T-loop Springs Research Articles

Evaluation of anchorage loss after en masse retraction in orthodontic patients with maxillary protrusion using friction vs frictionless mechanics: randomized clinical trial.

To evaluate anchorage loss after en masse retraction in bimaxillary dentoalveolar protrusion patients using friction vs frictionless mechanics. Thirty patients with bimaxillary dentoalveolar protrusion needing extraction of upper first premolars and en masse retraction with maximum anchorage were included in this two-arm, parallel, single-center, single-blinded randomized clinical trial with a 1:1 allocation ratio using fully sealed opaque envelopes. Friction group retraction utilized elastomeric power chain between miniscrews and hooks crimped mesial to upper canines on 17 × 25 stainless steel archwire. Frictionless group used customized T-loop springs loading upper first molars indirectly anchored to miniscrews. Activation was every 4 weeks until full retraction. The primary outcome assessed was anchorage loss evaluated at cusp tip and root apex of the first molar. First molar rotation, incisor tip and torque, and root resorption of anterior teeth were evaluated on digital models and cone beam computed tomography taken before and after space closure. Anchorage loss at crown of first molar was significantly more in frictionless group by 2.1 mm (95% CI = -0.4 to 3.5), (P = .014), while there was no significant difference in anchorage loss at root apex between groups. Significant mesial in molar rotation of 6.672° (95% CI = 12.2-21.2), (P = 0.02) was greater in the frictionless group. Both groups showed comparable tip, torque, and root resorption values. No severe harms were reported. There was mild gingival overgrowth and inflammation in the frictionless group due to T-loop irritation. Extra anchorage considerations are needed during en masse retraction when frictionless mechanics is implemented as higher anchorage loss and molar rotation were detected. No difference in tip, torque, and root resorption was observed.

What Is the Most Effective Frictionless Method for Retracting Anterior Teeth When Using Buccal Fixed-Appliance Therapy? A Systematic Review.

There are various techniques and designs for springs used in orthodontic treatment, including frictionless methods for closing spaces. However, there is limited explicit evidence to support the superiority of one method over another. This review aims to investigate the available evidence and highlight the advantages of these different methods. This review contained six papers, and information such as study design, spring design, applied force systems, variables studied, follow-up period, and records were extracted. All of the studies focused on canine retraction with the Ladanyi spring showing the highest rate of movement (1.8 mm per month) among all springs for upper canine retraction. The Gjessing and T-loop springs outperformed the Reverse Closing Loop and Ricketts spring, respectively, substantially. In terms of tip control, the T-loop spring showed a clear advantage over the modified Marcotte spring with a difference of 1.2° vs. 6.6° per 3 months. Additionally, it was observed that the Reverse Closing Loop caused a significant loss of anchorage during canine retraction with a medial movement of 2.4 mm. When comparing wire types, no significant differences were found between TMA and Nitinol, while stainless steel was found to be less effective in terms of movement rate and tip control. However, the results indicated that there was no clear evidence that one specific technique was definitively preferable to another; therefore, there is an urgent need for more studies with proper study designs to produce more robust conclusions.

The effect of different α and β gable on stainless steel and TMA segmental T-loop on the resulting force – an in vitro study

Adding more angle to the segmental T-Loop gable can affect the amount of force created to retract the canine on an orthodontic treatment with extraction. In-vitro laboratory experimental design, performed at the Chemistry Laboratory of Faculty of Science, ITB. The samples are 60 segmental T-loop springs with α and β angle of 0°–0°; 0°–45°; 45°–0°; 22.5°–22.5°; 15°–30°; 30°–15°. Force was measured using autograph with retraction distance of 1, 2, and 3 mm, then analyzed using ANOVA statistics analysis with a factorial design of 2x3x6 and 5 replications for each cell. The results of the posthoc Student Newman Keuls and Tukey test show that the added angle to the α and β gables of SS and TMA T-loop will add more resulting force along with the increase of retraction distance. The added angle to the α and β gables of SS and TMA segmental T-loop will add more resulting force along with the increase of retraction distance. The force resulted by the SS T-loop with various α and β gables are significantly different, while the force resulted by the TMA T-loop are not (p-value <0.05), as long as α + β is the same. The force resulted by the SS T-loop with various α and β gables are significantly different. However, on the TMA segmental T-loop, as long as α + β is the same, the force resulted will not be different.

