Effect of aging and bleaching on the color stability and surface roughness of a recently introduced single-shade composite resin

OBJECTIVES

To assess the effects of aging and bleaching procedures on the color stability and surface roughness of a new single-shade composite versus multi-shade composite resins.

METHODS

A single-shade composite resin (Charisma Diamond One, CDO) and 3 multi-shade composite resins (Tetric NCeram, Filtek Z350 XT, Clearfil Majesty Posterior) were tested. Thirty specimens of each material were subjected to one of the aging procedures respectively: immersion in distilled water (12 days/37 °C), immersion in coffee (12 days/37 °C), or water thermocycling (10,000 cycles/5-55 °C). All specimens underwent in-office bleaching after aging. Kruskal-Wallis tests and analysis of variance were used for statistical analysis (α=0.05).

RESULTS

All materials exhibited a change of color (ΔE00), translucency (RTP), whiteness (WID) and surface roughness parameters (Sa,Sv) after aging and bleaching procedures. CDO showed the highest ΔE00 among all resins with the highest RTP value, regardless of the aging procedures. Immersion in coffee led to the significantly highest ∆E00 values and lowest RTP values for nearly all resins. Positive ΔWID1 (WID(bleaching)-WID(baseline)) values were found in distilled water immersion and thermocycling groups, while negative ΔWID1 values were found in the coffee immersion group for all materials. Besides, positive ΔWID2 (WID(bleaching)-WID(aging)) values were found in all aging groups for nearly all materials. All materials showed an increasing trend in Sa and Sv after bleaching.

CONCLUSIONS

CDO showed more pronounced discoloration than multi-shade composite resins. Although the whiteness of all resins increased after bleaching, none was completely restored in the coffee immersion group. Bleaching significantly increased the surface roughness of all materials.

CLINICAL SIGNIFICANCE

Charisma Diamond One is more susceptible to discoloration, which may affect its long-term success rate. Bleaching could partially reduce the color change of the composite resins but did not return them completely to their original state. The roughness of the resins increased after bleaching, prompting dentists to repolish them after bleaching.

Influence of Thickness on the Translucency Parameter and Whiteness Index of Single-Shade Resin Composites

The study aimed to evaluate the effect of thickness on the translucency parameter (TP) and whiteness index for dentistry (WID) of single-shade resin composites compared with a multi-shade resin composite after thermocycling. A total of 100 resin composite samples of five brands (Filtek Z250, Omnichroma, Vittra APS Unique, Zenchroma, and Charisma Diamond One) with thicknesses of 2 mm and 4 mm were prepared (n=10). CIE L*a*b* coordinates were obtained using a spectrophotometer. The resin composite samples were subjected to 10,000 thermocycles. Before and after thermocycling, TP values were calculated with the CIEDE2000 formula, and whiteness values were calculated using the WID. The influence of thickness, resin composite, and aging on these variables was analyzed using the generalized linear model (p<0.05). Omnichroma and Filtek Z250 exhibited, respectively, the highest and the lowest TP00 values compared with the other resin materials (p<0.001). The TP00 values of Zenchroma and Diamond One were similar (p>0.05). Vittra APS Unique had a lower TP than Zenchroma and Diamond One (p<0.001). Before thermocycling, the highest WID showed the combination of Vittra APS Unique with thicknesses of 2 mm (48.33±1.18). After thermocycling, the highest WID was shown in the combination of Vittra APS Unique with thicknesses of 2 mm (45.33±0.55) and 4 mm (46.23±0.94) (p<0.001). After thermocycling, the lowest WID was for the combination of Filtek Z250 with thicknesses 2 mm (21.16±0.93) and 4 mm (20.70±0.91) (p<0.001). The TP and WID values of the resin composites varied across different composites and thicknesses. Single-shade resin composites of different thicknesses demonstrated higher translucency and whiteness values than multi-shade resin composite, both before and after thermocycling.

Color match of single-shade restorations after professional dental bleaching: An in vitro study

Background

Restorative dentistry aims to reproduce natural tooth shades through resin composites that must be layered to obtain colors, opacities, and translucencies, and therefore, clinical success is operator skill dependent.

Aims

The purpose of this study is to evaluate the color shift of single-shade composite restorations before and after dental bleaching.

Materials and Methods

Eighty human extracted posterior teeth were restored with four single-shade composites (Omnichroma OM; Clearfil Majesty ES-2 Universal CL; Essentia Universal ES; Venus Diamond One VE) (n = 20 each). Standardized V class cavities were prepared on buccal side. VITA Easyshade V spectrophotometer was used to register VITA color and color coordinates 24 h before (T0), 24 h after (T1), and 1 week after (T2) dental bleaching (Opalescence Boost PF 40%). Color differences (ΔEab) and (ΔWID) were calculated and subjected to statistical analysis.

Statistical Analysis

Categorical variables were analyzed using Pearson Chi-square, and data from color coordinates were analyzed using one-way analysis of variance and Tukey's multiple comparison test with Bonferroni correction. Paired t-tests were performed to compare continuous measures between groups and treatment time.

Results

Instrumental evaluations revealed statistically significant differences between materials (P < 0.05) with lower values for ES and VE samples followed by CL and OM at T0 and T1. At T2, OM and CL ΔEab values decrease getting closer to ES and VE.

