Retraction Hook Research Articles

Comparative analysis of tubular retractors and hook retractors in oblique lumbar interbody fusion at the initial stage of the learning curve

PurposeOblique lumbar interbody fusion (OLIF) still has a steep learning curve that many spinal surgeons who want to develop are hesitant. The purpose of this study is to provide reference for beginners through the comparative analysis of the application of two kinds of retraction devices in the early stage of learning curve.MethodWe prospectively included the first 60 patients with lumbar degenerative diseases treated with OLIF by a surgeon in our department. According to the application of different retraction devices during the operation, the patients were divided into hook retractor group and tubular retractor group. The clinical effects and complications of the two groups were compared.ResultThe average age of hook retractor group was 62 years old, the average age of tubular retractor group was 65 years old. There was no significant difference in age, sex, operative segment, follow-up time and blood loss between the two groups. The operation time in hook retractor group was less than that in tubular retractor group. The incidence of complications in hook retractor group (11.8%) was significantly lower than that in tubular retractor group (38.5%).ConclusionThe tubular retractor group has a higher risk of neurovascular injury in the initial stage of learning, as well as the risk of vertebral fracture. In contrast, the hook retractor group has the advantages of simple method, high fault tolerance and relatively low incidence of complications. Therefore, we believe that the application of hook retractor in the early stage of OLIF learning curve is easier to increase the operator’s confidence and make OLIF more acceptable.

Finite Element Analysis of Maxillary Teeth Movement with Time during En Masse Retraction Using Orthodontic Mini-Screw

Introduction: The aim of this study was to determine the placement of an orthodontic mini-screw (OMS) and the length of an anterior retraction hook (ARH) with en masse retraction. Continuous maxillary tooth movement pattern was simulated by finite element analysis (FEA). Materials and methods: Extraction of the first premolar was hypothesized with a finite element model. The placement of OMS was analyzed for the following two groups: (1) a high OMS (HOMS) group with OMS placed horizontally at the mesial side of the second premolar and apically 10 mm above the arch wire, and (2) a low OMS (LOMS) group with OMS placed horizontally between the second premolar and the first molar and apically 8 mm above the arch wire. According to the height of ARH, each group was divided into three subgroups. Results: When the extraction space of the first premolar was closed, anterior teeth were intruded in the HOMS group but extruded in the LOMS group. In all cases, the first molar was intruded. According to the intrusion of the first molar and extrusion of anterior teeth, the occlusal plane rotated clockwise (CW) in the LOMS group. However, in the HOMS1 group, the occlusal plane rotated counterclockwise (CCW) due to more intrusion of anterior teeth than that of the first molar. Conclusion: By analyzing six cases of different OMS and ARH, changes of incisor and molar in en masse retraction with the extraction of the first premolar could be predicted. In addition, OMS placement and ARH length can be determined based on results of incisal showing. This study can also help esthetic orthodontic results.

Digital Photoelastic Analysis of TAD-Supported Maxillary Arch Distalization

The objective of this study was to determine whether the distribution of compressional and tensional stress around tooth roots is influenced by the position of a temporary anchorage device and the length of the retraction hook during the distalization of the maxillary dentition. A photoelastic orthodontic model was made of photoelastic epoxy resin. Six combinations of three retraction hook lengths and two posterior Temporary skeletal anchorage devices (TAD) positions were established. Stress was applied through an elastic chain for each of the combinations. Digital photoelastic stress analysis measured the compression, tensional stress, and direction around the tooth root. Using this novel photoelastic model, we found that the distribution of compressional and tensional stress during the retraction of the maxillary dentition was significantly influenced by the position of the TAD and the length of the retraction hook.

Evaluation of Orthodontic Mini-implant-anchored en masse Retraction of Maxillary Anterior Teeth with Reduced Bone Support: A Prospective Finite Element Analysis Study

