Curvature versus v-bends in a group B titanium T-loop spring.
OBJECTIVE
To compare the system of forces acting on curvature and preactivated V-bends in titanium T-loop springs (TTLSs) made of 0.017- x 0.025-inch TMA (titanium molibdenium alloy) wire.


METHODS
Pictures of TTLSs preactivated by curvature and V-bends were inserted in the LOOP software program to design both TTLSs. Symmetry was assured using the program. Both TTLSs used the same amount (length) of wire and had the same angulation between their anterior and posterior extremities when passive. The loops were activated 7 mm, and forces and moments were registered after each 0.5 mm of deactivation. The brackets were at the same height, separated by 23 mm and angulated 0 degrees .


RESULTS
The preactivated curvature TTLS delivered horizontal forces ranging from 34 gF to 456 gF, while the TTLS preactivated by V-bends delivered forces ranging from 54 gF to 517 gF. The forces decreased more (30 gF vs 33 gF) with every 0.5 mm of activation on the preactivated V-bend TTLS than on the preactivated curvature TTLS. Vertical forces were low and clinically insignificant for both TTLSs. The moment to force (MF) ratios were systematically higher on the preactivated curvature than on the preactivated V-bend TTLS (from 5.8 mm to 38.8 mm vs 4.7 mm to 28.3 mm).


CONCLUSIONS
Although both loops show symmetrical moments in their anterior and posterior extremities and can be used for group B anchorage, the curvature preactivated TTLS delivers lower horizontal forces and higher MF ratios than the acute preactivated V-bend TTLS.
Martins
Renato Parsekian
RP
Faculdade de Odontologia de Araraquara, UNESP, Araraquara, São Paulo, Brazil. dr_renatopmartins@hotmail.com
Buschang
Peter H
PH
Viecilli
Rodrigo
R
dos Santos-Pinto
Ary
A
D000497:Alloys / Q000737:chemistry*; D001696:Biomechanical Phenomena; D003722:Dental Alloys / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D013314:Stress, Mechanical; D013499:Surface Properties
D000497:Alloys; D003722:Dental Alloys; C525450:titanium molybdenum alloy