Conclusion

Single-shade composites seem to match with the surrounding bleached tooth.

Color match analysis of single-shade and multi-shade composite resins using spectrophotometric and visual methods after bleaching

The aim of this study is to evaluate the color match of the materials after the staining and bleaching procedures applied to the teeth restored with single-shade and multi-shade composite resins. Cavities prepared on the facial surface of human incisors were restored with two different composite resins. After 24 h, the color matching parameters between the initial filling-tooth of the samples were recorded. Then, the color measurements of the samples subjected to the coloring process were repeated. Each composite resin group was randomly divided into 2 subgroups and home and office bleaching methods were applied to the samples. After bleaching, color measurements were repeated. In terms of periods, a statistically significant difference was found in ΔE values 1 day and 28 days after bleaching (p<0.05). In addition, it was found that the color match between filling-tooth was generally weaker in Omnichroma material and after home bleaching.

Effect of layering strategy and prolonged water aging on masking ability of composite resins

STATEMENT OF PROBLEM

Layered composite resins may adequately mask discolored substrates. However, whether color changes that occur over time affect masking ability is unclear.

PURPOSE

The purpose of this in vitro study was to investigate the effect of layering and water aging on the masking ability of 2 composite resins.

MATERIAL AND METHODS

Disk specimens (1.5 mm-thick and shade A1) from Charisma Diamond (CD) and Filtek Z350XT (Z350) were made according to the composite resin shade combination used in the layering strategies: bilayer for CD (enamel/dentin) and for Z350 (enamel/body and enamel/dentin) and trilayer for Z350 (enamel/body/dentin) (n=5). Color measurements were obtained with a spectrophotometer over an A3.5 ceramic substrate, and the whiteness index for dentistry (WID) was calculated. The specimens were aged in water at 37 °C and evaluated at different times: 24 hours, 1 week, 1 month, 2 months, 6 months, 12 months, 18 months, and 24 months. CIEDE2000 color differences (ΔE00) and WID differences (ΔWID) were calculated and interpreted by 50:50% color and whiteness perceptibility and acceptability thresholds. Changes among strategies and aging times were analyzed using the Kruskal-Wallis test (α=.05). Contrasts were made using the Mann-Whitney U test with Bonferroni correction (α=.001).

RESULTS

ΔE00 decreased from 24 hours to 2 months of aging. From 2 months onwards, ΔE00 increased for all layering strategies and times, without significant changes in lightness for CD (P>.004). Overall, for the CD restorative system, an increase in ΔWID was observed after 1 month of aging (P<.001), while for the Z350 restorative system, ΔWID decreased after aging (P<.001), except for the Z350 bilayer strategy (enamel + dentin) at 1 week and 2 months (P>.004). For all layering strategies and aging times, color differences were higher than the 50:50% perceptibility threshold for ΔE00 and, after 6 months, higher than the 50:50% acceptability threshold for ΔE00 and the 50:50% whiteness acceptability threshold.

CONCLUSIONS

The ability of the tested composite resins to mask a discolored substrate was affected by the layering approach applied and by prolonged water aging.

Efficacy of microabrasion and resin infiltration techniques for masking of fluorotic white spot lesions: A randomized clinical study

Aim

The aim of the study was to compare the esthetic treatment outcome and quantification of tooth color changes using microabrasion and resin infiltration techniques of fluorotic white spot lesions (WSLs).

Subjects and Methods

Sixty-six teeth with fluorotic small opaque white areas involving 25%-50% (very mild/mild fluorosis) of the surface were randomly assigned into two groups for microabrasion and resin infiltration techniques. To quantify tooth color changes, depicted by Delta E (DE), photographic analysis was performed using Adobe Photoshop CS5 Extended version by measuring Commission Internationale de l'Eclairage L*a*b* values of each tooth at two points, i.e. one at WSL and the other one at sound adjacent enamel.

Statistical Analysis Used

Data were analyzed with t-test using SPSS software version 23.

Results

L*value (decrease in whiteness) of posttreatment WSL decreased in both groups but was higher in the resin infiltration group, which was statistically significant. There were no statistically significant changes observed in a* and b* values of WSL in both groups. DE value difference of pre and postoperative was higher in the resin infiltration group, which was statistically significant which indicated the stability of color obtained by the resin infiltration group.

Conclusions

Resin infiltration technique is more efficient in the immediate elimination of fluorotic WSL than microabrasion.

The influence of smoking on the effectiveness of at-home bleaching: A prospective clinical study

OBJECTIVES

To evaluate the effect of smoking on tooth whitening and color change after at-home bleaching.

MATERIALS AND METHODS

This prospective clinical study evaluated two groups of participants: NS-non-smokers (n = 24) and S-smokers (n = 16). All subjects were treated with at-home bleaching using 22% carbamide peroxide (CP) for 1 h/day for 14 days. Color coordinates (L*-luminosity, a*-red-green axis and b*-yellow-blue axis) were obtained before bleaching (D0-baseline), 1 day (D1), 15 days (D15), and 1 month (D30) after bleaching. The whiteness index (WID ) and CIEDE2000 color differences (ΔE00 ) were calculated for S and NS. Color changes between S and NS subjects for specific teeth (CI-Central Incisors, LI-Lateral Incisors, and C-Canines) were analyzed using the Mann-Whitney test (α = 0.05).

