Evaluation of Microleakage under Orthodontic Brackets Bonded with Nanocomposites.
Background
The aim of this study was to evaluate the microleakage value under orthodontic brackets bonded with a nano-filled composite and to compare the results with a conventional adhesive using two different bonding systems.


Materials and Methods
Forty human premolars were used in this cross-sectional study. The samples were randomly divided into four equal groups of ten: Group I: Acid etch plus Transbond XT primer and Transbond XT adhesive, Group II: Acid etch plus Transbond XT primer and nanocomposite (Filtek Z350), Group III: Scotchbond™ Universal primer plus Transbond XT, and Group IV: Scotchbond™ and nanocomposite. Sections were prepared for microleakage evaluation at the occlusal and gingival margins. Statistical analysis was performed to compare the microleakage values among the groups using analysis of variance (ANOVA).


Statistical Analysis
Microleakage values were analyzed with two-way ANOVA test. Intraexaminer error was evaluated by the Kappa statistic. The level of significance was considered at P < 0.05.


Results
Gingival side displayed statistically higher microleakage (P < 0.001). The nanocomposite Filtek Z350 generally represented higher microleakage when compared with the Transbond XT at both occlusal and gingival sides of the brackets (P < 0.001). More microleakage values were observed in brackets bonded using acid etch compared with Scotchbond. Comparison of microleakage among all the four groups revealed that Group II and Group III had the most and the least microleakage values, respectively, at the enamel-adhesive interface. Microleakage values for groups bonded with nanocomposite were significantly higher.


Conclusion
This investigation clearly reveals the outstanding superiority and efficiency of a Transbond XT adhesive combined with a Scotchbond primer over that obtained using a Filtek Z350 nanocomposite in any combination with the used primers to limit microleakage under bonded brackets.
['Hedayati|Zohreh|Z|', 'Farjood|Amin|A|']
Adhesive margin bonding agent dental leakage nano