Frictional changes in force values caused by saliva substitution

Assessment of the influence of metal ions released from the fixed orthodontic appliances on the static friction and surface topography of stainless steel and I archwires: An in-vitro study

BACKGROUND

Static friction force between the orthodontic brackets and wire impacts the sliding mechanics that affect teeth movements and treatment duration. This sliding media is jam-packed with released metal ions from the fixed appliances. This study aimed to assess the static frictional force and surface topography of stainless steel (SS) and I archwires in dry conditions and in media fully with metal ions that were released from fixed appliances.

METHODS

In this research study, a set of 60 as-received straight archwires specimens (5 cm wire) were employed and categorized into two groups based on the material type [30 super elastics new I archwires gauge (0.018 × 0.014 inch) and 30 SS archwires 0.018 × 0.022" as a control]. The archwires' static friction force was measured while sliding a loaded Roth SS brackets (0.018") on the archwire using a universal tensile testing machine in dry and metal ions released media, while the surface topography was assessed using a noncontact AFM machine.

RESULTS

The static friction of I archwire was significantly lower than the SS wire in dry condition. Metal ions media released from fixed appliances significantly reduced the Static friction compared to dry and wet conditions with deionized water for both wires. An Atomic Force Microscope machine surface roughness reports revealed that the highest mean of all three roughness parameters was found in the SS group, followed by I archwires in descending order. Additionally, metal ions media significantly reduce all roughness parameters.

Influence of Different Mouth Rinsing Agents on Friction During Sliding Mechanics Between Orthodontic Metal Brackets and Stainless Steel Archwire: A Comparative In Vitro Study

Aim and objectives The aim of this in-vitro study is to evaluate and compare the effect of various mouth rinsing agents on frictional resistance through sliding mechanics among orthodontic metal brackets and stainless steel (SS) archwire. Materials and methods Each group comprised 15 samples of maxillary first premolar pre-adjusted edgewise SS movable, un-bonded brackets (Koden Inc., United States) which were welded with a power arm, where 100 g of the load was suspended. Brackets were ligated with elastic modules (Koden Inc., United States) onto the perspex sheet along with 0.019" x 0.025" SS archwire (Classic Orthodontics, United States) and were suspended from the upper component of the Instron machine. The coefficient of friction was tested in dry conditions (control), artificial saliva (AS) (Wet Mouth, ICPA Health Product Ltd., India), 0.2% chlorhexidine gluconate (CHG) mouthwash (Hexidine, ICPA Health Product Ltd., India), 0.05% sodium fluoride (NaF) mouthwash (ACT Anti-Cavity Fluoride Mouthwash, Sanofi Company, United States), charcoal (CC) mouthwash (Hello Activated Charcoal Extra Freshening Mouthwash, Hello Products LLC, United States) and ozone-infused oil-pulling solution with coconut oil (O₃) (O₃ Essentials, Health Ranger Store, United States). In order to calculate the coefficient of friction, 50 L was added to the test sample while moving at a 5 mm/min crosshead speed. The groups were compared using the one-way analysis of variance (ANOVA), and Tukey's post hoc analysis was performed for multiple pairwise comparisons. Results The coefficient of friction with the highest mean values was observed with the control group (2.01), followed by AS (1.79), and the least with O₃ (1.15). Statistically significant differences were observed with almost all groups of mouth rinsing agents, but NaF is significant with CHG and CC. However, CHG did not have any significant difference from CC. Conclusions Lower coefficient of frictional values were observed with the ozone-infused oil-pulling solution with coconut oil during sliding mechanics between metal brackets and stainless steel archwire. Almost all the mouth rinsing agents showed a significantly different coefficient of friction value.

Assessment of frictional resistance and surface roughness in orthodontic wires coated with two different nanoparticles

Several mechanical and biological factors may change the orthodontic wire frictional resistance (FR). Titanium dioxide (TiO₂ ) and silica dioxide (SiO₂ ) nanoparticle (NP) coatings may be used to improve the characteristics of materials, reducing FR between archwire and bracket. This in vitro study aimed to evaluate the FR of orthodontic wires with and without coating in both dry and wet environments and measure the surface roughness (SR). One hundred and eighty segments of rectangular Cr-Ni orthodontic wires (Morelli Co, Brazil) were divided into three groups according to the NP coating applied: TiO₂ group; SiO₂ group; and control group. The SR parameters were measured in an optical profilometer, the surface morphology was analyzed with scanning electron microscopy (SEM), and FR was performed in a universal testing machine in dry and wet environments (n = 30). The statistical analysis was performed using the Generalized Estimated Equations model with a Bonferroni post-test (α = 0.05). It was observed that SiO₂ NP coating decreased FR significantly when compared to the TiO₂ and control groups, in both environments (p < .001). The SiO₂ and TiO₂ groups presented statistically lower SR than the control group and were similar to each other (p < .001). The SiO₂ group presented the lower depth of Valley parameter than the TiO₂ group (p < .001). The SEM showed that the TiO₂ coating had the most heterogeneous surface morphology than the SiO₂ and control groups. The orthodontic wires with NP coating modified the FR and morphology. The SiO₂ coating reduced FR in both dry and wet environments and decreased SR.

The effect of various nanoparticle coating on the frictional resistance at orthodontic wire and bracket interface: A systematic review

This systematic review was aimed to test the null hypothesis that coating of orthodontic wires with nanoparticles does not affect the frictional properties at bracket--wire interface. Electronic database searches were performed up to September 2020. In vitro studies were considered for reviewing process. Study selection, data extraction, risk of bias assessment was performed during reviewing process. Only qualitative analyses of included literature were done due to the presence of heterogeneity among the studies. Out of 1,068 retrieved records, nine studies satisfied the inclusion criteria and included in this review. Studies were assessed at low risk to high risk of bias according to certain parameters. Wide variety of nanoparticles were used for surface coating of orthodontic wires of variable sizes, shapes, and materials like stainless steel, NiTi, and TMA and placed into the slots of different types of orthodontic brackets to evaluate the alteration in frictional and other mechanical properties. Most of the studies clearly indicate that coating with nanoparticles decreases the friction between wire and bracket interface under specified in vitro conditions. Furthermore, among the nine included studies, only two considered evaluation of effect of coated brackets on frictional and other mechanical properties and results were heterogeneous. The null hypothesis is rejected and it is concluded that the wires coated with nanoparticles might offer a novel opportunity to substantially reduce frictional resistance at bracket--wire interface during tooth movement. Further studies are necessary to strengthen the evidence regarding effect of coated brackets on frictional properties.

