1 Volume 24 2025 e256503 Original Research Braz J Oral Sci. 2025;24:e256503http://dx.doi.org/10.20396/bjos.v24i00.8676503 1 Department of Dental Materials and Prosthesis, Ribeirão Preto School of Dentistry, São Paulo University, Ribeirão Preto, São Paulo, Brazil. 2 Department of Chemistry of the Faculty of Philosophy, Sciences and Letters, University of São Paulo, Ribeirão Preto, São Paulo, Brazil. Corresponding author: Cláudia Helena Silva-Lovato Adress: Café Avenue, w/n; Zip Code: 14040–904, Ribeirão Preto - São Paulo, Brazil. Department of Dental Materials and Prosthesis, Ribeirão Preto School of Dentistry, São Paulo University, Ribeirão Preto, São Paulo, Brazil E-mail: chl@forp.usp.br; +551633154006 Editor: Dr. Altair A. Del Bel Cury Received: May 03, 2024 Accepted: March 05, 2025 Effect of different pigmentations, hygiene protocols, and time on maxillofacial silicone properties Carla Maria de Almeida Prado Magdalena1 , Arthur Augusto Martins e Silva1 , Priscila Lai Liu1 , Ana Paula Macedo1 , Grégoire Jean-Francois Demets2 , Cláudia Helena Silva-Lovato1* Objective: To evaluate the effects of pigmentation, hygiene protocols, and time on the physical, mechanical, and chemical properties, as well as the thermal behavior of MDX4-4210 and Silpuran 2420 silicones. Methods: Samples without pigmentation (WP;n=45), with intrinsic pigmentation (IP;n=45), and with intrinsic and extrinsic pigmentation (IEP;n=45) were tested. Samples were washed daily with neutral soap and immersed in water (control - C), washed daily with neutral soap and immersed in 2% hydrogen peroxide (HP2%), or washed daily with neutral soap and immersed in 0.15% triclosan (T0.15%) once a week for six months (T1). Subsequently, they were exposed to ultraviolet radiation and humidity, simulating 12 months (T2). Color, Shore A hardness, surface roughness, chemical properties, and thermal behavior were evaluated at T0, T1, and T2. Data were analyzed using a general linear model employing the Wald test and repeated measures for color and hardness changes, and ANOVA with Tukey’s post hoc test for surface roughness (α=0.05). Results: In MDX4-4210, WP and IEP had the greatest color change at T2 with T0.15% (p=0.020). IEP showed higher roughness at T1 and T2 but lower hardness variation (p<0.001). Hygiene protocols influenced roughness and hardness (p<0.05). In Silpuran, IEP had the highest color variation at T2, with reduced roughness and hardness, regardless of hygiene (p<0.001). Conclusion: IEP impacted color stability over time in both silicones when exposed to HP2% and T0.15%. Hardness changes did not compromise material quality. IEP groups showed lower roughness variation. Chemical and thermal behavior were unaffected by pigmentation or hygiene. Keywords: Maxillofacial prosthesis. Silicones. Disinfection. Surface properties. https://orcid.org/0000-0003-3010-0785 https://orcid.org/0000-0003-2334-2989 https://orcid.org/0000-0002-4037-8548 https://orcid.org/0000-0002-1064-3523 https://orcid.org/0000-0001-7152-1266 https://orcid.org/0000-0003-1629-2207 2 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 Introduction Prosthetic rehabilitation is a viable option when facial deformities cannot be surgi- cally corrected. Medical silicones are commonly used in the fabrication of maxillo- facial prostheses due to their comfort and favorable properties, such as hardness, roughness, tensile strength, and tear resistance1-6. However, alterations in these prop- erties can shorten the prosthesis lifespan and increase treatment costs, especially in countries where medical silicone is not readily available. Therefore, further studies are needed to evaluate alternative, cost-effective materials with desirable properties. Several factors can alter the properties of silicone, including processing techniques, variations in light and ambient humidity, atmospheric pollution, body fluids, hygiene methods1,3,7-21, and the addition of pigments5,7,22. Among these, hygiene methods and pigmentation can be controlled. Regarding pigmentation, adding pigments to the sili- cone base paste before mixing it with the catalyst is necessary to achieve an aesthetic skin color match, as silicone is naturally colorless. This process is known as intrinsic pigmentation. Additionally, to obtain realistic features with different tones and shades, extrinsic pigmentation is applied to the prosthesis surface after the polymerization process2,3,7,11,13. This can be done using ceramic pigments, silicone-based pigments, makeup powder, and oxides. Therefore, selecting a pigment compatible with silicone and using the appropriate dosage is essential2,7,9,13. Regarding hygiene methods for cleaning all surfaces of silicone facial prostheses, the literature describes various approaches, including brushing, microwaves, ultraviolet C light, and chemical agents such as chlorhexidine, natural extracts, peroxides, sodium hypochlorite, soap, and probiotics with anti-biofilm properties1,3,10,13-16,18-21. However, there is no consensus on a precise and safe hygiene protocol for cleaning and dis- infecting silicone prostheses. Hydrogen peroxide23,24 and triclosan25-27 solutions have demonstrated good efficacy in biofilm control. Diluted hydrogen peroxide can be an option for cleaning prostheses and tissues23, as it promotes oxygen release, loosening debris and removing light stains26. Additionally, it