Effect of Elastomeric Module Degradation and Ligation Methods on Kinetic Friction between NiTi or Stainless Steel Wires and Stainless Steel Brackets

Objectives: The reduction of resistance to sliding between the archwire and bracket promotes more seamless tooth movement, leading to a faster and improved orthodontic treatment experience. This research aimed to examine how the degradation of elastomeric modules, different ligation methods, bracket-wire angle, and wire type (nickel titanium, NiTi or stainless-steel, SS) impact the kinetic friction resulting from the interaction between NiTi or SS archwires and SS brackets. Materials and Methods: The current in vitro study was conducted on nine groups, including NiTi and SS archwires with three types of ligations (O-ring, figure of 8, and SS wire ligature) and two bracket-wire angles (0˚ and 10˚). The kinetic friction in each group was measured using a Universal Testing Machine at four time intervals: baseline, day one, week one, and week four. Repeated measures ANOVA, Mauchly test of sphericity followed by the Greenhouse-Geisser test, and relevant post hoc tests were used for statistical analysis (P<0.05). Results: The authors found a decrease in kinetic friction in all types of ligations, which confirmed the effect of time on the degradation of ligation modules. The kinetic friction of figure of 8 ligations was higher than both O-ring and SS wire ligations. No difference was observed between O-ring and SS wire ligations. Furthermore, the bracket-wire angle did not affect friction. Conclusion: The authors suggest that the use of figure of 8 ligations in NiTi and SS wires should be limited due to their high friction and replaced with other types of ligations, if possible.

Influence of receiver bandwidth on MRI artifacts caused by orthodontic brackets composed of different alloys

Purpose

The aim of this in vitro study was to assess the role of bandwidth on the area of magnetic resonance imaging (MRI) artifacts caused by orthodontic appliances composed of different alloys, using different pulse sequences in 1.5 T and 3.0 T magnetic fields.

Materials and Methods

Different phantoms containing orthodontic brackets (ceramic, ceramic bracket with a stainless-steel slot, and stainless steel) were immersed in agar gel and imaged in 1.5 T and 3.0 T MRI scanners. Pairs of gradient-echo (GE), spin-echo (SE), and ultrashort echo time (UTE) pulse sequences were used differing in bandwidth only. The area of artifacts from orthodontic devices was automatically estimated from pixel value thresholds within a region of interest (ROI). Mean values for similar pulse sequences differing in bandwidth were compared at 1.5 T and 3.0 T using analysis of variance.

Results

The comparison of groups revealed a significant inverse association between bandwidth values and artifact areas of the stainless-steel bracket and the self-ligating ceramic bracket with a stainless-steel slot (P<0.05). The areas of artifacts from the ceramic bracket were the smallest, but were not reduced significantly in pulse sequences with higher bandwidth values (P<0.05). Significant differences were also observed between 1.5 T and 3.0 T MRI using SE and UTE, but not using GE 2-dimensional or 3-dimensional pulse sequences.

Conclusion

Higher receiver bandwidth might be indicated to prevent artifacts from orthodontic appliances in 1.5 T and 3.0 T MRI using SE and UTE pulse sequences.

Comparison of the failure rate, bonding time and ARI score of two orthodontic bonding systems: Self-Etch Primer and Conventional Etching Primer: A systematic review and meta-analysis

OBJECTIVE

This study aimed to evaluate the failure incidence of brackets with at least six months follow-up between self-etch primer and conventional etch/primer, as well as to investigate the clinical duration of the bonding process and the amount of adhesive remnant index (ARI).

METHODS

Electronic search was conducted in databases including PubMed, Scopus, Web of Science, ProQuest, ClinicalTrials.gov, and ICTRP (International Clinical Trials Registry Platform). The electronic search targeted only randomized clinical trials and was limited from January 2000 to June 2021. Delphi list is used to evaluate the risk of bias and Stata Version14.2 software was used. This systematic review was conducted according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) and recorded on the Ethics Committee of Research Institute of Dental Sciences, SBMU (IR.SBMU.DRC.REC.1398.240).

RESULTS

Out of 2288 extracted studies, 30 of them entered the full-text evaluation process. According to the inclusion criteria, 15 studies entered this systematic review. Containing 607 participants and 10,563 brackets/teeth. All the included studies were of randomized clinical trials (RCT) design with either parallel or split-mouth design. Comparing the two groups, the risk difference effect (RD)=0.007 CI 95% (-0.004,0.018) indicated a neglectable difference in the risk of bracket failure during treatment between the two groups. The index I²=53.9% indicated moderate heterogeneity in the results. Furthermore, the P-value=0.007 indicated statistical insignificance between the two interventions in terms of failure rate. The clinical duration of bonding time analysis were equal to SMD _Cohen=-2.67 CI95% (-3.49, -1.85), which indicated a statistically significant reduction in clinical process time, using the self-etch primer. Data synthesis for adhesive remnant index could not be conducted due to heterogeneity among included studies.

