Discoloration and translucency changes of CAD-CAM materials after exposure to beverages

Effect of polishing and bleaching on color, whiteness, and translucency of CAD/CAM monolithic materials

OBJECTIVE

To evaluate the effect of polishing and bleaching on the recovery of lightness, color, whiteness, and relative translucency parameter (RTP) in CAD/CAM materials and changes in these properties when another staining in coffee was conducted after the treatments.

MATERIALS AND METHODS

Disks of Lava Ultimate (LU), Vita Enamic (VE), IPS Empress CAD (EMP), IPS e.max CAD (EMAX), and Vita Suprinity (VS) were (1) not treated (control), (2) polished with Proxyt or (3) Ceramisté, (4) bleached with Opalescence PF or (5) Whiteness HP Blue, and (6) air polished with Clinpro Prophy Powder. CIE L*a*b* color coordinates were registered at baseline (R0), after staining with coffee for 30 min daily for 36.5 days and treatment (R1), and after another staining (R2). Differences (R1-R0 and R2-R0) in lightness (ΔL00), color (ΔE00), RTP (ΔRTP00), and whiteness (ΔWID) were evaluated by mixed repeated measures ANOVA and 95% confidence intervals (α = 0.05) and interpreted in function of their respective 50:50% PT and AT thresholds. Topography was evaluated by scanning electron microscopy (SEM).

RESULTS

In LU, Opalescence PF and Proxyt decreasedΔ L 00 R 1 - R 0 $$ {\Delta L}_{00\left({R}_1\hbox{--} {R}_0\right)} $$ ,Δ E 00 R 1 - R 0 $$ {\Delta E}_{00\left({R}_1\hbox{--} {\mathrm{R}}_0\right)} $$ , andΔWI D R 1 - R 0 $$ {\Delta \mathrm{WI}}_{\mathrm{D}\left({R}_1\hbox{--} {R}_0\right)} $$ and showed lowerΔ L 00 R 2 - R 0 $$ {\Delta L}_{00\left({R}_2\hbox{--} {R}_0\right)} $$ ,Δ E 00 R 2 - R 0 $$ {\Delta E}_{00\left({R}_2\hbox{--} {R}_0\right)} $$ , andΔWI D R 2 - R 0 $$ {\Delta \mathrm{WI}}_{\mathrm{D}\left({R}_2\hbox{--} {R}_0\right)} $$ . In VE, all treatments decreasedΔ L 00 R 1 - R 0 $$ {\Delta L}_{00\left({R}_1\hbox{--} {R}_0\right)} $$ ,Δ E 00 R 1 - R 0 $$ {\Delta E}_{00\left({R}_1\hbox{--} {R}_0\right)} $$ , andΔWI D R 1 - R 0 $$ {\Delta \mathrm{WI}}_{\mathrm{D}\left({R}_1\hbox{--} {R}_0\right)} $$ , whereasΔ L 00 R 2 - R 0 $$ {\Delta L}_{00\left({R}_2\hbox{--} {R}_0\right)} $$ ,Δ E 00 R 2 - R 0 $$ {\Delta E}_{00\left({R}_2\hbox{--} {R}_0\right)} $$ , andΔWI D R 2 - R 0 $$ {\Delta \mathrm{WI}}_{\mathrm{D}\left({R}_2\hbox{--} {R}_0\right)} $$ were lower in Opalescence PF than in the control group. In both moments, ΔE00 and ΔWID in EMP (also ΔL00) and EMAX were higher in Opalescence PF than in the control group, from which the other treatments did not differ in R1-R0. In EMP,Δ E 00 R 2 - R 0 $$ {\Delta E}_{00\left({R}_2\hbox{--} {R}_0\right)} $$ in Whiteness HP Blue (alsoΔ L 00 R 2 - R 0 $$ {\Delta L}_{00\left({R}_2\hbox{--} {R}_0\right)} $$ ) and Proxyt were also higher in comparison to the control group and in VS, Ceramisté decreasedΔ L 00 R 1 - R 0 $$ {\Delta L}_{00\left({R}_1\hbox{--} {R}_0\right)} $$ ,Δ E 00 R 1 - R 0 $$ {\Delta E}_{00\left({R}_1\hbox{--} {R}_0\right)} $$ , andΔ R T P 00 R 1 - R 0 $$ \varDelta RT{P}_{00\left({R}_1\hbox{--} {R}_0\right)} $$ , whereas Opalescence PF increasedΔRTP 00 R 1 - R 0 $$ {\Delta \mathrm{RTP}}_{00\left({R}_1\hbox{--} {R}_0\right)} $$ .Δ E 00 R 2 - R 0 $$ {\Delta E}_{00\left({R}_2\hbox{--} {R}_0\right)} $$ of Ceramisté andΔWI D R 2 - R 0 $$ {\Delta \mathrm{WI}}_{\mathrm{D}\left({R}_2\hbox{--} {R}_0\right)} $$ andΔ R T P 00 R 2 - R 0 $$ \varDelta RT{P}_{00\left({R}_2\hbox{--} {R}_0\right)} $$ of Proxyt were lower than those of the control group.

