Effect of chromogenic beverages on color stability and surface roughness of CAD/CAM resin-matrix ceramics: an in vitro study

Abstract

Purpose

This study evaluated the effects of commonly consumed chromogenic beverages on the color stability and surface roughness of three CAD/CAM resin-matrix ceramics at different time intervals. The study aims to provide comparative data under standardized immersion conditions, addressing a gap in time-dependent color and surface alterations of CAD/CAM resin-matrix ceramics.

Materials and Methods

A total of 168 specimens were prepared from three CAD/CAM resin-matrix ceramics (Vita Enamic HT 2M2, Cerasmart HT A2, and Brava HT A2). Specimens were immersed in distilled water, coffee, cola, or red wine at 37 °C for up to 12 days. Color (ΔE₀₀, CIE L*a*b*), and surface roughness (Ra) were measured at baseline, 3, 6, and 12 days. Two-way repeated-measures ANOVA (factors: beverage and time) followed by post-hoc tests (α=0.05) was used for statistical analysis.

Results

Red wine produced the highest color change in all materials (p<0.001), followed by coffee, whereas cola and water resulted in significantly lower ΔE₀₀ values. At day 12, Vita Enamic showed greater discoloration and roughness than Cerasmart and Brava (p<0.05). Both ΔE₀₀ and Ra increased significantly with time (p<0.001).

Conclusion

Exposure to chromogenic beverages significantly affected both color stability and surface roughness of CAD/CAM resin-matrix ceramics. Red wine and coffee were the most aggressive agents, while Cerasmart demonstrated the best stability. Routine dietary counseling and periodic repolishing may be advisable to preserve the long-term esthetic integrity of CAD/CAM restorations.

Introduction

In recent years, increasing esthetic demands have led to a growing preference for all-ceramic and hybrid restorations in restorative dentistry. These materials combine high wear resistance, biocompatibility, translucency, and satisfactory color stability, making them suitable for both anterior and posterior applications. Recent reviews have emphasized that the evolution of CAD/CAM ceramics and resin-matrix materials has transformed restorative workflows by improving strength, repairability, and manufacturing precision (1, 2).

Hybrid ceramics and resin nanoceramics have gained particular attention for combining the favorable optical and mechanical properties of ceramics and composites (3, 4, 5, 6). Hybrid ceramics such as Vita Enamic consist of a feldspathic ceramic network infiltrated by polymer, while resin nanoceramics like Cerasmart or Brava contain densely packed silica and barium-glass nanofillers within a UDMA-based resin matrix. These new CAD/CAM resin-matrix ceramics demonstrate superior elasticity, polishability, and repairability compared to conventional ceramics, while maintaining clinically acceptable esthetics (7).

Color stability plays a key role in the long-term success of esthetic restorations. Discoloration is influenced by both intrinsic factors (e.g., resin composition, filler load, polymerization degree) and extrinsic factors (e.g., dietary habits, staining beverages, and oral hygiene) (8, 9, 10). Chromogenic beverages such as coffee, red wine, and cola are known to cause color changes and surface degradation in resin-matrix ceramics through pigment adsorption, resin hydrolysis, and filler exposure (11, 12, 13). Recent studies confirm that surface roughness is directly correlated with pigment retention, affecting gloss and bacterial adhesion (14, 15).

Despite extensive research, limited comparative data exist regarding how different CAD/CAM resin-matrix ceramics respond to staining under standardized, time-dependent immersion conditions. Unlike previous reports that examined isolated materials or short-term immersion, the present study directly compares three commercially available CAD/CAM resin-matrix ceramics—Vita Enamic, Cerasmart, and Brava—under identical protocols. This design allows material-specific assessment of discoloration and surface roughness kinetics, providing reproducible evidence relevant to everyday clinical practice (16).

