Invisalign® uses a series of removable aligners to straighten the teeth. The average number of aligners is usually between 18-30. Each aligner is worn for 22 hours per day and removed only to eat, drink, brush and floss. Each aligner is worn for 2 weeks then it is replaced by the next aligner in the series. This new aligner will be shaped slightly differently from the previous one and will continue the tooth straightening process.