Color adjustment potential of resin composites: Optical illusion or physical reality, a comprehensive overview

Influence of preheating and water storage on the color, whiteness, and translucency of modern resin-based composites

OBJECTIVES

To evaluate the influence of preheating and water storage on color, whiteness, and translucency of one-shaded, group-shaded, and multi-shaded resin-based composites.

MATERIALS AND METHODS

A total of 270 samples were fabricated from one-shaded (Omnichroma), group-shaded (Optishade MD), and multi-shaded (Enamel Plus HRI) resin-based composites and divided into six groups: no heating (control) and 1-5 heatings (test) (n = 15). The CIE L*, a*, b*, C*, and h° color coordinates were registered over white, black, and gray backgrounds with a spectrophotometer before and after 24, 72, 144 h water storage. Kruskal-Wallis test was used to evaluate differences in the color coordinates, whiteness index, and translucency parameter (α = 0.05). The Mann-Whitney U test was performed with a Bonferroni correction (p < 0.001) for pairwise comparisons. CIEDE2000 color, whiteness, and translucency differences between groups and subgroups were evaluated using their respective 50%:50% perceptibility and acceptability thresholds.

RESULTS

Preheating influenced color coordinates, whiteness index, and relative translucency parameters (p < 0.001). Although color differences were below the acceptability threshold for all materials, translucency differences were above the acceptability threshold for Omnichroma. Water storage significantly influenced the whiteness index of Optishade MD (p < 0.001).

CONCLUSIONS

Preheating had a more considerable effect on the color, whiteness, and translucency of one-shaded resin-based composite, while water storage influenced group-shaded resin-based composite more importantly.

CLINICAL SIGNIFICANCE

Preheating influences the color, whiteness level, and translucency of the resin-based composites, but the variations remain generally clinically acceptable; however, practitioners should be aware that the modifications in translucency for one-shaded resin-based composites could be more important than for group-shaded and multi-shaded resin-based composites.

Visual evaluation of the color adjustment of single-shade and group shade resin composites in restorations with different cavity configurations

OBJECTIVE

To evaluate the influence of the tooth shade, type of resin composite and cavity configuration on the color adjustment of single-shade and group shade resin composites.

METHODS

Class I and V cavities were prepared in artificial acrylic mandibular right molars with different shades - A1, A2, A3, A3.5 and A4. Three single-shade (OMN, UNI, CHA) and two group shade (FIL, HAR) resin composites were evaluated. Seventy-five observers, including dentists, dental students and laypersons (n = 25), participated in the study. A psychophysical experiment based on visual assessments of the color matching between each tooth and each restoration was ranked from 0 (excellent match) to 4 (huge mismatch), and mean frequencies (%) were calculated. Visual color differences among composite materials and tooth shades were statistically tested (P < 0.05).

RESULTS

The results showed highest percentages of unacceptable color mismatches for class V compared to class I restorations, especially for more chromatic tooth shades (A3.5 and A4). The percentage of ratings of acceptability was higher for laypersons group. For class V, OMN presented significant difference only from UNI in tooth shades A1, A2, A3 and A4. However, for class I, OMN presented significant differences with CHA for A1, A2 and A4, and with HAR and FIL for A1.

CONCLUSIONS

Class I resin composite restorations exhibit superior color matching than Class V, with lighter and low chroma tooth shades demonstrating better color adjustment. The color matching of both cavity configurations is comparable for single and group shade resin composites.

CLINICAL SIGNIFICANCE

Cavity configuration and tooth shade may impact color matching of single and group shade resin composites. This study demonstrates superior color matching in class I configurations over class V for both single and group shade resin composites. Additionally, restorations placed in teeth with lighter shades exhibit more favorable color adjustment.

Exploring the optical behavior and relative translucency parameter of CAD-CAM resin-based composites, polymer-infiltrated ceramic network, and feldspar porcelain

OBJECTIVES

To evaluate and compare the optical properties and relative translucency parameter of CAD-CAM restorative materials.

METHODS

Four CAD-CAM materials were evaluated: Lava Ultimate (LU), Grandio Blocs (GB), VITA Enamic (VE), and VITA Mark II (VM). Disk-shaped samples in shade A2-HT were prepared (n = 10) and polished to 1.00 ± 0.01 mm of thickness. Scattering (S), absorption (K), albedo (a) coefficient, transmittance (T%), light reflectivity (RI), infinite optical thickness (X∞), and radiative transfer coefficients (μa, and μ'S) were calculated using Kubelka-Munk method and Thennadil's semi-empirical approach. Root Mean Square Error (RMSE) and Goodness of Fit (GFC) were used as performance optical behavior. Translucency differences were evaluated using the relative translucency parameter (RTP00) and 50:50 % translucency perceptibility and acceptability thresholds (TPT00 and TAT00).

RESULTS

The spectral distribution of S, K, T%, RI, and X∞ was wavelength-dependent. GFC and RMSE values indicated good spectral behavior matches and good comparative spectral values for RI in LU-GB, LU-VE, and GB-VE, and for K in VE-VM. VM displayed the highest scattering values across the wavelengths, while VE and VM showed lower absorption at shorter wavelengths. LU and GB had the highest transmittance. The X∞ values indicated that all 1.0 mm thick materials could be influenced by the background. No good spectral match and no good comparative spectral values were found between CAD-CAM materials and anterior bovine maxillary specimens. VM had the lowest RTP00 values with perceptible and unacceptable differences compared to CAD-CAM materials evaluated.

SIGNIFICANCE

Understanding the optical behavior of different CAD-CAM materials was essential for guiding clinicians in material selection and optimizing their clinical performance. The findings confirm that the different compositions and microstructure impact the optical properties and translucency of CAD-CAM restorative materials.

Color Stability Assessment of Single- and Multi-Shade Composites Following Immersion in Staining Food Substances

Composite resins are the material of choice for direct restorations, and their success depends mainly on their color stability, since discoloration causes color mismatch, and consequent patient dissatisfaction. A single- and a multi-shade resin were compared in order to evaluate their pigmentation after immersion in staining substances and to investigate the effect of the polymerization time on their color stability. Two-hundred-and-forty composite specimens were created, half made of a single-shade (Group ONE, n = 120) and half of a multi-shade composite (Group OXP, n = 120). Each group was further divided into ONE30 (n = 60) and OXP30 (n = 60), polymerized for 30″, and ONE80 (n = 60) and OXP80 (n = 60), polymerized for 80″. Randomly, the specimens were immersed in turmeric solution, soy sauce, energy drink, or artificial saliva. By means of a spectrophotometer, ΔE00 and WId were calculated at 24 h (T0), at 7 (T1), and 30 (T2) days. Single-shade composites showed statistically significant differences in color change from the turmeric solution, energy drink, and soy sauce than the multi-shade composites (p < 0.005), showing a higher discoloration potential. The polymerization time did not have significative effects on color stability. Single-shade composites showed more color change than multi-shade systems after immersion in staining substances, and the curing time did not influence color variations.

