Effect of surface treatments on staining and roughness of bleached enamel

The effect of ascorbic acid and cranberry on the bond strength, surface roughness, and surface hardness of bleached enamel with hydrogen peroxide and zinc phthalocyanine activated by photodynamic therapy

AIM

To evaluate the effect of different bleaching methods 40% (hydrogen peroxide) HP and Zinc Phthalocyanine (ZP) activated by photodynamic therapy (PDT) with the utilization of diverse procedures of reversal (10% ascorbic acid and 6% cranberry solution) on bond values, surface microhardness and surface roughness of bleached enamel surface.

MATERIAL AND METHODS

An aggregate of 60 extracted human mandibular molars was gathered and the buccal surface of each specimen was exposed to 2 mm of enamel surface for bleaching with chemical and photoactivated agents with the use of reversal solutions. Specimens were divided into six groups (n = 10) at random- Group 1: samples bleached with 40% HP with 10% ascorbic acid (reversal agent), group 2: ZP activated by PDT with 10% ascorbic acid (reversal agent), group 3: 40% HP with 6% cranberry solution as a reversal agent, group 4: ZP activated by PDT with 6% cranberry solution, group 5: 40% HP and group 6: ZP activated by PDT with no reversal agents. Resin cement restoration was performed via etch and rinse technique and SBS was estimated by using the universal testing machine, SMH by using Vickers hardness tester, and Ra by stylus profilometer. Statistical analysis was executed using the ANOVA test and the Tukey multiple tests (p<0.05).

RESULTS

Enamel surface bleached with 40% HP reversed with 10% ascorbic acid displayed the highest SBS while 40% HP with no reversal agent use showed the least SBS. For SMH, ZP activated by PDT when applied on the enamel surface and reversed with 10% ascorbic acid showed the highest SMH while when bleached with 40% HP and reversed with 6% cranberry solution showed the least SMH value. For Ra, Group 3: samples bleached with 40% HP with 6% cranberry solution as reversal agent showed the highest Ra value while bleaching of enamel surface with ZP activated by PDT with 6% cranberry displayed the least Ra value.

CONCLUSION

Bleached enamel surface with Zinc Phthalocyanine activated by PDT with the application of 10% ascorbic acid as reversal solution has demonstrated the highest SBS and SMH with acceptable surface roughness for bonding adhesive resin to the enamel surface.

Effect of Activated Charcoal Toothpaste on Color Stability of Bleached Teeth Immersed in Different Drinks

OBJECTIVE

This study aimed to evaluate the effect of activated charcoal toothpaste on the color stability of teeth subjected to tooth bleaching and pigmenting agents.

METHODS

A total of 120 bovine crowns were randomly divided into 12 groups (n=10) according to two study factors: staining solutions (three levels): saliva (control), coffee, and red wine; and toothpaste (four levels): BPC, Bianco Pro Clinical (Bianco Oral Care) (Control); BIW, Black is White (Curaprox); BCA, Bianco Carbon (Bianco Oral Care); and NAT, Natural Suavetex (Suavetex). The samples were subjected to office bleaching with a 35% hydrogen peroxide-based gel (Whiteness HP Blue, FGM), followed by immersion in the solution for 45 minutes per day and daily toothbrushing for 7 days. The color (ΔE) and luminosity changes (ΔL*) were measured using reflectance spectroscopy (Vita EasyShade). The CIE values (L*, a*, b*) were measured at baseline after bleaching (T0) and immediately after immersion in solution each day (Ti1-Ti7) and after all toothbrushing cycles (Tb1-Tb7). ΔE and ΔL were analyzed using a two-way analysis of variance and Tukey's test (α=0.05). The clinically unacceptable level of ΔE > 3.3 was used to evaluate the color change.