CONCLUSIONS

There was no difference between the self-etch primer and conventional etch/primer in bracket debonding at a medium level of evidence, However, there was statistically significant reduction in clinical bonding time using self-etch primer.

Compliance with the ISO 27020:2019 norm of a sample of currently available preadjusted Orthodontic bracket systems. Are the actual dimensions as expected?

Background

Determine the exact slot dimension of a sample of a MBT prescription stainless steel conventional brackets from different manufacturers to compare the actual values with the nominal ones declared by the manufacturers and to verify the compliance with tolerance limits given by the ISO 27020:2019. Different batches from each manufacturer were evaluated to determine whether or not they are different in size. In addition, the geometry of the slot walls was assessed.

Methods

360 stainless steel preadjusted orthodontic brackets of 12 different manufacturers were assessed. All brackets had a nominal slot size of 0.022 by 0.028 inches, belonged to the right upper central incisor, and were fabricated with the metal injection molding technique (MIM). For each manufacturer, three different manufacturing batches were evaluated. Brackets were coded using a single-blind design.

Results

All bracket systems in the study group except one displayed a statistically significant difference with the nominal declared value, although only four of the systems did not comply with the tolerance limits established by the ISO 27020:2019. In most of the systems, the slot height was oversized when compared to the nominal one. A significant interbatch variability was found in most of the evaluated systems. Most of the brackets walls were divergent.

Conclusions

The dimensional accuracy of commercially available metal brackets is not guaranteed. The respect for the norm should be enforced as well as the quality controls along the manufacturing process since orthodontic brackets are a precision medical device.

Antimicrobial Efficacy of Silver Nanoparticles Incorporated in an Orthodontic Adhesive: An Animal Study

Objectives:

This study assessed the antimicrobial efficacy of silver nanoparticles (AgNPs) incorporated in Transbond XT orthodontic adhesive used in rats.

Materials and Methods:

Transbond XT orthodontic adhesive containing 0%, 1%, 5% and 10% AgNPs was experimentally produced. Twenty-eight male Wistar rats were randomly divided into four groups (n=7) of control (0% AgNPs), 1% AgNPs, 5% AgNPs and 10% AgNPs. After anesthetizing the rats, one drop (10 μm) of the adhesive was applied on the central incisor, and light-cured for 20 s. Transbond XT composite (1×1×1 mm) was also applied. Another 10-μm drop was applied over it, and light-cured for 40 s. Biofilm test was carried out, and the number of colony forming units (CFUs) of Streptococcus sanguinis (S. sanguinis), Streptococcus mutans (S. mutans) and Lactobacillus acidophilus (L. acidophilus) in the saliva of rats was counted at baseline and 24 h after the application of adhesive. The data were analyzed using one-way ANOVA and Tukey’s test.

Results:

In presence of 5% and 10% AgNPs, S. sanguinis and L. acidophilus counts were significantly lower than those in the control and 1% AgNP groups (P<0.05). The S. mutans colony count was significantly lower in presence of all concentrations of AgNPs compared with the control group (P<0.05). The S. mutans colony count in 10% AgNP group was significantly lower than that in 1% and 5% AgNP groups (P<0.05).

Conclusion:

Silver nanoparticles have dose-dependent antimicrobial effects; 5% concentration is the minimum concentration of AGNPs with optimal antimicrobial efficacy against all strains evaluated in this study.

Shear bond strength of APC Plus adhesive coated appliance system to enamel in wet and dry conditions: An in vitro study

OBJECTIVE

It is claimed that a hydrophilic primer, called the moisture insensitive primer (MIP), can be used with both dry and wet enamel surfaces. This study sought to assess the shear bond strength (SBS) of APC Plus adhesive coated appliance system to enamel using MIP in wet and dry conditions.

MATERIALS AND METHODS

This in vitro experimental study evaluated 24 extracted maxillary premolars with intact buccal enamel. The teeth were randomly divided into two groups (n=12), and APC Plus premolar brackets were bonded to their buccal surface using moisture insensitive primer (MIP) under wet and dry enamel conditions. The SBS values were measured by a universal testing machine. The adhesive remnant index (ARI) score was also determined under a stereomicroscope. Data were analyzed using t-test and Mann-Whitney test at P<0.05 level of significance.

RESULTS

The SBS in wet condition was significantly lower than that in dry condition (mean value of 18.37MPa versus 25.5MPa, P<0.001). The two groups had no significant difference regarding the ARI scores (P>0.05). However, in both groups, less adhesive was left on the tooth surface. This suggests that bond failure occurred at the adhesive-enamel interface.

CONCLUSIONS

APC Plus adhesive coated appliance system in combination with hydrophilic MIP can be effective in clinical conditions with high risk of moisture contamination.