Dental Color-Matching Ability: Comparison between Visual Determination and Technology

BACKGROUND

The choice of the correct color is of paramount importance in esthetic dentistry; however, there is still no consensus on the best technique to determine it. The aim of the present study is to compare the accuracy of a recently introduced colorimeter in shade matching with human vision. In addition, possible variables affecting color-matching by human eye have been analysed.

METHODS

18 disc-shaped composite samples with identical size and shape were produced from a composite flow system (Enamel plus HriHF, Micerium): Nine were considered control samples (UD 0-UD 6), and nine were test samples with identical flow composite shade to the control ones. Parallelly, 70 individuals (dental students and dental field professionals) were individually instructed to sit in a dark room illuminated with D55 light and to perform visual shade matching between control and test discs. An error matrix containing ΔE94 between control and test discs was generated, containing four match-clusters depending on perceptibility and acceptability thresholds. The frequency and severity of errors were examined.

RESULTS

The colorimeter achieved a 100% perfect matching, while individuals only achieved a 78%. A higher occurrence of mismatches was noted for intermediate composite shades without a statistically significant difference. No statistically significant differences were reported for age, sex, and experience. A statistically significant difference was present among the Optishade match and the visual determination.

CONCLUSIONS

The instrumental shade-matching evaluation proved to be significantly more reliable than the human visual system. Further research is needed to determine whether the same outcomes are achieved in a clinical setting directly on patients.

Assessing color mismatch in single-shade composite resins for enamel replacement

STATEMENT OF PROBLEM

Shade selection is a challenge in restorative dentistry. While single-shade composite resins may simplify this process, whether the color mismatch between this composite resin and the substrate is within acceptable levels to ensure successful outcomes is unclear.

PURPOSE

The purpose of this in vitro study was to assess the influence of background and surrounding shade, thickness, and proximity to the surrounding on color mismatch when shaded and single-shade composite resins are used in the center of an enamel layer.

MATERIAL AND METHODS

Two-layer specimens mimicking dentin (the background) and enamel (the surrounding and center) were prepared. Two shades were used for the background and the surrounding layer (OA1/A1 and OA3/A3). At the Ø3-mm center, 2 single-shade composite resins were placed, Omnichroma (OM) and Admira Fusion x-tra (FU), and also shaded composite resins A1, WE, A3, and C2. For the OA1/A1 background and surrounding, shades A1 and WE served as positive controls, while the A3 and C2 were negative controls. For OA3/A3, these controls were reversed. Two enamel layer thicknesses were evaluated (0.5- and 1.0-mm). Reflectance measurements were made at 0.0, 1.0, 2.0, and 2.5 mm from the center. Color differences were calculated between those at 2.5 mm and at other distances (ΔE0, ΔE1, and ΔE2). Data analysis employed a 4-way repeated measure ANOVA with Bonferroni corrections for the pair-wise comparisons (α=.05).

RESULTS

Background and surrounding shade, central shade, distance, and thickness affected color mismatch (P<.05). For the OA1/A1 specimens, single-shade color mismatch values were found between both the positive and negative controls (P<.05). For the OA3/A3 specimens, the color mismatch did not differ significantly from that of negative controls (P>.05). No difference was found between ΔE0 and ΔE1, but each was distinct from ΔE2. Thickness did not affect the color mismatch of the single-shade composite resins (P<.05).

CONCLUSIONS

Single-shade composite resins for enamel replacement showed higher color mismatches compared with positive controls.

The color-matching ability of single-shade universal composites in extracted human teeth

OBJECTIVES

To evaluate the color-match with extracted natural teeth of three single-shade universal composites, a group-shade universal composite, and a highly translucent-shade conventional composite.

METHODS

Twenty extracted human teeth were divided into light- and dark-shade groups (n = 10, LSG and DSG). A preparation was restored with the 3 single-shade universal composites, OMNICHROMA (OMC), Admira Fusion x-tra U (AFU), and Essentia U (ESU); a highly translucent-shade conventional composite, Tetric EvoCeram T (TEC-T); and two shades of a group-shade universal composite-Filtek Universal Restorative (FUR A1 and A4). Composites were photopolymerized, polished, and stored in water for 24 h. The ΔE00 value between the unprepared and restored surfaces was obtained using a spectrophotometer. Composite placement and measurements were repeated three times per tooth. Color differences were statistically analyzed with the within-between-subjects t-test and repeated-measures analysis of variance (ANOVA), followed by post hoc pairwise comparisons with a Bonferroni adjustment (α = 0.05).

RESULTS

There were no statistically significant differences between OMC and FUR (A1 and A4). AFU and ESU showed significantly higher ΔE00 values than OMC and TEC-T (p < 0.05). Single-shade composites exhibited significantly higher ΔE00 values in the DSG than in the LSG except ESU (p < 0.05). None of the composites satisfied the criteria for an acceptable match (ΔE00 >1.8).

CONCLUSION

OMC showed the same color matching ability as a group-shade universal composite. A highly translucent-shade conventional composite and OMC exhibited better color matching ability than other single-shade composites. Overall, single-shade universal composites performed better in lighter-shaded teeth.

CLINICAL SIGNIFICANCE

Single-shade universal composites have the potential to reduce chair time by eliminating shade selection in cavities with lighter-shade teeth. Highly translucent incisal conventional composites also may be used if the appropriate shade of composite is not available.

Instrumental and Visual Evaluation of the Chameleon Effect of Single-shaded Composite Resins

OBJECTIVE

To evaluate the shade-matching ability of single-shade resin-based composite restorations in different thicknesses using both instrumental and visual techniques.

METHODS AND MATERIALS

Cavities with 4 mm diameter and 2 mm (n=96) or 3 mm (n=96) depth were prepared in acrylic incisor teeth of shades A2, A3, B3, and C2 and restored with three single-shade resin composites, Omnichroma (Tokuyama Dental America, Encinitas, CA, USA [OM]), Vittra APS Unique (FGM Dental Group, Joinville, SC, Brazil [VU]), Zenchroma (President Dental, Allershausen, Germany [ZC]), and a microhybrid resin composite (Filtek 3M Z250 3M ESPE, St Paul, MN, USA [FZ]) of A2, A3, B3, and C2 shades. Readings were obtained using VITA Easyshade V spectrophotometer for the teeth and restorations. The CIEDE2000 (ΔE00) color difference formula was used, and the values were assessed using three-way analysis of variance (ANOVA). Forty-eight evaluators graded the shade match of 32 different specimens visually as (A) best shade match, (B) intermediate shade match, and (C) poor shade match.