Effect of different media on frictional forces between tribological systems made from self-ligating brackets in combination with different stainless steel wire dimensions

The purpose was to determine the effect of different environments (artificial saliva, human saliva, distilled water, dry storage) on frictional forces between various tribological systems made from self-ligating brackets in combination with stainless-steel wires (dimensions: 0.016″×0.022″, 0.018″×0.025″ and 0.019″×0.025″). An universal testing-machine applied a normal force of 1 N. Two-way ANOVA and Tukey post-hoc tests (α=5%) were used. Saliva had significantly higher frictional forces (p<0.001). Yet, the influence of the media depends on the wire dimensions. The results were not as straightforward as in 0.018″×0.025″, which had a clear order (dry storage<water<artificial saliva<human saliva, p<0.001 each). Except for human saliva, wire dimensions differed significantly from each other (p<0.001). Increasing wire cross-sections increases frictional force. Thus, saliva acts as adhesive. High frictional forces of larger wires are attributed to the contact between latch and wire. Still, in-vitro experiments can only approximate the quasi-static tooth movement and the various fluids in the mouth.

Comparative evaluation of Stainless-steel wires and brackets coated with nanoparticles of Chitosan or Zinc oxide upon friction: An in vitro study

OBJECTIVE

The present study was performed to affirm surface characterization, as well as to compare the effect of coating of stainless-steel (SS) orthodontic brackets and wires by nanoparticles Chitosan (CTS) or Zinc oxide (ZnO) during friction.

MATERIAL AND METHODS

Seventy SS brackets for the upper right central incisors with a 0.022-inch system and seventy 0.019×0.025-inch SS rectangular wires, with and without ZnO and CTS nanoparticle coating, were used. Coating was analysed by SEM. A universal testing machine was used to calculate the friction between the wires and brackets. Statistical analysis was performed using one-way ANOVA and Tukey's tests.

RESULTS

Significant differences were detected between coated and uncoated wires and brackets for friction with either ZnO or CTS nanoparticles. The mean values of the wires and brackets coated with ZnO and CTS nanoparticles were 0.64±0.24N and 0.85±0.23N, respectively, while they were 1.79±0.61N for the uncoated group. In addition, there was a significant decrease of about 64% and 53% found after coating with ZnO and CTS nanoparticles, respectively. The results of CTS nanoparticle coating were consistent with those of ZnO nanoparticles.

CONCLUSIONS

Friction force decreased significantly after coating of CTS or ZnO nanoparticles. These nanoparticles provide an opportunity to reduce friction during tooth movement, resulting in better anchorage control, reduced treatment time and risk of root resorption.

Nanomaterials Application in Orthodontics

Nanotechnology has gained importance in recent years due to its ability to enhance material properties, including antimicrobial characteristics. Nanotechnology is applicable in various aspects of orthodontics. This scientific work focuses on the concept of nanotechnology and its applications in the field of orthodontics, including, among others, enhancement of antimicrobial characteristics of orthodontic resins, leading to reduction of enamel demineralization or control of friction force during orthodontic movement. The latter one enables effective orthodontic treatment while using less force. Emphasis is put on antimicrobial and mechanical characteristics of nanomaterials during orthodontic treatment. The manuscript sums up the current knowledge about nanomaterials' influence on orthodontic appliances.

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.

Lubricating conditions: effects on friction between orthodontic brackets and archwires with different cross-sections

OBJECTIVE

This study investigated the effect of the condition of lubrication on the friction between brackets and NiTi archwires of different rounded cross-sections.

METHODS

Brackets (Roth, GAC) were affixed to a device connected to a universal testing machine into which segments of archwire were placed (NiTi, Nitinol, GAC) with cross-sections of 0.012-in, 0.016-in and 0.020-in. Once the wire was in the bracket slot, the following lubricants were applied: human saliva (HS: positive control), distilled water (DI), mucin-based (MUC) or carboxymethylcellulose-based (CMC) artificial saliva. In the negative control group, no lubricant was used. The combination between the wire cross-sections and the lubrication condition generated 15 groups with 15 samples each. Data were submitted to two-way analysis of variance and Tukey's test.

RESULTS

There was no significant interaction between the wire cross-section and the condition of lubrication (p= 0.901). Irrespective of whether lubricants were used or not, there was a significant increase in friction with an increase in the cross-section of the wire (p< 0.001). For any wire, the group tested in the presence of MUC was not different from that in which HS was applied. On the other hand, when the application of lubricants was suppressed, significantly higher friction values were observed. The CMC group and the DI group demonstrated intermediate behavior.

CONCLUSIONS

Friction increased with the increase of the cross-section of the NiTi archwire, but regardless of the archwire, friction with MUC artificial saliva was similar to that of HS and lower than in dry conditions.

In vitro comparison of frictional forces of a new polycrystalline ceramic bracket versus metal-insert ceramic bracket before and after aging

OBJECTIVE

The purpose of this study was to compare the friction of two types of polycrystalline ceramic brackets before and after aging.

METHODS

A total of 60 second-upper right premolar brackets were divided into two groups: Clarity™ Advanced (3M Unitek, Monrovia, CA) and Clarity™ (3M Unitek). All brackets had a nominal 0.022-in slot size and a McLaughlin Bennett Travesi (MBT) prescription. Each bracket was submitted to a friction test, using the YL01 UTM universal testing machine (YLE GMBH, Germany) before and after thermocycling. All tests were carried out in the presence of artificial saliva, using .019×.025-in. rectangular stainless steel (SS) archwires (3M Unitek). Bracket slot surfaces were observed under an optical microscope (Olympus CX41, Tokyo, Japan) before and after aging.

RESULTS

Before aging, the Clarity Advanced group showed significantly lower friction than the Clarity group (P=0.011). After aging, the friction of the Clarity Advanced bracket decreased significantly (P<0.001), whereas the friction of the Clarity bracket increased significantly (P<0.001). The microscopic qualitative evaluation showed that the slot surfaces of all aged Clarity brackets revealed important pit corrosion when compared with the original brackets.

CONCLUSIONS

The new Clarity Advanced ceramic bracket shows good physical friction properties due to the various modifications added by the manufacturers.

Evaluation and Comparison of Two Different Mouthwashes on Frictional Resistance Between Orthodontic Bracket and Archwire: An in Vitro Study

Aims: This study aimed to evaluate and compare the effect of tea tree oil (TTO) mouthwash and chlorhexidine (CHX) mouthwash on frictional resistance.

Settings and Design: In vitro.

