Some contraindications for tooth whitening include:
- Decayed teeth
- Pre-existing filling, crowns or veneers
- People prone to addictions or OCD behaviors
In young teeth, the pulp of the tooth is much larger than in adults. This means that the pulp is much more likely to be irritated. In adults this may lead to some sensitivity. In young people, it may lead to extreme sensitivity or irreversible damage to the pulp.
People with gum and bone recession have exposed root surfaces. These surfaces are much more sensitive than the crown portion of the tooth since they are not protected by an enamel layer.
Whitening decayed teeth is not a good idea since they are much more susceptible to permanent damage.
Pre-existing restorations really aren't a definite contraindication. The problem is that they will not whiten. So after whitening is performed they will likely need to be redone to ensure a uniform coloration.
People that are prone to addictive or OCD behaviors can whiten, but we must be careful that they do not develop a "whitening addiction". Excessive whitening will cause irreversible morphologic changes to the enamel and irreversible damage to the pulp.