produces free hydroxyl radicals that cause oxidation of DNA, proteins, and lipids in vivo24. Triclosan at 0.15% reduced the microbial load and promoted the remission of denture stomatitis25,26. It disrupts the lipid bilayer membrane, affecting RNA and protein synthe- sis, ultimately leading to cell death27. Triclosan is a broad-spectrum antibacterial agent effective against Gram-positive bacteria (Bacillus subtilis, Mycobacterium smegmatis, Staphylococcus aureus), Gram-negative bacteria (Escherichia coli, Salmonella typh- imurium, Shigella flexneri), as well as fungi and yeasts28. However, concerns have been raised regarding its potential toxicity. According to Dann and Hontela29 (2011), triclosan may exhibit toxic effects at concentrations above 0.3%, potentially affecting endocrine function and environmental safety. In Brazil, its use is regulated by the National Health Surveillance Agency (Anvisa) through Resolution RDC No. 29, of June 1, 2012, which establishes a maximum allowed concentration of 0.3% in formulations30, aligning with international safety standards. Both hydrogen peroxide and triclosan are widely avail- able and cost-effective. If proven safe for use with silicone, they could be recommended as hygiene methods for maxillofacial prostheses. 3 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 This in vitro study evaluated the color change, Shore A hardness, surface roughness, and microstructural properties of two medical silicones, considering the effects of pigmentation, hygiene protocols, and time. The evaluation was conducted after six months of natural aging and 12 months of accelerated aging. The tested hypothesis was that these factors would not significantly affect the materials’ properties. This study addresses this gap, providing valuable insights to enhance the longevity and aesthetics of maxillofacial prostheses. Materials and Methods The materials used in this study are listed in Table 1. A total of 135 disk-shaped spec- imens (3 mm thick × 12 mm in diameter) were distributed into three groups: WP (col- orless), IP (intrinsic pigmentation), and IEP (intrinsic + extrinsic pigmentation). The sample size was determined based on previous studies2-6,8,9,13,18,22. MDX4-4210 silicone was prepared at a 10:1 ratio (base:catalyst), while Silpuran 2420 was mixed in a 1:1 ratio (base:catalyst), following the manufacturers’ recommendations. Table 1. Materials used in the study. Material Trademark Silastic® MDX4-4210 BioMedical Grade Elastomer, Dow-Corning, USA Silpuran 2420 Wacker Chemie AG, München Silc Pig® (Beige – PMS 488C) Smooth-On, Inc., Macungie, Pennsylvania, USA Silc Pig® (Blood – PMS 7421C) Smooth-On, Inc., Macungie, Pennsylvania, USA Pre-painting fluid Smooth-On, Inc., Macungie, Pennsylvania, USA Psycho Paint Smooth-On, Inc., Macungie, Pennsylvania, USA Solvent for psycho paint D-Limonene, Dim Clay, São Paulo, São Paulo, Brasil Neutral soap Pleasant, Perol Commercial and Industrial Ltd., São Paulo, São Paulo, Brasil. Hydrogen peroxide at 2% Daterra Manipulation Pharmacy, Ribeirão Preto, São Paulo, Brasil Triclosan solution at 0,15% Mix das essências, Belo Horizonte, MG, Brasil. Solution prepared in Laboratory of Research in Oral Rehabilitation of School of Dentistry of Ribeirão Preto (100 mL of the sodium hydroxide, 0,056 M + 0.15 g Triclosan + water q.s.p = final concentration of the 0.15% For the WP group, the base and catalyst pastes were weighed on a digital balance and mixed under vacuum (Turbomix, EDG, São Bernardo do Campo, São Paulo, Bra- zil) for 120 seconds2,3. The mixture was then inserted into rectangular Teflon molds (12 mm long × 4 mm wide × 3 mm deep) and placed in a pneumatic press at 20 psi for 15 minutes to eliminate bubbles. Next, the set was placed in a polymerization oven (Odontobras Ind. and Trade Equip. Med. Odont. Ltda, Ribeirão Preto, São Paulo, Brazil) at 100°C for 60 minutes. After polymerization, the silicone sheets were cut into 12 mm diameter disks using circular sharp cutters2,3. The final dimensions were verified with a digital caliper (CD-6 CSX-B, Mitutoyo Ltda, Suzano, São Paulo, Brazil). 4 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 For the IP group, the beige pigment was weighed and incorporated into the sili- cone base paste at a 2% ratio2-4,6. The catalyst was then added, and the mixture was homogenized under vacuum for 120 seconds. The subsequent steps followed the same protocol as described for the WP group. After polymerization, half of the samples underwent extrinsic pigmentation, forming the IEP group. The specimen surfaces were pre-treated with a pre-painting fluid. A total of 0.02 g of blood-colored pigment was mixed with 2 g of Psycho-Paint A, followed by the addition of 2 g of Psycho-Paint B. To obtain a thin and uniform pigment layer, the mixture was diluted in an equal volume of Psycho-Paint solvent (2 parts), and 2 g of the final solution was applied to the specimen surfaces using a dry brush. For polymerization of the extrinsic pigment, the specimens were kept at room temperature for 24 hours. All specimens were individually numbered and stored in a closed container, protected from light10,22, until the initial measurements (T0) of color, hardness, surface roughness, and thermal analysis were performed. The specimens were randomly assigned to subgroups based on hygiene protocols, with randomization conducted using