In vitro evaluation of microleakage under orthodontic brackets using two different laser etching, self etching and acid etching methods

Effect of various orthodontic adhesives on enamel colour changes after fixed treatment

BACKGROUND

The aim of this study was to compare enamel colour changes of incisors and canines produced by various orthodontic adhesives following treatment with fixed appliances.

METHODS

The study included 300 maxillary and mandibular central and lateral incisors, and canines of 25 subjects who finished fixed appliance treatment. The following adhesives were used according to the manufacturer's instructions: Transbond XT (3M Unitek, Monrovia, CA, USA), Kurasper F (Kuraray Europe GmbH, Frankfurt, Germany), Grengloo (Ormco Corporation, Glendora, CA, USA) and Light Bond (Reliance Orthodontic Products, Itasca, IL, USA). Different adhesives were placed in each quadrant of the subjects. Pretreatment and posttreatment enamel colours were evaluated at the middle third of the buccal surfaces of teeth using the SpectroShade Micro Dental Colour Complete Tooth Analysis System^TM (MHT International, Verona, Italy). Tooth colour was determined using the Commission Internationale de l'Eclairage L* a* b* system, and ∆E values were calculated.

RESULTS

Pretreatment and posttreatment intragroup comparison results showed significant decreases in L* and b*, as well as insignificant changes in a* for all teeth. Significantly less enamel colour changes occurred in the Kurasper F group compared with the Grengloo and Light Bond groups. Evaluating incisors and canines separately, overall intergroup comparisons were not significant. Enamel colour changes were significantly less only for the canines compared to the incisors in the Transbond XT and Kurasper F groups. The ∆E values were 1.83-2.18 and 1.41-1.95 for incisors and canines, respectively.

CONCLUSION

Although statistically less enamel colour changes occurred in the Kurasper F group compared with the Grengloo and Light Bond groups, the observed changes were not clinically relevant.

Experimental study of brackets adhesion with a novel enamel-protective material compared with conventional etching

INTRODUCTION

A reliable adhesion between fixed devices and dental surfaces is a key factor for the clinical success of any orthodontic treatment. Adhesion preparation is associated with damages related to abrasive cleaning, enamel structure defacing caused by etching, enamel loss when removing resin remnants at orthodontic treatment finishing stage or when conditioning surface for adhesive failure and fractures at bracket removal.

AIM

The objective of this study was to compare the shear bond strength of metallic brackets to enamel adhered with a novel non-damaging and remineralizing material for enamel versus the traditional 37% phosphoric acid etching.

MATERIAL AND METHODS

75 Premolars collected from 15- to 40-years old healthy donors requiring extraction were collected. The teeth were then randomly divided into three groups (n = 25). One group was used for the experimental new method (EX), the second for the conventional phosphoric acid etching (PA) method and the third group was left without any treatment (NT). The metallic brackets were fixed with Transbond® XT adhesive and composite resin polymerized for 40 s with a halogen photocuring lamp. The shear bond strength was quantified by means of a universal testing machine at 1 mm/min crosshead speed and a load cell of 1 kN.

STATISTICAL ANALYSIS USED

Tests of normality, adjustment of the data to a root square, a one-way ANOVA and Tukey tests were performed.

RESULTS

Statistically significant differences between the NT (1.4 MPa), PA (32.1 MPa) and EX (9.7 MPa) groups were observed.

CONCLUSIONS

The experimental material for conditioning human enamel induces calcium phosphates crystals on the enamel surface and improves the bond strength in comparison to the NT group.

Laser-Aided Enamel Conditioning: A Comparison of Microleakage Under Brackets Following Different Aging Procedures

Objective:

To evaluate microleakage under the orthodontic adhesives applied following two version of erbium:yttrium aluminum garnet (Er:YAG) laser-aided enamel conditioning after thermal and thermomechanical simulators.

Materials and Methods:

A comparative analytical study based on metal braces bonded on the enamel of extracted teeth ( n = 160) etched with acid, Er:YAG laser and Er:YAG laser with an X-Runner handpiece, and self-etch adhesives. An arch wire was ligatured to samples which were embedded in acrylic blocks by two with periodontal ligaments. The specimens were subdivided into two groups: those aged with thermal cycling and thermomechanical aging procedures. The samples were immersed in basic fuchsin solution (0.5%) for 24 h. Buccolingual sections were performed on the mesial and distal wings of the braces. The color penetration at the gingival and occlusal margins of the adhesive-bracket and enamel-adhesive was evaluated under a stereomicroscope. The median and mean values of microleakage in both groups were evaluated with Kruskal–Wallis and Mann–Whitney U tests ( P < .05).