CONCLUSIONS

The most suitable treatment to recover the lightness, color, whiteness, and RTP without changing these properties after another coffee exposure is material-dependent.

CLINICAL SIGNIFICANCE

Although the effectiveness of the treatment was material-dependent, Proxyt was the only treatment that promoted clinically acceptable changes for both LU and VE, while for purely ceramic materials, this condition was observed with Ceramisté and Clinpro Prophy Powder.

Effect of coffee staining and simulated oral hygiene methods on the color and translucency of a nanoceramic resin

OBJECTIVE

Evaluate the color and translucency of a nanoceramic resin subjected to hygiene practices and immersion in coffee over time.

MATERIALS AND METHODS

Specimens (n = 80, HT and LT, 0.5-mm thick) of a nanoceramic resin were obtained and were divided in groups according to the simulated oral hygiene: no intervention (NT), brushing with an electric brush and water (BN), brushing with an electric brush and toothpaste for 10 s (BT), and immersion in mouthwash for 30 s (MW). Oral hygiene practices were repeated after staining in coffee solution for 15, 48, 336, 1440, 8640, and 35,040 min. Spectral wavelengths were recorded with a spectrophotometer at each time. ∆E00, ∆L', ∆C', ∆H', and TP00 were calculated by CIEDE2000 and were evaluated by 2-way ANOVA, repeated measures ANOVA, and Tukey's HSD test (α = 0.05).

RESULTS

ANOVA showed significance among factors for ΔE00 (p < 0.05), with higher ΔE00 for NT-HT (11.7) and NT-LT (11.2). After T6 (2-year simulation), the lowest values were found for BT-HT (5.3) and BT-LT (4.9). All groups showed a reduction in lightness and translucency and increased chroma and hue. However, the smallest variations were found in the BT groups (p < 0.05).

CONCLUSIONS

Brushing with toothpaste effectively minimized the color change of NCRs caused by coffee staining.

CLINICAL SIGNIFICANCE

Oral hygiene practices, such as brushing with toothpaste, might be important to minimize staining of nanoceramic resin restorations, especially in patients who frequently consume coffee.

Effect of coffee thermocycling on the color and translucency of milled and 3D printed definitive restoration materials

STATEMENT OF PROBLEM

Research on the color and translucency properties of 3-dimensionally (3D) printed definitive resins and the effect of coffee thermocycling on these properties is lacking.

PURPOSE

The purpose of this in vitro study was to investigate the effect of coffee thermocycling on the color and translucency parameters of the milled and 3D printed materials used for definitive restorations.

MATERIAL AND METHODS

Plate-shaped specimens (12×12×1 mm) of 3 milled (IPS e.max CAD (LDS), Vita Enamic (PICN), Cerasmart (RNC)) and two 3D printed (VarseoSmile Crownplus (VSP), Permanent Crown (PC)) were fabricated (n=12). The brightness (L*), red-green (a*), and yellow-blue (b*) parameters were measured with a spectrophotometer before and after 10 000 coffee thermocycles. The relative translucency parameters (RTP00) and color change were calculated using the CIEDE2000 formula. Stainability (ΔE00) and translucency differences (ΔRTP00) were evaluated. Data were analyzed with the Kruskal-Wallis, Mann-Whitney U, and Wilcoxon tests. The Spearman correlation test was used to analyze the ΔE00 and ΔRTP00 values (α=.05).

