A Mechanical Stress Model Applied to the Rat Periodontium: Using controlled magnitude and direction of orthodontic force with an absolute anchorage

Abstract

The objective of this study was to develop a mechanical stress model applied to the rat periodontium by means of moving teeth with magnitude- and direction- controlled orthodontic forces for a long period. Three length-differed titanium screw implants (3.0, 3.5 and 4.0mm in length) were used as anchorage for tooth movement. The upper first molars were moved mesially up to 28 days using three newly-developed force-differed super-elastic titanium-nickel (Ti-Ni) alloy closed coil springs (2, 10 and 35gf in load). The survival rate and the pull-out test data for each screw implant revealed that a 4.0mm-long screw implant was the most stable. By tooth displacement evaluation and histological observation, a 2gf-loaded spring provided the minimally detrimental effects on the periodontium and efficiently continuous tooth movement. We developed an effective mechanical stress model applied to the rat periodontium by applying magnitude- and direction-controlled light forces for long durations.