Shear Bond Strength of Brackets Bonded with Self-Etching Primers Compared to Conventional Acid-Etch Technique: A Randomized Clinical Trial

Objectives:

The purpose of this randomized clinical trial (RCT) was to compare the shear bond strength (SBS) of orthodontic brackets bonded to enamel with conventional acid-etch (AE) technique and self-etching primers (SEP).

Materials and Methods:

Twenty-two patients, requiring extraction of two bicuspids for orthodontic reasons, were recruited. In each individual, following blinding and allocation concealment, one intact premolar received conventional AE, whereas the contralateral premolar received SEP with a split-mouth design. Bonded brackets remained in the oral cavity for two months. Afterward, the teeth were extracted without debonding the brackets. SBS and adhesive remnant index (ARI) were measured using a Universal Instron machine and a stereomicroscope, respectively.

Results:

The mean SBS of the conventional AE and SEP groups was 9.53 and 9.20 MPa, respectively. Paired t-test showed no statistically significant difference between the two groups (P=0.096). Comparison of ARI between the two groups, using Wilcoxon test, indicated that significantly less adhesive remained on enamel with brackets bonded with SEP compared to brackets bonded with conventional AE (P<0.001) although the SBS was higher in the AE group.

Conclusion:

The present study indicated that although there is no significant difference in SBS between SEP and conventional AE for bonding orthodontic metal brackets, the amount of residual adhesive on the enamel surface is significantly less with SEP than with conventional AE.

(IRCT registration number: IRCT201705099086N3).

Pain perception of orthodontic treatment - A cross-sectional study

Objectives:

The objectives were to evaluate the intensity of pain perceived 24 hours following insertion of fixed orthodontic appliance components i-e separators, bands and brackets.

Methods:

This cross-sectional study conducted at a Dental College in Karachi (July 2017-March 2018) investigated the amount of pain perceived during different stages of fixed orthodontic treatment. The inclusion criteria were healthy individuals without systemic disease, age 13-26 years, fixed orthodontic treatment candidates having healthy permanent first molars. The exclusion criteria were missing permanent first molars, patients requiring brass wire separators instead of elastomeric separators and molar tubes instead of bands, ongoing or previous periodontal disease and syndromic patients. Pain intensity was assessed in ninety eight patients using a Numeric Rating scale (NRS) at baseline (T0) before insertion, and 24 hours after insertion (T1) of a component. This procedure was repeated six times, twice each for separators, bands and brackets. Scoring was done on the NRS from 0 to 10 where 0 indicated no pain and 10 indicated worst pain possible.

Results:

A significant difference in perceived pain was found between baseline and after 24 hours of placement of all components (P-value 0.000). Odds ratio indicated that males were at a greater risk to feel pain than females at baseline and after 24 hours of insertion of all components. Mann-Whitney U test showed that the most painful components at baseline were bands (Mean value=0.56) and after 24 hours were brackets (Mean value 6.25).

Conclusions:

Significant increase in pain was noted 24 hours after insertion of separators, bands and brackets. The most painful components were bands at baseline and brackets after 24 hours of insertion. There were no significant variations in pain perception based on age. However, males perceived higher pain than females both at baseline and after 24 hours.

Effect of Er:YAG and Er,Cr:YSGG Lasers on Ceramic Bracket Debonding from Composite Blocks

Objectives:

This study aimed to assess the effect of erbium-doped yttrium aluminum garnet (Er:YAG) and erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) lasers on the shear bond strength (SBS) of ceramic brackets debonding from the surface of composite blocks.

Materials and Methods:

Thirty-six composite blocks were fabricated using Filtek Z250 light-cure composite. Block surfaces were etched with 37% phosphoric acid for 30 seconds and then rinsed with water for 20 seconds and dried. Maxillary right central incisor ceramic orthodontic brackets were bonded to the surfaces of composite blocks using Transbond XT adhesive and were cured for 40 seconds. Twelve samples were irradiated with Er:YAG laser, while 12 samples were irradiated with Er,Cr:YSGG laser, and the brackets were then debonded using a universal testing machine. Twelve samples served as controls (debonding using the universal testing machine without using a laser). The adhesive remnant index (ARI) score and bracket or composite cracks were evaluated under a stereomicroscope. One-way analysis of variance (ANOVA) was used for the comparison of the three groups. Kruskal-Wallis test was used to compare the ARI scores.

Results:

The mean SBS was 17.01±5.22 MPa with Er:YAG laser, 18.03±6.46 MPa with Er,Cr:YSGG laser, and 16.61±6.73 MPa in the control group; the difference of the three groups was not significant (P=0.835). The difference in the ARI scores and enamel and composite cracks was not significant either (P>0.05).

Conclusion:

This study did not show any reduction in the bond strength of ceramic bracket to composite blocks after Er:YAG and Er,Cr:YSGG laser irradiation.

