Bracket Slot Research Articles

A Comparative Study of the In-Built Torque and Slot Size of MBT Prescription Bracket of Different Manufacturing Companies: A Stereo-Microscopic Study

Torque is produced by a twist in an “archwire” that creates a couple when interacted with a “bracket slot.” Depending on the magnitude of the twist, the size of the wire, the built-in torque and the size of the slot, the archwire expresses torsional forces to the teeth. When brackets are manufactured, some variations may inadvertently occur in the dimensions of the bracket slot. Hence this study was done to determine the accuracy of different manufacturer’s dimensions of bracket slots and the built-in torque. Method: Seven upper right central incisor brackets of Mclaughlin Bennet and Trevisi (MBT) prescription with 0.022-inch slot from 5 different manufacturers were taken to assess the accuracy of bracket slot dimensions and built-in torque. A stereomicroscope was used to accurately determine slot dimensions and built-in torque. Results: The results showed that all the bracket slots measured in this study were oversized when compared to the standard value. Dentaurum showed significant difference from the ideal slot size and brackets from JJ Orthodontics and Desires showed highly significance difference from ideal slot size. The mean values for built in torque were less in all the brackets. The brackets from JJ Orthodontics and Desires showed highly significant difference from the ideal built in torque values. Interpretation and Conclusion: The above findings of the study suggest that one should be cautious when choosing a commercially available brand in day to day practice as some of the materials may not fulfill the desired standards.

Finite element analysis of torque induced orthodontic bracket slot deformation in various bracket-archwire contact assembly

Background and ObjectivesOrthodontic fixed appliance therapy involves alignment of teeth through the bracket and archwires. The archwire twist (torque) imparts significant forces inside the bracket slot in refining the teeth position at the end of treatment. The objective of this in- silico study was to evaluate the torque induced bracket slot deformation in the commonly used 0.018 inch (") and 0.022" conventional Stainless Steel (SS) brackets with clinically relevant archwires during various angles of twist. MethodsSS maxillary central incisor brackets of 0.018" width × 0.022" depth (0.457 mm × 0.558 mm) and 0.022" width × 0.028" depth (0.558 mm × 0.711 mm) were used. The SS archwires of 0.016" width × 0.022" depth (0.406 mm × 0.558 mm), 0.017" width × 0.025" depth (0.431 mm × 0.635 mm), 0.019" width × 0.025" depth (0.482 mm × 0.635 mm) and 0.021" width × 0.025" depth (0.533 mm × 0.635 mm) were engaged in the respective bracket slots. The assembled bracket-archwire Finite Element (FE) models were constructed. The archwire torque, the top, middle and bottom slot deformations (TSD, MSD, BSD) were obtained for the bracket-archwire combinations for various angles of archwire twist using FE Analysis (FEA). ResultsThe torque, TSD, MSD and BSD for 30o twist of 0.016" × 0.022" archwire in 0.018" slot were 28.13 Nmm, 35.71 µm, 21.51 µm and 15.67 µm respectively, and for 0.017" × 0.025" archwire were 50.18 Nmm, 54.52 µm, 32.47 µm and 19.11 µm respectively. Similarly for 0.019" × 0.025" archwire in 0.022" slot and 0.021" × 0.025" archwire in 0.022" slot they were 38.82 Nmm, 50.78 µm, 31.47 µm and 16.82 µm, and 60.22 Nmm, 65.22 µm, 36.44 µm and 22.68 µm respectively. ConclusionsThe slot deformation was present in both 0.018" and 0.022" brackets which increased as the angle of twist increased. The TSD were higher than the MSD and BSD in all the bracket-archwire combinations. We conclude that there is only elastic deformation of bracket slots upto 30o angle of twist and clinicians could maintain within this torque limits to avoid plastic deformation leading to improper teeth position.

