The main disadvantage of any whitening technique is the sensitivity of some patients to hot and cold during bleaching. Some people experience toothache or sore gums. There are also side effects of teeth whitening such as chemical burns, sensitive teeth and over-bleaching.
People with receding gums, sensitive teeth or sensitive gums should discuss the applying of teeth whitening with the dentist. Also, anyone allergic to peroxide, bleaching product used for whitening the teeth, should avoid the process. Some patients can retch when wearing trays.
Most importantly, the excessive use of bleaching agents may cause damage to the tooth enamel. Excessive use of whitening agents by some patients makes teeth look translucent. Also, some tooth discolorations are more stubborn and can’t be lightening enough with at home kits alone.
Basically in most cases the pros outweigh the cons in home tooth whitening kits. Every procedure depends on individual person. It just really depends on your teeth and the product you use. While you may not achieve radical improvement you will get some positive results.