Different types of dental braces are used to correct the position of teeth over time according to the particular orthodontic problem such as crooked, crowded or protruding teeth. Invisible braces refers to either lingual braces or clear aligners which are alternatives to traditional metal braces. To avoid the social stigma often associated with traditional braces, many adults and teenagers are now considering invisible braces. Lingual braces are similar to traditional braces, but are instead fitted behind the teeth so they are not seen when a person smiles or talks. Clear aligners, including Invisalign® are similar to a mouth guard and grasp both the front and back of the teeth; they are completely removable. The best candidates for invisible braces are adults or older children who possess excellent oral health. Lingual braces can treat severe orthodontic conditions but Invisalign and other clear aligners are usually only ideal for those people with mild to moderate orthodontic conditions. The cost of lingual braces is between £3,000 and £5,000. Clear aligners are often more expensive, costing anywhere between £3,000 and £7,000.