Stress distribution in ceramic orthodontic bracket, tooth, bone and PDL contact assembly - A finite element study

Malocclusion (teeth irregularity) problems are increasing rapidly across the world in all age groups. Malocclusion is treated in orthodontics which is a specialty of dentistry. Orthodontic bracket is a component of fixed orthodontic appliance which is used to treat the malocclusion through archwire forces transferred to the tooth. In orthodontic treatment, the preadjusted orthodontic brackets are most widely used compared to the conventional brackets as there is an in-built torque by the angulated slot walls. This study aim to compare the stress distribution in the preadjusted ceramic brackets with and without Stainless steel (SS) metal slot insert along with tooth, alveolar bone and Periodontal Ligament (PDL) contact assembly using Finite Element Analysis (FEA). A preadjusted maxillary right central incisor ceramic orthodontic bracket (with and without metal insert in the slot) are modeled using CATIA software. The solid model of a maxillary right central incisor tooth is obtained from a Computer Tomography (CT) scan using image processing software. The PDL and alveolar bone are modelled using CATIA as per the dimensions. The assembled solid model consists of bracket with and without SS metal slot insert, adhesive layer, tooth, alveolar bone and PDL. The contact between the components and the mesh is created using hypermesh software. The archwire torque is applied as couple inside the bracket slot without using an archwire. The stress distribution in the assembly components are analysed for the applied couple (torque). The stresses induced in the assembly components are compared between ceramic bracket with and without metal slot insert. This in-silico study would help the clinicians to understand the behavior of commonly used ceramic bracket with and without metal slot insert and choose the appropriate bracket for successful treatment.

An In Vitro Evaluation of Frictional Characteristics of Labial and Lingual Self-ligating Brackets with Various Archwire Alloys

Background: An understanding of bracket slot–archwire interface is imperative for biomechanical effectiveness in orthodontic sliding mechanics and hence the aim of the study is to evaluate frictional properties of lingual self-ligating brackets comparing with conventional lingual and labial self-ligating brackets using three different archwire alloys in various environments. Materials and Methods: This in vitro study compared the frictional force of labial and lingual self-ligating and conventional lingual brackets with stainless steel, TMA, and Cr-Co alloy archwires of 0.017” × 0.025” dimension in dry and wet conditions. Frictional forces were evaluated in a simulated half arch fixed appliance using a testing machine. Static and kinetic friction were measured and analyzed by one-way analysis of variance (ANNOVA) test and post hoc Duncan multiple range test. The effects of brackets and archwires in dry and wet conditions were analyzed by three-way variance (ANNOVA) test. Result: The maximum frictional forces were observed with labial self-ligating brackets followed by lingual conventional brackets and the least by lingual self-ligating brackets. Of all the wires tested, TMA wires had the maximum frictional forces followed by Co-Cr and stainless steel. In both conditions, the values were non-significant with all bracket–wire combinations except with Co-Cr and TMA wires. Conclusions: Varied amount of frictional force was shown by the brackets and wires with highest by labial self-ligating bracket, followed by lingual conventional and lingual self-ligating brackets. TMA wires experienced higher friction followed by Co-Cr and stainless steel with minimum friction.

A novel and simple design of the closing loop producing optimal force magnitude and moment-to-force ratio for en-masse retraction of anterior teeth

ABSTRACT Purpose: The aim of this study was to clarify the mechanical conditions of loop activation that produce the optimal force system allowing controlled movement of the anterior teeth. Materials and Methods: The closing loop examined in this study was a 10-mm-high teardrop type bent from a 0.017 × 0.025-inch stainless steel archwire. A loop design that can generate a high moment-to-force (M/F) ratio and the optimal force magnitude was investigated by varying the rate of the cross-sectional reduction of the loop apex, the amount of loop activation and the degree of gable bend. Forces and moments acting on closing loops were calculated using structural analysis based on the tangent stiffness method. Results: A force magnitude of 302 g and an M/F ratio higher than 10 (sufficiently high to achieve bodily movement of the anterior teeth) could be produced when the thickness of the cross-section of a 10-mm-high teardrop loop was reduced by half for a distance of 3 mm from the apex and a gable bend of 30° was incorporated into the loop. Conclusions: The optimal force magnitude and M/F ratio for achieving controlled tipping or bodily movement of the anterior teeth can be produced by partially reducing the thickness of the teardrop loop, and by placing a gable bend of 20° to 30° in the 0.018-inch bracket slot system.

Comparative evaluation of square and rectangular slot three-point play behavior.

