Teeth Whitening and Bleaching
Tooth whitening or tooth bleaching is the process of lightening the color of human teeth or removing the internal stains. Whitening is often desirable when teeth become yellowed or stained over time for a number of reasons, and can be achieved by changing the intrinsic or extrinsic color of the tooth enamel. The chemical degradation of the chromogens within or on the surface of the tooth is termed as bleaching.
Staining Or Discoloration Of The Teeth
The staining or discoloration of teeth occurs in two ways one is extrinsic and the other one is intrinsic. The detailed description of both the types is given below
Extrinsic staining, is largely due to environmental factors including smoking, pigments in beverages and foods, antibiotics, and metals such as iron or copper, the coloured compounds from these sources are adsorbed into acquired
dental pellicle or directly onto the surface of the tooth causing a stain to appear. Some of the causes of extrinsic stains are as follows
Dental plaque is a clear biofilm of bacteria that naturally forms in the mouth, particularly along the gumline, and it occurs due to the normal development and defences of the immune system.
Neglected or overlooked plaque will eventually calcify, and lead to the formation of a hard deposit on the teeth, especially around the gumline which is known as calculus. The organic matrix of dental plaque and calcified tissues undergo a series of chemical and morphological changes that lead to calcification of the dental plaque and therefore leading to the formation of calculus. The calculus can be found in different colors like yellow, brown, green, black and white depending on the formation time of the calculus.
Tar in the smoke from tobacco products tends to form a yellow-brown-black stain around the necks of the teeth above the gum line. The nicotine and tar in tobacco, combined with oxygen, turns yellow and over time will absorb into the pores of enamel and stain the teeth yellow.
Betel chewing produces blood-red saliva that stains the teeth red-brown to nearly black. The extract gel of betel leaf contain tannin, a chromogenic agent that causes discoloration of the tooth enamel.
Tannin is also present in coffee, tea, and red wine and produces a chromogenic agent that can discolor teeth. Large consumption of tannin-containing beverages stain the dental enamel brown due to the chromogenic nature.
Certain topical medications
Certain topical medications like
Chlorhexidine binds to tannins, meaning that prolonged use in persons who consume coffee, tea or red wine is associated with extrinsic staining teeth. Chlorhexidine mouthwash has a natural liking for sulfate and acidic groups commonly found in areas where plaque accumulates such as along the gum line, on the dorsum of the tongue and cavities. Chlorhexidine is retained in these areas and stain yellow-brown. The stains are not permanent and can be removed with proper brushing.
Exposure to such metallic compounds may be in the form of medication or occupational exposure. Examples include iron (black stain), iodine (black), copper (green), nickel (green), and cadmium (yellow-brown).
Intrinsic staining primarily occurs during the tooth development either before birth or at early childhood. Intrinsic stains are those that cannot be removed through mechanical measures such as debridement or a prophylactic stain removal. Few examples of intrinsic stains are stated below
Tooth wear and aging
Tooth wear is a progressive loss of enamel and dentinal layers due to tooth erosion, abrasion and attrition. As enamel wears down, dentin becomes more apparent and chromogenic agents are penetrated in the tooth more easily. The natural production of secondary dentin also gradually darkens teeth with age.
The evidence regarding carious tooth discoloration is inconclusive, however the most reliable evidence suggests that carious lesion allows for exogenous agents to enter dentin and hence increased absorption of chromogenic agents causing discoloration to the tooth.
The materials used during root canal treatments, such as eugenol and phenolic compounds, contain pigment that stain dentin. Restorations using amalgam also penetrate dentin tubules with tin over time therefore causing dark stains to the tooth.
Dental trauma which may cause staining either as a result of pulp necrosis or internal resorption. Alternatively the tooth may become darker without pulp necrosis.
Enamel hypoplasia causes enamel to be thin and weak. It produces a yellow-brown discoloration and can also cause the enamel’s smooth surface to be rough and pitted which causes the tooth to be susceptible to extrinsic staining, tooth sensitivity, malocclusion, etc.
Dental fluorosis causes enamel to become opaque, chalky white, and porous. The enamel can break down and cause the exposed subsurface enamel to become mottled and produce extrinsic dark brown-black stains. Dental fluorosis occurs due to excessive ingestion of fluoride or overexposure to fluoride during the development of enamel which usually occurs between the ages of one to four. Fluoride is considered an important factor in the management and prevention of dental cavities, the safe level for daily fluoride intake is 0.05 to 0.07 mg/kg/day.
Dentinogenesis imperfecta is a hereditary dentin defect, associated with osteogenesis imperfecta, which causes the tooth to become discolored usually blue or brown in colour and translucent giving teeth an opalescent sheen. The condition is autosomal dominant which means that the condition runs in the family.
The appearance of amelogenesis imperfecta depends on the type of amelogenesis, there are 14 different subtypes and can vary from the appearance of hypoplasia to hypomineralisation which can produce different appearances of enamel from white mottling to yellow brown appearances.
