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Article

Impact of Collagen Peptide Supplements Dissolved in Different Beverages on the Surface Properties of Dental Restorative Materials

by
Zeynep Hale Keles
1,*,
Rana Turunc
2 and
Soner Sismanoglu
3
1
Department of Restorative Dentistry, Faculty of Dentistry, Istanbul Atlas University, Atlas Vadi Kampüsü, Anadolu Cd. No: 40, Kağıthane, 34408 Istanbul, Türkiye
2
Department of Prosthodontics, Faculty of Dentistry, Altinbaş University, 34147 Istanbul, Türkiye
3
Department of Restorative Dentistry, Faculty of Dentistry, Istanbul University-Cerrahpaşa, 34098 Istanbul, Türkiye
*
Author to whom correspondence should be addressed.
Appl. Sci. 2026, 16(5), 2581; https://doi.org/10.3390/app16052581
Submission received: 9 February 2026 / Revised: 27 February 2026 / Accepted: 6 March 2026 / Published: 8 March 2026
Versions Notes

Abstract

The increasing popularity of collagen peptide supplements raises concerns about their potential effects on dental restorations. This in vitro study investigated the effects of collagen peptide supplements dissolved in different beverages on the color stability, profile arithmetic mean roughness (Ra), and gloss of various restorative materials. Four restorative materials were tested: a nanofilled composite resin (Filtek Universal), a CAD/CAM composite block (Tetric CAD), a hybrid ceramic (Vita Enamic), and a leucite-reinforced glass-ceramic (IPS Empress CAD). Specimens were immersed in three collagen solutions (Pure Collagen Water Mix, Pure Collagen Coffee Mix, and Purple Collagen) and distilled water (control) for periods simulating 1 and 6 months of daily consumption. Color changes (ΔE00), Ra, and gloss were measured at baseline, after two immersion periods, and following repolishing. Results showed that collagen peptide supplements significantly affected all tested properties, with effects varying by material type and solution composition. Empress CAD demonstrated superior resistance to staining and surface property changes, while Filtek Universal exhibited the highest susceptibility. Collagen supplements mixed with coffee and those containing anthocyanin-rich ingredients produced more pronounced effects than water-mixed formulations. All materials remained within clinically acceptable thresholds for Ra and maintained adequate gloss values. Repolishing improved surface properties in all materials, though resin-based materials showed persistent discoloration due to internal staining. These findings suggest that material selection should be considered carefully for patients who regularly consume collagen peptide supplements, with ceramic and hybrid materials being preferable for aesthetic restorations.

1. Introduction

There is a growing demand among consumers for products that enhance, protect, or provide cosmetic benefits for their health. Many of these products are classified as nutritional supplements rather than pharmaceuticals, and access to these supplements is relatively easy. Products containing collagen have also gained significant popularity, driven by media influence and increased awareness regarding lifestyle supplements. This has led to heightened societal interest in these offerings [1]. The global collagen supplement market was valued at approximately USD 1.8 billion in 2025 and is projected to reach approximately USD 3.3 billion by 2035 [2].
Collagen serves as the predominant structural protein in connective tissues, including the skin, tendons, cartilage, and bones, accounting for 25–30% of the total protein composition in the human body [3]. As the principal element of the extracellular matrix, collagen is essential for the integrity, continuity, and regeneration of tissues [4]. Collagen is synthesized in various forms within the human body, with approximately ninety percent comprising types I, II, and III [5]. Collagen has a high molecular weight, which significantly complicates the body’s absorption. Therefore, any collagen intended for supplementation must undergo hydrolysis into smaller peptides and amino acids with a low molecular weight to enhance bioavailability [6]. Hydrolyzed collagen, commonly called collagen peptide, is a water-soluble protein hydrolysate obtained through enzymatic or acidic hydrolysis of collagen derived from animal sources [5,7] and can be easily consumed as a supplement dissolved in various beverages [8].
Collagen peptides have been associated with various potential health benefits, although the strength of evidence varies across different outcomes. Their utilization has been reported to facilitate collagen synthesis [9], help manage bone and joint conditions [10], mitigate the effects of skin aging [11], accelerates the healing of wounds and damaged tissues [12], and reduce arterial stiffness [13]. Furthermore, collagen peptides may increase HDL cholesterol levels and possess antioxidant and anti-inflammatory properties [8]. However, as interest and consumer consumption increase, the lack of clear clinical evidence for many of these claims remains a limitation [14]. Since collagen supplements are typically consumed by dissolving them in liquids and taken orally, it is necessary to evaluate not only their effects on general health but also their potential effects in the oral environment.
Given that collagen peptides are predominantly consumed as supplements dissolved in various beverages, the oral cavity is routinely exposed to these solutions. This exposure raises questions about the potential effects of collagen-containing drinks on the physical and optical properties of dental restorations. Restorative materials exposed to the oral environment may undergo color changes due to extrinsic and intrinsic factors. The consumption of pigmented foods and beverages, poor oral hygiene, mouthwashes, and smoking can be considered extrinsic factors [15]. Intrinsic factors result from changes in the structural properties of the material, such as oxidation of residual monomers, water sorption, and filler size and percentage [16]. Surface roughness is thought to be associated with color stability. Rough surfaces promote biofilm adhesion, leading to caries and periodontal deterioration, and facilitate staining, which can cause color changes [17]. The ability of restorative materials to meet aesthetic expectations in the long term depends on the stability of properties such as color stability, surface roughness, and gloss [18,19].
Among these restorative materials, computer-aided design and manufacturing (CAD/CAM) materials have become increasingly prevalent with the advancement of digital dentistry. The development of CAD/CAM technology has enabled the fabrication of metal-free restorations that can meet the increasing aesthetic expectations and demands of patients in modern times [20]. CAD/CAM systems possess advantages such as time savings, minimizing human errors, precision, and accuracy, in addition to their advanced aesthetic properties [21]. Polymer-based CAD/CAM bioceramic blocks have been developed due to some clinical disadvantages of traditional ceramic CAD/CAM blocks [22]. These materials have a more flexible structure than dental ceramics, and their fabrication and intraoral repair are easier [23,24]. Polymer-based CAD/CAM bioceramic blocks are produced in two categories: resin with dispersed fillers and polymer-infiltrated ceramic networks (hybrid ceramics) [21].
Although extensive research has investigated the effects of various beverages (coffee, tea, wine) on the color stability and surface properties of dental restorative materials, the potential impact of collagen peptide supplements dissolved in beverages remains unexplored. To our knowledge, no studies have evaluated the effects of collagen-containing drinks on the color stability, profile arithmetic mean roughness (Ra), and gloss of dental materials. Therefore, the aim of this laboratory-based study was to investigate the effects of collagen peptide powders dissolved in different liquids on the color, gloss, and Ra of a direct composite resin, a CAD/CAM composite block, a resin-infiltrated hybrid ceramic CAD/CAM block, and a feldspathic CAD/CAM block. The null hypotheses were set as follows: (1) collagen supplements have no effect on the color, Ra, and gloss of the tested materials; (2) there is no difference in color change, Ra, and gloss between the different restorative materials used in the study.

