined: (A)Aarhus® system (68.99.33 A, Medicon, Tuttlingen, Germany), (B)BENEfit® orthodontic screw (ST-33-54209; PSM Medical, Gunningen, Germany) and(C) anew design with atwo-part screw thread. The TADs were inserted into artificial bone blocks after predrilling to test primary stability. To test the fracture stability, the TADs were embedded in Technovit® 4004 (Heraeus Kulzer, Wehrheim, Germany) and torsional loaded at an angle of 90° until fracture. The threshold torque values occurring were recorded digitally. The statistical evaluation was carried out using the Kruskal-Wallis test with aposthoc test according to Bonferroni (p < 0.05). The following values were measured for the insertion torque: A: 33.7 ± 3.3 Ncm; B: 57.1 ± 8.4 Ncm; C: 34.2 ± 1.4 Ncm. There were significant differences between A-B andB-C. The measured values for the fracture strength were as follows: A: 46.7 ± 3.5 Ncm; B: 64.2 ± 5.1 Ncm; C: 55.4 ± 5.1 Ncm. Significant differences were found between all groups. The adapted screw design has no negative influence on primary and fracture stability. Whether the design has apositive effect on the success rates in the mandible must be clarified in further clinical studies.
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