The play between bracket slots and archwires affects tooth movement and the transmission of orthodontic force by multi-bracket appliances. We assessed play by quantifying the play behavior of three-point brackets and comparing the amount of play that occurred with square and rectangular slots, respectively, by using archwires of various sizes. Horizontal play with the square slot was significantly smaller than that with the rectangular slot. These data demonstrate that brackets with square slots can more effectively bring about tooth movement in the labio-lingual direction and control rotational movement with round and square archwires. Since the horizontal and vertical play ratios for the round and square wires within the square slot were approximately 1.0, three-dimensional tooth movement may also be achieved with uniform play in the vertical and horizontal directions.

OPTIMUM FORCE SYSTEM FOR EN-MASSE RETRACTION OF SIX MAXILLARY ANTERIOR TEETH IN LABIAL ORTHODONTICS

The orthodontists generally do not recommend application of force system above the archwire level owing to additional attachments and patient’s discomfort. Hence, the present research study focusses on application of retraction force system at the archwire level. The objective of this study is to specify an optimum combination of archwire and bracket slot size for en-masse (simultaneous) parallel retraction of six maxillary anterior teeth in labial orthodontics (LaO). In this research study, the concept (theoretical) model has been developed based on simple principles of mechanics to estimate the torque generated by different sizes of archwire in bracket slots. Based on torque value, retraction force developed by each combination of archwire and slot size was determined and compared with required retraction force of 150 gram-force on each side of sagittal plane. For combination of [Formula: see text] inch stalinless steel SS archwire and 0.022 inch SS bracket slot, magnitude of computed retraction force matched closely with aforementioned required force than other combinations and hence, it is recommended in the present research study. The validation of selected combination of archwire and bracket slot size was done successfully by in vivo (clinical) experimentation on three patients. Thus, it proves that the aforementioned combination of archwire and bracket slot size is more suitable than others for retraction force system applied at archwire level.

Evaluation of Intrusive Forces Created by ‘V’ Bend, Intrusion Arches at Various Deflections: An Invitro Study

Aim: To evaluate of intrusive forces created by ‘v’ bend, intrusion arches at various deflections- an invitro study. Objective: The present study is to consider the importance of alloy used as intrusion arches. Material and Method: We used stainless steel wires, timolium wires, CNA Beta 3. Wires (Libral,USA), blue elgiloy all with rectangular section of dimension 0.017 x 0.025 inch, 15 numbers each. Arch forms are standardized with the help of arch form selector guide. Three distances from vestibule to bracket slot in upper anteriors were marked. Trials were conducted at the CIPET (Central Institute Of Plastic Engineering and Technology, Chennai) and a dynamometer (Autograph, U.K) with 1kgf load cell at 0.01kgf resolution and speed of 10mm/min7. The load magnitude at various displacements (5, 10, 15 mm) were recorded. Statistical Method: The significance level of 5% was taken. ANOVA was used for assessing the force of all the alloys and Tukey test was used for multiple comparisons. Results: The forces recorded at 5, 10, and 15 mm were all significant between the four alloys when compared except for CNA and timolium between 5 mm and 10 mm and for blue elgiloy between 10 mm and 15 mm were not statistically significant. Conclusion: The load increments tends to decrease from the first to last increment, and the differences is being more significant from the first increment to the second increment for all the alloys, and more significant in stainless steel and the blue elgiloy. CNA produced the least force.

Design of ultra-wide tetra band phased array inverted T-shaped patch antennas using DGS with beam-steering capabilities for 5G applications

AbstractA novel 1 × 4 phased array elliptical inverted T-shaped slotted sectored patch antenna with defected ground structure (DGS), resonate at proposed ultra-wide tetra band at 28, 43, 51, and 64 GHz with high gain and beam-steering capabilities is presented. An inverted T-shaped slotted stub is used with the sectored patch to achieve ultra-wideband properties. In order to resonate the antenna at four different bands, DGS of round bracket slot is etched on the ground. The 1 × 4 phased arrays are used at the top edge and bottom edge of mobile PCB with high gain. The simulation results show that the antenna has four ultra-wide bands: 25.8–29.7, 40.6–44.6, 49.2–53.1, and 62.2–74 GHz with a maximum gain of 16.5 dBi at 51 GHz. The phased array antenna is capable to steer its main beam within ±30° at the 26, 28, and 43 GHz, using appropriate phase shifts of each antenna element. The proposed millimeter wave antenna is particularly suitable for cellular infrastructures and can be a candidate for emerging 5G mobile applications. The availability of an additional 11.8 GHz (62.2–74 GHz) of contiguous unlicensed spectrum will allow the launching of new exciting wireless services.

