Q: Dr. Mackler, I'm interested in getting my teeth "whiter" - I have been using over-the-counter brands with no success - my sister had her teeth bleached by another dentist and I really didn't see that much of a difference - my questions are: 1) do you feel retail brands should work? 2) what is the difference between what I buy in the store and what you would put on - I know it should be quicker but in the end is it the same result? 3) what about laser? Does it damage your teeth and gums? Thank you for your advise

A: All tooth whitening systems use some type of hydrogen peroxide or carbamide peroxide as the active ingredient. The only real variables in whitening systems are how concentrated the active ingredient is and how long it is kept in contact with the teeth.

Whitening products sold over-the-counter usually contain 3 percent active ingredients. At this concentration, it usually takes a long time to get the desired results. We have had great success using custom-made mouth trays and whitening products with 10 percent carbamide peroxide. These are usually worn at home for a few hours each day or overnight. Good results can be expected in 2 - 3 weeks. Over a 2-week period, the teeth are exposed to the whitening agent for 20 - 30 hours or more which explains why this process will produce better results than a much weaker product kept on the teeth for a matter of minutes.

A new variation on the tray system is Crest Whitestrips. The over-the-counter strips contain 3% carbamide peroxide and are worn for 30 minutes, twice a day. These will definitely produce some color changes after two weeks, especially in teeth that are light to start with. Crest Whitestrips containing 10% or 14% carbamide peroxide are available for purchase at dental offices and will produce much better results in a shorter time due to the increased strength of the whitening agent. The strips do not work well for teeth that have a lot of spacing or are misaligned since the uneven contact of the gel can produce some stripes in these cases. They also will only whiten the front 6 - 8 teeth, which can be a problem if the back ones show in a wide smile and are a much darker shade.

In-office tooth whitening systems all use the same active ingredients as the tray or strip method. Heat or bright light is used to speed up the whitening process so that it may take a few hours in the office versus a few weeks at home. Only the front 6 -8 teeth will be whitened with the in-office systems, and trays for home use will be needed if the back teeth need to be whitened. In-office systems are no more effective than the Crest Professional Whitestrips, but cost approximately 10 times as much since they involve dental chair time, dental staff time and the use of expensive lights or lasers. If used correctly, lasers should not damage your teeth or gums, but they are often used with much stronger whitening agents that may temporarily burn yours lips or gums and may cause some temporary hot and cold sensitivity in your teeth. As you may be able to infer from my answers, I do not provide in-office tooth whitening because I sincerely believe that it provides no appreciable benefits over trays or Whitestrips.

Finally, there are some tooth discolorations, which may not be completely removed with whitening products. In these cases, composite bonding, porcelain laminates, or porcelain crowns may produce better cosmetic results.