2. Materials and Methods

Three A2-shade CAD/CAM restorative materials were evaluated: a leucite-reinforced glass-ceramic block (IPS Empress CAD, Ivoclar Vivadent AG, Schaan, Liechtenstein), a resin composite block (Tetric CAD, Ivoclar Vivadent AG, Schaan, Liechtenstein), a polymer-infiltrated ceramic block (Vita Enamic, Vita Zahnfabrik GmbH, Bad Säckingen, Germany), and an A2-shade nanofilled composite resin (Filtek Universal Restorative, 3M ESPE, St. Paul, MN, USA). The immersion solutions consisted of two collagen peptide products namely, Collagen Purple (Collagen Purple, Kiperin Pharmaceutical and Food Industry and Trade Co., Ltd., Istanbul, Türkiye) and Pure Collagen (BMO Nutrition Pure Collagen Peptides; Delta Protein International, Inc., Sunflower, MS, USA), prepared with water, a collagen peptide (BMO Nutrition Pure Collagen Peptides; Delta Protein International, Inc., Sunflower, MS, USA) prepared with coffee, and distilled water which served as a control. The compositions of the materials are displayed in Table 1.
Sample size determination was performed with G*Power software (version 3.1, Heinrich Heine University, Düsseldorf, Germany), using color change (ΔE00) as the primary outcome. Drawing from a pilot study and relevant literature on color stability of restorative materials following immersion in staining solutions, an effect size (f) of 0.75 was estimated. Given a significance level (α) of 0.05, a power (1-β) of 0.80, 4 material groups, 4 immersion media subgroups, and 4 time-point measurements, a minimum of 8 specimens per subgroup was determined to be sufficient. To account for potential specimen loss or damage during the experimental procedures, the sample size was increased to 10 specimens per material per immersion medium, resulting in a total of 160 specimens (4 materials × 4 immersion media × 10 specimens).

2.1. Sample Preparation

From each CAD/CAM restorative material, 40 samples were prepared with a precision cutter (Mecatome T180, PRESI, Eybens, France). A digital micrometer (C-master, Mitutoyo, Japan) was used to confirm that all specimens had a 2 mm thickness. FU composite resin specimens were fabricated with dimensions of 10 mm in diameter and 2 mm in thickness. The material was packed into a circular Teflon mold (10 mm diameter, 2 mm depth), and celluloid tape was applied to the upper surface prior to compression between two glass plates to ensure surface smoothness. Following removal of the upper glass plate, polymerization was performed using an LED curing unit (Elipar S10, 3M ESPE, St. Paul, MN, USA) operating at a light intensity of 1200 mW/cm2. Irradiation was carried out for 10 s in accordance with the manufacturer’s recommendations. The specimens were immersed in distilled water at 37 °C for 24 h to allow for complete curing after polymerization. Subsequently, the top and bottom surfaces of the samples were polished sequentially using 600-, 800-, 1000-, and 2000-grit sandpaper under water cooling by the same investigator. To ensure that the values measured at the beginning and after the experiment belonged to the same samples, the surfaces of the samples that would not be measured were numbered. Samples were rinsed for 10 s with distilled water and gently wiped dry. The baseline color analysis, Ra, and gloss measurements of samples were performed.

