Purpose: To Evaluate the accuracy of the slot size dimension of 0.022-inch slot pre-adjusted MBT bracket system of three different companies.

Methodology: A total of 33 upper left central incisor brackets were divided into 3 equal groups according to their manufacturing companies; (Dentaurum, American Orthodontic and Leone), then they were prepared to be scanned under SEM.

Results: When compared to the standard MBT prescribed values, (Dentaurum) showed the least variance in slot height of the samples, and (American Orthodontics) showed the most variation. For the slot depth, (Dentaurum) had shown least variation and (American Orthodontics) displayed the most variation. Nearly all of the brackets, when assessed for slot depth, were undersized.

Conclusion: It was concluded that the examined brackets' real dimensions differed greatly from what the companies have stated. Between various bracket systems, there was a significant difference in the slot dimensions. In vivo studies are recommended to analyze the clinical impact of the inaccuracies found in the bracket dimensions.