Resistance to sliding of orthodontic archwires under increasing applied moments.

Orthodontic treatment with fixed appliances involves sliding of brackets along archwires. These movements involve friction, which causes resistance to sliding. In addition, moments cause teeth to tip until binding occurs between the bracket and archwire. The manufacturer of a new TiMolium®Titanium archwire claims material properties superior to β-Titanium, potentially leading to reduced resistance to sliding. To compare TiMolium archwires with β-Titanium and stainless steel archwires as the current gold standard for sliding mechanics under application of an increasing moment. A total of 120 stainless steel (Smartclip, 3M, Monrovia, CA) and ceramic self-ligating 0.022″-slot brackets (Clarity SL, 3M) were divided into six equal-sized groups. Resistance to sliding was tested with 0.019″ × 0.025″ TiMolium (TP Orthodontics, La Porte, IN), β-Titanium (3M), and stainless steel (3M) archwires using a custom-designed apparatus to simulate sliding mechanics and application of moments of 1000, 2000, and 3000 g-mm. Using stainless steel brackets, the TiMolium archwires had significantly higher resistance to sliding than stainless steel archwires at all moments tested while there was no difference between TiMolium and β-Titanium. Using ceramic brackets, the resistance to sliding with TiMolium archwires was no different than with stainless steel archwires. Both TiMolium and stainless steel archwires showed significantly lower resistance to sliding than β-Titanium. TiMolium archwires have resistance to sliding intermediary to stainless steel and β-Titanium archwires when clinically relevant moments are applied. Used with the stainless steel brackets, they behave like β-Titanium, whereas used with the ceramic brackets, they behave more like stainless steel.

Delaying Premolar Extraction for Conservation of Anchorage: A Prospective Case Control Study

Introduction: Anchor loss (AL) is the most common side effect of orthodontic treatment. Anchorage planning is the vital step of every orthodontic treatment. The aim of this study was to evaluate the amount of anchor loss of maxillary first permanent molar in early v/s delayed premolar extraction cases treated using fixed orthodontic mechanotherapy.
 Materials & Method: Sixty orthodontic patients, having either Class I or Class II Division 1 malocclusion with no or minimal crowding were divided equally into early extraction and the delayed extraction group (30 each). The patients were treated using MBT prescription 022” slot brackets with standard wire sequencing until 0.019”x 0.025” stainless-steel wire. Pre and post levelling study models were used for assessing the amount of space loss using palatal rugae as a stable point from the points marked on the 1st molar (point A on mesiobuccal cusp and point B on the distobuccal cusp). The obtained data was tabulated and was subjected to statistical t test (p<0.05).
 Result: The distance of point A to the 3rd rugae reduced after treatment by 0.39mm (3.4%) and by 0.48 mm (3.24%) in delayed and early extraction groups respectively. Similarly, the distance from point B was reduced by 0.48 mm (3.24%) and by 1.77mm (6.28%) in delayed and early extraction group respectively. The change in point A and point B in Early extraction cast group was 76% and 71% more respectively than the delayed Extraction cast group. All the findings were statistically significant (p<0.05).
 Conclusion: Anchor loss is an inevitable after effect following premolar extraction. Greater chances of anchor loss in early extraction group is noted. And delaying premolar extraction in cases with mild crowding (<4mm) can effectively help in anchorage preservation.

