Bracket Slot Research Articles

Effect of different liquids on APC flash-free ceramic bracket’s color stability, shear bond strength, and slot surface roughness

Abstract Objective: The aim of this in vitro study was to evaluate the effect of thermal aging and five different discolouring solutions on the shear bond strength (SBS), discoloration, and slot surface roughness (SSR) of Flash-Free ceramic brackets. Methods: A total of 70 human premolar teeth were randomly divided into seven groups: group 1: no procedure was performed; group 2: Only thermal cycling (TC); group 3: TC + immersion in cherry juice for 72 hr; group 4: TC + immersion in coffee for 72 hr; Group 5: TC + immersion in Coke for 72 hr; group 6: TC + immersion in artificial gastric acid for 24 hr; group 7: TC + immersion in artificial saliva for 72 hr. SBS values were determined by using a universal testing machine. The discolouration was evaluated using a Vita Easy Shade spectrophotometer which is based on the International Commission on Illumination system (CIE Lab colour system). A 3D optical profilometer was used to measure the roughness of the bracket slot bases. Results: Coke, coffee, cherry juice, and gastric acid all significantly increased slot surface roughness. There was, however, no statistically significant difference in the roughness caused by these liquids. The lowest SBS value was observed in the gastric acid group. Gastric acid and Coke were observed to induce the largest colour change. Conclusions: Thermal aging and different liquids cause discolouration and increased surface roughness on APC flash-free brackets. The adhesive bond strength was clinically acceptable even after immersion in gastric acid.

Loads of continuous mechanics for uprighting the second molar on the second molar and premolar

This paper aims to evaluate the effect of tube height on uprighting a mandibular second molar with a continuous arch, specifically the main effects on the molar tube and the side effects on the second premolar bracket. Slot brackets (0.18-in) and tubes were passively bonded from the left second molar to the right second premolar of the patient's cast and fixed to an orthodontic force tester. A mesially tipped second molar along with its tube was positioned at 5 different heights in relation to the bracket slots of the remaining appliance: 2 mm below (group -2), 1 mm below (group -1), leveled (group 0), 1 mm above (group 1) and 2 mm above (group 2). Each group had 10 different 0.016 × 0.022-in superelastic nickel-titanium wires tied one at a time to the appliance to register the vertical forces (Fz) and tipping moments (Mx) produced at the molar tube and the premolar bracket, statistically. Analysis of variance was used to identify differences of load among the groups for wire response to the position of the tube in relation to the other brackets' slots. As the molar tube was positioned more occlusally, Fz and Mx decreased at the molar tube from 1.31 N to 0.75 N and 13.98 N.mm to 11.84 N.mm, respectively, whereas at the premolar bracket, Fz and Mx decreased from 1.52 N to 0.88 N and 8.77 N.mm to 1.05 N.mm, respectively. In all groups, the load system at the molar tube (the main effects) registered a distal tipping moment and an extrusive force, whereas at the premolar bracket, the load system (side effects) included a distal tipping moment and an intrusive force. As the tube moved occlusally, the extrusive force and the uprighting moment decreased, along with the side effects at the premolar bracket. Attempting to bond the molar tube more occlusally (within reasonable intraoral dimensions) when trying to upright a molar does not appear to be sufficient to keep a molar from extruding.

Tip and Torque Accuracy According to the ISO 27020:2019 Norm in Currently Available Pre-Adjusted Orthodontic Brackets

Background: The precision of bracket manufacturing is fundamental to ensure the correct expression of the inbuilt information. The objective of this study was to determine the actual tip and torque values of a pool of stainless steel brackets, pre-adjusted according to the MBT prescription values, and to compare these actual values with those stated by the manufacturers in order to test their compliance with the tolerance limits reported in the ISO 27020:2019. Methods: A sample of 360 stainless steel brackets, from 12 different providers, were evaluated. All brackets had a nominal slot size of 0.022 in., belonged to the upper right central incisor, and were manufactured with the metal injection molding technique (MIM). For each provider, three different batches of the same bracket series were tested. A single-blind design was used for bracket coding. Results: Only five systems displayed torque mean values that matched the declared values (p > 0.05). Only one system did not respect the tolerance limits established in the ISO 27020:2019 norm. The tip values were different from those declared in seven of the assessed systems; however, none exceeded the tolerance limits. The inter-batch variability in most cases was not statistically significant. Conclusions: In most of the assessed systems, there can be a difference between the actual and the declared torque values, while tip information is usually accurately incorporated into the bracket slot. Lack of precision in the manufacturing process can reduce the efficacy of the appliance and force the clinician to compensate for dimensional inaccuracy through wire bending.

