Reviews of the Current status of Tooth Whitening

Published: 27th June 2011
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The Tooth Whitening in Noida is an alternative therapeutic method. In contrast to crowning or veneering, whitening of teeth is relatively non-invasive and conserves dental hard tissue. Vital teeth can be whitened by the nightguard vital bleaching technique utilizing carbamide peroxide gels as the bleaching medium .The whitening of root-filled teeth can be carried out by internal whitening treatment. This review of the walking bleach technique describes the recommended procedures to help reduce the risks of complications and to ensure a successful bleaching therapy.

Dissemination of blood components into the dentinal tubules caused by pulp extirpation or traumatically induced internal pulp bleeding is a possible reason for discolouration of non-vital teeth. A temporary colour change of the crown to pink can often be detected initially. Then, blood degradation products such as haemosiderin, haemin, haematin and haematoidin release iron during haemolysis .The iron can be converted to black ferric sulphide with hydrogen sulphide produced by bacteria, which causes a grey staining of the tooth. Apart from blood degradation, degrading proteins of necrotic pulp tissue may also cause discolouration. If the access cavity is prepared inappropriately, pulp tissue can be left in the pulp chamber in the pulp horns, which maybe another reason for discolouration. Coronal discolouration of root-filled teeth can also be caused by some root-filling materials or tetracycline-containing medicaments. These discolourations arise when remnants of root-filling materials or medicaments are left in the pulp chamber and the staining substance infiltrates the dentinal tubules. Although no penetration of the dental enamel takes place, there is an observable difference of colour on the tooth (Vogel 1975).

Reports on the bleaching of discoloured non-vital teeth were first described in the middle of the 19th century. Chlorinated lime was recommended for the whitening of non-vital teeth . Later, oxalic acid and other agents such as chlorine compounds and solutions , sodium peroxide (Kirk 1893), sodium hypochlorite or mixtures consisting of 25% hydrogen peroxide in 75% ether were used to bleach non-vital teeth.

The decomposition of H2O2 into active oxygen is accelerated by application of heat, addition of sodium hydroxide or light . H2O2-releasing bleaching agents are therefore chemically unstable. Only fresh preparations should be utilized, which must be stored in a dark, cool place. The thermocatalytic technique was proposed for many years as the best way of whitening non-vital root-filled teeth because of the high reactivity of H2O2 upon application of heat . In this thermocatalytic procedure, 30-35% H2O2 is applied to the pulp cavity and heated by special lamps or hot instruments. In addition to this, cotton pellets impregnated with 30-35% H2O2 were often used as temporary fillings .

The chemical reaction mentioned above emphasizes that release of H2O2 by mixing sodium perborate and water is achieved without supplementary addition of H2O2. Several studies have reported bleaching effectiveness by comparing mixtures of sodium perborate with distilled water or H2O2 in different concentrations. Rotstein et al. and Weiger et al. did not report any significant difference in the effectiveness between sodiumperborate mixed with 3-30%H2O2 and the sodiumperborate-distilled water mixture. However, the whitening effect of the second mixture can take longer, so that more frequent changes of the bleaching agent may be necessary. The shade stability of teeth treated by a mixture of perborate and water is as high as the shade stability of teeth in which a mixture of sodium perborate with 3 or 30% H2O2 was used . Other surveys found that mixing sodiumperborate with 30%H2O2wasmore effective than mixing with water . Freccia et al. showed that the walking bleach technique with a mixture of 30% H2O2 and sodiumperborate was as effective as the thermocatalytic technique.

Complications of the walking bleach technique are contributed to an acidic pH of the bleaching reagent; 30% H2O2 has a pH value between 2 and 3.When 30% H2O2 is mixed with sodium perborate in a ratio of 2 :1 (g mL_1), the pH of this mixture is alkaline. If further 30% H2O2 is added, it becomes acidic. Weiger et al. tested the pH value of mixtures consisting of 2 g sodiumperborate and 1mL of 10-30% H2O2 or distilled water. Initially, a neutral or weak alkaline pH for all compositions was apparent, e.g. the mixture of 30% H2O2 and perborate showed an initial pH value of 7.0-8.7 depending on the perborate used (mono-, tri- or tetrahydrate). It was also shown that the pH significantly in creased with decreasing concentration of H2O2. The highest initial pH was observed when sodiumperborate was mixed with water. Within a day, a distinct increase of the pH value of 9- 11was achieved. This is true for a sodiumperborate suspension mixed with water or H2O2. This increase in pH is desirable because the whitening effectiveness of buffered alkalineH2O2 is significantly higher than the effect of unbuffered H2O2 .

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