RESULTS

The type of material and coffee thermocycling significantly affected the evaluated parameters at both measurement periods (P=.001). Coffee thermocycling decreased the L* and RTP00 values while increasing the a* and b* values (P=.001). The highest ΔE00 values were found in VSP and PC, which were statistically similar (P=.291), while the highest | ΔRTP00 | values were observed for VSP (P=.001). The lowest ΔE00 and | ΔRTP00 | values were found in LDS (P=.001). A positive relationship was found between the ΔE00 and | ΔRTP00| values (R=.590, P=.01).

CONCLUSIONS

After coffee thermocycling, all tested materials exhibited a darkened, yellowish, and opaque appearance, although the alterations in color and translucency remained within clinically acceptable thresholds (AT00=1.81) for these materials.

Comparison of discoloration of ceramic containing 3D printable material and CAD/CAM blocks

This study aimed to clarify aspects of the color and translucency of 3D printed dental material with CAD/CAM blocks. Three different ceramic-containing, resin-based CAD/CAM blocks and a 3D printable resin were evaluated after thermocycled and assessed for their degree of discoloration based on colorant types and storage times. Data were analyzed using repeated-measures analysis of variance followed by Tukey's post-hoc test. All materials in red wine had ∆E00 values higher than the clinically accepted threshold value. At 1 week and 1 month, the 3D material was statistically significantly more discolored than the other 3 materials (p<0.05). None of the materials exceeded the acceptable threshold value at any time point. The color changes increased over time in resin-based CAD/CAM blocks and 3D printable dental materials. After 1 week and 1 month, there was a statistically significant difference in the color change between the 3D printed material and the CAD/CAM blocks.

Color stability of two different resin matrix ceramics: randomized clinical trial

BACKGROUND

One of the most common causes of aesthetic failure and restoration replacement is the tooth restorations color mismatch specifically after aging.

METHODS

One hundred and two participants with endodontically treated first molar were selected clinically. The patients were randomly splited into two groups and restored either with Cerasmart hybrid ceramic or Vita Enamic polymer infiltrated ceramic network (PICN) crowns and cemented using dual cure adhesive cement. The color difference (ΔE) values after cementation at 0 (Baseline), 6, and 12 months of use were obtained by quantification of L*, a*, and b* values with a digital spectrophotometer. Mann-Whitney test used to compare between tested groups at each time point and between (α = 0.05).

RESULTS

At 6 months follow-up intervals, Vita Enamic group showed the highest significant ∆L* (p = 0.035) and ∆a* (p < 0.001) compared to Cerasmart group. ∆b* and ∆E showed no significant difference between both groups (p > 0.05). Furthermore, all color parameters of both groups showed statistically significant difference at 12 months follow-up intervals. After 12 months, Vita Enamic restorations presented higher color change compared to Cerasmart restorations with a (p-value of 0.0120). When comparing the total color difference ∆Et through-out the follow-up intervals of Vita Enamic & Cerasmart groups, there were insignificant difference (p = 0.263).

CONCLUSION

Both hybrid materials demonstrated comparable color stability after 1 year of clinical service within clinical acceptance range. However, Cerasmart demonstrated a better colour stability after 1 year.

TRIAL REGISTRATION

ClinicalTrials.gov (ID: NCT05501808) 15/8/ 2022- 'retrospectively registered'.

Effect of aging on color, gloss and surface roughness of CAD/CAM composite materials

OBJECTIVES

To assess the effect of aging procedures on color, gloss and surface roughness of CAD/CAM composite materials.

METHODS

6 CAD/CAM composite materials (Brilliant CRIOS, Cerasmart, Lava Ultimate, Tetric CAD, Shofu Block HC, Grandio Blocs) were tested. 10 CAD/CAM fabricated specimens of each material polished according to manufacturers' recommendations, were subjected to one of the following aging procedures; immersion in coffee (30 days, 37^οC), water thermocycling (5000 cycles, 5-55 °C) and photoaging (150,000 kJ/m²). Color, gloss and surface roughness measurements were performed before and after aging and the respective changes were calculated. Kruskal-Wallis tests, paired t-tests, one-way ANOVA and Bonferroni post-hoc tests were used for statistical analysis (a = 0.05).