RESULTS

FZ material achieved satisfactory matches for both thicknesses, across all shades, and OM material demonstrated statistically significant lower shade matches than the ZC and the FZ materials (p<0.05). VU exhibited poor shade match with the highest ΔE00 value on C2 shade. According to the visual examination, the best shade matches were observed for FZ on A3-shade and ZC on C2-shade teeth.

CONCLUSIONS

Shade matching for 2 mm and 3 mm-thick composite resin restorations is material- and tooth-shade dependent.

On color adjustment potential and color blending threshold of dental composite resins

OBJECTIVE

Color Adjustment Potential evaluates the color blending of dental Composite Resins. While Color Adjustment Potential is simple, its clinical relevance is unclear. This research aims to understand it better and to create an index for Composite Resins with meaningful clinical interpretation.

MATERIALS AND METHODS

Single and double shade composite disks of various diameters and opacities were created to test the indices. Color measurements used a dental colorimeter, avoiding subjective assessments. Color Adjustment Potential analysis of each material revealed insights, leading to the creation of a new Color Blending Threshold, providing a clinically relevant numerical value for Composite Resins.

RESULTS

Color Adjustment Potential's numerical significance was clarified and introduced a new index for clinical applications. Color adaptation of each test shade to all Vita shades was also calculated, useful for single-shade restorations in open and closed cavity types.

CONCLUSIONS

The proposed Color Blending Threshold defines the open/closed cavity dimension that can be adequately restored with a single shade of resin composite.

CLINICAL SIGNIFICANCE

Understanding how dental materials adapt to surrounding tooth colors enhances esthetic restorations, simplifies shade matching, and optimizes resin composite production. The proposed Color Blending Threshold is a parameter that directly relates to the clinical significance of a material's true color blending ability. It defines the cavity dimension that can be adequately restored with a single shade of resin composite while ensuring that the resulting color difference falls below a predetermined threshold, meeting the clinical requirements for an esthetic restoration.

Influence of cavity wall thickness on the color adjustment potential of single-shade resin composites

BACKGROUND

The color adjustment potential of resin composites depends on the specific characteristics of the surrounding structures. The authors evaluated the influence of cavity wall thickness on CIEDE2000 color adjustment potential (CAP00) of single-shade composites using the CIEDE2000 color difference (ΔE00) formula.

METHODS

Two types of specimens were produced: single, using Vittra APS color DA3 (FGM Dental), Vittra APS Unique (VU) (FGM Dental), and Omnichroma (Tokuyama Dental) composites; and dual, using Vittra APS color DA3, but with cavity wall thicknesses of 3, 2, or 1 mm, restored with VU or Omnichroma. CIEL∗a∗b∗ color coordinates were obtained from digital photographs of the specimens at different locations, and ΔE00 and CAP00 were calculated. Statistical analysis included 2-way analysis of variance, Kruskal-Wallis, Holm-Sidak, Student-Newman-Keuls, Wilcoxon signed rank, and paired t tests (α = 5%).

RESULTS

Cavity walls 1-mm-thick had higher ΔE00 values and lower CAP00 values, particularly for VU (P < .05). Restorations matched better with the control at the periphery than the central area (P < .001). Overall ΔE00 means exceeded the color perceptibility threshold (ie, 0.8) and the acceptability threshold (ie, 1.8). Color differences (between center of restoration and control composite) were moderately unacceptable for 3-mm and 2-mm thicknesses and extremely unacceptable for 1-mm thickness. Both composites had a ΔE00 color shift predominately determined by means of the lightness difference. Positive CAP00 values were found for VU and Omnichroma.

CONCLUSIONS

Wall thickness, especially at 1 mm, negatively impacted the color of single- shade composites. This effect was more pronounced for VU, affecting mainly the restoration's central area.

PRACTICAL IMPLICATIONS

Color matching ability depends on the structural and material characteristics, and clinicians should be attentive to these factors when using single-shade resin composites.

Effect of aging and fiber-reinforcement on color stability, translucency, and microhardness of single-shade resin composites versus multi-shade resin composite

OBJECTIVE

The purpose of this study was to evaluate the effect of aging and fiber-reinforcement on the color stability, translucency, and microhardness of single-shade resin composites versus multi-shade resin composite.

MATERIALS AND METHODS

Four resin composites (Filtek Z250, Omnichroma, Vittra APS Unique, Zenchroma) were tested. Three subgroups of specimens were prepared for each of the composites: control, polyethylene fiber-reinforcement, and glass fiber-reinforcement- groups (n = 10/per group). The samples were subjected to aging for 10,000 thermal cycles. Color differences (ΔE00 ) were calculated after aging. Relative translucency parameter (RTP00 ) and microhardness values were calculated before and after aging. A two-way analysis of variance and the generalized linear model was used (p < 0.05).

RESULTS

The lowest and highest ΔE00 values were found for Filtek Z250 (0.6 ± 0.2) and Omnichroma resin composites (1.6 ± 0.4), respectively. The ΔE00 value of the polyethylene fiber-reinforcement group (1.2 ± 0.6) was significantly higher than the ΔE00 value of the glass fiber-reinforcement group (1.0 ± 0.4, p < 0.001). The RTP00 value of the glass fiber-reinforcement group (1.92 ± 0.78) was significantly higher than the RTP00 value of the polyethylene fiber-reinforcement group (1.72 ± 0.77, p < 0.001). The highest microhardness values were found in glass fiber-reinforcement group (76.48 ± 17.07, p < 0.001).

CONCLUSION

Single-shade resin composites were more translucent, had higher color change, and lower hardness than multi-shade resin composite. For relative translucency and microhardness, statistical significance was found in the material and fiber type interaction. The glass fiber-reinforcement provided higher translucency, lower color change and higher microhardness values than polyethylene fiber-reinforcement group after aging. Thermocycling had a significant impact on the color stability, translucency parameter, and microhardness of the tested resin composite materials.

CLINICAL SIGNIFICANCE

Single-shade resin composite materials have greater color-changing potential. The glass fiber-reinforcement optimize resin material mechanical properties and color stability more than polyethylene fiber-reinforcement.

In Vitro Comparison of Optical Properties Between Single-Shade and Conventional Composite Resin Restorations

INTRODUCTION

The recently developed single-shade composite resin (using the concept of structural coloring) is a promising option to eliminate the process and subjectivity of shade selection. However, current evidence of its performance is still insufficient. This study aimed to evaluate the color matching, color stability, and refractive index (RI) of single-shade restorations compared with conventional composite resin.