Friction and archwire engagement in contemporary self-ligating appliance systems : An in vitro comparison.

The aim of this study was to compare classical friction (FR) in passive self-ligating brackets (P-SLBs), active self-ligating brackets (A-SLBs) and atraditional twin bracket, in vitro, and to identify the point of initiation of bracket-archwire engagement. Nine bracket systems of 0.022 in slot size were FR tested: 5 P‑SLB systems; 4 A‑SLB systems; and a control group of twin brackets with elastomeric ligatures. Single upper right central incisor brackets were mounted on acustom metal fixture for testing. Straight sections of various round and rectangular nickel-titanium (NiTi) archwires (0.016, 0.018, 0.018 × 0.018, 0.020 × 0.020, 0.016 × 0.022, 0.017 × 0.025, 0.019 × 0.025, and 0.021 × 0.025 in) were ligated to the bracket and peak static FR (cN) was measured with an Instron Universal Testing Machine. Ten unique tests each utilizing anew bracket and new archwire were conducted for each group in the dry state. FR was significantly different between control, P‑SLB and A‑SLB systems (P < 0.001). P‑SLB groups displayed no significant differences in FR between each other, regardless of archwire size. A‑SLB groups did exhibit significant differences in FR between each other depending on both the bracket system and archwire size. Each A‑SLB system tested possessed adistinctly different pattern of initiation of bracket-archwire engagement. FR between the archwire and bracket slot differs between P‑SLB and A‑SLB systems, with adistinct pattern of FR and bracket-archwire engagement for each A‑SLB system. Understanding the different bracket-wire interactions of SLB systems should help orthodontic clinicians to plan effective and efficient biomechanics with the bracket system of their choice.

Self ligating brackets: from past to present

Self-ligating brackets, as the name suggests, do not use any steel ligature wires or elastic ligature modules in holding the archwires into the bracket slots. Rather they have their own mechanics of holding the archwire, either by a clip already in the bracket or a sliding lock mechanic in the bracket. These brackets can be active or passive depending on how the wire is engaged in between the slot and the self-ligating mechanism. In this review article, various systems of self-ligating brackets have been shown as they have been introduced from the past since their introduction in the early 1930s to the present.

Canine angulation and rotation during canine retraction using elastomeric chains with and without a power arm

Background: During canine retraction, orthodontic forces are applied away from the tooth’s center of resistance. This introduces canine distal tipping and mesiobuccal rotation. The correction of these unwanted movements will prolong treatment time. Applying the force closer to the center of resistance should decrease this unwanted tooth movement. Objective: Compare the canine angulation and rotation during canine retraction with and without the use of power arm. Materials and Methods: Twenty-four female orthodontic patients (age 19.32± 4.17 years) with dental Class II indicated for bilateral maxillary first premolar extraction and maximum anchorage were included in this study. The canines were retracted with elastomeric chains over 0.016” X 0.022” statinless steel arch wires to reduce friction. The retraction force was 150g. In twelve patients, the canines were retracted using a power arm fixed to the vertical slots of the canine brackets. For the other twelve patients, the elastic chains were attached to the bracket hooks. Results: Before treatment, the canine angulation and rotation was similar for the two groups. The canine angulation was 12.38± 8.27 and 14.5o± 9.41 for the group with the power arm and without, respectively. while canine rotation was 64.74o± 11.65 and 63.12o± 14.88, respectively. Post-retraction, there was no significant difference in the canine angulation or rotation between the groups. Conclusion: Compared to canine retraction with a power arm, conventional canine retraction with elastomeric chains attached to the bracket hook may provide similar control over distal tipping, provided a stiff 0.017” X 0.025” stainless steel arch wire is used.