Hence, the present study aimed to compare the effects of commonly consumed chromogenic beverages on the color stability and surface roughness of three CAD/CAM resin-matrix ceramics at 3, 6, and 12 days. The null hypotheses were that the type of beverage and material would not significantly affect color or roughness; and both parameters would remain unchanged over time.

Materials and Methods

Sample size and study design

Power analysis was performed using G*Power v3.1.9 to determine the ideal sample size. Assuming a medium effect size (f = 0.4), with 95% power and a 95% confidence level, the calculation indicated that 14 specimens per cell would be sufficient for a two-way ANOVA (3 CAD/CAM materials × 4 beverage groups) design. Accordingly, 56 specimens were planned for each CAD/CAM block, which was divided into four subgroups containing 14 specimens each, resulting in a total of 168 specimens.

Specimen preparation

Three CAD/CAM resin-matrix ceramics were evaluated: a hybrid ceramic (Vita Enamic HT 2M2; VITA Zahnfabrik, Bad Säckingen, Germany), a resin nanoceramic (Cerasmart HT A2; GC Corporation, Tokyo, Japan), and a glass-ceramic-containing resin composite (Brava HT A2; FGM Produtos Odontológicos, Joinville, Santa Catarina, Brazil). The main compositional features of each material are listed in Table 1.

Table 1.

CAD/CAM resin-matrix ceramics used in this study

Material	Material type	Main composition	Manufacturer	Lot No
Vita Enamic	Hybrid ceramic	86 wt.% feldspathic ceramic, 14 wt.% polymer (UDMA, TEGDMA)	VITA Zahnfabrik, Bad Säckingen, Germany	204140
GC Cerasmart	Resin nanoceramic	71 wt.% resin matrix containing silica and barium glass fillers (20–300 nm)	GC Corporation, Tokyo, Japan	2308026
FGM Brava	Glass-ceramic-containing resin composite	80 wt.% silica, 20 wt.% resin matrix (0.5–40 μm)	FGM Produtos Odontológicos, Joinville, Santa Catarina, Brazil	170522

UDMA; urethane dimethacrylate; TEGDMA; triethylene glycol dimethacrylate; wt: %, weight percent.

A total of 168 specimens (n = 56 per material) were sectioned from CAD/CAM blocks into slices measuring 12×7×1.5 mm using a precision cutting machine (Isomet; Buehler Ltd., Lake Bluff, IL, USA) with a diamond wafering blade under continuous water cooling. Each specimen was polished for 60 seconds using 600-grit silicon carbide paper (3M ESPE, St. Paul, MN, USA), rinsed thoroughly with distilled water and air-dried to standardize the surface texture.

Standard restorative finishing protocols often include both polishing and glazing to optimize surface characteristics.(17) However, after clinical adjustments, polished surfaces are generally considered clinically relevant, as re-glazing is not routinely performed chairside and requires additional laboratory procedures.(18) Polishing alone has been shown to produce surface roughness values comparable to those of glazed surfaces following occlusal adjustments.(19) Therefore, glazing was intentionally omitted to simulate post-adjustment clinical conditions and to isolate the effect of mechanical polishing on surface roughness and optical properties.

The polishing protocol was selected based on widely used in vitro surface preparation procedures to achieve a standardized and reproducible baseline surface. The use of 600-grit silicon carbide paper has been commonly reported to simulate surface alterations produced by clinical finishing procedures,(20) and a polishing duration of 60 seconds was chosen to ensure uniform abrasion while avoiding excessive material removal, as polishing time significantly influences surface roughness outcomes.(21) Although this standardized protocol may influence absolute roughness values, the application of identical surface preparation procedures to all specimens allows reliable comparative evaluation of time-dependent changes in surface roughness and optical properties.(20, 21) In addition, the omission of glazing reflects clinically relevant post-adjustment conditions, as polished surfaces are commonly evaluated in chairside practice.(19)

Color and surface roughness measurements

Baseline measurements were recorded for each specimen. Color (CIE L*a*b*) was measured using a dental spectrophotometer (Vita Easyshade Compact; VITA Zahnfabrik, Bad Säckingen, Germany), and surface roughness (Ra, µm) was determined using a contact profilometer (Surtronic S128; Taylor Hobson, Leicester, UK). Each specimen was measured three times, and the mean value was used for statistical analysis.

