| Abstract|| |
Background: The objectives were to evaluate the effect of surface treatments and waiting time before contact with dye on bleached enamel staining and surface treatments on roughness. Methods: One hundred bleached teeth were randomly assigned to G1 artificial saliva, G2 2% sodium fluoride (Flugel, Nova DFL), G3 casein phosphopeptide-amorphous calcium phosphate fluoride paste (MI Paste Plus, GC America), G4 rinse for bleached color maintenance (Keep White Rinse, DMC), and G5 polishing with impregnated disks (SuperBuff Disk, Shofu). Fifty specimens were immersed in coffee immediately after treatment; the others 1 h after. Color difference (ΔE) was evaluated with a spectrophotometer (Vita EasyShade) and roughness (Ra, Rq) with an optical profilometer (NewView 7300). Effects were analyzed with two-way ANOVA, Friedman, and Kruskal–Wallis test (P < 0.05). Results: Surface treatments (P = 0.878), waiting time (P = 0.105), and interaction (P = 0.145) were not significant to bleached color maintenance. Roughness was different among the evaluation time points (2nd evaluation >1st evaluation >3rd evaluation) (P < 0.001); not among surface treatments (G1, G2, G3, G4, G5) (P > 0.05). Conclusions: Surface treatments were similar to saliva for bleached enamel color maintenance. Immediate or 1-h postponed contact with coffee did not affect bleached enamel color. Bleaching increased enamel roughness; surface treatments and artificial saliva decreased it.
Keywords: Color, dental enamel, hydrogen peroxide, pigmentation, tooth bleaching
|How to cite this article:|
Hauss Monteiro DD, Valentim PT, Elias DC, Moreira AN, Machado Cornacchia TP, Magalhães CS. Effect of surface treatments on staining and roughness of bleached enamel. Indian J Dent Res 2019;30:393-8
|How to cite this URL:|
Hauss Monteiro DD, Valentim PT, Elias DC, Moreira AN, Machado Cornacchia TP, Magalhães CS. Effect of surface treatments on staining and roughness of bleached enamel. Indian J Dent Res [serial online] 2019 [cited 2020 Nov 25];30:393-8. Available from: https://www.ijdr.in/text.asp?2019/30/3/393/264111
| Introduction|| |
Low pH bleaching agents can induce alterations on the dental surface., Different methods of analysis demonstrated enamel morphological alterations after tooth bleaching, including demineralization, depressions and other irregularities,,,,,, and enamel microhardness decrease.,,,,
Immersion in saliva after bleaching can increase enamel microhardness,,, with a minor calcium loss.,, However, saliva might not be able to completely restore calcium and phosphate baseline levels on bleached enamel. Fluoride and other remineralizing solutions can favor a positive balance toward remineralization.,,,,
Sodium fluoride can minimize enamel demineralization,, roughness, and other morphological alterations after tooth bleaching., However, the effect of neutral or acidic fluoride on bleached enamel staining is controversial., Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) can prevent enamel demineralization and promote remineralization,,,, decreasing bleached enamel roughness., In addition, CPP-ACP does not affect bleaching efficacy  but induces less staining immediately after bleaching.
After 12 weeks of treatment, a Plasdone-containing rinse promoted a color alteration similar to conventional dentifrice. Polishing bleached enamel with a nanohydroxyapatite paste promoted a roughness decrease similar to polishing with sodium fluoride, and polishing with a nanometric polishing paste, feltrum, and Sof-lex disks can produce a smoother surface than a nonbleached one.
Although immersion for 2 h in artificial saliva is effective in preventing bleached enamel staining, the ideal waiting time before contact with dyes is controversial. Even within 72 h after bleaching, there is still a potential for bleached teeth pigmentation, but some authors did not find any difference between 30 and 150 min.
The aim of this study was to evaluate the effect of surface treatments and waiting times before contact with dye on enamel staining after 35% hydrogen peroxide bleaching and the effect of surface treatments on bleached enamel roughness. The primary null hypothesis was that surface treatments and waiting times do not affect bleached enamel color maintenance, and the secondary was that surface treatments do not affect bleached enamel roughness.
| Methods|| |
One hundred bovine incisors were randomly divided into ten complete blocks. The independent variables were surface treatments and waiting time before contact with dye (immediate or 1-h postponed). The dependent variables were color maintenance (ΔE) evaluated with a spectrophotometer (n = 10) and roughness with a profilometer (Ra – mean roughness, Rq – root mean square roughness) (n = 20).
The crowns were cleaned, the pulps were extracted, and the chamber entrance was sealed with zinc oxide-eugenol paste (Lysanda Produtos Odontológicos, São Paulo, Brazil). A 6-mm 2 experimental area was delimited on the buccal incisal third by nail polish application (Risqué Niasi S.A., Taboão da Serra, Brazil). The specimens were identified.