RESULTS

Color changes ranged from 3.03 to 4.13 after coffee immersion, from 1.33 to 2.55 after thermocycling and from 1.02 to 2.75 after photoaging. No statistically significant differences for ΔE*_ab were found among materials after coffee immersion and thermocycling (p>0.05). Gloss changes ranged from -5.7 to -1.6 GU after coffee immersion, from -2.3 to 0.1 GU after thermocycling and from -4.4 to 0.5 GU after photoaging. No significant differences in gloss changes were found among materials after aging (p>0.05). Tetric CAD demonstrated the significantly lower gloss and the higher surface roughness after polishing. Except for gloss after thermocycling, aging procedures caused significant alteration of gloss and surface roughness parameters from baseline levels.

CONCLUSIONS

Aging procedures caused perceptible but acceptable color changes and small but visible gloss changes, while surface roughness parameters of the tested CAD/CAM composite materials were significantly affected by aging.

CLINICAL SIGNIFICANCE

Aging procedures affected CAD/CAM composite materials indicating that these materials may be prone to color and surface alterations in the oral environment that could compromise the esthetics and the performance of the restorations. Clinical studies are needed to investigate the long-term behavior of the newly introduced CAD/CAM materials.

Color Stability of Polymer-Based Composite CAD/CAM Blocks: A Systematic Review

BACKGROUND

This systematic review aims to evaluate the color stability of resin composite CAD/CAM blocks (CCB) when submitted to staining solutions.

METHODS

A systematic search was performed on different databases (Embase, Medline, Scopus, Web of Science). Search terms were: 'polymer infiltrated', 'polymer-based', 'resin nanoceramic', 'resin ceramic', 'hybrid composite', 'hybrid ceramic', 'composite ceramic', 'resin infiltrated', 'CAD-CAM', 'CAD/CAM', 'color stability', 'staining', 'staining susceptibility', 'color change', 'color difference'.

INCLUSION CRITERIA

in vitro articles published in the English language until 18 September 2022 without initial time restriction evaluating the color stability of CCB when submitted to staining solutions.

EXCLUSION CRITERIA

studies investigating color change induced by smoke or whitening treatments; studies not including a clinical evaluation of the results using the thresholds for color perceptibility and acceptability. Risk of bias assessment using the QUIN tool.

FINDINGS

Out of the 378 initially retrieved articles, 19 were included in this review. They investigated 17 different CCBs and different artificial staining by liquid protocols, including coffee, red wine, tea, and cola. CCBs exceeded clinical acceptability thresholds for color shift in 18 out of 19 studies, with a significantly higher color stability than conventional hybrid resin-based composites (RBCs), and a significantly lower color stability than ceramic materials. The identified differences in CCBs in color stability can be attributed to the material's composition, but also to the heterogeneity of staining procedures. Interpretation and clinical implication: Clinicians should be aware that, although to a lower degree when compared to RBCs used in direct or indirect procedures, CCBs undergo color changes to a higher degree in comparison to ceramic materials.

Physical Properties and Color Stainability by Coffee and Red Wine of Opaque and High Translucency Zirconia Dental Ceramics after Hydrothermal Degradation

The objective was to evaluate the bending strength, phase transformation, roughness, and color stainability by coffee and red wine of opaque and high translucency yttria-stabilized zirconia before and after hydrothermal degradation in saline solution or oral mouthwash. Presintered zirconia blocks with medium opacity (ZrO₂-3 mol. % of Y₂O₃) designed as ZrOp and high translucency zirconia (5.2 mol. % of Y₂O₃) designed as ZrTrans were used. Specimens (n = 80/group) were cut and sintered at 1500°C for 2 h. The specimens were hydrothermally degraded in an autoclave (134°C–1.8 kg/cm²) for 20 h in saline solution (0.5 g/L) and oral mouthwash solution (0.02% sodium fluoride, without alcohol and with 21.6% alcohol). After hydrothermal degradation, the samples were immersed in containers with coffee or red wine for 14 days to determine their color stainability. The results showed that the ZrOp had a higher bending strength than the ZrTrans before and after hydrothermal aging. In ZrOp and ZrTrans, the roughness increased after hydrothermal degradation. ZrOp samples had a higher Ra roughness than the ZrTrans samples. Roughness did not change after immersion in coffee or red wine. The X-ray diffraction (XRD) results showed that ZrOp samples underwent a tetragonal to monoclinic phase transformation, while ZrTrans samples were unchanged. Both ZrOp and ZrTrans samples changed color after immersion in coffee and red wine.

