PubMed · 15218685
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Ellen F Nuss. How safe is tooth bleaching?. https://pubmed.ncbi.nlm.nih.gov/15218685/
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OBJECTIVES: The purpose of this study was to evaluate the influence of different home bleaching procedures on surface microhardness of human enamel. METHODS: Among eight groups 192 incisors were distributed. The facial surface of each incisor was polished and baseline hardness of enamel (m0; Knoop) was assessed with a load of 1N for 30s. Subsequently, the enamel was treated for 14 days with the bleaching agent: groups 1, 2 and 4 Viva Style Paint on, 8% carbamide peroxide (CP) 1x20min, 2x20min and 2x5min; group 3 Colgate Simply White, 5.9% hydrogen peroxide (HP), 2x30min; group 5 Viva Style 10% CP 1x1h; group 6 Blend-a-med White Strips, 5.9% HP 2x30min; group 7 Odol-med3 Beauty-Kur, sodium chlorite 2x10min; group 8 control, running water 1x1h. Hardness was reassessed after the last bleaching treatment (m1) and after 6 weeks storage in artificial saliva (m2). RESULTS: Changes in microhardness were as follows (m0-m1): (1) -2.3 (+/-20.3); (2) -8.9 (+/-27.2); (3) 63.4 (+/-56.3); (4) 9.6 (+/-30.1); (5) 12.8 (+/-62.6); (6) 92.2 (+/-50.2); (7) 158.4 (+/-59.7); (8) 10.6 (+/-38.5). Statistical analysis showed that hardness values were significantly (p< or =0.0005; Wilcoxon test) reduced in groups 3, 6, and 7 (m1) and in group 7 (m2). SIGNIFICANCE: Both type of bleaching agent and concentration have a significant influence on the microhardness of enamel. The most critical bleaching agent seems to be the one containing sodium chlorite in combination with citric acid.
OBJECTIVES: The objective of this in vitro study was to investigate whether a high concentration 'in-office' bleaching agent affected the mineral content of enamel and dentin. METHODS: A commercially available 35% carbamide peroxide bleaching agent was applied for 2h to sectioned teeth (n=11). Specimens were then immersed in artificial saliva at 37 degrees C for a further 24h to simulate the oral environment. Tomographic images of these sections were obtained (micro-CT 80, Scanco, Switzerland) prior to and post-bleach application. Eight three-dimensional regions of interest (ROI), starting from the enamel surface extending to the dentinoenamel junction, were selected for each section. The hydroxyapatite equivalent mineral concentrations (g/cm(3)) of the ROIs were calculated. Any changes in mineral content as a consequence of the bleaching procedure were calculated in relation to each ROI. RESULTS: There was a significant reduction in the mineral content of enamel specimens post-bleach application extending to a depth of 250microm (paired t-test, p<0.05); this reduction in mineral content was greatest in the ROI's closest to the tooth surface. There was, however, no significant difference in the mineral content of dentin as a consequence of bleaching. SIGNIFICANCE: This in vitro study has shown that significant demineralization of enamel occurred following bleaching with 35% carbamide peroxide. The concept that 'in-office' bleaching is a non-destructive cosmetic procedure should be reconsidered.
OBJECTIVE: The aim of the present study was to assess the hypothesis that the efficiency of vital tooth bleaching depends on the concentration of carbamide peroxide agents. METHODS: The front teeth of 30 subjects were bleached at home with 10%, 17% or 0% (control) carbamide peroxide for 1 week in a double-blind study design. Tooth shades were determined in the LCH color space employing a visual shade matching system and a spectrophotometer. Differences in lightness (Deltal), chroma (Deltac) and hue (Deltah) were measured to assess the treatment process. After 2 weeks of no treatment, tooth shades were evaluated again to assess stability of the resultant shade. RESULTS: First-time changes of shade values could be observed after 3 days in the 17% group and after 7 days in the 10% group. After 1 week, in both the 17% group (Deltal: 2.80, Deltac: -3.33, Deltah: 0.60) and the 10% group (Deltal: 2.61, Deltac: -2.54, Deltah: 0.09), values for lightness and chroma were significantly different from the control (Deltal: 0.13, Deltac: 0.14, Deltah: 0.21, p<0.05) with no difference between the test groups (p>0.05). Two weeks after treatment, a rebound of shade values could be observed in the test groups (p<0.05). SIGNIFICANCE: The study indicates that higher concentration bleaching agents might whiten teeth faster with major changes in lightness and chroma. However, by bleaching daily for 1 week, similar effects can be achieved with both a high and a low concentration agent. After treatment, a regression of the resultant shade has to be expected.