2.2. Immersion Cycles

After the baseline measurement, the specimens of each group were divided into four subgroups (n = 10) and submerged in three immersion solutions: Collagen Purple mixed with water (Purple Collagen), Pure Collagen mixed with water (Pure Collagen Water Mix), Pure Collagen mixed with coffee (Pure Collagen Coffee Mix), and distilled water which served as a control.
Purple Collagen and Pure Collagen were prepared by dissolving collagen powders (14.4 g for Purple Collagen and 10 g for Pure Collagen) in 200 mL of drinking water at room temperature. For Pure Collagen Coffee Mix, the coffee was prepared by dissolving 1.5 teaspoons of instant coffee powder (Nescafé Gold, Nestlé Deutschland, Frankfurt, Germany) in 150 mL of hot water at 80 °C, as recommended by the manufacturer. Then, 10 g of Pure Collagen powder was added to the coffee. The specimens were submerged in a 10 mL immersion solution. The immersion period was 6 days (a total of 144 h), corresponding to 6 months of consumption, with each day of immersion (24 h) representing 1 month [25,26]. The immersion solutions were renewed daily to prevent bacterial growth.

2.3. Spectrophotometric Color Analysis

Color measurements were performed using a clinical compact spectrophotometer (Vita Easyshade, VITA Zahnfabrik, Bad Säckingen, Germany), which was calibrated prior to each measurement session following the manufacturer’s instructions. During measurements, specimens were positioned on a white background with the probe tip held perpendicular to the specimen center. CIE L*, a*, b* color coordinates, as defined by the International Commission on Illumination, have been extensively employed in dental research for color evaluation of resin composite materials [27]. Baseline L*, a*, b* values were recorded from the unmarked surface of each specimen, with three consecutive readings taken per sample to obtain mean values. All measurements were conducted under D65 standard illuminant conditions in compliance with the CIE L*, a*, b* system. Color differences (ΔE00) were subsequently calculated using the CIEDE2000 formula [22].
Δ E 00 = Δ L ′ k L S L 2 + Δ C ′ k C S C 2 + Δ H ′ k H S H 2 + R T Δ C ′ k C S C Δ H ′ k H S H
The parametric weighting factors kL, kC, and kH were each assigned a value of 1.0, consistent with the reference conditions specified in the CIE technical report [27]. CIEDE2000 color difference values were interpreted against 50%:50% perceptibility and acceptability thresholds of 0.8 and 1.8, respectively, as established in a previously published study. This standardized framework enables objective assessment of color differences with respect to both visual detectability and clinical acceptability [28].

2.4. Ra Measurement

Surface roughness (Ra) measurements were carried out using a contact profilometer (Surtronic S128, Taylor Hobson, Leicester, England, UK), with an evaluation length of 1.25 mm and a cut-off value of 0.25 mm. Three separate regions of each specimen were measured, and the mean value was recorded as the Ra (μm). Calibration of the profilometer was performed prior to every measurement session.

2.5. Gloss Measurement

Gloss measurements were obtained using a gloss meter (GM 26 Glossmeter, Dalian Teren Industry Instrument Co., Ltd., Dalian, China) with a 60° geometry and a square measurement area of 15 × 10 mm, with results expressed in gloss units (GU). The device quantifies the intensity of reflected light from the specimen surface and compares it against a calibrated reference value. To minimize the effect of ambient light and ensure consistent specimen positioning across repeated assessments, an opaque black plastic mold was placed over each specimen during measurement. A total of three readings were taken per specimen, and the mean value was recorded.
Following the immersion period simulating 6 months, the samples’ top and bottom surfaces were repolished as previously described. Color measurements, Ra, and gloss were performed at four time points: baseline, 1 day, 6 days, and after repolishing.

2.6. Statistical Analysis

The normality of data distribution was assessed using the Shapiro–Wilk test, and homogeneity of variances was evaluated using Levene’s test. Since the data exhibited normal distribution and homogeneous variances, parametric tests were employed for statistical analysis.
A repeated-measures analysis of variance (ANOVA) was conducted to evaluate the effects of immersion medium (distilled water, Pure Collagen Water Mix, Pure Collagen Coffee Mix, and Purple Collagen), material type (Filtek, Empress, Tetric, and Vita), and time points (baseline, 1 day, 6 days, and after repolishing) on color change (ΔE00), Ra, and gloss values. Post hoc pairwise comparisons were performed using Bonferroni correction test to identify specific differences between groups. The level of statistical significance was set at p < 0.05. All statistical analyses were performed using SPSS software (version 31, IBM Corp., Armonk, NY, USA).

3. Results

Repeated-measures ANOVA conducted for color difference, Ra, and gloss revealed that the immersion medium had a significant effect on the results (p < 0.001), followed by the material type (p < 0.001). The interaction between immersion medium and material was statistically significant (p < 0.001).

