Comparison of tensile bond strength of new and rebonded Symetri Clear™ ceramic brackets with Transbond™ XT or BluGloo™, with or without surface treatment: An in vitro study

A novel orthodontic adhesive containing zinc-doped phosphate-based glass for preventing white spot lesions

OBJECTIVES

This study aimed at demonstrating the remineralization effect of the enamel around the brackets to aid reduction in white spot lesions (WSLs) with use of zinc-doped phosphate-based glass (Zn-PBG) containing orthodontic adhesives.

METHODS

Zn-PBG powder was synthesized, and particle morphology, size, and density were evaluated. Orthodontic adhesives with increasing loading percentage of Zn-PBG powder were prepared: ZnPG3 (3 wt.%), ZnPG6 (6 wt.%), and ZnPG9 (9 wt.%). Brackets were bonded on the etched enamel surface and stored in distilled water (DW) for 1 h. Following, Shear bond strength (SBS) along with adhesive remnant index were analyzed. The release of calcium (Ca), phosphorus (P), and zinc (Zn) from adhesive specimens in DW was evaluated after 7, 15 and 30 days of immersion. The remineralization effect was confirmed by microhardness and surface morphology analysis with scanning electron microscopy.

RESULTS

The SBS value was observed between 20 and 22 MPa on enamel surface. The concentration of Ca, P and Zn released in DW increased with loading percentage of Zn-PBG. The microhardness increased in the experimental groups after immersion in artificial saliva for 7 days. Apatite-like crystal formation was observed after 30 days in the ZnPG 9 group.

CONCLUSIONS

The orthodontic adhesive containing Zn-PBG with an optimal SBS performance has an enamel remineralization effect, and therefore can aid in prevention of WSLs.

CLINICAL SIGNIFICANCE

The orthodontic adhesive containing Zn-PBG is clinically advantageous as it can promote remineralization and resist the formation of WSLs that may occur during orthodontic therapy.

Reliability of qualitative and quantitative assessment of adhesive remnants after debonding of ceramic brackets bonded with Transbond™XT on human molar teeth: An in vitro study

OBJECTIVE

To test the hypothesis that there are any differences between qualitative and quantitative methods of adhesive remnants index (ARI) scores on the buccal surfaces of the upper molar.

MATERIALS AND METHODS

The study included 34 upper first human molars. After etching for 20seconds by using 35% orthophosphoric acid (Ultra-Etch, Ultradent Products Inc., USA) and then rinsed with distilled water for 15seconds, the adhesive (Transbond™XT, 3M™, USA) was applied and cured with the polymerization lamp (Bluephase Style, Ivoclar Vivadent, Liechtenstein) for 10seconds. Ceramic brackets (Damon® Clear™, Ormco, USA) were placed by composite (Transbond™XT, 3M™, USA) on the buccal surface of the molars. Following 24-hour storage of the samples in distilled water (WB-12, Phoenix Instrument, Gabsen, Germany) at 37°C, the brackets were debonded using a debonding plier (Damon Clear Debonding Plier, Ormco, USA). ARI and a modified ARI-scoring system were used. Three independent observers scored the ARI with the naked eye under 10x, 20x, and 32x magnifications using Stereomicroscope Stemi DV4 (Zeiss, Germany). Afterward, the digital microscope VHX-5000 (Keyence, Japan) under 50x magnification was used for the quantitative analysis of the adhesive remnants by just one evaluator. The Fleiss' Kappa-coefficient test was used to assess interrupter reliability.

RESULTS

Fleiss' Kappa-coefficient test show that the highest amount of agreement between observers is observed using the naked eye for both of the scoring methods P<0.001. Increasing the magnification led to the moderate decrease of inter-observer agreement. For evaluations with naked eye, a higher agreement is observed for the modified ARI score compared to the ARI scored. The agreement between the quantitative and qualitative evaluation of the ARI score rose with increasing magnification.

CONCLUSION

The assessment of adhesive remnants should be done either with naked eye or under 10x magnification, as they showed the highest rate of intra-observer agreement.

Evaluation of Different Adhesive Resin Removal Methods after Debonding Ceramic Orthodontic Molar Tubes: A Scanning Electron Microscope Study

OBJECTIVES

To evaluate and compare the impacts, bond strength, residual adhesive, and time invested on the enamel surface after debonding of recently introduced ceramic buccal molar tubes with different systems.

MATERIALS AND METHODS

Ceramic molar tubes were bonded to fifty-four maxillary molar teeth, and a shear bond strength (SBS) test was performed. The adhesive remnant index (ARI) scores were recorded, and the samples were divided into two groups for adhesive removal with low-speed instruments: tungsten carbide bur or diamond-coated micropolisher point. The time to clean the enamel surfaces was also noted down for each tooth. The enamel surfaces were investigated with scanning electron microscope (SEM) after adhesives were cleaned. Shapiro-Wilk's, Kolmogorov-Smirnov's, and Student's independent t tests were used for statistical analysis.

RESULTS

The mean SBS value of the tested ceramic molar tubes was 9.78 ± 1.85 MPa, and the majority of the samples were scored as ARI 1 and ARI 2. No statistically significant difference between PoGo micropolisher and TCB was found in terms of time values for surface cleaning. The enamel surface characteristics of TCB for adhesive remnant removal resulted in a better enamel surface than the single-step diamond polisher when the samples were investigated by using SEM.

CONCLUSIONS

Ceramic molar tubes may be an enamel-safe product for patients seeking for fully aesthetic orthodontic treatment, if used in carefully handled clinical conditions. One-step polishing systems utilised with low-speed instruments could be used confidentially for cleaning the resin remnants on enamel after orthodontic treatment.

Shear Bond Strength and Bracket Base Morphology of New and Rebonded Orthodontic Ceramic Brackets

The objectives of this study were to (1) to evaluate the shear bond strength (SBS) of two ceramic brackets when new and when rebonded following various bracket base conditioning methods, and (2) to determine bond failure mode relative to bracket base morphology. 100 Symetri Clear^TM (SC) and 100 Radiance Plus^® (RP) ceramic brackets were bonded to bovine incisors and divided into five groups: one group served as controls and four had brackets rebonded following conditioning by: no surface treatment, sealant, sandblasting, and flame then steam. SBS, adhesive remnant index, and bracket base morphology were evaluated. SBS showed no statistical difference between new and rebonded with no surface treatment or sealant (SC brackets) and with sealant or flame and steam (RP brackets). When comparing SC to RP, SBS was higher with SC, no surface treatment, and sandblasted groups. All groups had varying amounts of adhesive left on the tooth, with the sandblasted group having the most. SEM analysis showed that sandblasting damaged the retention features of bracket bases. In conclusion, when rebonded, the SBS of SC brackets that had no surface treatment and both SC and RP brackets that had sealant showed no significant differences to new brackets. Sandblasting damaged the retention features of SC and RP bracket bases, resulting in low SBS.