The frictional force has been considered as an harmful factor in an active unit where tooth movement occurs, but as an advantageous factor in anchor unit that resist tooth movement. That is, efficient tooth movement is planned by using ligation methods that have low levels of bracket-wire frictional force and the anchorage control can be achieved by using ligation methods that have high levels of bracket-wire frictional force that result in binding of the bracket accompanied by little or no tooth movement.
The purpose of this study was to evaluate the frictional force generated between bracket and wire in accordance with the methods of ligation, the material of ligation and the passage of time under artificial saliva. Tested were 0.017X0.022 inch stainless steel wires in standard edgewise twin brackets for upper central incisors in a 0.018-inch slot The wires were ligated into the brackets with elastomeric modules and stainless steel ligatures. Whole tie, half tie, twisting tie and double overlay tie were done with elastomeric modules. With 0.009-inch stainless steel ligature whole tie and half tie were done by needle holder and whole tie by ligature tying plier. With 0.012-inch stainless steel ligature whole ties were done by needle holder. Whole tie groups of elastomeric module were kept in artificial saliva bath at 37t for 28 days. The frictional force was recorded by means of an Instron universial testing instrument (4202 INSTRON, Instron Co., U.S.A.) at initial, 7, 14, 21, and 28 days.
The results for ligated samples in a simulated oral environment revealed the following
In elastomeric module whole tie, 28 days group was significantly greater mean static frictional force than any other group but there were no significant differences among any other group (p>0.05). Elastomeric module twisting ties were significantly greater mean static frictional forces than any other ligation method but there were no significant differences between twisting tie and double overlay tie (p>0.05). Twisting tie, double overlay tie, whole tie, half tie showed differences in decreasing order.
Stainless steel half tie produced lower mean static frictional forcee than whole tie, ligation by ligature tying plier
produced greater mean static frictional force than by needle holder and ligation with 0.012-inch stainless steel ligature produced greater mean static frictional force than with 0.009-inch stainless steel ligature (p<0.05).
? There were no significant differences between the mean static frictional forces of elastomeric whole tie and stainless steel whole tie (p>0.05).
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