METHODS

This in vitro study was conducted on 48 extracted maxillary premolars. The teeth were sorted into three tooth shade groups (B2, A3, and A3.5). Each group included two subgroups based on the materials used: Omnichroma (OM; Tokuyama Dental, Tokyo, Japan) and Filtek Z350 (FT; 3M ESPE, St. Paul, MN, USA). Buccal and lingual Class V round cavities were prepared and restored according to the randomly assigned subgroups, with the test single-shade material (OM) on one surface and the matching conventional control material (FT) of the proper shade on the other surface of each tooth. Color matching was evaluated by visual assessment and a spectrophotometer. All specimens were distributed into four staining groups and immersed in various staining beverages (black coffee, Arabic coffee, Coca-Cola, and distilled water) for four weeks. Color changes were assessed using a spectrophotometer. Four groups of disc-shaped specimens (single-shade, B2, A3, and A3.5) were fabricated to evaluate the RI using a refractometer. Statistical analyses were performed to compare the materials.

RESULTS

The mean value of the color difference (ΔE) of single-shade restorations was significantly higher than that of paired conventional restorations in all shade groups. The highest mean ΔE was in subgroup A3.5-OM (8.84 ± 2.39) and showed significantly less color matching than other OM subgroups (p=0.009). The visual assessment showed comparable and acceptable color matching in all subgroups except A3.5-OM (p=0.006). There was a significant color change after the staining test within and across staining groups, but the color change was comparable between the OM and FT subgroups. The RI of single-shade material was significantly higher than conventional material (p<0.05).

CONCLUSION

The color matching of single-shade restorations was affected by tooth shade. Its color stability was influenced by various staining substances but was similar to conventional restorations.

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.

Mechanical and Optical Characterization of Single-shade Resin Composites Used in Posterior Teeth

OBJECTIVES

This study aimed to evaluate the optical and mechanical performance of two single-shade resin-based composites (RBCs) compared to those of a conventional RBC for restoring posterior teeth.

METHODS

Two single-shade RBCs, Omnichroma (Tukoyama) and Vittra Unique APS (FGM), and a conventional RBC, Filtek Z350XT shade A2 (3M Oral Care), were evaluated in this study. The optical shade-matching performance was measured using a spectrophotometer. The light emitted by VALO Grand (Ultradent) and transmitted through the 2.0-mm RBC specimens was evaluated using beam profiling. Knoop hardness (KH, N/mm2), degree of conversion (DC, %) at the top and bottom, flexural strength (FS, MPa), elastic modulus (E, GPa), postgel shrinkage (Shr, %), and shrinkage stress (MPa) were evaluated. Scanning electron microscopy (SEM) was used to characterize the filler. Data for FS, E, and Shr were analyzed by one-way analysis of variance (ANOVA) and KH and DC by repeated one-way ANOVA measurement followed by Tukey test (α=0.05). The modified von Mises stress values, light transmission, and SEM images were analyzed qualitatively.

RESULTS

All single-shade RBCs exhibited higher chromatic adaptation than the Filtek Z350XT (p<0.001). Omnichroma exhibited less color difference than Vittra Unique APS, irrespective of the shade. The light transmitted through Omnichroma and Vittra Unique APS increased during polymerization. KH and DC values were significantly reduced from the top to the bottom of the specimens for all RBCs (p<0.001); however, the ratio values were always higher than 80%. In general, all RBCs demonstrated similar mechanical properties. All RBCs exhibited a similar FS (p=0.083) and Shr value (p=0.144). Filtek Z350XT exhibited significantly higher E (p<0.001) than both single-shade RBCs. All RBCs exhibited similar shrinkage stress during restoration and similar residual stress during occlusal loading.

CONCLUSIONS

Single-shade Omnichroma and Vittra Unique APS increased light transmission during light-activation, demonstrating better chromatic adaptation than conventional Filtek Z350XT. In general, Omnichroma and Vittra Unique APS exhibited similar mechanical properties and shrinkage stress distributions as Filtek Z350XT during light-activation and occlusal loading.

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.

Effects of background color and restoration depth on color adjustment potential of a new single-shade resin composite versus multi-shade resin composites

The objectives of this study was to evaluate the effects of background color and restoration depth on color adjustment potential of a new single-shade resin composite versus multi-shade resin composites. Two multi-shade resin composites (Spectrum TPH3 and Clearfil AP-X) marked A2 shade and a new single-shade resin composite (Charisma Diamond One) were tested. Four base shades (A1, A2, A3, and A3.5) of the same resin composite (Filtek Z250) were selected as different background colors. Dual specimens with 1-, 2-, and 3-mm restoration depth and single specimens of all materials were fabricated. CIE color coordinates were measured using a spectrophotometer, then color differences (∆E00) and translucency parameter (TP00) were calculated using the CIEDE2000 formula. Independent observers performed visual scoring. CAP-I and CAP-V values were calculated according to ΔE00 and visual scoring. The results revealed that CAP-I and CAP-V were significantly affected by resin composite type, background color, and restoration depth. CAP-I and CAP-V decreased as restoration depth increased at the same background color for all materials. Charisma Diamond One had the highest CAP-I and CAP-V values at all background colors and restoration depths, with the highest TP00 value. These findings demonstrated that color adjustment potential was dependent on resin composite type, background color, and restoration depth, so shade selection is indispensable for multi-shade resin composites. Charisma Diamond One exhibited the highest color adjustment potential and the most pronounced color shifting, contributing to simplifying the process of shade selection and improving the efficiency of clinical work.

The role of interface distance and underlying substrate on the color adjustment potential of single-shade composites

OBJECTIVE

This study assessed how the distance from the composite interface and the underlying chromatic substrate affect the color adjustment potential (CAP) of two single-shade composites.

MATERIALS AND METHODS

Cylinder-shaped specimens were created using Vittra APS Unique (VU), Charisma Diamond One (DO), and a shaded (A3) composite. Some single-shade specimens were surrounded by the A3 composite, forming dual specimens. Color measurements of simple specimens were taken against a gray background using a spectrophotometer. All specimens were positioned at a 45° angle in a viewing booth under illuminant D65, and images were captured with a DSLR camera against gray or A3 backgrounds. Image colors were measured using image processing software and converted to CIELAB coordinates. Color differences (ΔE00 ) between the single-shade composites and the A3 composite were calculated. CAP was determined by comparing data from simple and dual specimens.

RESULTS

No clinically significant differences were observed between color measurements obtained from images and the spectrophotometer. CAP was higher for DO compared to VU and increased as the distance from the composite interface decreased and when specimens were positioned against an A3 background.

CONCLUSION

The color adjustment potential increased with decreased distance from the composite interface and against a chromatic background.