Effect of staining beverages and bleaching on optical properties of a CAD/CAM nanohybrid and nanoceramic restorative material

Background

The purpose of this study was to evaluate the optical properties of nanohybrid Grandio (GR) and nanoceramic Lava Ultimate (LU) CAD/CAM restorative materials subjected to different beverage solutions and subsequently bleached.

Methods

Five groups of each restorative material (n = 20/group, shade A2-high translucent) were immersed in distilled water, coffee, tea, cola, and ginger for one week. Changes in whiteness index, translucency parameter, and color changes of the specimens were evaluated. The data of color measurements after staining, bleaching, and the residual differences were statistically analyzed using Kruskal–Wallis and Mann–Whitney U tests at the significance level of P < 0.05.

Results

LU and GR revealed the highest differences in whiteness index after coffee staining (P < 0.001). GR revealed lower translucency parameter differences after staining with coffee than LU (P = 0.007). There were no significant differences in translucency changes between LU and GR after staining with tea, cola, or ginger (P > 0.05). LU revealed significantly greater color changes than GR after staining (P < 0.001).

Conclusions

LU nanoceramic CAD/CAM restorative material revealed higher color changes than GR nanohybrid material. Staining beverage solutions had a distinct influence on the optical properties of the tested CAD/CAM restorative materials.

Evaluation of color stability and microhardness of contemporary bulk-fill composite resins with different polymerization properties

OBJECTIVES

To determine the color stability and microhardness of three bulk-fill composites with different polymerization characteristics, after immersion in four different solutions.

MATERIALS AND METHODS

Color measurements of three bulk fill (Viscalor (VIS), Tetric PowerFill (TPF), Fill Up! (FUP)) and a microhyrid composite resin (G-aenial posterior [GCP]) were performed after polymerization. The specimens were immersed in coffee, cola, red wine and distilled water. Discolorations were recorded after 24 h (T1), 10 days (T2) and 30 days (T3) of immersion. ΔE (CIEDE2000) values were calculated. Vickers microhardness (VHN) was measured from top and bottom surfaces at T0 and T3. Data was analyzed with Two-way ANOVA, One-way ANOVA and Tukey post hoc tests.

RESULTS

The highest discoloration was seen in wine and the lowest in distilled water and cola. At T3, there was no difference in distilled water groups, while the statistically highest ΔE₀₀ were obtained in TPF and GCP in coffee, cola and wine. VIS groups had the highest VHN values at T0 and T3 in all solutions.

CONCLUSIONS

Samples immersed in coffee and wine showed discoloration beyond clinically acceptable limits. After 30 days, discoloration occurred in all materials immersed in all solutions. At T3, VIS microhardness generally decreased, while TPF did not.

CLINICAL SIGNIFICANCE

After 30 days, all bulk-fill composites immersed in distilled water, coffee and wine showed clinically unacceptable ΔE₀₀ .

Color Stability and Translucency of Polymer-Infiltrated Ceramic-Network Materials—A Systematic Review of the Literature

This systematic review aimed to compile information and report the color stability and translucency of polymer-infiltrated ceramic-network (PICN) materials for suitable clinical applications in dentistry. Original peer-reviewed articles in electronic databases including PubMed, MEDLINE, Scopus, and Web of Science were searched to identify relevant papers published between January 2013 and August 2020. The published papers were only in the English language and limited to in vitro studies, and experimental reports were considered. The data from nine studies were considered when reviewing the color stability and translucency of PICN in comparison to other commonly used restorative materials. Among the included studies, color stability assessment was performed in five studies, and the other four studies were involved in the combined assessment of both color stability and translucency. PICN materials are a comparatively newer class of restorative materials and are recommended to overcome the drawbacks of ceramics and resin composites. The outcomes of previous laboratory studies still do not provide convincing results regarding the optical properties of PICN materials. However, with existing sources and evidence, PICN materials exhibit less color stability than ceramics do but better color stability compared to that of resin nanoceramics (RNC) and resin composites. The translucency of PICN materials is low compared to that of ceramics, nanoceramics, and resin composites.

Effect of Staining and Aging on Translucency Parameter of CAD-CAM Materials

Objectives

To evaluate different intervals of exposure to staining solutions and artificial aging on translucency parameter (TP₀₀) of CAD-CAM materials.

