Tooth discoloration by blood: an in vitro histochemical study

Time-Course Diffusion of Hydrogen Peroxide Through Human Dentin: Clinical Significance for Young Tooth Internal Bleaching

The purpose of this study was to record the time-course diffusion of hydrogen peroxide through human dentin from a peroxide carbamide gel designed for the walking bleach technique in order to determine its optimal renewal time. It was considered that the optimal renewal rate corresponded to the time necessary to achieve 80% of the maximal diffusion because a much longer time does not involve further significant diffusion. Thirty-six freshly extracted human premolars were used for this study. Eighteen were extracted for orthodontic reasons on patients under 20 years old (young-teeth group). Eighteen were extracted for periodontal reasons on patients between 40 and 60 years old (old-teeth group). The teeth were endodontically treated, and a flat defect was created at the enamel-cementum junction. The teeth were suspended in vials containing water, and the access cavities were filled with 20 microL of 20% hydrogen peroxide gel. The amount of diffusing hydrogen peroxide was assessed at 1 hour, 24 hours, 48 hours, and 120 hours. The diffusive flux and the maximal diffusion were calculated as well as the optimal renewal time. Hydrogen peroxide diffusion through young teeth lasted 352 hours but lasted 291 hours through old teeth. Diffusive flux and maximal diffusion were higher through young teeth than through old teeth. The optimal renewal time for young teeth was 33 hours and for old teeth was 18 hours.

Evaluation of a combined thiourea and hydrogen peroxide regimen to bleach bloodstained teeth

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Pink Teeth in a Series of Bodies Recovered From a Single Shipwreck

Pink teeth have most often been observed in victims of drowning but have also been reported in subjects who died suddenly and unnaturally. There is general agreement that there is no obvious connection between the occurrence of pink teeth and the cause of death, but the condition of the surroundings (especially humidity) must certainly play an important role in the development of the pink-tooth phenomenon. The frequency and distribution of postmortem pink coloration of the teeth have been studied among a representative sample of 52 cadavers. All the bodies were victims of a single shipwreck that occurred on March 13, 1997, in the middle of the Otranto Canal (Mediterranean Sea). The bodies were recovered from the seawater after approximately 7 months. A distinct pink coloration of the teeth was found in only 18 cadavers (13 females and 5 males) of ages ranging between 13 and 60 years. The phenomenon was more pronounced in younger individuals due to age-related changes of the root canal, less penetrable by the pigment responsible for the postmortem pink staining. By histochemical methods and autofluorescence, hemoglobin and its derivatives have been identified as the most likely pigments responsible for this postmortem process that can be considered analogous to postmortem lividity. These data are consistent with previous reports on pink teeth, indicating that the diffusion of the blood in the pulp into the dentinal tubules causes the red discoloration of the teeth. Based on the results, the pigmentation is more prominent on the teeth with single roots rather than in the posterior teeth with multiple roots.

The ability of thiourea to scavenge hydrogen peroxide and hydroxyl radicals during the intra-coronal bleaching of bloodstained root-filled teeth

BACKGROUND

Hydrogen peroxide, an agent used in the intra-coronal bleaching of root-filled teeth for over a century, has been shown to diffuse from the pulp chamber to the outer root surface. Furthermore, it has been demonstrated that destructive hydroxyl radicals, the by-products of the bleaching process, have been detected on the external 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 intra-coronal bleaching of discoloured root-filled teeth using hydrogen peroxide. The aims of the present in vitro study are to quantify the diffusion of hydrogen peroxide and hydroxyl radicals to the outer root surface following intra-coronal bleaching, and to evaluate the ability of thiourea incorporated into the bleaching protocol to scavenge residual hydrogen peroxide and hydroxyl radicals.

METHODS

Thirty-five single rooted premolar teeth with intact cementum at the cemento-enamel junction were used in this project. Thirty teeth were stained with red blood cells and root-filled with gutta-percha and AH26. The five unstained teeth were root-filled and constituted a negative control (Group 1). The stained teeth were divided equally into the following experimental groups and subjected to various intra-coronal bleaching regimes: Group 2--'walking bleach' with 20 microl 30 per cent w/w hydrogen peroxide; Group 3--20 microl 30 per cent w/w hydrogen peroxide and thermocatalytically activated; Group 4--20 microl acidified thiourea; Group 5--20 microl acidified thiourea and 20 microl 30 per cent w/w hydrogen peroxide; Group 6--20 microl acidified thiourea and 20 microl one per cent sodium hypochlorite; Group 7--20 microl acidified thiourea, 20 microl one per cent sodium hypochlorite and 20 microl 30 per cent w/w hydrogen peroxide. The reaction products of the bleaching process were quantified at the outer root surface using high performance liquid chromatography and electrochemical detection (HPLC-ECD).