RESULTS

There was no significant difference in WID between S and NS subjects at baseline. NS participants showed higher WID than S at D1, D15, and D30 (p < 0.05). NS showed higher ΔWID for CI and C between D0 and the other evaluation times (D1, D15, and D30) compared to S. Smokers showed higher darkening of CI than NS in ΔWID D30-D1 (p < 0.05). Color changes showed similar overall behavior for ΔWID . For all evaluation times, ΔWID and ΔE00 values were below the corresponding acceptability thresholds.

CONCLUSION

At-home bleaching was effective on smokers and nonsmokers. Smoking negatively affected color stability after bleaching. ΔE00 and ΔWID were acceptable for both groups.

CLINICAL SIGNIFICANCE

Although smoking negatively affected color stability after bleaching, the observed changes were clinically acceptable.

The impact of the diode laser 940 nm photoactivated bleaching on color change of different composite resin restorations

The study's main objective was to evaluate as well as compare the impact of diode laser 940 nm and conventional in-office bleaching technique on the color change of different composite resin restorations. A total of ninety composite resin discs (CRDs) were made from Filtek™ Bulk Fill, nanohybrid composite resin Filtek™ Z550 XT Universal Restorative, and flowable composite resin restoration Filtek™ Z350xt Flowable Composite. Group A: (30) CRD for Filtek™ Bulk Fill, group B: (30) CRD for Filtek™ Z550 XT Universal Restorative, and group C: (30) CRD for Filtek™ Z350xt Flowable Composite. A1, B1, and C1: (10 CRD in each group): Control group without bleaching. A2, B2, and C2: 10 CRD in each group bleached with Laser White20 without laser activation. A3, B3, and C3: 10 CRD in each group bleached with Laser White20 and activated by diode laser 940 nm. The color was evaluated using a dental spectrophotometer. One-way ANOVA was utilized for the comparison of the color stability of the CRD. P < 0.05 is regarded as statically significant. Both conventional and diode laser in-office vital tooth bleaching protocols affected the color stability of composite resin restorations. The result demonstrated that bleaching without laser activation produced color change (mean [8.30], standard deviation [SD] (1.95) P [< 0.001]), whereas the bleaching and activation by diode laser produced color change (mean [8.11], SD [1.99], P [< 0.001]). Both types of bleaching protocol affected composite resin restorations' color stability. In all tested materials, color changes after the bleaching protocol were clinically perceptible. The restorations following the bleaching procedure are required to be replaced by clinicians.

Effects of different toothpastes on the color and whiteness of stained anterior composite resin

PURPOSE

To evaluate changes in the color of an anterior nanohybrid composite resin and differences in its whitening index after 30 days of brushing with six brands of whitening toothpaste in vitro to simulate the situation in individuals with high coffee consumption.

METHODS

Eighty-four disk-shaped resin specimens were prepared (shade A2). For initial staining, the samples were immersed in coffee solution for 14 days and then divided into eight groups for treatment with various toothpastes. Color was assessed at the baseline, after initial staining, and on days 7, 14, and 30 of the staining-and-brushing cycle. Color stability was evaluated based on the CIEDE2000 color difference (ΔE00), and differences in whiteness were determined using the whitening index for dentistry (WID).

RESULTS

The highest ΔE00 and ΔWID values were obtained with Colgate Herbal, followed by Opalescence Whitening and Crest Baking Soda and Peroxide, whereas the lowest values were obtained with distilled water, followed by Yotuel Pharma B5, on day 30 of the staining-and-brushing cycle.

CONCLUSION

In terms of improving the color and whiteness of coffee-stained anterior nanohybrid composite resin, Colgate Herbal, Opalescence Whitening, and Crest Baking Soda and Peroxide yielded promising results after 30 days of continuous use.

The effect of bleaching applications on stained bulk-fill resin composites

Background

The structure of bulk-fill resin composites differs from that of their conventional counterparts, but how this difference affects the color stability of the former after staining and bleaching is unclear. Accordingly, this study was aimed at investigating color change in nine bulk-fill resin composites and one nanohybrid resin composite treated with hydrogen peroxide and carbamide peroxide after staining with tea, coffee, and red wine.

Methods

Eighty specimens were prepared from each resins [Clearfil Majesty Posterior (CMP), SDR flow⁺ (SDR), Filtek^TMBulk-Fill Flowable Restorative (FBF), Reveal HD Bulk (RHD), Beautifil-Bulk Restorative (BBR), Tetric EvoCeram® Bulk Fill (TEC), SonicFill™2 (SF2), everX Posterior™ (eXP), X-tra base (XB), and Venus® Bulk Fill (VBF)]. Following baseline color measurements, the specimens were randomly divided into 4 groups according to immersion solutions and distilled water as the control. At the end of a 30-day test period, color measurements were repeated, and color change values (∆E₀₀) were calculated. Each resin group was then divided into 2 subgroups (with 10 specimens per group) on the basis of bleaching agent (Opalescence Boost 40%, Opalescence PF 16%). Following bleaching application, ∆E₀₀ and changes of whiteness (∆WI_D1 = WI_Dbleaching-WI_Dbaseline, ΔWI_D2 = WI_Dbleaching-WI_Dstaining) values were recorded. Two- and three-way analyses of variance and Tukey’s post hoc test were performed, with a P < 0.05 regarded as indicative of significance.

