Comparison of ion release from new and recycled orthodontic brackets

Quantitative and qualitative analysis of metallic ion release of orthodontic brackets in three different pH conditions - An invitro study

Background

Fluoridated mouth rinses improve anti-cariogenic environment but decrease oral pH below critical value, affecting orthodontic bracket surface topography and causing corrosive changes over prolonged use. This invitro study aimed to quantitatively and qualitatively assess the surface topography and metallic ion release of the stainless steel (SS) brackets at varying acidic and alkaline pH.

Materials and methods

Forty unused SS brackets were divided into four groups (Group A, B, C, D) and immersed for 48- hours in solutions of artificial saliva and sodium fluoride (0.2 %) mouth rinse at varying pH of 5.5,6.7,7 and 8. The surface morphologic changes were analyzed under scanning electron microscope (SEM) at 50×, 150×, and 500× magnification. The changes in slot area were scored using the customized scale. The Energy Dispersive Xray Spectroscopy Analysis (EDAX) was used to estimate the probed elements' atomic and weight percentage.

Results

The mean score of the scale was 3.4 for the brackets immersed in the acidic solution which was statistically significant (p = 0.00)and for alkaline and neutral solutions (p = 0.00). Chromium was found to be significantly higher in the alkaline solution (p = 0.016) followed by the neutral solution. Carbon was found excess in acidic solution than the neutral and alkaline solution.

Conclusion

Quantitative and qualitative analysis of the ion release in stainless steel brackets using SEM and EDAX revealed the corrosive effect of fluoride ion causing maximum surface changes in acidic medium and chromium release in alkaline pH.

In vitro wearing away of orthodontic brackets and wires in different conditions: A review

Introduction

The release of metallic ions from orthodontic brackets and wires typically depends on their quality (chemical composition) and the medium to which they are exposed, e.g., acidic, alkaline, substances with a high fluoride concentration, etc. This review examines corrosion and wear of orthodontic brackets, wires, and arches exposed to different media, including: beverages (juices), mouthwashes and artificial saliva among others, and the possible health effects resulting from the release of metallic ions under various conditions.

Objective

This review aims to determine the exposure conditions that cause the most wear on orthodontic devices, as well as the possible health effects that can be caused by the release of metallic ions under various conditions.

Sources

A search was carried out in the Scopus database, for articles related to oral media that can corrode brackets and wires. The initial research resulted in 8,127 documents, after applying inclusion and exclusion criteria, 76 articles remained.

Conclusion

Stainless steel, which is commonly used in orthodontic devices, is the material that suffers the most wear. It was also found that acidic pH, alcohols, fluorides, and chlorides worsen orthodontic material corrosion. Further, nickel released from brackets and wires can cause allergic reactions and gingival overgrowth into patients.

Metal Release and Surface Degradation of Fixed Orthodontic Appliances during the Dental Levelling and Aligning Phase: A 12-Week Study

The purpose of the present study is twofold: (i) to assess the salivary nickel, chromium, and iron concentrations and (ii) to characterize the surface microstructure of the typical commercially available Ni-containing metallic appliances during the first 12-week orthodontic treatment period. A total of 85 unstimulated saliva samples were collected from patients before treatment, after 2 days, and after 1, 4, and 12 weeks. Salivary ion concentrations were determined by inductively coupled plasma optical emission spectroscopy, and data were analyzed with the Statistical Package for Social Sciences (IBM SPSS) software. The recorded mean metal concentrations were in the ranges of 132–175 µg/L for Ni, 171–192 µg/L for Cr, and 826–1023 µg/L for Fe. No statistically significant variations were observed between the different study times, and the null hypothesis (the concentrations of metallic ions in patients’ saliva did not significantly change after the placement of the orthodontic appliances) was accepted (p > 0.05). Mean salivary metallic ions were below toxic levels, and no adverse clinical reactions were registered. The intraoral surface degradation of the fixed components was corroborated by optical microscopy, scanning electron microscopy, and energy dispersive spectrometry. Microstructural analysis after complete orthodontic procedure confirmed different corrosion types, from pitting to biocorrosion.

Residual Adhesive Removal Methods for Rebonding of Debonded Orthodontic Metal Brackets: Systematic Review and Meta-Analysis

Debonding of orthodontic brackets is a common occurrence during orthodontic treatment. Therefore, the best option for treating debonded brackets should be indicated. This study aimed to evaluate the bond strength of rebonded brackets after different residual adhesive removal methods. This systematic review and meta-analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Web of Science, The Cochrane Library, SciELO, Scopus, LILACS, IBECS, and BVS databases were screened up to December 2020. Bond strength comparisons were made considering the method used for removing the residual adhesive on the bracket base. A total of 12 studies were included for the meta-analysis. Four different adhesive removal methods were identified: sandblasting, laser, mechanical grinding, and direct flame. When compared with new orthodontic metallic brackets, bond strength of debonded brackets after air abrasion (p = 0.006), mechanical grinding (p = 0.007), and direct flame (p < 0.001) was significantly lower. The use of an erbium-doped yttrium aluminum garnet (Er:YAG) laser showed similar shear bond strength (SBS) values when compared with those of new orthodontic brackets (p = 0.71). The Er:YAG laser could be considered an optimal method for promoting the bond of debonded orthodontic brackets. Direct flame, mechanical grinding, or sandblasting are also suitable, obtaining clinically acceptable bond strength values.

Exposure to the oral environment enhances the corrosion of metal orthodontic appliances caused by fluoride-containing products: Cytotoxicity, metal ion release, and surface roughness

INTRODUCTION

This study aimed to evaluate the metal ion release, cytotoxicity, and surface roughness of clinically used metal orthodontic appliances after immersion in different fluoride product solutions compared with those of new appliances.