computer-generated numbers (Excel 2013, Microsoft Windows). All specimens underwent daily cleaning by being washed with one drop of neutral soap, using the index finger and thumb for 20 seconds. Additionally, once a week, they were immersed for 20 minutes in 5 mL of either water (control, C), 2% hydrogen peroxide (HP2%), or 0.15% triclosan (T0.15%), followed by rinsing under running water for 20 seconds. This protocol was maintained for six months (T1). The hygiene protocols were adapted for this study based on literature regarding den- ture hygiene25,26 and maxillofacial prosthesis care2,23. All procedures were performed by the same operator (C.M.A.P.M.) to ensure consistency and standardization. During the interval, specimens were kept near to an open glass window, exposed to envi- ronment light, temperature, and humidity until the next cleaning procedure2,22. The exper- iment took place from February to July 2023, thus encompassing the summer, autumn and winter seasons. This model has aim to simulate the use of the prosthesis during 6 months (T1). Subsequently, specimens were exposed to ultraviolet-B (UV-lamp TL 40 W/12RS B medical, Phillips, The Netherlands) for 240 hours and subjected to conden- sation at 50°C for an additional 240 hours (UV Cond, Comexim and Raw Materials Indus- try Commerce Ltda, São Paulo, Brazil), simulating 12 months of prosthesis use (T2)2. Color change1,2,5,8,10 was measured using a spectrophotometer (Color Eye 7000; Mac- beth, Newburgh, NY) following the Color System Standard Commission Internationale de L’Eclairage (CIE LAB; American Dental Association). The color change (ΔEab) was calculated using the formula: ΔEab = √(ΔL)2 + (Δa)2 + (Δb)2 Where ΔL represents the variation in luminance (brightness), Δa indicates the varia- tion in the red (+) or green (-) intensity, and Δb represents the variation in yellow (+) or blue (-) intensity. To classify the color change, the National Bureau of Standards (NBS) was applied using the formula: NBS = ΔEab × 0.92 The color change was categorized as: very light (0.0-0.5), light (0.5-1.5), remarkable (1.5-3.0), appreciable (3.0-6.0), high (6.0-12.0), and very high (>12.0). 5 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 Shore A hardness analysis was conducted in accordance with ASTM D 2240-64 stan- dards and previous studies2,4. A Shore A Durometer (Nishi Tokyo Seimitsu Co Ltd, Tokyo, Japan) was used with a 1 kg load applied for 5 seconds. The test specimen was visually divided into four quadrants, with measurements taken at the center of each quadrant and an additional measurement at the center of the specimen to obtain the mean value. To comply with ASTM D 2240-64 standards and perform indentations on 6 mm specimens, two specimens were stacked. In the sequence, surface roughness2,4,5 was measured with a rugosimeter (Rug 0.3; Prazis, Buenos Aires, Argentina) with 0.01 μm resolution, 0.8 mm cut-off length, 4.8 mm transverse length, and 0.5 mm/sec speed. Three measurements (in the center, at 5 mm to the right, and at 5 mm to the left of the center) were performed for each specimen and the mean value was used as the roughness value (Ra; µm). Chemical property was analyzed using Fourier Transform Infrared Spectroscopy (FTIR) and the thermal comportment was analyzed by Differential Scanning Calorime- try (DSC), and Thermogravimetric Analysis (TGA)2. FTIR is a spectroscopic technique used to identify the functional groups and chemical bonds present in the material, revealing its molecular composition31. DSC analyzes thermal transitions (such as melting, crystallization, and glass transition), allowing the energetic behavior of the material during heating or cooling to be understood. TGA monitors the variation in material mass as a function of temperature, being essential for evaluating thermal stability and degradation processes32. FTIR was performed with the Nexus 4700 FTIR spectrophotometer (Thermo Nicolet, Berkeley, California, USA) and the measure- ments occurred in the region between 4000 to 400 cm-1, using 20 sweeps of the attenuated total reflection (ATR) kit. The DSC and TGA tests were performed simulta- neously (SDT 600, TA Instruments, Newcastle, England), and the thermogravimetric curves were obtained in a DTA/TGA/DSC thermal analysis system (TA Instruments Q-600 - Simultaneous). The specimens of 4 mg were heated from room temperature (23°C) to 550°C in a synthetic air atmosphere. After reaching 550ºC, an oxygen atmo- sphere was used, with an average flow of 50 mL / minute-1 up to 900ºC. Measurements of the color, Shore A hardness, surface roughness, chemical proper- ties, and thermal comportment were obtained before hygiene protocols exposition (T0), after 6 months of hygiene protocols (T1), and after the accelerated aging (T2). Normality (Shapiro-Wilk test) and homoscedasticity (Levene) tests were performed. Color change and Shore A hardness data met the assumptions of normal distribution. These dependent variables were analyzed by the General Linear Model (GLM) with repeated measures and Wald post-hoc test. Roughness data did not present a nor- mal distribution, so data were analyzed by ANOVA with repeated measures and Tukey post-hoc test. A 95% confidence interval was considered. For each material, the inde- pendent variables included pigmentation (WP, IP, and IEP), hygiene protocols (control, HP2%, and T0.15%), and time (T0, T1, and T2). The time influence was analyzed by variation (D) between T1-T0 (DT1) and T2-T0 (DT2) for all dependent variables. The analyses were conducted using SPSS software (version 21, IBM Corp) by a blinded researcher (C.H.L.S). The results of the chemical and thermal analyses are presented in tables and figures and were interpreted and discussed. 