Bleaching agents were first released in the United States in the 1990s, containing lower concentrations of hydrogen peroxide or carbamide peroxide, directly sold to consumers for home use.

The present-day bleaching technique normally uses different concentrations of hydrogen peroxide, between 15% and 40%, with or without light.

Types of dental stains/discoloration

Many color-related issues can affect the teeth appearance and the causes vary, as well as the speed with which they can be removed. The causes of tooth coloring must be carefully assessed for a better prediction of the success rate and the degree to which the bleaching will improve the tooth color, given that some stains surrender themselves more easily to the bleaching process than others. Discoloration may be extrinsic or intrinsic.

Extrinsic stains

Extrinsic stains are often the byproduct of the accumulation of chromogenic substances on the tooth’s outer surface. Extrinsic color changes may occur due to poor oral hygiene, food intake and chromogenic beverages, as well as smoking habits.

The retention of these chromogenic elements takes place when the proteins found in the saliva connect themselves to the enamel surface through calcium bonds, forming a layer.

Intrinsic stains

Intrinsic stains are often caused by deeper internal blemishes or enamel defects. They are caused by aging, food and chromatic beverages, smoking, tetracycline-based medication, excessive fluoride intake, severe jaundice during childhood, dental caries, restorations and the enamel layer thinning.

Aging is a common cause of discoloration. Over time, the dentine tends to darken due to the formation of a tissue known as secondary dentin, which is darker and opaquer than the original dentin, thus making the dental enamel thinner and the dentin’s darker color more visible.

Tooth bleaching mechanism

Bleaching products used in the office or at home have hydrogen peroxide or carbamide peroxide as the active component, in concentrations ranging from 3% to 40%.

The hydrogen hydroxide activation is achieved using light or lasers, which leads to the formation of hydroxyl radicals from the hydrogen peroxide, and these have proved to be capable of increasing the bleaching potential, providing faster results.

Some bleaching products include calcium phosphate to reduce sensitivity, reduce the enamel demineralization through a post-bleaching remineralization process and increases the brightness of teeth.

Clinical Bleaching

This bleaching technique uses a high concentration of bleaching agents, hydrogen peroxide between 25-40%. This bleaching technique is safer, since the dentist has complete control over the procedure and the ability to finish it when the intended shade/effect is achieved.

In this bleaching technique, different types of activating lights (halogen light, plasma globe, Xe-halogen light, laser diodes or metal-halide light) can be used to activate the bleaching gel or accelerate the bleaching effect.

Ambulatory bleaching (at home)

Home bleaching has the following benefits: self-administration by the patient, shorter office time, a high degree of safety, lower cost. Nevertheless, the overall outcome of this technique is not always that efficient, since it requires responsibility from the patient, something that often fails.

Some doctors recommend a 35% concentration of hydrogen peroxide for in-office tooth bleaching, whereas ambulatory bleaching (home-made) relies on concentrations of 10%, 15% or 20% of carbamide peroxide.

There are also several over-the-counter bleaching products, which are sold in supermarkets or in teleshopping ads, whose popularity has increased in recent years. These products contain a low concentration of the bleaching agent (3 to 6% of hydrogen peroxide). These bleaching agents can be highly questionable from a safety standpoint, since some are not regulated by the Food and Drug Administration (FDA).

Effects of the bleaching process

Effects on the soft tissues (gums)

The most potent in-office bleaching (30-35% of hydrogen peroxide) can easily produce soft tissue burns, making the tissue white. Generally, these tissue burns are reversible, with no long-term consequences, if the exposure to the bleaching material is limited in time and amount.

Rehydration and the use of an antiseptic gel lead to a quick recovery of the original tissue color. It’s very important to protect the soft tissues with a rubber dam or other measures to avoid tissue burn.

Furthermore, soft tissue irritation has been reported with home bleaching. That irritation is probably due to an ill-adjusted bleaching tray, and is not associated with the bleaching agent itself.

Systemic effects

The concern involved with ambulatory bleaching agents is greater, due to possible adverse effects, although their concentrations are much lower than in-office bleaching agents, since these are controlled by the dentist.

Occasionally, patients report irritation of the gastrointestinal mucosa, including burnt palate and throat and tiny disturbance in the stomach or intestines. Nevertheless, most reports in the literature concluded that the use of low concentrations of hydrogen peroxide in tooth bleaching is still safe.

Effects of tooth bleaching on the tooth structure:

The most recent studies assessed changes in the micromorphology and microhardness of the enamel surface after bleaching with two different concentrations of hydrogen peroxide and carbamide peroxide, using bleaching gel containing 10% or 35% of carbamide peroxide or 3,6% or 10% of hydrogen peroxide, respectively, for two hours every second day, throughout a 2-week period. It was possible to conclude that the application of carbamide peroxide and hydrogen peroxide showed only tiny quantitative and qualitative differences, in other words, they do not negatively alter the tooth surface in an impactful way.

Dr. Tiago Ribeiro

Dr. Tiago Ribeiro

Graduated in Dental Medicine in 2007 at the I.S.C.S.E.M. – Monte de Caparica – Portugal

Registered in the O.M.D. – Portugal (the Portuguese correspondent with the British General Dental Council) since August 2007

Private Practice in Oral and Aesthetic Complex Rehabilitation (Implants and Teeth)

Clinical Director of the Center for Aesthetics and Oral Rehabilitation of Lisbon – C.E.R.O. – Almada

Responsible for the Department of Oral Rehabilitation of the Center for Aesthetics and Oral Rehabilitation, Lisbon and Almada

Plastic –Esthetic Periodontal and Implant Surgery – University Complutense Madrid

Orthodontic and dental-facial Orthopedics – International Institute of Medical & Dental Science

Guest monitor of Biophysic in Dentistry Course in ISCS – Egas Moniz in years 2005/2006 and 2006/2007.

Advanced course in Botulinum Toxin (Botox) and Hyaluronic acid injections – Med – Estetic Madrid

Clinical Review in Occlusion Assessment

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