CLINICAL SIGNIFICANCE

Achieving satisfactory color match in restorations using single-shade composites is crucial, and selecting an appropriate underlying substrate is essential. The color adjustment gradually decreases from the restoration margins towards its center.

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.

Instrumental and visual evaluation of the color adjustment potential of a recently introduced single‑shade composite resin versus multishade composite resins

STATEMENT OF PROBLEM

Single-shade composite resins simplify the process of shade selection by providing a narrow range of color but the ability to simulate all shades. However, evidence is limited for the color shifting ability of a newly developed single‑shade composite resin.

PURPOSE

The purpose of this in vitro study was to evaluate the instrumental color adjustment potential (CAP-I) and visual color adjustment potential (CAP-V) of a recently introduced single-shade composite resin compared with conventional multishade composite resins against different background colors.

MATERIAL AND METHODS

Four multishade composite resins (Spectrum TPH3, Beautifil II, Clearfil AP-X, and Gradia Direct) and a single-shade composite resin (Charisma Diamond One) were tested. Four base shades (A1, A2, A3, and A3.5) of the same composite resin (Filtek Z350XT) were selected as different background colors. Dual specimens (an outer base material with an inner hole filled with inner test material) and single specimens of all test and base materials were prepared (n=6 per group). Spectral reflectance values were obtained by using a spectroradiometer. The color difference (ΔE00) and relative translucency parameter (RTP) were calculated by using the CIEDE2000 and RTPCIEDE2000 formula. Visual scoring of color matching was performed by independent observers. The CAP-I and CAP-V values were calculated according to ΔE00 and visual scoring. Analysis of variance (ANOVA) was used for statistical analysis (α=.05).

RESULTS

CAP-I and CAP-V were significantly affected by composite resin type, background color, and their interaction (P<.001). Positive CAP-I and CAP-V values were found for the majority of test materials. Charisma Diamond One exhibited the highest CAP-I value under all background colors, the highest CAP-V value under most background colors, and the significantly highest RTP value (P<.001).

CONCLUSIONS

The color adjustment potential was dependent on the material type and background color. Charisma Diamond One exhibited the highest color adjustment potential and the most pronounced color shifting ability.

Effect of bleaching on the color match of single-shade resin composites

PURPOSE

To evaluate the color match of single-shade resin composites before and after bleaching procedures, through instrumental and visual analyses.

METHODS

Class V cavities were created on the buccal surfaces of 80 extracted human molars, restored with 4 single-shade composites (Omnichroma; Clearfil Majesty ES-2 Universal; Essentia Universal; Venus Diamond One). A spectrophotometer (VITA Easyshade V) was used to evaluate the tooth/resin color match before (T0), and 24 h (T1) and one week (T2) after dental bleaching (Opalescence Boost PF 40%). Color variations (ΔE00) were calculated and statistically analyzed (P < 0.05). Visual analysis was performed before and after tooth bleaching.

RESULTS

Spectrophotometric evaluations revealed statistically significant differences between materials at T0, T1, and T2 (P < 0.05). Visual analysis reported excellent and very good grades (0 and 1, respectively), irrespective of the materials and timepoints.

CONCLUSION

Data seem to indicate that single shade composites are able to shift their color when the surrounding tooth undergoes bleaching effects. Single-shade composites seem to achieve a good color match with the surrounding tooth structure, before and after professional bleaching.

Influence of surface roughness of universal shade resin composites on color adjustment potential

This study aimed to determine the influence of surface roughness of the color adjustment potential restoration of universal resin composites. A structural colored resin composite (Omnichroma, OC) and a pigment-employed universal shade resin composite (Beautifil Unishade, BU) were used. Each resin composite was placed in a cavity to determine its ability to match the color of artificial teeth. The surface of the resin composites was polished with #800- or #2000-grit SiC paper before performing color measurements. One-way analysis of variance and Tukey post hoc tests were performed (α=0.05). The color difference (ΔE*ab) ranged from 2.5-3.9 for OC and 1.8-8.7 for BU. OC has a more stable color adjustment than BU. The color adjustment potential of universal resin composites was affected by the surface roughness of the restorations.

Toward esthetically and biomechanically reliable anterior resin composite restorations: Current clinical experiences among dental practitioners in Saudi Arabia

Background: Esthetic anterior composite restorations are very challenging. They constitute a main part of the clinical practice of restoring teeth with resin composites. Distinctive variations in composite material selection and technique of application in anterior teeth exist when compared to the practice of restoring posterior teeth with resin composites. In a continuation of a previous assessment of class II resin composite practice,  a cross-sectional survey study was performed to determine the awareness of general dental practitioners in Saudi Arabia about resin composite restorations in anterior teeth and to provide evidence-based recommendations to improve their practice. Methods: A total of 500 dental practitioners from different provinces in Saudi Arabia were invited to participate in an online questionnaire which comprised four domains and included a total of sixteen questions addressing aspects regarding the selection of resin composites, cavity configuration, etching protocol, light-curing technique, liner application, application of poly-chromatic composite, as well as finishing and polishing procedures. Chi square testing and descriptive statistics were used to analyze the attained data. Results: From 250 respondents, the greatest participation was from the Eastern and Middle provinces of Saudi Arabia. Female dentists participated less than males. There was no general agreement between participants regarding the resin composite material or the employed technique of application in restoring anterior tooth defects. Respondents indicated that discoloration and hypersensitivity were the most common reasons for patient's dissatisfaction with resin composites in anterior teeth. Conclusions: Dental practitioners are highly encouraged to improve their clinical practice of restoring anterior teeth using resin composites with the focus upon continuous education programs, online webinars, and workshops.

Probing the micro- and nanoscopic properties of dental materials using infrared spectroscopy: A proof-of-principle study

The preservation of oral health over a person's lifespan is a key factor for a high quality of life. Sustaining oral health requires high-end dental materials with a plethora of attributes such as durability, non-toxicity and ease of application. The combination of different requirements leads to increasing miniaturization and complexity of the material components such as the composite and adhesives, which makes the precise characterization of the material blend challenging. Here, we demonstrate how modern IR spectroscopy and imaging from the micro- to the nanoscale can provide insights on the chemical composition of the different material sections of a dental filling. We show how the recorded IR-images can be used for a fast and non-destructive porosity determination of the studied adhesive. Furthermore, the nanoscale study allows precise assessment of glass cluster structures and distribution within their characteristic organically modified ceramic (ORMOCER) matrix and an assessment of the interface between the composite and adhesive material. For the study we used a Fourier-Transform-IR (FTIR) microscope and a quantum cascade laser-based IR-microscope (QCL-IR) for the microscale analysis and a scattering-type scanning near-field optical microscopy (s-SNOM) for the nanoscale analysis. The paper ends with an in-depth discussion of the strengths and weaknesses of the different imaging methods to give the reader a clear picture for which scientific question the microscopes are best suited for. STATEMENT OF SIGNIFICANCE: Modern resin-based composites for dental restoration are complex multi-compound materials. In order to improve these high-end materials, it is important to investigate the molecular composition and morphology of the different parts. An emergent method to characterize these materials is infrared spectroscopic imaging, which combines the strength of infrared spectroscopy and an imaging approach known from optical microscopy. In this work, three state of the art methods are compared for investigating a dental filling including FTIR- and quantum cascade laser IR-imaging microscopy for the microscale and scattering-type scanning near-field optical microscopy for the nanoscale.