6 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 Results The environmental conditions for time T1 are in Figure 1. Color change (MDX4-4210: p=0.020; Silpuran 2420: p<0.001), shore A hardness (MDX4-4210: p<0.001; Silpuran 2420: p<0.001), and roughness (MDX4-4210: p<0.001; Silpuran 2420: p<0.001) were influenced by interaction of factors (Table 2). For MDX4-4210/IEP/T0.15% exhibited the highest color change, while the IP/T0.15% group showed small variations. Silpuran 2420/IEP/T0.15% exhibited the greatest color change at ΔT2. The NBS values are showed in Figure 2. Figure 1. Environment conditions during first experimental period. Table 2. Comparison [means (standard deviation)] of the interaction Pigmentation × Hygiene protocols × time on color change, hardness and surface roughness (µm). MDX4-2410 P* Silpuran2420 P* ΔT1 ΔT2 ΔT1 ΔT2 Co lo r c ha ng e WP C 1.69 (0.56) 2.56 (0.87) 0.02 3.93 (0.89) 1.90 (0.75) <0,00 aBβ bBα aAα bBβ HP2% 1.45 (0.49) 3.55 (1.00) 2.91 (0.70) 2.25 (0.52) aBβ bBα aBα bBβ T0.15% 3.36 (1.33) 18.98 (2.78) 4.01 (1.19) 3.67 (1.01) aAβ aAα aAα bAα IP C 1.46 (0.34) 1.80 (0.36) 1.91 (0.56) 1.89 (0.59) abAα bAα bAα bAα HP2% 1.30 (0.29) 1.89 (0.68) 0.82 (0.48) 0.87 (0.50) aAα cAα bBα bAα T0.15% 1.40 (0.45) 1.70 (0.64) 1.40 (0.48) 1.00 (0.55) cAα cAα bABα cAα IEP C 0.88 (0.62) 17.82 (1.76) 1.34 (0.84) 9.61 (1.12) bBβ aABα bAβ aAα HP2% 1.46 (1.73) 18.21 (2.36) 1.64 (2.06) 10.8 (2.86) aBβ aAα bAβ aAα T0.15% 8.59 (0.34) 16.72 (1.19) 1.41 (0.66) 9.64 (2.08) bAβ bBα bAβ aAα Continue 7 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 Continuation Sh or e A ha rd ne ss WP C 2.32 (0.74) 2.01 (0.86) <0,00 2.48 (0.43) 1.56 (0.46) <0,00 cBα cCβ aAα aAβ HP2% 3.01 (0.51) 3.06 (0.63) 2.03 (0.44) 1.28 (0.48) aAα aBα aAα aAβ T0.15% 3.36 (0.60) 3.78 (0.57) 2.08 (0.55) 1.45 (0.59) aAβ aAα aAα aAβ IP C 3.61 (0.33) 3.71 (0.28) 1.28 (0.65) 0.78 (0.68) aAα aAα bBα bBβ HP2% 3.05 (0.60) 3.08 (0.62) 2.00 (0.60) 1.25 (0.45) aBα aBα aAα aAβ T0.15% 2.73 (0.50) 2.05 (0.49) 1.81 (0.43) 1.28 (0.33) bBα bCβ abAα aAβ IEP C 2.91 (0.57) 2.58 (0.56) 1.73 (0.47) 0.38 (0.36) bAα bAβ bAα bAβ HP2% 2.30 (0.38) 1.91 (0.44) 1.25 (0.46) 0.68 (0.41) bBα bBβ bBα bAβ T0.15% 2.11 (0.33) 0.66 (0.26) 1.36 (0.55) 0.73 (0.47) cBα cCβ bABα bAβ Su rf ac e ro ug hn es s WP C 0.43 (0.14) 0.51 (0.12) <0.001 0.56 (0.11) 0.82 (0.12) <0,001 cAβ bAα cAβ aAα HP2% 0.38 (0.09) 0.46 (0.08) 0.49 (0.15) 0.74 (0.08) cAβ bAα bABβ bAα T0.15% 0.37 (0.10) 0.44 (0.08) 0.42 (0.09) 0.61 (0.09) cAβ bAα bBβ bBα IP C 0.58 (0.08) 1.05 (0.20) 0.97 (0.12) 0.89 (0.08) bAβ aAα aAa aBβ HP2% 0.52 (0.09) 0.50 (0.11) 0.86 (0.12) 1.00 (0.07) bAα bBα aABβ aAα T0.15% 0.53 (0.19) 0.41 (0.06) 0.70 (0.07) 0.89 (0.08) bAα bBβ aBβ aBα IEP C 1.23 (0.15) 1.06 (0.07) 0.85 (0.14) 0.65 (0.07) aAα aAβ bAα bAβ HP2% 1.24 (0.14) 0.97 (0.09) 0.85 (0.08) 0.59 (0.07) aAα aABβ aAα cAβ T0.15% 1.17 (0.11) 0.91 (0.08) 0.77 (0.13) 0.57 (0.10) aAα aBβ aAα bAβ * Surface roughness: ANOVA with Tukey’s post-hoc (Bonferroni-adjusted); Color change and Shore A hardness: Wald test (generalized linear model, Bonferroni-adjusted); Small letters: compare pigmentations for the same time and hygiene protocol; Capital letters: compare protocols for the same time and pigmentation; Greek letters compare time for the same protocol and pigmentation; Equal letters: indicate statistical similarity. WP: silicone colorless; IP: silicone with intrinsic pigment; IEP: silicone with intrinsic +extrinsic pigment; C: control - washing and immersion in water; HP2%: washing and immersion in hydrogen peroxide at 2%; T0.15%: washing and immersion in triclosan at 0.15%; ΔT1: variation between T1-T0; ΔT2: variation between T2-T0. 8 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 0.0-0.5: very light; 0.5-1.5: light; 1.5-3.0: remarkable; 6.0-12.0: high; >12.0: very high Figure 2. NBS values and color change classification. MDX4-4210 is a material with higher average hardness values than Silpuran (Table 3). Analyzing the variations of each material (Table 2), MDX4-4210/C/WP and IP were more stability over time; IEP/T0.15% had pronounced changes, with hardness increasing over time. For Silpuran 2420, hardness variation was smallest with WP/HP2%. The C proto- col caused greater variation. Surface roughness was most affected in the IEP/T0.15%, while WP/C presents the least surface roughness for both materials (Table 2). Table 3. Means [standard deviation (SD)] of the Shore A hardness. MDX4-4210 Silpuran T0 T1 T2 T0 T1 T2 WP C Mean 35.25 37.58 37.27 10.98 13.47 12.55 SD 0.58 0.43 0.46 0.38 0.21 0.29 HP2% Mean 34.72 37.73 37.78 11.20 13.23 12.48 SD 0.56 0.38 0.36 0.41 0.37 0.27 T0.15% Mean 34.72 38.08 38.50 11.37 13.45 12.82 SD 0.38 0.44 0.46 0.48 0.25 0.32 IP C Mean 34.92 38.53 38.63 9.87 11.15 10.65 SD 0.35 0.16 0.41 0.65 0.40 0.23 HP2% Mean 35.22 38.28 38.30 9.80 11.80 11.05 SD 0.57 0.27 0.45 0.58 0.39 0.29 T0.15% Mean 35.35 38.08 37.40 9.93 11.75 11.22 SD 0.52 0.26 0.70 0.35 0.46 0.19 IEP C Mean 32.92 35.83 35.50 10.62 12.35 11.00 SD 0.60 0.39 0.35 0.33 0.48 0.23 HP2% Mean 33.47 35.77 35.38 10.57 11.82 11.25 SD 0.31 0.26 0.36 0.35 0.35 0.30 T0.15% Mean 33.70 35.82 34.37 10.63 12.00 11.37 SD 0.34 0.29 0.39 0.36 0.38 0.19 WP: silicone colorless; IP: silicone with intrinsic pigment; IEP: silicone with intrinsic +extrinsic pigment; C: control - washing and immersion in water; HP2%: washing and immersion in hydrogen peroxide at 2%; T0.15%: washing and immersion in triclosan at 0.15%. 