Materials and Methods: In total, 60 extracted premolars were mounted on a custom-made acrylic fixture. These 60 premolars were randomly divided into 3 groups of 20 each, on which 0.022″ × 0.028″ slot MBT stainless steel brackets were bonded and 0.019″ × 0.025″ rectangular stainless steel wire was ligated with an elastomeric module. The 3 groups included a control group where the samples were immersed in artificial saliva and 2 experimental groups immersed in 0.2% CHX and TTO mouthwash, respectively, for 1.5 hours. Postimmersion static frictional resistance was evaluated on a universal testing machine at crosshead speed of 0.5 mm/min.

Statistical Analysis Used: Tukey’s post hoc procedure.

Results: This study showed a statistically significant difference in the frictional resistance between saliva and CHX groups and CHX and TTO groups ( P < .05). No statistically significant difference was observed between saliva and TTO groups ( P > .05). The frictional resistance was more in the CHX mouthwash group than in the TTO mouthwash group.

Conclusions: Frictional resistance was lesser in the TTO mouthwash than in the CHX mouthwash. Based on this result, TTO mouthwash can be used instead of CHX mouthwash as an oral hygiene aid in patients with orthodontic treatments.

An in vitro Evaluation of Friction Characteristics of Conventional Stainless Steel and Self-ligating Stainless Steel Brackets with different Dimensions of Archwires in Various Bracket-archwire Combination

AIM

The purpose of this research is to compare the frictional attributes of stainless steel conventional brackets and self-ligating stainless steel brackets with different dimensions of archwires.

MATERIALS AND METHODS

The test was carried with two sets of maxillary brackets: (1) Conventional stainless steel (Victory Series), (2) stainless steel self-ligating (SmartClip) without first premolar brackets. Stainless steel, nickel-titanium (NiTi), and beta-Ti which are the types of orthodontic wire alloys were tested in this study. To monitor the frictional force, a universal testing machine (Instron 33R 4467) that comprises 10 kg tension load cell was assigned on a range of 1 kg and determined from 0 to 2 kg, which allows moving of an archwire along the brackets. One-way analysis of variance was used to test the difference between groups. To analyze the statistical difference between the two groups, Student's t-test was used.

RESULTS

For Victory Series in static friction, p-value was 0.946 and for kinetic friction it was 0.944; at the same time for SmartClip, the p value for static and kinetic frictional resistance was 0.497 and 0.518 respectively. Hence, there was no statistically significant difference between the NiTi and stainless steel archwires.

CONCLUSION

It is concluded that when compared with conventional brackets with stainless steel ligatures, self-ligating brackets can produce significantly less friction during sliding. Beta-Ti archwires expressed high amount of frictional resistance and the stainless steel archwires comprise low frictional resistance among all the archwire materials.

CLINICAL SIGNIFICANCE

In orthodontics, frictional resistance has always had a major role. Its ability to impair tooth movement leads to the need for higher forces to move the teeth and it extends the treatment time which results in loss of posterior anchorage. Friction in orthodontics is related with sliding mechanics when a wire is moving through one or a series of bracket slots.

The Effects of In-Office Reconditioning on the Slot Dimensions and Static Frictional Resistance of Stainless Steel Brackets

INTRODUCTION

Orthodontists are commonly faced with the decision of what to do with loose brackets, and with inaccurately located brackets that need repositioning during treatment. One solution is to recycle the brackets. The potential effects of reconditioning a bracket are dependent upon many factors which may result in physical changes like alteration in slot tolerance, which may influence sliding mechanics by affecting frictional resistance.

AIM

To study and compare the dimensional changes in the bracket slot width and depth in reconditioned brackets from unused brackets under scanning electronic microscope and to study and compare any consequent effects on the static frictional resistance of stainless steel brackets after reconditioning and in unused brackets.

MATERIALS AND METHODS

Dentarum manufactured 90 stainless steel central incisors edgewise brackets of size 0.22 X 0.030″ inch and 0° tip and 0°angulation were taken. 60 samples for measuring frictional resistance and 30 samples for measuring slot dimensions. Ortho organizers manufactured stainless steel arch wires 0.019 X 0.025″ straight lengths 60 in number were considered for measuring static frictional resistance.

RESULTS

The mean slot width and depth of new brackets were 0.0251″ and 0.0471″, which exceeded the manufacturers reported nominal size of 0.022″ X 0.030″, by 0.003″ and 0.017″. The reconditioned brackets demonstrated a further increase in mean slot width and depth to 0.028″ and 0.0518″ that is by 0.0035″ and 0.0047″ which is statistically significant (p=0.001, 0.002). The mean static frictional forces of the reconditioned brackets was nearly similar to that of new brackets that is 0.3167N for reconditioned brackets and 0.2613 N for new brackets.

CONCLUSION

Although the reconditioning process results in physical changes to bracket structure this does not appear to result in significant effect on ex-vivo static frictional resistance.

Friction in orthodontics

Conventional wisdom suggests that resistance to sliding (RS) generated at the wire-bracket interface has a bearing on the force transmitted to the teeth. The relative importance of static and kinetic friction and also the effect of friction on anchorage has been a topic of debate. Lot of research work has been done to evaluate the various factors that affect friction and thus purportedly retards the rate of tooth movement. However, relevancy of these studies is questionable as the methodology used hardly simulates the oral conditions. Lately studies have concluded that more emphasis should be laid on binding and notching of archwires as these are considered to be the primary factors involved in retarding the tooth movement. This article reviews the various components involved in RS and the factors affecting friction. Further, research work should be carried out to provide cost effective alternatives aimed at reducing friction.

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.

A comparative evaluation of static frictional resistance using various methods of ligation at different time intervals: an in vitro study

Aim. To compare and evaluate the static frictional resistance offered by the four different types of ligation methods in both dry and wet conditions and at different durations when immersed in artificial saliva. Material and Methods. Alastik Easy to Tie modules, Super Slick Mini Stix elastomeric modules, Power “O” modules, and 0.009^″ Stainless Steel ligatures were used to compare the static friction using maxillary canine and premolar Preadjusted Edgewise brackets with 0.022^″ × 0.028^″ slot and 0.019^″ × 0.025^″ stainless steel wires. Results. The mean frictional resistance for Alastik modules was the lowest and that of Stainless Steel ligatures was found to be highest among the four groups compared and the difference among the four groups was statistically significant (P < 0.005). The mean static frictional resistance in all groups under dry conditions was lower than that under wet conditions. No statistical significant differences were found when the groups were compared at different time periods of immersion in artificial saliva. Conclusion. This study concludes that the Alastik modules showed the lowest mean static frictional forces compared to any other ligation method, though no significant difference was found for different time periods of immersion in the artificial saliva.