The purpose of this study was to evaluate force systems to bring about the en masse retraction of maxillary anterior teeth having reduced bone levels using finite element analysis. This is a prospective study. Three-dimensional finite element models of maxillary dentition having normal alveolar bone level and 2, 4, and 6 mm bone loss with first premolar extraction were constructed from a spiral CT scan of a skull. Archwire and brackets were modeled on the facial surfaces of teeth. Retraction force of 175 gm was applied from an orthodontic mini-implant placed bilaterally between the second premolar and first molar and 12 mm above plane of the archwire to anterior retraction hook (ARH) fixed at two heights of 6 and 10 mm above the archwire. Maximum displacement and periodontal ligament (PDL) stress were calculated for different combinations of bone levels and ARH. As the bone loss increased, the tipping tendency, amount of intrusion, and maximum von Mises stress in PDL also increased, showing a direct correlation. To minimize tipping and PDL stress, the height of ARH should be increased in alveolar bone loss conditions to allow retraction force to pass through or even above the center of resistance of anterior teeth. Even then, pure bodily retraction may not be achieved, but tipping tendency can be reduced. Nevertheless, it may not be suitable to increase ARH beyond a limit owing to chances of irritation to the vestibular mucosa. Alternative methods should be contemplated to reduce the tipping behavior. The alternative is to apply a lighter retraction force to reduce lingual tipping. A higher counter-moment in the archwire or bracket can also be incorporated.

The effect of varied force vector on type of tooth movement of maxillary anterior teeth during en masse retraction; randomized clinical trial

This randomized clinical trial was conducted on female patients in need of extraction of at least of two maxillary first premolars. The sample was divided into three groups; Group I: study group with Anterior retraction hook (ARH) of 9 mm, group II: study group with ARH of 6 mm, group III: study group with ARH of 3mm. Cone beam computed tomography were taken at two-time intervals for the whole sample; T1: Before the onset of en-masse retraction and T2: After the completion of en-masse retraction.Significant reduction in the inclination of anterior teeth as measured to the palatal plane had been recorded in three groups. Significant retraction of crowns and roots of anterior teeth had been recorded in all groups. Significantly lower amount of root movement had been recorded in group 2 and 3 compared to group 1. All groups showed significant intrusive movement with significantly less intrusion movement in group 2 and group 3 compared to group 1.

The Effect of Varied Positioning of Mini-screw, Anterior Retraction Hook, and Resultant Force Vector on Efficient En-Masse Retraction Using Finite Element Method: A Systematic Review

Objective: The objective of this systematic review was to assess the available evidence to evaluate the effectiveness of en-masse retraction design with mini-screw with respect to the retraction hook and mini-implant position and height. Methods: The following electronic databases were searched till July 31, 2020: Pro-Quest Dissertation Abstracts and Thesis database Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Google Scholar, US National Library of Medicine, and National Research Register. En-masse retractions with anterior retraction hooks assisted by mini-implant three-dimensional finite element method (3D FEM) models were included in the study. The selected studies were assessed for the risk of bias using the Cochrane Collaboration risk of bias tool. The “traffic plot” and “weighted plot” risk of bias distribution were designed using the ROBVIS tool. The authors extracted and analyzed the data. Results: Twelve studies fulfilled the inclusion criteria. The risks of biases were low for 9 studies and high for 3 studies. Data on mini-implant, retraction hook, and the center of resistance/force vectors were extracted. The outcomes of the included studies were heterogeneous. Conclusions: According to the currently available literature review for successful bodily en-masse tooth movement, the force vector should pass through the center of resistance, which can be achieved by the clinical judgment of placing a mini-screw and an anterior retraction hook. The force from an implant placed at a higher level from the anterior retraction hook will cause intrusion; an implant placed at the medium level shows bodily movement; and an implant placed at a lower level shows tipping forces in consolidated arches.

Three-Dimensional Finite Element Analysis for Stress Distribution During Intrusion and Retraction Using Orthodontic Mini-implants

Background and Objectives: the study was conducted to evaluate the levels of stress produced in and around implants when placed at different sites for retraction and intrusion of maxillary anteriors. The other objective was to evaluate stress levels produced at implant bone interface when mini implants were placed at different angulations at the same site. Materials and Methodology: Finite element model of the maxilla and maxillary dentition was constructed using the CT skull of subject used in the study. All the accessories used like mini-implants, stainless steel wire, coil springs etc were scanned separately for obtaining detailed anatomic features. The force was given between retraction hook and mini -implant using NITI closed coil spring for intrusion and retraction of maxillary anterior teeth. The basic mechanical factors i.e. the stresses developed in mini implant, the angle of insertion of the mini implant into the bone surface were analyzed. Finite Element model was generated by Hyper mesh 9.0 software. Analysis was carried out by using Ansys 12.1 software. Results and Conclusion: All the set objectives were accomplished at the end of the study which included complete closure of extraction space by retraction and intrusion in the models. The following conclusions were drawn: The least stress was seen on an implant at middle third, when inserted at an angle of 800 to the bone surface, with application of 50-100mg of intrusive force on anterior implant and 200 gms of retractive force on posterior implant.

