The influence of bracket design on frictional losses in the bracket/arch wire system

The minimal important difference in orthodontic treatment duration: a survey across adult patients

BACKGROUND

The minimal important difference (MID) is defined as the smallest difference that the patient perceives as important. Furthermore, the smallest worthwhile effect (SWE) is the important change measured with the benefit-harm trade-off method. The aim of this study was to evaluate the MID in orthodontic treatment duration to inform the decision regarding seeking procedures to accelerate orthodontic tooth movement and reduce treatment duration.

METHODS

We constructed a survey eliciting views of the MID from adult participants from four countries undergoing orthodontic treatment. Ten questions addressed reduction in the treatment duration for both durations 12 and 24 months, and four questions were related to the reduction in treatment duration that the patients would require to undergo surgical or non-surgical adjunctive procedures. We applied a univariable random effects logistic regression model to examine the association between the participants' characteristics and the MID. Then, we fitted a multivariable logistic random effects regression including significant predictors.

RESULTS

Four hundred and fifty adults, with a median age of 21 (interquartile range: 19-24), undergoing orthodontic treatment participated in the survey. Of the respondents, 60% considered 15 days as a trivial reduction from 12 months duration of therapy and 70% considered 15 days a trivial reduction from 24 months. Of the respondents, 48% considered the period of 2 months a moderate reduction from 12 months, and 60% considered 2 months a moderate reduction from 24 months. From these results, we inferred that patients considered reductions of approximately 1 month as the MID in the treatment duration for both 12 and 24 months. However, SWE was considerably more than the MID for most of the participants to decide undergoing surgical adjunctive procedures to reduce the time of therapy. The participants required smaller SWE to undergo non-surgical procedures compared to surgical procedures.

CONCLUSION

The MID in the treatment duration is one month for both treatment durations 12 and 24 months. Patients require a greater SWE than the MID to undergo adjunctive procedures to shorten the duration, particularly for surgical procedures.

Comparative assessment of frictional forces between differently designed esthetic brackets during simulated canine retraction

OBJECTIVES

To evaluate force loss due to friction (FR) with an emphasis on esthetic brackets and their design differences during simulated canine retraction.

MATERIALS AND METHODS

The tested brackets were round and sharp-cornered conventional-ligating brackets and round-cornered self-ligating brackets. The tested archwires were stainless steel (0.018 × 0.025″ and 0.019 × 0.025″, and 0.018″) archwires. A total of 90 bracket-archwire combinations in 9 equally-sized groups (n = 10) were analyzed. Canine retraction was experimentally simulated in a biomechanical set-up utilizing the custom-made orthodontic measurement and simulation system (OMSS) using a NiTi coil spring that delivered a constant force of 1 N. The simulated retraction path was up to 4 mm. FR was compared among groups using the Welch t‑test. Significance level (α) was set to 0.05.

RESULTS

The round-cornered conventional-ligating bracket exhibited the least FR (28.6 ± 5.4%), while there were no significant differences in FR between the round-cornered conventional-ligating bracket and the round-cornered self-ligating bracket with 0.018″ stainless steel wires. However, the round-cornered self-ligating bracket exhibited the least FR (34.9 ± 5.1% and 39.3 ± 4.6%) with 0.018 × 0.025″ and 0.019 × 0.025″ stainless steel archwires, respectively. The sharp-cornered conventional-ligating bracket showed the highest FR of 72.4 ± 3.0% among the bracket systems tested in this study.

CONCLUSIONS

The round-cornered conventional-ligating bracket showed less FR when compared to sharp-cornered conventional-ligating bracket. Conversely, the round-cornered conventional-ligating bracket exhibited greater FR when compared to the round-cornered self-ligating bracket, with an exception with respect to the 0.018″ wire. In general, FR increased with increased wire dimension.

Self-Ligating Bracket Systems: A Comprehensive Review

Currently, ligature-free bracket technologies, including self-ligating brackets (SLBs), are all the rage in orthodontics. Self-ligating mechanisms have been shown to be more effective and less time-consuming in orthodontic treatment than traditional appliances due to their enhanced frictional properties. Crucial to the success of the multi-band/bracket method is the transmission of forces and moments from the bracket to the archwire. Advances in bracket design and ligation techniques are constantly being made to better distribute loads and increase the efficiency of leveling.

