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Biomechanical analysis of asymmetric mesio-distal molar positions loaded by a symmetric cervical headgear

Kizilova N., Geramy A., Romashov Y.

Acta of Bioengineering and Biomechanics

2016

Vol. 18, no. 4

97--106

Purpose: The plane 2d model and 3d finite element model of the headgear attached to two molars with different mesio-distal location are studied to show the asymmetric mechanical effects produced by symmetrically loaded headgear. In daily dental practice the asymmetrical location of molars is usually ignored. Methods: Six 3D finite element models of a symmetric cervical headgear were designed in SolidWorks 2011. The models showed symmetric molar position (model 1), 0.5 to 2 mm of anterior-posterior molar difference (models 2-5) and a significant asymmetry with 10 mm of difference in the locations (model 6). The head gear was loaded with 3N of force applied at the cervical headgear. The forces and moments produced on terminal molars are assessed. Results: It is shown the difference between the forces acting at the longer and shorter outer arms of the headgear increases with increase in the distance. The significant numeric difference in the forces has been found: from 0.0082 N (model 1) to 0.0324 N (model 5) and 0.146 N (model 6). These small forces may produce unplanned distal tipping and rotation of the molars around their vertical axes. The most important funding was found as a clockwise yaw moment in the system when is viewed superio-inferiorly. The yaw moment has been computed between -0.646 N•mm (model 1) and -1.945 N•mm (model 5). Conclusions: Therefore even small asymmetry in location of molars loaded by a symmetric cervical headgear will produce undesirable move-ment and rotation of the teeth that must be taken into account before applying the treatment.

Zgrzewanie rezystancyjne punktowe z pneumatycznym i serwomechanicznym dociskiem elektrod

Mikno Z., Kowieski S.

Przegląd Spawalnictwa

2015

R. 87, nr 10

53--59

W artykule porównano dwa systemy docisku elektrod zgrzewarki w procesie zgrzewania rezystancyjnego tj. klasyczny pneumatyczny i serwomechaniczny. Porównania dokonano na podstawie pomiarów wielkości charakterystycznych procesu tj.: prądu i napięcia zgrzewania oraz przebiegu siły docisku i przemieszczenia elektrod. Wyznaczano wielkości pochodne prądu i napięcia zgrzewania i analizowano: przebieg mocy chwilowej, rezystancji zastępczej statycznej oraz energii dostarczonej do zgrzeiny. Pomiary przeprowadzono na zgrzewarce inwertorowej dla technologicznych prób zgrzewania punktowego dwustronnego dla blach gatunku DX53 o grubości 1.5 mm z ochronną warstwą cynku. Uzyskane wyniki zweryfikowano eksperymentalnie za pomocą badań niszczących tj. statycznej próby rozciągania oraz badań metalograficznych.

The article presents the comparison of two electrode force systems applied in resistance welding machines, i.e. pneumatic (i.e. classical) and servomechanical. The comparison was based on measurements of characteristic quantities of the process, i.e. welding current and voltage as well as the force and travel of electrodes. The study involved the determination of derived quantities of welding current and voltage as well as the analyses of momentary power, static slope resistance and energy supplied to the weld. Measurements, involving the use of an inverter welding machine, were performed for technological tests of two-sided spot welding of 1.5 mm thick DX53 steel sheets provided with protective zinc coatings. The results were verified experimentally in destructive tests, i.e. static tensile tests and metallographic examinations.