METHODS

Used fixed appliances were debonded from 36 patients after their treatment was done. New appliances were as-received. Each used and new group comprised 36 sets of 20 brackets and 4 tubes that were divided into 3 groups by archwire type; stainless steel, nickel-titanium, and beta-titanium. The samples in each group were divided into 3 subgroups and immersed in solutions of fluoride toothpaste, 1.23% acidulated phosphate fluoride, or artificial saliva without fluoride as a control group. The immersion times were estimated from the recommended time for using each fluoride product for 3 months. The samples were then immersed in Dulbecco's Modified Eagle's Medium for 7 days. The cytotoxicity test was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay using primary gingival fibroblasts. Chromium, nickel, and iron ion release were detected using inductively coupled plasma mass spectroscopy. The surface roughness of the brackets and wires was measured by a scanning electron microscope and a noncontact optical 3-dimensional surface characterization and roughness measuring device. The data were analyzed using the paired t test and 2-way analysis of variance.

RESULTS

Used brackets demonstrated a significantly higher ion release, surface roughness, and cytotoxicity than the new brackets. Acidulated phosphate fluoride significantly increased the ion release and surface roughness; however, it significantly decreased cell viability, especially in the titanium molybdenum subgroup.

CONCLUSIONS

Used brackets were significantly prone to further corrosion. Acidulated phosphate fluoride gel should not be used in orthodontic patients with fixed metal appliances.

Color heterogeneity and individual color changes in dentin and enamel bleached in the presence of a metallic orthodontic bracket

OBJECTIVE

This in-vitro study evaluated the color changes in enamel and dentin bleached in the presence of an orthodontic bracket, as well as the heterogeneity of the color and contribution of each tissue to the color change (CTCC).

MATERIALS AND METHODS

Enamel-dentin specimens from extracted bovine teeth were bleached before or after bracket removal or maintained without any treatment (control). The colors of the dentin and enamel were measured individually and after recombining these substrates. The changes in the color (ΔE₀₀ ) and whitening index (ΔWID) were estimated by the color difference between the bleached specimens and those of the control. The CTCC was also calculated by recombining the tissues from different treatments. Images of specimens obtained from a stereomicroscope were used to analyze the color homogeneity within each tissue.

RESULTS

The highest values of ΔE₀₀ and ΔWID were observed in the specimens bleached in the absence of a bracket. Bleaching in the presence of a bracket resulted in enamel with a center that was whiter than the periphery. Dentin and enamel presented similar CTCC values.

CONCLUSIONS

Tooth bleaching performed in the presence of a metallic bracket resulted in a reduced bleaching effect and increased color heterogeneity within both tissues.

CLINICAL SIGNIFICANCE

Tooth bleaching before the orthodontic bracket removal reduces the bleaching effect in both dentin and enamel. Moreover, a heterogeneous color of enamel surface can be observed after tooth bleaching in the presence of a nickel-free metallic orthodontic bracket.

Salivary Nickel and Chromium Levels in Orthodontic Patients with and Without Periodontitis: a Preliminary Historical Cohort Study

Many periodontal patients may need orthodontic treatment. Alterations in oral environment particularly the reduction of pH in periodontal patients could affect metal ion release from orthodontic appliances. However, there is no study on metal ion release in periodontal patients. The aim of this preliminary study was to comparatively evaluate, for the first time, salivary levels of nickel and chromium in periodontal patients (versus healthy controls) under orthodontic treatment for 2 months. In this in vivo study, 40 subjects were evaluated. Patient selection and standardization of orthodontic treatment protocols were prospectively designed and performed. Two groups of n = 20 each (control: healthy orthodontic patients, cohort: orthodontic patients with periodontitis) underwent similar protocols of fixed orthodontic treatment for 2 months. After 2 months, salivary nickel and chromium concentrations of the case and cohort groups were measured using inductively coupled plasma mass spectrometry (ICP-MS). The values were compared between the two groups using t test. There were 10 men and 10 women in each group. The mean age of patients was 34.6 ± 3.6 years old. The salivary level of nickel was 338.2 ± 235.5 ng/ml and 182.8 ± 116.5 ng/ml in the cohort and control groups, respectively (P = 0.0118). The salivary level of chromium was 7.4 ± 3.15 ng/ml in the cohort and 6.35 ± 2.39 ng/ml in the control group (P = 0.2214). Salivary level of nickel might be considerably higher in periodontal patients undergoing 2 months of orthodontic treatment compared to orthodontic patients with healthy gingivae.

Effect of radiofrequency electromagnetic fields (RF-EMFS) from mobile phones on nickel release from orthodontic brackets: An in vitro study

BACKGROUND

The worldwide dramatic increase in the use of cell phones has generated great concerns about their potential adverse health effects.

OBJECTIVE

The aim of the present study was to evaluate the effects of radiofrequency electromagnetic fields (RF-EMFs) emitted from mobile phones on the level of nickel release from orthodontic brackets.

METHODS

Twenty stainless steel brackets were divided randomly into experimental and control groups (n=10). Brackets were immersed in artificial saliva at 37°C for 6 months. Experimental group were exposed to GSM 900MHz RF-EMFs emitted from a mobile phone stimulator for 4hours. The specific absorption rate (SAR) was 2.287W/kg. The concentration of nickel in the artificial saliva in both groups was evaluated by using the cold-vapour atomic absorption spectrometry. The Mann-Whitney test was used to assess significant differences in nickel release between the exposed and non-exposed groups.

RESULTS

The mean nickel levels in the exposed and non-exposed groups were 11.95 and 2.89μg/l, respectively. This difference between the concentrations of nickel in the artificial saliva of these groups was statistically significant (P=0.001).

CONCLUSION

Exposure to RF-EMFs emitted from mobile phones can lead to human exposure to higher levels of nickel in saliva in patients with orthodontic appliances. As nickel exposure can lead to allergic reaction in humans and considering this point that about 10-20% of the population can be hypersensitive to nickel, further studies are needed to evaluate the effects of radiofrequency electromagnetic fields (RF-EMFs) emitted from common devices such as mobile phones or Wi-Fi routers on the level of nickel release from orthodontic brackets.

Evaluation of determinants for the nickel release by the standard orthodontic brackets

AIM

The study was aimed to assess the effect of different pH and immersion time on the amount of nickel release from simulated orthodontic appliance of 3M Unitek company.

