The area of the teeth near the gums is still not as white as the rest of the tooth?
Make sure that the bleach covers the entire surface of the tooth and not just the bottom half. The average tooth will usually have a seamless whitening transition from whiter at the bottom of the tooth (biting surface) to less white towards the gum line. This is normal and an expected result. This is due to thinner enamel in this area allowing more show through of the tooth color. Very few cases have total uniform whiteness. With grayish teeth, the transition is occasionally somewhat more noticeable. One might see a demarcation area / line between the 2 areas. Keep in mind that whitening fades and the tooth will in most instances gradually blend. In some cases that are extremely resistant to bleaching, one might consider bonding or veneers as an alternative treatment.
