Rigidity of major connectors when subjected to bending and torsion forces.

Rigidity tests were performed on maxillary major connectors of different designs and mandibular major connectors of the lingual bar-type with different cross-sectional shapes and thicknesses. Each major connector was clamped on one side while the other side was subjected to bending, torsion, and bending under torsion forces. Deformation was measured with a micrometer microscope. The most rigid maxillary major connector was the design incorporating the anterior-posterior palatal bar. The most flexible was the U-shaped palatal bar. The full pear-shaped lingual bar (4 x 4 mm) was the most rigid of the major connectors. Among the more conventional lingual bars, the semielliptical bar (3.75 X 1.75 mm) was the most rigid, and the narrow semielliptical bar (4 x 1.5 mm) was the most flexible.