Results

After immersion in distilled water, tea, and red wine, the highest ΔE₀₀ values were observed in eXP (P < 0.05). Resin materials immersed in coffee and tea exhibited statistically higher ∆E₀₀ values than those immersed in red wine except for eXP, TEC, and FBF (P < 0.05). For eXP, the highest ∆E₀₀ values were recorded in distilled water. For TEC and FBF, there was no statistically significant difference among the immersion solutions and distilled water (P > 0.05). For all the resins and staining beverages, no statistically significant difference in ∆WI_D1 and ∆WI_D2 values were detected between bleaching agents (P > 0.05). All the ΔWI_D1 values were above the whiteness perceptibility threshold.

Conclusion

The bulk-fill materials were more resistant to discoloration and bleaching procedures than the conventional resin composites. Coffee and tea caused more staining than distilled water and red wine generally. The type of bleaching procedure had no effect on the whiteness of the tested materials.

Effects of long-term cinnamaldehyde immersion on the surface roughness and color of heat-polymerized denture base resin

STATEMENT OF PROBLEM

Cinnamaldehyde has been successfully used for the short-term disinfection of dentures; however, its long-term effects on the surface and color properties of denture base materials remain unknown.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of simulated immersion in cinnamaldehyde for up to 5 years on the surface roughness and color parameters of a heat-polymerized denture resin.

MATERIAL AND METHODS

Eighty Ø10×5-mm disk-shaped specimens were prepared from microwave heat-polymerized polymethylmethacrylate (PMMA) and immersed in 4 solutions (n=20): TW-tap water (control), SH - 0.5% sodium hypochlorite, PX-alkaline peroxide, and CA-cinnamaldehyde (27 μg/mL). The immersion protocol simulated 104 cycles (3.5 months), 913 cycles (2.5 years), and 1825 immersion cycles (5 years) of a daily immersion cleaning protocol, with immersion times ranging from 10 to 20-minutes. Surface roughness (Sa) and the color parameters of CIELab (L∗ a∗ b∗, ΔEab), CIEDE2000 (ΔE00), and the National Bureau of Standards (NBS) were analyzed at baseline (t=0) and after the immersion cycles. The data were analyzed by 2-way analysis of variance (ANOVA) for repeated measures and the Tukey post hoc test (α=.01).

RESULTS

Sa was significantly increased in all groups after 1825 cycles compared with baseline (P<.01), regardless of the solution. Only the time factor significantly affected ΔEab, ΔE00, and NBS parameters, which were below the perceptibility and acceptability thresholds. After a simulated 5-year immersion, the surface roughness and color values of CA-treated specimens were not statistically different from those of the other groups (P>.01).

CONCLUSIONS

Cinnamaldehyde solution (27 μg/mL) produced minor effects on the surface roughness and color parameters of a heat-polymerized denture base resin similar to those of 0.5% sodium hypochlorite and alkaline peroxide after a 5-year simulated immersion.

Color prediction of layered dental resin composites with varying thickness

OBJECTIVE

The aim of this study was to assess the accuracy of a Principal Components Analysis (PCA)-based method for reflectance reconstruction and color estimation of layered dental resin-based composites with different thicknesses.

METHOD

Bi-layered samples of different clinically relevant thicknesses were created using shades of VITAPAN Excell (VE), VITAPAN Dentine (VD) and VITA Physiodens (VP), combined with their corresponding enamel shades. Spectral reflectance of all samples was measured over a black background using a non-contact spectroradiometer with CIE 45^∘∕0^∘ geometry. Two different PCA-based models, built from two different configurations of known samples, were proposed to reconstruct the spectral data and color of unknown layered samples. Root Mean Square Error (RMSE), Goodness of Fit (GFC), as well as ΔE₀₀ with corresponding 50:50% acceptability and perceptibly thresholds (AT and PT) were used as performance assessment.

RESULTS

The 5-samples training set approach provided an average RMSE < 0.015 and GFC > 0.999 when measured and predicted spectral reflectances were compared, while for the 9-samples training set, RMSE < 0.0098 and GFC > 0.9999 were obtained. The overall mean color differences obtained with the 5-samples training set approach were ΔE₀₀ = 0.99 (AT% = 96.25% and PT% = 32.50%), while using the 9-samples training set resulted in lower overall mean color differences: ΔE₀₀ = 0.50 (AT% = 99.22% and PT% = 83.87%).

SIGNIFICANCE

Within the framework of this study, the two proposed PCA-based configurations allow the prediction of the spectral reflectance of layered dental resin-based composites of different shades and thicknesses, with a high degree of accuracy.

