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.
Sometimes orthodontists may start you with a bonded retainer, and switch you to a Hawley or Essix retainer after six month to one year. It can be very difficult to floss the teeth which are bonded; you will need to use Threader Floss to do it correctly. Pros Retains teeth well. Cannot be seen by other people.