Results:

The highest microleakage was recorded in the gingival part of the samples aged with the thermomechanical aging procedure ( P = .001). The amount of microleakage generally increased in the samples subjected to thermomechanical loading, but the only significant difference was recorded in the gingival part in each four different conditioning methods.

Conclusion:

Microleakage of the phosphoric acid-etched groups was recorded with lower values for both aging methods. Thermomechanical aging should be included to microleakage studies due to increased microleakage on gingival side for all etching groups.

Microleakage under ceramic flash-free orthodontic brackets after thermal cycling

OBJECTIVE

To compare microleakage under 3M Unitek's APC Flash-Free Adhesive Coated System bracket and the APC PLUS Adhesive Coated System bracket after thermal cycling.

MATERIALS AND METHODS

Forty freshly extracted human maxillary premolars were randomly divided into two groups and bonded with either a Flash-Free bracket or a PLUS bracket. After bonding, the samples were incubated in a water bath at 37°C for 24 hours and thermocycled for 5000 cycles between 5°C and 50°C. All teeth were immersed in a 2% methylene blue solution for 24 hours, embedded in acrylic and sectioned in a buccolingual direction at approximately the center of the bracket. Microleakage was observed at the enamel-adhesive interface from the occlusal and gingival margins of the bracket base. Statistical analysis was conducted using the Mann-Whitney U-test.

RESULTS

The median microleakage was higher in the Flash-Free group, but the difference between the two groups was not statistically significant (P > .05).

CONCLUSION

In a laboratory setting, there is no significant difference between the extent of microleakage under the APC Flash-Free Adhesive Coated System bracket and the APC PLUS Adhesive Coated System bracket after thermal cycling.

Microleakage under orthodontic brackets bonded with different adhesive systems

OBJECTIVE

This in vitro study aimed to compare the microleakage of orthodontic brackets between enamel-adhesive and adhesive-bracket interfaces at the occlusal and gingival margins bonded with different adhesive systems.

MATERIALS AND METHODS

A total of 144 human maxillary premolar teeth extracted for orthodontic reasons was randomly divided into four groups. Each group was then further divided into three sub-groups. Three total-etching bonding systems (Transbond XT, Greengloo and Kurasper F), three one-step self-etching bonding systems (Transbond Plus SEP, Bond Force and Clearfil S3), three two-step self-etching bonding systems (Clearfil SE Bond, Clearfil Protectbond and Clearfil Liner Bond), and three self-adhesive resin cements (Maxcem Elite, Relyx U 100 and Clearfil SA Cement) were used to bond the brackets to the teeth. After bonding, all teeth were sealed with nail varnish and stained with 0.5% basic fuchsine for 24 h. All samples were sectioned and examined under a stereomicroscope to score for microleakage at the adhesive-enamel and adhesive-bracket interfaces from both occlusal and gingival margins.

STATISTICAL ANALYSIS USED

Statistical analyses were performed with Kruskal-Wallis and Wilcoxon signed-rank tests.

RESULTS

The results indicate no statistically significant differences between the microleakage scores of the adhesives; microleakage was detected in all groups. Comparison of the average values of the microleakage scores in the enamel-adhesive and adhesive-bracket interfaces indicated statistically significant differences (P < 0.05). The amount of the microleakage was higher at the enamel-adhesive interface than at the bracket-adhesive interface.

CONCLUSIONS

All of the brackets exhibited some amount of microleakage. This result means that microleakage does not depend on the type of adhesive used.

Microleakage and shear bond strength of orthodontc brackets bonded to hypomineralized enamel following different surface preparations

Objectives: This study investigated the effects of several conditioning methods on shear bond strength (SBS) and microleakage of orthodontic brackets bonded to demineralized enamel. Study Design: One hundred premolars were selected and immersed in a cariogenic solution for 12 weeks. The teeth were randomly assigned into 5 groups. In groups 1 and 2, the teeth underwent acid etching for 30 and 120 seconds, respectively. In group 3, a combination of laser and acid etching was employed. A self-etch primer (SEP) was applied in group 4 and in group 5, the teeth were exposed to acidulated phosphate fluoride (APF) for 4 minutes before etching. After bracket bonding, the teeth were immersed in methylen blue for 12 hours and then were mounted in acrylic resin. SBS was determined with an Instron Universal Testing Machine and the amount of microleakage under the brackets was assessed under a stereomicroscope. Results: The lowest SBS was related to the SEP group and the highest one was observed in the specimens prepared by APF+acid etching. There was a significant difference in SBS (p=0.009), but not in microleakage (p=0.971) of the study groups. The SBS of the specimens treated with SEP was significantly Lower than the other groups, which were not significantly different from each other. The SEP group displayed a higher frequency of bond failure at the enamel-adhesive interface. Conclusions: Enamel preparation with SEP provided the lowest SBS among the groups. All groups showed some degree of microleakage. There was no significant correlation between SBS and microleakage.