In vitro assessment of competency for different lingual brackets in sliding mechanics

AIM

To determine the static frictional resistance of different lingual brackets at different second order angulations when coupled with stainless steel (SS) archwire in dry and wet conditions.

MATERIALS AND METHODS

Using a modified jig, frictional resistance was evaluated under different conditions for a total of 270 upper premolar lingual brackets (0.018″ × 0.025″ - conventional - 7(th) generation and STb, self-ligating - evolution) with no in-built tip or torque together with 0.016″ × 0.022″ straight length SS archwires. For conventional brackets, the archwire was secured with 0.008″ preformed SS short ligature ties.

STATISTICAL ANALYSIS

One way analysis of variance with Tukey HSD as post-hoc test was applied for degree wise and bracket wise comparison within dry condition and wet condition. For pair wise comparison Student's t-test was used.

RESULTS

Under both conditions the static frictional resistance is significantly higher for self-ligating brackets at 0°, while at 5° and 10° it is higher for 7(th) generation brackets. Statistically, significant difference does not exist at 0° between conventional brackets and the same was found at 5° and 10° between STb and self-ligating brackets. With an increase in second order angulations, all the evaluated samples exhibited an increased frictional value. Wet condition samples obtained a higher value than their corresponding dry condition.

CONCLUSION

The self-ligating bracket evaluated in this in vitro study is not beneficial in reducing friction during en-mass retraction due to its interactive clip type.

The effects of salivas on occlusal forces

Contacting surfaces of opposing teeth produce friction that, when altered, changes the contact force direction and/or magnitude. As friction can be influenced by several factors, including lubrication and the contacting materials, the aim of this study was to measure the occlusal load alterations experienced by teeth with the introduction of different salivas and dental restorative materials. Pairs of molar teeth were set into occlusion with a weighted maxillary tooth mounted onto a vertical sliding assembly and the mandibular tooth supported by a load cell. The load components on the mandibular tooth were measured with three opposing pairs of dental restorative materials (plastic denture, all-ceramic and stainless steel), four (human and three artificial) salivas and 16 occlusal configurations. All lateral force component measurements were significantly different (P < 0·0001) from the dry (control) surface regardless of the crown material or occlusal configuration, while the effects of the artificial salivas compared to each other and to human saliva depended on the crown material.

Efficacy of Super Slick elastomeric modules in reducing friction during sliding: a comparative in vitro study

AIM

To evaluate and compare the frictional resistance produced by Super Slick modules during sliding with four different types of brackets and four ligature types both in conventional and figure-of-8 ligation method with saliva as lubricant.

MATERIALS AND METHODS

The frictional resistance was evaluated by using four different ligatures on 0.019" × 0.025" stainless steel (SS) archwires using four different brackets using an universal testing machine with unstimulated saliva as a lubricant. Mean and SD values were calculated. Data was statistically analyzed using analysis of variance ANOVA with post hoc test.

RESULTS

The results showed that self-ligating brackets produced least frictional forces. Among all other tested combinations,Tefon-coated SS ligatures in ceramic with metal slot brackets produced least coefficient of static and kinetic friction and full ceramic brackets ligated with Super Slick elastomeric modules demonstrated the highest, with other combinations falling in between.

CONCLUSION

Super Slick elastomeric modules, produced highest coefficient of both static and kinetic friction with the conventional and figure-of-8 ligation technique even in wet conditions using natural fresh human saliva.

CLINICAL SIGNIFICANCE

Both static and kinetic frictional resistance play an important role during sliding mechanics. Various factors have been attributed for friction. However, bracket type, archwire material, type of ligature and method of ligation are important variables. Recently polymeric coated slick elastomeric modules were introduced with the claim that they produce very low frictional forces in wet condition. Contrary to the claim made by the manufacturers of Super Slick elastomeric modules, they produced highest coefficient of both static and kinetic friction with the conventional and figure-of-8 ligation technique.

Role of lubricants on friction between self-ligating brackets and archwires

OBJECTIVE

To evaluate the effect of different lubricants on friction between orthodontic brackets and archwires.

MATERIALS AND METHODS

Active (Quick, Forestadent) and passive (Damon 3MX, Ormco) self-ligating brackets underwent friction tests in the presence of mucin- and carboxymethylcellulose (CMC)-based artificial saliva, distilled water, and whole human saliva (positive control). Dry friction (no lubricant) was used as the negative control. Bracket/wire samples (0.014 × 0.025 inch, CuNiTi, SDS Ormco) underwent friction tests eight times in a universal testing machine.

RESULTS

Two-way analysis of variance showed no significant interaction between bracket type and lubricant (P  =  .324). Friction force obtained with passive self-ligating brackets was lower than that for active brackets (P < .001). Friction observed in the presence of artificial saliva did not differ from that generated under lubrication with natural human saliva, as shown by Tukey test. Higher friction forces were found with the use of distilled water or when the test was performed under dry condition (ie, with no lubricant).

CONCLUSION

Lubrication plays a role in friction forces between self-ligating brackets and CuNiTi wires, with mucin- and CMC-based artificial saliva providing a reliable alternative to human natural saliva.

Coating NiTi archwires with diamond-like carbon films: reducing fluoride-induced corrosion and improving frictional properties

This study aims to coat diamond-like carbon (DLC) films onto nickel-titanium (NiTi) orthodontic archwires. The film protects against fluoride-induced corrosion and will improve orthodontic friction. 'Mirror-confinement-type electron cyclotron resonance plasma sputtering' was utilized to deposit DLC films onto NiTi archwires. The influence of a fluoride-containing environment on the surface topography and the friction force between the brackets and archwires were investigated. The results confirmed the superior nature of the DLC coating, with less surface roughness variation for DLC-coated archwires after immersion in a high fluoride ion environment. Friction tests also showed that applying a DLC coating significantly decreased the fretting wear and the coefficient of friction, both in ambient air and artificial saliva. Thus, DLC coatings are recommended to reduce fluoride-induced corrosion and improve orthodontic friction.

Assessment of the dimensions and surface characteristics of orthodontic wires and bracket slots

OBJECTIVE

The purpose of this study was to evaluate the dimensions and surface characteristics of orthodontic wires and bracket slots of different commercial brands.

METHODS

Thirty metallic brackets (0.022 x 0.028-in and 0.022 x 0.030-in) were divided into three groups: DYN/3M group = Dyna-Lock, 3M/Unitek (stainless steel, or SS); STD/MO group = Slim Morelli (SS); and Ni-Free/MO group = Slim Morelli (Ni-Free). The stainless steel wires (0.019 x 0.025-in) were divided into two groups: MO group = Morelli; and 3M group = 3M/Unitek. The bracket and wire measurements were done by two methods: (a) Surface Electron Microscopy (SEM), and (b) Profile Projection. The surface analysis was done qualitatively, based on SEM images and/or by a rugosimeter. The quantitative results were analyzed by ANOVA with Tukey's test (p < 0.05) and Student's t test.