MATERIAL AND METHOD

Nickel ion release was evaluated after subjecting the brackets to the simulated artificial oral environment. In this study, 90 stainless steel brackets of 3M Unitek Company were tested by immersing them in artificial saliva of pH 4.2, pH 6.5 and pH 7.6 for a time interval of 1hour, 1 week and 1 month (T1 - 1h, T2 - 7 days, T3 - 30 days) respectively. The data was subjected for the one-way ANOVA and the post-hoc test for the statistical comparison.

RESULTS

Means of 2.99±0.77, 9.53±4.26 and 12.65±2 .52 ppb (parts per billion by volume) of nickel were released for 4.2 pH at a time interval of 1hour, 7 days and 1 month respectively. Means of 5.37±2.26, 10.94±1.51 and 16.92±1.69 ppb of nickel were released for 6.5 pH at a time interval of 1hour, 7 days and 1 month respectively. A mean of 2.13±0.92, 0.74±0.54 and 18.83±1.02 ppb of nickel was released for 7.6 pH at a time interval of 1 hr, 7 days and 1 month respectively.

CONCLUSION

pH of the artificial saliva significantly affected the amount of nickel release. Acidic pH was found to increase the amount of nickel release in the artificial saliva. Time duration of bracket immersion significantly affected the amount of nickel release.

Assessment of Ions released from Three Types of Orthodontic Brackets immersed in Different Mouthwashes: An in vitro Study

AIM

Herbs are used widely in medicine. The purpose of the present study was to assess the ion release from gold-plated orthodontic bracket compared with other stainless steel brackets, and based on the findings of the study, the orthodontists can choose the most biocompatible brackets and mouthwashes useful in the clinical practice.

MATERIALS AND METHODS

A total of 150 orthodontic brackets from Orthotechnology™ Company, USA (50 stainless steel one-piece brackets, 50 stainless steel two-piece brackets, and 50 gold brackets) were immersed in four mouthwashes in addition to distilled water. Ten of each type of brackets in every media were immersed under 37°C for 45 days. Ions released in these mouthwashes were measured, and comparisons among different bracket types and among various mouthwashes were done by one-way analysis of variance (ANOVA) and then with Games-Howell tests.

RESULTS

Increased amounts of ions released in herbal mouth-washes were recorded in gold and two-piece brackets in comparison with one-piece stainless steel brackets.

CONCLUSION

Herbal mouthwashes must be used with caution as they showed an increased amount of ions released in comparison with chlorhexidine. One-piece stainless steel bracket system is the most compatible bracket type, as they released the least amount of ions.

CLINICAL SIGNIFICANCE

One-piece stainless steel brackets are better than two-piece brackets in terms of ions released.

Metal release profiles of orthodontic bands, brackets, and wires: an in vitro study

AIM

The present study evaluated the temporal release of Co Cr, Mn, and Ni from the components of a typical orthodontic appliance during simulated orthodontic treatment.

MATERIALS AND METHODS

Several commercially available types of bands, brackets, and wires were exposed to an artificial saliva solution for at least 44 days and the metals released were quantified in regular intervals using inductively coupled plasma quadrupole mass spectrometry (ICP-MS, Elan DRC+, Perkin Elmer, USA). Corrosion products encountered on some products were investigated by a scanning electron microscope equipped with an energy dispersive X-ray microanalyzer (EDX).

RESULTS

Bands released the largest quantities of Co, Cr, Mn, and Ni, followed by brackets and wires. Three different temporal metal release profiles were observed: (1) constant, though not necessarily linear release, (2) saturation (metal release stopped after a certain time), and (3) an intermediate release profile that showed signs of saturation without reaching saturation. These temporal metal liberation profiles were found to be strongly dependent on the individual test pieces. The corrosion products which developed on some of the bands after a 6-month immersion in artificial saliva and the different metal release profiles of the investigated bands were traced back to different attachments welded onto the bands.

CONCLUSION

The use of constant release rates will clearly underestimate metal intake by the patient during the first couple of days and overestimate exposure during the remainder of the treatment which is usually several months long. While our data are consistent with heavy metal release by orthodontic materials at levels well below typical dietary intake, we nevertheless recommend the use of titanium brackets and replacement of the band with a tube in cases of severe Ni or Cr allergy.

A comparative evaluation of ion release from different commercially-available orthodontic mini-implants – an in-vitro study

Background

Titanium alloy mini-implants have become popular in recent times and have been extensively used and studied. Although corrosion resistance of orthodontic materials has always been of concern, this property has been the least explored. The present study aimed to assess the composition, surface characterisation and corrosion resistance of five commercially available mini-implants by assaying ion release in artificial saliva.

Methods

Ten mini-implants each from five companies were obtained: Group 1 – AbsoAnchor (Dentos Inc, South Korea); Group 2 – Microimplant Anchorage System (MIA, Biomaterials Korea); Group 3 – The Orthodontic Mini Anchorage System (TOMAS, Dentaurum, Germany); Group 4 – mini-implants (Denticon, Maharashtra, India); Group 5 – orthodontic mini-implants (J.J.Orthodontics, Kerala, India). One mini-implant from each group was subjected to characterisation and surface microstructure analysis using Energy Dispersive Atomic Spectrometry (EDAX) and Scanning Electron Microscope (SEM), respectively. Ten miniimplants were immersed for 30 days in Fusayama-Meyer artificial saliva solution and the release of titanium, aluminium and vanadium ions was detected with Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES). The Kruskal-Wallis test was used for multi-variate analysis. In order to determine the significant differences between the groups on independent samples, the Mann-Whitney U test (bi-variate analysis) was applied.

Results and conclusion

All groups showed machining defects but surface pitting after immersion was mostly evident in Group 4. Although the composition of all the implants was comparable, there was a statistically significant difference in the Ti, Al and V release between Group 4 – the group with maximum release – and Group 2, the group with least release.

Release of nickel and chromium ions in the saliva of patients with fixed orthodontic appliance: An in-vivo study

INTRODUCTION

Various components of fixed orthodontic appliances are continuously interacting with saliva and other fluids in the mouth releasing various metal ions including nickel and chromium that can cause damaging effects if their concentration exceeds above the toxic dose.

