Retraction Spring Research Articles

Comparison of retraction efficacy of titanium-molybdenum and titanium-niobium alloy wires – A prospective split-mouth study

Objectives: The study aimed to compare the efficacy of Titanium-Molybdenum (Ti-Mo) and Titanium-Niobium (Ti-Nb) alloy wires as retraction springs, by comparing: The amount and rate of canine retraction, the degree of canine rotation, the change in axial inclination of canines, and the associated anchorage loss. Material and Methods: All 17 participants (age: 18–25 years) to be treated with the first premolar extraction approach by canine retraction were assigned Ti-Mo and Ti-Nb alloy T-loop springs to either of the upper quadrants randomly. Digital intraoral 3-D scans and panoramic radiographs orthopantomagram (OPG) were taken before (T0) and after (T1) the study period (4 months). 3-D superimposition was performed and using the digital models and OPG, changes in canine position, angulation, and anchorage loss were compared between the two groups. Results: There was no significant difference between the two treatment groups for all the parameters pertaining to maxillary canine retraction, that is, canine retraction (P = 0.72), change in axial inclination of canines (P = 0.71), rotation of canines (P = 0.74), and anchorage loss (P = 0.13) as well as extraction space closure (P = 0.74). Conclusion: Ti-Nb and Ti-Mo alloy wires show a similar potency for use in retraction mechanics for orthodontic space closure.

Effect of light-emitting photobiomodulation therapy on the rate of orthodontic tooth movement : Arandomized controlled clinical trial.

The aim of this study was to evaluate the effect of light-emitting photobiomodulation therapy (LPT) on the rate of canine distalization. This study was performed on 60extraction spaces formed by extraction of the upper first premolars of 30patients (15 in the LPT group and 15in the control group). Paul Gjessing (PG)-segmented canine retraction springs were used for canine distalization. In the LPT group, the Biolux OrthoPulse™ (Biolux Research Ltd, Vancouver, Canada) intraoral device (wavelength 850 nm LED light and an energy density of 63 mW/cm2 [±13 mW/cm2]) was used for 5min per day over a period of 84days. For each patient, the diagnosis was based on standard orthodontic documentation with photographs, digital model casts, and cephalometric and panoramic radiographs. The anchorage loss, canine rotations, canine inclinations, and molar inclinations were also evaluated on plaster models obtained on days 0, 21, 42, 63, and 84. The models were measured by using 3Shape OrthoAnalyzer software (3Shape, Copenhagen, Denmark). Measurements were made by a researcher and a blinded clinician. For statistical comparison, a paired-samples t‑test and one-way analysis of variance (ANOVA) were used at the p < 0.05 level. The mean canine distalization rates were 1.36 mm/21days and 1.02 mm/21days in the LPT and control groups, respectively, and were statistically greater in the LPT group (p < 0.001). The amount of anchorage loss, canine rotations, canine inclinations and molar inclinations were not significantly different between the LPT and control groups at any of the timepoints. LPT has the potential to accelerate orthodontic tooth movement by 33%.

Canine root/cortical bone relation (CRCR) and the orthodontic tooth movement

This observational study evaluates three-dimensionally the relation between the root of maxillary canine and overlying labial cortical plate of bone during orthodontic canine retraction. Eighty-four bilateral maxillary canines in 42 patients were retracted in the extraction space of first premolars, using conventional orthodontic NiTi retraction spring delivering 150gm. Three-dimensional evaluation at the cusp tip, root apex, and the overlying cortical bone was done based on Classification of Root/Cortical bone relation (CRCR) before and after canine retraction. 168 observations of the canines pre- and post-retraction showed a mean distal movement of the canine cusp tip of 3.78(± 2.05) mm, while the canine root apex was almost stationary. Scarcely, 5.4% of the canine roots and root apices persisted in the medullary bone during retraction, while 16.1% contacted the overlying cortical bone. Fenestration of the overlying cortical bone by the canine roots or root apices occurred in 78.6% of the sample. The unembellished intimacy between the canine root and apex to the overlying thick dense cortical bone might have the decelerating effect on the maxillary canine retraction. The natural bone plate labial to the maxillary canine root did not yield infront nor enlarge due to canine retraction, but else defeated the current orthodontic biomechanical implementation.