Effect of stress relaxation in two different preactivation methods of beta-titanium T-loops: bends vs. continuous curvature

ObjectiveAssess the changes in the force system of T-loop springs (TLSs) preactivated by bends and curvature, when secured in place with a constant strain over time. Materials and MethodsA total of 120 TLSs with dimensions 6 x 10 mm, produced out of 0.017 × 0.025-inch TMA, were randomly divided into two groups of 60 TLSs, each according to what preactivation was going to be used, concentrated bends or gradual curvature. Subgroup 1 was tested immediately and the remaining subgroups were tested after they were secured at 5-mm activation for different periods of time in an interbracket distance of 23 mm. Subgroups 2, 3, 4, 5, and 6 were kept activated for 24, 48, and 72 hours, 1 and 2 weeks, respectively. Using a moment transducer coupled to a digital extensometer indicator adapted to a universal testing machine, the amount of horizontal force, moment, and moment-to-force (MF) ratios were recorded. ResultsBoth groups showed a decrease in force levels over time (P < 0.001 and 0.005 for bend and curvature preactivation, respectively), but with different behaviors. The group preactivated by bends showed a reduction in moments over time (P < 0.001), whereas the group preactivated by curvature did not (P = 0.410). The MF ratio has not changed over time in either group. ConclusionsThe stress-relaxation effect is more evident on group preactivated by bends.

T形スプリングを用いた歯列の一括移動におけるループ位置,トランスパラタルアーチ,臼歯列の歯数の影響 : 有限要素法による解析

T形スプリングを用いた歯列の一括移動におけるループ位置,トランスパラタルアーチ,臼歯列の歯数の影響 : 有限要素法による解析

Stability of beta-titanium T-loop springs preactivated by gradual curvature.

ABSTRACTObjective: Evaluate changes in the force system of T-Loop Springs (TLS) preactivated by curvature, due to stress relaxation. Methods: Ninety TLSs measuring 6 x 10 mm, produced out with 0.017 x 0.025-in TMA® wire and preactived by gradual curvature, were randomly distributed into nine groups according to time point of evaluation. Group 1 was tested immediately after spring preactivation and stress relief, by trial activation. The other eight groups were tested after 24, 48 and 72 hours, 1, 2, 4, 8 and 12 weeks, respectively. Using a moment transducer coupled to a digital extensometer indicator adapted to a universal testing machine, the amount of horizontal force, moment and moment-to-force ratios were recorded at every 0.5 mm of deactivation from 5 mm of the initial activation, in an interbracket distance of 23 mm. Results: The horizontal forces decreased gradually among the groups (p< 0.001) and the moments showed a significant and slow decrease over time among the groups (p< 0.001). All groups produced similar M/F ratios (p= 0.532), with no influence of time. Conclusions: The TLSs preactivated by curvature suffered a gradual deformation over time, which affected the force system, specifically the moments, which affected the horizontal forces produced.

Nickel titanium T-loop wire dimensions for en masse retraction.

To compare the force system produced by nickel-titanium T-loop springs made with wires of different dimensions. Thirty compound T-loop springs were divided into three groups according to the dimensions of the nickel-titanium wire used for its design: 0.016" × 0.022", 0.017" × 0.025", and 0.018" × 0.025". The loops were tested on the Orthodontic Force Tester machine at an interbracket distance of 23 mm and activated 9 mm. The force in the y-axis and the moment in the x-axis were registered while the calculated moment to force ratio was recorded at each .5 mm of deactivation. The data were analyzed by three analyses of variance of repeated measures to detect differences and interactions between deactivation and wire size on force, moment, and moment-force ratios (M/F). All groups had significantly different forces (P < .001). The 0.016" × 0.022" wire produced 1.78N of force while the 0.017" × 0.025" and the 0.018" × 0.025" produced 2.81 N and 3.25 N, respectively. The 0.016" × 0.022" wire produced lower moments (11.6 Nmm) than the 0.017" × 0.025" and 0.018" × 0.025" wires, which produced similar moments (13.9 Nmm and 14.4Nmm, respectively). The M/F produced was different for all groups; 0.016" × 0.022" T-loops produced 6.7 mm while the 0.017" × 0.025" and 0.018" × 0.025" T-loops produced 5.0 mm and 4.5 mm, respectively. An interaction was detected for all variables between deactivation and groups. The larger wires tested produced higher forces with slight increase on the moments, but the M/F produced by the 0.016" × 0.022" wire was the highest found.

