1 If X is a topological (or metric) space and M is a metric space, then the set of all bounded continuous functions from X to M forms a metric space if we define the metric as above: d (f, g) = sup x in X d (f (x), g (x)) for any bounded continuous functions f and g.
Invisalign is orthodontic appliance, so since orthodontic treatment is allowed as an FSA expense, Invisalign is covered. Different companies have different rules concerning amounts set aside and the timing of how funds are used for orthodontics.
Many general dentists perform orthodontic treatment routinely, even though they have not completed residency training in Orthodontics and Dentofacial Orthopedics nor are they board certified. Because of this, it is important for patients to determine if they should receive their orthodontics treatment from a general dentist or an orthodontist.