Tetracycline and minocycline
Tetracycline is a broad-spectrum antibiotic, and its derivative minocycline is common in the treatment of acne. The drug is able to chelate calcium ions and is incorporated into teeth, cartilage, and bone. Ingestion during the years of tooth development causes yellow-green discoloration of dentin visible through the enamel which is fluorescent under ultraviolet light. Later, the tetracycline is oxidized, and the staining becomes more brown and no longer fluoresces under UV light.
Root resorption is clinically asymptomatic, however can produce a pink appearance at the amelocemental junction.
Tooth whitening or bleaching may be undertaken for a variety of reasons, but whitening may also be recommended to some individuals by dentist.
Intrinsic tooth staining
Endodontic treatment (internal bleaching)
Some groups are advised to carry out tooth whitening or bleaching procedure with caution as they may be at higher risk of adverse effects.
Patients with unrealistic expectations
Allergy to peroxides
Pre-existing sensitive teeth or gums
Cracks or exposed dentin of a teeth
Enamel developmental defects
Receding gums or gingival recession and yellow roots
Defective dental restorations or old restorations
Active periapical pathology like cysts
Untreated periodontal diseases
Pregnant or lactating women
Children under the age of 16 because the pulp chamber, or nerve of the tooth, is enlarged until this age. Tooth whitening under this condition could irritate the pulp or cause it to become sensitive. Younger people are also more susceptible to abusing bleaching procedure.
Types Of Bleaching
Before the treatment, the clinician should examine the patient by taking a health and dental history, observe hard and soft tissues, placement and conditions of restorations, and sometimes x-rays to determine the nature and depth of possible irregularities.
If this is not completed prior to the whitening agents being applied to the tooth surface, excessive sensitivity and other complications may occur after the completion of the procedure.
The whitening shade guides are used to measure tooth color.
These shades determine the effectiveness of the whitening procedure, which may vary from two to seven shades.
These shades may be reached after a single in office appointment, or may take longer, depending on the individual.
The effects of bleaching can last for several months, but may vary depending on the lifestyle of the patient.
Consuming tooth staining foods or drinks that have a strong color may compromise effectiveness of the treatment.
These include food and drinks containing tannins such as coffee, tea, red wines, etc.
Power or light-accelerated bleaching uses light energy which is intended to accelerate the process of bleaching in a dental office. Different types of energy can be used in this procedure, with the most common being
plasma arc. Use of light during bleaching increases the risk of tooth sensitivity and may not be any more effective than bleaching without light when high concentrations of hydrogen peroxide are used.
Internal bleaching is a process which occurs after a tooth has been endodontically treated.
This means that the tooth will have had the nerve of the tooth extirpated or removed through a root canal treatment at the dentist or by a specialist endodontist.
Internal bleaching is often sought after in teeth which have been endodontically treated as tooth discoloration becomes a problem due to the lack of nerve supply to that tooth.
It is common to have this internal bleaching done on an anterior tooth.
A way around this is by sealing off the bleaching agent inside the tooth itself and replacing it every few weeks until the desired shade has been achieved.
At Home Bleaching
Strips and gels
The plastic whitening strips contain a thin layer of peroxide gel and are shaped to fit the buccal or labial surfaces of teeth.
Specific whitening strip products have their own set of instructions however the strips are typically applied twice daily for 30 minutes for 14 days.
In several days, tooth color can lighten by 1 or 2 shades.
The tooth whitening endpoint does depend on the frequency of use and ingredients of the product.
Whitening gels are applied onto the tooth surface with a small brush.
The gels contain peroxide and are recommended to be applied twice a day for 14 days.
Whitening rinses work by reaction of the oxygen sources such as hydrogen peroxide within the rinse and the chromogens on or within the tooth. It is recommended to use twice a day, rinsing for one minute. To see an improvement in shade color, it can take up to three months.
Whitening toothpastes differ from regular toothpastes in that they contain higher amounts of abrasives and detergents to be more effective at removing tougher stains. Some whitening toothpastes contain low concentrations of carbamide peroxide or hydrogen peroxide which help lighten tooth color however they do not contain bleach. With continuity of use over time, tooth colour can lighten by one or two shades.
Tray-based tooth whitening is achieved by wearing a fitted tray containing carbamide peroxide bleaching gel overnight or for two to four hours a day. If manufacturer’s instructions are followed, tooth whitening can occur within three days and lighten teeth by one or two shades. This type of tooth whitening is available over-the-counter and professionally from an oral health professional.
Baking soda is a safe, low abrasive, and effective stain removal and tooth whitening toothpaste. Tooth whitening toothpaste that have excessive abrasivity are harmful to dental tissue, therefore baking soda is a desirable alternative. To date, clinical studies on baking soda report that there have been no reported adverse effects.
Whitening pens are a convenient way to touch up any dental surface. The plastic, convenient, tube contains a bleaching gel that can be easily applied in hard-to-reach spots. In order to work, the gel needs to stay on the tooth surface for around 20-30 minutes.