Evaluation of stress pattern in periodontium and change in inclination during en masse retraction: Finite element analysis

ObjectiveUnderstanding the effects of retraction accompanied by intrusion on the periodontium of the anterior teeth along with the change in displacement during the en masse retraction of the maxillary anteriors using orthodontic mini-implants (OMIs) and retraction hooks at different levels. DesignFinite element analysis. Materials and methodThe finite element model of maxillary dentition was made using a computed tomographic scan. The implants of 1.5 × 8.0-mm dimensions were inserted at an angle of 90° at distance of 7 mm (low OMI) and10 mm (high OMI) with anterior retraction hooks (ARH) at 3, 6, and 9 mm. Six models were constructed for the study. After the boundary conditions were defined, 200 g of retractive force was applied from ARH at low and high OMI traction. The stresses on periodontal ligament (PDL), bone, bone surrounding implant, and cementum, along with change in inclination and displacements of anterior and posterior teeth along the y- and z-axis were determined. ResultsAn overall tipping and extrusion was seen in all the cases. Low OMI placement with retraction hooks at 3 mm and 6 mm showed more tipping movements, whereas high OMI with 9-mm ARH showed more bodily movement. Both high and low OMI with 9-mm ARH showed more root movement. The stresses in PDL, bone, and cementum were less at 3-mm ARH in both low and high OMI groups. The stresses were more in cortical bone than cancellous bone and also more on lateral incisors than central incisors. ConclusionIf controlled lingual tipping of anterior teeth is required with minimum torque loss, high OMI with low ARH is recommended, whereas if lingual root movements with retraction is required, high OMI and high ARH is recommended.

Evaluation of initial displacement and stresses in the maxillary dentition following en masse retraction using fixed lingual appliance and micro-implants: A finite element analysis

To evaluate and compare the stress and displacement pattern between conventional and micro-implant supported retraction in lingual orthodontic system. A finite element model of the maxilla, teeth, periodontal ligament, lingual-orthodontic appliance and a micro-implant complex was constructed using ANSYS 12.1 software. Two sizes of micro-implants, 6mm and 8mm, were constructed producing a simulated model of 99,190 nodes and 32,4364 elements. A retraction force of 200g was applied from an anterior retraction hook to the molar tube in the conventional model and from the micro-implants in the implant supported model. The initial displacement and stress patterns in the X-Y-Z axes were obtained using Hyper-view software. The maximum von Mises stresses in the 6mm, 8mm and conventional model were 22.164 Megapascals (MPa), 28.603MPa and 16.491MPa respectively. The bucco-lingual displacement of the maxillary anteriors was greater in the 8mm implant model with 23×10-3mm lingual displacement observed. The least lingual displacement of 11×10-3mm was noted for the conventional model while a slightly higher moderate reading of 15×10-3mm was seen in the 6mm micro-implant supported model. The maximum displacement of the periodontal ligament was noted in the 8mm micro-implant model. Within the limitations of this research, the 8mm micro-implant model displayed high initial stresses and greater initial displacement of the anterior teeth in the X-Y-Z coordinates in comparison to conventional retraction method.

Design and Evaluation of a Novel Hybrid Soft Surgical Gripper for Safe Digital Nerve Manipulation.

Forceps are essential tools for digital nerve manipulation during digital nerve repair surgery. However, surgeons have to operate forceps with extreme caution to prevent detrimental post-operative complications caused by over-gripping force. Their intrinsically safe characteristics have led to the increasing adoption of soft robotics in various biomedical applications. In this paper, a miniaturized hybrid soft surgical gripper is proposed for safe nerve manipulation in digital nerve repair surgery. This new surgical gripper includes a soft inflatable actuator and a gripper shell with a hook-shaped structure. The ability to achieve a compliant grip and safe interaction with digital nerves is provided by the inflated soft pneumatic actuator, while the rigid hook retractor still allows surgeons to scoop up the nerve from its surrounding tissues during surgery. The performance of the proposed surgical gripper was evaluated by the contact/pulling force sensing experiments and deformation measurement experiments. In the cadaver experiments, this new surgical gripper was able to complete the required nerve manipulation within the limited working space. The average deformation of the digital nerve with an average diameter of 1.45 mm gripped by the proposed surgical gripper is less than 0.22 mm. The average deformity is less than 15% of its original diameter.