3.1. Spectrophotometric Color Analysis

Table 2 shows the ΔE00 values and their standard deviations of the tested materials after immersion in distilled water and collagen solutions for 1 day, 6 days, and after repolishing. The acceptability threshold (AT) for clinically acceptable color change was established at ΔE00 = 1.8, while the perceptibility threshold (PT) was set at ΔE00 = 0.8.
In distilled water, all materials except FU remained below AT at all time points. FU exceeded AT after both immersion periods but returned below AT after repolishing (p < 0.05). No significant time-dependent changes were observed for IPS, TET, or VE.
Pure Collagen Water Mix caused moderate staining. FU showed the highest color change, exceeding AT at both time points, with a significant increase from 1 day to 6 days (p < 0.05). TET also exceeded AT after immersion. Both materials improved after repolishing, returning to within AT limits. VE and IPS remained below AT throughout all experimental conditions.
Pure Collagen Coffee Mix produced the most severe staining. FU exhibited the highest ΔE00 values among all groups, reaching 8.41 at 6 days, followed by TET. Despite repolishing, both materials remained above AT. VE exceeded AT after immersion but returned below AT after repolishing. IPS consistently remained below AT with no significant changes across time points or after repolishing.
Purple Collagen demonstrated staining patterns similar to Pure Collagen Coffee Mix. FU again showed the highest color change, followed by TET. VE exceeded AT after immersion but improved below AT after repolishing. IPS maintained stable color below AT throughout.
Overall, IPS demonstrated superior color stability across all immersion media, remaining below AT in all conditions. FU was the most susceptible to staining in all media. The staining effect was ranked: Pure Collagen Coffee Mix ≈ Purple Collagen > Pure Collagen Water Mix > Distilled Water.

3.2. Ra Measurements

Table 3 shows the Ra values at baseline, 1 day, 6 days, and after repolishing. All materials remained below the clinically acceptable threshold of 0.2 μm under all conditions. Ra increased progressively over time in all immersion media, with improvement observed after repolishing.
In distilled water, minimal changes in roughness occurred. Collagen solutions caused greater surface alterations, with FU and TET showing significantly higher Ra values compared to IPS and VE at both immersion time points (p < 0.05). Pure Collagen Coffee Mix and Purple Collagen produced the most pronounced increases in roughness. Repolishing effectively reduced Ra in all groups. VE and IPS returned to baseline values after repolishing in most groups, while some differences persisted for FU and TET in collagen solutions.

3.3. Gloss

Table 4 presents gloss meter values at baseline, 1 day, 6 days, and after repolishing. IPS in distilled water and Pure Collagen Water Mix maintained stable gloss throughout the experimental period with no significant changes (p > 0.05). In Pure Collagen Coffee Mix and Purple Collagen, IPS showed a reduction in gloss during immersion, but recovered to baseline after repolishing.
All other materials experienced progressive gloss reduction over time in all immersion media. The magnitude of reduction was greater in collagen solutions compared to distilled water. After repolishing, VE returned to baseline values, while FU and TET showed improvement but did not fully recover to baseline levels. Overall, IPS demonstrated superior gloss retention, particularly in water-based solutions. Filtek consistently showed the greatest gloss reduction across all immersion media.