Identification of Bone Density Changes Applying Impedance Spectroscopy with a Piezo-Device Coupled to a Human Tooth

Bone tissue is a calcium deposit and supporting structure of the human body, it is exposed to several pathologies that modify its mineral content. To determine these changes, different diagnostic procedures are performed with techniques using invasive ionizing radiation, which are limited by the negative effects in the long term on human health. A methodology is explored that could be applicable in the diagnosis of pathologic variations in bone mineral density, using structural monitoring tools. The proposed technique estimates changes in bone conditions by applying impedance spectroscopy with a tooth-borne piezo-device. Bone-tooth samples were prepared to simulate a section of maxillary bone and subsequently treated with chemical agents, simulating pathologic decalcification. The piezo-device is inserted in the slot of an orthodontic bracket, previously bonded to the crown of the tooth, in order to transmit vibration to surrounding bone. The variations in bone micro-architecture were computed by image processing analyzed with samples prepared in transparent resin, allowing the measurement of morphometry before and after the induced changes in mineral content. Using vibrational bone response, impedance measurements allowed to observe the variations in bone mass as the samples were progressively decalcified. In the 5-50kHz spectrum, it was demonstrated the sensitivity of the electro-mechanical impedance during the bone alteration procedure since the electrical resistance signals of the piezo-device consistently changed in the frequency spectrum (5-50kHz). The piezo-device shows to be sensitive to the changes produced by the bone alterations, which were caused by the stiffness variations made in the sample during the decalcifying. These changes were statistically correlated to demonstrate that in a less invasive way, bone alterations could be monitored from the teeth. This result opens the door to search for a new way to diagnose bone density changes in real applications.

Frictional Forces of Three Types of Lingual Appliance with Self-ligating Mechanisms

The present study compared the frictional forces of three types of self-ligating lingual appliances. The lingual appliances (2D, Forestadent; Alias, Ormco; and Clippy L, Tomy International) consisted of a self-ligating bracket (second premolar) and two self-ligating tubes (first and second molars) bonded to a stainless steel jig and attached to a "drawing-friction tester." Full-size and non-full-size stainless steel archwires were tested, and the static and kinetic friction acting on six lingual appliance/wire combinations was estimated (n = 5). Three-dimensional micro-computed tomography (micro-CT) analysis of each premolar bracket was performed. The frictional forces were compared between the bracket/wire combinations using the Kruskal-Wallis and Mann-Whitney U tests. The Alias and Clippy L bracket/wire combinations had greater contact between the wire surfaces and bracket slots compared to the 2D bracket/wire combination. For all lingual appliances, the static and kinetic frictional forces were significantly higher for the full-size than non-full-size archwire. The 2D bracket, which had a wider outer wing, had less frictional force than the other appliances. The Alias, which had a narrower outer wing, had a significantly lower frictional force than the Clippy L. Frictional force was significantly higher for heavier full-size bracket/archwire combinations than for non-full-size archwires. The 2D bracket had lower frictional force due to its archwire-holding mechanism. The outer wing width may influence the frictional resistance. The frictional forces of self-ligating lingual appliances vary, and bracket design and archwire size may influence the frictional performance.

Biomechanical analysis for total distalization of the maxillary dentition: A finite element study

This study aimed to identify the tooth movement patterns relative to various force angulations (FAs) when distalizing the total maxillary dentition. Long-term orthodontic movement of the maxillary dentition was simulated by accumulating the initial displacement of teeth produced by elastic deflection of the periodontal ligament using a finite element analysis. Distalization forces of 3N were applied to the archwire between the maxillary canine and first premolar at 5 different FAs (-30°, -15°, 0°, 15°, and 30°) to the occlusal plane. Maxillary incisors and molars showed lingual and distal tipping at all FAs, respectively. At a force angulation of 30°, almost bodily distalization of the total maxillary dentition occurred, but incisors showed considerable lingual tipping because of the effect of clearance gap (0.003-in, 0.022×0.025-in bracket slot, 0.019×0.025-in archwire) and elastic deflection of the archwire. Medial displacement of the maxillary anterior teeth occurred because of lingual tipping during distalization. The occlusal plane rotated clockwise at all FAs because of extrusion of the maxillary incisors and intrusion of the maxillary secondmolars, and the amounts decreased as FA increased. Tooth movement patterns during distalization of the total maxillary dentition were recognized. With an understanding of the mechanics, a proper treatment plan can be established.