Comparative in vitro analysis of the sliding resistance of a modern 3D-printed polymer bracket in combination with different archwire types

Objectives

To analyse the sliding resistance of a modern 3D-printed polymer bracket combined with different archwire types and to compare the results with conventionally used polymeric, ceramic and metal brackets. It was of further interest which bracket-archwire combination could be best qualified for clinical use.

Materials and methods

The sliding behaviour was tested using an orthodontic measurement and simulation system (OMSS) for the use of two bracket types of the polymer, ceramic and metal group in combination with a 0.016 inch × 0.022 inch and 0.017 inch × 0.025 inch archwire of nickel-titanium (NiTi), titanium-molybdenum alloy (TMA) and stainless steel. Six bracket types were combined with six different archwire types and compared to each other.

Results

The sliding resistance showed significant differences between various the bracket-archwire complexes. The combination of 3D-printed polymer brackets with both steel archwire cross-sections showed the least values of sliding resistance (average 23–29%), while the combination of ceramic brackets with TMA archwires presented the highest (average 47%).

Conclusions

The present study could show that modern 3D-printed bracket materials can have similar or even better mechanical properties than conventional ones regarding sliding resistance. Although the combination of bracket and archwire material is decisive for low sliding resistance values, the selection of the bracket material seems to have a greater influence than the selection of the archwire material or its cross section.

Clinical relevance

It might be possible in future to combine aesthetic and biomechanical requirements for aesthetic brackets by using 3D-printing technology.

Study of force loss due to friction comparing two ceramic brackets during sliding tooth movement

OBJECTIVE

To compare the percentage of force loss generated during canine sliding movements in newly introduced ceramic brackets with metal brackets.

MATERIALS AND METHODS

Two types of ceramic brackets, namely polycrystalline alumina (PCA) ceramic brackets (Clarity Advanced) and monocrystalline alumina (MCA) ceramic brackets (Inspire Ice) were compared with stainless steel (SS) brackets (Victory Series). All bracket groups (n = 5 each) were for the maxillary canines and had a 0.018-inch slot size. The brackets were mounted on an Orthodontic Measurement and Simulation System (OMSS) to simulate the canine retraction movement into the first premolar extraction space. Using elastic ligatures, 0.016 × 0.022″ (0.40 × 0.56 mm) stainless steel archwires were ligated onto the brackets. Retraction force was applied via a nickel-titanium coil spring with a nearly constant force of approximately 1 N. The OMSS measured the percentage of force loss over the retraction path by referring to the difference between the applied retraction force and actual force acting on each bracket. Between group comparisons were done with one-way analysis of variance.

RESULTS

The metal brackets revealed the lowest percentage of force loss due to friction, followed by the PCA and MCA ceramic bracket groups (67 ± 4, 68 ± 7, and 76 ± 3 %, respectively). There was no significant difference between SS and PCA brackets (p = 0.97), but we did observe significant differences between metal and MCA brackets (p = 0.03) and between PCA and MCA ceramic brackets (p = 0.04).

CONCLUSION

PCA ceramic brackets, whose slot surface is covered with an yttria-stabilized zirconia-based coating exhibited frictional properties similar to those of metal brackets. Frictional resistance resulted in an over 60 % loss of the applied force due to the use of elastic ligatures.

Which Orthodontic Wire and Working Sequence Should be Preferred for Alignment Phase? A Review

The key to a successful orthodontic therapy depends not only on manual skills and knowledge about treatment steps, but also on knowledge and choice of materials used. One of the major components of fixed orthodontic therapy is the choice of wires. Orthodontic wires are defined as devices consisting of a wire conforming to the alveolar or dental arch, used as an anchorage in correcting irregularities in the position of the teeth. The history of these materials is as old as that of fixed orthodontic treatments and they present different features. With proper general knowledge, doctors can differentiate between wires and use the sufficient wire sequence suitable for each patient. This can increase the quality of treatment. Therefore, the aim of the present review is to focus on the differences in features of wires as well as the sequence of leveling wire selection according to the treatment plan.