The samples were randomly assigned to four immersion media: distilled water, coffee (3.6 g instant coffee per 300 mL water), cola (The Coca-Cola Company, Atlanta, GA, USA), and red wine (Lucien Arkas Vineyards Idol, Torbalı, Turkey). Immersions were conducted at 37 °C for 12 days in an incubator, and the solutions were renewed daily to maintain stability. Measurements of color and surface roughness were repeated after 3, 6, and 12 days following the same procedure used at baseline.The immersion durations in this study were selected based on established in vitro staining protocols designed to simulate cumulative clinical exposure to chromogenic beverages (22, 23) In vitro aging models commonly use stepwise immersion periods to assess time-dependent discoloration and surface roughness changes.(24) In this context, 24 hours of in vitro staining has been reported to approximate one month of clinical exposure.(25) Accordingly, immersion periods of up to 12 days have been used in accelerated aging protocols and considered equivalent to nearly one year of intraoral exposure.(26, 27) Based on this rationale, immersion durations of 3, 6, and 12 days were selected to represent early, intermediate, and extended exposure periods, enabling evaluation of progressive changes in surface roughness and optical properties. Importantly, the use of multiple immersion durations allowed systematic assessment of time-dependent trends within the same experimental design while minimizing inter-sample variability. This approach is consistent with previously published laboratory aging studies while acknowledging the limitations of in vitro simulations.(28) Color differences (ΔE₀₀) were calculated using the CIEDE2000 formula, adopting perceptibility (ΔE₀₀ = 0.8) and acceptability (ΔE₀₀ = 1.8) thresholds as suggested by Paravina et al. (29).

The experimental design of the staining phase is illustrated in Figure 1.

Figure 1.

Experimental design of the staining phase.

Statistical analysis

Statistical analysis was performed using IBM SPSS Statistics 26.0 (IBM Corp., Armonk, NY, USA). The normality of data distribution was evaluated using the Shapiro–Wilk test. Since all variables showed normal distribution, results were expressed as mean ± standard deviation. Differences among groups were analyzed using two-way repeated-measures ANOVA with factors of beverage and time. When significant differences were detected, Duncan's post-hoc test was applied for pairwise comparisons. p<0.05 was considered as statistical significance.

Results

All materials exhibited measurable color changes over time, with significant effects of both beverage and storage duration (p<0.001, Table 2).

Table 2.

Mean color change values (ΔE00, mean ±SD) of CAD/CAM resin matrix ceramics immersed in different beverages at 3, 6, and 12 days.

Material	Beverage	Day 3	Day 6	Day 12
Vita Enamic	Distilled water	0.4 ± 0.1 (p = 0.412)	0.5 ± 0.1 (p = 0.326)	0.6 ± 0.1 (p = 0.284)
	Coffee	1.2 ± 0.2 (p = 0.038)	1.9 ± 0.3 (p = 0.021)	2.6 ± 0.4 (p < 0.001)
	Cola	0.8 ± 0.2 (p = 0.128)	1.0 ± 0.2 (p = 0.084)	1.3 ± 0.3 (p = 0.041)
	Red wine	2.4 ± 0.3 (p < 0.001)	3.5 ± 0.4 (p < 0.001)	4.8 ± 0.5 (p < 0.001)
Cerasmart	Distilled water	0.3 ± 0.1 (p = 0.519)	0.4 ± 0.1 (p = 0.366)	0.5 ± 0.1 (p = 0.247)
	Coffee	0.9 ± 0.2 (p = 0.042)	1.5 ± 0.3 (p = 0.034)	2.0 ± 0.3 (p = 0.017)
	Cola	0.6 ± 0.1 (p = 0.151)	0.8 ± 0.2 (p = 0.103)	1.0 ± 0.2 (p = 0.067)
	Red wine	1.9 ± 0.3 (p < 0.001)	2.7 ± 0.3 (p < 0.001)	3.9 ± 0.4 (p < 0.001)
Brava	Distilled water	0.3 ± 0.1 (p = 0.486)	0.4 ± 0.1 (p = 0.335)	0.5 ± 0.1 (p = 0.262)
	Coffee	0.8 ± 0.2 (p = 0.047)	1.2 ± 0.2 (p = 0.031)	1.7 ± 0.3 (p = 0.019)
	Cola	0.5 ± 0.1 (p = 0.172)	0.7 ± 0.1 (p = 0.118)	0.9 ± 0.2 (p = 0.083)
	Red wine	1.6 ± 0.2 (p < 0.001)	2.2 ± 0.3 (p < 0.001)	3.1 ± 0.3 (p < 0.001)