Material and Methods

One millimeter thick square-shaped specimens (N = 288) were cut from Cerasmart (CS), IPS e.max (IE), Lava Ultimate (LU), Shofu HC (SH), Vita Enamic (VE), and Vita Suprinity (VS) and were divided into laboratory and chairside polishing. Reflection wavelength spectra, CIE D65 standard illuminant, 2 ° standard observer, SCI, UV included, SAV aperture, 6 mm diameter, were recorded at 10 nm sensitivity against white and black calibration tiles using a benchtop spectrophotometer. Subsequently, they were converted into CIEDE 2000 TP₀₀. After baseline measurements (T0), the specimens were divided as follows (n = 8): staining in coffee (C) and wine (W), for 60 (T1) and 120 hours (T2), and accelerated artificial aging (A). Artificial aging (ISO 4892-2 standard) was performed in two cycles of 150 KJ/m², for T1 and T2, respectively. TP measurements were repeated at T1 and T2. Data of TP₀₀ retention were submitted to analysis of variance and Fisher’s PLSD multiple comparison test (α=0.05).

Results

Fisher’s PLSD critical differences among materials, time intervals and staining/aging were 0.16, 0.11 and 0.11, respectively. SH showed the highest TP₀₀ followed by LU > CS > IE = VS > VE. For all time intervals, the lowest TP₀₀ retention was observed with C. W, and A presented similar values.

Conclusions

Translucency Parameter was a time and staining/aging-dependent material. In majority of cases, it decreased upon staining/aging.

Evaluation of the Color Stability of 3D-Printed Crown and Bridge Materials against Various Sources of Discoloration: An In Vitro Study

Recent advances in three-dimensional (3D) printing have introduced new materials that can be utilized for dental restorations. Nonetheless, there are limited studies on the color stability of restorations using 3D-printed crowns and bridge resins. Herein, the color stability of conventional computer-aided design/computer-aided manufacturing (CAD/CAM) blocks and 3D-printing resins was evaluated and assessed for their degrees of discoloration based on material type, colorant types (grape juice, coffee, curry, and distilled water (control group)), and storage duration (2, 7, and 30 days) in the colorants. Water sorption, solubility, and scanning electron microscope (SEM) analyses were conducted. A three-way ANOVA analysis showed that all three factors significantly affected the color change of the materials. Notably, the discoloration (ΔE₀₀) was significantly higher in all 3D printing resins (4.74–22.85 over the 30 days) than in CAD/CAM blocks (0.64–4.12 over the 30 days) following immersion in all colorants. 3D-printing resins showed color differences above the clinical limit (2.25) following storage for 7 days or longer in all experimental groups. Curry was the most prominent colorant, and discoloration increased in almost all groups as the storage duration increased. This study suggests that discoloration must be considered when using 3D printing resins for restorations.

Investigation the effects of whitening toothpastes on color change of resin-based CAD/CAM blocks

INTRODUCTION

Some colorant foods and beverages cause undesired discoloration on dental restorations. The aim of this study was to investigate the effect of whitening kinds of toothpaste with different active ingredients on the color change of resin-based CAD/CAM blocks.

MATERIAL AND METHODS

In the study, resin-based CAD/CAM block samples sized 1.5 × 7 × 12 mm, were prepared. Then, to simulate the time-dependent color change, the samples were immersed in coffee (Nescafe Classic, Nestlé) for 14 days. After the color change values of the samples colored in coffee were measured by spectrophotometer, the samples were brushed with different types of whitening toothpastes for 4 minutes. Statistical analysis of the color change (ΔE₀₀ ) was performed using the one-way analysis of variance (ANOVA).

RESULTS

Color differences occurring on all resin-based CAD/CAM blocks immersed in coffee for 14 days exceeded the 50%:50% perceptibility threshold (PT) (ΔE₀₀ :0.8). There was no statistical significant difference between the whitening toothpastes containing activated charcoal, hydrogen peroxide (HP), blue covarine pigment, and microparticles in color improvement on resin-based CAD/CAM blocks (P > .05).

CONCLUSION

It has been verified that the discoloration on resin-based CAD/CAM blocks exhibiting color difference above the PT after coffee immersion can be reduced by utilizing toothpastes containing whiteners.

