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Project log

Shereen S Azer
added a research item
The purpose of this study was to evaluate the effect of bleaching on tooth discolouration from neutral food colourant media (NFCM). Freshly extracted human molar teeth (n = 32) were divided into four groups (n = 8): non-bleached treatment-NBT, non-bleached control-NBC, bleached treatment-BT and bleached control-BC. Bleached teeth specimens were subjected to 20% carbamide peroxide bleaching agent for 10h. Colour measurements (pre-test) were done using a non-contact spectroradiometer. The teeth specimens were immersed in a neutral buffer solution. NBT and BT groups had 0.025% red food colour (Red 40) added to the buffer solution. The immersed specimens were incubated for 4h at 37°C. Colour was again measured after immersion/incubation (post-test) and after subsequent polishing using plain-pumice slurry (post-polish). Differences in CIE a* (redness parameter) were analysed by repeated measures ANOVA with Bonferroni-corrected t-tests for the pairwise comparisons of interest. Tooth discolouration was measured as total stain (mean difference in a* between post-test minus pre-test), extrinsic stain (mean difference in a* post-polish minus post-test) and intrinsic stain (mean difference in a* post-polish minus pre-test) A statistically significant difference in the mean Δa* was observed (P = 0.009) between staining treatment for bleached and non-bleached teeth. Also, a statistically significant difference (P < 0.001) was noted between control and treatment groups of bleached teeth that were subjected to staining. Bleaching resulted in total and extrinsic tooth discolouration by the NFCM. It might be beneficial to avoid highly pigmented foods immediately following bleaching in order to optimize the effects of tooth whitening.
Shereen S Azer
added 2 research items
Objectives: The popularity of over the counter (OTC) tooth whitening products stems from their availability, ease of use, affordability, and rapid mode of action in yielding desirable effects. Several published studies have reported detrimental effects on hard dental tissues due to bleaching, particularly affecting enamel hardness. Products are advertised to work ranging from few minutes single application to several days through multiple applications. Three commonly used products; Luster Pro Light by Dentovations Inc. (40 min), as well as Crest 3D Whitestrips Professional Effects (3 days) and Opalescence Tooth Whitening Gel (multiple applications) were used. The purpose of this in vitro investigation was to compare the immediate after bleaching effects on hardness of human enamel. Methods: Extracted human incisor teeth were invested into acrylic resin blocks exposing the clinical crowns. The bleaching agents were applied directly on the facial surfaces of human natural teeth according to the manufacturer's instructions. The lingual surfaces were not bleached and served as control. Teeth were sectioned and prepared for nanoindentation. Indents were done in a wet environment using a Berkovich tip at a rate of 10 nm/sec up to 500 nm. A total of 216 indents were performed on enamel tissue to calculate enamel nanohardness (H) and were statistically analyzed ANOVA (Fisher's, P<0.05). Results: MeanSD values in GPa and ANOVA comparison test results are shown below: MeanSD ANOVA P-Value Luster 3.9100.4 Crest<Luster <0.0001 Opalescence 3.3021.0 Crest<Opalescence 0.0099 Crest 2.8331.6 Luster>Opalescence 0.0001 Conclusion: Immediate post bleaching enamel nanohardness testing revealed statistically significant differences between the 3 tested materials. The current findings indicate that enamel nanohardness is influenced differentially by various whitening agents; being greater for the Luster Pro Light group, followed by Opalescence gel and Crest Whitestrips.
Objectives: Tooth whitening (bleaching) products have become extremely popular because of their relative ease of use and affordability. Several products are available which, to ensure acceptable esthetic results, require multiple applications over extended periods of time involving several days. Prolonged exposure to such products has been shown to cause adverse effects on the physical properties of enamel. A recently introduced product (Luster Premium White by Dentovations Inc.) is recommended to produce desired whitening effect through a full treatment regimen of forty (40) minutes, whereby the bleaching agent is directly applied on the tooth and activated by light. The purpose of this in vitro investigation was to evaluate the immediate after bleaching effects on physical properties of human enamel; particularly nanohardness and elastic modulus. Methods: Extracted human incisor teeth were invested into acrylic resin blocks exposing the clinical crowns. Teeth were bleached for 40 minutes of light treatment per manufacturer's instructions, then sectioned and prepared for nanoindentation. Similarly intact non-bleached incisors were used for control. Indents were done in a wet environment using a Berkovich tip at a rate of 10 nm/sec up to 500 nm. Each specimen was subjected to 7 indents. Enamel nanohardness-H and elastic modulus-E were then calculated. Results: MeanSD values in GPa and two-way ANOVA with post-hoc Fisher's PLSD comparison test results are shown below: Treatment Control P-Value Nanohardness-H 3.2561.1 2.9730.5 0.3617 Elastic Modulus-E 45.07616.2 47.2415.1 0.6214 Conclusion: Since time and effects on hard tissues are of prime importance for bleaching protocols, the results of this investigation are of particular clinical significance. Immediately following treatment with Luster Premium White, no significant differences were seen between bleached and non-bleached enamel regarding nanohardness and enamel elastic modulus indicating no adverse effects of product usage on human enamel. This study is supported in part by Dentovations Inc., Boston, MA, USA.