4. Discussion

The popularity of collagen peptides as dietary supplements is increasing rapidly. However, substances in these supplements and the liquids used to dissolve them may affect the color, gloss, and Ra of dental restorative materials [29,30]. With growing patient demand for aesthetic restorations, both dentists and patients require evidence-based guidance on material selection and supplement formulation choices. This laboratory-based study investigated the effects of collagen peptide solutions prepared in different liquids, exposure duration, and repolishing on the color stability, roughness, and gloss of four restorative materials: nanofilled direct composite (FU), CAD/CAM composite (TET), CAD/CAM hybrid ceramic (VE), and CAD/CAM leucite-reinforced glass-ceramic (IPS). According to the results, collagen peptide solutions caused changes in the color, roughness, and gloss of the tested materials. The only exception was IPS immersed in Pure Collagen Water Mix, which showed no significant change in gloss. Therefore, the first null hypothesis, stating that collagen peptides would have no effect on the color, roughness, and gloss of restorative materials, was partially rejected. The second null hypothesis proposed that there would be no difference in color change, Ra, and gloss among the different restorative materials tested. Statistically significant differences were determined among the tested materials depending on solution type and immersion duration. Therefore, the second null hypothesis was also partially rejected.
Among the tested materials, the direct composite Filtek showed the highest discoloration in all groups, with color stability ranking as IPS > VE > TET > FU. In distilled water, only FU exceeded the clinical acceptability threshold (AT = 1.8). FU’s ΔE00 values exceeded AT in all immersion media. IPS and VE demonstrated lower discoloration than TET and FU in collagen solutions. The staining effect ranked as: distilled water < Pure Collagen Water Mix < Purple Collagen ≈ Pure Collagen Coffee Mix.
Differences in color stability among restorative materials primarily result from their structural compositions [31]. Previous studies demonstrated superior color stability of CAD/CAM blocks compared to direct composites, with ceramic materials outperforming hybrid or resin materials [15,32]. Water sorption in resin composites significantly affects their properties, occurring primarily in the resin matrix [17], and can decrease durability by expanding components, hydrolyzing silane-coupling agents, and causing micro-crack formation, allowing stain penetration [33]. Oxidation of unreacted residual monomers contributes to color changes even without colorant exposure [15]. High conversion degree reduces unreacted monomers, resulting in superior physical properties and better color stability [17,34]. CAD/CAM materials polymerized under controlled industrial conditions, including high-temperature and high-pressure processing, achieve significantly higher degrees of monomer conversion compared to chairside light-cured direct composites, with conversion rates reaching up to 90% [17,20], resulting in higher crosslink density, reduced porosity, and limited water sorption [17,35]. Furthermore, variations in photopolymerization protocol, including curing duration and mode, have been shown to directly influence the mechanical and surface properties of resin-based materials [36], which may partly explain the differences in staining susceptibility observed among the materials tested in the present study. TET’s superior color stability compared to FU can be attributed to its better polymerization. Effective silanization in CAD/CAM materials positively influences water sorption and color stability [34]. Higher inorganic filler content correlates with lower water sorption and better staining resistance [17,34]. VE is a hybrid ceramic with 86% feldspathic ceramic structure; its dense ceramic network significantly limits water sorption and dissolution [17]. Despite containing TEGDMA, a water sorption-sensitive monomer, VE’s color stability in distilled water may be attributed to its high inorganic ceramic content [20].
No previous studies have examined collagen supplements’ effects on restorative materials. However, coffee’s staining effect is well-documented [15,37,38,39]. Coffee’s staining results from polar colorants having absorption and adsorption effects on resin-based materials [40]. Coffee’s acidic pH (4.9–5.2), containing approximately 22 different acids, can alter materials’ microstructure and increase staining capacity [15,20]. Tannins and chlorogenic acid penetrate restorative materials, causing discoloration [15].
Although the study did not include beverage-only control groups, the experimental design inherently allows for several informative internal comparisons that partially address this concern. The observed staining effect ranking (distilled water < Pure Collagen Water Mix < Purple Collagen ≈ Pure Collagen Coffee Mix) itself provides meaningful insight into the relative contributions of different solution components. The comparison between Pure Collagen Water Mix and distilled water reveals the effect of collagen peptides dissolved in a neutral vehicle, with the former producing only marginally greater changes across all outcome measures. The comparison between Pure Collagen Water Mix and Pure Collagen Coffee Mix, which represent the same collagen product dissolved in water versus coffee respectively, isolates the contribution of coffee as a vehicle, demonstrating that coffee substantially amplifies the staining and surface effects observed. Furthermore, the comparison between Pure Collagen Water Mix and Purple Collagen highlights the influence of additional chromogenic ingredients such as anthocyanins and organic acids present in the latter formulation. Taken together, these internal comparisons suggest that the vehicle and accompanying ingredients, rather than collagen peptides per se, are the primary determinants of the observed material changes.
Purple Collagen contains sambucus extract along with other ingredients. Sambucus (elderberry) is rich in anthocyanins, which are water-soluble pigments that cause significant discoloration in restorative materials [29,41]. Yılmaz et al. demonstrated that sambucus-containing beverages caused color changes in CAD/CAM materials [42]. The acidic nature of vitamins in Purple Collagen may have also facilitated microstructural degradation and pigment retention [20,42]. It should be noted that the commercial collagen supplement products evaluated in this study are complex formulations containing numerous ingredients in addition to collagen peptides, including coffee, anthocyanins, organic acids, vitamins, colorants, and flavoring agents. It is unlikely that collagen peptides per se are responsible for the observed changes in color, surface roughness, and gloss of the tested materials; rather, the accompanying ingredients are more plausibly the primary contributing factors. This interpretation is supported by the comparatively favorable performance of the Pure Collagen Water Mix group, which contained fewer additives and no chromogenic agents, and consistently produced the least pronounced changes across all tested materials and outcome measures. Therefore, the findings of this study reflect the effects of the specific commercial products tested and cannot be directly generalized to all collagen peptide supplement formulations. Alternative products dissolved in neutral, non-chromogenic vehicles or formulated without aggressive additives may produce substantially less adverse effects on restorative materials [42,43]. Clinicians may consider advising patients to opt for such formulations when possible.
