Orthodontic movement is defined by the effect of the force system on the tooth and the consequent responses of the adjacent structures.
For that reason, effective space closure is challenging, and can be optimized when there is control and predictability of the force system.
The released forces must be continuous and the center of rotation of the tooth must be constant to release biologically favorable forces that does not continually modify the stress areas of the periodontal ligament.
The simplest way to determine and visualize the force system is utilizing two groups of teeth, to obtain one center of resistance and one center of rotation in each unit.
This is possible using the segmented arch approach. Moreover, the greater interbrackets distance and smaller load/deflection rates of the loops are favorable to the dental movement biology.
Pre-calibrated loops, as the T-loop, are an important part of this technical approach.
â–º DENTAL BOOK: Orthodontics - Diagnosis and Management of Malocclusion and Dentofacial Deformities - Om Prakash Kharbanda
Different T-loops designs have been studied in the literature regarding their parametric characteristics.
However, there is still no consensus on which height, apical length, preactivation, material and cross-section are more adequate.
In their studies, several authors did not evaluate some characteristics that directly influence the appliance force system, such as the neutral position and the possibility of permanent deformation.
In addition, an important attribute of the T-loop is the possibility of obtaining, with different preactivations or with the eccentric positioning of the spring, differential moments or differential forces, to achieve a differential space closure, that is, a space closure greater in one unit compared to the other.
Thus, the aim of this study was to review the literature on the force systems obtained in different studies related to the segmented T-loop, specially regarding the main factors that influence it.