Friction behavior of self-ligating and conventional brackets with different ligature systems

OBJECTIVES

Self-ligating brackets are widely believed to offer better clinical efficiency and, in particular, less friction. Thus, the goal of this in vitro investigation was to assess the friction behavior of different bracket/archwire/ligature combinations during simulated canine retraction. An important aspect of this work was to determine whether conventional bracket systems behave differently in passive or active self-ligating brackets used with a Slide™ ligature, an elastic ligature, or a steel ligature.

METHODS

Three conventional (Contour, Class One; Discovery(®), Dentaurum; Mystique MB, GAC) and six self-ligating (Carriere SL, Class One; Clarity™ SL, 3M Unitek; Damon3, Ormco; In-Ovation(®) C, GAC; Speed Appliance, Speed System™; QuicKlear(®), Forestadent(®)) bracket systems were analyzed. All brackets featured a 0.022″ slot (0.56 mm). Each conventional system was tested with a steel ligature (0.25 mm; Remanium(®), Dentaurum), an elastic ligature (1.3 mm in diameter; Dentalastics, Dentaurum), and a modified elastic ligature (Slide™; Leone(®)). Each combination was used with four archwires, including rectangular stainless steel (0.46 × 0.64 mm, 0.018 × 0.025″, Dentaurum), rectangular nickel-titanium with Teflon coating (0.46 × 0.64 mm, 0.018 × 0.025″, Forestadent(®)), round coaxial nickel-titanium (0.46 mm, 0.018″, Speed), and half-round/half-square (D-profile) stainless steel (0.46 mm, 0.018″, Speed). In the orthodontic measurement and simulation system (OMSS), retraction of a canine was simulated on a Frasaco model replicated in resin. Based on the force systems, the respective friction values were determined. For each combination of materials, five brackets of the same type were tested and five single measurements performed.

RESULTS

Friction values were found to vary distinctly with the different combinations, modifiers being the ligature systems and the archwire types. Any significant friction differences between the steel-ligated, Slide™-ligated, and self-ligated brackets were sporadic. All three systems were associated with average friction values of 40 %. Active self-ligating brackets and elastic-ligated conventional brackets, by contrast, generally differed significantly from the three above-mentioned bracket systems and showed distinctly higher friction values averaging 59 and 67 %, respectively.

CONCLUSIONS

While passive self-ligating bracket systems have frequently been touted as advantageous in the literature, they should not be regarded as the only favorable system. Steel-ligated and Slide™-ligated conventional bracket systems are capable of offering similar friction performance.

Comparison of frictional resistance of esthetic and semi-esthetic self-ligating brackets

AIM

The frictional resistance encountered during sliding mechanics has been well established in the orthodontic literature, and it consists of complex interactions between the bracket, archwire, and method of ligation the claim of reduced friction with self-ligating brackets is often cited as a primary advantage over conventional brackets. This study was done to compare and evaluate the frictional forces generated between fully esthetic brackets and semi-aesthetic self-ligating brackets, which are of passive form and SEM (scanning electron microscope) study of the Brackets after Frictional evaluation.

MATERIALS AND METHODS

Two types of self-ligating esthetic brackets, Damon clear (Ormco) made of fully ceramic and Opal (Ultradent Products, USA) and, Two types of self-ligating semi-esthetic brackets, Clarity SL (3M Unitek) and Damon 3 (Ormco) both of which are made of ceramic with metal slot. Arch wires with different dimensions and quality 17 × 25, 19 × 25 Titanium Molybdenum Alloy (TMA) and 17 × 25, 19 × 25 stainless steel that came from plain strands of wire were used for frictional comparison test. The brackets used in this study had 0.022 × 0.028 inch slot.