RESULTS

The color change was significantly influenced by the staining solutions and toothpastes (p<0.001). The color change (ΔE) was significantly higher when immersed in wine than in coffee, and lower ΔE values were observed for artificial saliva (control), irrespective of the toothpaste used. In artificial saliva, BPC, BIW, and BCA resulted in significantly lower ΔE values than NAT, which presented a clinically unacceptable level of dental color change (ΔE>3.3). Coffee resulted in a lower (L*) reduction than wine, irrespective of the toothpaste used.

CONCLUSION

Charcoal toothpastes resulted in a color change on the surface of the tooth enamel (ΔE). The bleaching effect of the charcoal toothpastes and control evaluated in this study partially reduced the color changes on the surface of the tooth enamel caused by staining solutions but was unable to reestablish the measured values to the baseline. For teeth immersed in artificial saliva, the color change was not noticeable in BCA, BIW, and control-BPC (ΔE≥3.3), except for NAT, which showed a significant color change.

The impact of remineralization agents on dental bleaching efficacy and mineral loss in bleached enamel

This study evaluated the effect of remineralization agents on bleaching efficiency, enamel mineral changes, and post-bleaching color stability. A total of 112 enamel-dentin blocks were prepared from bovine teeth. Following initial color measurements, separate treatment regimens were carried out as follows: negative control (no treatment); positive control (bleaching only); bleaching, then NaF; bleaching + NaF (mix); bleaching, then CPP-ACPF; bleaching + CPP-ACPF (mix); bleaching, then nHAP+F; bleaching + nHAP+F (mix). Color measurements were repeated after immersion in distilled water for 7 days, and again after staining with coffee solution for 14 days. The CIELAB-based whiteness index was used to evaluate bleaching efficiency, and the CIEDE2000 color difference formula for color stability. Chemical investigation was performed using scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction analyses. The experimental groups showed significant increases in whiteness compared to the negative control, and the staining after bleaching did not result in statistically significant differences between the groups. Energy dispersive spectroscopic analysis revealed that bleaching protocols had no impact on elemental levels as well as the ratio of Ca/P. The combined use of bleaching agents with remineralization agents did not affect bleaching effectiveness but also did not provide an additional contribution.

Does polishing of bleached enamel affect roughness and tooth color stability after exposure to coffee?

OBJECTIVE

This laboratory randomized study was designed to evaluate the effect of polishing on roughness and color stability of bleached teeth after coffee immersion.

MATERIALS AND METHODS

Ninety bovine crowns were randomly allocated to six groups (n = 15), according to bleaching protocols: At-home: standard protocol using 10% hydrogen peroxide (HP) or In-office: standard protocol using 35% HP; and with polishing protocols: (1) no polishing, (2) bleached enamel polished with #0.5 μm or (3) #2-4 μm diamond particles grit pastes. Samples were daily immersed into coffee solution for 45 min followed by mechanical brushing simulation (30 s) for 30 days. The surface roughness (Ra) and color alteration, expressed by ΔEab , ΔE00 , and whitening index (WI) were analyzed at baseline, after bleaching/polishing protocols and after coffee solution staining. The surface from each group was examined using a scanning electron microscope. Data were analyzed by two-way repeated measure analysis of variance followed by the Tukey test (α = 0.05).

RESULTS

Staining increases Ra, ΔEab , ΔE00 , and decreases WI values. Polishing after bleaching did not prevent staining, however, tooth polished with #0.5 μ-grit polishing paste showed better performance than #2-4 μ-grit (ΔEab : p = 0.001/ΔE00 : p = 0.003). Scanning electron microscope revealed a more irregular surface after coffee staining for all groups regardless bleaching/polishing protocols.

CONCLUSIONS

Using #0.5 μ-grit diamond paste to polish 35%HP in-office bleached enamel reduces the roughness and tooth staining. However, polishing after 10%HP at-home bleached enamel neither affects roughness nor improves tooth color stability after exposure to coffee.

CLINICAL SIGNIFICANCE

Polishing after at-home bleaching does not have benefits but after 35% hydrogen peroxide in-office bleaching, the polishing with #0.5 μ-grit polishing paste is indicated to reduce roughness and the tooth staining over time.