Effect of 0.05% Sodium Fluoride Mouthwash on Surface Roughness and Friction between Ceramic Brackets and Rhodium-Coated and Uncoated Stainless Steel Wires

Objectives:

This study aimed to assess the effect of 0.05% sodium fluoride (NaF) mouthwash on the surface roughness and friction between ceramic brackets and rhodium-coated (RC) and uncoated stainless steel (SS) wires.

Materials and Methods:

This experimental study was performed on 48 maxillary premolar ceramic brackets. Twenty-four pieces of RC-SS wires were used. Samples were divided into four groups. Groups 1 and 2 were immersed in artificial saliva, and groups 3 and 4 were immersed in a solution consisting of artificial saliva (9%) and mouthwash (91%). To assess surface roughness, images were obtained from the surface of wires and brackets with atomic force microscopy (AFM) and scanning electron microscopy (SEM) before and after the intervention. To assess friction, the wires were ligated into brackets, and friction was measured at a crosshead speed of 0.5 mm/minute using a universal testing machine. Data were analyzed using one-way analysis of variance (ANOVA) at the 0.05 significance level.

Results:

Friction during sliding in RC wires was significantly less than that in SS wires (P<0.05). Increase in the friction in SS wires by mouthwash was significantly greater compared to RC wires (P<0.05). Surface roughness coefficients of the wires before the intervention were not significantly different. The surface roughness of the wires significantly increased after the intervention and it was greater in SS wires than in RC wires (P<0.05).

Conclusion:

Considering the lower friction and surface roughness of SS-RC wires compared to SS wires, SS-RC wires may be a better alternative for use with ceramic brackets.

Evaluation of the Shear Bond Strength and Adhesive Remnant Index in Debonding of Stainless Steel Brackets Assisted with Nd:YAG Laser Irradiation

Objectives:

The purpose was to compare shear bond strength (SBS), pulp temperature, and adhesive remnant index (ARI) in debonding of stainless steel brackets from enamel surface using neodymium-doped yttrium aluminum garnet (Nd:YAG) laser versus the conventional debonding method.

Materials and Methods:

Forty-eight extracted premolars were bonded to stainless steel brackets. The samples were divided into three experimental groups and one control group. In the first three groups, Nd:YAG laser was used for debonding with the power of 1, 1.5, and 2 W, respectively, for 10 seconds. The SBS and ARI of the samples were assessed. Pulp temperature was recorded before and after irradiation. Two samples from each group were used for determining enamel morphology after debonding using scanning electron microscopy (SEM).

Results:

The mean SBS in the groups was 33.05, 28.69, 24.37, and 31.53 MPa, respectively, with no statistically significant differences (P=0.205). Significant differences in post-irradiation temperature were noted among the lased groups (P=0.000). Debonding mainly occurred at the adhesive-enamel interface in the 1-W laser and control groups and at the bracket-adhesive interface in the 1.5-W and 2-W laser groups. Enamel structure was amorphous and irregular following laser irradiation.

Conclusion:

Based on the results of this study, the use of Nd:YAG laser could not significantly affect the SBS. Therefore, this laser would not be suitable for debonding of metal brackets. The use of a 2-W laser could significantly raise the pulpal temperature. Nd:YAG laser renders a more heterogeneous enamel morphology compared to conventional debonding methods.

Shear Bond Strength of Orthodontic Brackets to Composite Restorations Using Universal Adhesive

STATEMENT OF THE PROBLEM

The dental adhesives may have the potential to increase the bond strength of orthodontic brackets to composite resin and it would be highly desirable if adequate bracket-composite bond strength could be yielded by using these adhesives without the need for surface roughening.

PURPOSE

The purpose of this study was to measure the shear bond strength (SBS) of metal brackets to composite restorations by use of a universal adhesive compared with a conventional adhesive.

MATERIALS AND METHOD

In this in vitro, experimental study, 45 composite discs measuring 6 mm in diameter and 4 mm in thickness were fabricated and assigned to three groups (n=15). In the group 1, discs were etched with 37% phosphoric acid for 15 seconds and Scotchbond Universal was then applied. Discs were roughened by diamond bur in the group 2 and were subjected to the application of Scotchbond Universal. In the group 3, conventional adhesive (Single Bond 2) was applied after roughening the discs by diamond bur. Metal brackets were then bonded to discs and after thermocycling, the SBS was measured by an Instron machine. The mode of failure and adhesive remnant index (ARI) score were determined using stereomicroscope. Data were analyzed by SPSS version 18, one-way ANOVA, and the Kruskal Wallis test.

RESULTS

The surface roughening plus universal adhesive group showed the highest SBS (11.90 MPa) but according to one-way ANOVA, the difference in this regard among the three groups was not statistically significant (p= 0.94). Most samples showed ARI score of 4.

