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

The document attached has been archived with permission from the Australian Dental Association. An external link to the publisher’s copy is included.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 20μl 30 per cent w/w hydrogen peroxide; Group 3 – 20μl 30 per cent w/w hydrogen peroxide and thermocatalytically activated; Group 4 – 20μl acidified thiourea; Group 5 – 20μl acidified thiourea and 20μl 30 per cent w/w hydrogen peroxide; Group 6 – 20μl acidified thiourea and 20μl one per cent sodium hypochlorite; Group 7 – 20μl acidified thiourea, 20μl one per cent sodium hypochlorite and 20μl 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.DS Farmer, P Burcham, PD Mari

A virtual reality embodiment technique to enhance helping behavior of police toward a victim of police racial aggression

There is an alarming level of violence by police in the US toward African Americans. Although this may be rooted in explicit racial bias, the more intractable problem is overcoming implicit bias, bias that is non-conscious but demonstrated in actual behavior. If bias is implicit, it is difficult to change through explicit methods that attempt to change attitudes. We carried out a study using virtual reality (VR) with 38 officers in a US police department, who took part in an interrogation of an African American suspect alongside an officer who was racially abusive toward the suspect. Seventeen of the participants witnessed the interview again from a third person perspective (Observer) and 21 from the embodied perspective of the suspect, now a victim of the interrogation (Victim condition), having been assigned randomly to these two groups. Some weeks later, all witnessed aggression by an officer toward an African American man in a virtual cafe scenario. The results show that the actions of those who had been in the Victim condition were coded as being more helpful toward the victim than those in the Observer condition. We argue that such VR exposures operate at the experiential and implicit level rather than the explicit, and hence are more likely to be effective in combating aggression rooted in implicit bias

Activity of key enzymes of antioxidant system in rat blood plasma under the effect of histamine and sodium hypochlorite

The effects of histamine in 1 mg/kg and 8 mg/kg doses that correspond to the doses causing pathological effects at experimental conditions and of sodium hypochlorite in 5 mg/l dose – the lowest concentration of sodium hypochlorite that affects a body by oral administration, on the key enzymes of blood plasma antioxidant system were studied. It was found that histamine used in both concentrations intensified superoxide dismutase activity for 14 days. The simultaneous injections of histamine and sodium hypochlorite caused significant activation of superoxide dismutase in rats. Sodium hypochlorite received by rats with drinking solution caused the same effect. The catalase activity of blood plasma was not significantly affected by histamine, and its activity was significantly increased only under the influence of biogenic amine in 1 mg/kg dose on the 7th day of the experiment. Sodium hypochlorite caused a decline in catalase activity both in intact animals and in animals that received histamine injections subcutaneously. The injection of histamine in 1 mg/kg dose caused an increase in glutathione peroxidase activity on the 1st and 7th day of the experiment. Histamine in 8 mg/kg dose caused the intensification of glutathione peroxidase activity only on the 1st day, followed by the inhibition on the 14th day of the experiment. Sodium hypochlorite received by rats with drin­king solution led to general lowering of glutathione peroxydase activity in blood plasma