Evaluation of antimicrobial potential and surface morphology in thin films of titanium nitride and calcium phosphate on orthodontic brackets

The goal of this research was to experimentally evaluate the surface morphology and adhesion capacity of Streptococcus mutans (U159) on brackets with thin films of titanium nitride (TN) and of titanium nitride doped with calcium phosphate (TNCP). Twenty-four metallic brackets were equally allocated to 3 groups (n=8), according to the type of covering (no covering, TNCP, and TN). The coatings were deposited by cathodic cage (TNCP and TN groups) and were evaluated by scanning electron microscopy and energy dispersive x-ray spectrometry. The biofilm formation of S. mutans on the surface of brackets was determined by crystal violet assay and subsequent optical density quantification. There was homogeneity on the surface morphology of the tie wing area in all groups, whereas the TNCP group has presented particles in the slot. After 24hours, a biofilm of S. mutans was formed in all the observed groups. The optical density obtained in all 3 groups was similar (no covering, 0.347±0.042; TNCP, 0.238±0.055; TN, 0.226±0.057), with no statistically relevant difference (P=0.06). The thin film of TNCP has altered the surface of the bracket's slot, whereas the coatings of TN and TNCP have not altered the superficial morphology of the tie wings. The presence of coatings have not influenced the formation of the S. mutans biofilm on the surface of metallic brackets.

Experimental evaluation of orthodontic bracket slot deformation to simulated torque.

In orthodontic fixed appliance therapy, the archwire torque used to refine the teeth position during the treatment imparts significant forces inside the bracket slot. The objective of this study was to measure the torque relevant bracket slot deformation in Stainless Steel (SS) brackets during various degree of archwire twist. Standard edgewise brackets 0.018-inch (in.)/0.022-in. each 20 no. and 0.016 × 0.022, 0.017 × 0.025, 0.019 × 0.025, and 0.021 × 0.025 in. archwires each 10 no. were used. A novel experimental setup consisting of loading fixture and torque key mounted on a Vision Measuring System (VMS) were used to measure the brackets slot deformation. The Top Slot and Middle Slot Deformations (TSD and MSD) of the brackets for 35° angle of twist in 0.016 × 0.022 in. archwire in 0.018-in. slot, 0.019 × 0.025 in. archwire in 0.022-in. slot and for 30° angle of twist in 0.017 × 0.025 in. archwire in 0.018-in. slot and 0.021 × 0.025 in. archwire in 0.022-in. slot were measured. Results showed that the mean TSD and MSD were higher when the archwire size, the slot size and the angle of twist were greater. In the evaluated bracket-archwire combinations, the TSD were higher than MSD and the bracket slots were elastically deformed within the clinically required 35° angle of twist in the archwire. Clinicians should be aware of this torque relevant bracket slot deformation which might be a factor for torque loss and suitably incorporate archwire angle of twist.

Assessment on the Precision of the Orthodontic Bracket Slot Dimensions Using Micro-computed Tomography (Micro-CT)

To evaluate the precision of the orthodontic bracket slot dimensions of 0.022 inch and to compare them with those of the manufacturers' specifications. The slots of upper-right central incisor brackets (n = 5) from 11 commercial bracket systems of three different manufacturers (3M Unitek: Victory Mini Metal, Clarity, SmartClip, Clarity SL; ORMCO/SYBRON: Mini Diamond Twin, Damon Q, Damon Clear; Dentsply/GAC: Ovation, Mystique, In-Ovation R, In-Ovation C) were measured. The orthodontic brackets were scanned using micro-computed tomography (micro-CT), and the bracket slots were measured using micro-CT images. The slot was measured at four different surfaces (occlusal, gingival, base, and face) for both mesial and distal sites. Data were subjected to ANOVA and unpaired t-tests. A p-value of ≤0.05 was considered statistically significant. All brackets had slot dimensions that were significantly larger (p < 0.05) than the stated 0.022 inch. 3M-victory were 11.99% larger (0.02509 inch) and the closest to the stated dimension and the ORM-Damon C were 24.07% larger (0.02948 inch) than the quoted slot size of 0.022 inch. Comparison between mesial and distal sides showed that 91% of the bracket slots were asymmetrical at their bases and 100% asymmetrical at their faces. All of the bracket system showed divergent walls from base to face with values ranging from 1.96 (3M-SmartClip) to 26.58% (ORM-Damon C). The actual measurements of 11 bracket systems from three different manufacturers were more substantial than the manufacturers' specifications, and the walls of the slots diverged from the bracket bases in all of the tested bracket system. Orthodontic bracket slots vary significantly from that of the manufacturers' specification. The orthodontist should anticipate such shortcomings and be able to modify treatment mechanics through additional wire bending in three spatial planes.