Masking Ability of the Combined Application of Opaquers and Resin Composite on Discolored Backgrounds

The aim of this study was to evaluate the masking ability of a combined application of opaquers and resin composite over discolored backgrounds: A3, A3.5, C2, C3, and C4. The groups were divided according to the opaquer brand, the number of opaquer coats (one or two), and the thickness of the resin composite layer (0.5 or 1.0 mm). The color measurements were made by a reflectance spectrophotometer (SP60, EX-Rite). The color difference between the opaquer + resin composite + background and a reference background was calculated using the CIEDE2000 formula. ANOVA and Tukey's post hoc test (α=0.05) were used to analyze the ΔE00 mean values. A bivariate analysis was used to determine the association between dependent and independent variables. The masking ability was rated by the ΔE00 visual thresholds of acceptability and perceptibility (Excellent Match: ΔE00 ≤ 0.8; Acceptable Match: 0.8 < ΔE00 ≤1.8; Moderately Unacceptable Mismatch: 1.8 < ΔE00 ≤ 3.6; Clearly Unacceptable Mismatch: 3.6 < ΔE00 ≤ 5.4; Extremely Unacceptable Mismatch: ΔE00 > 5.4). The mean ΔE00 values ranged from 0.5 to 5.52. Masking ability was affected by the opaquer brand, thickness of the resin composite layer, and background shades. Most of the combinations that achieved either excellent or acceptable masking ability were obtained with combinations composed of one or two coats of opaquer and a 1.0-mm-thick resin composite layer for all backgrounds except C4. Acceptable results were also obtained for combinations with 0.5-mm-thick resin composite over C2, A3, and A3.5 backgrounds.

Color Change of Resin-based Composites After In Vitro Bleaching Protocols: A Systematic Review and Meta-analysis

OBJECTIVES

To systematically review the literature on color stability of resin-based composites (RBC) after in vitro bleaching protocols and to assess the influence of bleaching protocols by meta-regression analysis on RBC color stability, and the association with clinical and experimental characteristics.

METHODS

The electronic search was conducted in MEDLINE/PubMed, Scopus, and Web of Science databases and included English language studies that evaluated and reported color differences (CIELAB values) of RBC after in vitro bleaching procedures using hydrogen peroxide and/or carbamide peroxide.

RESULTS

Database search for color change of RBC after bleaching retrieved 1335 eligible papers after removing duplicates. After initial screening, 66 articles were assessed for full-text reading with final inclusion of 23 published papers. A meta-regression analysis showed that storage time (p≤0.01), color measuring device (p≤0.01), and background color (p≤0.01) had influenced on color changes of RBC. The bleaching protocol (bleaching agent and time of application) did not influence on color changes of RBC (p>0.01).

CONCLUSIONS

There is evidence that RBC change color after bleaching, but the change is not clinically significant.

Visual and digital tooth shade selection methods, related effective factors and conditions, and their accuracy and precision: A literature review

OBJECTIVE

Despite developments of dental shade selection methods, shade selection is still a challenge affecting esthetic outcomes. The purpose of this review was to discuss visual and digital shade taking methods, related effective factors and conditions, and their accuracy and precision to find out the most accurate, precise shade selection method available in dentistry.

OVERVIEW

The key terms of accuracy, background, ceramic, color, colorimeter, color analysis, color science, color measurement, color measuring instrument, color matching, composite resin, dental/tooth shade guide, digital camera, esthetics, imaging, imaging application/program/ software, intraoral scanner, light source, photography, precision, shade, shade matching/ determination/prediction/reproduction/selection, shade taking device, spectrophotometer, spectrophotometry, tooth color measurement, tooth color/shade, and visual perception were used separately and jointly to detect related English-language articles published between January 1, 1985, and January 1, 2021. Electronic/non-electronic searches of Google Scholar/PubMed/Scopus/Web of Science were accomplished. Consequently, 249 articles were considered. Accordingly, the digital methods show higher accuracy and precision compared to the visual methods while requiring to be enhanced regarding accuracy to achieve ideal shade taking results.

CONCLUSIONS

Dental spectrophotometers provide the highest overall accuracy and precision among different shade selection methods while needing clinical setting to control related effective factors/conditions and technological improvement to perform optimally.

CLINICAL SIGNIFICANCE

Different factors can affect the accuracy and precision of tooth shade selection methods and devices. The understanding of these effective factors may lead to a standard shade taking protocol using accurate, precise methods and devices.

Effects of whitening gels on color and surface properties of a microhybrid and nanohybrid composite

The aim of this study was to compare color changes, surface roughness and gloss of a microhybrid and nanohybrid composite whitened in a simulated in-office or at-home procedure using 40% hydrogen peroxide or 16% carbamide peroxide, respectively. CIELab coordinates were measured before, during and after treatment using VITA EasyShade V (VITA) and ∆E₀₀ calculated. Surface roughness was measured using a surface roughness tester (SJ210; Mitutoyo). Gloss was measured using a gloss checker (IG-331; Horiba). At-home whitening resulted in ∆E₀₀ of 1.23±0.49 (microhybrid) and 1.01±0.76 (nanohybrid). In-office exposure resulted in ∆E₀₀ of 0.69±0.38 (microhybrid) and 0.72±0.50 (nanohybrid). There were no significant differences in ∆E₀₀, surface roughness and gloss between whitening protocols (p>0.05). Color changes of a microhybrid and nanohybrid composite following simulated in-office or at-home whitening reached CIEDE2000 50:50% perceptibility but not acceptability threshold. Surface roughness and gloss of the microhybrid and nanohybrid composite were not affected by whitening.

Effect of Daily Usage Time of 4% Hydrogen Peroxide on the Efficacy and Bleaching-induced Tooth Sensitivity: A Single-blind Randomized Clinical Trial

OBJECTIVE

Compare the risk/intensity of tooth sensitivity (TS) and color change of a 30-minute vs. the recommended 120-minute application time of 4% hydrogen peroxide (HP) for at-home bleaching.