RESULTS

Results showed that hydrogen peroxide used alone in Groups 2 and 3 was able to be detected at the outer root surface in 100 per cent of the samples, and that the presence of the hydroxyl radical generated in both groups was detected in equal amounts (P < 0.05). When thiourea was incorporated into the bleaching protocols in Groups 5-7, it was shown to scavenge both hydrogen peroxide and hydroxyl radicals to a significant degree (P < 0.05).

CONCLUSIONS

Acidulated thiourea is an effective scavenger of residual hydrogen peroxide and hydroxyl radicals generated during the intra-coronal bleaching of bloodstained root-filled teeth.

Inaugural Geoffrey Heithersay oration in endodontics and oral biology

Smiles are often a reflection of dental health, and as such provide great satisfaction to a dental practitioner who has successfully managed complex dental problems such as malformed, malpositioned or traumatically damaged teeth. A biological approach to the management of the pulpal and periodontal responses to dental trauma has been made possible by cumulative research, and application of this knowledge will enhance successful treatment.

Tooth discolouration and staining: a review of the literature

OBJECTIVE

To carry out an extensive review of the literature on tooth staining with particular regard to some of the more recent literature on the mechanisms of tooth staining involving mouthrinses.

DESIGN

Comprehensive review of the literature over four decades.

CONCLUSIONS

A knowledge of the aetiology of tooth staining is of importance to dental surgeons in order to enable a correct diagnosis to be made when examining a discoloured dentition and allows the dental practitioner to explain to the patient the exact nature of the condition. In some instances, the mechanism of staining may have an effect on the outcome of treatment and influence the treatment options the dentist will be able to offer to patients.

A quantitative comparison of traditional and non-peroxide bleaching agents

Single-rooted premolar teeth, stained with blood utilizing the technique devised by Freccia & Peters (1981), were subjected to traditional and non-peroxide bleaching agents. Colour changes were recorded over a period of 7 days using a Speedmaster R75-CP Reflection Densitometer. The most efficient removal of staining occurred after the application of 30% hydrogen peroxide, with sodium perborate being 75% as effective. All bleaching agents realized their optimum efficacy within the first 3 days. A combination of three enzymes (amylase, lipase and trypsin) with disodium edetate was not as effective as the routine bleaching agents; however, the combination did have a modifying effect on the blood stains. It is suggested that other non-peroxide agents should be investigated to determine their efficacy in removing staining from experimentally induced blood-stained teeth.

Hydroxyl radical activity in thermo-catalytically bleached root-filled teeth

Intra-coronal bleaching of root-filled teeth has been associated with invasive cervical root resorption. It is considered that during bleaching hydrogen peroxide diffuses through the tooth structure into the cervical periodontium, resulting in periodontal tissue destruction and initiating a resorptive process. Hydrogen peroxide is capable of generating hydroxyl radical, an oxygen-derived free radical, in the presence of ferrous salts. Hydroxyl radicals are extremely reactive and have been shown to degrade components of connective tissue, particularly collagen and hyaluronic acid. The aim of the present study was to determine whether hydroxyl radicals are generated during the bleaching of root-filled teeth which have been discoloured by blood. Forty extracted human premolar teeth were root-filled with gutta-percha and AH26 sealer cement. Twenty of the teeth were experimentally discoloured by blood. All teeth were then thermo-catalytically bleached using 30% hydrogen peroxide while tooth roots were seated in a test solution of sodium salicylate. Hydroxyl radical generation was determined by the detection of reaction products of this radical with salicylate using high performance liquid chromatography with electrochemical detection (HPLC-ECD). The presence of hydroxyl radicals was detected in twenty-five of the teeth. There was a significant association between the production of hydroxyl radicals and the presence of tooth discolouration caused by blood components. Greatest yields of hydroxyl radicals occurred in teeth in which EDTA had been used to clean the pulp chamber prior to bleaching. It was concluded that hydroxyl radicals are generated during the thermo-catalytic bleaching of root-filled teeth. Generation of this toxic chemical species may be one mechanism underlying periodontal tissue destruction and root resorption after intra-coronal bleaching.