A comparative assessment of developed novel power bridge with conventional power arm for en-masse retraction of maxillary six anterior teeth

• An intra-oral orthodontic appliance called as ‘power bridge’ is developed. • The parabolic power bridge has two arms mounted on the top surfaces of two brackets. • Parameters of power bridge and power arm are compared with finite element analysis. • Power bridge is found to be approximately 10 times safer than the power arm. • Power bridge is found to be 92 times stiffer than the power arm. For en-masse retraction of protruded maxillary six anterior teeth, power arms are attached on the archwire as a general practice to pass the force vector through centre of resistance (C res ) of maxillary six anterior teeth. As a power arm is similar to cantilever beam, it gets more deflected at free end (hook end) where retraction spring is attached. Additionally, the equivalent stresses at base of power arm increases due to deflection of power arm. The developed novel power bridge in this research study has a parabolic shape as parabolic arches can support larger load with less deformation. To verify the performance of the power bridge, finite element analysis was done to compare the results of equivalent (von-mises) stresses and total deformation of this novel power bridge and conventional power arm. The cross-sections of segments of both power bridge and power arm were kept uniform and equal to justify the results of finite element analysis. The maximum equivalent (von-mises) stress in the teeth assembly model with power arm was found to be 10.42 times greater than the teeth assembly model with power bridge. Thus, power bridge structure developed in this study can be considered as approximately 10 times safer than the power arm structure. The maximum total deformation in the teeth assembly model with power arm was found to be 92 times greater than the teeth assembly model with power bridge. Thus, power bridge structure developed in this study can be considered as 92 times stiffer than the power arm structure. So, it is clear that the power bridge structure is significantly safer and stiffer than the power arm structure. Hence, this research study suggests that the power bridge structure should be used instead of power arm once the efficacy of power bridge structure is tested and proved clinically.

Tooth Movement Efficacy of Retraction Spring Made of a New Low Elastic Modulus Material, Gum Metal, Evaluated by the Finite Element Method.

The aim of this study was to evaluate the tooth movement efficacy of retraction springs made of a new β-titanium alloy, “gum metal”, which has a low Young’s modulus and nonlinear super elasticity. Using double loop springs incorporated into an archwire made of gum metal (GUM) and titanium molybdenum alloy (TMA), the maxillary anterior teeth were moved distally to close an extraction space. The long-term movements were simulated by the finite element method. Its procedure was constructed of two steps, with the first step being the calculation of the initial tooth movement produced by elastic deformation of the periodontal ligament, and in the second step, the alveolar socket was moved by the initial tooth movement. By repeating these steps, the tooth moved by accumulating the initial tooth movement. The number of repeating calculations was equivalent to an elapsed time. In the GUM and TMA springs, the anterior teeth firstly tipped lingually, and then became upright. As a result of these movements, the canine could move bodily. The amount of space closure in GUM spring was 1.5 times that in TMA spring. The initial tipping angle of the canine in the GUM spring was larger than that in the TMA spring. The number of repeating calculations required for the bodily movement in the GUM spring was about two times that in the TMA spring. It was predicted that the speed of space closure in the GUM spring was smaller than that in the TMA spring.

3-Dimensional Retraction Spring for Buccally Impacted Canines

An innovative method to successfully erupt buccally impacted canines in difficult positions, that is, sector III and IV mesial to the root of lateral incisors into occlusion, has been described. 3-dimensional retraction spring is fabricated using 0.017 × 0.025-inch Titanium Molybdenum Alloy(TMA) wire and 45-degree bends are made simultaneously in 2 directions. The first bend is given distally starting from mesial of the first premolar and the second buccally at the same location. This 3-dimensional spring with its unique design provides the required labial and distal force with least chances of root resorption. A representative case is illustrated to demonstrate the clinical use of the same.

