Abstract
ObjectivesCompression screws that can fix a fracture of the condylar head of the mandible are available. Although typical titanium lag screws are generally used, a series of headless screws have been designed for this purpose. The “headless” advantage derived from the complete submergence of the screw in the bone after fixation is the lack of irritation of the lateral ligament of the temporo-mandibular joint by the screw head. The aim of this study is to compare the compression force of typically used lag screws with that of newly developed headless compression screws.Materials and methodsThis study tested five types of screws with a 14-mm length: 10 2.0-mm lag screws and 40 headless screws (four groups of equal size: 1.5-mm H screws, 1.8-mm H screws, 2.0-mm H screws, and 1.8-mm W screws). Two cuboid blocks of standardized polyurethane foam were fixed by one screw. The maximal compression force (F in N) and torque at maximal compression force (T in Ncm) were tested according to the guidelines of the American Society for Testing and Materials (ASTM F1839-08).ResultsThe test results were as follows: 2.0-mm lag screw: F = 211.5 ± 20.7 and T = 21.1 ± 1.6; 1.5-mm H screw: F = 47.2 ± 5.6 and T = 18.2 ± 1.1; 1.8-mm H screw: F = 95.5 ± 9.8 and T = 18.2 ± 1.1; 2.0-mm H screw: F = 145.1 ± 18.4 and T = 25.5 ± 1.5; and 1.8-mm W screw: F = 180.5 ± 8.7 and T = 26.4 ± 2.8. Each type of screw significantly differed from one another as far as compression forces (F) were considered (p < 0.05): the best is the lag screw contrary to the thinnest H screw which is the worst one. For all tested screws, the compression force depended on the torque (S curve relationship was revealed, p < 0.05) and screw diameter (a larger diameter yielded greater compression, p < 0.05).ConclusionsThe 8-mm headless screws featured only a small loss of compression ability compared to the titanium lag screws.Clinical relevanceHeadless screws are mechanically attractive fixation materials for condylar head fracture treatment.
Highlights
Surgical management of mandibular head fractures has rapidly progressed in recent years, thanks to improvement in diagnostics [1], including accurate classification and imaging by cone beam tomography, as well as advances in surgical procedures and the development of new surgical materials
The lag screw has a high compressive capability, its screw head protrudes over the bone level after fixation (Fig. 1 a and b)
According to the Kruskal-Wallis test, the compression force was significantly different according to the screw type
Summary
Surgical management of mandibular head fractures has rapidly progressed in recent years, thanks to improvement in diagnostics [1], including accurate classification and imaging by cone beam tomography, as well as advances in surgical procedures and the development of new surgical materials. The lag screw has a high compressive capability, its screw head protrudes over the bone level after fixation (Fig. 1 a and b). This protrusion can cause problems and lead to bone resorption [4, 5]. To solve this problem, a headless compression screw was created [6]. A headless compression screw was created [6] This screw had a lower compression strength than the lag screw. A new modified headless compression screw was developed
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