Red wine immersion produced the greatest discoloration in all materials, exceeding the clinical acceptability threshold (ΔE₀₀>1.8) at every evaluation point (Vita Enamic: p<0.001 at days 3–12; Cerasmart: p<0.001 at days 3–12; Brava: p<0.001 at days 3–12).

Coffee also caused significant color changes, with ΔE₀₀ values surpassing the threshold by day 6 (Vita Enamic: p=0.038 at day 3, p=0.021 at day 6, p<0.001 at day 12; Cerasmart: p=0.042, p=0.034, p=0.017; Brava: p=0.047, p=0.031, p=0.019).

Cola showed a mild but significant effect only at the final evaluation (Vita Enamic: p = 0.041 at day 12; Cerasmart: p=0.067; Brava: p=0.083), whereas distilled water produced the lowest ΔE₀₀ values and no significant color change (Vita Enamic: p=0.284; Cerasmart: p=0.247; Brava: p=0.262) throughout storage.

When materials were compared, Vita Enamic exhibited significantly higher ΔE₀₀ values than Cerasmart and Brava in the red-wine (p<0.001), coffee (Vita Enamic p<0.001; Cerasmart p=0.017; Brava p=0.019), and cola (p=0.041) groups, whereas no significant difference was found in the water group (p>0.2, Figure 2). Cerasmart consistently demonstrated the best color stability among the tested materials.

Figure 2.

Time-dependent ΔE₀₀ changes of Vita Enamic specimens immersed in different beverages. Dashed lines indicate perceptibility (ΔE₀₀=0.8) and acceptability (ΔE₀₀=1.8) thresholds.

Baseline Ra values did not significantly differ among materials (p>0.05). Over time, all specimens demonstrated increased surface roughness after immersion (p<0.001, Table 3). Coffee immersion caused the most pronounced increase in Ra, particularly in Vita Enamic, where values exceeded the clinical threshold of 0.2 µm by day 12 (p=0.047). Red wine also significantly increased surface roughness compared with cola and distilled water (Vita Enamic p=0.029; Cerasmart p=0.028; Brava p=0.029; Vita Enamic day 3 p=0.048).

Table 3.

Mean surface roughness values (Ra, µm; mean ±SD) of CAD/CAM resin matrix ceramics immersed in different beverages at baseline, 3, 6, and 12 days.