The Effect of Blocker Application on Color Matching of Different Colored Composite Resin Systems

To evaluate the effect of blocker on color matching of different shaded composite systems on natural teeth, 120 anterior teeth were divided into two groups as light and dark shades (n = 60). Round cavities (7 mm in diameter; 2 mm in depth) were prepared on labial surfaces of the teeth. They were restored using three types of resin composites: multi-shaded (Estelite Sigma Quick, Tokuyama Dental, Japan), single-shaded (Omnichroma, Tokuyama Dental, Japan) and group-shaded (Neo Spectra ST, Dentsply Sirona, Germany) (n = 20). Blocker (Omnichroma) was applied to half of the samples in each group (n = 10). Color matching of the restorations with the surrounding tissues were evaluated either by visual analysis or an instrumental method. The resin composites tested did not yield acceptable results instrumentally. Using blocker with single-shade resin composite on dark-colored teeth yielded a minimal change in color in 2 mm deep cavities in the visual evaluation by dentists. Similarly, applying blocker with group-shaded and multi-shaded resin composite on light-colored teeth caused minimal change in color of 2 mm deep cavities in the visual evaluation by dentists. As the application of blocker had no effect on the color matching of different shaded resin composites in the visual evaluations by all observers, except by dentists, blocker may be used as a dentin shade in 2 mm deep cavities of anterior teeth.

Evaluation of Single-Shade Composite Resin Color Matching on Extracted Human Teeth

Introduction

Universal single-shade composite resins are characterized by a property that enables the creation of restorations that mimic tooth structure to the extent possible with fewer shades of color.

Objectives

This study aimed to instrumentally and visually evaluate the color correspondence of two single-shade composite resins in extracted human teeth multishade composite resins.

Methods

Upper central incisors and upper and/or lower molars with intact buccal surfaces were selected. The study consisted of a control group (n = 20): Z250 XT (3M ESPE) (G1) multishade composite resin in colors A1 to A4, and a test group (n = 20) divided further into two equal groups, consisting of single-shade composite resin Omnichroma (Tokuyama Dental) (G2) and single-shade composite resin Vittra APS Unique from (FGM) (G3). Instrumental evaluation was performed using a spectrophotometer, and visual evaluation was performed by three observers. Descriptive measurements related to the differences in color obtained through instrumental means were analyzed using mean and standard deviation, wherein the means were compared using ANOVA, applying the Bonferroni post hoc test.

Results

A statistically significant difference was observed among the groups (G1, G2, and G3) (ANOVA: p < 0.001). For the visual assessment, regardless of the assessment group, 77.49% of the teeth were within the acceptable color-match classification, with the single-shade resins showing better correspondence than the multishade resins.

Conclusion

Single-shade composite resins showed different color-matching results when compared to multishade resins, both in spectrophotometry and visual evaluations. Clinical Significance. Single-shade composite resins simplify the shade-selection process and are promising materials for use in dental practice.

Instrumental and visual evaluation of the color adjustment potential of different single-shade resin composites to human teeth of various shades

OBJECTIVE

The study aims to evaluate the color adjustment potential (CAP-I, CAP-V) of different single-shade resin composites.

MATERIALS AND METHODS

The shades of 40 human incisors were determined using a spectrophotometer, with the teeth divided into four groups of the same shade (n = 10). The following single-shade resin composites were tested: Omnichroma, Charisma Diamond One, Vittra Unique, and Essentia Universal. The specimens were prepared as "dual" and "single." Standardized cavity preparations (diameter, 7 mm; depth, 2 mm) were prepared in human incisor teeth and then restored for dual specimens. Composite duplicates of human incisors were prepared with resin composites for single specimens (n = 10). The color match of these specimens to that of unrestored human incisors was compared, and the color difference (ΔE*) was calculated. Independent observers conducted a visual evaluation of the specimens and scored them. CAP-I and CAP-V values were determined. A one-way analysis of variance test was used for statistical analysis (p < 0.05).

RESULTS

There was no statistically significant difference between the CAP-V and CAP-I values of the tested single-shade resin composites (p > 0.05). All the materials tested had acceptable color-matching potential.

CONCLUSIONS

In terms of color matching, there were no significant differences between the different tooth shades of all the tested resin composites.

CLINICAL RELEVANCE

Single-shade resin composites have acceptable CAP. The use of single-shade resin composites can reduce in-chair clinical times by minimizing the time spent on shade selection.

Effects of surrounding and underlying shades on the color adjustment potential of a single-shade composite used in a thin layer

Objectives

This study aimed to evaluate the surrounding and underlying shades' effect on the color adjustment potential (CAP) of a single-shade composite used in a thin layer.

Materials and Methods

Cylinder specimens (1.0 mm thick) were built with the Vittra APS Unique composite, surrounded (dual specimens) or not (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens were also built only with the control composites. Each specimen's color was measured against white and black backgrounds or the simple control specimens with a spectrophotometer (CIELAB system). The whiteness index for dentistry (WI_D) and translucency parameters (TP₀₀) were calculated for simple specimens. Differences (ΔE₀₀) in color between the simple/dual specimens and the controls were calculated. The CAP was calculated based on the ratios between data from simple and dual specimens.

Results

The Vittra APS Unique composite showed higher WI_D and TP₀₀ values than the controls. The highest values of ΔE₀₀ were observed among simple specimens. The color measurements of Vittra APS Unique (simple or dual) against the control specimens presented the lowest color differences. Only surrounding the single-shade composite with a shaded composite barely impacted the ΔE₀₀. The highest CAP values were obtained using a shaded composite under simple or dual specimens.

Conclusions

The CAP of Vittra APS Unique was strongly affected by the underlying shade, while surrounding this composite with a shaded one barely affected its color adjustment.