These findings align with previous studies showing superior color stability of ceramic CAD/CAM materials compared to polymer-infiltrated hybrid ceramics [31], higher staining of resin CAD/CAM blocks compared to ceramics [44,45], and greater discoloration of direct composites [44,46]. Time-dependent color changes have been reported with longer immersion times [45]. In this study, TET showed time-dependent color changes in Pure Collagen Water Mix and Purple Collagen, while TET and VE in coffee-mixed collagen solution showed no significant time-dependent changes.
Surface roughness affects light reflection, thereby influencing the optical characteristics and compromising the mechanical strength and longevity of restorative materials [47]. Biofilm accumulation is promoted on surfaces with Ra values exceeding 0.2 μm, whereas values below this threshold are regarded as clinically acceptable [17]. In the present study, all tested materials exhibited Ra values below 0.2 μm at baseline and following immersion. Nevertheless, a statistically significant increase in Ra was observed for most materials after 1 day and for all materials after 6 days of immersion. Among the materials, FU and TET showed greater surface roughness compared to IPS and VE, both at baseline and following the 6-month aging simulation.
Water sorption causes resin matrix softening, leading to micro-crack formation and surface degradation, with inorganic fillers detaching from the outer surface [17,48]. Other factors including mineral content, temperature, and acid type affect erosive potential [48]. The acidic nature of beverages increases Ra through chemical degradation [24]. Tannic acid in coffee and acids in Purple Collagen may have contributed to increased Ra.
Previous studies reported better surface quality of CAD/CAM materials than direct composites [17] and greater resistance of hybrid ceramics to Ra from staining agents [39]. However, in this study, TET and FU demonstrated similar Ra, and hybrid and feldspathic ceramics showed similar Ra values except in the 6-day Pure Collagen Coffee Mix group, where IPS showed higher Ra values than VE, consistent with reports that acidic beverages combined with high temperatures can significantly increase Ra of feldspathic ceramics [25].
Gloss values exceeded 58 GU for all materials regardless of immersion medium or duration. However, gloss levels varied by material and were affected differently by immersion time. Although gloss values and Ra may correlate, this relationship is not always observed [25]. All materials showed time-dependent roughness increases, yet IPS maintained stable gloss in distilled water and Pure Collagen Water Mix throughout the immersion period. In Pure Collagen Coffee Mix and Purple Collagen, IPS showed significant gloss reduction after 6 months.
Feldspathic ceramics show decreased gloss after exposure to acidic environments [49]. The acids in coffee and Purple Collagen likely affected IPS gloss. FU, VE, and TET showed time-dependent gloss reduction in all immersion media, with TET consistently demonstrating better gloss values than FU. CAD/CAM blocks are considered more resistant to gloss loss due to superior monomer conversion compared to direct composites. Water sorption reduces gloss units of resin materials [19].
Repolishing can remove color deterioration and extend restoration lifespan, with smoother surfaces becoming more resistant to discoloration [26,34,50]. Polishing stained CAD/CAM composites improved surface properties, including color and roughness [51]. In this study, repolishing improved Ra and increased gloss for all affected materials.
Material-dependent variations in ΔE00 changes after repolishing were observed. IPS remained within AT across all immersion media with no significant changes after repolishing. Other materials immersed in collagen showed significant ΔE00 reductions after repolishing [26,34]. VE exceeded AT slightly after immersion in Pure Collagen Coffee Mix and Purple Collagen but fell below PT after polishing, likely due to predominantly external staining. Staining in ceramic structures with high inorganic content percentages is predominantly extrinsic and can be almost completely removed by polishing [26]. In contrast, FU and TET remained above AT after repolishing despite ΔE00 reductions. This incomplete color reversal in resin-based materials results from internal staining in addition to external staining. Composite materials exhibit intrinsic discoloration due to factors including insufficient polymerization, resin matrix type, filler size, and Ra [16,26,44].
The immersion protocol employed in this study (24-h immersion equivalent to approximately one month of clinical exposure) is a well-established and widely used simulation methodology in dental materials research. This calibration has been validated and applied across a broad range of beverages beyond coffee, including tea, cola, red wine, energy drinks, and anthocyanin-containing beverages [42,43,52]. Since the collagen supplement solutions tested in the present study were dissolved in coffee and flavored pigmented beverages, the immersion protocol is directly applicable. The 6-day total immersion period therefore represents a simulated 6-month consumption period, consistent with the standard approach adopted in the literature. The primary limitation of in vitro studies is the inability to fully simulate intraoral conditions. Color, roughness, and gloss of intraoral restorations may be affected by various factors, including oral hygiene, toothbrushing habits, consumption of different beverages, and smoking. Additionally, while only one surface of restorations is exposed to external factors in the oral environment, both surfaces of specimens are exposed to solutions in laboratory studies, potentially causing different levels of material effects compared to the oral environment. Despite these limitations, in vitro studies provide valuable information by enabling comparison of different materials under identical conditions. Supporting these studies with clinical research will provide more comprehensive data.