Differences in the force system delivered by different beta-titanium wires in elaborate designs.

Objective: Evaluation of the force system produced by four brands of b-Ti wires bent into an elaborate design. Methods: A total of 40 T-loop springs (TLS) hand-bent from 0.017 x 0.025-in b-Ti were randomly divided into four groups according to wire brand: TMATM(G1), BETA FLEXYTM (G2), BETA III WIRETM (G3) and BETA CNATM (G4). Forces and moments were recorded by a moment transducer, coupled to a digital extensometer indicator adapted to a testing machine, every 0.5 mm of deactivation from 5 mm of the initial activation. The moment-to-force (MF) ratio, the overlapping of the vertical extensions of the TLSs and the load-deflection (LD) ratio were also calculated. To complement the results, the Young's module (YM) of each wire was determined by the slope of the load-deflection graph of a tensile test. The surface chemical composition was also evaluated by an energy dispersive X-ray fluorescence spectrometer. Results: All groups, except for G2, produced similar force levels initially. G3 produced the highest LD rates and G1 and G4 had similar amounts of overlap of the vertical extensions of the TLSs in "neutral position". G1 and G3 delivered the highest levels of moments, and G2 and G3 produced the highest MF ratios. b-Ti wires from G3 produced the highest YM and all groups showed similar composition, except for G2. Conclusion: The four beta-titanium wires analyzed produced different force systems when used in a more elaborate design due to the fact that each wire responds differently to bends.

Effects of stress relaxation in beta-titanium orthodontic loops: Part II.

To determine which regions of beta-titanium T-loop springs (TLSs) are more affected by the stress relaxation over a 12-week period. Fifty TLS were previously activated by concentrated bends and divided into five groups of 10 each according to their evaluation periods: immediate assessment (G0), 24 hours (G1), 48 hours (G2), 1 week (G3), and 12 weeks (G4). Groups 1 to 4 were mounted into a structure simulating a clinical situation. After the experimental periods, the springs were scanned for measurement of their angles and numbered from 1 to 9. A two-way analysis of variance was used to detect differences among the angles measured and differences caused by time and also to detect interactions between those two factors. Tukey's test was used to find differences among the groups. Time influenced the angulations of the TLSs (P < .001). Tukey post hoc test showed that G0 (84.1°) presented a different profile, whereas G1 (90.2°), G2 (90.7°), and G3 (91.1°) had similar profiles among each other, with G4 (92.6°) showing a mean value different from all other groups. A significant interaction was detected between activation time and angular deformation in the TLSs (P < .01). Stress relaxation was observed in the TLSs. It was greatest within 24 hours and gradually increased up to 12 weeks. Two regions were identified as responsible for the relaxation of the TLSs: one at the bend between the vertical extensions of the springs and the base arch and the other at the preactivation bends made in the base arch.

Photoelastic analysis of forces generated by T-loop springs made with stainless steel or titanium-molybdenum alloy

The purpose of this study was to use photoelastic analysis to compare the system of forces generated by retraction T-loop springs made with stainless steel and titanium-molybdenum alloy (TMA) (Ormco, Glendora, Calif) with photoelastic analysis. Three photoelastic models were used to evaluate retraction T-loop springs with the same preactivations in 2 groups. In group 1, the loop was constructed with a stainless steel wire, and 2 helicoids were incorporated on top of the T-loop; in group 2, it was made with TMA and no helicoids. Upon using the qualitative analysis of the fringe order in the photoelastic model, it was observed that the magnitude of force generated by the springs in group 1 was significantly higher than that in group 2. However, both had symmetry for the active and reactive units related to the system of force. Both springs had the same mechanical characteristics. TMA springs showed lower force levels.

