Shear Bond Strength Of Metal Brackets Research Articles

Effect of Different Desensitizer Treatments on the Shear Bond Strength of Orthodontic Metal Brackets Following In-Office Bleaching: An In Vitro Study.

One of the adverse effects of in-office bleaching is tooth hypersensitivity, which could be neutralized with a desensitizing agent. In-office bleaching and the application of desensitizing agents will affect the morphology of the enamel surface. These morphological changes have potential effects on the shear bond strength (SBS) and bonding of orthodontic brackets. This study analyzed the effects of fluoride and nonfluoride desensitizing agents after in-office bleaching on the SBS of metal brackets with resin composite cementation. Twenty-seven postextraction premolars (n = 27) were bleached with 37% hydrogen peroxide and then divided into three groups: control group (group 1), fluoride-based desensitizing agent (group 2), and nonfluoride-based desensitizing agent (group 3). After treatment, the brackets were bonded using Transbond, and then the SBS test was performed using a universal testing machine. The adhesive remnant index (ARI) was analyzed after the SBS test, whereas enamel morphological changes were observed under a scanning electron microscope. After this assessment, energy-dispersive X-ray spectroscopy was conducted to determine calcium and phosphorus elements in the enamel surface after treatments. SBS data were analyzed using the one-way analysis of variance, followed by the Tukey test, whereas ARI scores were subjected to the Kruskal-Wallis test and the Mann-Whitney test with a significance level of 5%. The SBS increased significantly in group 2 compared with groups 1 and 3 (p < 0.05). In group 2, an ARI of 2 (55.56%) was frequent, whereas in group 3, an ARI of 3 (55.56%) appeared most frequently. The application of the desensitizing agent fluoride after in-office bleaching increased the SBS and more adhesive remains on the tooth surface compared with that when nonfluoride desensitizing agents were applied on metal brackets with composite resin cementation.

Contrary to an old belief, four corner curing does not provide more bond strength or polymerization in bonding of orthodontic metal brackets

Objectives: The study aimed to investigate the effect of the direction of light curing on bond strength and adhesive polymerization of orthodontic metal brackets. Material and Methods: In this in vitro investigation, 75 extracted human upper premolars were randomly divided into three groups according to the curing direction: Group A (20 s curing from the occlusal side of the bracket), Group B (10 s from occlusal and 10 s from gingival), and Group C (5 s from four corners of the bracket). After bonding, the brackets were subjected to a shear bond strength (SBS) test performed with a universal testing machine. Moreover, Fourier transform infrared spectroscopy (FTIR) analysis was used to find the polymerization ratio of the adhesives in each group. Kruskal–Wallis test was to statistical analysis of SBS and FTIR data, respectively, at the 0.05 level of significance. Results: The difference in SBS of metal brackets was not statistically significant between the groups (P &gt; 0.05). However, the difference in polymerization ratio was significant between all groups where the highest and lowest ratio belonged to Groups A and B, respectively (P &lt; 0.05). Conclusion: Curing metal brackets from four corners do not increase their bond strength and/or polymerization.

Effects of blood and saliva contamination on shear bond strength of metal orthodontic brackets and evaluating certain methods for reversing the effect of contamination

The background and purposeContaminations may reduce shear bond strength (SBS) of orthodontic brackets. For reversing such effects, certain surface treatments are suggested. This study was conducted to evaluate (1) effects of saliva and blood contamination on SBS of metal brackets, (2) the efficacy of three surface treatments, while (3) using two adhesives (37% phosphoric acid etchant (Ivoclar/Vivadent)+RMGIC (Fuji Ortho LC), and self-etchant primer (iBonD GI)+composite resin (No-Mix, Dentaurum)). MethodsThe sample was categorized into 12 experimental subgroups (2 contaminations×3 treatments×2 adhesives, n=12×10) and 2 control subgroups (n=2×10). Experimental specimens underwent different treatments according to their group. They were incubated (37°C, 96h) and thermocycled (3000 cycles, 5–55°C, dwell time=30s). SBS was tested at 1mm/min crosshead speed. ResultsSEP–composite produced significantly lower SBS rates (P<0.05) according to Mann–Whitney. ANOVA indicated a significant difference between blood contamination and both control and saliva contamination. According to Wilcoxon signed rank test, comparing with SBS=7, drying failed to achieve appropriate SBS rates (except drying saliva when using RMGIC). On RMGIC, re-etching and rinsing–drying methods might provide sufficient SBS levels. All treatments (except rinsing–drying saliva contamination) did not produce appropriate SBS levels when using SEP–composite. ConclusionsBlood contamination reduced the SBS much greater than saliva. Using etchant–RMGIC is strongly recommended. Drying may only suffice when RMGIC is used over saliva contamination. The efficacy of re-etching depends on the etchant type. Rinsing–drying may produce appropriate SBS levels.

Shear bond strength of metallic brackets bonded with four different composite resins

The objective of this study was to assess the shear bond strength of metallic brackets with different types of Concise composites and the Adhesive Remnant Index (ARI). Sixty bovine permanent lower incisors were inserted into PVC tubes and divided into four groups (n = 15): Group 1 – Transbond XT (control) composite; Group 2– Concise restorative composite; Group 3 – Concise diluted restorative composite (Artun and Zachrisson's technique); and Group 4– Concise Orthodontic composite. After bonding the brackets, the samples were stored in distilled water at 37° C for 24 hours and then submitted to shear strength tests (Instron) at a crosshead speed of 0.5 mm/min. Analysis of variance and Tukey's test (5%) were used for statistically analysing the data regarding the shear bond strength results, whereas Kruskal-Wallis test was used for analysing the ARI scores. The shear bond strength mean values (MPa) for Group 1 (12.13) and Group 2 (12.20) were found to be statistically higher (p < .05) than that for Group 3 (8.20). No statistically significant differences were observed (p > .05) between Groups 1, 2, and 4 (9.86) as well as between Groups 3 and 4. Regarding the ARI evaluation, the majority of the fractures involved the bracket/ composite interface.