The Efficacy of Er,Cr:YSGG Laser in Reconditioning of Metallic Orthodontic Brackets

An In-Vitro Analysis of the Surface Treatment of Orthodontic Bracket Bases With Er,Cr:YSGG Laser and Its Effect on Shear Bond Strength

Introduction Shear bond strength is indispensable to prevent the debonding of orthodontic brackets. Lasers have been proven to alter the bond strength of orthodontic brackets, but their efficiency has not been validated in many trials. The study aimed to evaluate the impact of the Er,Cr:YSGG laser on the bases of orthodontic brackets and determine their bond strength with the enamel surface. Materials and methods The Waterlase iPlus (made in the USA in 2012), comprising an Er,Cr:YSGG laser, was used. Based on the surface treatment of brackets, two groups were assigned (n=10), comprising laser-treated and untreated bracket bases. The brackets were treated with the minimum laser intensity (50 Hz, 4.5 W). Then, the brackets of both groups were attached to the labial surfaces of previously extracted premolars, respectively. The shear bond strength of brackets (SBS) was assessed using the universal testing device, and the Adhesive Remnant Index (ARI) was also measured. An independent sample t-test was used to compare the bond strength between the laser-treated and untreated brackets. Results The mean bond strength of laser-treated and control group brackets was 5 MPa and 8.63 MPa, respectively. The laser-treated brackets showed lower bond strength than the control brackets, but the results were statistically insignificant (p=0.23). The ARI analysis stated that bond failures occurred mostly in the region of the bracket and adhesive interface. Conclusion Laser-etched bracket bases showed lesser shear bond strength than the untreated ones, though the difference was statistically insignificant.

The effect of minimally invasive treatments on enamel microhardness and resistance to further demineralization

Objectives: The present study aimed to compare microhardness of inactive proximal lesions treated by resin infiltration, Er:YAG laser + resin infiltration and Bioactive glass, and investigate the resistance of treated lesions to further demineralization challenge. Methods: In this in-vitro study, 30 human molars with inactive proximal lesions were selected and randomly divided into three groups of 10. In group 1 (resin infiltration), the lesions were treated by a resin infiltrant (Icon). In group 2, the surface was conditioned by an Er:YAG laser prior to resin infiltration. The specimens in group 3 were remineralized by bioactive glass. The treated specimens were kept in artificial saliva for 1 week and then immersed in a demineralization solution for 8 weeks. Surface microhardness was measured at baseline (T0), after remineralization (T1) and after exposure to the demineralization solution (T2), and the difference in microhardness between time points (ΔVHN) was calculated. Results: Microhardness after demineralization (T2) was significantly lower than those of other intervals (P0.05). The statistical analysis revealed no significant difference either in ΔVHNT1-T0 or in ΔVHNT2-T1 among the study groups (P>0.05) Conclusion: Pretreatment by the Er:YAG laser prior to resin infiltration was more effective that other treatments in enhancing microhardness and protecting the tooth against acidic challenge. However, the difference between groups did not reach a statistical significance, implying the need for further studies to achieve more conclusive results.

Bond assessment of enamel conditioned with Er, Cr: YSGG laser and methylene blue photosensitizer activated by photodynamic therapy to orthodontic metallic brackets

AIM

To assess bond integrity and failure mode after enamel pretreated with conventional and contemporary conditioning methods were bonded to metallic brackets (MB).

MATERIAL AND METHODS

Forty maxillary central incisors were selected and disinfected. All specimens were mounted up to the cement-o-enamel junction and divided into four experimental groups randomly based on the enamel conditioning technique. Photodynamic therapy (PDT) was used to condition enamel in group 1, Total-etch and rinse (TER) was used to treat samples in group 2, Specimens in group 3 were conditioned with ECL, and samples in group 4 surface pretreated with SEP. Bonding of MB was performed on the surfaces of all the specimens with a Transbond XT. Specimens from all investigated groups were positioned on a universal testing machine maintaining buccal surfaces similar to the direction of the force. After bracket debonding bond failure was assessed using ARI. The bond integrity of all four groups was compared using analysis of variance (ANOVA). Post hoc Tukey test was used for pairwise comparison among different groups.