METHODS

A single-blind, parallel, randomized clinical trial was conducted with 92 adult patients with caries and restoration-free anterior teeth A2 or darker, randomly allocated to two groups. Bleaching trays containing 4% HP were used for three-weeks. A four-week regimen was also offered to the patients for the 30-min group after the end of the 3-week protocol. The color change was assessed with the Vita Classical (VITA Zahnfabrik, Bad Säckingen, Germany) and Vita Bleachedguide shade guides (VITA Zahnfabrik) and the Vita Easyshade spectrophotometer (VITA Zahnfabrik) at baseline, weekly, and 30 days after the bleaching. The absolute risk and the intensity of TS were assessed daily using the 0-10 visual analogue scale (VAS) and 5-point Numerical Rating Scale (NRS) scale, and patient satisfaction was recorded with a Likert 0-7 scale. Risk of TS (Fisher's test), intensity of TS in NRS scale (Mann-Whitney test), VAS scale (t-test), and a color change (t-test) were compared.

RESULTS

The 30-minute group saw color change of around 1 SGU inferior to the 120-minute group in all-time assessments (p<0.05). After an extra week of bleaching, mean color change was similar (p>0.05). Patient satisfaction was high for both groups (p>0.05).

CONCLUSIONS

A four-week protocol of at-home dental bleaching with 4% HP for 30 minutes/day whitened teeth similarly to the 120 minutes/day protocol, with low intensity of dental sensitivity and high patient satisfaction.

Effects of a reduced in-office bleaching protocol with 37.5% hydrogen peroxide on effectiveness and tooth sensitivity: A double-blind randomized clinical trial

OBJECTIVE

This randomized clinical trial evaluated the effectiveness and tooth sensitivity (TS) of 37.5% hydrogen peroxide (37.5HP) in-office bleaching with reduced protocol.

MATERIALS AND METHODS

Forty participants with shade mean C2 or darker for the six maxillary anterior teeth were randomly allocated into two treatment groups (n = 20): two (37.5HP2) or three (37.5HP3) 8 min applications/clinical session. Three clinical sessions were performed with a 1 week interval. Color evaluations were done with a spectrophotometer at baseline and 1 week post-bleaching. TS was measured during and up to 48 h after bleaching using a five-point numeric rating scale. Color change was evaluated by Student's t-test for independent samples. The absolute risk and intensity of TS were analyzed by Fisher's and Mann-Whitney/Friedman tests (p < 0.05).

RESULT

Both treatment groups resulted in a significant tooth whitening 1 week post-bleaching (p < 0.001). There were no significant differences between 37.5HP2 and 37.5HP3 for ΔE*_ab , ΔE₀₀ and ∆WI_D . Also, there were not differences between groups regarding high absolute risk (p = 1.0) and low intensity of TS at all time assessments (p > 0.7).

CONCLUSIONS

The in-office bleaching with two 37.5% HP applications produced the same whitening degree, risk and intensity of TS to that performed with three gel applications.

CLINICAL SIGNIFICANCE

Clinicians should opt to use a neutral 37.5% HP in-office bleaching gel for two 8 min applications/clinical session because produces the same whitening effectiveness, risk and low intensity of TS as the protocol proposed by manufacturer (three 8 min applications).

Assessment of a novel bleaching agent formula containing 35% hydrogen peroxide and titanium tetrafluoride: an in vitro study

This study developed experimental gels containing titanium tetrafluoride (TiF4) combined with commercial 35% hydrogen peroxide (HP), and evaluated bleaching efficacy and pH of the gels, and mineral content and morphology of enamel submitted to these treatments. In phase-1, different stock gels mixed with TiF4 were combined with HP. In phase-2, the selected gels were tested on enamel/dentin specimens (n=8): HP; HP and Natrosol+TiF4 (HPnT); HP and Natrosol+Chemygel+TiF4 (HPncT); HP and Aristoflex+TiF4 (HPaT). Bleaching was performed in four sessions (3x15min-application/session). Color (CIEL*a*b*) and whiteness index (WID) were measured after each session, whereas whiteness index differences (ΔWID), color alteration (CIELab-ΔE, CIEDE2000-ΔE00), enamel morphology and pH, at end of bleaching therapy. The change in Knoop microhardness (ΔKHN) was compared before and after bleaching. Data were analyzed by two-way repeated measures ANOVA and Bonferroni (CIEL*, a*, b*), one-way ANOVA and Tukey (ΔWID, ΔE, ΔE00), and LSD (ΔKHN) tests (α=5%). SEM and pH measurements were submitted to descriptive analysis. No differences were observed in lightness (L*) or WID among the groups (p > 0.05), but HP exhibited lower b* values (p<0.05), higher ΔWID than HPnT, and the highest ΔE among the groups (p < 0.05). No differences in ΔE00 were observed between HP and HPncT (p > 0.05), and HPncT showed higher ΔKHN than HP (p < 0.05). HP presented pH values closer to neutral (6.9), whereas experimental agents showed acidic pH values (2.3-3.9). No morphological changes were observed in HP or HPncT groups. HPncT was able to bleach the enamel and maintain enamel microhardness and surface integrity, even at low pH.

