When a patients requests to have a brighter and whiter smile, it is important to address the degree of whiteness the pt. is wanting to achieve and if it achievable for them. Everyone’s teeth are different and display different hues of whiteness, grayness, and or yellowness form certain factors such as staining. The origin of the stain is also a very important factor because it tells the clinician what the best bleaching system would be and how long it may take for the pt. to achieve his or her desired whiteness.
Analyzing the stain that the pt. is exhibiting is key to bleaching success. More times than not, the teeth will be stained more at the gingival third due to the thinner enamel and thicker dentin present here. Depending on the type and location of stain, the teeth can be bleached seeing a color change within the first few days, reaching the maximum whiteness in a few months. Other stains such as tetracycline staining can take up to 15 months to reach the maximum whiteness. This can be done with nightly bleaching with a 10% carmamide peroxide solution.
Bleaching cases are not all the same. It is pertinent for the clinician to explain to pt. that the degree of whiteness they want may not be achievable. As a clinician, we do not want to give the pt. false hopes, in the end leaving them disappointed. An interesting fact that can be used when going over the shaded of whiteness, is to explain to the pt. that we are going to try to match your teeth to the whiteness of your sclera of your eyes. This makes for a nice balance of whiteness and brightness to the face.

Source: Haywood B. Van, DMD, Sword J. Rhoda. Inside Dentistry. January 2018. Bleaching Tetracycline-Stained Teeth. Considerations and recommendations for treatment. Pgs. 38-44.