AIM

To determine and compare the level of nickel and chromium in the saliva of patients undergoing fixed orthodontic treatment at different time periods.

MATERIALS AND METHODS

The sample of saliva of 13 patients was taken at different time periods that is: Group 1 (before appliance placement), Group II, III, and IV (after 1-week, 1-month, and 3 months of appliance placement respectively). The fixed appliance comprised of brackets, bands, buccal tubes, lingual sheath, transpalatal arch and wires composed of Ni-Ti and stainless steel. The level of ions was determined using graphite furnace atomic absorption spectro-photometry. The data thus obtained were statistically analyzed using SPSS Statistical Analysis Software (Version 15.0).

RESULTS

Level of nickel and chromium in saliva was highest in Group II and lowest in Groups I for both the ions. On comparison among different Groups, it was statistically significant for all the groups (<0.001) except between Group III and Group IV.

CONCLUSION

The release of nickel and chromium was maximum at 1-week and then the level gradually declined. These values were well below the toxic dose of these ions. The results should be viewed with caution in subjects with Ni hypersensitivity.

Comparative evaluation of nickel discharge from brackets in artificial saliva at different time intervals

Objectives:

To determine and compare the potential difference of nickel release from three different orthodontic brackets, in different artificial pH, in different time intervals.

Materials and Methods:

Twenty-seven samples of three different orthodontic brackets were selected and grouped as 1, 2, and 3. Each group was divided into three subgroups depending on the type of orthodontic brackets, salivary pH and the time interval. The Nickel release from each subgroup were analyzed by using inductively coupled plasma-Atomic Emission Spectrophotometer (Perkin Elmer, Optima 2100 DV, USA) model. Quantitative analysis of nickel was performed three times, and the mean value was used as result. ANOVA (F-test) was used to test the significant difference among the groups at 0.05 level of significance (P < 0.05). The descriptive method of statistics was used to calculate the mean, standard deviation, minimum and maximum. SPSS 18 software ((SPSS.Ltd, Quarry bay, Hong Kong, PASW-statistics 18) was used to analyze the study.

Result:

The analysis shows a significant difference between three groups. The study shows that the nickel releases from the recycled stainless steel brackets have the highest at all 4.2 pH except in 120 h.

Conclusion:

The study result shows that the nickel release from the recycled stainless steel brackets is highest. Metal slot ceramic bracket release significantly less nickel. So, recycled stainless steel brackets should not be used for nickel allergic patients. Metal slot ceramic brackets are advisable.

Estimation of Release of Nickel and Chromium by Indian Made Orthodontic Appliance in Saliva

INTRODUCTION

With increasing use of Indian made orthodontic materials, need was felt to know nickel and chromium release from these material.

MATERIALS AND METHODS

This study was conducted on simulated appliances consisting of brackets (022″Roth, Modern orthodontics, Ludhiana, India), from second premolar to central incisor, buccal tube and 0.019×0.025- inch SS arch wires secured with SS ligatures. Immersion was done in artificial saliva. Samples were analysed to using Atomic Absorption Photospectrometer (GVC ScientificEquipment Pvt. Ltd Australia) at AES Laboratories (P) Ltd., Noida India on 1(st), 7(th), 14(th) and 28(th) day.

RESULTS

SPSS (ver 17, Inc., Chicago, Illinois, USA) was used toperform the statistical analysis. Descriptive statistics i.e. median and 25 and75 percentiles were used. Peak nickel release was on 7(th) day and subsequently declined over 14(th) and 28(th) day. The peak level of chromium concentration was on 14(th) day, which declined thereafter.

CONCLUSION

Average daily release of nickel and chromium over a period of one month was 97.368 μg/day and 47.664 μg/day respectively. The estimated release rates were approximately 32% and 16% of the reported average daily dietary.

Shear bond strength and morphological analysis of KrF laser-recycled metal brackets

OBJECTIVE

The aim of this study was to compare the effect of a KrF excimer laser versus traditional chairside deboned bracket processing methods of grinding, flaming, and sandblasting on the shear bond strength and morphological change of recycled brackets.

BACKGROUND DATA

Bracket dislodgement happens frequently in orthodontic treatment.

METHODS

The Victory Series bracket with a foil-mesh base and the Mini Sprint bracket with a raised base were chosen in this research. Grind, flame, sandblast, and laser groups acted as the experimental groups, and the new bracket group served as control. The shear bond strengths were determined with an Electroforce test machine and statistically tested by an analysis of variance (ANOVA). Morphological examinations of the recycled bracket bases were conducted with scanning electron microscopy and confocal laser scanning microscopy. Bracket base residue content was analyzed using Raman spectroscopy.

RESULTS

The study showed that adhesive was left on the recycled bracket base processed by grinding and flaming, with significantly decreased shear bond strength (p<0.05). Sandblasting and KrF excimer lasering both thoroughly removed the adhesive. Shear bond strength decreased with sandblasting in the Victory bracket but not in the Mini Sprint bracket. Shear bond strength of KrF-lasered recycled brackets did not differ statistically from that of both kinds of new brackets. The study also showed that KrF excimer laser caused limited damage to the bracket.

CONCLUSIONS

The KrF excimer laser can remove adhesive on the two different bracket bases effectively, causing little damage to the bracket; therefore, it is a superior bracket refurbishing method worth further study.

[Evaluation of the corrosion resistance of orthodontic wires by electrochemical measures and scanning electron microscopy (SEM)]

The objective of this paper is to study the corrosion resistance of orthodontic wires made of different alloys (stainless steel, chrome-cobalt, nickel-titanium and β-titanium) and for the same alloy from different vendors (GAC(®), RMO(®), 3M(®) and ORMCO(®)). Different electrochemical techniques (corrosion potential monitoring as a function of immersion time, current-potential curves, electrochemical impedance spectroscopy (EIS)) were used. The wires' resistance to corrosion was measured and compared with the surface condition, assessed by scanning electron microscopy (SEM). Using the recorded data, a rating system based on the corrosion resistance of orthodontic wires was developed. The comparison of these data with the results of SEM shows that the surface chemical composition plays a primary role in the electrochemical behavior of the orthodontic wires and, unlike surface defects, is a key parameter for the corrosion resistance of the alloy.