Force system evaluation of symmetrical beta-titanium T-loop springs preactivated by curvature and concentrated bends

The objective of this research was to compare the effect of preactivation on the force system of beta-titanium T-loop springs (TLSs). Twenty TLSs with dimensions of 6 × 10 mm, of 0.017 × 0.025-in beta-titanium alloy, were randomly divided into 2 groups according to their preactivation. By using a moment transducer coupled to a digital extensometer indicator adapted to a testing machine, the amounts of horizontal force and moment produced were recorded at every 0.5 mm of deactivation from 5 mm of the initial activation in an interbracket distance of 23 mm. The moment-to-force ratio, the "neutral position" and the load-deflection ratio were also calculated. TLSs preactivated by curvature delivered horizontal forces significantly lower than those preactivated by concentrated bends. No differences were found in relation to the moments produced throughout the deactivation of both groups. The moment-to-force ratios were systematically higher on the TLSs preactivated by curvature than those preactivated by concentrated bends, except on 5 mm of activation. Significant differences were found in the load-deflection rates and "neutral position." The TLSs preactivated by curvature delivered lower horizontal forces and higher moment-to-force and load-deflection ratios than did those preactivated by concentrated bends.

Numerical simulations of canine retraction with T-loop springs based on the updated moment-to-force ratio

The purpose of this study was to develop a new finite element method for simulating long-term tooth movements and to compare the movement process occurring in canine retraction using a T-loop spring having large bends and with that having small bends. Orthodontic tooth movement was assumed to occur in the same manner as the initial tooth movement, which was controlled by the moment-to-force (M/F) ratios acting on the tooth. The M/F ratios were calculated as the reaction forces from the spring ends. For these M/F ratios, the teeth were moved based on the initial tooth movements, which were calculated by using the bilinear elastic model of the periodontal ligament. Repeating these calculations, the teeth were moved step by step while updating the M/F ratio. In the spring with large bends, the canine at first moved bodily, followed by root distal tipping. The bodily movement was quickly achieved, but over a short distance. In the spring with small bends, the canine at first rotated and root mesial tipping occurred, subsequently the canine uprighted and the rotation decreased. After a long time elapsed, the canine moved bodily over a long distance. It was found that the long-term tooth movement produced by the T-loop springs could be simulated by the method proposed in this study. The force system acting on the teeth and the movement type remarkably changed during the long-term tooth movement. The spring with large bends could move the canine bodily faster than that with small bends.

Changes over time in canine retraction: An implant study

The objective of this study was to analyze rates of canine movement over the first 2 months of continuous retraction, when rate changes are expected. Ten patients with bone markers placed in the maxilla and the mandible had their canines retracted over a 2-month period. Retraction was accomplished with beta-titanium alloy T-loop springs. Standardized 45 degrees oblique cephalograms where taken initially and every 28 days thereafter. The radiographs were scanned and digitized twice (the average was used for the analyses). The radiographs were superimposed by using the bone markers and oriented on the functional occlusal plane. Paired t tests were used to compare side and jaw effects. There were no significant differences between sides. The maxillary cusp was retracted 3.2 mm, with less movement during the first (1.1 mm) than during the second 4 weeks (2.1 mm). The maxillary apices did not move horizontally. There were no significant vertical movements in the cusps and apices of the maxillary canines. The mandibular cusp was retracted 3.8 mm-1.1 mm during the first and 2.7 mm during the second 4 weeks. The mandibular apices were protracted 1.1 mm. The cusps and apices were intruded 0.6 and 0.7 mm, respectively. The only difference between jaws was the greater protraction of the mandibular apices during the second 4 weeks and in overall movement. The rate of canine cusp retraction was greater during the second than the first 4 weeks. The mandibular canines were retracted by uncontrolled tipping whereas the maxillary canines were retracted by controlled tipping.

