Hi. Teeth whitening is completely a cosmetic procedure and is going to last only for some time like 6months to 1 year or little more than that and then you might have to repeat.there are two types of bleaching systems... Office bleach and home bleach. Office bleach.. Is done in the dental clinic. It gets over in 45 minutes time and the results are good.. But remember if u already suffer from teeth sensitivity issues. This can further aggravate sensitivity. So the dentist will check n decide if you are a suitable case for office bleaching. Home bleach on other hand... Here a customised bleaching tray is made for patient and patient can do the procedure at home. But it takes almost 2 weeks time. Results would match or sometimes a little less than office bleaching systems. This system might cause less or no sensitivity at all. Cost might vary depending on type of system and the product we use