In vitro corrosion of metallic orthodontic brackets: influence of artificial saliva with and without fluorides

OBJECTIVE: This in vitro study verified the resistance to corrosion of metallic brackets, evaluating the superficial aspects in scanning electron microscopy (SEM) and the residual components. METHODS: The sample consisted of 17 sets of brackets of four different metallic alloys: Titanium, Cobalt-Chromium, Stainless steel with low nickel concentration and with titanium nitride coating (NiTi). Twelve sets were submitted to corrosion by immersion in 50 ml of artificial saliva (pH 6.5) and four in saliva (pH 6.5) containing fluoride (2 g/l), all at a temperature of 37 ºC and analyzed after 7, 9 and 11 weeks. One was kept as control set. The analysis consisted in qualitative evaluation of the corrosion by the images obtained on the SEM, in semi-quantitative evaluation of chemical composition of the surface residue by SEM-EDS and the amount of ions released in saliva on evaluation of atomic absorption spectrophotometry. RESULTS: The results showed that the pure titanium brackets and the ones with low nickel concentration were superior regarding resistance to corrosion. The cobalt-chromium alloy showed the greatest corrosion. In the presence of fluoride, it was observed greater variation in all alloys, especially in the ones of NiTi coated steel and the ones of cobalt-chromium. CONCLUSION: Although observed corrosion on the SEM, the spectrophotometry showed low ions release in the artificial saliva, however, the presence of fluoride negatively affected the corrosion resistance.

Comparison of metal ion release from different bracket archwire combinations: an in vitro study

AIM

The metal ion released from the orthodontic appliance may cause allergic reactions particularly nickel and chromium ions. Hence, this study was undertaken to determine the amount of nickel, chromium, copper, cobalt and iron ions released from simulated orthodontic appliance made of new archwires and brackets.

MATERIALS AND METHODS

Sixty sets of new archwire, band material, brackets and ligature wires were prepared simulating fixed orthodontic appliance. These sets were divided into four groups of fifteen samples each. Group 1: Stainless steel rectangular archwires. Group 2: Rectangular NiTi archwires. Group 3: Rectangular copper NiTi archwires. Group 4: Rectangular elgiloy archwires. These appliances were immersed in 50 ml of artificial saliva solution and stored in polypropylene bottles in the incubator to simulate oral conditions. After 90 days the solution were tested for nickel, chromium, copper, cobalt and iron ions using atomic absorption spectrophotometer.

RESULTS

Results showed that high levels of nickel ions were released from all four groups, compared to all other ions, followed by release of iron ion levels. There is no significant difference in the levels of all metal ions released in the different groups.

CONCLUSION

The study confirms that the use of newer brackets and newer archwires confirms the negligible release of metal ions from the orthodontic appliance.

CLINICAL SIGNIFICANCE

The measurable amount of metals, released from orthodontic appliances in artificial saliva, was significantly below the average dietary intake and did not reach toxic concentrations.

Reconditioning of self-ligating brackets

OBJECTIVE

To test the null hypothesis that there is no significant difference in the shear bond strength (SBS) and Adhesive Remnant Index (ARI) scores of new vs reconditioned self-ligating brackets.

MATERIALS AND METHODS

One hundred and twenty permanent extracted bovine teeth were embedded in resin blocks. Three different new and reconditioned self-ligating orthodontic brackets (Smart Clip [3M Unitek]; Quick [Forestadent]; and Damon3MX [Ormco]) were tested. Scanning electron microphotographs of the different new (groups 1, 3, and 5) and reconditioned (groups 2, 4, and 6) bracket bases were taken before starting the experiments. Brackets were then bonded to the teeth using an orthodontic adhesive and were then tested in shear mode using an Instron Universal Testing Machine. ARI scores were then recorded. Statistical analysis was performed to determine significant differences in SBS and ARI Scores.

RESULTS

Smart Clip and Damon3MX reconditioned brackets showed significantly lower SBS than did new ones. On the contrary, Quick reconditioned brackets showed significantly higher SBS than did new ones. No significant differences in ARI scores were found after the reconditioning process for the three different brackets tested.

CONCLUSION

The in-office reconditioning procedure alters the SBS of self-ligating brackets, although SBS values still remain clinically acceptable.

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.

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.

Release of metal ions from orthodontic appliances by in vitro studies: a systematic literature review

In the present work, a systematic literature review on release of metal ions from orthodontic appliances under in vitro conditions is described. Detailed and schematic analysis of used materials and applied methods (immersion media, incubation time, temperature, and analytical techniques) is provided. The PubMed search identified 40 studies, among which eight met the selection criteria. One additional study was included in the review. All the authors agreed that the doses of released metal ions were far below the toxic level and the dietary intake. Although the concentrations of metal ions in immersion media greatly differed, the general conclusions were coherent. It must be underlined that the main disadvantage of in vitro tests was that the experimental setup did not reflect in vivo conditions, e.g., the presence of biofilm, which grows on the surface of the materials in oral cavity. The presence and activity of microflora to a large extent is responsible for the process of corrosion, in particular, biodeterioration. The further scheme of in vitro research should incorporate changeable conditions of oral cavity environment (pH, dynamic conditions-saliva flow) and the presence of microbiological flora (microbiological attack) in the experimental design and, first of all, the real proportions of appliance elements.