Evaluation of stress generation on the cortical bone and the palatal micro-implant complex during the implant-supported en masse retraction in lingual orthodontic technique using the FEM: Original research.

Background. This study aimed to evaluate and analyze the distribution of stresses on the palatal micro-implants and the cortical bone at the micro-implant site with optimal orthodontic retraction force in lingual orthodontics. Methods. ANSYS 12.1 software was used to construct the finite element model of the maxillary bone, teeth and the periodontal ligament along with the lingual bracket set-up with wire and the micro-implant. Six- and 8-mm micro-implants were constructed. The final model consisted of 99190 nodes and 324364 elements. A 200-gram of retraction force was applied from the micro-implant to the anterior retraction hook. The micro-implant was embedded between the second premolar and the first molar. Hyper-view software was used to get the results in X-Y-Z dimensions. Results. The maximum von Mises stresses detected were 52.543 MPa for 6-mm micro-implant and 54.489 MPa for 8-mm micro-implant. Maximum stress was at the neck of the micro-implant. The 8-mm implant model showed 6×10-3 mm of lingual displacement. The least displacement of 1×10-3 mm was noticed for both the implant models in the apico-occlusal direction. The maximum von Mises stresses in the cortical bone at the micro-implant site was 18.875 MPa for 6-mm micro-implant and 21.551 MPa for 8-mm micro-implant. Conclusion. Six-mm micro-implant can be the choice for the implant-supported lingual orthodontic retraction as it produced minimal stresses on the cortical bone, and the initial stress displacements produced on the micro-implant were also minimal.

Type of tooth movement during en masse retraction of the maxillary anterior teeth using labial versus lingual biocreative therapy in adults: A randomized clinical trial.

ObjectiveThe objective of this two-arm parallel trial was to compare the type of tooth movement during en masse retraction of the maxillary anterior teeth using labial versus lingual biocreative therapy.MethodsTwenty-eight subjects were randomized in a 1 : 1 ratio to either the labial or lingual group. En masse anterior retraction was performed using labial biocreative therapy in group A and lingual biocreative therapy in group B. Cone beam computed tomography scans were taken before and after retraction and the primary outcome was the type of tooth movement during anterior retraction. Data were analyzed using paired t-tests for comparisons within each group and independent-sample t-test for comparison of the mean treatment changes between the two groups.ResultsSignificant differences were found between the two groups in relation to the type of tooth movement (labiolingual inclination of the central incisor; mean difference, 5.85 ± 1.85°). The canine showed significant distal tipping in the lingual group (mean difference, 6.98 ± 1.25°). The canine was significantly more intruded in the lingual group (mean difference, 1.67 ± 0.49 mm). Good anchorage control and significant soft tissue changes occurred in both groups. No serious adverse effects were detected.ConclusionsWith a 10-mm retraction hook, the labial biocreative technique with the reverse curve overlay provided anterior retraction with good torque control, while in the lingual group, anterior retraction occurred with controlled tipping movement with significant distal tipping and intrusion of the canine (trial registration: The trial was registered at ClinicalTrials.gov [NCT03239275]).

Stress Distribution and Displacement of Maxillary Anterior Teeth During En-masse Intrusion and Retraction: A FEM Study

Background: Space closure by en masse intrusion and retraction in orthodontics is of particular interest. Aim: The aim of this study was to evaluate the stress distribution and displacement of maxillary anterior teeth. Materials and Methods: Four different finite element models of maxillary arch were constructed to understand the nature of stresses and displacement patterns of anterior teeth during en masse intrusion and retraction on force application with different combinations of mini-implants and retraction hooks. Results: In this study, tensile stresses were seen in the cervical region and various movements of teeth such as lingual crown tipping, bodily movement, lingual root tipping, intrusion, and extrusion were observed. Conclusion: Nature of stresses changes from tensile to compressive from cervical area to apical area. Various tooth displacements suggest that different combinations of mini-implants and retraction hooks affect the direction of the tooth movement.

