Tooth sensitivity affects the majority of those who whiten their teeth to some degree; for most it’s mild, but for others it can be more intense. The degree of discomfort while whitening sensitive teeth is dependent on two variables:
1) saliva flow in the mouth and
2) the condition of the tooth’s enamel.
Whitening products can cause temporary tooth sensitivity. As the whitening gel undergoes its natural process from active to inactive, the tubules (pores) in the tooth are left open and exposed, resulting in tooth dehydration. When the tooth dehydrates the dentin (inner layer) shrinks inward applying pressure to the nerve resulting in discomfort. The tooth will remain sensitive until the pressure is relieved from re-hydration. Natural re-hydration occurs through saliva production over the course of several hours; however it may take up to 48 hours for those with low saliva flow (dry mouth).
During the 1-2 weeks you’re using teeth whitening products it is important to avoid/minimize consumption of foods and drinks containing color, sugar, or acid. When the tubules in the tooth are open and exposed the tooth will very easily re-stain. The same applies to sugars and acids which will increase the risk of decay.
For most, tooth sensitivity onsets several hours after whitening which means there is time to prevent the discomfort by using a post whitening application known as desensitizing (remineralization) gel.
After each tooth whitening application you will rinse and dry your teeth whitening trays; then proceed by applying the desensitizing gel to the trays. Wear the loaded trays for 5-10 minutes, remove the trays and spit out the excess desensitizing gel, but do not rinse because the saliva helps the tooth absorb the gel. As the desensitizing gel slowly flows into the open tubules the tooth will quickly re-hydrate thus preventing your teeth from becoming sensitive. For those with more extreme sensitivity it may not prevent it 100%, but it will dramatically reduce the level of discomfort as well as shorten its duration.