RESULTS

Group 2, TER+MB (15.38±0.14 MPa) displayed the highest bond value whereas the lowest values of SBS were exhibited by group 1, PDT+MB (10.11±0.17 MPa). The inter-group comparison revealed that specimens of group 2 and group 3, ECL+MB (14.61±0.55 MPa) demonstrated comparable bond strength (p>0.05).

CONCLUSION

Enamel conditioned with TER and ECL demonstrated comparable SBS. However, bond integrity after PDT and SEP (self-etch primer) surface treatment of enamel bonded with MB significantly lowered bond values.

Effect of sandblasting on the shear bond strength of recycled metal brackets: A systematic review and meta-analysis of in-vitro studies

INTRODUCTION AND OBJECTIVE

Sandblasting is an efficient and economic method of rebonding brackets. Literature is divided regarding the Shear Bond Strength (SBS) associated with sandblasted brackets. Hence this systematic review was conducted to obtain conclusive evidence on the same. The aim was to compare the SBS between sandblasted brackets bonded to extracted human teeth and new brackets bonded on extracted teeth that have not been previously bonded.

MATERIALS AND METHODS

The following databases were searched up to April 30, 2021: PubMed via Medline, Web of Science, LILACS, Cochrane, EMBASE and Scopus. Articles comparing SBS of a new bracket with that of a rebonded bracket following sandblasting were included. Two reviewers independently selected the studies, extracted the data and assessed the risk of bias which was based on a modification of the Risk Of Bias In Nonrandomized Studies of Interventions Tool (ROBINS-I). SBS data generated from the systematic review was summarized and a meta-analysis using random effects inverse-generic model was done.

RESULTS

Sixteen studies generated 521 samples for the new bracket group and 391 samples for the sandblasted group. These sixteen studies showed a low risk of bias. Meta analysis reported the mean difference between the SBS of new and sandblasted brackets to be 0.85. (95 CI of -0.24 to 1.94). This difference can be clinically disregarded. The high degree of heterogeneity indicated by an I² of 87% led to a subgroup analysis.

CONCLUSIONS

With the studies showing a high quality of evidence, it can be concluded that sandblasting is an efficient means of recycling debonded brackets without affecting SBS. The inherent deficiencies of in vitro bond strength studies should be borne in mind when making this conclusion. The study protocol was registered on the International Prospective Register of Systematic Reviews (Reg no: CRD42020193616).

The Effect of Fractional CO2 Laser Irradiation on Shear Bond Strength of Resin Cement to Feldspathic Porcelain

Introduction: This study investigated the effect of fractional CO2 laser on shear bond strength (SBS) of resin cement to feldspathic porcelain. Methods: Sixty blocks of unglazed feldspathic porcelain were randomly divided into 5 groups of 12 by treatment. Group 1 and 2 underwent etching with 9.6% hydrofluoric acid (HF) and air abrasion with alumina particles, respectively. In groups 3 and 4, a fractional CO2 laser was applied for 10 seconds using 20 W/10 mJ (group 3) or 15 W/20 mJ (group 4). The specimens in group 5 were first treated by fractional CO2 laser (15 W/20 mJ) and then etched by HF acid. After silane application, a resin cement (Clearfil SA) was poured into plastic molds over the porcelain surface and light cured. SBS was assessed by a universal testing machine and the type of bond failure was determined. Results: Analysis of variance (ANOVA) indicated a significant difference in SBS among the study groups (P<0.001). Pairwise comparison demonstrated that the application of fractional CO2 laser followed by HF acid yielded SBS that was significantly greater than that of the other groups (P<0.05). The SBS of both laser groups (groups 3 and 4) were comparable to each other and significantly lower than the other groups (P<0.05). No significant difference was found in the distribution of failure modes among the groups (P=0.522) Conclusion: The application of fractional CO2 laser followed by HF acid treatment can improve SBS of resin cement to feldspathic porcelain and could be recommended when demanding extra retention.