Tooth movement rate and anchorage lost during canine retraction: A maxillary and mandibular comparison.

To investigate the canine retraction rate and anchorage loss during canine retraction using self-ligating (SL) brackets and conventional (CV) brackets. Differences between maxillary and mandibular rates were computed. Twenty-five subjects requiring four first premolar extractions were enrolled in this split-mouth, randomized clinical trial. Each patient had one upper canine and one lower canine bonded randomly with SL brackets and the other canines with CV brackets but never on the same side. NiTi retraction springs were used to retract canines (100 g force). Maxillary and mandibular superimpositions, using cephalometric 45° oblique radiographs at the beginning and at the end of canine retraction, were used to calculate the changes and rates during canine retraction. Paired t-tests were used to compare side and jaw effects. The SL and CV brackets did not show differences related to monthly canine movement in the maxilla (0.71 mm and 0.72 mm, respectively) or in the mandible (0.54 mm and 0.60 mm, respectively). Rates of anchorage loss in the maxilla and in the mandible also did not show differences between the SL and CV brackets. Maxillary canines showed greater amount of tooth movement per month than mandibular canines (0.71 mm and 0.57 mm, respectively). SL brackets did not show faster canine retraction compared with CV brackets nor less anchorage loss. The maxillary canines showed a greater rate of tooth movement than the mandibular canines; however, no difference in anchorage loss between the maxillary and mandibular posterior segments during canine retraction was found.

Comparative evaluation of the efficiency of canine retraction using modified Marcotte and T-loop retraction springs - A split-mouth, randomized clinical trial.

OBJECTIVE:The aim of this study was to compare the efficiency of canine retraction using modified Marcotte and T-loop retraction springs.MATERIALS AND METHODS:Twenty-four subjects with a treatment plan involving bilateral extractions of upper first premolars were included in the study. A split-mouth design was used to randomly allocate opposite quadrants to either modified Marcotte spring (MS) or T-loop spring (TLS) for canine retraction. Cephalometric radiographs and models were used to measure the rate of canine retraction (primary outcome) and compare the angular/rotational changes in the canines and anchorage loss in molars (secondary outcomes) following retraction. Subjective assessment of pain and discomfort was compared using visual analog scale (VAS). Paired and independent t-tests were used to evaluate changes.RESULTS:The mean amount and rate of retraction of the canine were found to be significantly higher for MS (3.56 ± 0.696 mm and 1.188 ± 0.232 mm, respectively) when compared with TLS (2.125 ± 0.472 mm and 0.71 ± 0.157 mm, respectively). Distopalatal rotation of the canine was also significantly lesser for MS (2.42°±1.868°) than TLS (5.65° ±2.84°, P < 0.001). However, the amount of anchorage loss and canine tipping were significantly higher for MS. Statistically significant higher values in the VAS score for TLS indicated greater discomfort.CONCLUSION:MS exhibited increased rate of retraction and rotation control when compared with TLS during sectional canine retraction. Patient comfort was better for MS as evidenced by the VAS scores. However, the amount of tipping and anchorage loss obtained with MS were significantly higher than TLS.

THE EFFECTS OF INTERBRACKET DISTANCE AND GABLE BENDS ON THE FORCE AND MOMENTS IN A SEGMENTED ARCH APPROACH: A NUMERICAL-EXPERIMENTAL STUDY

The present paper verified the effect of the interbracket distance on the force system developed by orthodontic retraction springs with two delta geometries measured during space closure when spaces between teeth are present. By using a platform transducer, five different interbracket distances were tested. Also the finite element method was applied to know the von Mises stress during spring activation/deactivation process. It was concluded that the interbracket distance and spring geometry variables have not caused significant influence on the force system resulting from activations, but activation has produced a statistical difference.