Effect of filler load on structural coloration and color adjustment potential of resin composites

The color-matching ability of single-shade composites Omnichroma (OMN) and Omnichroma Flow (OCF) is ensured by structural color, which arises from monodisperse 260 nm spherical fillers. This study evaluated how filler load influences the color adjustment potential of composite restorations to human teeth of various shades. The performance of composites containing the 260 nm spherical fillers -OMN (79 wt%), OCF (71 wt%), and experimental composites R1 (65 wt%), and R2 (60 wt%)- was compared to two conventional A2-shade composites and a transparent composite. Additionally, the translucency parameter, spectral reflectance, and light transmission properties were assessed. Composites with a lower load of the 260 nm spherical fillers exhibited lower light diffusion and lower reflectance in the yellow-to-red range (580-650 nm), which is characteristic for the structural color of OMN and OCF. The best color adjustment was achieved with OCF, presumably due to its high translucency and uniform spectral reflectance.

Does the thickness of universal-shade composites affect the ability to reflect the color of background dentin?

The recently introduced resin composites with a universal shade are claimed to match any tooth color. In this study, it was examined how composite thickness affects the color adjustment of conventional and universal-shade composites to background dentin. Thirty sound human central incisors of various shade were used, and color differences between their intact labial surfaces, exposed dentin surfaces and composite restorations (thickness 1-3 mm) were evaluated. In addition, the translucency, light transmission characteristics, and spectral reflectance of the composites were measured. The results showed that universal-shade composites outperformed conventional composites of A2 shade in the adjustment of hue and chroma (p<0.05) but not in lightness (p>0.05). The color adjustment potential of all composites significantly decreased as their thickness increased (p<0.05). The effect of thickness on Omnichroma and Omnichroma Flow was less marked, presumably because of their higher translucency (p<0.05) and structural coloration which induces light reflectance in the yellow-to-red range.

Background and surrounding colors affect the color blending of a single-shade composite

This study evaluated the background and effect of surrounding colors on the color blending of a single-shade composite used in a thin layer. Disc-shaped specimens (1.0 mm thickness) were built with the Vittra APS Unique composite surrounded (dual specimens) or not surrounded (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens were also built with only control composites. The specimen color was measured against white and black backgrounds with a spectrophotometer (CIELAB system). The whiteness index for dentistry (WID) was calculated for simple specimens. Differences (ΔE00) in color and translucency parameters (ΔTP00) between the simple/dual specimens and the controls were calculated. The translucency adjustment potential (TAP) and color adjustment potential (CAP) were estimated based on the ratios between data from simple and dual specimens. The Vittra APS Unique composite showed higher WID values than the controls. No differences between ΔTP00_SIMPLE and ΔTP00_DUAL were observed for any of the shades. The composite shade did not affect TAP values. The lowest values of ΔE00_SIMPLE and ΔE00_DUAL were observed for shade A1 regardless of the background color. For the white background, ΔE00_SIMPLE values did not differ from those of ΔE00_DUAL for all shades. Only A1 showed ΔE00_DUAL values lower than ΔE00_SIMPLE when the black background was used. The highest modulus of CAP (negative values for the white background) was observed when shade A1 surrounded the Vittra APS Unique composite. The color blending ability of the single-shade resin composite used in a thin layer was affected by both the surrounding shade and background color.

Two‐year retrospective evaluation of monoshade universal composites in direct veneer and diastema closure restorations

OBJECTIVES

The aim of this retrospective evaluation was to assess the short-term outcome of two monoshade universal resin composites with high chameleon effect in anterior direct veneer and diastema closure restorations, and to investigate the possible reasons for failure.

MATERIAL AND METHODS

Patients subjected to veneer and diastema closure restorations with two monoshade universal resin composites (Essentia Universal Shade; EU, GC Corp., and Omnichroma; OC, Tokuyama) operated between January 2018 and March 2019 were selected for the present retrospective evaluation. A total of 159 composite restorations (78 veneers and 81 diastema closure restorations) performed by a single operator in 44 patients (mean age: 33.6) were included in the study. Two blinded and calibrated examiners performed 1- and 2-year assessments of the restorations with respect to FDI criteria, using medical/clinical history and dental photography records. Data were analyzed using Pearson Chi-square with Continuity Correction, Fisher's Exact tests, and Cox regression (a < 0.05).

RESULTS

The cumulative overall survival rates of EU and OC restorations were 94.6% (97.3% for the first year) and 88.6% (95.3% for the first year), respectively, with no significant difference from each other (p = 0.316). The cumulative overall survival rates of direct veneer and diastema closure restoration types were 90.2% (95.1% for the first year) and 92.4% (97.4% for the first year), respectively, with no significant difference (p = 0.559). The reasons for failure were evaluated as fracture of the restoration, failure in esthetic anatomical form, and color mismatch. All the failed direct veneer restorations were due to fractures (FDI score of 5.4), whereas 5 of 6 failed diastema closure restorations were due to color mismatch (FDI score of 3.4). Regarding the composite materials, there were no significant differences between the success rates of the restoration types (p = 0.442 for EU, p = 1.000 for OC). With respect to the restoration types, there were also no significant differences between the success rates of the resin-based composites (p = 1.000 for direct veneer restorations and p = 0.228 for the diastema closure restorations). In addition, no significant difference was observed between male and female patients regarding the acceptable and unacceptable scores (p = 1.000).

CONCLUSIONS

The 2-year clinical performance of the two monoshade universal composites in anterior veneer and diastema closure restorations were both considered successful and similar. Despite the lack of shade selection, both monoshade universal composites presented a successful color match. However, the diastema closure restorations might be more prone to color mismatch compared to the veneers over time, while veneer restorations presented more fractures than the diastema closure restorations.

CLINICAL SIGNIFICANCE

Monoshade universal composites presented successful short-term clinical outcomes regarding both function and esthetics in anterior direct veneer and diastema closure restorations.

Effect of two artificial aging protocols on color and gloss of single-shade versus multi-shade resin composites

The long-term color stability and gloss retention of resin composites are among the crucial factors that affect the clinical longevity of esthetic restorations, especially in anterior teeth. This study evaluated the effect of artificial aging by immersion in different storage media and thermocycling on color and gloss of dental single-shade resin composite (Omnichroma) versus multi-shade one (Filtek Z350XT). One hundred resin-composite disc-shaped specimens were used, 50 from each group, Omnichroma and Filtek Z350XT. Ten specimens from each material acted as control group (incubated in saliva). For each material, 40 specimens were divided according to the artificial-aging protocol (immersion at 37 °C for 12 days or thermocycling for 10,000 cycles) and storage media (tea, red wine). Color and gloss were measured before and after artificial aging. Color difference (∆E₀₀) was compared with perceptibility threshold and acceptability threshold. Data were statistically analyzed; independent t test was used to compare results between two tested materials, while two-way ANOVA was used to compare results among the different immersion media within the same material. Artificial aging (immersion or thermocycling) in tea and red wine led to significant color changes and gloss reduction in both materials (P < 0.05), in contrast to control group. Red wine produced highest color differences. Both dental resin-composites; the single-shade (Omnichroma) and multi-shade (Filtek Z350XT) displayed unacceptable discoloration and gloss reduction after artificial-aging in tea and red-wine by immersion or thermocycling simulating one-year clinical-service.