Metal ion release from fixed orthodontic appliances--an in vivo study

The aim of this study was to test the hypothesis that there is no difference in salivary metal ion content between subjects with fixed orthodontic appliances and their same-gender sister or brother without any orthodontic appliance. This retrospective study was carried out on 28 subjects (16 females and 12 males) who had undergone fixed orthodontic therapy for a duration of 12-18 months. In order to limit the effects of dietary and hygiene habits on salivary metal ion concentration, a same-gender brother or sister (total of 28 subjects) was selected as a control. Approximately 5 ml of saliva was collected from each subject, and the samples were analysed using an atomic absorption spectrophotometer. The detection limit of the method for sample solutions was 1 ng/ml. Since some variables were not normally distributed, non-parametric tests (Mann-Whitney U and Wilcoxon W) were used for statistical analysis. The mean salivary nickel (Ni) content in subjects with and without a fixed orthodontic appliance was 18.5 ± 13.1 and 11.9 ± 11.4 ng/ml, respectively. A statistically significant difference (P < 0.035) was found between the two groups. The mean salivary chromium (Cr) ion level recorded was 2.6 ± 1.6 ng/ml in the study group and 2.2 ± 1.6 ng/ml in the control group. The difference, however, was statistically insignificant. Within the limits of this in vivo study, it can be concluded that the presence of fixed orthodontic appliances leads to an increased concentration of metal ions in salivary secretions.

Nickel release from new conventional stainless steel, recycled, and nickel-free orthodontic brackets: An in vitro study

INTRODUCTION

The aim of this study was to compare the nickel released from 3 kinds of orthodontic brackets: new conventional stainless steel, recycled stainless steel, and nickel-free brackets.

METHODS

This in-vitro study was performed by using a classic batch procedure. Samples were immersed in artificial saliva at various acidities (pH 4.2, 6.5, 7.6) over an extended time interval (0.25, 1, 24, 48, and 120 hours). The amount of nickel released was determined by using an atomic absorption spectrophotometer and an inductively coupled plasma atomic emission spectrometer. Statistical analysis included a linear regression model for repeated measures, with calculation of Huber White robust standard errors to account for intrabracket correlation of data. For post-hoc comparisons, the Bonferroni correction was applied.

RESULTS

The recycled brackets released the most nickel (74.02 +/- 170.29 microg per gram); the new stainless steel brackets released 7.14 +/- 20.83 microg per gram. The nickel-free brackets released the least nickel (0.03 +/- 0.06 microg per gram). All the differences among the groups were statistically significant (P = 0.000).

CONCLUSIONS

Reconditioned brackets released the most nickel. Moreover, the highest nickel release was recorded in the 2 experiments performed at pH 4.2; it was lower at pH 6.5 and 7.6. Conversely, no relevant differences were observed overall between the maxillary and mandibular arches.

Biodegradação de braquetes ortodônticos: análise por microscopia eletrônica de varredura

OBJETIVO: analisar, por meio de microscopia eletrônica de varredura, as alterações químicas e estruturais de braquetes metálicos submetidos a um processo de biodegradação in vitro. MÉTODOS: a amostra foi dividida em dois grupos, de acordo com a marca comercial dos acessórios - Grupo A = Dyna-Lock, 3M/Unitek (AISI 303) e Grupo B = LG Edgewise Standard, American Orthodontics (AISI 316L). Os corpos de prova, aparelhos ortodônticos simulados, permaneceram imersos em solução salina (0,05%) por um período de 60 dias, a 37ºC, sob agitação. As alterações decorrentes da exposição dos acessórios à solução salina foram investigadas através da observação com microscópio eletrônico de varredura (MEV) e análise da composição química (EDX), realizadas antes e após o período de imersão (T0 e T5, respectivamente). RESULTADOS: em T5, houve formação de produtos de corrosão sobre a superfície dos braquetes, especialmente no Grupo A, além disso, houve alterações na composição da liga metálica dos braquetes de ambos os grupos, sendo que, no Grupo A, houve redução dos íons ferro e cromo e, no Grupo B, redução de íons cromo. CONCLUSÃO: os acessórios do Grupo A apresentaram-se menos resistentes à biodegradação in vitro, o que poderia estar associado ao tipo de aço utilizado em sua fabricação (AISI 303).

An in vitro comparison of nickel and chromium release from brackets

This study aimed at comparing amounts of nickel (Ni) and chromium (Cr) released from brackets from different manufacturers in simulated oral environments. 280 brackets were equally divided into 7 groups according to manufacturer. 6 groups of brackets were stainless steel, and 1 group of brackets was made of a cobalt-chromium alloy with low Ni content (0.5%). International standard ISO 10271/2001 was applied to provide test methods. Each bracket was immersed in 0.5 ml of synthetic saliva (SS) or artificial plaque fluid (PF) over a period of 28 days at 37 degrees Celsius. Solutions were replaced every 7 days, and were analyzed by spectrometry. The Kruskal-Wallis test was applied. Amounts of Ni release in SS (microg L(-1) per week) varied between groups from 'bellow detection limits' to 694, and from 49 to 5,948.5 in PF. The group of brackets made of cobalt-chromium alloy, with the least nickel content, did not release the least amounts of Ni. Amounts of Cr detected in SS and in PF (microg L(-1) per week) were from 1 to 10.4 and from 50.5 to 8,225, respectively. It was therefore concluded that brackets from different manufacturers present different corrosion behavior. Further studies are necessary to determine clinical implications of the findings.

Chromium release from new stainless steel, recycled and nickel-free orthodontic brackets

OBJECTIVE

To test the hypothesis that there is no difference in the amounts of chromium released from new stainless steel brackets, recycled stainless steel brackets, and nickel-free (Ni-free) orthodontic brackets.

MATERIALS AND METHODS

This in vitro study was performed using a classic batch procedure by immersion of the samples in artificial saliva at various acidities (pH 4.2, 6.5, and 7.6) over an extended time interval (t(1) = 0.25 h, t(2) = 1 h, t(3) = 24 h, t(4) = 48 h, t(5) = 120 h). The amount of chromium release was determined using an atomic absorption spectrophotometer and an inductively coupled plasma atomic emission spectrometer. Statistical analysis included a linear regression model for repeated measures, with calculation of Huber-White robust standard errors to account for intrabracket correlation of data. For post hoc comparisons the Bonferroni correction was applied.

RESULTS

The greatest amount of chromium was released from new stainless steel brackets (0.52 +/- 1.083 microg/g), whereas the recycled brackets released 0.27 +/- 0.38 microg/g. The smallest release was measured with Ni-free brackets (0.21 +/- 0.51 microg/g). The difference between recycled brackets and Ni-free brackets was not statistically significant (P = .13). For all brackets, the greatest release (P = .000) was measured at pH 4.2, and a significant increase was reported between all time intervals (P < .002).

