A. The zoom whitening you had done has one large draw back, as the procedure is being done the teeth before dehydrated, this makes the teeth appear whiter. once the teeth have rehydrated this causes a rebound and makes the teeth look slightly yellower again. the zoom treatment needs to be followed up with a home treatment to make sure the results are satisfactory. there are no long term side affects with zoom whitening. The better system on the market is called enlighten which works by two weeks at home with some trays you wear through the night. and then a one hour in surgery treatment. this i have found gives very good results and is consistent. hope this is helpful.