The digital spectrophotometer (Vita EasyShade Compact, Vita, Bad Säckingen, Germany) was calibrated in the beginning and after each specimen evaluation. The first reading was performed. Three readings of L*, a*, and b* of CIEL*a*b* system were performed, and the mean was calculated.
The roughness parameters Ra and Rq were obtained with an optical laser three-dimensional (3D) profilometer (NewView 7300, Zygo Corporation, Middlefield, EUA). The adjustment parameter was 0.001% for minimal modulation, 7 pixels for minimal area size, and 0.60 μm for spikes height. Baseline evaluation was performed.
The pH of the 35% hydrogen peroxide bleaching agent (Whiteness HP, LOT 170214, FGM Produtos Odontológicos, Joinville, Brazil) was 5.40 within 15 min, measured with a potentiometer (Metrohm 827 pH lab, Metrohm Pensalab Instrumentação Analítica LTDA, São Paulo, Brazil). The specimens were bleached three times (15 min each), washed, and subjected to a second evaluation of color and roughness.
The specimens were divided into five groups according to a complete block design with a spreadsheet for randomization generated with Microsoft Excel (Microsoft Corporation, Redmond, USA).
- Group 1 (G1): Immersion in neutral artificial saliva for 10 min, which contained 0.96 g KCl, 0.67 g NaCl, 0.04 g of MgCl2, 0.27 g monobasic potassium phosphate, 0.12 g calcium phosphate tricalcium, 10 ml preservative solution, 24 ml 70% sorbitol, 8 g carboxymethylcellulose, and bidistilled water to a final 1000 ml. The preservative solution was 15% nipagin, 5% nipasol, and propylene glycol
- Group 2 (G2): Neutral 2% sodium fluoride (Flugel, LOT 15050588, DFL Indústria e Comércio S.A. Rio de Janeiro, RJ, Brazil) for 4 min
- Group 3 (G3): Casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF) paste (GC MI Paste Plus™, LOT 120411M, GC Corporation, Tokyo, Japan) for 3 min
- Group 4 (G4): Two sprays of a rinse for bleaching result maintenance (Keep White Rinse, LOT 20615, DMC, São Carlos, Brazil)
- Group 5 (G5): Polishing with aluminum oxide-impregnated feltrum disks (SuperBuff, LOT 0411711, Shofu, San Marcos, USA) for 10 s.
After surface treatments, G2, G3, G4, and G5 were rinsed. The third roughness evaluation was performed.
For 250 ml of coffee, 15 g of powder was weighed. Five specimens of each block were immersed in 25 ml of coffee, for 24 h in an incubator (37°C ± 1°C), immediately after surface treatment (Time 0), and 1 h after (Time 1). During the waiting time, the specimens were in artificial saliva. They were cleaned with a brush in low-speed handpiece and dentifrice (Colgate Total 12, Colgate-Palmolive Company, New York, USA) for 3 s, washed, and subjected to the third color evaluation.
The differences of L* (ΔL), a* (Δa), and b* (Δb) were calculated using baseline evaluation, after bleaching, and after staining values. The ΔLb, Δab, and Δbb were obtained by the difference between baseline and after bleaching and the ΔLs, Δas, and Δbs by the difference between after bleaching and after staining. For the total difference obtained with bleaching (ΔEb) and with staining (ΔEs), a formula was applied:
ΔE = ([ΔL]2+ [Δa]2+ [Δb]2)½
The normal distribution and homogeneity of variance were analyzed with Kolmogorov–Smirnov and Levene test. The effect of surface treatments and waiting time on color maintenance was analyzed with two-way ANOVA for repeated measures. The analysis was performed for ΔE and for each CIELab coordinate (L*, a*, b*). The effects of surface treatments on roughness were analyzed using Kruskal–Wallis test. Friedman's test analyzed the roughness differences among the evaluation time points. The confidence level applied on the statistical software SPSS 17 (Statistical Product and Service Solutions, SPSS, Chicago, USA) was 5%.
| Results|| |
[Table 1] shows that bleaching was effective as the ΔEb mean values were higher than 3.3 for all groups.
|Table 1: Means (standard deviations) of the color change (ΔEb) with tooth bleaching|
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Two-way ANOVA testing showed that surface treatments (P = 0.878), waiting time (P = 0.105), and their interaction (P = 0.145) did not have an effect on the bleached enamel color maintenance. The ΔEs means and standard deviations are shown in [Table 2]. The analysis of the parameters L*, a*, and b* in isolation is not presented as it did show an effect neither on the factors nor on their interactions (P > 0.05).