Material	Beverage	Baseline	Day 3	Day 6	Day 12
Vita Enamic	Distilled water	0.12 ± 0.01 (p = 0.374)	0.13 ± 0.01 (p = 0.298)	0.13 ± 0.01 (p = 0.267)	0.14 ± 0.01 (p = 0.224)
	Coffee	0.12 ± 0.01 (p = 0.092)	0.16 ± 0.02 (p = 0.041)	0.20 ± 0.02 (p = 0.027)	0.25 ± 0.03 (p = 0.047)
	Cola	0.12 ± 0.01 (p = 0.184)	0.14 ± 0.01 (p = 0.133)	0.15 ± 0.01 (p = 0.078)	0.17 ± 0.02 (p = 0.056)
	Red wine	0.12 ± 0.01 (p = 0.123)	0.15 ± 0.02 (p = 0.048)	0.18 ± 0.02 (p = 0.034)	0.21 ± 0.02 (p = 0.029)
Cerasmart	Distilled water	0.11 ± 0.01 (p = 0.492)	0.12 ± 0.01 (p = 0.347)	0.12 ± 0.01 (p = 0.296)	0.12 ± 0.01 (p = 0.278)
	Coffee	0.11 ± 0.01 (p = 0.125)	0.14 ± 0.01 (p = 0.042)	0.16 ± 0.02 (p = 0.031)	0.18 ± 0.02 (p = 0.024)
	Cola	0.11 ± 0.01 (p = 0.189)	0.12 ± 0.01 (p = 0.157)	0.13 ± 0.01 (p = 0.102)	0.14 ± 0.01 (p = 0.073)
	Red wine	0.11 ± 0.01 (p = 0.101)	0.13 ± 0.01 (p = 0.047)	0.15 ± 0.01 (p = 0.036)	0.17 ± 0.02 (p = 0.028)
Brava	Distilled water	0.10 ± 0.01 (p = 0.437)	0.11 ± 0.01 (p = 0.314)	0.11 ± 0.01 (p = 0.271)	0.11 ± 0.01 (p = 0.254)
	Coffee	0.10 ± 0.01 (p = 0.162)	0.13 ± 0.01 (p = 0.049)	0.14 ± 0.01 (p = 0.039)	0.16 ± 0.02 (p = 0.031)
	Cola	0.10 ± 0.01 (p = 0.221)	0.11 ± 0.01 (p = 0.174)	0.12 ± 0.01 (p = 0.129)	0.13 ± 0.01 (p = 0.091)
	Red wine	0.10 ± 0.01 (p = 0.139)	0.12 ± 0.01 (p = 0.048)	0.13 ± 0.01 (p = 0.037)	0.15 ± 0.01 (p = 0.029)

Among materials, Vita Enamic exhibited higher Ra values than Cerasmart (coffee p=0.024; red wine p=0.028) and Brava (coffee p=0.031; red wine p=0.029) after immersion in both coffee and red wine (Figure 3).No clinically significant roughness was observed in cola (p=0.056–0.091) or water (p=0.224–0.278) groups at any time point.

Figure 3.

Surface roughness (Ra) changes of Vita Enamic specimens after beverage immersion. Dashed line represents the clinical roughness threshold (Ra=0.2 μm).

Discussion

The present study investigated the effects of common staining beverages on the color stability and surface roughness of three CAD/CAM resin matrix ceramics. The findings of this study partially rejected the null hypotheses, as both the type of beverage and the material composition significantly affected color stability and surface roughness, and both parameters showed measurable changes over time. These results indicate that CAD/CAM resin-matrix ceramics are susceptible to optical and topographical alterations depending on their chemical structure and environmental exposure. This aligns with recent reports highlighting that the optical performance of CAD/CAM resin-matrix ceramics is governed by polymer chemistry, filler morphology, and beverage pH (16).

A contact profilometer was selected to assess surface roughness because it provides quantitative and reproducible Ra measurements over relatively large surface areas, allowing direct comparison with previously published dental materials studies and clinically relevant thresholds such as plaque retention (30). Although scanning electron microscopy (SEM) and atomic force microscopy (AFM) offer high-resolution surface imaging, SEM primarily provides qualitative information without standardized numerical roughness values, while AFM, despite its nanoscale sensitivity, is limited by small scanning areas that may not adequately represent the overall surface condition.(31, 32) While profilometry mainly records two-dimensional surface profiles and may not capture nanoscale features, it remains widely accepted for comparative and time-dependent roughness analysis in dental materials research when identical measurement conditions are applied across all groups.(33, 34) Cerasmart's superior color stability may be attributed to its UDMA-based matrix, which exhibits lower water sorption and pigment uptake than Bis-GMA–dominant systems (4, 35). The densely cross-linked nanofillers in Cerasmart act as a diffusion barrier, minimizing pigment penetration, whereas the dual-network structure of Vita Enamic allows micro-gap formation that facilitates fluid ingress and staining (3, 35, 36, 37). These microstructural and compositional differences explain the observed variation in ΔE00 values among materials and confirm that chemical architecture directly influences staining behavior (16).

