Comparing the Efficacy of Specs Loop and T Loop for En Masse Anterior Retraction - A Finite Element Study

Figures & data

Figure 1. The Specs loop.

Figure 2. The T loop.

Figure 3. Specs loop and T loop with preactivation bends.

Table 1. Material properties.

Properties	Wire & Loop	Maxillary bone	Teeth	Periodontal ligament	Bracket
Young’s Modulus (MPa)	69,000	2000	20,000	5	200,000
Poisson’s Ratio	0.3	0.3	0.3	0.3	0.3

Figure 4. Finite element analysis model of maxillary bone and dentition along with Specs loop.

Figure 5. Stress acting on the teeth.

Figure 6. Stress acting on the bone with teeth assembly.

Table 2. Force, moment and moment to force ration acting on anterior and posterior teeth.

Groups	Anterior teeth					Posterior teeth
	Horizontal Force (g)	Horizontal Moment (g/mm)	Vertical Force (g)	Vertical Moment (g/mm)	M/F Ratio (mm)	Horizontal Force (g)	Horizontal Moment (g/mm)	Vertical Force (g)	Vertical Moment (g/mm)	M/F Ratio (mm)
Specs Loop	158.60	1205	56.36	1083	10.64	632.80	2178	67.510	4170	9.06
T loop	178.50	1228	69.65	1088	9.33	644.90	2174	68.89	4147	8.86

Table 3. Crown tip, root tip and vertical movements of individual teeth.

Groups	Movements (e^−3mm)	Central incisor	Lateral incisor	Canine	Second premolar	First molar	Second molar
Specs Loop	Crown tip	13.210	13.990	13.250	18.420	18.750	17.580
	Root tip	−4.150	−6.380	−8.920	−5.500	−4.290	−3.510
	Vertical movement	−36.910	−35.710	−31.820	−27.040	−20.100	−10.730
T Loop	Crown tip	12.330	13.130	12.610	17.460	17.810	16.730
	Root tip	−3.540	−5.610	−8.000	−4.890	−3.770	−3.130
	Vertical movement	−37.120	−35.820	−32.540	−26.140	−19.760	−10.120