Tooth discoloration can be due to many causes. Some medications, dental trauma, root fillings, as well as certain foods and drinks can cause tooth discoloration over time. Some discolorations may be superficial while others are internal. All can be effectively treated by a dentist - professional whitening is the best option to safely lighten discolored teeth.

How does teeth whitening work?
The whitening process is possible due to the ability of the carbamide peroxide and hydrogen peroxide to freely pass through enamel and dentin and to permeate to all parts of the tooth.8 These peroxides break down into oxygen radicals, which migrate between the enamel prisms, breaking down any colored molecules that result in tooth discoloration. The structure of the tooth is not altered; the internal tooth color is simply made lighter.

Whitening agents break down into tiny molecules and move in all directions, so even if the entire tooth is not covered with gel, the entire tooth is whitened²

Numerous studies have proven the effectiveness of peroxides in whitening teeth. Enamel, dentin, existing fillings, and bonding materials are not harmed by the whitening materials.

Does whitening affect adhesion forces?
Although bleaching agents release a large amount of oxygen within the tooth, this does not weaken existing adhesions.^3,4 If bleaching before bonding, please allow 7-10 days after bleaching. The high oxygen concentration in the tooth could significantly and adversely affect the polymerization of the resins.^5,6

How long does the effect of a whitening last?
The results of a teeth whitening are very stable, but depending on the nutritional habits and lifestyle of the patient, the procedure may need to be repeated periodically. Due to the safety of bleaching agents, this should not concern either the dentist or the patient.

Does whitening cause tooth sensitivity?
Tooth sensitivity is a relatively common side effect of whitening. If sensitivity occurs, it is transient and disappears after the completion of the whitening procedure. However, most Opalescence products include PF (potassium nitrate and fluoride) desensitizing agents for additional comfort. Findings have confirmed that the potassium nitrate and fluoride actually help to reduce cavities, minimize sensitivity, increase enamel hardness, and improve the overall health of the teeth. Research has shown that just as hydrogen peroxide penetrates through the enamel and dentin to the pulp, so does potassium nitrate. Potassium nitrate acts more like an analgesic or anesthetic by keeping the nerve from repolarizing after it has depolarized in the pain cycle. Fluoride acts primarily as a tubule blocker, plugging the holes and slowing down the fluid flow that causes the sensitivity.⁷

Will whitening weaken tooth enamel?
Opalescence tooth whitening gel contains PF (potassium nitrate and fluoride). Potassium nitrate has been shown to help reduce sensitivity. Fluoride has been shown to help reduce caries and strengthen enamel. Together they help to improve the overall health of the teeth.^8-12

The best way to whiten is under the supervision of the dentist.
Today, teeth whitening treatments are effective and safe when used properly and with the correct materials. This includes an initial diagnosis, a professional dental cleaning, advice on the selected whitening treatment, and monitoring of the patient during the treatment phase. Self-treatment by the patient with OTC products often does not provide the desired results. Opalescence's whitening product are recommended for whitening discolored teeth prior to placement of composite, veneers, and/or crowns. It is effective in removing some or all internal tooth discolorations due to congenital, systemic, pharmacologic, traumatic, etc., factors as well as aging. It is even successful at resolving staining from fluorosis and tetra​cycline.

^{1. Haywood VB. History, safety and effectiveness of current bleaching techniques and applications of the nightguard vital bleaching technique. Quintessence Int. 1992;23(7):471-88. 2. Jadad E, Montoya J, Arana G, Gordillo LA, Palo RM, Loguercio AD. Spectrophotometric evaluation of color alterations with a new dental bleaching product in patients wearing orthodontic appliances. Am J Orthod Dentofacial Orthop. 2011;140(1):e43-7. 3. Klukowska M, White DJ, Kozak KM, et al. Effect of bleach on microleakage of Class V composite restorations. J Dent Res. 85(Spec Iss B):0035, 2006 (www.dentalresearch.org). 4. Angerame D, Garaffa S, Maglione M, Di Lenarda R, De Stefano Dorigo E. Effect of inoffice bleaching on Class V composite restorations seal. J Dent Res. 84(Spec Iss A):3013, 2005 (www.dentalresearch.org). 5. Wilson D, Xu C, Hong L, Wang Y. Effects of clinical factors during tooth whitening on enamel. J Dent Res. 86(Spec Iss A):2632, 2007 (www.dentalreasearch.org). 6. Lim B-S, Ryu I, Lee Y-K, et al. Effect of bleaching agent on shear bond strength to dentin. J Dent Res. 85(Spec Iss B):0036, 2006 (www.dentalresearch.org). 7. Haywood VB. A comparison of at-home and in-office bleaching. Dentistry Today. 2000; 19(4):44-53. 8. Basting RT, Rodrigues AL Jr, Serra MC. The effects of seven carbamide peroxide bleaching agents on enamel microhardness over time. J Am Dent Assoc. 2003;134(10):1335-42. 9. Al-Qunaian TA. The effect of whitening agents on caries susceptibility of human enamel. Oper Dent. 2005;30(2):265-70. 10. Clark LM, Barghi N, Summitt JB, Amaechi BT. Influence of fluoridated carbamide peroxide bleaching gel on enamel demineralization. J Dent Res. 85(Spec Iss A):0497, 2006 (www.dentalresearch.org). 11. Amaechi BT, Clark LM, Barghi N, Summitt JB. Enamel fluoride uptake from fluoridated carbamide peroxide bleaching gel. J Dent Res. 85(Spec Iss A):0498, 2006 (www.dentalresearch.org). 12. Browning WD, Myers M, Downey M, Pohjola RM, Brackett WW. Report on low sensitivity whiteners. J Dent Res. 85(Spec Iss A):1650, 2006 (www.dentalresearch.org).}