Surface Morphological Changes and Predisposition to Staining in Dental Enamel Bleached with Different Hydrogen Peroxide Concentrations

Background:

The tooth bleaching treatment can cause structural changes in the surfaces of the teeth; these changes can increase the absorption of staining agents.

Purpose:

This study assessed surface morphological changes and predisposition to staining in dental enamel bleached with different hydrogen peroxide (HP) concentrations, with or without the use of a light source (LS).

Methods:

25 bovine incisor specimens were divided into five groups (n = 5): Control- no treatment; HP35 - hydrogen peroxide 35%; HP35+LED - hydrogen peroxide 35% + light emission; HP20 - hydrogen peroxide 20%; and HP7 - hydrogen peroxide 7,5%. Twenty days after bleaching, the specimens were immersed in staining solutions four hours a day for 28 days. The morphological alterations of the bovine enamel surface were evaluated by means of scanning electron microscopy, X-ray dispersive energy spectroscopy and predisposition to the staining of the brightened enamel by means of colorimetry.

Results:

ANOVA with Tukey's test (p<0.05) showed that HP7 had the highest ΔL values (p=0.176) (brightest), with a better lightening effect. The bleached groups exhibited morphological changes in the enamel. The groups did not exhibit significant changes in oxygen, calcium, and phosphorus values (p=0.020). The presence or absence of light was not significant (p=0.007) for the predisposition to staining in bleached teeth.

Conclusion:

The time of exposure to the staining solution was significant for staining bovine dental enamel. High concentrations of HP were not necessary for achieving effective bleaching. HP caused an increase in enamel porosity and depressions. The light source did not influence bleaching.

Effect of bleaching agents on hardness, surface roughness and color parameters of dental enamel

Background

In this study was evaluated the effect of carbamide peroxide (CP) and hydrogen peroxide (HP) in different concentrations on hardness, roughness, and color parameters (color change - ΔE, lightness - ΔL, and yellow-blue axis - Δb) of bovine teeth.

Material and Methods

Fifty square dental blocks (7 x 7 x 2 mm) were submitted to initial readings of Knoop hardness, surface roughness (Ra), and color parameters. Specimens were divided into 5 groups (n = 10): control group was kept in artificial saliva during the experimental period; CP 20% was bleached for 2 h daily for 14 days, HP 9.5% was bleached for 30 min daily for 14 days, HP 38% the bleaching gel was applied for 15 min, gel was removed and it was reapplied for two more times, the bleaching session was repeated for another 2 times every 7 days, totaling three sessions, and in CP 45% three sessions of 30 min each were performed of 7 in 7 days. All groups after the bleaching procedures had the bleaching gel removed, washed, and kept in artificial saliva. At the end of bleaching treatment, the hardness, roughness, and color parameters (ΔE, ΔL, and Δb) were re-evaluated. Data were analyzed by ANOVA, Tukey, and Dunnett tests (α = 0.05).

Results

Bleaching promoted a reduction in hardness, the CP 45% showed the lowest hardness and the CP 20% the highest, the HP 9.5% and HP 38% showed intermediate values of hardness. Bleaching agents did not affect the roughness. CP 20% and HP 38% promoted the highest values of ΔE and higher reduction of yellowish tone of tooth. Lightness increase after bleaching treatment for all groups.

Conclusions

All the bleaching agents tested showed effectiveness, but with reduced hardness.

Key words:Carbamide peroxide, hydrogen peroxide, tooth whitening, hardness, roughness.