9 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 The decomposition processes initiating around 347–361°C (dt1) for MDX4-4210 and 329–336°C (dt1) for Silpuran 2420. MDX4-4210 showed increasing stability over time, with final decomposition temperatures (dt5) in the WP group rising from 563°C (T0) to 651°C (T2). Similarly, the IEP group exhibited enhanced stability, with dt5 increasing from 576°C (T0) to 603°C (T2). For Silpuran 2420, the WP group demonstrated a slight increase in stability, with dt5 rising from 534°C (T0) to 549°C (T2). The IP and IEP groups showed comparable trends, with final decomposition temperatures at T2 reaching 549°C and 548°C, respectively. Thermogravimetric analyses (TGA) indicated progressive increases in stability. For MDX4-4210, the WP group’s primary decomposition point (tg5) increased from 533°C (T0) to 543°C (T2). The IEP group also showed growth, with tg5 rising from 540°C (T0) to 553°C (T2). Silpuran 2420 displayed smaller increases in tg5 across groups, with values reach- ing 522°C (WP), 522°C (IP), and 518°C (IEP) at T2. Decomposition curves revealed processes beginning near 300°C and extending to approximately 550°C. Both sil- icones left residues (35–57% of mass) composed primarily of SiO2 and SiC. The main exothermic DSC peak corresponded to silicone polymerization, with minor peaks indicating secondary processes, including siloxane hydrolysis. Pigmentation not influenced in this comportment (WP = 562°C; IP = 563°C; IEP = 566°C). Time did not influence stability until T2, where samples exhibited slightly higher stability (582°C) (Table 4). FTIR (Figure 3) confirmed these findings, with preserved Si-O-Si stretching peaks at 1082 cm-1 and 707 cm-1, as well as Si-CH3 and CH2-stretch modes around 1260 cm-1 and 2970 cm-1. The spectra revealed that pigmentation and time had minimal impact on polymer structures, maintaining relative peak intensities in all groups. Figure 3. Fourier Transform Infrared Spectroscopy (FTIR) curves of hygiene protocols and pigmentation groups. 10 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 Table 4. Temperatures of the thermoanalytical curves of the Differential Scanning Calorimetry (DSC) and Thermogravimetry (TGA) tests of the silicone MDX4-4210 and Silpuran 2420 of the colorless (WP), with intrinsic pigmentation (IP), and with intrinsic+extrinsic pigmentation (IEP) at the T0, T1 and T2 times. Groups Times Points of the DSC curves Points of the TGA curves dt1 dt2 dt3 dt4 dt5 dt6 tg1 tg2 tg3 tg4 tg5 M DX 4- 42 10 WP T0 347 434 484 537 563 635 367 432 458 481 533 T1 358 412 438 463 568 637 372 407 436 497 529 T2 351 439 482 574 651 * 369 425 447 466 543 IP T0 354 * 441 502 585 638 378 438 * 489 553 T1 354 431 448 490 574 651 372 413 430 497 574 T2 354 435 471 575 615 661 381 433 452 470 570 IEP T0 361 427 446 547 576 645 374 422 451 491 540 T1 358 433 473 564 579 628 379 431 460 498 529 T2 353 446 474 576 603 * 377 426 456 473 553 Si lp ur an 2 42 0 WP T0 330 413 436 486 534 649 355 409 434 485 508 T1 336 426 445 491 524 638 360 416 441 466 494 T2 329 423 438 474 534 642 354 422 439 475 504 IP T0 332 417 441 483 523 611 360 398 413 440 455 T1 336 427 452 504 536 625 360 413 451 488 525 T2 335 416 441 494 549 643 362 413 441 491 522 IEP T0 335 420 459 501 548 654 358 388 454 492 518 T1 334 413 447 477 548 637 359 411 445 485 522 T2 335 415 442 495 544 637 360 417 443 494 516 *Absent Discussion The null hypothesis was rejected. For both silicones, the IP promoted greater color stability over time, suggesting that pigment incorporation was favorable. In general, there was color change for the WP group with T0.15%, and for the IEP group at T1 and T24,9,10,12,19. According to the NBS scale, WP and IEP groups of both silicones showed clinically unacceptable color changes when exposed to T0.15% at T1 and T2, regard- less of the hygiene protocol. The IP groups of both silicones showed values within the clinically acceptable range, regardless of time and hygiene protocol. The results are promising, as 2% hydrogen peroxide and 0.15% triclosan has good antimicrobial action24,27 and are easy to access. Color degradation for the colorless group indicates that color instability is inherent to the material7,8. On the other hand, the color degrada- tion of the IEP specimens may be related to substances absorption, degradation reac- tions such as hydrolysis, and thermal and humidity changes of the extrinsic pigment10 11 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 as well as modification or removal of the external pigment layer caused by hygiene protocols over the months. Due to average hardness values, MDX4-4210 can be classified as soft silicone and Silpuran 2420 as extra soft33. The literature is controversial regarding the ideal Shore A hardness of silicone for facial prostheses. For some authors, hardness values should be between 25 and 35 units1,2. However, the choice of a material with higher or lower hardness