CLINICAL SIGNIFICANCE OF THE LEVELS OF THE GINGIVAL CREVICULAR FLUID VOLUME AND LEPTIN DURING ORTHODONTIC TOOTH MOVEMENT

It is assumed that leptin has a role in protecting gingival tissues, leptin stimulates the immune system and enhances bone formation by acting directly on osteoblasts. As periodontal disease progresses, the protective role of leptin on the gingiva is lost owing to a decrease in the leptin level. During orthodontic tooth movement, the early response of periodontal tissues to mechanical stress is an acute infammatory reaction. Study of leptin therefore is a useful guide to determine its relationship with tooth movement in both tension and pressure sites and the role of this cytokine in controlling the local infammation around the tooth. Detection of the leptin level in GCF at sites under orthodontic movement had been tested and it was found that the concentration of leptin in GCF is decreased by orthodontic tooth movement.
 The present study was planned in Department of Periodontology, Manipal College of Dental Sciences Manipal. Total 20 cases were evaluated in the present study. The 10 cases were enrolled in Group A as study cases and 10 cases were enrolled in control cases. The selected 10 patients were bonded with fixed appliance 0.022" PEA bracket slot, MBT prescription. The maxillary right canines (control tooth, CT) were not bonded with the bracket. The initial wire will be 0.016" NiTi wire. The distalisation force were applied on the left canine (test tooth, TT) using 0.010 SS lace backs.
 Significantly decreased levels of leptin concentration might result from the presence of inflammation adjacent to the teeth undergoing movement. It has been shown previously that orthodontic tooth movement may therefore show local traits of a damage/ repair process with inflammation-like reactions: high vascular activity, many leukocytes and macrophages, and involvement of the immune system.
 Keywords: Leptin levels, periodontal disease activity, orthodontic tooth movement, ininflammatory markers

Effect of Bracket Slot and Archwire Dimension on Posterior Tooth Movement in Sliding Mechanics: A Three-dimensional Finite Element Analysis.

IntroductionSpace closure by molar protraction has always been a challenge in orthodontic treatment due to larger root surface area which requires additional anchorage. Ideally, there should be little or no tipping. However, the protraction forces, being occlusal and buccal to the centre of resistance (CR) of the tooth, cause tipping and rotations.AimThe aim of the study was to assess the effect of bracket slot and archwire dimensions on posterior tooth movement during space closure in sliding mechanics and evaluate the length of power arm to bring about translatory movement of teeth using three-dimensional finite element analysis.Materials and methodsA model of the maxillary teeth was created and converted to a finite element format through a meshing software, Hypermesh. Two three-dimensional models, each with a combination of 0.017”× 0.022” archwire in 0.018” slot (model 1) and 0.019”×0.025” archwire in 0.022” slot (model 2), were generated. Power arms of different lengths were attached to the first molar. Miniscrew was inserted between the canine and first premolar.ResultsIn model one, the power arm of 10-mm height provided controlled tooth movement than the one with 6 mm height, and in model two, power arms of both 6-mm and 10-mm height produced controlled tooth movement.ConclusionsAs the force was raised apically from the slot, more translation was observed. Power arm of 6-mm height can be used due to anatomic limitation of the vestibule.

Deflection test on different orthodontic wire materials sized 0.016 x 0.022 inches

The development of technology in orthodontic field produces some orthodontic wires that have different deflection abilities. Loading force is the force needed to place an orthodontic wire in bracket slot (activation). Unloading force is the force produced by an orthodontic wire to move tooth (deactivation). Deflection test with three-point bending technique is a technique that is often used to determine the magnitude of the activation and deactivation force of orthodontic wire. Stainless steel (SS), nickel titanium (NiTi), copper nickel titanium (CuNiTi), and beta titanium (TMA), are the types of frequently used wires. This study aimed to compare loading and unloading force on the deflection test of SS, NiTi, CuNiTi, and TMA orthodontic wires sized 0.016 x 0.022 inch on the load-deflection graph. This is a laboratoryexperimental research on a total of 16 pieces of SS, NiTi, CuNiTi, and TMA orthodontic wires sized 0.016 x 0.022 inches. The group was divided based on the type of material. The deflection test was performed using a universal testing machine with a press speed of 5 mm/minute. Loading and unloading forces were recorded on deflections of 0.5; 1; and1.5 mm. Statistical tests of differences among groups were carried out by ANOVA analysis (p-value ≤ 0.05) and post-hoc analysis with T-test. There were significant differences in the loading and unloading forces recorded on deflections of 0.5; 1; and 1.5 mm; except for deflections of 0.5 mm of the SS and nickel-titanium wires. The wire deflection force fromthe lowest to the highest was CuNiTi wire, nickel-titanium wire, TMA wire, and stainless-steel wire.