RESULTS

The statistical tests showed significantly smaller amount of kinetic frictional forces is generated by Damon 3 (semi-esthetic self-ligating brackets). For each wire used, Damon 3 displayed significantly lower frictional forces (P ≤ 0.05) than any of the self-ligating system, followed by Opal (fully esthetic self-ligating brackets) which generated smaller amount of frictional forces but relatively on the higher side when compared with Damon 3. Damon clear (fully esthetic self-ligating brackets) generated the maximum amount of kinetic forces with all types of wire dimensions and properties when compared to the other three types of self-ligating system. Clarity SL (semi-esthetic self-ligating brackets) generated smaller amount of frictional forces when compared with Damon clear and relatively higher amount of frictional forces when compared to Opal and Damon 3.

Different bracket-archwire combinations for simulated correction of two-dimensional tooth malalignment: Leveling outcomes and initial force systems

OBJECTIVES

Self-ligating brackets are widely believed to be more effective in clinical use and to involve less friction and force. Thus, the goal of this in vitro investigation was to experimentally assess the effectiveness of different bracket-archwire combinations and the force levels exerted in two-dimensional direction during correction of tooth malalignment. An important aspect of this objective was to determine whether the behaviors of conventional bracket systems with an elastic or steel ligature differ from that of self-ligating brackets.

MATERIALS AND METHODS

Three conventional (Mini Taurus®, RMO; Synergy®, RMO; Victory Series™, 3M Unitek) and three self-ligating bracket systems (Speed™, Strite; Smart Clip™, 3M Unitek; Time 3, American Orthodontics) were analyzed. All brackets had 0.018-inch (0.46-mm) slots and--except for the self-ligating brackets-were tested with both a steel ligature (0.25 mm; Remanium, Dentaurum) and an elastic rubber ligature (1.3 mm in diameter; Dentalastics, Dentaurum). They were fitted with four different round wires: a 0.30-mm stainless steel (3M Unitek), 0.38-mm stainless steel coaxial (Advanced Orthodontics), 0.30-mm Thermalloy NiTi (RMO), and 0.30-mm Orthonol NiTi (RMO) archwire. The orthodontic measurement and simulation system (OMSS) was used to simulate a two-dimensional (2 mm of infraocclusion and 2 mm of vestibular displacement) malalignment of tooth 21 inserted in a resin replica of a Frasaco model. Four brackets of the same type were assessed and four individual measurements taken per bracket to analyze initial force systems and corrective malalignment outcomes.

RESULTS

The initial force systems and tooth movements varied distinctly between the different material combinations in conjunction with the ligation systems and archwire types used. The force systems generated were readily reproducible across individual measurements. Leveling outcomes and force systems between conventional steel-ligated and self-ligating brackets coincided in most cases. Both of these device configurations corrected the malalignment by 78-99 % on average. Rubber-ligated conventional brackets, by contrast, performed significantly worse due to exertion of significantly higher forces and 60 % less of a leveling effect.

CONCLUSION

Our investigation demonstrates that both conventional steel-ligated brackets and self-ligating brackets, which are highlighted in the literature as highly efficient systems, lead to equivalent corrective outcomes in the treatment of tooth malalignments.

A systematic review and meta-analysis of experimental clinical evidence on initial aligning archwires and archwire sequences

The aim of the study was to assess treatment effects and potential side effects of different archwires used on patients receiving orthodontic therapy. Electronic and manual unrestricted searches were conducted in 19 databases including MEDLINE, Cochrane Library, and Google Scholar until April 2012 to identify randomized controlled trials (RCTs) and quasi-RCTs. After duplicate study selection, data extraction, risk of bias assessment with the Cochrane risk of bias tool, and narrative analysis, mean differences (MDs) with confidence intervals (CIs) of similar studies were pooled using a random-effects model and evaluated with GRADE. A total of 16 RCTs were included assessing different archwire characteristics on 1108 patients. Regarding initial archwires, meta-analysis of two trials found slightly greater irregularity correction with an austenitic-active nickel-titanium (NiTi) compared with an martensitic-stabilized NiTi archwire (corresponding to MD: 1.11 mm, 95% CI: -0.38 to 2.61). Regarding archwire sequences, meta-analysis of two trials found it took patient treated with a sequence of martensitic-active copper-nickel-titanium (CuNiTi) slightly longer to reach the working archwire (MD: 0.54 months, 95% CI: -0.87 to 1.95) compared with a martensitic-stabilized NiTi sequence. However, patients treated with a sequence of martensitic-active CuNiTi archwires reported general greater pain intensity on the Likert scale 4 h and 1 day after placement of each archwire, compared with a martensitic-stabilized NiTi sequence. Although confidence in effect estimates ranged from moderate to high, meta-analyses could be performed only for limited comparisons, while inconsistency might pose a threat to some of them. At this point, there is insufficient data to make recommendations about the majority of initial archwires or for a specific archwire sequence.

