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Objectives: This study assessed the efficacy of different combinations of oxalic acid, 35% hydrogen peroxide, and 5.25% sodium hypochlorite (NaOCl) for bleaching of tooth discolorations caused by hemoglobin. Materials and Methods: In this in vitro study, 40 sound extracted human premolars were disinfected and decoronated. Their primary color parameters were measured (T1). The teeth were then centrifuged with human blood for 3 days, rinsed, polished, and their color parameters were measured again (T2). They were randomly divided into 4 groups (N=10) and treated as follows: Group A: in-office bleaching with Pola-Office Plus followed by 30 seconds of light-curing, group B: 0.24 M oxalic acid for 5 minutes followed by in-office bleaching, group C: 5.25% NaOCl for 5 minutes followed by in-office bleaching, and group D: 0.24 M oxalic acid (5 minutes) followed by 5.25% NaOCl (5 minutes) and subsequent application of in-office bleaching gel. The color parameters of the teeth were measured again (T3). Data were analyzed by one-way ANOVA and paired sample t-test (alpha=0.05). Results: T2-T3 ΔE in groups B and D was significantly higher than that in group A (P<0.05); the difference between groups B and D was not significant. The mean ΔE and ΔL in group C were not significantly different from those in group A (P>0.05). ΔL significantly and equally increased in groups B and D after bleaching. Conclusion: Application of oxalic acid followed by in-office bleaching gel is more effective than the bleaching gel alone for correction of tooth discolorations caused by hemoglobin. [ABSTRACT FROM AUTHOR]

Objectives Bleaching agents can change the organic and mineral contents of the tooth structure. The aim of this study was to evaluate the effects of two remineralizing agents on surface roughness of bleached enamel. Methods In this experimental study, 24 premolars were collected. The testing area was a window measuring 3 × 4 mm. First the surface roughness of specimens was measured by atomic force microscopy (AFM). Then, the teeth were bleached. Surface roughness was measured again. Specimens were randomly divided into 3 groups. No remineralizing agent was applied in the control group (A). Casein phosphopeptide amorphous calcium phosphate (CPP-ACP) and Remin-Pro were used in groups B and C, respectively. After 15 days, the surface roughness was measured. The changes in surface roughness were analyzed by paired t-test, and comparison between the groups was done by the Welch and Games-Howell post hoc tests. Results The surface roughness increased after bleaching (P<0.000). Surface roughness in groups B (P=0.03) and C (P=0.04) was significantly lower than that in group A. There was no significant difference in the level of surface roughness reduction between groups B and C. The Welch test revealed that the mean change in surface roughness values after remineralization in groups B and C was significantly higher than that in group A (P=0.001 and P=0.002, respectively). The difference between groups B and C was not significant (P=0.97). Conclusion CPP-ACP and Remin-Pro reduce the surface roughness of bleached enamel more effectively than the saliva. [ABSTRACT FROM AUTHOR]