Effect of Different Reconditioning Methods on Slot Dimensions, Bracket Base Thickness and Base Surface Area on Stainless Steel Brackets: An in vitro Study:

Aim and objective: This study evaluated the effects of cumulative reconditioning on standard stainless steel edgewise brackets of original slot dimensions of 0.022 × 0.028, bracket base thickness of 0.4 mm 2 and base surface area of 11.702 mm 2 . Materials and methods: The sample for this study consists of thirty new maxillary central incisor brackets. Brackets were divided into one control group (Group A, unrecycled) and two experimental groups (Groups B and C). Each group comprised of ten samples. Experimental groups were subjected to specific reconditioning methods (modified BigJane methods and Buchman methods) for three consecutive times, subsequent to which dimensional changes were measured and recorded. The bracket slot dimensions and bracket base thickness were measured by universal measuring microscope and base surface area by digital vernier caliper. Statistical analysis: The statistical analysis done were Kruskal- Wallis test (H), Wilcoxon rank test, Wilcoxon rank signed test. Results: There was change in the slot dimensions in both the reconditioning methods, but the Big-Jane method showed a greater increase in width as compared to the Buchman method. The changes in the slot depth, bracket base thickness and bracket base surface area in both the reconditioning methods showed clinically insignificant changes during first reconditioning. Conclusion: The result of this study shows that single reconditioning of bracket is advisable. Clinical significance: During first reconditioning of the bracket statistically significant changes do occurs in slot width but clinically least significance alteration occurs in other dimensions of the brackets so, there will be clinically insignificant play occurs, thus torque value will not change.

Evaluation of the basic surface roughness of an ISO-certified and non-ISO-certified slot bracket with an atomic force microscope

Introduction: The base surface roughness of slot bracket can affect friction in tooth movement. There are ISO-certified and non-ISO-certified stainless steel brackets on the market. Thus orthodontists must be careful in choosing the right bracket. This study was aimed to evaluate the differences of the surface roughness of ISO-certified and non-ISO-certified Roth 0.022 inch stainless steel bracket with the parameter of S a (average roughness). Methods: This research was a laboratory observational. Samples were taken randomly as many as 32 brackets divided into two groups, each consisted of two bracket brands. Surface roughness measurements were performed using an atomic force microscope (AFM), then the data were analysed by ANOVA test (p < 0.05) and Post-Hoc analysis. Results: The ISO-certified bracket has an S a value smaller than the non-ISO-certified bracket. There was a significant difference in the surface roughness of the ISO-certified and non-ISO-certified slot bracket base (p < 0.05). Conclusion: The ISO-certified bracket has a smoother base surface than the non-ISO-certified bracket base.Keywords: Surface roughness, stainless steel slot bracket, atomic force microscope

Variability of slot size in orthodontic brackets.

ObjectiveThe accuracy of the information incorporated into brackets is a determining factor for the efficacy of torque applied to teeth. The aim of this study was to compare the dimensions of a bracket's slots with the nominal values announced by the manufacturer.Materials and methodsA total of 730 maxillary right central brackets manufactured by seven companies (Dentsply Gac, American Orthodontics, Rocky Mountain Orthodontics, GC Orthodontics, 3M Unitek, and Dentaurum) were studied. The sample included 0.018 × 0.025 and 0.022 × 0.028 in., metal and ceramic, conventional and self‐ligating brackets. Images were obtained with an Olympus BX51 optical microscope. Slot dimensions were measured at the base and at the face on both mesial and distal sides using ImageJ software. Data were analyzed using Wilcoxon, sign tests, two‐ and three‐way ANOVA, and Tukey's tests. Intraclass correlation coefficient was employed to assess the intraobserver and interobserver variability. The threshold for statistical significance was p ≤ .05.ResultsStatistical analysis showed that the slot dimensions of 90% to 97% of studied brackets were significantly different from nominal values. In general, slot size was oversized, with a face size larger than the base size. Comparison between mesial and distal sides showed that up to 45% of the brackets were significantly asymmetrical. The manufacturer had a significant effect for base and face widths (p = .0001) and for length (p = .003).ConclusionThis study shows that a large proportion of measured brackets displays dimensional inaccuracies when compared with stated values. Clinically, the slot oversize and the divergence of slot walls cause an increase of wire‐slot play, inducing a loss of torque control. Practitioners cannot fully trust the precision of used appliances and should be aware that adjustments could be needed in the finishing stages of the treatment.