Impact of short-term dental dehydration on in-vivo dental color and whiteness

OBJECTIVE

To determine in-vivo chromatic and whiteness changes produced by short-term dental dehydration.

METHODS

Spectral reflectance of 452 upper incisors (226 centrals and 226 laterals) of 113 participants were measured using a spectroradiometer at baseline and after short-term dehydration (minutes 2, 4, 6, 8 and 10). CIE L*a*b* color coordinates (L*, a*, b*, C*_ab and h_ab) and whiteness index for dentistry (WI_D) were calculated. Color differences (ΔE₀₀, ΔE_ab^*) and whiteness differences (ΔWI_D) were computed and interpreted based on their respective 50:50% perceptibility (PT) and acceptability thresholds (AT). Statistical analysis was performed using the related samples Wilcoxon signed-rank test.

RESULTS

L* showed an increasing trend with dehydration, while a*, b*, C*_ab and h_ab have a decreasing tendency. All chromatic coordinates showed statistically significant differences (p < 0.003) at each interval of dehydration compared with baseline, except a* for all teeth. For ΔE₀₀ and ΔE_ab^* values were higher than PT after 2 min of teeth dehydration and higher than AT after 6 and 8 min, respectively. The percentage of teeth exceeding corresponding PT was higher than 50% after 2 min. WI_D index increased with dehydration time, while whiteness differences were clinically perceptible after 4 min. Statistically significant differences were found for WI_D between all dehydration intervals (except 8-10 min). The percentage of teeth exceeding whiteness PT was higher than 50% after 6 min of teeth dehydration.

CONCLUSIONS

Short-term dental dehydration produces clinically unacceptable changes in tooth color and clinically perceptible increase in tooth whiteness level.

CLINICAL SIGNIFICANCE

Clinical shade matching must be done within the first two minutes of any clinical procedure that requires precise chromatic determination but implies a risk of tooth dehydration.

Effects of Artificial Staining and Bleaching Protocols on the Surface Roughness, Color, and Whiteness Changes of an Aged Nanofilled Composite

This study evaluated the surface roughness and color alteration of an aged nanofilled composite exposed to different staining solutions and bleaching agents. Ninety nanofilled composite (Filtek Z350XT, 3M/Oral Care) specimens were submitted to 5,000 thermal cycles and immersed in (n = 30): red wine, coffee, and artificial saliva at 37°C for 48 h. Groups were subdivided according to the bleaching protocol (n = 10) with 20% carbamide peroxide, 38% hydrogen peroxide, or without bleaching - control. Mean surface roughness values (Ra - μm) and color parameters (L*, a*, b*) were measured at baseline (T0), after thermal cycling aging and staining (TS), and after bleaching (TB). Color (ΔE00) and whiteness index (ΔWID) changes were determined after aging and staining (Ts-T0) and after bleaching (TB-TS). The adopted perceptibility and acceptability thresholds of the nanofilled composite were 0.81 and 1.71 ΔE00 units and 0.61 and 2.90 ΔWID units, respectively. Ra was analyzed using mixed models for repeated measurements and L* by the Tukey-Kramer test. The a* and b* values were evaluated by generalized linear models for repeated measures. ΔE00 was tested using two-way ANOVA and Tukey tests, and ΔWID by Kruskal-Wallis and Dunn tests (α = 5%). Ra of all groups decreased after aging and staining (TS, p &lt; 0.05), but increased after bleaching only for groups stained with red wine (TB). Aging and staining decreased the luminosity of the composites, but L* increased after bleaching (p &lt; 0.05). Aging and staining increased a* and b* values, but after bleaching, b* values decreased (p &lt; 0.05). After bleaching, ΔE00 and ΔWID were greater in stained groups at both time intervals, regardless of the bleaching protocol. Stained resin composites exhibited perceptible but unacceptable color (ΔE00 &gt; 1.71) and whiteness (ΔWID &gt; 2.90) changes, regardless of the bleaching treatment performed. Therefore, red wine affected the surface roughness of the aged nanofilled resin submitted to bleaching. Bleaching was unable to reverse the color changes promoted by red wine and coffee on the aged nanofilled composite.

Analysis of enamel structure and mineral density after different bleaching protocols using micro-computed tomography

OBJECTIVE

This study aims to investigate the effect of three different bleaching applications on structural integrity, mineral volume (MV) and density of the enamel by using micro-computed tomography (Micro-CT) and evaluate the colour effectiveness using CIEDE2000.

MATERIALS AND METHODS

Twenty-four maxillary premolar teeth were divided into three groups (n = 8) (group 1: 40% HP gel with erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser activation; group 2: 40% HP gel with diode laser activation; group 3: 16% CP gel). Bleaching protocols were applied and colour alteration was obtained. Data were calculated with CIEDE2000 before and after bleaching. A Micro-CT was used to scan the specimens before and after the bleaching application. Statistical analysis was performed by ANOVA.

RESULTS

No significant difference was observed between the groups for colour changes (p > .05). Micro-CT analysis showed significant differences in structural thickness, structural separation, mineral density and MV for the different ROIs before and after bleaching for all groups (p<.05).

CONCLUSIONS

All of the bleaching methods represented similar efficiency. However, bleaching with Er,Cr:YSGG laser was less harmful to enamel in comparison with other bleaching methods. The present results may be useful for establishing a numerical standard for the change in bleaching with laser systems in dental hard tissues.