CONCLUSION

Universal adhesive can provide sufficient bond strength as high as that provided by conventional adhesives for orthodontic bracket bonding to composite restorations even in absence of surface roughening by bur.

Comparison of Shear Bond Strength Orthodontic Brackets Bonded to Zirconia and Lithium Disilicate Crowns

Aim

of this study was to analyze Shear Bond Strength (SBS) and Adhesive Remnant Index (ARI) of ceramic and metallic orthodontic brackets bonded to zirconia or lithium-disilicate ceramics used for prosthetic restorations, conditioned with hydrofluoric acid (HFA) or phosphoric acid (PhA), as well as to determine the Porcelain Fracture Index (PFI), in order to examine the condition of the ceramic surface after debonding.

Material and methods

The research was conducted on 96 prepared all-ceramic samples divided into 8 groups combined from the type of ceramic material, orthodontic brackets, and surface conditioning. SBS was tested with Universal Testing Machine, and the samples were analyzed using a Scanning Electron Microscope, to determine ARI and PFI. Statistical data were processed using ANOVA, with the level of significance α = 0.05.

Results

Lithium-disilicate showed better bond strength in almost all groups. However, no significant difference between the groups was noticed and none of the factors had a significant influence on the mean values of SBS (p>0.05). Nevertheless, ARI significantly depended on the type of bracket (p = 0.005), and PFI significantly depended on the type of etchant (p = 0.029).

Conclusion

The use of HFA for surface etching of zirconia and lithium-disilicate, does not cause a significant increase in the SBS values as compared to etching with PhA and silane application. Furthermore, HFA can weaken the surface structure of the ceramic, and considering its toxicity, might not be the best suitable conditioner prior to orthodontic bonding to lithium disilicate, and in particular to zirconia, also taking into account its crystalline structure.

Effect of Cyclic Loading on Shear Bond Strength of Orthodontic Brackets: An In Vitro Study

OBJECTIVES

In clinical conditions, orthodontic brackets are exposed to periodic stresses mainly induced by mastication and intraoral forces. The objective of the present study was to evaluate the effects of cyclic loading to simulate masticatory forces on shear bond strength (SBS) of metal brackets bonded to teeth using self-etch and total-etch bonding systems.

MATERIALS AND METHODS

Eighty-four caries- and crack-free bovine mandibular incisors were selected and randomly assigned to two groups based on the type of bonding system. After bonding, all samples were thermocycled (500 cycles) followed by cyclic loading of the half of the specimens in each group by applying 40 N load with 2 Hz frequency for 10,000 cycles. The SBS was measured using a universal testing machine. The adhesive remnant index (ARI) score was calculated subsequently. Data were analyzed using Kolmogorov-Smirnov test, two-way ANOVA and Mann-Whitney test.

RESULTS

The SBS was 10.09±3.78 MPa and 14.44±6.06 MPa for self-etch and total-etch bonding systems in cyclic loading group, respectively. The SBS was 9.43±5.3 MPa and 11.31±5.42 MPa in self-etch and total-etch groups without cyclic loading, respectively. Cyclic loading did not cause any significant difference in SBS (P>0.05). The ARI scores of the groups were significantly different (P<0.05).

CONCLUSIONS

The present results demonstrated that low masticatory forces at 10,000 cycles did not have a significant impact on bracket-adhesive SBS; however, they significantly changed the ARI score. Even though the total-etch bonding system yielded higher SBS than the self-etch system, the performance of both was clinically acceptable.

Shear Bond Strength of Rebonded Ceramic Brackets Using Four Different Methods of Adhesive Removal

OBJECTIVES

Rebonding of isolated brackets is an economic option that can be conducted using available in-office or commercial recycling methods. Nowadays, lasers are known as an efficient modality for composite removal, but there is not much information available about using lasers for removal of adhesive remnants from the ceramic bracket base.

MATERIALS AND METHODS

Fifty human premolar teeth were divided into five groups. Samples in all groups were bonded to ceramic brackets. Brackets in four groups were debonded and the remaining adhesive was removed by Er:YAG laser, Er;Cr:YSGG laser, sandblasting or direct flame. After removing adhesives from the tooth surfaces by carbide bur, the recycled brackets were bonded again. in the control group, new ceramic brackets were bonded. Finally, all brackets were debonded by universal testing machine and their shear bond strength (SBS) was measured. The adhesive remnant index (ARI) was calculated under a stereomicroscope at ×10 magnification. Data were analyzed using oneway ANOVA and Tukey's test.

RESULTS

SRS values showed no significant difference among the five groups (P=0.568). The highest SRS was noted in the control group (7.46±1.4 MPa), followed by Er:YAG laser group (7.40±1.24 Mpa) and the lowest was noted in the flame group (6.32±2.3 Mpa). ARI scores indicated that most of the adhesive remained on the tooth surface in all groups.

