thiourea and Tooth-Discoloration

Tooth discolouration could occur due to bacterial contamination in traumatized teeth. Hydrogen peroxide is the commonly used bleaching agent. However, due to concerns over safety, alternative bleaching regimes such as sodium perborate (S) and thiourea-hydrogen peroxide (T) have been investigated.. Apices resected and pulp extirpated 99 premolars were divided into two groups. Group 1 and 2 was injected with blood and blood/bacteria, stored anaerobically for 35 days. The two groups were treated by bleaching with water, S or T. Teeth were rebleached after 7 days. Colourimetric evaluation was assessed using digital imaging, CasMatch standardization and CIE L*a*b colour system preoperatively, 35 days of staining and 7 and 14 of bleaching. A linear mixed model with fixed effects of time, group and bleach was used to examine colour difference.. Blood-stained teeth were significantly redder and darker on day 35 compared with blood/bacteria-stained teeth. After bleaching, blood-stained teeth retained significant redness compared with blood/bacteria-stained teeth using either S or T. T produced a significantly whiter shade in both the groups after 14 days.. Blood-stained teeth were significantly darker and red compared with blood/bacteria-stained teeth. T bleaching regime was more effective than S.

Topics: Bicuspid; Borates; Color; Colorimetry; Humans; Hydrogen Peroxide; Linear Models; Thiourea; Tooth; Tooth Bleaching; Tooth Discoloration

Current techniques for intra-coronal bleaching of stained root-filled teeth employ oxidative bleaching with hydrogen peroxide. However, concern over the potential for invasive cervical resorption following the use of hydrogen peroxide has been expressed by many researchers, and recommendations have been made to limit the use of this agent. A reductive-oxidative bleaching process using a thiourea and hydrogen peroxide regimen is proposed as an effective and safer bleaching combination. The efficacy of this novel bleaching regimen is evaluated in this study.. The study involved a quantitative and qualitative spectrophotometric assessment of the ability of two amine (bleaching) agents, aqueous thiourea and acidified thiourea, to alter the absorption spectra of haemoglobin and methaemoglobin compared to hydrogen peroxide. In addition, extracted premolar teeth discoloured by blood were subjected to different bleaching regimens using amine reducing agents and hydrogen peroxide. The change in the colour of the bloodstained dentine samples was measured at each stage of the bleaching process with a Photometer and Reflectance Densitometer. Comparisons of different treatments were made using a method of least significant difference and/or analysis of variance.. Spectrophotometric studies showed that acidified thiourea solution greatly reduced the colour of the haemoglobin and methaemoglobin in the visible range (330-760 nm). Aqueous thiourea had no effect on the presence of haemoglobin and methaemoglobin. Reflection Densitometer and Photometer scores indicate that the greatest bleaching effect was achieved by the combined acidified thiourea and hydrogen peroxide regimen.. The recognition that bleaching discoloured teeth is a chemical process, which can be achieved by both reducing and oxidizing agents, offers the possibility of developing new and safer clinical bleaching protocols. It is concluded that the bleaching regimen which employs the sequential use of 0.1 M acidified thiourea and 30% w/v hydrogen peroxide is as effective at bleaching bloodstained dentine as 30% w/v hydrogen peroxide alone. However, the addition of thiourea to the bleaching regimen has the potential benefit of reducing the level of damaging hydroxyl radicals and achieving a safer bleaching process.

Topics: Adolescent; Blood; Child; Humans; Hydrogen Peroxide; Oxidants; Thiourea; Tooth Bleaching; Tooth Discoloration

Current techniques for intra-coronal bleaching of stained root-filled teeth employ oxidative bleaching with hydrogen peroxide. However, it has been shown that hydrogen peroxide and hydroxyl radicals, the by-products of the bleaching process, diffuse from the pulp chamber to the outer root surface. The control of such diffusion may be of importance in minimizing the risk of invasive cervical resorption (ICR) which has been linked to intracoronal bleaching. A novel reductive-oxidative bleaching process using a thiourea and hydrogen peroxide regimen is proposed as a more effective and safer bleaching protocol. Also, other clinical considerations during the intra-coronal bleaching of root-filled teeth are discussed.

Topics: Drug Combinations; Free Radical Scavengers; Humans; Hydrogen Peroxide; Oxidants; Root Resorption; Thiourea; Tooth Bleaching; Tooth Discoloration; Tooth, Nonvital