Group A T-loop for differential moment mechanics: An implant study

When anchorage control is critical and compliance is less than ideal, efficient treatment depends on differential tooth movements. The purpose of this study was to evaluate the distal tipping of partially retracted canines and the mesial movement of the molars. Eleven patients had their maxillary and mandibular canines partially retracted with TMA (Ormco Corp, Orange, Calif) T-loop springs with 45 degrees gable bends distal to the loops preactivated for group A (maximum anchorage). Metallic bone markers served as references. The canines were retracted until enough space was available for alignment of the incisors without proclination. Oblique (45 degrees) radiographs were taken immediately before the initial activation and after partial retraction. The radiographs were scanned, superimposed on the bone markers, and measured digitally. The mandibular canine crowns were retracted (4.1 +/-1.9 mm) and intruded (0.7 +/- 0.3 mm) by uncontrolled tipping. In contrast, the maxillary canine crowns were retracted (3.2 +/- 1.4 mm) by controlled tipping. The maxillary and mandibular molars crowns were protracted by similar amounts (1.0 +/- 0.6 and 1.2 +/-1.2 mm, respectively) by controlled tipping, without significant extrusion. The molars were protracted approximately 0.3 mm for every 1 mm of canine retraction. The T-loop spring used in this investigation produced controlled tipping of the maxillary canines, but it did not produce controlled tipping of the mandibular canines or translation of the molar as expected.

Optimizing the design of preactivated titanium T-loop springs with Loop software

A TMA (Ormco Corp, Glendora, Calif) T-loop spring (TTLS), preactivated with a gable bend distal to the loop, holds promise for producing controlled tipping of the canines and translation of the posterior segment. However, there is currently no consensus as to where the preactivated gable bend or the loop should be placed, what the height of the loop should be, or how the interbracket distance changes the moments produced. Using the Loop software program (dHal, Athens, Greece), we systematically modified a .017 x .025-in TTLS (10 x 6 mm) that was preactivated with a 45 degrees gable bend distal to the loop, and simulated the effects. As the gable bend was moved posteriorly, the moment increased at the posterior bracket more than it decreased at the anterior bracket. As the loop was brought closer to the anterior bracket, the posterior moment decreased at the same rate that it increased anteriorly. As the loop was increased in size, the moments increased both posteriorly and anteriorly. As the interbracket distance increased, the posterior moment decreased, and the anterior moment remained constant. We concluded that the size of the loop should be slightly increased, to 10 x 7 mm, and it should be placed 2 mm from the anterior bracket, with a preactivation bend of 45 degrees , 4 to 5 mm from the posterior bracket (after 4 mm of activation).

Curvature Versus V-Bends in a Group B Titanium T-Loop Spring

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. 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 . 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). 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.

T-loop position and anchorage control

The effect of off-center positioning on the force system produced by segmented 0.017 × 0.025-inch TMA T-loops was measured. A T-loop was designed to produce equal and opposite moments in the centered position. The spring was tested in seven positions, centered, 1, 2, and 3 mm toward the anterior attachment, and 1, 2, and 3 mm toward the posterior attachments. The horizontal force, vertical force, and alpha and beta moments were measured over 6 mm of spring activation. The results showed that the alpha/beta moment ratio was dependent only on the spring position, and independent of spring activation. Eccentric positioning of T-loop springs effectively produces a consistent moment differential through the range of spring activation. (Am J Orthod Dentofac Orthop 1997;112:12-8.)

Molar Uprighting with T-Loop Springs

Uprighting of molars is indicated as an adjunct to restorative and periodontal procedures. Limiting conditions exist in which previously reported helical and box-loop springs cannot be used effectively. In those instances, segmental arch wires with T-loops upright the molars efficiently while maintaining control in three planes of space. Furthermore, these loop designs permit immediate engagement of these appliances. Clinical experiences with these springs by students in the professional and graduate dental clinics at the University of Kentucky College of Dentistry lead to the conclusion that: segmental uprighting arch wires with T-loops are easy to fabricate and use; T-looped uprighting springs can be engaged immediately and used efficiently in instances in which helical spring or box-loop uprighting appliances are contraindicated; T-looped uprighting springs offer excellent controlled movements of teeth in three planes of space; acceptance by the patient is favorable; and treatment time, depending on the amount of tooth movement required, is rapid and varies between 8 to 16 weeks.