5. Conclusions

Within the limitations of this in vitro study, collagen peptide supplements significantly affected the color stability, Ra, and gloss of tested restorative materials, with effects varying by material type and solution composition. Ceramic materials demonstrated superior resistance compared to resin-based materials. Collagen supplements mixed with coffee or containing anthocyanin-rich ingredients produced more pronounced staining than water-mixed formulations. While repolishing improved surface properties, resin-based materials showed persistent discoloration due to internal staining. Dental professionals should consider these findings when selecting materials for patients who regularly consume collagen supplements.

Author Contributions

Conception, S.S.; Design, R.T., S.S. and Z.H.K.; Data collection, R.T. and Z.H.K.; Analysis/Interpretation, S.S. and Z.H.K.; Literature Research, R.T., S.S. and Z.H.K.; Writing Manuscript, S.S. and Z.H.K.; Critical review, S.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding. And The APC was funded by Istanbul Atlas University.

Institutional Review Board Statement

No ethical approval was required for this article, as it does not include any studies involving human participants or animals.

Data Availability Statement

The datasets generated during the current study are not publicly available due to their use in ongoing research and potential future publications but are available from the corresponding author on reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

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Table 1. Materials used in the study.
Table 1. Materials used in the study.
BrandManufacturerChemical CompositionTypeBatch Number
Filtek Universal Restorative (FU)3M, St. Paul, MN, USAAUDMA, AFM, diurethane-DMA, and 1,12-dodecane-DMA.
Filler: silica (20 nm), zirconia (4 to 11 nm), ytterbium trifluoride (100 nm)
76.5% by weight, 58.4% by volume		Nanofilled resin compositeNF18742
Tetric CAD (TET)Ivoclar
Vivadent AG, Schaan,
Liechtenstein		Bis-EMA, Bis-GMA, TEGDMA, UDMA.
Filler: barium aluminum silicate glass (<1 μm), SiO2 (<20 nm), 71% by weight		Resin composite blockX44070
Vita Enamic (VE)Vita
Zahnfabrik H. Rauter, Bad Säckingen, Germany		TEGDMA, UDMA.
Filler: feldspar ceramic enriched with aluminum oxide, 86% by weight.		Polymer-infiltrated
ceramic network block		78560
IPS Empress CAD
(IPS)		Ivoclar Vivadent AG, Schaan, LiechtensteinSiO2 (60–65 %wt), Al2O3 (16–20 %wt), K2O (10–14 %wt), Na2O (3.5–6.5 %wt), other oxides (0.5–7 %wt), pigments (0.2–1 %wt)Leucite-reinforced glass-ceramicY45442
BMO Nutrition Pure Collagen PeptidesDelta Protein International, Inc., Sunflower, MS, USAHydrolyzed bovine type 1&3 22070301
Collagen Purple Kiperin Pharmaceutical and Food Industry and Trade Co., Ltd., Istanbul, TürkiyeType 1-2-3-5-10 collagen, collagen peptites, inulin fiber, sambucus extract, magnesium cirrate, egg membrane, bromelain, black cumin extract, hyaluronic acid, vitamin C, 100% natural blueberry flavor KMP2501004
Nescafé GoldNestlé Deutschland, Frankfurt, GermanyInstant coffee 30530012
AUDMA: Aromatic Urethane Dimethacrylate; AFM: Addition-Fragmentation Monomer; DMA: Dimethacrylate; Bis-EMA: Ethoxylated bisphenol A glycol Dimethacrylate; Bis-GMA: bisphenol A glycol Dimethacrylate; TEGDMA: Triethylene Glycol Dimethacrylate; UDMA: Urethane Dimethacrylate; SiO2: Silicon dioxide; Al2O3: Aluminium oxide; K2O: Potassium oxide; Na2O: Sodium oxide.
Table 2. The mean and standard deviations of ΔE00 values.
Table 2. The mean and standard deviations of ΔE00 values.
Immersion MediaMaterial1 Day6 DaysAfter Polishing
Distilled WaterFU2.03 (0.32) a, B2.65 (0.36) a, A1.76 (0.55) a, B
IPS0.99 (0.36) b, A1.33 (0.53) b, A1.01 (0.39) b, A
TET1.02 (0.21) b, A1.14 (0.33) bc, A1.04 (0.48) b, A
VE0.74 (0.22) b, A0.61 (0.19) c, A0.62 (0.26) b, A
Pure Collagen FU3.18 (0.23) a, B3.92 (0.28) a, A1.83 (0.32) a, C
Water MixIPS1.36 (0.46) c, A1.26 (0.56) c, A1.15 (0.23) bc, A
TET2.18 (0.35) b, B2.82 (0.58) b, A1.44 (0.2) ab, C
VE1.03 (0.35) c, A1.22 (0.26) c, A0.73 (0.47) c, A
Pure Collagen FU7.26 (0.49) a, B8.41 (0.74) a, A3.09 (0.64) a, C
Coffee MixIPS1.42 (0.51) d, A1.54 (0.39) c, A1.02 (0.15) c, A
TET3.88 (0.35) b, A4.2 (0.2) b, A1.94 (0.33) b, B
VE1.93 (0.19) c, A1.91 (0.36) c, A0.7 (0.32) c, B
PurpleFU6.65 (0.39) a, B8.97 (0.63) a, A3.62 (0.52) a, C
CollagenIPS1.23 (0.37) d, A1.19 (0.67) d, A1.01 (0.19) c, A
TET3.36 (0.31) b, B4 (0.33) b, A2.31 (0.34) b, C
FU; Filtek Universal Restorative, IPS; IPS Empress CAD, TET; Tetric CAD, VE; Vita Enamic. ΔE00 values of restorative materials after immersion in distilled water, pure collagen with water mixture, pure collagen with coffee mixture, and purple collagen at three time points. Different superscript upper-case letters within the same row indicate statistically significant differences among time points according to repeated-measures ANOVA (p < 0.05). Different superscript lower-case letters within the same column indicate statistically significant differences among tested materials at the same time point according to pairwise comparisons (p < 0.05).
