The fluid inside the dentinal tubules causes sensitivity when moved. The minerals found in saliva play an important role in preventing this fluid to move by creating protective plugs. Unfortunately, these plugs do not resist in contact to any bleaching substance and cause tooth sensitivity.
Sensitivity caused by Acid reactions
This type of tooth sensitivity is the most common one among patients who use bleaching products. Small dental problems such as cracks, chips or decay as well as a stressful life and improper alimentation (sodas, candy, and too many acid fruits) attack the tooth enamel. From this point access becomes easy for acids to invade and destroy the saliva plugs that cover the ends of the dentinal tubules. To avoid that, a good diet combined with a good hygiene is recommended. Periodic visits to the dentist will keep anyone safe from dental trouble.
Sensitivity caused by bleach stability
Bleaching gels or other similar products have to be really strong to actually have any result on making teeth whiter. However, each person has different teeth sensitivity and applying a general bleaching formula can't always be perfect for everyone. The blending, storage or shipping operations of the bleaching gels also have a strong influence on how the bleaching problem is going to react on a patient's teeth. Most manufacturers go for applying a mid strong bleaching formula because it involves fewer risks than delivering a too weak or too strong product. The desired result is a self stable bleaching gel or powder with a neutral pH, but that is most of the times hard to obtain.
So if the bleaching product is too acid, the little protective plugs within the tooth tubules dissolve causing teeth sensitivity. Dentists advice their patients to avoid over-the-counter bleaching products because the risks they expose themselves at are sometimes irreparable.
Fair haired and fair skinned individuals seem to have developed a higher risk of teeth sensitivity, but complications may occur to anybody who has tooth problems regardless of age, sex or race. It is highly recommended to patients to go through a thorough dental examination before paying for a tooth bleaching treatment. Some people can never be good candidates for bleaching their teeth although a good oral hygiene, healthy diet and saying 'no' to smoking always help.