The effect of surface treatment with a fractional carbon dioxide laser on shear bond strength of resin cement to a lithium disilicate-based ceramic

BACKGROUND

This study investigated the impact of different surface treatments, including fractional carbon dioxide (CO₂) laser on shear bond strength (SBS) of resin cement to lithium disilicate ceramic.

MATERIALS AND METHODS

In this in vitro study, 72 blocks of IPS e.max CAD ceramic were randomly divided into six groups in terms of treatment (n = 12). Group 1 underwent etching with 9.6% hydrofluoric (HF) acid, whereas group 2 was subjected to air abrasion with aluminum oxide particles. Groups 3 and 4 were treated with a fractional CO₂ laser for 10 s using 10 W/14 mJ (group 3) or 20 W/10 mJ (group 4). In groups 5 and 6, the CO₂ laser was applied similar to that in groups 3 and 4, respectively; then, the specimens were etched by HF acid. After silane application, luting cement was bonded to the specimens. The SBS was assessed with a universal testing machine, and the type of bond failure was determined. Data were analyzed by ANOVA, Duncan, and Fisher's exact tests.

RESULTS

Surface conditioning with fractional CO₂ laser alone resulted in significantly lower SBS than HF acid treatment (P < 0.05). Bond strengths of the specimens treated with a combination of laser irradiation and acid etching were significantly greater than all the other groups (P < 0.05). No significant difference was found in the distribution of failure modes among the groups (P = 0.337).

CONCLUSION

The combination of fractional CO₂ laser irradiation and HF acid etching could be recommended when extra retention is required for lithium disilicate-based restorations, whereas laser treatment alone cannot produce sufficient SBS.

The effects of three remineralizing agents on regression of white spot lesions in children: A two-week, single-blind, randomized clinical trial

BACKGROUND

This study investigated the effect of three remineralizing agents on improving white spot lesions (WSLs).

MATERIAL AND METHODS

This clinical trial included children who had at least one WSL on anterior teeth of upper or lower jaws. The participants were randomly assigned to 4 groups by treatment: 1) a cream containing casein phosphopeptide-amorphous calcium phosphate and fluoride (MI Paste Plus); 2) a cream containing hydroxyapatite and fluoride (Remin Pro); 3) a 2% sodium fluoride gel; and 4) usual home care (control). The treatment was performed for 3 times over 10 days using special trays for retaining remineralizing agents. The area and mineral content of WSLs were measured at baseline (T1) and 1 day after finishing treatment (T2). Blinding was applied for outcome assessment.

RESULTS

Eighty patients were assigned to MI Paste Plus, Remin Pro, NaF or control groups. The application of all remineralizing agents caused a significant decrease in area and a significant increase in mineral content of WSLs (p<0.05), whereas the control patients did not experience any significant alteration (p>0.05). At T2, the area of WSLs was significantly lower in three experimental groups compared to the control group (p=0.023), but between-group difference in mineral content of WSLs failed to achieve statistical significance (p=0.08).

CONCLUSIONS

The in-office application of either MI Paste Plus or Remin Pro was as effective as 2% NaF for reducing area and increasing mineral content of WSLs. MI Paste Plus and Remin Pro could be recommended as suitable alternatives to NaF for managing WSLs. Key words:White spot lesion, caries, casein phosphopeptide-amorphous calcium phosphate, hydroxyapatite, sodium fluoride, CPP-ACP, MPlus, Remin Pro, NaF.

Surface treatment with a fractional CO2 laser enhances shear bond strength of resin cement to zirconia

AIMS

The present study investigated the effect of different surface treatments on shear bond strength (SBS) of resin cement to zirconia.