CLINICAL SIGNIFICANCE

Color changes that occur over time in resin-based CAD/CAM blocks can be a clinical problem. These color changes in the materials can be reduced below the PT level using whitening toothpastes.

Analysis of color differences in stained contemporary esthetic dental materials

STATEMENT OF PROBLEM

Although contemporary analytical methods are available for application to data which exhibit a lack of equality of variances or a lack of normality in the error distribution, little guidance is provided for selecting the methods of data handling and analysis which best fit color difference data for stained esthetic materials.

PURPOSE

The purposes of this in vitro study were to apply information criteria of analysis of variance (ANOVA) methods of differing error distributions and covariance structures when analyzing color differences to determine the degree of alienation among 3 Commission Internationale de l'Eclairage (CIE) color difference formulae to assess the linearity of relationships among these formulae and to independently assess differences among various computer-aided design and computer-aided manufacture (CAD-CAM) materials in any color change after common forms of staining over time.

MATERIAL AND METHODS

Hybrid ceramic, resin nanoceramic, feldspathic-ceramic, and lithium-disilicate ceramic specimens (N=128) were subjected to staining from water, tea, coffee, and red wine over 1, 7, and 30 days, with color differences calculated from baseline. Akaike information criteria (AIC) and Bayesian information criteria (BIC) values were determined for Gaussian and lognormal error distributions at covariance structures of standard variance components and compound-symmetry. The analysis of variance used to analyze any significant effects on these color differences was the one with the lowest AIC and BIC values. Then, for each solution, day, and CIE color difference formula, any significant difference in the color differences between all pairs of materials was found by Bonferroni-corrected Student t tests. Those statistically significant pairwise comparisons where the larger of the color differences met or exceeded the acceptability threshold were labeled as statistically and visually noteworthy.

RESULTS

For this color difference data set, the lognormal error distribution and the covariance structure of compound symmetry provided the best AIC and BIC. Because the interaction between material, solution, and day was statistically significant (P<.001), pairwise comparisons were made between all pairs of materials for each level of solution and day studied. Noteworthy differences were identified, where hybrid ceramic and resin nanoceramic each had color changes after staining in coffee and red wine that were greater than each of feldspathic-ceramic and lithium-disilicate ceramic.

CONCLUSIONS

AIC and BIC values evaluate distinctively the Gaussian and lognormal error distributions when analyzing highly varying color differences. Although there is a high linear correlation between the 3 color difference formulae studied, each formula is unique, and each represents a different assessment of the perceived color difference. CAD-CAM materials, staining liquids, and time points affected the notable color changes.

Do resin-based composite CAD/CAM blocks release monomers?

OBJECTIVE

The present study aimed to identify and quantify the elution of monomers of five different resin-based CAD/CAM blocks (RCBs) using HPLC.

METHODS

Five different RCBs were used in the study: GC Cerasmart (CS), Voco Grandio blocs (GR), 3M Lava Ultimate (LU), Shofu Block (SB), and Vita Enamic (VE). Fifteen samples from each material were prepared using a low-speed precision diamond saw (ISOMET Buehler, Lake Bluff, IL, USA) at 5 × 5 × 4 mm size. After the preparation of samples, an extraction solution was mixed with %75/%25 ethanol/water. The samples were stored in the amber-colored bottles during three different immersed periods as 1 h, 24 h, and 90 days (n = 5). After immersion, 0.5 ml solutions were taken from each bottle and analyzed using HPLC.

RESULTS

A total of 16.7 μg/ml of monomers from SB, 13.4 μg/ml of monomers from GR, 13.2 μg/ml of monomers from CS, and 6.7 μg/ml of monomers from LU were found after 3-m immersion. TEGDMA after 3-m of immersion was only released from the SB group, and also BisEMA was released from the CS group. Among the specimens immersed for 1 h, UDMA was released the least from the LU group and the most from the GR group (p < 0.05). Correspondingly, 24 h and 3 m after immersion, the highest release of monomers was found in the GR (p < 0.05).

CONCLUSIONS

When the monomer release from RCBs was evaluated, it was shown that these materials released methacrylate-based monomers except VE, especially if they were kept in a solvent solution for a long time such as 3 m.

CLINICAL SIGNIFICANCE

The novel resin-based CAD/CAM blocks might monomer release, which may cause cytotoxic effects. But, the detected amount of monomer release is below the estimated daily limit.