Tooth whitening (termed tooth bleaching when utilizing bleach), is either restoration of natural tooth shade or whitening beyond natural tooth shade, depending on the definition used.
Restoration of the underlying, natural tooth shade is possible by simply removing surface (extrinsic) stains (e.g. from tea, coffee, red wine and tobacco) and calculus (tartar). This is achieved by having the teeth cleaned by a dental professional (commonly termed “scale and polish”, see debridement and polishing), or at home by various oral hygiene methods. Calculus is difficult to remove without a professional clean.
To whiten the natural tooth shade, bleaching is suggested. It is a common procedure in cosmetic dentistry, and a number of different techniques are used by dental professionals. Many different products are also marketed for home use. Techniques include bleaching strips, bleaching pen, bleaching gel, and laser tooth whitening. Bleaching methods generally use carbamide peroxide or hydrogen peroxide. There are claims that carbamide peroxide is less effective than hydrogen peroxide, but also has fewer side effects. Common side effects of bleaching are increased sensitivity of the teeth and irritation of the gums. Occasionally individuals develop an unhealthy obsession with tooth whitening akin to body dismorphic disorder, termed “bleachorexia”.
The most common side effects associated with tooth bleaching are increased sensitivity of the teeth and irritation of the gums, which tend to resolve once the bleaching is stopped.
Hypersensitive teeth are caused by open dentinal tubules. Manifest as increased sensitivity to stimuli such as hot, cold or sweet. Tooth sensitivity often occurs during early stages of the bleaching treatment. Potassium nitrate and sodium fluoride are used to reduce tooth sensitivity following bleaching.
Irritation of mucous membranes
Hydrogen peroxide is an irritant and cytotoxic. At concentrations of 10% or higher, hydrogen peroxide is potentially corrosive to mucous membranes or skin and can cause a burning sensation and tissue damage. Chemical burns from gel bleaching (if a high-concentration oxidizing agent contacts unprotected tissues, which may bleach or discolor mucous membranes). Tissue irritation most commonly results from an ill-fitting mouthpiece tray rather than the tooth-bleaching agent.
After teeth bleaching, it is normal to have uneven results. With time, the color will appear more even. To avoid this from happening it is important to avoid making some common post-bleaching mistakes, such as consuming foods and beverages that stain the surface of your teeth.
Return to original pre-treatment shade
Nearly half the initial change in color provided by an intensive in-office treatment (i.e., 1 hour treatment in a dentist’s chair) may be lost in seven days. Rebound is experienced when a large proportion of the tooth whitening has come from tooth dehydration (also a significant factor in causing sensitivity). As the tooth rehydrates, tooth color ‘rebounds’ back toward where it started.
Over bleaching, known in the profession as “bleached effect”, particularly with the intensive treatments (products that provide a large change in tooth colour over a very short treatment period, e.g., 1 hour). Too much bleaching will cause the teeth to appear very translucent.
Damage to enamel
Home tooth bleaching treatments can have significant negative effects on tooth enamel. This is especially the case with home remedy whitening products that contain fruit acids and brushing with abrasives such as baking soda.