The magnitude and distribution pattern of stress on implant, teeth, and periodontium under different angulations of implant placement for en masse retraction: A finite element analysis

Context: This study was undertaken to evaluate the magnitude of reactionary stresses and their pattern of distribution on implant, teeth, cortical bone, cancellous bone, and periodontal ligament (PDL) so as to determine the most favorable angle for the placement of mini implant and the most favorable force system for en masse retraction. Aims: The aim of this study is to obtain the ideal force system for en masse retraction using mini implant and to determine most favorable angle for implant insertion. Materials and Methods: DENTASCAN was used to fabricate a three-dimensional finite element model of the maxilla. Three models were constructed with different implant angulations, i.e., 45°, 60°, and 75°. Each model was applied 150, 200, 250, and 300 g of load. The results were analyzed using ANSYS software. Results: Maximum stress was observed at the head of implant at the point of attachment with the retraction spring. In cortical bone and cancellous bone, stress was distal to bone-implant interface. In PDL, maximum stress developed at the apex of lateral incisor root. Conclusion: For en masse retraction, the most favorable angulations for implant placement are 60°, and ideal force system is in the range of 200–250 g. Force levels above 300 g will possibly produce deleterious effects on PDL, cancellous bone, and teeth.

Simultaneous torquing, aligning and retraction spring: A three-dimensional approach for blocked out canines

Orthodontic management of a buccally blocked-out canine requires a substantial amount of bodily movement, which is difficult to perform because of its long and bulbous root. Even when orthodontic forces are applied in a desired direction, large hyalinized areas are created which impede the root movement. Palatal root torque is needed for the canine to increase the buccal bone thickness, decrease the risk of bone dehiscence and gingival recession. Closing loops generate a distal force along with an extrusive component which retracts the canine into the extraction space but lacks control on the torque of the canine. To overcome this limitation, this simultaneous torquing, aligning, and retraction spring was designed. It can be easily fabricated, activated at chairside for either simultaneous or sequential controlled three-dimensional tooth movements.

Measurement of strain distribution in cortical bone around miniscrew implants used for orthodontic anchorage using digital speckle pattern interferometry

An application of digital speckle pattern interferometry (DSPI) for the measurement of deformations and strain-field distributions developed in cortical bone around orthodontic miniscrew implants inserted into the human maxilla is presented. The purpose of this study is to measure and compare the strain distribution in cortical bone/miniscrew interface of human maxilla around miniscrew implants of different diameters, different implant lengths, and implants of different commercially available companies. The technique is also used to measure tilt/rotation of canine caused due to the application of retraction springs. The proposed technique has high sensitivity and enables the observation of deformation/strain distribution. In DSPI, two specklegrams are recorded corresponding to pre- and postloading of the retraction spring. The DSPI fringe pattern is observed by subtracting these two specklegrams. Optical phase was extracted using Riesz transform and the monogenic signal from a single DSPI fringe pattern. The obtained phase is used to calculate the parameters of interest such as displacement/deformation and strain/stress. The experiment was conducted on a dry human skull fulfilling the criteria of intact dental arches and all teeth present. Eight different miniscrew implants were loaded with an insertion angulation of 45 deg in the inter-radicular region of the maxillary second premolar and molar region. The loading of miniscrew implants was done with force level (150 gf) by nickel–titanium closed-coil springs (9 mm). The obtained results from DSPI reveal that implant diameter and implant length affect the displacement and strain distribution in cortical bone layer surrounding the miniscrew implant.