|Table 2: Means (standard deviations) of the color change of bleached enamel subjected to surface treatment and to coffee staining (ΔEs), in T0 and T1|
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Kruskal–Wallis testing showed that the effects of surface treatments (Groups 1–5) on roughness were similar among the groups (P > 0.05). Friedman's test showed differences in roughness among the evaluation time points (P < 0.001) [Table 3] and [Table 4].
|Table 3: Medians (interquartile range) of roughness (Ra) according to surface treatment and time point of evaluation|
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|Table 4: Medians (interquartile range) of roughness (Rq) according to surface treatment and time point of evaluation|
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| Discussion|| |
The primary null hypothesis was accepted as surface treatments and postponing 1 h for contact with dye did not affect the color maintenance of bleached enamel. The secondary null hypothesis was rejected as surface treatments promoted a decrease in the roughness of 35% hydrogen peroxide bleached enamel.
Bleaching and staining were effective as the ΔEb and ΔEs mean values were higher than 3.3. The difference of color perceived with the human eye is ΔE >3.7. The clinical spectrophotometer (Vita EasyShade) has an excellent scanning reproduction with high accuracy. The repeatability of the readings is acceptable and comparable to a laboratory spectrophotometer; therefore, it can be considered reliable. The CIELab color system coordinates (L*, a*, b*) locate the object in a 3D color space and quantify the differences in lightness and chromaticity (ΔL*, Δa*, Δb*), for the total color difference (ΔE) calculation. The statistical analysis showed similar results for the total color difference (ΔE) and the parameters L*, a*, and b* in isolation.
Surface treatment with neutral sodium fluoride, CPP-ACPF, polyvinylpyrrolidone (PVP)-containing rinse, polishing, or artificial saliva immersion showed a significant effect on enamel roughness reduction but did not influence the bleached enamel color maintenance. Human saliva minimizes the demineralization induced by bleaching agents., In this study, the control group was artificial saliva with a neutral pH. Enamel remineralization with artificial saliva during consecutive bleaching sessions was effective in preventing staining. In our study, all specimens were maintained in artificial saliva until coffee immersion, but only the control group was stored in artificial saliva during the entire experiment so that its effect would not influence surface treatments effect,,, and treatment groups were stored in distilled water during the experiment., However, some authors maintained all groups in artificial saliva during the experiment.,,, In dynamic models in situ with an everyday-contact with human saliva for 14 days after bleaching, it was found that natural saliva minimized the enamel morphological alterations, calcium loss and microhardness reduction expected with bleaching., Bleaching with 35% hydrogen peroxide induced adverse effects on the enamel that were reversed with a 7-day storage in artificial saliva after bleaching, but it can change surface morphology only with 24 h. Other authors found no difference in the mineral content analysis of teeth stored in artificial saliva for 4 weeks after bleaching compared to bleached teeth treated with fluoride for 5 min daily, followed by storage in artificial saliva. In Mori et al. (2015), a dynamic model of bleaching agent applications interspersed with storage in saliva favored the active agent incorporation such as fluoride and CPP-ACPF. In our study, specimens that received neutral sodium fluoride and CPP-ACPF were not stored in artificial saliva so that the effects of the treatments were not altered. It is possible that this option promoted the uniformity of effects.
Enamel roughness increased with 16% carbamide peroxide and 35% hydrogen peroxide,, and the higher the hydrogen peroxide concentration, the greater the superficial roughness. We found that superficial roughness increased with 35% hydrogen peroxide, and a similar effect was found for 38% hydrogen peroxide followed by some recovery after saliva immersion.
Although avoiding colored food immediately after bleaching has been recommended to optimize the results, the influence of time was not observed with waiting times of 0 min, 60 min, and 240 min. In addition, there was no difference between waiting times of 30 and 150 min after bleaching, with coffee or red wine immersion, although significant staining was found only with wine. The potential for staining seems to depend mostly on the staining agent rather than the waiting time after bleaching. We found no difference between a waiting time of 0 and 60 min for coffee immersion on the bleached color maintenance. Drinking coffee is a common habit in many cultures, and specimen immersion for 24 h might simulate 1 month of consumption.
Fluoride absorption is enhanced on demineralized enamel. Fewer evident morphological alterations were detected on nonbleached enamel, followed by enamel treated with 2% neutral sodium fluoride after bleaching and then by bleached enamel. Bleaching with 35% hydrogen peroxide should be associated with daily fluoridation, to make enamel less susceptible to acid demineralization. Fluoride application after 38% hydrogen peroxide bleaching might reduce enamel demineralization risk. Fluoride application after bleaching and also both before and after bleaching can reduce the roughness of enamel bleached with 16% carbamide and 35% hydrogen peroxide. Our study corroborates these results for 35% hydrogen peroxide bleached enamel. However, Públio et al. evaluated the influence of artificial saliva, neutral sodium fluoride, and CPP-ACP, on bleached enamel susceptibility to smoke staining, and found that fluoride can enhance smoke staining because microporosities created after bleaching are not remineralized homogeneously. We found that 2% neutral sodium fluoride did not differ from artificial saliva on bleached enamel color maintenance after coffee staining. Moreover, there was no difference between bleached enamel staining with red wine after treatment with 1.25% and 5% sodium fluoride and the control without fluoridation.