Metal Ion Accumulation on Denture Teeth Following Exposure to Chlorhexidine and Different Drinks: A Spectrometric Analysis

Denture teeth are used for removable prostheses and implant-supportive restorations. The purpose of this study was to analyze the surface of artificial teeth following exposure to different liquids. Mechanical wear and the cleaning of artificial teeth were also investigated. Two groups of resin teeth were used; original surface (Group A) and surface abrasion/wear (Group B). The teeth were exposed for 24 h to water (control), cola (Group 1), coffee (Group 2), tea (Group 3), chlorhexidine (Group 4), and red wine (Group 5). Baseline measurements of liquids were taken. An x-ray fluorescence spectrometric analysis was performed. Data were evaluated using semi-quantitative descriptive analysis. The data showed approximate increases of peak intensity for Group A1-2-fold Fe, 2-fold Ni, 2.2-fold Zn; for Groups A2 and A3- less than 1.5-fold Fe, Ni, and Zn. Group B yielded similar results; however, the increases in Fe, Ni, and Zn were significantly higher in Groups 1 and 2 (ranged 2-4-fold increases in intensity). Group B3 showed little increase in Fe, Ni, and Zn. Groups A4 and A5 showed intensity increases for Zn. Groups A1-A5 showed reductions in intensity following 30 s of cleaning. A pronounced accumulation of iron, nickel, and zinc was found after exposure to liquids, especially when artificial teeth were worn down. Peak intensities were reduced following 30 s of brushing.

Evaluation of the effect of tooth polishing on color stability after in-office bleaching treatment

Abstract Introduction One of the most commonly used corrective methods for staining teeth is tooth bleaching. However, subclinical alterations may occur in the micromorphology of dental tissues during the bleaching procedure, such as increases in porosity and surface roughness. Consequently, dental enamel may become more permeable and susceptible to staining. Objective To evaluate the influence of tooth polishing after in-office bleaching treatment on color stability. Material and method Thirty-three extracted human molars were used. The teeth were cut in the mesiodistal direction to obtain two samples per tooth (total of 66). The samples were randomly divided into six groups (n=11). Before and after the bleaching treatment, the lightness of the samples and change in lightness (∆L) were determined with a digital spectrophotometer (Easy Shade). The samples were bleached with 35% hydrogen peroxide (three sessions weekly). Three groups were submitted to polishing with felt discs and polishing paste after each session. To simulate the oral conditions during the consumption of colored beverages, the samples were submitted to alternating cycles of immersion in staining solutions (coffee, red wine, and Coca Cola). Result Polishing resulted in an increase of mean lightness of 4.49 in the red wine group, 2.73 in the coffee group, and 4.08 in the cola group. The difference was significant in the red wine group (p<0.022), but not in the coffee or cola group. Conclusion Polishing after in-office bleaching using felt discs and polishing paste can reduce the degree of pigment impregnation in patient with red wine rich diet.

Does comsumption of staining drinks compromise the result of tooth whitening?

Background

After dental bleaching procedures dentists commonly advise patients to reduce the consumption of beverages that may cause the teeth to stain, however, the effectiveness of teeth whitening may not be directly affected by diet.

Material and Methods

It was evaluated through in vitro study whether contact with dyes through in-office bleaching sessions with 35% hydrogen peroxide would influence the effectiveness of treatment. Sixty bovine incisors were randomly assigned into 5 groups (n = 12) according to contact frequency and type of dye solutions. All dental elements received three in-office bleaching sessions with 35% hydrogen peroxide one week apart. Except for GCTRL (control), all experimental groups were submerged in dyes (coffee or wine) for 5 min once a day. In groups GC24 and GW24 contact with the dyes was made from 24 hours after each bleaching session, while in groups GC72 and GW72, from 72 hours. The color was measured with a digital spectrophotometer. Data were expressed as statistics: mean and standard deviation.

Results

Contact with dyes during in-office bleaching treatment with 35% hydrogen peroxide did not influence the staining averages after three bleaching sessions. The speed of the whitening effect was influenced by contact with coffee from 24 hours after the sessions and with wine from 24 hours and 72 hours after the whitening session. The whitening result was reversed after one week for all groups, especially for groups that came in contact with red wine either 24 hours or 72 hours after session and coffee after 24 hours.

Conclusions

Contact with dyes during in-office bleaching treatment did not influence the final staining averages after three bleaching sessions although there was influence on speed of the whitening effect between the sessions. Key words:Tooth bleaching, hydrogen peroxide, spectrophotometry.