Key words:Bond strength, microleakage, bonding, self-etch primer, Er:YAG laser.

Effect of enamel laser irradiation at different pulse settings on shear bond strength of orthodontic brackets

OBJECTIVE

To compare the effect of laser irradiation at two different pulse settings and acid etching on the shear bond strength (SBS) of orthodontic brackets to enamel.

MATERIALS AND METHODS

Thirty-six premolars were allocated to three groups (n  =  12): (1) 37% phosphoric acid etching, (2) erbium-doped yttrium aluminum garnet (Er:YAG) laser etching with medium-short pulse mode (MSP; 100 µs, 120 mj, 10 Hz, 1.2 W), and (3) Er:YAG laser etching with quantum-square pulse mode (QSP; 120 mj, 10 Hz, 1.2 W). Metallic brackets were bonded with Transbond XT. After photopolymerization, the samples were subjected to 5000 thermal cycles and debonded with a universal testing machine, and the SBS values were recorded. Surface morphology was evaluated with profilometric examination, scanning electron microscopy, and atomic force microscopy. The adhesive remnant index (ARI) was evaluated to assess the remaining adhesive.

RESULTS

The results of SBS testing were analyzed by one-way analysis of variance and Tukey honestly significant diffference tests. The mean SBS values of QSP and MSP laser groups were 11.80 ± 2.7 MPa and 10.10 ± 4.5 MPa, respectively, and the QSP group demonstrated significantly higher SBS (P < .01) than that of the acid-etched group (6.6 ± 2.4 MPa). No significant difference was observed between the SBS values of the two laser groups (P < .05). The difference between the ARI scores of the laser groups and the acid-etched group was statistically significant (P < .05).

CONCLUSION

Laser etching at MSP and QSP modes present successful alternatives to acid etching; however, long-term clinical studies are required to verify clinical success.

The effect of different surface treatments of demineralised enamel on microleakage under metal orthodontic brackets

BACKGROUND

The aim of this investigation was to assess the effects of different treatments of demineralised enamel on microleakage under orthodontic brackets.

METHODS

Seventy-five intact premolars were randomly assigned to five groups. The teeth in groups 2 through 5 were immersed in a demineralising solution for 16 weeks. In groups 1 (control) and 2 (demineralised/control), conventional acid etching was used. In group 3, sodium hypochlorite (NaOCl) was applied on the enamel surface for 1 min after acid etching, and in group 4, Transbond Plus (3M Unitek, Monrovia, CA, USA) self-etching primer (SEP) was used. The teeth in group 5 were treated with 2% sodium fluoride (NaF) for 4 min before etching. After bracket bonding, the specimens were thermocycled, sealed with nail varnish, immersed in 0.5% basic fuchsine solution for 24 h and sectioned. Microleakage was measured under a stereomicroscope for the enamel-adhesive and adhesive-bracket interfaces of both occlusal and gingival sides.

RESULTS

Demineralised teeth showed more microleakage at the enamel-adhesive interface on both occlusal and gingival sides compared to sound teeth, but the difference was not significant (P>0.005). Treating the demineralised enamel with 5% NaOCl or Transbond Plus SEP was not effective in reducing microleakage. NaF treatment followed by acid etching of demineralised enamel resulted in significantly lower microleakage in most comparisons (P<0.005).

CONCLUSIONS

The use of 2% NaF on hypomineralised enamel before the bracket bonding procedure is an effective way to decrease microleakage.

Evaluation of different enamel conditioning techniques for orthodontic bonding

OBJECTIVE

The aim of this study was to compare the effects of different enamel conditioning techniques for bracket bonding.

METHODS

Ninety-one human premolars were randomly divided in six groups of 15 specimens each. The enamel surfaces of the teeth were etched with 35% orthophosphoric acid in Group 1, with a self-etching primer in Group 2, sandblasted in Group 3, sandblasted and etched with 35% orthophosphoric acid in Group 4, conditioned by Er:YAG laser in Group 5 and conditioned by Er:YAG laser and etched with 35% phosphoric acid gel respectively in Group 6. After enamel conditioning procedures, brackets were bonded and shear bonding test was performed. After debonding, adhesive remnant index scores were calculated for all groups. One tooth from each group were inspected by scanning electron microscope for evaluating the enamel surface characteristics.

RESULTS

The laser and acid etched group showed the highest mean shear bond strength (SBS) value (13.61 ± 1.14 MPa) while sandblasted group yielded the lowest value (3.12 ± 0.61 MPa).

CONCLUSIONS

Although the SBS values were higher, the teeth in laser conditioned groups were highly damaged. Therefore, acid etching and self-etching techniques were found to be safer for orthodontic bracket bonding. Sandblasting method was found to generate inadequate bonding strength.