MATERIALS AND METHODS

Ninety zirconia blocks were prepared and divided into 6 groups of 15 by treatment. Group 1 served as the control group, whereas groups 2 and 3 were treated with air abrasion and a universal primer (Monobond plus), respectively. The remaining zirconia copings were treated with a fractional CO2 laser for 10 seconds using 10 W/10 mJ (group 4), 10 w/14 mJ (group 5) or 20 W/10 mJ (group 6). A luting cement (Clearfil SA) was bonded to the treated zirconia surfaces and cured for 40 seconds. SBS was measured with a universal testing machine and the type of bond failure was determined.

RESULTS

There was a statistically significant difference in SBS among the study groups (p<0.001). The highest SBS values were observed in the groups treated with the fractional CO2 laser at settings of 20 W/10 mJ (28.1 MPa) or 10 W/14 mJ (27.4 MPa), followed by the specimens treated with the universal primer (22.8 MPa). The control specimens exhibited the lowest SBS (9.4 MPa) among the study groups (p<0.05). There was no significant difference in the distribution of failure modes among the groups (p=0.871).

CONCLUSIONS

The application of fractional CO2 laser can improve bond strength of resin cement to zirconia ceramic, and thus it could be considered as an appropriate alternative to conventional methods of zirconia surface treatment.

Structural and Morphological Changes in Human Dentin after Ablative and Subablative Er:YAG Laser Irradiation

INTRODUCTION

This study investigated the influence of Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser on microhardness, chemical composition and subsurface morphology of dentin cavity walls.

METHODS

Forty sound human premolars were selected and randomly assigned into four groups. Class V cavities were prepared either with an Er:YAG laser (groups 1 and 2; 15 Hz, 250 mJ for enamel, 10 Hz, 200 mJ for dentin) or with a high speed handpiece (groups 3 and 4). The specimens in groups 1 and 3 served as the control, whereas those in groups 2 and 4 were exposed to subablative laser irradiation following cavity preparation (10 Hz, 50 mJ). After bisecting the specimens, one half was subjected to microhardness assessment and the other half was evaluated by SEM-EDS analysis.

RESULTS

Microhardness was significantly greater in the specimens prepared by both ablative and subablative laser irradiation (group 2) than that of the bur-prepared cavities (groups 3 and 4) (P < 0.05). The quantity of calcium ion was significantly greater in cavities prepared by the Er:YAG laser (groups 1 and 2) compared to that of the bur cavities (groups 3 and 4) (P < 0.05). Subablative irradiation improved microhardness and weight percentage of calcium ion in both laser and bur cavities, but the difference was not significant compared to that of the relevant control group (P > 0.05).

CONCLUSION

Cavity preparation with an Er:YAG laser could be considered as an alternative to the conventional method of drilling, as it enhances the mechanical and compositional properties of lased dentin, especially when combined by subablative irradiation.

A comparative evaluation of the effectiveness of erbium-doped yttrium aluminum garnet laser with other in house refurbishing methods for reconditioning stainless steel and ceramic brackets. An environmental scanning electron microscope and shear bond strength analysis: An in-vitro study

Introduction

Brackets can be recycled by sending them to a commercial recycling company but it is time consuming and the bracket cannot be bonded in the same appointment. Hence in-house methods for recycling of brackets would be beneficial to both the orthodontist and the patient.

Aim

In our study, we compared the shear bond strength of brackets after being recycled with erbium-doped yttrium aluminum garnet (ER:YAG) laser, sandblasting and the thermal method.

Materials and Methods

The study was carried out on 126 extracted premolars. The bonding procedure was performed with mandibular premolar metal and premolar ceramic brackets. Eighty-four teeth were subdivided into three groups for each method of recycling. These groups were further subdivided into two groups of 14 teeth each for the types of brackets used. Prior to the initial bonding the bracket was also viewed under an environmental scanning electron microscope to examine the meshwork of the brackets and once again after the respective recycling methods had been performed.

Results

We found that for stainless steel brackets, the sandblasting method was superior to the ER:YAG laser, as the recycled brackets showed a higher shear bond strength. For ceramic brackets the ER:YAG laser recycled group had the highest recycled shear bond strength therefore was the best method of recycling ceramic brackets.