CONCLUSIONS

Recycling of ceramic brackets with Er:YAG laser is an efficient in-office method which causes the least damage to the bracket base. However, all methods of bracket recycling showed acceptable SBS.

Effect of Different Types of Toothpaste on the Frictional Resistance Between Orthodontic Stainless Steel Brackets and Wires

OBJECTIVES

The purpose of this study was to investigate the effect of different types of toothpaste on the frictional resistance between stainless steel brackets and archwires.

MATERIALS AND METHODS

Ninety stainless steel orthodontic brackets with stainless steel wires were bonded to bovine teeth and were divided into 6 groups for application of the following toothpastes: Colgate® Total® Advanced Whitening, Colgate® Total® Pro Gum Health, Colgate® Anticavity, Ortho.Kin®, and Sunstar GUM® Ortho toothpastes. No toothpaste was applied in the control group. Each group was brushed by a brushing machine with the use of the designated solution for 4.5 minutes. The frictional force was measured in a universal testing machine with a crosshead speed of 10 mm/minute over a 5-mm archwire. Data were analyzed using one-way analysis of variance (ANOVA) at the 0.05 significance level.

RESULTS

The frictional resistance values of Ortho.Kin® and GUM® Ortho toothpastes and the control group were not significantly different (P>0.05). However, there were significant differences between the frictional resistance values of Colgate® Total® Pro Gum Health and Colgate® Anticavity toothpastes with that of the control group (P<0.05). The highest and lowest frictional resistance values were related to Colgate® Total® Pro Gum Health toothpaste and the control group, respectively.

CONCLUSIONS

Among the evaluated toothpastes, the orthodontic toothpastes did not increase the frictional resistance between the orthodontic stainless steel brackets and wires.

Effect of Surface Treatment on Enamel Cracks After Orthodontic Bracket Debonding: Er,Cr:YSGG Laser-Etching Versus Acid-Etching

OBJECTIVES

This study sought to compare enamel cracks after orthodontic bracket debonding in the surfaces prepared with erbium, chromium: yttrium-scandium-galliumgarnet (Er,Cr:YSGG) laser and the conventional acid-etching technique.

MATERIALS AND METHODS

This in-vitro experimental study was conducted on 60 sound human premolars extracted for orthodontic purposes. The teeth were randomly divided into two groups (n=30). The teeth in group A were etched with 37% phosphoric acid gel, while the teeth in group B were subjected to Er,Cr:YSGG laser irradiation (gold handpiece, MZ8 tip, 50Hz, 4.5W, 60μs, 80% water and 60% air). Orthodontic brackets were bonded to the enamel surfaces and were then debonded in both groups. The samples were inspected under a stereomicroscope at ×38 magnification to assess the number and length of enamel cracks before bonding and after debonding. Independent-samples t-test was used to compare the frequency of enamel cracks in the two groups. Levene's test was applied to assess the equality of variances.

RESULTS

No significant difference was noted in the frequency or length of enamel cracks between the two groups after debonding (P>0.05).

CONCLUSIONS

Despite the same results of the frequency and length of enamel cracks in the two groups and by considering the side effects of acid-etching (demineralization and formation of white spot lesions), Er,Cr:YSGG laser may be used as an alternative to acid-etching for enamel surface preparation prior to bracket bonding.

Comparison of Bond Strength of Metal and Ceramic Brackets Bonded with Conventional and High-Power LED Light Curing Units

OBJECTIVES

The aim of this study was to evaluate the effect of conventional and high-power light emitting diode (LED) light curing units on shear bond strength (SBS) of metal and ceramic brackets to tooth surface.

MATERIALS AND METHODS

Forty sound bovine maxillary central incisors were used for the study. The teeth were divided into four groups (n=10). Teeth surfaces were etched with 37% phosphoric acid for 20 seconds. After applying a uniform layer of adhesive primer on the etched enamel, composite was placed on the base of brackets. The samples were light cured according to the manufacturer's instructions and thermocycled. The SBS was measured. The failure mode was scored using the adhesive remnant index (ARI).

RESULTS

The mean SBS of samples in groups A (high-power LED, metal bracket), B (high-power LED, ceramic bracket), C (conventional LED, metal bracket) and D (conventional LED, ceramic bracket) was 23.1±3.69, 10.7±2.06, 24.92±6.37 and 10.74±3.18MPa, respectively. The interaction effect of type of LED unit (high-power/conventional) and bracket type on SBS was not statistically significant (P=0.483). In general, type of LED unit did not affect SBS. Type of bracket significantly affected SBS (P<0.001). The ARI score was not significantly influenced by the interaction between the type of LED unit and bracket.

CONCLUSIONS

The obtained SBS is the same for both bracket types by use of high-power and conventional LED light curing units. Regardless of the type of LED unit, SBS of ceramic brackets was significantly lower than that of metal brackets.

