A Molar Band (also called an Orthodontic Band) is a metal ring that is placed around a tooth (usually a Premolar or a Molar) to hold on parts of your braces. Molar Bands provide a solid anchor to an Arch Wire. They also give Orthodontists an area to attach additional appliances if necessary, such as Headgear.
In the old days, a Band was wrapped around every tooth to secure the orthodontic Brackets. When modern direct bonding with adhesives became possible in the mid-1970s, Orthodontists found that they no longer needed to place a Band on every tooth. At that point, they began using them mainly on Molars and other posterior teeth.