Efficacy of whitening toothpaste containing blue covarine: A double-blind controlled randomized clinical trial

OBJECTIVE

This randomized clinical trial evaluated the efficacy and safety of a blue-covarine whitening toothpaste on tooth bleaching.

SUBJECTS AND METHODS

Seventy-five subjects with shade mean C1 or darker were randomized into three groups (n = 25): CT-conventional toothpaste, WT-whitening toothpaste, and CP10-10% carbamide peroxide. Subjects from CT and WT brushed their teeth twice/day for 2 weeks. CP10 used bleaching gel for 4 hours/night for 2 weeks. Tooth shade and CIELab parameters were measured at baseline, after the first application, 2- and 4-week. ΔE*_ab and ΔE₀₀ were calculated. Subjects' perception about tooth color appearance, tooth sensitivity (TS), and gingival irritation (GI) were also assessed.

RESULTS

At all evaluation periods, it was not observed differences between WT and CT considering tooth shade (P > 0.7) or CIELab parameters (P > 0.3). At 2- and 4-week, ΔE*_ab and ΔE₀₀ were higher for CP10 than WT or CT (P = 0.001). WT and CT reported major dissatisfaction with tooth color appearance than CP10 (P = 0.001). At 1- and 2-week, WT experienced GI and TS similar to CT, both lower than CP10 (P < 0.01).

CONCLUSION

There were no significant differences in the whitening efficacy between whitening and conventional toothpastes. Neither of the dentifrices was as effective as at-home bleaching.

CLINICAL SIGNIFICANCE

The silica-based toothpaste containing blue covarine evaluated in this study did not give significant tooth whitening benefits over 2 weeks of use.

Influence of bleaching agents on the color change and translucency of resin matrix ceramics

OBJECTIVE

The aim of this study was to investigate the color change, translucency, and whiteness index of three different resin matrix ceramics and a resin composite subjected to different bleaching agents.

MATERIALS AND METHODS

Twenty disc-shaped specimens (A2 shaded) for three different resin matrix ceramic brands (Groups Ena, Ulti, and Cera) (totally 60) were prepared using the CAD/CAM technique and 20 nanofiller composite specimens (Group Comp) (A2 shaded) with the same dimensions were prepared as the control group. The color change (∆E₀₀ ), relative translucency parameter (RTP), and whiteness index (WI_D ) of the specimens initial and after different bleaching procedures (home-bleaching and office-bleaching) were calculated using ∆E₀₀ , TP₀₀ , and WI_D formulas. Two-way analysis of variance (ANOVA) and multiple comparison test with Bonferroni correction (α = .05) at the significance level of P < .05 were performed for the comparisons of ∆E₀₀ values. The RTP and WI_D values were evaluated by using repeated measures ANOVA and multiple-comparison test with Bonferroni corrections (α = .05) at the significance level of P < .05.

RESULTS

Bleaching procedure and material type were found to be significant regardless of bleaching type for RTP and WI_D values. Material type has a significant effect on the ∆E₀₀ values. The highest color change values were determined in Group Comp (P < .05).

CONCLUSIONS

Bleaching procedures significantly affected the RTP values of Groups Ulti and Cera (P < .05). ∆E₀₀ values for the resin matrix ceramics after the bleaching procedures were below the clinically acceptable values, regardless of the bleaching agent.

CLINICAL SIGNIFICANCE

Optically, materials such as resin matrix ceramics have properties different from not only enamel and dentin but also among themselves. The possible effect of bleaching agents on these materials should be considered carefully while choosing the restorative material.

A Pilot Study About the Effect of Laser-Induced Fluorescence on Color and Translucency of Human Enamel During Tooth Bleaching

Objective: To probe into the effect of laser-induced fluorescence (LIF) on color and translucency of human enamel during tooth bleaching. Materials and methods: Twenty enamel slabs were randomly assigned to be whitened by acidic 30% hydrogen peroxide (HP), neutral 30% HP, alkaline 30% HP, and distilled water, respectively, monitored by a colorimeter and Raman spectrometer simultaneously. Afterward, the parameter differences of color, translucency, Raman relative intensity, and LIF intensity between baseline and post-treatment of each bleaching cycle were calculated. Results: The results demonstrated that the three bleaching groups resulted in increasingly prominent whitening outcome over time compared with control group, and no statistical difference was detected between them. Accordingly, the bleaching groups also engendered a same decrease tendency in fluorescence intensity (FI). However, less demineralization effect occurred on the enamel surface in neutral HP group. The correlation analysis further excluded the effect of demineralization on all the optical parameters (p > 0.05). Besides, various degrees of dependency were detected between FI and translucency parameter (TP), masking effect (ME), C*ab, W*, b*. In addition, ΔFI was associated with parameters of ΔC*ab, ΔW*, Δb*, ΔE, Δa*, and ΔME. ΔFI% was correlated with ΔC*ab, Δb*, ΔW*, and ΔE values. Conclusions: Thirty percent HP with different pH values could result in same variation tendency of enamel color, translucency, and FI. Plus, FI showed a strong association with enamel color and translucency alteration, which is promising for future application as a nondestructive testing method to evaluate bleaching effect and might be a novel way to investigate tooth bleaching mechanism.