Effect of Addition of Curcumin Nanoparticles on Antimicrobial Property and Shear Bond Strength of Orthodontic Composite to Bovine Enamel

OBJECTIVES

This study sought to assess the effect of curcumin nanoparticles (curcNPs) on antimicrobial property and shear bond strength (SBS) of orthodontic composite to bovine enamel.

MATERIALS AND METHODS

In this in vitro, experimental study, 1%, 5% and 10% curcNPs were added to Transbond XT composite. Stainless steel brackets were bonded to 48 sound bovine incisors in four groups (n=12) using composite containing 0% (control), 1%, 5% and 10% curcNPs. The bracket-tooth SBS was measured by a universal testing machine. The adhesive remnant index (ARI) score was calculated after debonding using a stereomicroscope. Also, 180 discs were fabricated of the four composites; 108 were subjected to eluted component test, 36 were used for disc diffusion test and 36 were used for biofilm test to assess their antimicrobial activity against Streptococcus mutans, Streptococcus sanguinis and Lactobacillus acidophilus.

RESULTS

The highest and lowest SBS belonged to control and 10% curcNP groups, respectively. The difference in SBS was significant among the four groups (P=0.008). The SBS of control group was significantly higher than that of 10% curcNPs (P=0.006). The four groups were not significantly different in terms of ARI score (P>0.05). Growth inhibition zones were not seen in any group. In biofilm test, the colony counts of all bacteria significantly decreased by an increase in percentage of curcNPs. Colony count significantly decreased only at 30 days.

CONCLUSIONS

At 1% concentration, curcNPs have significant antimicrobial activity against cariogenic bacteria with no adverse effect on SBS. However, insolubility of curcNPs remains a major drawback.

Evaluation of Antibacterial Effects of Silver-Coated Stainless Steel Orthodontic Brackets

OBJECTIVES

White spots and enamel demineralization around orthodontic brackets are among the most important complications resulting from orthodontic treatments. Since the antibacterial properties of metals and metallic particles have been well documented, the aim of this study was to assess the antibacterial effect of stainless steel orthodontic brackets coated with silver (Ag) particles.

MATERIALS AND METHODS

In this study, 40 standard metal brackets were divided into two groups of 20 cases and 20 controls. The brackets in the case group were coated with Ag particles using an electroplating method. Atomic force microscopy and scanning electron microscopy were used to assess the adequacy of the coating process. In addition, antibacterial tests, i.e., disk diffusion and direct contact tests were performed at three, six, 24, and 48 hours, and 15 and 30 days using a Streptococcus mutans strain. The results were analyzed using Student's t-test and repeated measures ANOVA.

RESULTS

Analyses via SEM and AFM confirmed that excellent coatings were obtained by using an electroplating method. The groups exhibited similar behavior when subjected to the disk diffusion test in the agar medium. However, the bacterial counts of the Ag-coated brackets were, in general, significantly lower (P<0.001) than those of their non-coated counterparts.

CONCLUSIONS

Brackets coated with Ag, via an electroplating method, exhibited antibacterial properties when placed in direct contact with Streptococcus mutans. This antibacterial effect persisted for 30 days after contact with the bacteria.

Effect of Saliva Contamination on Microleakage Beneath Bonded Brackets: A Comparison Between Two Moisture-Tolerant Bonding Systems

OBJECTIVES

This study aimed to evaluate the effects of saliva contamination on the metallic bracket microleakage bonded with two moisture-tolerant bonding systems.

MATERIALS AND METHODS

Ninety freshly extracted premolar teeth were randomly divided into six groups of 15 with the following treatments: G1 (control): After acid etching, Assure primer and Assure adhesive were applied to non-contaminated enamel surfaces. G2 (contaminated after etching): The etched enamel surface was exposed to saliva, then Assure primer and Assure adhesive were applied. G3 (contaminated after priming): Saliva contamination was done after application of Assure primer. The exact same procedures were applied to groups G4 to G6 except that TIMP primer and Transbond Plus adhesive system were used. To measure the microleakage score, the teeth were stained with 2% methylene blue for 24 hours, sectioned and examined under a stereomicroscope at ×16 magnification. Data analysis was performed using Fisher's exact test.

RESULTS

In dry conditions, Assure and TMIP were not significantly different in terms of microleakage scores. All contaminated groups exhibited higher microleakage score at the enamel/adhesive interface compared to the bracket/adhesive interface (P< 0.01). In wet conditions, Assure groups showed higher microleakage at the enamel-adhesive interface compared to the TMIP groups (P<0.05). At the bracket-adhesive interface, the microleakage scores were not significantly different in saliva contaminated groups compared to the controls.

CONCLUSION

Saliva contamination caused greater microleakage at the enamel-adhesive interface compared to the adhesive-bracket interface.

A comparative study of metal artifacts from common metal orthodontic brackets in magnetic resonance imaging

Purpose

This study was performed to compare the metal artifacts from common metal orthodontic brackets in magnetic resonance imaging.