Evaluating the effects of consolidation on intrusion and retraction using temporary anchorage devices\u2014a FEM study

BackgroundExtraction of premolars and retracting the anterior teeth using mini-implants and anterior retraction hooks became advent now a day. In such treatments, consolidation of arches is not done in regular practice. So, the present study is concentrated on effects of consolidation in two implant and three implant combinations of retraction and intrusion.MethodsA three-dimensional FEM model of maxillary teeth and periodontal ligament housed in the alveolar bone with the first premolars extracted is generated with appropriate number of elements and nodes. The models were broadly divided into two groups according to the no. of implants. Mini-implants were placed bilaterally between the second premolar and molar at varying heights (7, 10, 13 mm) in group I, and along with bilateral implants, an additional mid-implant is placed between the central incisors as group II. Brackets with 0.022 slot were placed on the teeth, 19 × 25 SS wire is placed in the brackets, an anterior retraction hook was placed at 9 mm height, and analysis was done to evaluate the stresses and displacement patterns in consolidation and non-consolidation models.ResultsThe results showed that consolidation of the anterior teeth during intrusion and retraction shows various advantages such as less stresses on the bone, PDL, implant, teeth, and no labial flaring of the anterior teeth and three implant system, i.e., two bilateral implant at 10 mm and a mid-implant at 12 mm between the centrals has shown to be better than other models as bodily movement is observed.ConclusionConsolidation is better than non consolidation during enmasse retraction and intrusion.

Finite element analysis of different load mode on tooth movement for space closure in patient with bimaxillary protrusion

To investigate the stress distribution on the maxillary anterior teeth retracted with sliding mechanics and micro-implant anchorage using different retraction hook heights and positions. DICOM image data including maxilla and upper teeth were obtained with cone-beam CT. The three-dimensional finite element model was constructed using Mimics software. Brackets and archwire model were constructed using Creo software. The models were instantiated using Pro/Engineer software. Abaqus software was used to simulate the sliding mechanics by loading 2 N force on 0, 2, 4, 6, 8, 10 mm retraction hooks and three different positions, repectively. Rotation of the occlusal plane, the initial displacement and stress distribution of teeth were analyzed. Lingual rotation of maxillary central incisor(0.021°), gingival movement of the maxillary first molar(0.005 mm), and clockwise rotation of the maxillary occlusal plane(0.012°) were observed when the force application point located at the archwire level (0 mm). In contrast, 0.235° labial rotation of the maxillary central incisor, 0.015 mm occlusal movement of the maxillary first molar, and 0.075° anti-clockwise rotation of the maxillary occlusal plane were observed when the force application point located at the higher level(10 mm retraction hook). The more the force application point was located posteriorly at the archwire level, the less lingual rotation of the maxillary central incisor and the more buccal displacement of maxillary first molar was observed. Maxillary anterior tooth rotation and retraction, vertical displacement of posterior segment, and rotation of the occlusal plane could be controlled by adjusting the height and position of the retraction hook in space closure using miniscrew and sliding mechanics.

Finite element analysis of maxillary incisor displacement during en-masse retraction according to orthodontic mini-implant position.

ObjectiveOrthodontic mini-implants (OMI) generate various horizontal and vertical force vectors and moments according to their insertion positions. This study aimed to help select ideal biomechanics during maxillary incisor retraction by varying the length in the anterior retraction hook (ARH) and OMI position.MethodsTwo extraction models were constructed to analyze the three-dimentional finite element: a first premolar extraction model (Model 1, M1) and a residual 1-mm space post-extraction model (Model 2, M2). The OMI position was set at a height of 8 mm from the arch wire between the second maxillary premolar and the first molar (low OMI traction) or at a 12-mm height in the mesial second maxillary premolar (high OMI traction). Retraction force vectors of 200 g from the ARH (-1, +1, +3, and +6 mm) at low or high OMI traction were resolved into X-, Y-, and Z-axis components.ResultsIn M1 (low and high OMI traction) and M2 (low OMI traction), the maxillary incisor tip was extruded, but the apex was intruded, and the occlusal plane was rotated clockwise. Significant intrusion and counter-clockwise rotation in the occlusal plane were observed under high OMI traction and -1 mm ARH in M2.ConclusionsThis study observed orthodontic tooth movement according to the OMI position and ARH height, and M2 under high OMI traction with short ARH showed retraction with maxillary incisor intrusion.