depends on the clinical condition of the organ to be rehabilitated and its tissue characteristics1,7,18,19. The increase in the hardness can promote a negative effect on patient acceptance due to misfit of the edges1. The maximum change in hardness of the materials studied was 3.78 points, and considering the initial values, this change would hardly affect the quality of the prosthesis. Both sil- icones with IEP showed shore A hardness changes smaller than or equal to the IP group, corroborating with the literature19. However, other studies show that extrinsic pigmentation promoted a greater change in hardness when compared to intrinsic pigmentation and colorless silicone5,9. Although the authors justify this result as consequence of double polymerization, the use of the make-up powder and not a pigment suitable for silicone can had influenced. The HP2% and T0.15% promoted similar or lower hardness values than control group, independent of pigmentation. This can be considered a good result. It is important to mention that triclosan was banned from soap products (liquid, gel, foam, bar) by the U.S. Food and Drug Administration in 2016 and from all human hygiene biocidal products by the European Union in 2017, due to the detection of triclosan in skin, urine, and plasma after mucosal contact, raising concerns about its potential toxicity and harmful effects on both the population and the environment34. However, there is a lack of mechanism-based human studies in terms of both num- ber and scope35. Most cohort and in vitro studies have predominantly assessed the toxic effects of triclosan exposure without an in-depth analysis of its specific mech- anisms of action and cellular targets. The literature emphasized the need for further investigation into the biological effects of triclosan exposure at the metabolic level in vivo. Furthermore, evaluation of the DNA damage, cytokinetic defects, prolifera- tive potential, and cell death caused by mouthrinses (chlorhexidine, triclosan, and essential oils in ethanolic solution) didn’t show evidence of genotoxic effects from the analyzed mouthrinses36. In this study, triclosan was tested at a concentration of 0.15% and was also recommended for denture immersion, as this method avoids direct mucosal contact, minimizing the risk of toxicity. Pigmentation and time might influence silicone surface roughness. The smallest variation occurred with colorless silicones7,19, however, this group showed a greater change in roughness in T2 when compared with T17,14,19,20. In regard to hygiene solutions, the literature presents different options2,6,13,15,19,21,26, but the majority of the studies evaluated antimicrobial action without analyzing the effect on material properties, specifically surface roughness, which is related to biofilm adhesion19,20. Our results indicate that there was an increase in roughness after hygiene protocols and that the use of neutral soap resulted in less variation for both materials in the colorless form20. 12 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 Infrared vibrational spectrometry showed that the vibrational peaks remained preserved for both materials. Similar chemical groups were identified among the samples, regardless of pigmentation and time, indicating that the addition of pigments did not interfere in the polymerization process and composition of the samples4. Thermal analysis corroborates with the vibrational spectroscopy, which indicates that the variation factors applied to the materials did not result in struc- tural alterations. Both materials started the continuous decomposition process at around 300°C, generating a loss of 35% to 57% mass of silicon dioxide (SiO2) and silicon carbide (SiC) residue. This can be explained by the difference in pro- portions in quantity of carbon and oxygen in the composition of the two types of silicone. It is also noted that the initial mass loss is not perfectly monotonic, and there is the presence of minor oxidative processes, suggesting that presence of occluded oxygen in the specimens in bubble form. The mass loss in an anoxic atmosphere was consistent with the release of siloxane hydrolysis products with the formation of water and carbon dioxide. The main exothermic peak, around 500ºC, corresponded to the degradation processes of the two types of silicone and, when comparing all the specimens, the variation in temperatures was very small, with the values of MDX4-4210 around 10% higher compared to those of Silpuran 2420, suggesting similarity between them. However, it should be noted that the temperatures required for the degradation of both types of silicone were much higher than those experienced in everyday life. This variation in values does not seem to be related to the presence of pigment, suggesting that there was inte- gration of the pigments added to the silicone. One limitation of this study is the artificial aging process used, which differs from natural aging. Due to time constraints, a 12-month consecutive material analysis was not feasible, so accelerated aging was necessary to simulate long-term con- ditions. Additionally, the absence of previous studies on Silpuran 2420 limits the ability to directly compare the results. However, this also highlights the innovative nature of the findings. Future studies could be analyzing other properties of the materials, such as tensile