CONCLUSION

The hypothesis is rejected, but the amount of chromium released in all test solutions was well below the daily dietary intake level.

Type of archwire and level of acidity: effects on the release of metal ions from orthodontic appliances

OBJECTIVE

To examine the effects of three different parameters-pH value, type of archwire, and length of immersion-on release of metal ions from orthodontic appliances.

MATERIALS AND METHODS

Simulated fixed orthodontic appliances that corresponded to one-half of the maxillary arch were immersed in artificial saliva of different pH values (6.75 +/- 0.15 and 3.5 +/- 0.15) during a 28-day period. Three types of archwires were used: stainless steel (SS), nickel-titanium (NiTi), and thermo NiTi. The quantity of metal ions was determined with the use of a high-resolution mass spectrophotometer (HR-ICP/MS).

RESULTS

The release of six different metal ions was observed: titanium (Ti), chromium (Cr), nickel (Ni), iron (Fe), copper (Cu), and zinc (Zn). Repeated measures statistical analysis of variance (ANOVA) was used. Results showed that (1) the appliances released measurable quantities of all ions examined; (2) the change in pH had a very strong effect (up to 100-fold) on the release of ions; and (3) the release of ions was dependent on wire composition, but it was not proportional to the content of metal in the wire. The largest number of ions was released during the first week of appliance immersion.

CONCLUSION

Levels of released ions are sufficient to cause delayed allergic reactions. This must be taken into account when type of archwire is selected, especially in patients with hypersensitivity or compromised oral hygiene.

Biocompatibilidade dos materiais em Ortodontia: mito ou realidade?

O objetivo deste trabalho é apresentar uma revisão sobre os conceitos relacionados à biocompatibilidade dos materiais empregados em Ortodontia. Fatos relacionados às reações de hipersensibilidade aos diversos materiais ortodônticos são discutidos, sendo apresentadas as condutas recomendáveis nestas situações.

Effect of bracket base conditioning

INTRODUCTION

The aim of this study was to compare the effect of a silicoating system, the influence of sandblasting, and the effect of a silane-coupling agent after sandblasting on the shear bond strength of stainless steel foil-mesh brackets. To simulate the oral environment, all specimens were thermocycled (6000 times at 5 degrees C and 55 degrees C) in a mastication device before testing.

METHODS

Four bracket groups were tested: group 1 consisted of 20 metal brackets that were sandblasted on the base; group 2 contained 20 brackets that were sandblasted, and a silane-coupling agent was applied; in group 3, the surface of the base of 20 metal brackets was treated by using a tribochemical system; and group 4 was the control group. The brackets were bonded with a light-curing adhesive to extracted third molars, and the shear bond strength and the adhesive remnant index score were determined. The brackets of group 1 were reconditioned after debonding with sandblasting and tested again (group 5).

RESULTS

Sandblasting and tribochemical treatment of brackets improved the shear bond strength of stainless steel brackets. Combined sandblasting and silane-coupling treatment offers no benefit of increased in-vitro strength.

CONCLUSIONS

The bond of resins to tribochemically silicoated stainless steel brackets seems to be sufficient to strengthen the bond between the adhesive and the metal bracket. This treatment is mainly indicated for low-compliance patients or teeth that are difficult to bond.

Nickel concentration in the saliva of patients with nickel-titanium orthodontic appliances

INTRODUCTION

The purpose of this study was to examine whether nickel-titanium (Ni-Ti) archwires cause an increase of nickel concentration in the saliva of 18 orthodontic patients to estimate the possible risk of these archwires in patients who have nickel hypersensitivity.

METHODS

Saliva samples were collected before orthodontic treatment, after placement of the bands and brackets, 2 weeks later and before placing the Ni-Ti archwires, immediately after placing the Ni-Ti archwires, 4 weeks after placing the wires, and 8 weeks after placing the wires.

RESULTS

By using mass spectrometry, no statistically significant differences were found in the nickel concentrations in the samples taken without appliances, in those obtained 2 weeks after placement of the bands and brackets, and 4 and 8 weeks after placement of the archwires. Samples taken immediately after placement of the bands and brackets and the Ni-Ti archwires showed slight but significant increases in nickel concentration of 78 and 56 microg per liter, respectively, compared with the pretreatment value of 34 microg per liter.

CONCLUSIONS

Nickel leaching occurred after placement of the bands and brackets and after placement of the Ni-Ti archwires, associated with an increase of the nickel ion concentration in the patient's saliva. This effect decreased within 10 weeks.

Biodegradação de braquetes ortodônticos: avaliação da liberação iônica in vitro

OBJETIVO: avaliar, in vitro, a biodegradação de aparelhos ortodônticos simulados constituídos de braquetes e fios de aço inoxidável. METODOLOGIA: a amostra foi dividida em 2 grupos, de acordo com a marca dos braquetes usados: grupo A - Dyna-Lock, 3M/Unitek (AISI 303); e grupo B - LG Edgewise Standard, American Orthodontics (AISI 316L). Os corpos-de-prova permaneceram incubados em solução salina (0,05%) a 36ºC, sob agitação por um período de até 60 dias. A análise da liberação iônica foi realizada por meio de espectrofotometria de absorção atômica. O peso em massa dos braquetes também foi medido antes e após o experimento. RESULTADOS: os resultados indicaram que o grupo A apresentou maior liberação de íons ferro, níquel e cromo do que o grupo B. Além disso, os braquetes do grupo A também mostraram perda de massa, considerada outro indicativo de corrosão. CONCLUSÃO: concluiu-se que, nas condições deste experimento, os braquetes do grupo A apresentaram maior biodegradação que os acessórios do grupo B, o que pode estar associado à liga metálica e/ou ao processo de fabricação dos mesmos.

Nickel, chromium and iron levels in the saliva of patients with simulated fixed orthodontic appliances

OBJECTIVE

To assess the in vivo release of nickel, chromium, and iron ions into saliva by different metallic brackets.

