Load-deflection behavior of transpalatal bars supported on orthodontic palatal implants. An in vitro study

Within the scope of indirect orthodontic implant anchorage, the transpalatal bar (TPB) transmits the forces applied at the anchorage teeth to an implant inserted into the palate. It is thus the connecting element between teeth and palatal implant. The aim of the present study was to analyze the extent of sagittal deflection of TPBs of different dimensions attached to an implant abutment. For this purpose, commercially available stainless steel wires measuring 1.2 mm x 1.2 mm (n = 25) and 0.8 mm x 0.8 mm (n = 25) respectively were bent to comply with a representative bend specified with respect to casts, fixed with clamp caps to the implant abutment, and exposed for forces of 50, 100, 150, 200 and 300 cN. The mean deflection of the 1.2 mm x 1.2 mm TPB was lower by a factor of 4.5 than that of the 0.8 mm x 0.8 mm TPB. With a clinically relevant load of 200 cN, for example, the mean deflection of the 1.2 mm x 1.2 mm (0.051" x 0.051") TPB was 301 microm, whereas that of the 0.8 mm x 0.8 mm (0.032" x 0.032") TPB was 1337 microm. When maximum anchorage is required, 1.2 mm x 1.2 mm (0.051" x 0.051") TPBs should be used as a matter of principle.