An in vitro comparison of the frictional forces between archwires and self-ligating brackets of passive and active types

The aim of this study was to compare the static and kinetic frictional forces generated by various contemporary designs of self-ligating brackets (SLBs) and different wire alloys. In total, six different brackets (four passive type SLB, one active SLB, and one conventional bracket) were investigated using stainless steel, nickel-titanium, and titanium-molybdenum alloy archwires of several sizes. The friction forces were measured by sliding on a bracket-wire combination system in an EZ instron testing machine. A scanning electron microscope (SEM) was used to examine the wear effects of the wall surfaces of bracket slots. Energy-dispersive spectroscopy (EDS) was used to identify the elemental compositions of the bracket surfaces. The data were collected and statistically analysed using analysis of variance. The results of static and kinetic frictional forces were lower in passive type SLBs (P < 0.05), except in the Smart Clip bracket. The wire materials or wire dimensions in the present study showed similar friction forces with no statistical differences (P > 0.05). The wearing effects were not obviously found in bracket slots under SEM observation. Only conventional brackets and mini-Clippy SLB revealed nickel ions via EDS analysis. This study shows that passive SLBs are associated with lower static or kinetic friction forces than those of active SLBs or conventional brackets. Wear on the bracket slots was not observed in the present study.

Frictional Resistance in Self-Ligating Orthodontic Brackets and Conventionally Ligated Brackets

Objective: To compare the amount of expressed frictional resistance between orthodontic self-ligating brackets and conventionally ligated brackets in vitro as reported in the literature.

Methods: Several electronic databases (Medline, PubMed, Embase, Cochrane Library, and Web of Science) were searched without limits. In vitro studies that addressed friction of self-ligating brackets compared with conventionally ligated brackets were selected and reviewed. In addition, a search was performed by going through the reference lists of the selected articles to identify any paper that could have been missed by the electronic searches.

Results: A total of 70 papers from the electronic database searches and 3 papers from the secondary search were initially obtained. After applying the selection criteria, only 19 papers were included in this review. A wide range of methods were applied.

Conclusions: Compared with conventional brackets, self-ligating brackets produce lower friction when coupled with small round archwires in the absence of tipping and/or torque in an ideally aligned arch. Sufficient evidence was not found to claim that with large rectangular wires, in the presence of tipping and/or torque and in arches with considerable malocclusion, self-ligating brackets produce lower friction compared with conventional brackets.

Alignment efficiency of Damon3 self-ligating and conventional orthodontic bracket systems: a randomized clinical trial

INTRODUCTION

The aim of this study was to compare the efficiency of mandibular tooth alignment and the clinical effectiveness of a self-ligating and a conventional preadjusted edgewise orthodontic bracket system.

METHODS

A multicenter randomized clinical trial was conducted in 2 orthodontic clinics. Sixty-two subjects (32 male, 30 female; mean age, 16.27 years) with mandibular incisor irregularities of 5 to 12 mm and a prescribed extraction pattern including the mandibular first premolars were randomly allocated to treatment with Damon3 self-ligating (Ormco, Glendora, Calif) or Synthesis (Ormco) conventionally ligated brackets. Fully ligated 0.014-in nickel-titanium archwires were used first in both groups, followed by a sequence of 0.014 x 0.025-in and 0.018 x 0.025-in nickel-titanium, and 0.019 x 0.025-in stainless steel. Study casts were taken at the start of treatment (T1), the first archwire change (T2), and the placement of the final 0.019 x 0.025-in archwire (T3). Cephalometric lateral skull and long-cone periapical radiographs of the mandibular incisors were taken at T1 and T3.