Various bidimensional techniques used in orthodontics: A systematic review

Maintaining torque with sliding mechanics in maxillary anterior teeth especially in presence of large extraction spaces has become a major concern among orthodontist. Loss of torque occurs owing to play between bracket system and arch wires. Thus, for torque control various arch wire twisting and torquing axillaries have been introduced. Not only do these techniques cause certain discomfort to patients but also extends patient chair time because of various chair side wire bending involved. Thus, a bidimensional technique in bracket system will be beneficial in controlling incisor torque simultaneously it will also assist in loss of anchorage in posterior teeth as it facilitates free sliding of arch wire through the bracket slot thus reducing friction. The aim of this article is to equip an overview of bidimensional technique in orthodontics. Keywords: Bimetric system.

Effects of Diode and Nd:YAG Laser Irradiation on Friction Forces Between Two Types of Ceramic Brackets and Rhodium-Coated Archwires.

Introduction: Ceramic brackets have gained increasing popularity among dental clinicians and orthodontic patients but friction is a major concern when using them. This study sought to assess the effects of diode and Nd:YAG (neodymium-doped yttrium aluminum garnet) laser irradiation on friction forces between two types of ceramic brackets and rhodium-coated esthetic archwires. Methods: Thirty polycrystalline and 30 poly-sapphire brackets were divided into 6 groups (n=10) as follows: (I) control polycrystalline brackets (no laser irradiation), (II) polycrystalline brackets subjected to diode laser irradiation, (III) polycrystalline brackets subjected to Nd:YAG laser irradiation, (IV) control poly-sapphire brackets (no laser irradiation), (V) poly-sapphire brackets subjected to diode laser irradiation, and (VI) poly-sapphire brackets subjected to Nd:YAG laser irradiation. The bracket slots were laser-irradiated on a custom-made table. Sixty 5-cm pieces of rhodium-coated archwires were used for the friction test in a universal testing machine at a speed of 10 mm/min. Ten brackets from the six groups underwent scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). Results: The frictional resistance value of polycrystalline brackets was significantly higher than that of poly-sapphire brackets, irrespective of laser type (P <0.05). Irradiation of diode and Nd:YAG lasers, compared with the control group, had no significant effect on friction, irrespective of bracket type (P >0.05). Conclusion: It appears that diode and Nd:YAG laser irradiation cannot significantly decrease the friction. Future studies are warranted on different laser types with variable exposure.

Scanning Accuracy of Bracket Features and Slot Base Angle in Different Bracket Materials by Four Intraoral Scanners: An In Vitro Study.

The accurate expression of bracket prescription is important for successful orthodontic treatment. The aim of this study was to evaluate the accuracy of digital scan images of brackets produced by four intraoral scanners (IOSs) when scanning the surface of the dental model attached with different bracket materials. Brackets made from stainless steel, polycrystalline alumina, composite, and composite/stainless steel slot were considered, which have been scanned from four different IOSs (Primescan, Trios, CS3600, and i500). SEM images were used as references. Each bracket axis was set in the reference scan image, and the axis was set identically by superimposing with the IOS image, and then only the brackets were divided and analyzed. One-way analysis of variance (ANOVA) was used to compare the differences. The difference between the manufacturer’s nominal torque and bracket slot base angle was 0.39 in SEM, 1.96 in Primescan, 2.04 in Trios, and 5.21 in CS3600 (p < 0.001). The parallelism, which is the difference between the upper and lower angles of the slot wall, was 0.48 in SEM, 7.00 in Primescan, 5.52 in Trios, 6.34 in CS3600, and 23.74 in i500 (p < 0.001). This study evaluated the accuracy of the bracket only, and it must be admitted that there is some error in recognizing slots through scanning in general.

