No matter how fastidious a person is, the teeth will always change its appearance and color. The youthful glow and sparkle of young teeth will in time lost its sheen as the enamel starts developing tiny cracks that will eventually lose the crystalline rods in the tooth, thinning the enamel making the teeth more transparent and showing through the yellowish color of the dentin. Even discounting this natural aging of the teeth, eating habits, food choices, medication, lifestyles, health conditions and many other factors will develop the tiny cracks in the enamel allowing debris to accumulate between the spaces staining the teeth.
Extrinsic staining and intrinsic staining are the two basic types at which the teeth develop stains and discoloration.
Extrinsic stains are developed in the surface of the teeth that resulted from the accumulation of food debris and color. While superficial stains and discoloration could be removed by prophylactic cleaning and brushing, there are stains that are a little more stubborn and could accumulate between the spaces of the tiny cracks in the tooth that would need bleaching to remove the stains. When the stains are not effectively removed and stays on the teeth for a period of time, this could penetrate deeper into the dentin which could require more involved methods.
Those stains that form beneath the enamel are intrinsic stains. Previously, intrinsic stains are believed to be resistant to treatments although today most of it could be removed with close supervision from qualified professionals. Intrinsic stains are caused by the natural process of aging, trauma to the tooth, exposure to drugs containing tetracycline and flourosis.
Other factor that stains the teeth is grinding. Grinding often attributed to stress accelerates micro cracking of the tooth enamel that will hold tiny debris to be accumulated. It also causes the edges of the tooth shade darker, faster. Another big factor is smoking. Nicotine is brownish in color that could stick in the enamel of the tooth and even soak in its structure causing internal discoloration. Red wine may be good for the heart but it contains a high concentration of tannins that causes staining fast.
DNA. All teeth are translucent to some degree. There are people though that are born with teeth that are more translucent than most. Teeth that are more translucent tend to show more staining than those with more opaque teeth.
Teeth transparency is the only known teeth condition today that could not benefit from teeth whitening and teeth bleaching. On the other hand, no amount of teeth bleaching will whiten teeth more than its natural color. In some cases, it could artificially be done but never recommended.
No matter how teeth whitening and bleaching is done, anything involving cosmetic enhancements and restoration is subjective that varies from person to person. There will always be limits to this that are often the cause of the feeling of well being or disappointment.
A good point therefore before any teeth whitening and bleaching is done is ask a realistic assessment from the dentist.