strength, tear strength, and sorption and solubility. Fur- thermore, surface analysis using confocal microscopy, extended aging times, and studies evaluating the behavior of Silpuran 2420 regarding biofilm adhesion and antimicrobial response under various hygiene protocols are necessary. Moreover, analyses to identify whether residues of the solutions remain on the prostheses after washing are important to eliminate possible adverse effects. This study demonstrated that intrinsic+extrinsec pigmentation impacted color stability over time in both MDX4-4210 and Silpuran 2420, with notable variations, particularly when exposed to HP2% and T0.15%. Changes in hardness did not com- promise the quality of the materials. Chemical and thermal comportment was not affected by pigmentation or hygiene protocols. IEP silicones showed lower varia- tion in surface roughness, suggesting greater resistance to surface wear, but still exhibited increases in roughness with prolonged exposure to hygiene protocols. Conflict of interests The authors affirm that they have no conflicts of interest to declare. 13 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 Data Availability Datasets related to this article can be found at: https://www.teses.usp.br/teses/dis- poniveis/58/58131/tde-23102023-145726/pt-br.php. Hosted at: https://www.teses.usp.br/ Acknowledgements This study was supported by the Coordination for the Improvement of Higher Educa- tion Personnel (CAPES) – Finance Code 001. Author Contribution Carla Maria de Almeida Prado Magdalena: Data curation, Investigation, Methodol- ogy, Writing – original draft. Arthur Augusto Martins e Silva: Writing – original draft, Writing – review & editing. Priscila Lai Liu: Methodology, Writing – original draft. Ana Paula Macedo: Data curation, Formal Analysis, Methodology, Writing – original draft. Grégoire Jean Francois Demets: Formal Analysis, Methodology, Writing – original draft. Cláudia Helena Silva-Lovato: Conceptualization, Data curation, Formal Anal- ysis, Funding acquisition, Methodology, Project administration, Resources, Supervi- sion, Validation, Writing – original draft, Writing – review & editing. All authors revised and approved the final version of the manuscript. References 1. Eleni PN, Krokida MK, Polyzois GL, Gettleman L. Effect of different disinfecting procedures on the hardness and color stability of two maxillofacial elastomers over time. J Appl Oral Sci. 2013;21(3):278-83. doi: 10.1590/1679-775720130112. 2. Pinheiro JB, Reis AC, Pisani MX, Leite VMF, Souza RF, Paranhos HFO, et al. Microstructural characterization and evaluation of the properties of polymeric materials for maxillofacial prosthetics. J Med Eng Technol. 2014;38(2):67-75. doi: 10.3109/03091902.2013.864715. 3. Pinheiro JB, Vomero MP, do Nascimento C, Watanabe E, Paranhos H de FO, Coto NP, et al. Genomic identification of microbial species adhering to maxillofacial prostheses and susceptibility to different hygiene protocols. Biofouling. 2018;34(1):15-25. doi: 10.1080/08927014.2017.1403591. 4. Shihab NM, Abdul-Ameer FM. Studying some mechanical properties of maxillofacial silicone elastomer before and after incorporation of intrinsic pigments and artificial aging. Futur Dent J. 2018;4(2):244-52. doi: 10.1016/j.fdj.2018.06.002. 5. Nair A, Saratchandran S. Comparative evaluation of color stability of maxillofacial silicones following accelerated aging conditions. FACE. 2022;3(2):362-8. doi: 10.1177/27325016221101899. 6. Abdullah HA, Abdul-Ameer FM. Evaluation of some mechanical properties of a new silicone elastomer for maxillofacial prostheses after addition of intrinsic pigments. Saudi Dent J. 2018;30(4):330-6. doi: 10.1016/j.sdentj.2018.05.006. 7. Gupta P, Deshpande S, Radke U, Ughade S, Sethuraman R. The color stability of maxillofacial silicones: a systematic review and meta analysis. J Indian Prosthodont Soc. 2021;21(2):138-49. doi: 10.4103/jips.jips_253_19. 8. Hatamleh MM, Watts DC. Effect of extraoral aging conditions on color stability of maxillofacial silicone elastomer: color stability of maxillofacial silicone elastomer. J Prosthodont. 2010;19(7):536-43. doi: 10.1111/j.1532-849x.2010.00627.x. 14 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 9. Farah A, Sherriff M, Coward T. Color stability of nonpigmented and pigmented maxillofacial silicone elastomer exposed to 3 different environments. J Prosthet Dent. 2018;120(3):476-82. doi: 10.1016/j.prosdent.2017.11.016. 10. Chamaria A, Aras MA, Chitre V, Rajagopal P. Effect of chemical disinfectants on the color stability of maxillofacial silicones: An in vitro study. J Prosthodont. 2019 Feb;28(2):e869-e872. doi: 10.1111/jopr.12768. . Epub 2018 Mar 8. 11. Rahman AM, Jamayet NB, Nizami MMUI, Johari Y, Husein A, Alam MK. Effect of tropical outdoor weathering on the surface roughness and mechanical properties of maxillofacial silicones. J Prosthet Dent. 2022;127(6):937-42. doi: 10.1016/j.prosdent.2020.07.026. Epub 2021 Jan 17. 12. Guiotti AM, Cunha BG, Paulini MB, Goiato MC, dos Santos DM, Duque C, et al. Antimicrobial activity of conventional and plant-extract disinfectant solutions on microbial biofilms on a maxillofacial polymer surface. J Prosthet Dent. 2016;116(1):136-43. doi: 10.1016/j.prosdent.2015.12.014. 