Tooth enamel problems and whitening
Enamel is a very hard, white to off-white, highly mineralized substance that acts as a barrier to protect the tooth. The enamel helps protect teeth from daily wear from chewing, biting, crunching, and grinding. Although enamel is a strong protector of teeth, it can chip and crack. Enamel also insulates the teeth from potentially painful temperatures and chemicals.
But enamel can become susceptible to degradation, especially by acids from food and drink. When it erodes, patients may notice that their teeth are more sensitive to hot or cold foods, drinks, and sweets, since they can get through holes in the enamel to the nerves inside.
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Teeth whitening has become one of the most frequently requested dental procedures. The public has come to demand whiter, more perfect smiles, and in response, many options for tooth whitening have become available.
These include home-based products such as toothpaste, gels, and films, as well as in-office procedures where products containing highly concentrated bleaching agents are applied under professional supervision.
The dental profession and the public are aware of certain risks related to tooth whitenings, such as increased tooth sensitivity and gingival irritation. New research has shown that there are additional risks, such as tooth surface roughening and softening, increased potential for demineralization, and degradation or unacceptable colour change of dental restorations.
Industry Challenges
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Chemical bleaching solutions that penetrate the enamel structure are commonly used in whitening procedures. Bleaching agents will not completely remove most enamel discolorations, which are caused by developmental malformation or ion incorporation in the natural enamel structure (e.g., fluorosis). Removing intrinsic stains in dentin from the exterior by chemical or mechanical means is nearly impossible. Because of the microporous structure of enamel and dentin, stains adhere to it quite well.
When peroxide is used too frequently or excessively, the outer layer of the teeth is damaged, leaving the enamel more porous and susceptible to discoloration. Additionally, it has been found that using 20% CP bleach for two weeks reduced the flexural strength of a bovine enamel and dentin complex by a statistically significant amount.
In teeth, an inorganic mineral (calcium phosphate in the form of hydroxyapatite) is combined with an organic protein matrix. The chemical and structural interplay between these two components leads to the extraordinary mechanical properties of teeth with respect to hardness and fracture toughness. Thus, teeth are not simply inorganic materials but highly optimized and complex organic-inorganic biocomposites. When aggressive bleaching agents like hydrogen peroxide are applied in high concentrations, it damages the organic matrix in the tooth, especially the dentin. Enamel contains about 1% organic matrix, and dentin contains about 20% organic matrix, mainly collagen. Bleaching could lead to the mechanical weakening of the tooth due to a decreasing integration of the calcium phosphate crystals. Increased tooth sensitivity can occur, mainly if highly concentrated hydrogen peroxide solutions are applied. There are also reports of structural damage to enamel surface prisms after using 35% carbamide peroxide. The risk of adverse effects will increase with the peroxide concentration.