The effect of corticotomy on tooth movements during canine retraction

Objectives: The objective was to evaluate the effect of corticotomy/corticectomy surgery combined with fixed appliances on tooth movement during the canine retraction phase. Materials and Methods: We assessed 13 postpubertal patients (3 males and 10 females) requiring extraction of both maxillary first premolars. One side of the upper dental arch was treated with a PG retraction spring as a control, while the other side was treated with combined corticotomy/corticectomy surgery and a PG spring. A force of 100 g was used for canine retraction on both sides, with activation of the spring monthly on the control side and once every 15 days on the combined treatment side. A paired t-test was used to assess the difference between the two sides. Results: There was a small but statistically significant reduction in the duration of canine retraction (P < 0.05) and an increase in the rate of canine retraction (P < 0.05) (mm/month) in the combined treatment group. No difference in anchorage loss was observed between the groups. Tipping per millimeter of retraction was significantly different between the groups (P < 0.05). Conclusion: Corticotomy-assisted orthodontics increased the rate of tooth movement during canine retraction in 20% ratio. Relative bodily tooth movement was achieved with the corticotomy combined treatment.

Evaluation of Maxillary Canine Retraction with Remaloy Cuspid Retraction Spring

Objectives: To evaluate the efficiency of Remaloy cuspid retraction spring as a means of canine retraction. Methods: The sample was consisted of 14 female patients with age ranged from 14 to 18 years. Canine retraction was done by Remaloy canine retraction springs. For all patients the following records were made: Photographs, Upper and lower plaster casts and Radiographs. The measurements were performed using casts and lateral cephalometric radiographs taken before and after canine retraction. The collected data were analyzed statically using t-test. Results: The upper canines were retracted significantly with Remaloy cuspid retraction spring with rate 2 ± 0.17mm/m. There was a significant difference between pre and post retraction rotation angle about 22.86 ± 2.14˚. The upper canine tipping was signi ficantly increased with Remaloy cuspid retraction spring about 6 ± 1.57˚. Conclusions: The Remaloy cuspid retraction spring is effective method for canine retraction. However, the canine tipping and rotation need to decrease by increase the antitipping and antirotation angles or decrease the force utilized.

Helicopter Rotor-Blade Chord Extension Morphing Using a Centrifugally Actuated Von Mises Truss

Previous studies have shown that chord extension morphing over a spanwise section of helicopter rotor blades can reduce main rotor power requirements in stall-dominant flight conditions while being able to increase the maximum gross weight, altitude, and flight speed capability of the aircraft. This study examines a centrifugally driven, fully passive chord morphing mechanism for helicopter rotor blades. It is based on a von Mises truss connected to a rigid extension plate that deploys through a slit in the trailing edge. When the rotor revolutions per minute increases beyond a critical value, the chordwise component of centrifugal force on the assembly results in the deployment of the plate beyond the slit in the trailing edge, effectively increasing chord length. On reducing the revolutions per minute, a retraction spring pulls the plate back within the confines of the blade. This study presents the design process, iterations, and final design solution for a configuration that undergoes 20% chord extension. A prototype was fabricated and tested on the bench top as well as on a rotor test stand at rotational speeds simulating more than 60% full-scale centrifugal loads. The test results demonstrate that the concept works. However, effects such as friction lead to revolutions-per-minute requirements different from those predicted by simulation.

An Improved Puncture Access Tip-Retraction Mechanism

An Improved Puncture Access Tip-Retraction Mechanism

Are there differences on tooth movement between different sectional canine retractors?

The aim of this study was to compare the effects of two retraction springs, demonstrating differences in reactivation and constancy of force, on tooth movement during canine distalization. Upper and lower canines of 16 patients (9 females, 7 males; mean age 14.6±1.7 years) with Angle Class I or II malocclusion were included in the study. Left upper and lower canines were distalized using Poul Gjessing (PG) retractors, whereas right canines of the same patients were distalized using Hybrid retractors. Angular and linear measurements were performed on lateral cephalometric radiographs and dental models taken prior to and at the end of canine distalization. Paired Samples t-test, Repeated Measures of Analysis of Variance and Greenhouse-Geisser tests were used for statistical analysis. The mean rates of canine distalization in PG retractors were 1.03 and 0.88 mm/months and 1.13 and 0.93 mm/months for Hybrid retractors for upper and lower canines, respectively. No significant differences were detected in the rate of canine distalization, sagittal and vertical movement of canines, and first molars between retractors or arches. Despite the differences in reactivation and constancy of the forces between PG and Hybrid retractors, both revealed similar canine distalization, distal tipping, rotation, and anchorage loss of molars. As a clinical point of view, Hybrid retractors could provide more benefits due to fewer activation requirements.