RESULTS

No significant difference was noted (P >0.05) in initial rate of alignment for either bracket system. Initial irregularity influenced subsequent rate of movement, but sex, age, and appliance type were statistically insignificant. Alignment was associated with an increase in intercanine width, a reduction in arch length, and proclination of the mandibular incisors for both appliances, but the differences were not significant. Incisor root resorption was not clinically significant and did not differ between systems.

CONCLUSIONS

Damon3 self-ligating brackets are no more efficient than conventional ligated preadjusted brackets during tooth alignment.

Resistance to sliding of orthodontic brackets with bumps in the slot floors and walls: effects of second-order angulation

OBJECTIVE

Two stainless steel (SS) bracket designs with two bumps across the slot floors and rounded slot walls and one polycrystalline alumina (PCA) bracket design with one bump along the slot floor were compared to conventional SS and PCA brackets.

METHODS

For each design, the resistances to sliding of four archwire-bracket couples, two in the dry state and two in the wet (saliva) state, were measured at 32 second-order angles between -12 and +12 degrees.

RESULTS

When clearances existed, the kinetic coefficients of friction of the SS brackets ranged from 0.13 to 0.15 in the dry state and from 0.17 to 0.18 in the wet state. For the PCA brackets, the kinetic coefficients of friction were 0.18 for both designs in the dry state and were 0.18 for the brackets with bumps and 0.24 for the brackets without bumps in the wet state.

SIGNIFICANCE

Overall, the bumps and rounded slot walls did not reduce classical friction. When the brackets with rounded slots were modeled, the critical contact angles for binding were larger than the values based on the apparent dimensions, but were less than those based on the true dimensions. When clearances did not exist, the rates of binding were greater for the SS brackets with bumps and rounded walls than for the conventional brackets. The rates of binding increased because the rounded walls forced the archwires into complex shapes. Both PCA bracket designs had similar rates of binding; but unlike the conventional design, the brackets with the bumps did not permanently deform the archwires at large angles.

Accuracy of third-order bends of nickel-titanium wires and the effect of high and low pressure during memorizing heat treatment

This study evaluated the accuracy of third-order bends of nickel-titanium wires and determined the effect of high and low pressure for maintaining the wire shape during memorizing heat treatment. A computer-aided bending machine was used to incorporate 200 randomly determined torsional angles between 0 degrees and 60 degrees into 30 linear 0.016 x 0.022-in NeoSentalloy F80 (GAC International, Central Islip, NY) wires. The torsional bendings were randomized into 2 groups. Bends assigned to group 1 (n = 100) received heat treatment of 1.6 MPa (16 bar) pressure, and bends assigned to group 2 (n = 100) received heat treatment of 50 MPa (500 bar) pressure. Cross-sectional cuts from the bent wires were prepared by using standard metallurgical techniques, and the torsional angles were analyzed under computer control. The results of our study show that third-order bends </= 30 degrees can be made with adequate clinical accuracy with an error of 1.89 degrees +/- 1.75 degrees (0 degrees to 10 degrees ) and 3.57 degrees +/- 1.57 degrees (20 degrees to 30 degrees ), irrespective of the pressure applied. With bends > 30 degrees but </= 40 degrees , the method with the higher pressure offers fundamentally greater precision than that with the lower pressure. With torque bends > 40 degrees , the bending error with both methods is clinically unacceptable. In addition to the variability in the dimension and composition of nickel-titanium wires, the scale of the incorporated plastic deformations makes a substantial contribution to the bending error. As far as permitted by the clinical situation, then, the bend should be distributed over the maximum possible wire length. Third-order bends in the first rectangular pseudoelastic nickel-titanium wires represent an efficient means of effecting torque at an early stage. This individualization allows the full therapeutic potential of these archwires to be exploited right from the initial phase of treatment.