MATERIALS AND METHODS

Thirty volunteers wore removable appliances with bonded brackets and were divided according to the brand of brackets: group A, 3M/Unitek (AISI 303); group B, American Orthodontics (AISI 316L); and group C, Dentaurum (AISI 316L). The appliances were worn for 60 days, and saliva samples were collected at the following time points: T1, before placement of the appliance; T2, after 10 minutes; T3, 24 hours; T4, 7 days; T5, 30 days; and T6, 60 days after insertion of the removable appliance. Saliva samples were analyzed for nickel, chromium, and iron by atomic absorption spectrophotometry. Statistical analysis was performed by nonparametric tests (Friedman, Mann-Whitney, Kruskal-Wallis).

RESULTS

Saliva evaluation revealed a large variation in concentration of these ions between individuals. The results also appeared to indicate an increase in nickel and chromium ions immediately after placement of the appliance (T2), but this was statistically significant only for groups B and C. There was no increase in iron levels. A tendency for increases in nickel and chromium concentrations was verified immediately after placement of the appliance, but these values are probably reduced because of biofilm formation regardless of the bracket used.

CONCLUSION

Nickel and chromium ion concentrations increased immediately after placement of the appliance in the mouth for all study groups. There were no significant differences in the nickel, chromium, and iron levels released by the three groups of appliances at all study periods.

Hypersensitivity to conventional and to nickel-free orthodontic brackets

The aim of this study was to evaluate the allergenic potential of orthodontic brackets, comparing the cutaneous sensitivity provoked by metals present in conventional metallic brackets to that provoked by brackets with a low concentration of nickel, known as "nickel-free". A sample was selected from 400 patients undergoing treatment in the orthodontic clinic of the Pontifical Catholic University of Minas Gerais (Belo Horizonte, MG, Brazil), in the period from the beginning of 2002 to the end of 2003. A cutaneous sensitivity patch test containing 5% nickel sulphate was used in 58 patients (30 males and 28 females), aged between 11 and 30, which were using fixed appliances with Morelli® brackets in both arches. In a second phase, 30 days later, a comparative test of cutaneous sensitivity was applied to the whole sample with two types of test specimens, in the form of a disc. Two alloys were tested: discs composed of the alloy used in the construction of conventional brackets and discs composed of a nickel-free alloy. The internal part of the forearm was chosen for testing, and 20 test specimens of each experiment (corresponding to the twenty brackets of a complete fixed appliance) were applied. Of the 58 patients evaluated, 16 patients were sensitive to the patch test with 5% nickel sulphate. Out of these 16 patients, 12 developed an allergic reaction to experiment 1 (test specimen with nickel), while in experiment 2, only 5 patients showed sensitivity to that sample. The McNemar test revealed that the nickel-free test specimens provoked less allergic reaction when compared with the conventional alloy (p = 0.016).

Cytotoxicity of Orthodontic Wire Corroded in Fluoride Solution In Vitro

OBJECTIVE

To investigate the toxicity of fluoride corrosion extracts of stainless steel (SS) and nickel-titanium (NiTi) wires on a human osteosarcoma cell line (U2OS).

MATERIALS AND METHODS

The SS and NiTi wires were corroded by an electrochemical method with the application of three kinds of electrolytes: 0.2% pH 3.5 acidulated phosphate fluoride (NaF) in artificial saliva, and pH 4 and pH 6.75 artificial saliva solutions. The extracts were analyzed for nickel, chromium, and titanium ions by the atomic absorption method. The extracts were diluted with medium to different concentrations (1, 0.1, and 0.01 microL/mL). The cell survival rate was determined by the ability of test cells to cleave the tetrazolium salt to form a formazan dye.

RESULTS

The results were compared using one-way analysis of variance. Differences between the treatment means were analyzed using a Student-Newman-Keuls (SNK) test and were considered significant at P < .05. The release of ionic nickel was different in different extract groups (P < .05). The SS and NiTi wires in the 0.2% pH 3.5 NaF artificial saliva group caused a dose-dependent decrease in the survival rate (P < .05). Survival rates of cells in the groups exposed to extracts of SS and NiTi wires in pH 4 and pH 6.75 artificial saliva solutions showed no statistical differences (P >.05).

CONCLUSIONS

Orthodontic wires in acidulated fluoride saliva solution can cause U2OS cell toxicity.

Comparison of frictional resistance after immersion of metal brackets and orthodontic wires in a fluoride-containing prophylactic agent

INTRODUCTION

In this study, we investigated and compared the levels of frictional resistance between metal brackets and orthodontic wires after immersion in an acidified phosphate fluoride (APF) agent.

METHODS

Three types of mandibular incisor stainless steel metal brackets with beta-titanium alloy wire (TMA), heat-activated nickel-titanium wire (Ni-Ti), and 2 sizes of stainless steel wires (SSW) were immersed in 0.2% APF and pH 6.75 artificial saliva solutions for 24 hours. The study included 480 bracket-wire specimens. The frictional resistance was measured on an EZ-test machine (Shimadazu, Tokyo, Japan) with a 5-N load cell. An Alastik (Quik-Stik Clear, A-1 Alastik, 3M Unitek, Monrovia, Calif) module ligated to the bracket was attached to the crosshead of the machine and pulled at a speed of 10 mm per minute for a distance of 5 mm. A completely randomized 1-way ANOVA was used to test for significant differences among the 3 bracket/wire specimens after immersion in 0.2% APF and pH 6.75 artificial saliva solutions. This was followed by the Student-Newman-Keuls multiple comparison of means ranking at P <.05 to determine differences between the groups.

RESULTS

In the APF-immersed group, the static frictional force was greater than the kinetic frictional force. The frictional forces of the orthodontic wires had statistically significant differences (P <.05) in this progressive order: TMA, Ni-Ti, and SSW. Similar frictional force results were obtained in the pH 6.75 saliva group (P <.05). The frictional force values of the APF group were higher than those of the pH 6.75 saliva group (P <.05).

CONCLUSIONS

This study demonstrates that the frictional forces of orthodontic brackets and wires are influenced by contact with fluoride-containing solutions.