Effect of multiple debonding sequences on shear bond strength of new stainless steel brackets

Objectives:

This in-vitro study aimed at evaluating the effect of three debonding sequences on the shear bond strength (SBS) of new stainless steel (SS) brackets.

Materials and Methods:

Stainless steel twin brackets (0.022-inch, American Orthodontics, Sheboygan, WI, USA) were bonded with light cure adhesive (Transbond XT, 3M Unitek, St. Paul, MN, USA) to 80 newly extracted human premolars after acid etching with 37% phosphoric acid (30 s). Brackets were debonded with a universal testing machine, and new brackets were bonded to teeth using the same adhesive and same manner. This process was repeated twice, and brackets were debonded within 24 h after bonding. The longitudinal changes of average SBS were assessed with the repeated measures ANOVA. Post-hoc tests using the Bonferroni correction were also used to compare the average SBS at three debonding sequences.

Result:

The mean SBS decreased significantly after each debonding sequence (P < 0.01). The corresponding mean values (standard deviation, 95% CI) after the first, second, and third debonding sequences were 22.88 MPa (4.08, 21.97-22.79), 19.36 MPa (4.54, 18.62-20.64), and 16.67 MPa (4.27, 15.72-17.62), respectively. There was no significant difference among the adhesive remnant index (ARI) scores of three debonding sequences (χ²= 5.067, df = 6, P = 0.53).

Conclusion:

Average SBS after three debonding sequences was significantly decreased, but was above the recommended 5.9-7.8 MPa. In-vivo studies are required to validate the finding of this study.

Comparison of Microleakage under Rebonded Stainless Steel Orthodontic Brackets Using Two Methods of Adhesive Removal: Sandblast and Laser

OBJECTIVES

Debonding is a common occurrence in orthodontic treatment and a considerable number of orthodontists prefer to rebond the detached brackets because of economic issues. The aim of this study was to compare the microleakage beneath rebonded stainless steel brackets using two methods of adhesive removal namely sandblast and laser.

MATERIALS AND METHODS

Sixty human premolar teeth were randomly divided into three groups. Following bonding the brackets, group 1 served as the control group. Brackets in groups 2 and 3 were debonded, and adhesive removal from the bracket bases was done by means of sandblasting and Er-YAG laser, respectively. After rebonding, teeth in each group were stained with 2% methylene blue for 24 hours, sectioned and examined under a stereomicroscope. Marginal microleakage at the adhesive-enamel and bracket-adhesive interfaces in the occlusal and gingival margins was determined. Statistical analysis was done using the Kruskal-Wallis test.

RESULTS

Comparison of the microleakage scores among the three groups revealed no statistically significant difference (P > 0.05). At the enamel-adhesive interface, the gingival margins in all groups showed higher microleakage while in the adhesive-bracket interface, the occlusal margin exhibited greater microleakage.

CONCLUSION

Er-YAG laser irradiation and sandblasting for adhesive removal from the debonded brackets yielded clinically acceptable microleakage scores.

The effect of surface treatment with Er: YAG laser on shear bond strength of orthodontic brackets to fiber-reinforced composite

OBJECTIVES

This study aimed to investigate the effect of surface treatment with Er:YAG laser on shear bond strength (SBS) of orthodontic brackets to fiber-reinforced composite (FRC).

STUDY DESIGN

Ninety human premolars were randomly divided into six groups of 15. FRC bars were bonded to the teeth with a flowable composite (FC) and then underwent following treatments. In group 1 no further treatment was performed. In group 2 the FRC surfaces were covered by FC. An Er:YAG laser was employed to treat FRCs in groups 3 ( 200 mJ/10 Hz) and 4 (300 mJ/15 Hz). The FRC strips in groups 5 and 6 were first covered by FC and then irradiated with Er:YAG laser at 200 mJ/10 Hz (group 5) or 300 mJ/15 Hz (group 6). Stainless steel brackets were bonded to FRCs using a light-cure adhesive system. After 24 hours, the samples were tested for SBS and the adhesive remnant index (ARI) scores were determined.