Materials and Methods

A dry mandible with 12 intact premolars was prepared, and was scanned ten times with various types of brackets: American, 3M, Dentaurum, and Masel orthodontic brackets were used, together with either stainless steel (SS) or nickel titanium (NiTi) wires. Subsequently, three different sequences of coronal and axial images were obtained: spin-echo T₁-weighted images, fast spin-echo T₂-weighted images, and fluid-attenuated inversion recovery images. In each sequence, the two sequential axial and coronal images with the largest signal-void area were selected. The largest diameters of the signal voids in the direction of the X-, Y-, and Z-axes were then measured twice. Finally, the mean linear values associated with different orthodontic brackets were analyzed using one-way analysis of variation, and the results were compared using the independent t-test to assess whether the use of SS or NiTi wires had a significant effect on the images.

Results

Statistically significant differences were only observed along the Z-axis among the four different brands of orthodontic brackets with SS wires. A statistically significant difference was observed along all axes among the brackets with NiTi wires. A statistically significant difference was found only along the Z-axis between nickel-free and nickel-containing brackets.

Conclusion

With respect to all axes, the 3M bracket was associated with smaller signal-void areas. Overall, the 3M and Dentaurum brackets with NiTi wires induced smaller artifacts along all axes than those with SS wires.

Effect of Saliva pH on Shear Bond Strength of Orthodontic Brackets

OBJECTIVES

The purpose of this study was to evaluate the effect of salivary pH on the shear bond strength (SBS) of orthodontic brackets to tooth surface.

MATERIALS AND METHODS

Eighty intact premolars were randomly divided into four groups of 20. After bonding a bracket on each tooth, the groups one to four were stored in artificial saliva at a pH of 3.8, 4.8, 5.8, and 6.8, respectively for two months. The artificial saliva solutions were refreshed weekly. Each tooth was then embedded in an acrylic block so that the crown was exposed and its buccal surface was parallel to the direction of the force during SBS testing. All brackets were debonded using Dartec universal testing machine, and the mean values of SBS in different groups were compared using one-way analysis of variance (ANOVA).

RESULTS

The mean SBS value in group one (pH 3.8) was significantly lower than that in other groups (P<0.05). The differences between other groups were not significant (P>0.05).

CONCLUSION

Decreased salivary pH due to poor oral hygiene and/or frequent consumption of acidic beverages may be responsible for orthodontic bracket bond failure.

In vitro evaluation of microleakage around orthodontic brackets using laser etching and Acid etching methods

OBJECTIVE

path of microleakage between the enamel and adhesive potentially allows microbial ingress that may consequently cause enamel decalcification. The aim of this study was to compare microleakage of brackets bonded either by laser or acid etching techniques.

MATERIALS AND METHOD

The specimens were 33 extracted premolars that were divided into three groups as the acid etching group (group 1), laser etching with Er:YAG at 100 mJ and 15 Hz for 15s (group 2), and laser etching with Er:YAG at 140 mJ and 15 Hz for 15s (group 3). After photo polymerization, the teeth were subjected to 500 thermal cycles. Then the specimens were sealed with nail varnish, stained with 2% methylen blue for 24hs, sectioned, and examined under a stereomicroscope. They were scored for marginal microleakage that occurred between the adhesive-enamel and bracket-adhesive interfaces from the occlusal and gingival margins. Data were analyzed with the Kruskal- Wallis test.

RESULTS

For the adhesive-enamel and bracket-adhesive surfaces, significant differences were not observed between the three groups.

CONCLUSION

According to this study, the Er:YAG laser with 1.5 and 2.1 watt settings may be used as an adjunctive for preparing the surface for orthodontic bracket bonding.

Assessment of Bond Strength between Metal Brackets and Non-Glazed Ceramic in Different Surface Treatment Methods

OBJECTIVE

The aim of this study was to evaluate the bond strength between metal brackets and non-glazed ceramic with three different surface treatment methods.

MATERIALS AND METHODS

Forty-two non-glazed ceramic disks were assigned into three groups. Group I and II specimens were etched with 9.5% hydrofluoric acid. Subsequently in group I, silane and adhesive were applied and in group II, bonding agent was used only. In group III, specimens were treated with 35% phosphoric acid and then silane and adhesive were applied. Brackets were bonded with light-cured composites. The specimens were stored in water in room temperature for 24 hours and then thermocycled 500 times between 5°C and 55°C.

RESULTS

The difference of tensile bond strength between groups I and III was not significant (P=0.999). However, the tensile bond strength of group II was significantly lower than groups I, and III (P<0.001). The adhesive remnant index scores between the three groups had statistically significant differences (P<0.001).

CONCLUSION

With the application of scotch bond multi-purpose plus adhesive, we can use phosphoric acid instead of hydrofluoric acid for bonding brackets to non-glazed ceramic restorations.