The reduced polarity and higher cross-link density of UDMA-based matrices in Cerasmart likely limit the diffusion of polyphenolic pigments and acidic molecules, providing a structural explanation for its enhanced color stability and surface integrity. This mechanism supports the observed resistance to hydrolytic and alcohol-induced degradation in UDMA-rich hybrid ceramics (38).

Beverage type played a crucial role. Red wine and coffee produced the greatest discoloration due to their acidic pH, polyphenolic pigments, and alcohol content, which enhance polymer plasticization and surface softening (16, 39). Cola, although acidic, lacks chromogenic molecules and produced comparatively lower color change, confirming findings from recent in vitro staining studies (40).

Surface roughness followed a similar trend. Low-pH and ethanol-containing beverages promote matrix degradation and filler exposure, creating micro-irregularities that increase pigment retention (41). The strong correlation between ΔE00 and Ra values in this study supports the idea that rougher surfaces not only reduce gloss but also facilitate microbial colonization (30, 42). Importantly, all materials except Vita Enamic maintained Ra values below the clinically critical threshold of 0.2 µm. This observation is consistent with recent reports by Yıldırım-Işık and Büyükgöze-Dindar (37) indicating that Vita Enamic shows greater susceptibility to acidic degradation.

These outcomes are consistent with recent systematic reviews emphasizing the time-dependent degradation of resin-matrix ceramics under acidic and alcoholic conditions, confirming that beverage composition and polymer network density are decisive factors for color and surface stability (43). The findings underline the clinical importance of selecting stain-resistant materials and providing dietary counseling to patients regarding the consumption of chromogenic beverages. Regular maintenance polishing and professional cleaning may help preserve both esthetic appearance and surface smoothness of CAD/CAM restorations (44). The comparative design and standardized immersion protocol employed in this study ensured reproducibility and enabled meaningful cross-material evaluation, representing a methodological advancement over previous single-material investigations. Furthermore, aligning immersion duration with clinically relevant exposure periods allowed prediction of long-term esthetic outcomes without complex aging simulations. The primary limitation of this in vitro study is the absence of thermal and mechanical aging, which could further influence color and roughness outcomes. Although 12-day continuous immersion approximates one year of beverage exposure (13), real intraoral conditions involve fluctuating pH, temperature, and salivary enzymes. Nevertheless, the standardized immersion protocol enhances reproducibility and isolates the intrinsic material response to chromogenic agents (16). Future studies incorporating thermocycling, brushing simulation, and SEM/AFM surface imaging are warranted to visually validate the observed alterations and to evaluate the reversibility of discoloration after repolishing. Overall, the results provide clinically relevant insights into the long-term esthetic performance of CAD/CAM resin-matrix ceramics and establish a foundation for further investigations on repolishing and whitening strategies.

Conclusion

Within the limitations of this study, exposure to chromogenic beverages significantly affected the color stability and surface roughness of CAD/CAM resin-matrix ceramics. Red wine and coffee caused the most pronounced color and surface alterations, whereas Cerasmart demonstrated the greatest resistance to staining and degradation.

Differences among materials were closely related to their resin chemistry and filler microstructure, confirming that polymer backbone and network density are decisive factors for esthetic performance. Clinically, these results emphasize the need for careful material selection, dietary guidance, and periodic repolishing to maintain the esthetic longevity of CAD/CAM restorations.