RESULTS

There was a significant difference in SBS among the study groups (P <0.001). Pairwise comparisons indicated that SBS was significantly lower in group 1 compared to all other groups (p<0.05) except group 2. Bond strength in group 6 was significantly greater than all the study groups (p<0.05) except group 5. No significant difference was found in ARI scores among the groups.

CONCLUSIONS

Covering the FRC surface by a layer of flowable composite and then application of Er:YAG laser at 300 mJ/15 Hz could be recommended to increase bond strength of orthodontic attachments to FRC. Key words:Fiber-reinforced composite, orthodontics, Sshear bond strength, laser, Er:YAG, surface treatment, bracket, FRC.

Microshear bond strength according to dentin cleansing methods before recementation

PURPOSE

The aim of this study was to determine the efficiency of Erbium, Chromium: Yttrium-Scandium-Gallium-Garnet laser in different output powers for removing permanent resin cement residues and therefore its influence on microshear bond strength compared to other cleaning methods.

MATERIALS AND METHODS

90 extracted human molars were sectioned in 1 mm thickness. Resin cement was applied to surface of sliced teeth. After the removal of initial cement, 6 test groups were prepared by various dentin surface treatment methods as follows: no treatment (Group 1), ethylene diamine tetra acetic acid application (Group 2), Endosolv R application (Group 3), 1.25 W Erbium, Chromium:Yttrium-Scandium-Gallium-Garnet laser irradiation (Group 4), 2 W Erbium, Chromium:Yttrium-Scandium-Gallium-Garnet laser irradiation (Group 5) and 3.5 W Erbium, Chromium:Yttrium-Scandium-Gallium-Garnet laser irradiation (Group 6). The topography and morphology of the treated dentin surfaces were investigated by scanning electron microscopy (n=2 for each group). Following the repetitive cementation, microshear bond strength between dentin and cement (n=26 in per group) were measured with universal testing machine and the data were analyzed by Kruskal Wallis H Test with Bonferroni correction (P<.05). Fracture patterns were investigated by light microscope.

RESULTS

Mean microshear bond strength ± SD (MPa) for each group was 34.9 ± 17.7, 32.1 ± 15.8, 37.8 ± 19.3, 31.3 ± 12.7, 44.4 ± 13.6, 40.2 ± 13.2 respectively. Group 5 showed significantly difference from Group 1, Group 2 and Group 4. Also, Group 6 was found statistically different from Group 4.

CONCLUSION

2 W and 3.5 W Erbium, Chromium: Yttrium-Scandium-Gallium-Garnet laser application were found efficient in removing resin residues.

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.

A Comparison of Shear Bond Strengths of Metal and Ceramic Brackets using Conventional Acid Etching Technique and Er:YAG Laser Etching

Background and aims. The aim of this study was to compare shear bond strength (SBS) of metal and ceramic brackets bonded to enamel using acid versus Er:YAG laser etching.

Materials and methods. Eighty premolars were divided into 4 groups: AM (acid etching/ metal brackets), AC (acid etching/ ceramic brackets), LM (laser etching/ metal brackets) and LC (laser etching/ ceramic brackets). Enamel condition-ing was done using acid in AC and AM and Er:YAG laser in LC and LM. Brackets were debonded with a Dartec machine and the SBSs were determined. Adhesive remnant index was evaluated under a stereomicroscope. Two additional teeth were conditioned with acid and laser for scanning electron microscopy examination. Comparisons of SBS value were done by ANOVA test.

Results. statistical analyses showed that SBSs of acid groups were significantly higher than that of laser groups, but dif-ferences between SBS values of AC/ AM and LC/LM were not significant. SEM examination revealed different etching pattern.

Conclusion. Low power Er:YAG laser etching offers clinically acceptable SBS which besides its other superiorities to acid etching can be an appropriate alternative for bonding of ceramic brackets.

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.