Effect of surrounded shade and specimen`s thickness on color adjustment potential of a single-shade composite

Abstract This study evaluated the effect of surrounded shade and specimens` thickness on the color adjustment potential (CAP) of a single-shade composite. The composite Vittra APS Unique was surrounded (dual specimens) or not (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens of the control composite were also confectioned. Opacity and whiteness index for dentistry (WID) were calculated for simple specimens. Color differences between the simple (ΔE*SIMPLE)/ dual specimens (ΔE*DUAL) and the controls were calculated. CAP was calculated based on the ratio between ΔE* SIMPLE and ΔE* DUAL. The tested composite presented lower opacity (53 to 62% vs. 80 to 93%) and higher WID (≈ 42 vs. 18 to 32) than controls. Irrespective of the specimens’ thickness (1.0/ 1.5 mm), the lowest values of ΔE* SIMPLE (11.1/ 10.8) and ΔE*DUAL (7.2/ 6.1) were observed using the surrounding shade A1. The shade A3 yielded higher ΔE*SIMPLE (16.4/ 17.1) and ΔE* DUAL (11.3/ 12.3) than the A2 (ΔE*SIMPLE = 13.4/ 14.6; and ΔE* DUAL = 9.7/ 10.3). The specimen`s thickness significantly affected the CAP (0.35 and 0.44 for 1.0 and 1.5 mm, respectively) only for shade A1, which had the highest CAP values. The shade A3 resulted in higher CAP values (0.31) than A2 (0.27) when 1.0-mm thick specimens were used, but similar values were observed for 1.5 thick specimens (≈ 0.29). In conclusion, both surrounding shade and specimen thickness can affect the CAP of a single-shade resin composite.

Color stability and surface roughness of ormocer- versus methacrylate-based single shade composite in anterior restoration

Background

The blending ability of universal shade composites and their stability in the oral environment are of great concern in restoring anterior teeth. This study aims to evaluate and compare the color stability and surface roughness of two single-shade composite restorations, ormocer-based composite (OBC) and methacrylate resin-based composite (RBC), after storing them in different staining media.

Materials and methods

In this study, two universal shade composite restorative materials were tested: a nanohybrid OBC (Admira fusion X-tra, Voco) and a supra-nanofilled RBC (Omnichroma, Toukyama). In total, 60 cylindrical centralized cavities (diameter: 5 mm, depth: 2 mm) were prepared in sound extracted-human central incisors and divided into two equal groups according to the restorative material used (n = 30). According to the storage media, the teeth of each group were divided into three subgroups (n = 10): artificial saliva, black tea, and cola. The restoration color was evaluated for all teeth at baseline and after four weeks of storage. The color stability (∆E) was measured using a reflective spectrophotometer (X-Rite, model RM200QC, Neu-Isenburg, Germany). The surface roughness (Ra) was evaluated using three-dimensional optical profilometry (Wyko, Model NT 1100, Veeco, Tucson, USA). Additionally, the extracted data were analyzed using two-way analysis of variance (ANOVA), one-way ANOVA and Student’s t-test.

Results

In the baseline evaluation, there were no statistically significant differences with respect to color matching or surface roughness results between the two studied restorative materials. However, the differences were statistically significant after storing them in different media.

Conclusion

Universal composites showed satisfactory color matching with different teeth colors and accepted surface smoothness, whereas the aging procedure exerted a negative effect on their color stability and surface characteristics.

Simulation of Automatic Color Adjustment of Landscape Image Based on Color Mapping Algorithm

With the continuous development and progress of image sensing technology in recent years, the problem of image data acquisition, recovery, and recording has been solved, and people have gradually realized that image data can be better recovered, recorded, and exhibited by collecting image data. It is also used in target recognition, image display, landscape design, and other fields. And the application of color mapping algorithm can more intuitively affect the final quality of the display image. This is extremely important for landscape design. It can be said that the emergence and application of color mapping algorithm provide strong technical support for both dynamic and static image color automatic adjustment and simulation. On this basis, taking the color mapping algorithm as the breakthrough, through the in-depth introduction of the color mapping algorithm, starting from the direction of landscape image color automatic adjustment, a relatively simplified color mapping algorithm model inheriting the positive and negative two-way vision model is proposed. At the same time, a simulation algorithm based on landscape suitcase color automatic adjustment is proposed based on the color mapping algorithm model. Experiments show that automatic color adjustment of landscape images based on color mapping algorithm can achieve more realistic image reproduction, and the color mapping method based on color mapping algorithm has less illumination bias. When the number of experiments is 30, the difference in visibility of the plane is 0.25 cd/m2, the difference of visibility according to the color change segmented by the gradient area is 0.71 cd/m2, and the difference of the illuminance difference of the transition image is 0.71 cd/m2. Gaussian pyramid is 1.25 cd/m2. The proposed method improves color density by reducing image sharpness and compensating for color sharpness of landscape image, and high quality landscape images provide assistance for landscape design.

Masking Ability of Bleach Shade Composite Resins in Different Thicknesses

Introduction

In recent years, the use of bleach shade composite resins has increased due to the high esthetic demands. The aim of the present study was to investigate the masking ability and translucency of several bleach shade composite resins.

Materials and Methods

In this in vitro study, 180 discs from 9 bleach shade composite resins of 5 brands (G-aenial Anterior, Gradia Direct, Charisma Diamond, Estelite Sigma Quick, and Renamel Microfill) in thicknesses of 0.5, 1, 1.5, and 2 mm were prepared. The color parameters of the specimens were measured in a CIE l ∗ a ∗ b ∗ system using a spectrophotometer. Masking ability and translucency parameters were calculated, and the influence of thickness, shade, and composite resin brand on these variables was analyzed using the Kruskal-Wallis and Mann-Whitney U tests.

Results

Both masking ability and translucency differed significantly among groups (p < 0.001), but only MA was different between different brands (p < 0.001). Higher thicknesses showed lower translucency in all pairwise comparisons (p < 0.001). 0.5 mm-thick specimens had lower masking ability than 1.5 mm- (p=0.016) and 2 mm- (p=0.035) thick ones. However, masking ability of other thickness pairs did not show a significant difference (p > 0.05). G-aenial Anterior and Renamel Microfill had the highest and lowest masking ability. Bleach white shades had lower masking ability and higher translucency than extrawhite bleach shades.

Conclusion

Translucency and masking ability of bleach shade composite resins differed in different thicknesses, composite resin brands, and shade groups.