A Comparative Analysis of Force Deflection Property of Nickel-Titanium Wires of Four Manufacturers using Five Point Bending Test: An In-vitro Study

Introduction: Over the last century, material science has made rapid progress. In orthodontics, not only the materials improved, but also the philosophies have changed. Orthodontic wires, which generate biomechanical forces through brackets for tooth movement, are central to the practice of this profession. Aim: To measure the force deflection properties of Nickel-Titanium (NiTi) wires of four manufacturers, used during orthodontic treatment. Materials and Methods: In this in-vitro study, 480 NiTi wires from four different manufacturers [American Orthodontics (AO), 3M-Unitek (3M), Rabbit Force Orthodontics (RO) and Modern Orthodontics (MO)], of various cross-sections was obtained. Samples of each wire were obtained by cutting the straightest distal portion of an arch wire, thus an approximate length of 5.5 cms was recovered. These wires were subjected to a five point bending test. Five lower anterior stainless steel brackets of tooth number 31, 32, 41, 42 (MBT 0.022” Libral traders Centrino brackets) were fixed with the face of the bracket facing upwards on the acrylic block. Each NiTi wire was placed in the slots of orthodontic brackets and secured with stainless steel ligature wires. These wires were subjected to artificial saliva (Wet Mouth) for 30 days at 37°C. This temperature was regulated by using an incubator. The main assessment criterion was the force deflection property of the wire material. Force deflection was measured using a graph paper where initially the wire was placed and plotted on the graph paper. After the deflection of the wire, it was again placed on the same graph paper such that wire ends coincided and the force deflection at the highest point was measured in millimetres using a digital Vernier Caliper (Mitutoyu). The Design of Experiments (DOE) model was used for analysis and a three-way Analysis of Variance (ANOVA) with wire shape as covariate was used for analysing the variability. Results: A 0.014” NiTi wire showed more mean deflection when compared to 0.016” NiTi wire. When a comparison between 0.016”×0.022” and 0.017”×0.025” NiTi wires was done, mean deflection was almost the same. When round and rectangular wires were compared it showed more mean deflection in round wires. When AO was compared with other three manufacturers. A significant difference (p-value &lt;0.0001) was seen in the mean deflection values of MO and RO. When 3M was compared with the other three manufacturers a significant difference (p-value &lt;0.0001) was seen in the mean deflection values of MO and RO. Three-way ANOVA test with wire shape as co-variate showed a significant amount of difference (p&lt;0.0001) for AO, 3M wires with their counterparts. Conclusion: Round NiTi wires showed more force deflection as compared to rectangular NiTi wires. AO and 3M wires were superior as compared to RO and MO wires. Superelastic wires showed more deflection as compared to conventional and heat- activated NiTi. This can be attributed to the property of the wire. Stiffer the wire, less deflection was seen. Cost of the wire also played a role. Cheaper wires were not able to match the quality and standards of their counterparts.

Biomechanical implications of rotation correction in orthodontics: Case series

According to Bacetti (1998) tooth rotation is defined as observable mesiolingual or distolingual intra-alveolar displacement of the tooth around its longitudinal axis.1 Tooth rotations cause difficulty in finishing fixed orthodontic treatment. In Begg’s technique rotation springs are used to correct tooth rotations. These springs are engaged into the vertical slot of the bracket. In case of preadjusted edgewise technique and edgewise technique brackets doesn’t have a vertical slot. So alternative methods are used to correct tooth rotations.2 Various methods include engaging NiTi arch wire into the bracket slot, off centering the bracket, using rotation wedges, creating a couple on the rotated tooth, by using ligature ties.3 The purpose of this case series is to discuss the biomechanics involved in rotation correction using bracket offsetting and couple. Keywords: Couple, Bracket offsetting.