RESULTS

A significant difference in the dimensions of slots was observed, and the NiFree/MO group showed the greatest changes when compared to the other groups. The analysis of surface topography of the brackets indicated greater homogeneity of the metallic matrix for DYN/3M and STD/MO groups. As for the dimensions of the wires, groups showed statistically different mean heights.

CONCLUSIONS

It was concluded that wires and brackets slots can present altered dimensions, which might directly and unintentionally affect the planned tooth movement.

The comparison of frictional resistance in titanium, self-ligating stainless steel, and stainless steel brackets using stainless steel and TMA archwires: An in vitro study

Aim:

The aim of the study was to compare the frictional resistance of titanium, self-ligating stainless steel, and conventional stainless steel brackets, using stainless steel and titanium molybdenum alloy (TMA) archwires.

Materials and Methods:

We compared the frictional resistance in 0.018 slot and 0.022 slot of the three brackets – titanium, self-ligating stainless steel, and conventional stainless steel – using stainless steel archwires and TMA archwires. An in vitro study of simulated canine retraction was undertaken to evaluate the difference in frictional resistance between titanium, self-ligating stainless steel, and stainless steel brackets, using stainless steel and TMA archwires.

Results and Conclusion:

We compared the frictional resistance of titanium, self-ligating stainless steel, and conventional stainless steel brackets, using stainless steel and TMA archwires, with the help of Instron Universal Testing Machine. One-way analysis of variance (ANOVA), Student's “t” test, and post hoc multiple range test at level of <0.05 showed statistically significant difference in the mean values of all groups. Results demonstrated that the titanium, self-ligating stainless steel, and stainless steel brackets of 0.018-inch and 0.022-inch slot had no significant variations in frictional résistance. The self-ligating bracket with TMA archwires showed relatively less frictional resistance compared with the other groups. The titanium bracket with TMA archwires showed relatively less frictional resistance compared with the stainless steel brackets.

FRICTION OF STAINLESS STEEL, NICKEL-TITANIUM ALLOY, AND BETA-TITANIUM ALLOY ARCHWIRES IN TWO COMMONLY USED ORTHODONTIC BRACKETS

In orthodontic treatment, the efficiency of tooth movement is affected by the frictional force between the archwire and bracket slot. This study evaluated the static and kinetic frictional forces produced in different combinations of orthodontic archwires and brackets. Three types of archwires [stainless steel, nickel-titanium (NiTi) alloy, and beta-titanium (TMA) alloy] and two types of brackets (stainless steel and self-ligating) were tested. Both static and kinetic frictional forces of each archwire–bracket combination were measured 25 times using a custom-designed apparatus. The surface topography and hardness of the archwires were also evaluated. All data were statistically analyzed using two-way analysis of variance and Tukey's test. The experiments indicated that the static frictional force was significantly higher than the kinetic frictional force in all archwire–bracket combinations not involving TMA wire. TMA wire had the highest friction, followed by NiTi wire, and then stainless steel wire when using the stainless steel bracket. However, there was no difference between NiTi and stainless steel archwires when using the self-ligating bracket. For TMA wire, the friction was higher when using the stainless steel bracket than when using the self-ligating bracket. Scanning electron microscopy indicated that stainless steel wire exhibited the smoothest surface topography. The hardness decreased in the order of stainless steel wire > TMA wire > NiTi wire. This study demonstrates that the frictional forces of brackets are influenced by different combinations of bracket and archwire. The reported data will be useful to orthodontists.

The effect upon friction of the degradation of orthodontic elastomeric modules

Orthodontic elastomeric modules are susceptible to degradation and deformation after time in the mouth. The aims of this study were to determine whether degradation of elastomeric modules significantly affects friction during sliding mechanics and to investigate whether there is a difference in the behaviour of elastomeric modules after storage in both in vivo and in vitro environments. An Instron testing machine was used to determine the friction generated by elastomeric modules on 0.019 × 0.025 inch stainless steel archwires at 4 degrees of bracket tip. Four brands of modules were tested straight from the packet (n = 15), after storage in artificial saliva (n = 15), and after being in patients' mouths (n = 32). Modules were tested after 24 hours, 1 week, and 6 weeks after storage in both in vivo and in vitro. Analysis of variance revealed that the degradation of elastomeric modules had a variable affect upon friction and that each storage medium produced a distinct pattern of frictional resistance. Modules stored in artificial saliva experienced a significant reduction in friction (P < 0.001) while modules collected from patients' mouths produced similar friction to modules tested straight from the packet. TP Super Slick® modules under dry test conditions produced significantly greater friction than the other three types of test modules (P < 0.001). The structure and surface characteristics of elastomeric modules may affect frictional resistance when a bracket slides along an archwire. These effects vary according to time, storage medium, and brand of elastomeric material.

Comparison of friction force between corroded and noncorroded titanium nitride plating of metal brackets

INTRODUCTION

Titanium nitride (TiN) plating is a method to prevent metal corrosion and can increase the surface smoothness. The purpose of this study was to evaluate the friction forces between the orthodontic bracket, with or without TiN plating, and stainless steel wire after it was corroded in fluoride-containing solution.

METHODS

In total, 540 metal brackets were divided into a control group and a TiN-coated experimental group. The electrochemical corrosion was performed in artificial saliva with 1.23% acidulated phosphate fluoride (APF) as the electrolytes. Static and kinetic friction were measured by an EZ-test machine (Shimadazu, Tokyo, Japan) with a crosshead speed of 10 mm per minute over a 5-mm stretch of stainless steel archwire. The data were analyzed by using unpaired t test and analysis of variance (ANOVA).

RESULTS

Both the control and TiN-coated groups' corrosion potential was higher with 1.23% APF solution than with artificial solution (P <0.05). In brackets without corrosion, both the static and kinetic friction force between the control and TiN-coated brackets groups showed a statistically significant difference (P <0.05). In brackets with corrosion, the control group showed no statistical difference on kinetic or static friction. The TiN-coated brackets showed a statistical difference (P <0.05) on kinetic and static friction in different solutions.

CONCLUSION

TiN-coated metal brackets, with corrosion or without corrosion, cannot reduce the frictional force.

Frictional resistance between orthodontic brackets and archwire: an in vitro study

AIM

The purpose of this investigation was to determine the kinetic frictional resistance offered by stainless steel and Titanium bracket used in combination with rectangular stainless steel wire during in vitro translatory displacement of brackets.

