The last time i did it was when i first got my braces off my dentist had told me that he would do it for free, so the results that i had were great but it didn't last for very to long.
after getting my teeth zoomed whitened i had a couple of zinger and later on that day, my teeth were throbbing soo badly that i didn't even want to eat or anything all i wanted to do was take pain medication or something. a year later i had gotten the zoom whitening again, which cost me $150.
when i was sitting in the chair getting the zoom whitening done, i didn't get any zingers, i made sure to take some advil before i went in because i didn't want to feel the discomfort. it took longer than 45 minutes, or it felt like it. and after the second time of getting the zoom whitening i had the same throbbing pains in my mouth since when i did it the first time. i couldn't eat or drink nothing cuz it was giving me bad discomfort!!
but ... overall i would recommend Zoom whitening, but i warn you it will give you SENSITIVE ASS TEETH!! .... when i brush my teeth or drink cold or hot stuff ... it tingles baddly!! its been 2 years since i had my last procedure done and i want to get zoom whitening again because i love the whiteness results it gives me. i had called the same dentist and they raised their price up to 250 =( so i donno when i would do it again.