Biomechanical analysis for total mesialization of the mandibular dentition: A finite element study.

To clarify the mechanics of tooth movement in mesialization of the whole mandibular dentition when changing the force angulation. A finite element method was used to simulate long-term movements of the whole mandibular dentition. Tooth movement was simulated by accumulating the initial displacement, which was produced by elastic deformation of the periodontal ligament. Mesial forces of 3N were applied to the second molar bracket at -30°, -15°, 0°, 15° and 30° to the occlusal plane. The whole dentition and occlusal plane were rotated depending on the direction of the force with respect to the centre of resistance (CR). At a force angulation of -30°, the line of action of the force passed near the CR, and the whole dentition translated without rotation of the occlusal plane. The second molar tipped buccally due to a clearance gap between the archwire and bracket slot. When increasing a force angulation from -30°, the line of action of the force passed above the CR, and thereby, the occlusal plane rotated clockwise. This rotation of the whole dentition induced tipping of the individual teeth. Buccal tipping of the molar due to an elastic deformation of the archwire was prevented by using a lingually pre-bent archwire. Careful selection of force angulation and biomechanics is essential to obtain proper tooth movement in total mesialization of the mandibular dentition.

Variation in bracket slot sizes, ligation methods and prescriptions: UK national survey

This study designed to investigate the use of fixed bracket slot sizes, ligation method and prescriptions in the UK using an online survey/questionnaire comprised of seven questions. The questionnaire link along with an explanation of its nature was circulated via the British Orthodontic Society (BOS) to all 978-email addresses of the Consultant Orthodontists Group (COG) and Orthodontic Specialists Group (OSG) (registered on the UK Specialist List for Orthodontics) members inviting them to participate. Two email reminders were sent to increase the response rate. Chi2 analyses determined the statistical differences in the use of bracket slots and prescriptions according to the regions and years of experience. The respondents represented 31.2% of the BOS specialist orthodontic members. Most of the respondents practised in the South of England with experience between 11-30years. The vast majority of the respondents routinely used brackets with the multibracket appliance treatment (MBT) prescription (81.6%) and 0.022-inch slot size (98.7%), which was statistically significantly higher in all geographical regions and experience levels (P<0.001). The majority of the respondents reported either 100% or 90% use of conventional brackets when compared to self-ligating brackets. The vast majority of UK specialist orthodontists use conventional ligating MBT prescription brackets with the 0.022-inch slot size. This was mainly because they perceive that this combination provides better treatment outcomes, whilst many respondents also indicated that they were taught and trained using this combination and that there was not enough evidence to support a change in their clinical practice.

Evaluation and comparison of bracket slot dimensions in lingual bracket systems: An in vitro study

ABSTRACT Background The aim of this study was to evaluate bracket slot width and slot depth and to compare and assess the variation between reported and actual slot dimensions of various commercially available lingual brackets. Materials and Methods The study comprised 60 new lingual upper right central incisor brackets from four different manufacturers. Brackets were segregated into four groups composed of 15 brackets: Group A, Ormco STb Lingual Brackets; Group B, Leone Lingual Brackets; Group C, Dentaurum Lingual Brackets; Group D, Dentos Org. Lingual Brackets. Each bracket was individually mounted on a slide using modeling clay. The bracket slot was oriented vertically on the slide so that the line of view of the confocal microscope was parallel to the slot axis. Slot dimensions were measured from the LEXT software of the confocal microscope. Results Slot dimensions were not as mentioned by manufacturers. Slots were either undersized or oversized. Conclusions Actual slot size and shape of commercially available brackets are larger or smaller from the actual prescribed value within a bracket series. Slot geometry and the standard of bracket finish varies between the brackets of different groups. Clinicians should be aware that there may be a three-dimensional loss of tooth positioning as a result of the inadvertent use of orthodontic brackets with oversized slots prolonging treatment duration and the need of additional wire bending to overcome the inadequacies of the brackets so as to achieve a good finishing.