Moment-to-force characteristics of preactivated nickel-titanium and titanium-molybdenum alloy symmetrical T-loops

Nickel titanium T-loop wire dimensions for en masse retraction

“…This was expected since it has already been shown that betatitanium T-loops produced with larger wire sizes produced more force. 18 The NiTi T-loops previously shown in the literature produced lower force levels [10][11][12] than was found in our study but were probably adequate for canine retraction. This study, however, aimed to evaluate springs for en masse retraction, where a force twice as large is generally suggested.…”

“…8 The 0.018" 3 0.025" T-loops, on the other hand, delivered forces ranging from 470 gf to 224 gf (Table 7), mostly adequate for en masse retraction and higher than what has been documented in the other T-loops made of the same size wire. These differences are probably due to the height of the T-loops of these reports (8.45 mm 10,12 ), which were larger than ours. A peculiar characteristic of shape memory alloys upon reverse transformation from stress-induced martensite is a drop of load before a pseudoelastic plateau is described on a load-deflection graph, 7,20,21 and this effect can be perceived on the forces measured of the T-loops (Table 7; Figure 5).…”

“…8,10,12 Then, they were attached to a 0.017" 3 0.025" stainless steel base wire through crimpable crisscross tubes (Morelli Ortodontia, Sorocaba, Brazil) ( Figure 1). The springs were distributed into three groups of 10 according to the thickness of the NiTi wire used: 0.016" 3 0.022", 0.017" 3 0.025", and 0.018" 3 0.025".…”

“…Even though the use of NiTi T-loops has already been shown in attempts to maintain the force upon deactivation, [9][10][11][12] it appears that they were designed for canine retraction. Because recent studies have shown that there is no difference in the rates of anterior retraction and loss of anchorage between that and en masse retraction, [13][14][15] it makes sense that the latter method would be clinically more practical and save chair time.…”

“…The issue is that previously described available NiTi T-loop9 designs produce low forces for that purpose (below 250 gf at the beginning of deactivation), either because they were made from a small dimension wire, such as 0.016" 3 0.022", 9 or because they were possibly not activated enough. [10][11][12] Another issue with the proposed NiTi T-loops is that they are too large, with heights above 8 mm, which could cause impingements clinically.…”