Surface Roughness on the Slots and Wings of Various Ceramic Self-Ligating Brackets and their Potential Concern on Biofilm Formation.

The surface roughness of various orthodontic materials could affect biofilm formation and friction. The purpose of this study was to examine the surface roughness and chemical composition of the slots and wings of several ceramic self-ligating brackets. Four types of ceramic self-ligating brackets were separated into experimental groups (DC, EC, IC, and QK) while a metal self-ligating bracket (EM) was used as the control group. Atomic force microscopy and energy-dispersive x-ray spectroscope were used to examine the surface roughness and chemical composition of each bracket slot and wing. The control group was made of ferrum and chrome while all the experimental groups were comprised of aluminum and oxide. There was a statistically significant difference in the roughness average (Sa) among the various self-ligating brackets (p< 0.001 in slots and p<0.01 in the wing). The slots in the EC group had the lowest Sa, followed by the DC, IC, control, and QK groups. The wings in the IC group had the lowest Sa, followed by the EC, DC, control, and QK groups. There is a significant difference in the surface roughness of the slots and wings among several types of ceramic self-ligating brackets.

Comparison of slot sizes and parallelism of metal brackets manufactured through metal injection molding and computerized numerical control.

ObjectiveTo investigate and compare the slot sizes and parallelism of metal injection molding (MIM) and computerized numerical control (CNC) brackets.MethodsThe following four MIM bracket series with 0.022-inch (in) slots were selected for investigation Di MIM mini Twin (Ortho Organizers), Mini Diamond Roth (Ormco), Gemini MBT (3M Unitek), and Formula R Roth (Tomy). The following four CNC bracket series with 0.022-in slots were selected for investigation Econoline MBT (Adenta), Legend mini MBT (GC Orthodontics), Crown mini MBT (Adenta), and Evolve MBT (DB Orthodontics). The slot dimensions were measured using an optical microscope (XTCam-D310M; Mitutoyo) with a resolution of 1 μm. The results were statistically analyzed using one-way analysis of variance and the Tukey post-hoc test with a significance level of 0.05.ResultsThe results indicated that all the investigated slot sizes were oversized with respect to the manufacturers’ specifications (0.022 in). Among the eight bracket series, the Di MIM bracket (MIM) was the most oversized by 10.4%, whereas the Evolve bracket (CNC) was the least oversized by 2.6%. The slots in seven of the bracket series had divergent walls instead of parallel ones. The Evolve bracket alone had parallel slot walls.ConclusionsRegardless of the manufacturing method, all the slot sizes of the brackets investigated in this study were significantly oversized; most of the slot walls were nonparallel, except for those of the Evolve bracket. This study could not establish that the CNC method was more accurate than the MIM method in manufacturing bracket slots.

A Prospective Randomized Clinical Trial to Evaluate the Slot Size on Pain and Oral Health-Related Quality of Life (OHRQoL) in Orthodontics during the First Month of Treatment with Conventional and Low-Friction Brackets

The aim of this research project was to analyze the influence of slot size and low-friction on pain and the oral health-related quality of life (OHRQoL) of subjects receiving fixed appliances. A group of 120 patients (61 male, 59 female) were chosen for this randomized clinical trial. Participants were classified into four groups (30 patients in each). We compared conventional (C group) and low-friction (LF group) brackets and 0.018″ and 0.022″ slots. Pain was assessed at 4 (T0), 8 (T1), and 24 (T2) hours, and 2 (T3), 3 (T4), 4 (T5), 5 (T6), 6 (T7), and 7 (T8) days after the start of treatment by using the visual analogue scale (VAS). OHRQoL was assessed at 1 month using the Oral Health Impact Profile (OHIP-14). Data was analyzed using the analysis of variance (ANOVA) test with post-hoc Bonferroni correction. For pain on the visual analogue scale, statistically significant differences (p &lt; 0.05) were found for T0 and T3. For OHRQoL, statistically significant differences (p &lt; 0.01) were found in the domains of physical pain, psychological discomfort, psychological disability, and overall OHIP. The group with 0.022″ low-friction brackets showed a lower pain score and less impact on OHRQoL. The type of bracket system used and bracket slot size influenced patients’ perceptions of pain and their OHRQoL.