Table 3. The mean and standard deviations of Ra values.
Table 3. The mean and standard deviations of Ra values.
Immersion MediaMaterialBaseline1 Day6 DaysAfter Polishing
Distilled WaterFU0.07 (0.01) a, B0.08 (0.01) a, AB0.09 (0.01) a, A0.06 (0.01) a, B
IPS0.04 (0.01) b, B0.05 (0.01) b, A0.07 (0.01) b, A0.04 (0.01) b, B
TET0.06 (0.01) ac, AB0.07 (0.01) ac, B0.09 (0.01) a, A0.05 (0.01) ab, C
VE0.05 (0.01) bc, B0.06 (0.01) bc, AB0.06 (0.01) b, A0.04 (0.01) b, B
Pure Collagen FU0.08 (0.01) a, B0.10 (0.02) a, A0.11 (0.01) a, A0.06 (0.01) a, C
Water MixIPS0.05 (0.01) b, B0.07 (0.02) b, A0.08 (0.01) b, A0.03 (0.01) b, C
TET0.07 (0.01) ac, C0.09 (0.01) a, B0.11 (0.01) a, A0.05 (0.01) a, D
VE0.06 (0.01) bc, B0.07 (0.01) b, AB0.08 (0.01) b, A0.05 (0.01) a, B
Pure Collagen FU0.07 (0.01) a, C0.09 (0.01) b, B0.12 (0.01) a, A0.06 (0.01) a, C
Coffee MixIPS0.05 (0.01) b, B0.07 (0.01) c, A0.10 (0.01) b, A0.04 (0.01) b, B
TET0.08 (0.01) a, C0.11 (0.01) a, B0.13 (0.01) a, A0.05 (0.01) ab, D
VE0.04 (0.01) b, C0.07 (0.01) c, B0.09 (0.01) c, A0.05 (0.01) ab, C
PurpleFU0.08 (0.01) a, C0.10 (0.02) a, B0.12 (0.01) a, A0.06 (0.01) a, D
CollagenIPS0.04 (0.01) b, C0.08 (0.01) b, B0.10 (0.01) b, A0.04 (0.01) ab, D
TET0.07 (0.01) a, C0.11 (0.02) a, B0.13 (0.01) a, A0.06 (0.01) a, C
VE0.05 (0.01) b, C0.07 (0.01) b, B0.09 (0.01) b, A0.05 (0.01) a, C
FU; Filtek Universal Restorative, IPS; IPS Empress CAD, TET; Tetric CAD, VE; Vita Enamic. Ra values of restorative materials after immersion in distilled water, pure collagen with water mixture, pure collagen with coffee mixture, and purple collagen at four time points. Different superscript upper-case letters within the same row indicate statistically significant differences among time points according to repeated-measures ANOVA (p < 0.05). Different superscript lower-case letters within the same column indicate statistically significant differences among tested materials at the same time point according to pairwise comparisons (p < 0.05).
Table 4. The mean and standard deviations of glossmeter values.
Table 4. The mean and standard deviations of glossmeter values.
Immersion MediaMaterialBaseline1 Day6 DaysAfter Polishing
Distilled WaterFU71 (0.9) c, A66.9 (0.6) d, B63.4 (0.8) d, C68.3 (0.8) d, B
IPS77 (0.8) b, A76.2 (0.5) b, A75.8 (0.5) b, A76.7 (0.4) b, A
TET79.5 (1) a, A79 (1) a, AB77.6 (1.3) a, B79.5 (0.7) a, A
VE75.5 (0.9) b, A73.5 (0.9) c, B71.2 (1) c, C74.4 (0.8) c, AB
Pure Collagen FU70.8 (0.9) c, A67.9 (0.8) c, B65.2 (1.8) c, C69 (1.1) c, B
Water MixIPS72.8 (1) b, A72.8 (1.1) b, A71.8 (0.7) b, A72.5 (0.6) b, A
TET86 (1.1) a, A82.8 (1.9) a, B76.8 (1.1) a, D80.6 (0.8) a, C
VE69.8 (0.7) c, A67.5 (0.8) c, B64.8 (1) c, C69.2 (0.9) c, A
Pure Collagen FU70.2 (1.4) c, A65.8 (1.6) b, C59 (1.2) c, D68.1 (1.4) c, B
Coffee MixIPS76.2 (1) b, A74.7 (0.4) a, A72.3 (1.1) a, B75.7 (1) b, A
TET82.4 (1.1) a, A75.1 (2) a, C68.7 (1.2) b, D78.6 (1.1) a, B
VE66.9 (0.7) d, A63.3 (1.1) c, B59.9 (1.1) c, C66.2 (1.1) d, A
PurpleFU70.1 (0.8) d, A63.5 (1.9) d, C58.1 (1.4) d, D68.4 (1) d, B
CollagenIPS75.2 (0.9) a, A74 (0.8) a, AB72.8 (1) a, B74.9 (0.6) a, A
TET72 (0.6) b, A67.5 (0.8) c, B59.9 (0.8) c, C70.2 (0.4) c, D
VE73.7 (0.9) c, A71.7 (1.2) a, B68.5 (1.2) b, C72.3 (0.9) b, AB
FU; Filtek Universal Restorative, IPS; IPS Empress CAD, TET; Tetric CAD, VE; Vita Enamic. Glossmeter values of restorative materials after immersion in distilled water, pure collagen with water mixture, pure collagen with coffee mixture, and purple collagen at four time points. Different superscript upper-case letters within the same row indicate statistically significant differences among time points according to repeated-measures ANOVA (p < 0.05). Different superscript lower-case letters within the same column indicate statistically significant differences among tested materials at the same time point according to pairwise comparisons (p < 0.05).
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Keles, Z.H.; Turunc, R.; Sismanoglu, S. Impact of Collagen Peptide Supplements Dissolved in Different Beverages on the Surface Properties of Dental Restorative Materials. Appl. Sci. 2026, 16, 2581. https://doi.org/10.3390/app16052581

AMA Style

Keles ZH, Turunc R, Sismanoglu S. Impact of Collagen Peptide Supplements Dissolved in Different Beverages on the Surface Properties of Dental Restorative Materials. Applied Sciences. 2026; 16(5):2581. https://doi.org/10.3390/app16052581

Chicago/Turabian Style

Keles, Zeynep Hale, Rana Turunc, and Soner Sismanoglu. 2026. "Impact of Collagen Peptide Supplements Dissolved in Different Beverages on the Surface Properties of Dental Restorative Materials" Applied Sciences 16, no. 5: 2581. https://doi.org/10.3390/app16052581

APA Style

Keles, Z. H., Turunc, R., & Sismanoglu, S. (2026). Impact of Collagen Peptide Supplements Dissolved in Different Beverages on the Surface Properties of Dental Restorative Materials. Applied Sciences, 16(5), 2581. https://doi.org/10.3390/app16052581

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