The average range of time that Invisalign treatment takes to straighten teeth is between 9 and 18 months. This is comparable to the time that braces take to achieve the same results, but sometimes braces take a bit longer, reaching 2 or 3 years for some patients. The reason for the difference is that Invisalign works for many patients, but not necessarily for everyone. If you or your child need extensive corrections or have certain needs that extend beyond the average, Invisalign may not be an option.