The CPP-ACP can prevent demineralization and promote enamel remineralization,,, decreasing enamel roughness, without affecting bleaching efficacy. Casein, calcium, and phosphate are responsible for acid dissolution resistance. When CPP-ACP or CPP-ACPF is applied, the reactive part of CPP bonds to the oral biofilm. Free calcium and phosphate ions detach from CPP and are deposited on the enamel as hydroxyapatite with a higher Ca:Pratio. CPP-ACP and fluoride promote less dye absorption immediately after bleaching, with a better color stability, due to the synergistic effect of CPP-ACP and fluoride on remineralization. The CPP-ACP paste does not reduce peroxides efficacy but prevents undesirable alterations on the enamel roughness and hardness when applied before or after hydrogen peroxide bleaching. Although it may remineralize the tooth surface ,, decreasing re-staining susceptibility, in the present study, surface treatment with CPP-ACPF for 3 min did not affect bleached color maintenance but induced surface roughness decrease.
A PVP-containing rinse has been proposed to maintain dental bleaching results. The manufacturer recommends spraying it on the tooth surface after brushing and affirms that it protects against re-staining due to the Plasdone polymer. It is composed of water, sorbitol, propylene glycol, sodium lauryl sulfate, PVP, mint aroma, sodium saccharin, and methylparaben. PVP forms complexes due to hydrogen bonding with catechins and other compounds that cause staining, removing them from the dental surface. PVP is a polymer with the properties of damping and easy formation of films, making it a good coating. A rinse with Plasdone promoted a color change similar to a conventional dentifrice after 12 weeks. We did not find differences among the PVP-containing rinse and the other surface treatments on the color maintenance after staining. However, the rinse application reduced bleached enamel roughness.
Polishing with nanohydroxyapatite paste reduced the surface roughness of 38% hydrogen peroxide bleached enamel. Furthermore, polishing 38% hydrogen peroxide bleached enamel using Sof-lex disks, feltrum disks, and nanometric polishing paste produced an even less rough surface than of the nonbleached specimens. These results are in accordance with ours and might be due to the deposition of micron-sized particles in the enamel defects, resulting in decreased roughness. Frequent consumption of coffee might increase enamel staining susceptibility and its potential to re-stain. Surface polishing using impregnated feltrum disks (G5) was performed as a physical way to prevent re-staining. However, although this surface treatment did not affect bleached enamel color maintenance after coffee immersion, it decreased enamel roughness; however, its effect was similar to the other surface treatments.
This studyhassome limitations. Bovine teeth can be an alternative to human due to their similar histology. Although artificial saliva has electrolytes and minerals, there are no proteins due to the difficulty regarding their denaturation. Although surface treatments reduced the roughness, there was no effect on the bleached enamel color maintenance. We brushed specimens with dentifrice after coffee staining to simulate patients' tooth brushing habits, as in other reports,,, to evaluate the specimens intrinsic color. However, it might have influenced the uniformity of the effects as decreases extrinsic staining. Future in situ studies may determine if the surface treatments effect is superior to natural saliva regarding bleached enamel color maintenance and roughness.
| Conclusions|| |
Surface treatments (2% neutral sodium fluoride, CPP-ACPF, PVP-containing rinse, and polishing with feltrum disks impregnated with aluminum oxide) were similar to artificial saliva and did not affect bleached enamel color maintenance. Immediate or 1-h postponed contact with coffee did not affect bleached enamel color. Bleaching increased enamel roughness, but the surface treatments decreased it to lower values than baseline.
We thank CNPq for scholarships (161092/2013-6 and 350106/2014-2); FGM, Nova DFL, DMC and Shofu for the donated products and “Pró-reitoria de Pesquisa” (UFMG) for the English editing.
We had the support of CNPq for scholarships (161092/2013-6 and 350106/2014-2); FGM, Nova DFL, DMC and Shofu for the donated products and “Pró-reitoria de Pesquisa” (UFMG) for the English edition.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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Dr. Débora Drummond Hauss Monteiro
Department of Restorative Dentistry, School of Dentistry, Universidade Federal De Minas Gerais, 6627, Avenida Antonio Carlos, Pampulha, CEP 31270-901 - Belo Horizonte, Minas Gerais
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2], [Table 3], [Table 4]