MATERIALS AND METHODS

In this study. Brackets: (All brackets used had a torque of - 7° and an angulation of 0°): (1) Dynalock (Unitek) 0.018'' slot, 3.3 mm bracket width, (2) Mini Uni-Twin (Unitek) 0.018'' slot, 1.6 mm bracket width, (3) Ultra-Minitrim (Dentaurum) 0.022'' slot 3.3 mm bracket width, (4) Titanium (Dentaurum) 0.022'' slot, 3.3 mm bracket width. WIRES: (1) 0.016 x 0.022'' stainless steel (Dentaurum), (2) 0.017 x 0.025''stainless steel (Unitek), (3) 0.018 x 0.025'' stainless steel (Dentaurum), elastomeric modules (Ortho Organisers), 0. 009'' stainless steel ligature wires, hooks made of 0.021 x 0.025'' stainless steel wires, super glue to bond the hooks to the base of the bracket, acetone to condition the bracket and wires before testing and artificial saliva. Brackets were moved along the wire by means of an Instron universal testing machine (1101) and forces were measured by a load cell. All values were recorded in Newtons and then converted into gms (1N-102 gm). 200 gm was then subtracted from these values to find out the frictional force for each archwire/bracket combination. For each archwire/ bracket combination three readings were taken under wet and dry condition and also with stainless steel ligature and elastomeric modules separately.

RESULTS

The results showed that narrow brackets generated more friction than wider brackets. Frictional force was directly proportional to wire dimension. Titanium brackets generated more friction than stainless steel brackets. Archwire and bracket ligated with elastomeric module generated more friction than when ligated with stainless steel ligature wire. Frictional forces in the wet condition were greater than in the dry condition for all archwire to bracket combinations.

CONCLUSION

Frictional force was seen to be inversely proportional to bracket width, frictional force was inversely proportional to bracket width, and in the wet condition were greater than in the dry condition for all archwire to bracket combinations.

CLINICAL SIGNIFICANCE

This study of friction is its role in lessening the force actually received by a tooth from an active component such as a spring, loop or elastic. Hence greater applied force is needed to move a tooth with a bracket archwire combination demonstrating high magnitudes of friction compared with one with a low frictional value.

Evaluation of frictional forces between ceramic brackets and archwires of different alloys compared with metal brackets

The aim of this study was to evaluate, in vitro, frictional forces produced by ceramic brackets and arch wires of different alloys. Frictional tests were performed on three ceramic brackets: monocrystalline (Inspire ICE), polycrystalline (InVu), polycrystalline with metal slot (Clarity), and one stainless steel bracket (Dyna-Lock). Thirty brackets of each were tested, all with .022' slots, in combination with stainless steel and nickel-titanium wires .019' x .025', at 0 degrees and 10 degrees angulation, in artificial saliva. Arch wires were pulled through the slots at a crosshead speed of 10 mm/min. There were statistically significant differences between the groups of brackets and wires studied (p < .05). The polycrystalline brackets with metal slots had values similar to those of conventional polycrystalline brackets, and the monocrystalline brackets had the highest frictional forces. The nickel-titanium wires produced the lowest friction. The addition of metal slots in the polycrystalline brackets did not significantly decrease frictional values. Nickel-titanium wires produced lower friction than those of stainless steel.

Self-Ligation Esthetic Brackets with Low Frictional Resistance

Objective: To test the frictional resistance forces (FRS) generated between several archwires and (1) interactive self-ligating (ISL) brackets and (2) conventionally ligated (CL) brackets.

Materials and Methods: Frictional forces produced between three different archwire combinations and self-ligating (SL) brackets (ceramic and metal-slot or all-metal) and CL brackets (metal or ceramic) were evaluated in a dry environment. The three ISL brackets tested were In-Ovation-C, In-Ovation-R, and Damon 3. The three CL brackets were Mystique with Neo Clip, Clarity, and Ovation. Each bracket was tested with 0.020″ SS, 0.019″ × 0.025″ SS and 0.018″ × 0.018″ coated SS.

Results: The ISL brackets generally exhibited the lowest frictional forces irrespective of the bracket material and the wire size, and CL brackets exhibited consistently higher frictional forces. Mystique with Neo Clip produced the lowest frictional resistance of all brackets. The In-Ovation-C brackets demonstrated significantly lower frictional resistance than the SL brackets In-Ovation-R and Damon 3 as well as the CL brackets Clarity and Ovation.

Conclusions: The ISL ceramic brackets produced the lowest frictional resistance of all the self-ligating brackets. The CL ceramic brackets produced the greatest friction.

Resistance to sliding with 3 types of elastomeric modules

INTRODUCTION

Super Slick (TP Orthodontics, LaPorte, Ind), a polymeric-coated ligature, has recently been introduced to the orthodontic market. The manufacturer claims it will significantly reduce friction. The purposes of this study were to determine whether Super Slick modules show lower friction than round and rectangular modules and to put the frictional forces into perspective with a self-ligating bracket.

METHODS

Maxillary premolar, stainless steel, self-ligating, and monocrystalline brackets with .022-in slots were used with straight lengths of .018-in and .019 x .025-in stainless steel wires. Buccal segment models were set up with 1 molar band and 2 premolar brackets for each test group: self-ligating brackets with the slide closed, self-ligating brackets with the slide open, and monocrystalline brackets. The latter 2 groups were tested with all 3 types of elastomeric module. Each setup was tested both under dry conditions and after soaking in a water bath for 1 hour.

RESULTS

The self-ligating brackets demonstrated virtually zero friction with each combination of wire and environmental condition. When the different bracket and elastomeric module combinations were compared, significant differences were observed. In all but 2 combinations, round modules provided the least resistance to sliding and rectangular modules the greatest, with Super Slick modules in between the 2. The self-ligating bracket provided the least resistance to sliding of all the bracket/ligation combinations and almost entirely eliminated friction under the conditions of this experiment.

CONCLUSIONS

Super Slick modules demonstrated greater resistance to sliding than conventional round modules, but not rectangular. Self-ligating brackets provided the least resistance to sliding of all bracket/ligation combinations and were the only method that almost entirely eliminated friction. The .018-in and .019 x .025-in wires exhibited similar friction in the dry state, but, when wet, the .018-in wire produced less friction. Ceramic brackets demonstrated greater resistance to sliding than stainless steel brackets. Lubrication reduced the friction with .018-in wires and increased it for .019 x .025-in wires.