13. Guiotti AM, Goiato MC, dos Santos DM, Vechiato-Filho AJ, Cunha BG, Paulini MB, et al. Comparison of conventional and plant-extract disinfectant solutions on the hardness and color stability of a maxillofacial elastomer after artificial aging. J Prosthet Dent. 2016 Apr;115(4):501-8. doi: 10.1016/j.prosdent.2015.09.009. Epub 2015 Nov 19. 14. Tan Y, Leonhard M, Moser D, Schneider-Stickler B. Inhibition activity of Lactobacilli supernatant against fungal-bacterial multispecies biofilms on silicone. Microb Pathog. 2017;113:197-201. doi: 10.1016/j.micpath.2017.10.051. 15. Babu AS, Manju V, Gopal VK. Effect of chemical disinfectants and accelerated aging on maxillofacial silicone elastomers: an In vitro Study. Indian J Dent Res. 2018 Jan-Feb;29(1):67-73. doi: 10.4103/ijdr.IJDR_272_16. 16. Tetteh S, Bibb R, Martin S. Mechanical and morphological effect of plant based antimicrobial solutions on maxillofacial silicone elastomer. Materials (Basel). 2018 May;11(6):925. doi: 10.3390/ma11060925. 17. El Afandy H, Fawzy A. Evaluation of mechanical properties of maxillofacial silicone after long term exposure to different conditions. Egypt Dent J. 2019;65(3):2681-9. doi: 10.21608/edj.2019.72629. 18. Miranda NB, de Arruda JAA, de Almeida SBM, dos Santos EG, Medeiros IS, Moreno A. Optical parameters and hardness of two maxillofacial elastomers after immersion in different solutions of Brazilian green propolis extract. J Prosthet Dent. 2019 Aug;122(2):168-75. doi: 10.1016/j.prosdent.2019.01.020. 19. Sahal G, Woerdenbag HJ, Hinrichs WLJ, Visser A, Tepper PG, Quax WJ, et al. Antifungal and biofilm inhibitory effect of Cymbopogon citratus (lemongrass) essential oil on biofilm forming by Candida tropicalis isolates; an in vitro study. J Ethnopharmacol. 2020 Jan;246:112188. doi: 10.1016/j.jep.2019.112188. Epub 2019 Aug 27. 20. Choonharuangdej S, Mat-Rani S, Chotprasert N, Srimaneekarn N. Fungicidal effect of lemongrass essential oil on Candida albicans biofilm pre-established on maxillofacial silicone specimens. J Int Soc Prev Community Dent. 2021 Aug;11(5):525-30. doi: 10.4103/jispcd.jispcd_63_21. 21. Malateaux G, Salazar-Gamarra R, de Souza Silva J, Gallego Arias Pecorari V, Suffredini IB, Dib LL. Ultraviolet C as a method of disinfecting medical silicone used in facial prostheses: an in vitro study. J Prosthet Dent. 2021 Sep;126(3):452.e1-452.e6. doi: 10.1016/j.prosdent.2021.06.036. 22. Hatamleh MM, Polyzois GL, Silikas N, Watts DC. Effect of Extraoral Aging Conditions on Mechanical Properties of Maxillofacial Silicone Elastomer. J Prosthodont. 2011 Aug;20(6):439-46. doi: 10.1111/j.1532-849x.2011.00736.x. 15 Magdalena et al. Braz J Oral Sci. 2025;24:e256503 23. Goiato MC, Zucolotti BC, Mancuso DN, dos Santos DM, Pellizzer EP, Verri FR. Care and cleaning of maxillofacial prostheses. J Craniofac Surg. 2010 Jul;21(4):1270-3. doi: 10.1097/SCS.0b013e3181e1b431. 24. Linley E, Denyer SP, McDonnell G, Simons C, Maillard JY. Use of hydrogen peroxide as a biocide: new consideration of its mechanisms of biocidal action. J Antimicrob Chemother. 2012 Jul;67(7):1589-96. doi: 10.1093/jac/dks129. 25. Araujo CB, Ribeiro AB, Fortes CV, Bueno FL, De Wever B, Oliveira VC, et al. Effect of local hygiene protocols on denture-related stomatitis, biofilm, microbial load, and odor: a randomized controlled trial. J Prosthet Dent. 2022 Oct;128(4):664-73. doi: 10.1016/j.prosdent.2020.12.018. 26. Ribeiro AB, Borba Araújo C, Vieira Fortes C, Lucarini Bueno F, de Cássia Oliveira V, Macedo AP, et al. Effect of denture hygiene protocols on patient satisfaction, oral health‐related quality of life, and salivary parameters: a randomized clinical trial. J Prosthodont. 2022; Jun;31(5):e12-e19. doi: 10.1111/jopr.13494. 27. Stewart MJ, Parikh S, Xiao G, Tonge PJ, Kisker C. Structural basis and mechanism of enoyl reductase inhibition by triclosan. J Mol Biol. 1999 Jul;290(4):859-65. doi: 10.1006/jmbi.1999.2907. 28. Bhargava HN, Leonard PA. Triclosan: Applications and safety. Am. J. Infect. Control. 1996 Jun;24(3):209-18. doi: 10.1016/s0196-6553(96)90017-6. 29. Dann AB, Hontela A. Triclosan: environmental exposure, toxicity and mechanisms of action. J Appl Toxicol. 2011 May;31(4):285-311. doi: 10.1002/jat.1660. 30. Brazilian Ministry of Health, National Health Surveillance Agency. [Resolution RDC No. 29, of June 1, 2012]. Brasília, DF: ANVISA; 2012 [cited 2025 Feb 09]. Available from: https://bvsms.saude.gov.br/bvs/saudelegis/anvisa/2012/rdc0029_01_06_2012.html. Portuguese. 31. Smith BC. Fundamentals of Fourier Transform Infrared Spectroscopy. CRC Press; 2011. doi: 10.1201/b10777. 32. Di Maio L. Thermal analysis of polymers: fundamentals and applications. Weinheim: Wiley-VCH; 2002. 33. Caetano MJL. Dureza. [cited 2022 May 12]. Available from: https://www.ctborracha.com/borracha- sintese-historica/propriedades-das-borrachas-vulcanizadas/propriedades-fisicas/propriedades- mecanicas/dureza. 34. Weatherly LM, Gosse JA. Triclosan exposure, transformation, and human health effects. J Toxicol Environ Health B Crit Rev. 2017;20(8):447-69. doi: 10.1080/10937404.2017.1399306. 35. Chen X, Mou L, Qu J, Wu L, Liu C. Adverse effects of triclosan exposure on health and potential molecular mechanisms. Sci Total Environ. 2023 Jun;879:163068. doi: 10.1016/j.scitotenv.2023.163068. 36. Ros-Llor I, Lopez-Jornet P. Cytogenetic analysis of oral mucosa cells, induced by chlorhexidine, essential oils in ethanolic solution and triclosan mouthwashes. Environ Res. 2014 Jul;132:140-5. doi: 10.1016/j.envres.2014.03.032.