In order to practice, all orthodontists must be licensed by their state. To receive a dental license, candidates must graduate from an accredited dental school, successfully complete the written National Board Dental Examinations and pass state clinical tests.
The world's tallest artificial structure is the 829.8 m (2,722 ft) tall Burj Khalifa in Dubai . The building gained the official title of Tallest Building in the World and the tallest self supported structure at its opening on January 9, 2010. The second tallest self-supporting structure and the tallest tower is the Tokyo Skytree. The tallest guyed structure is the KVLY-TV mast.
The Pentagon was the world's largest office building for a while. The Vehicle Assembly Building, where NASA puts together its rockets, is pretty amazing. It was built in 1966 and was only supposed to last 10 years. It's still in use. Burj Khalifa is currently the tallest man-made structure in the world. You might find this list interesting: List of largest buildings in the world.