In vitro friction of stainless steel arch wire-bracket combinations in air and different aqueous solutions

OBJECTIVES

To investigate the in vitro coefficient of friction of stainless steel arch wire-bracket combinations under fretting contact test conditions performed in air and in different aqueous solutions, like Ringer solution, Ringer with addition of a buffer, Ringer with addition of glucose, and Coca Cola.

METHODS

The fretting test set-up used allowed to control on-line the contact configuration and the positioning of the contacting parts. A specific positioning method was used to achieve a parallel alignment of arch wire and bracket slot. The effect of arch wire size, roughness, and test environment were investigated.

RESULTS

It was found that the aqueous solutions act as a lubricant compared to air. Friction was affected by the arch wire width while the roughness was found to have a limited effect. Stainless steel 0.018'' x 0.025'' arch wires exhibited higher frictional forces than stainless steel 0.017'' x 0.025'' arch wires on sliding against stainless steel 0.018'' x 0.025'' brackets in the selected test environments when tested under identical fretting test conditions. The wear damage on the arch wire after these in-vitro fretting tests was investigated. It revealed that these in-vitro tests are governed by a competition between oxidational wear and abrasive wear taking place at contact areas between brackets and arch wires.

CONCLUSIONS

For all aqueous solutions a lower coefficient of friction was found compared to tests performed in ambient air.

In vitro evaluation of frictional forces between archwires and ceramic brackets

The aim of this study was to evaluate the frictional force between orthodontic brackets and archwires. The differences in magnitude of the frictional forces generated by ceramic brackets, ceramic brackets with metal reinforced slot, and stainless steel brackets in combination with stainless steel, nickel-titanium, and beta-titanium orthodontic archwires were investigated. Brackets and wire were tested with tip angulations of 0 degrees and 10 degrees. Friction testing was done with the Emic DL 10000 testing machine (São José do Rio Preto, PR, Brazil), and the wires were pulled from the slot brackets with a speed of 0.5 cm/min for 2 minutes. The ligation force between the bracket and the wire was 200 g. According to the data obtained, the brackets had frictional force values that were statistically significant in this progressive order: stainless steel bracket, ceramic bracket with a metal reinforced slot, and traditional ceramic bracket with a ceramic slot. The beta-titanium wire showed the highest statistically significant frictional force value, followed by the nickel-titanium and the stainless steel archwires, in decreasing order. The frictional force values were directly proportional to the angulation increase between the bracket and the wire.

Frictional resistance in orthodontic brackets with repeated use

This study measured and compared the level of frictional resistance generated with a nonrepeated and repeated experimental design to evaluate whether the wear in the bracket slot will influence frictional resistance. Both 0.018 and 0.022 inch slot size edgewise brackets were tested in a specially designed apparatus. The frictional resistance was measured on an Instron Universal Testing Machine. A repeated measures ANOVA was used to determine differences among the 10 individual bracket wire specimens for each combination to study the influence of wear on static and kinetic frictional force. A paired t test (two-tail) procedure was used to compare the static and kinetic frictional forces in the nonrepeated and repeated study for each bracket slot, wire size, and bracket type. The results show that there was a distinct trend for the mean frictional force to be higher with the repeated use of the brackets.

Evaluation of friction during sliding tooth movement in various bracket-arch wire combinations

Frictional forces during simulated sliding tooth movement were measured with a model that was representative of the clinical condition. The model allowed tipping of the tooth until contact was established between the arch wire and diagonally opposite corners of the bracket wings; it also allowed rotation until the wire contacted opposite corners of the ligature tie, or the buccal shield with self-ligating brackets, and the base of the slot. Conventional and self-ligating stainless steel brackets as well as conventional ceramic brackets, and ceramic brackets with a stainless steel slot, all with 0.022 inch bracket slot, were tested with 0.019 x 0.025 inch arch wires of stainless steel, nickel titanium, and beta titanium. Each of the 12 bracket-arch wire combinations was tested 10 times. No significant interaction was detected between brackets and arch wires (P = .89), but the bracket and arch wire effects were significant (P < .001). The pairwise differences between conventional and self-ligating stainless steel brackets and ceramic brackets with stainless steel slot were not significant. However, the conventional ceramic brackets generated significantly higher friction than the other brackets tested. Beta titanium arch wires produced higher frictional forces than nickel titanium arch wires, but no significant differences were found between each of the two and stainless steel arch wires. Attempts to identify differences in surface scratches of the arch wires produced by the different brackets were unsuccessful.

Comparison of frictional resistance in titanium and stainless steel brackets

This study measures and compares the level of frictional resistance generated between titanium and stainless steel brackets. Both 0.018 and 0.022 inch slot size edgewise brackets were tested with different sized rectangular stainless steel wires in a specially designed apparatus. The frictional resistance was measured on Instron Universal testing machine (Instron Corp, Canton, Mass) with a 10 pound load cell. The specimen population was composed of 180 brackets and 180 wire specimens. A completely randomized design (one way) ANOVA was used to test for significant differences among the three bracket/wire types in the 0.018 and 0.022 inch slot sizes. This was followed by the Student Newman Keuls Multiple Comparison of means ranking at P < .05 to determine differences between the different groups. The titanium brackets showed lower static and kinetic frictional force as the wire size increased, whereas stainless steel brackets showed higher static and kinetic frictional force as the wire size increased.

An investigation into the behavioural characteristics of orthodontic elastomeric modules

The object of the study was to investigate the behavioural characteristics of orthodontic elastomeric modules with regard to their effect on frictional resistance and their failure load forces, and involved the use of an experimental laboratory-based study. Six cohorts were assembled employing five types of module and two bracket types. Straight lengths of 0.018 x 0.025-inch stainless steel were pulled through the ligated brackets and frictional resistance was measured using an Instron universal testing machine. Recordings were repeated over a 4-week period, during which time the cohorts were placed in a simulated oral environment. Failure load forces of new and used modules were also recorded, and frictional resistance and failure load forces. Analysis of variance revealed that the Minitwin cohort exhibited significantly higher frictional resistance and that the clear modules demonstrated the lowest levels of friction. Time soaked in a simulated oral environment had a variable effect on frictional resistance. A wide range of failure load forces was seen for the five types of module and all types showed a reduction in failure load force following their soaking in the simulated oral environment. There was variation in performance of the different modules both in friction testing and failure load testing.