Distalization pattern of whole maxillary dentition according to force application points.

ObjectiveThe purpose of this study was to observe stress distribution and displacement patterns of the entire maxillary arch with regard to distalizing force vectors applied from interdental miniscrews.MethodsA standard three-dimensional finite element model was constructed to simulate the maxillary teeth, periodontal ligament, and alveolar process. The displacement of each tooth was calculated on x, y, and z axes, and the von Mises stress distribution was visualized using color-coded scales.ResultsA single distalizing force at the archwire level induced lingual inclination of the anterior segment, and slight intrusive distal tipping of the posterior segment. In contrast, force at the high level of the retraction hook resulted in lingual root movement of the anterior segment, and extrusive distal translation of the posterior segment. As the force application point was located posteriorly along the archwire, the likelihood of extrusive lingual inclination of the anterior segment increased, and the vertical component of the force led to intrusion and buccal tipping of the posterior segment. Rotation of the occlusal plane was dependent on the relationship between the line of force and the possible center of resistance of the entire arch.ConclusionsDisplacement of the entire arch may be dictated by a direct relationship between the center of resistance of the whole arch and the line of action generated between the miniscrews and force application points at the archwire, which makes the total arch movement highly predictable.

Laparoendoscopic single-site distal pancreatectomy in pigs.

To explore the technique for laparoendoscopic single-site distal pancreatectomy. Laparoendoscopic single-site spleen-preserving distal pancreatectomy was performed in pigs using a novel flexible multichannel port, a curved laparoscopic multifunctional operative device and a fish hook retractor, which provided a favorable operative field. Six pigs were involved in this study, and five survived the procedure. The first animal died following injury to the superior mesenteric vein and uncontrolled intraoperative bleeding. Except for this failure, the mean operative time was 155 min (range: 102-236 min). A steep learning curve was observed in the study, with a mean operative time of 177 min in the first two operations vs 134 min in the last three operations. The mean blood loss was 50 mL, and the postoperative course was uneventful. The animals were sacrificed three weeks after the procedures, and no pancreatic leakage or abdominal infection was found macroscopically. Laparoendoscopic single-site distal pancreatectomy is a safe and feasible procedure and can be implemented in humans in selected cases at qualified surgical centers.

Torque Loss in En-Masse Retraction of Maxillary Anterior Teeth Using Miniimplants with Force Vectors at Different Levels: 3D FEM Study.

This FEM study was conducted to quantify the amount of torque loss in maxillary anterior teeth by applying force vectors from different levels to the anterior retraction hook at various heights and comparing with that of molar anchorage system. Five 3D FEM models were constructed with force vectors at different levels: HOT-High Orthodontic Traction (13.5mm from archwire) to ARH1- Anterior Retraction Hook (5mm), HOT to ARH2 (8mm), LOT- Low Orthodontic Traction (8 mm) to ARH1, LOT to ARH2 and from conventional molar hook to ARH1. Mini-implants were placed buccally between the roots of second premolar and first molar. Torque loss was calculated by measuring the displacement of the teeth at crown tip and root apex in two planes i.e. sagittal and vertical using Y and Z axis respectively in all the five models. The results were statistically analyzed by using Kruskal Wallis ANOVA and Mann-Whitney U-test. HOT to ARH1 showed that the anterior teeth moved bodily (p =0.5127), followed by molar hook - ARH1(p=0.0495*) which showed mild uncontrolled tipping. Whereas the HOT- ARH2, LOT - ARH1,and LOT - ARH2 models exhibited uncontrolled tipping with maximum torque loss in LOT - ARH1 (p=0.0001*). It can be concluded that bodily movement with very minimal torque loss was observed in HOT-ARH1 model whereas the maximum torque loss was recorded in LOT-ARH2 model. Conventional molar anchorage group showed uncontrolled tipping with some amount of extrusion and anchor loss of posteriors.

Evaluation of Optimal Implant Positions and Height of Retraction Hook for Intrusive and Bodily Movement of Anterior Teeth in Sliding Mechanics: A FEM Study

Evaluation of Optimal Implant Positions and Height of Retraction Hook for Intrusive and Bodily Movement of Anterior Teeth in Sliding Mechanics: A FEM Study