Effect of bending angles in orthodontic retraction springs made from a titanium molybdenum alloy wire : A finite element analysis

Effect of bending angles in orthodontic retraction springs made from a titanium molybdenum alloy wire : A finite element analysis

Mechanical behaviour of a prototype orthodontic retraction spring: a numerical-experimental study

The purpose of this study was to examine the mechanical behaviour of orthodontic delta retraction springs. Twelve titanium-molybdenum (0.016 × 0.022 inch) delta loops were studied. The springs were analysed by means of the finite element (FE) method and experimental tests using a platform transducer. Each spring was activated from 0 to 6 mm. Statistical analysis of the data was carried out by one-way analysis of variance and Games-Howell parametric multiple comparison test for heterogeneous variances. FE analysis revealed that the stress level varied from 277 to 1273 MPa. At 6.1 mm (773 MPa), the springs were still in the elastic range. Force levels varied from 0.1 N (10 g) to 2.2 N (224 g) at 1.4-8.1 mm of activation for the numerical study and from 0.44 N (45 g) at 1 mm to 2.02 N (206 g) at 6 mm of activation in the experimental study. The spring rate was within the levels that are appropriate for clinical use (34 g/mm). Vertical forces (Fy) showed constancy and were of low magnitude. The anterior moment/force ratio from the experimental tests was 14 at 3 mm of activation decreasing to 10.7, 8.7, and 7.2, for 4, 5, and 6 mm of activation, respectively. The springs could be activated up to 7 mm without exceeding the elastic limit.

Mechanical Behavior of Various Orthodontic Retraction Springs

Retraction spring is a type of orthodontic apparatus that is used to move a tooth with respect to another by utilizing its spring back effect. It is made of metallic wire formed to individual orthodontic cases. A specific geometry results in a set of force system, consisting of forces and moments, that provides specific movement effect when it is pre-activated to the adjacent teeth. Currently, orthodontists select its geometry depending on their knowledge and experience. It is based on separate and less-than-comprehensive literatures that not all orthodontists have access to. It may result in inaccuracies in treating individual tooth retraction case. Engineering approach to estimating retraction spring structural behavior is proposed through analytical, numerical and empirical methods. Castigliano method is used as the analytical approach, whilst finite element method is used as the numerical approach. The two simulation approaches were compared to the experiments to obtain the best simulation model. The behavior of the simulation models agree well with those of experiments. Hence, the simulation models were used to simulate a large number of geometries to form database of structural behavior of retraction spring that could be used in the geometry selection by orthodontists. Orthodontic is a specialty of dentistry that is concerned with the study and treatment of malocclusions (improper teeth arrangement). It may be caused by a result of tooth irregularity ordisproportionate jaw. Retraction spring is a type of orthodontic device used for correcting the tooth position using the reaction force of the pre-tensioned spring. Certain geometry of the spring forms a certain system of forces that allows certain dental movement. With the correct selection, the treatment will take place more accurately and reducing the side- effect to the patients. In order to do so, an orthodontist selects the geometry of the retraction spring based on his/her knowledge and experience, as well as literatures. Then, a piece of raw orthodontic wire is formed to the geometry manually. The wire can be of Stainless steel (SS), Titanium molybdenum alloy (TMA), or Nickel Titanium alloy (NiTi). Manual selection and production of