A comparison of self-ligating and conventional orthodontic bracket systems

This ex-vivo study compared the static frictional resistance of three self-ligating brackets with a conventional steel-ligated Ultratrimm bracket. The effects of archwire size (0.020, 0.019 x 0.025 and 0.021 x 0.025-inch), bracket/archwire angulation (0, 5 and 10 degrees) and the presence of unstimulated human saliva were investigated. The study demonstrated that both increases in wire size and bracket/archwire angulation resulted in increased static frictional resistance for all bracket types tested, with the presence of saliva having an inconsistent effect. Mobil-Lock Variable-Slot had the least friction for all wires for 0 degree angulation. However, with the introduction of angulation, the values were comparable to those of the other brackets. Activa brackets had the second lowest frictional resistance, although high values were found with 0.019 x 0.025-inch wires. SPEED brackets demonstrated low forces with round wires, although with rectangular wires or in the presence of angulation, friction was greatly increased. Ultratrimm brackets produced large individual variation, confirming the difficulty in standardizing ligation force, although under certain conditions, significantly larger frictional forces were observed. In conclusion, self-ligating brackets showed reduced frictional resistance in comparison to steel ligated brackets only under certain conditions.

Friction between different wire-bracket configurations and materials

Friction opposes tooth motion whenever sliding mechanics is employed. Understanding what friction is and how to manage it is of paramount importance to the successful practitioner. In this article, the coefficients of friction are summarized between different arch wire-bracket couples as a function of material, geometric, and external parameters. From this vantage point, friction can then be evaluated within the context of other factors that affect sliding-binding and notching.

Frictional resistances in stainless steel bracket-wire combinations with effects of vertical deflections

This research evaluated the effects of different bracket-wire combinations and second-order deflections on kinetic friction. Thirteen different brackets, six with 0.018 x 0.025 inch slots and seven with 0.022 x 0.028-inch slots were evaluated with six different sizes and shapes of stainless steel orthodontic wire, i.e., 0.016, 0.016 x 0.022, 0.017 x 0.025, 0.018, 0.018 x 0.025 and 0.019 x 0.026 inch for four second order deflections of 0.00, 0.25, 0.50, and 0.75 mm. The wires were ligated into the brackets with elastomeric modules. Bracket movement was implemented by means of an Instron universal testing instrument (RMO, Denver, Colo.), and frictional forces were measured by a tension load cell and recorded on an X-Y recorder (Hewlett-Packard, Anaheim, Calif.). Second-order deflection was created by a specially designed and machined testing apparatus that allowed two alternate pairs of the four total brackets to be offset in increments of 0.25 mm. The kinetic frictional force increased for every bracket-wire combination tested as the second-order deflection increased. Friction also increased with an increase in wire size, whereas rectangular wires produced greater friction than round wires. Bracket designs that limited the force of ligation on the wire generated less friction at low second-order deflections (0.00 and 0.25 mm).

A study of force application, amount of retarding force, and bracket width in sliding mechanics

We investigated the relationship of the retraction force to the location of force application, retarding force and bracket width during simulated sliding tooth movement along an arch wire. Point 1 for retraction was located at the center of the bracket, and points 2 and 3 were at 4.0 mm and 6.0 mm from the bracket slot, respectively. Weights of 100 gm, 200 gm, and 400 gm were suspended at 9.0 mm from the bracket slot as the point of simulated center of resistance. Stainless steel standard edgewise wide, medium, and narrow twin brackets were engaged with two elastomeric ligatures on a stainless steel wire (0.016 x 0.016 inch). The bracket was retracted at the rate of 0.1 mm per second for a distance of 2.0 mm. Measurements were repeated six times, and the results were compared with multiple ANOVA tests. For all brackets, with an increase of the retarding weight, the mean retraction force at points 1 and 2 increased but decreased at point 3. The mean retraction force at point 1 for the narrow twin bracket was significantly (p < 0.05) higher than that for the wide twin bracket at all retarding force levels. However, the mean retraction force at points 2 and 3 for the narrow twin bracket was significantly (p < 0.05) lower than for the wide twin bracket at all retarding force levels. These findings indicated that the point of force application, the resistance force of a tooth, and the width of the bracket are crucial in consideration of the tipping moments on the bracket.

The effect of artificial saliva on the frictional forces between orthodontic brackets and archwires

The effect of artificial saliva on the static and kinetic frictional forces of stainless steel (Dentaurum) and polycrystalline ceramic (Transcend) brackets in combination with 0.018-inch round and 0.019 x 0.025-inch Edgewise archwire sizes and stainless steel, nickel-titanium and beta-titanium archwire materials, under a constant ligature force were investigated. In all cases, artificial saliva had the effect of increasing the frictional force when compared with the dry state.

Relative kinetic frictional forces between sintered stainless steel brackets and orthodontic wires

The level of kinetic frictional forces generated during in vitro translation at the bracket-wire interface were measured for two sintered stainless steel brackets as a function of two slot sizes, four wire alloys, and five to eight wire sizes. The two types of sintered stainless steel brackets were tested in both 0.018-inch and 0.022-inch slots. Wires of four different alloy types, stainless steel (SS), cobalt chromium (Co-Cr), nickel-titanium (Ni-Ti), and beta-titanium (beta-Ti), were tested. There were five wire sizes for the 0.018-inch slot and eight wire sizes for the 0.022-inch slot. The wires were ligated into the brackets with elastomeric ligatures. Bracket movement along the wire was implemented by means of a mechanical testing instrument, and time dependent frictional forces were measured by a load cell and plotted on an X-Y recorder. For most wire sizes, lower frictional forces were generated with the SS of Co-Cr wires than with the beta-Ti or Ni-Ti wires. Increase in wire size generally resulted in increased bracket-wire friction. There were no significant differences between manufacturer for the sintered stainless steel brackets. The levels of frictional force in 0.018-inch brackets ranged from a low of 46 gm with 0.016-inch Co-Cr wire to a high of 157 gm with 0.016 x 0.025-inch beta-Ti wire. In comparing the data from a previous study by Kapila et al. 1990 performed at OUHSC with the same apparatus, the friction of sintered stainless steel brackets was approximately 40% to 45% less than the friction of the conventional stainless steel brackets.

A study of frictional forces between orthodontic brackets and archwires

The differences in magnitude of static and kinetic frictional forces generated by 0.022 x 0.030-inch stainless steel (Dentaurum) and polycrystalline ceramic (Transcend) brackets in combination with archwires of different sizes (0.018 inch and 0.019 x 0.025 inch) and materials (stainless steel, nickel-titanium, and beta-titanium) at a constant ligature force were investigated. A friction-testing assembly using the Instron machine was used. In all cases, the static frictional force was greater than the kinetic frictional force. There were no significant differences in the frictional forces generated by stainless steel and polycrystalline ceramic brackets. Beta-titanium archwires produced greater frictional forces than the other two materials. Increasing the archwire diameter increased the frictional force.