1068 D3000 new imprint Word template Vol 13, No 1 (2025) ISSN 2167-8677 (online) DOI 10.5195/d3000.2025.1068 http://dentistry3000.pitt.edu Acrylic Denture Basis’ Long-Term Colour Stability Shahrazad Fouad Karkosh1, Amer Hussian Makki2 1Middle Technical University, Technical Medical Ins4tute, Baghdah, Iraq 2Uruk University, College of Health and Medical Technologies, Baghdad, Iraq Abstract Objec:ve: This study invesEgated how staining soluEons affected the acrylic denture bases' colour stability. Materials and Methods: FiOy-six samples of acrylic denture base (hot and cold) were submerged in disElled water for control and three staining soluEons. A spectrophotometer was uElized to measure colour Before immersion, every sample's iniEal colour value was noted. Following a 24-hour, one-week, and two-week immersion period, colour change values were calculated. Results: Hot coffee was the most preferred beverage, showing strong significance over both Eme periods (P = 0.002 for 24 hours, P = 0.013 for 1 week). This indicates a consistent preference for hot coffee. Karak and hibiscus demonstrated increasing preference over Eme, especially in their hot forms (P = 0.001 for hot Karak, P = 0.006 for hot hibiscus). This suggests that these drinks become more favored as habits de- velop. Comparison between 24-hour and 1-week data showed that coffee remained stable in preference, while Karak and hibiscus became more preferred over Eme. Conclusion: The denture base's discoloraEon rose in direct proporEon to the immersion Eme, and the instant coffee soluEon was discovered to be the most chromogenic staining soluEon. To maintain the color stability of acrylic dentures, us- ers should adopt good oral hygiene prac- Eces and minimize prolonged exposure to these beverages. Open Access Cita%on: Karkosh SF, et al. (2025) Acrylic Denture Basis’ Long-Term Colour Stability. Den%stry 3000. 1:a001 doi:10.5195/d3000.2025.1068 Received: October 8, 2025 Accepted: October 15, 2025 Published: November 10, 2025 Copyright: ©2025 Karkosh SF, et al. This is an open ac- cess ar%cle licensed under a Crea%ve Commons AUribu- %on Work 4.0 United States License. Email: Shahrazad.almunjm@mtu.edu.iq Introduc)on One of the most popular materials for creat- ing a denture base is acrylic, also known as polymethyl methacrylate [1]. due to its supe- rior mechanical and physical characteristics. Its drawbacks, however, include brittleness and liquid absorption with extended usage, which could damage its mechanical qualities [2]. The polar characteristics of resin mole- cules are the main cause of liquid absorption, which makes PMMA denture base materials more susceptible to food consumption, liq- uid exposure, and staining from denture cleaners [3]. The colour match and the material's colour stability over time are the primary factors that determine whether an aesthetic restorative material is successful or not. One crucial characteristic of many materials used in dentistry is colour stability, or the capacity of the material to maintain its original colour over time in a particular environment [4]. Over time, a number of internal and external factors that impact the mechanical and physical characteristics of acrylic resin can cause colour change [5]. Beverages, such as black tea, coffee, cola drinks, and fruit juices, have been shown to discolor denture surfaces. These beverages may also impact the surface Minish of the den- tures [6]. An annual herbaceous plant, hibiscus grows vertically and can reach a height of roughly two meters. The plant's branches have a reddish-green colour. The simple leaves have serrated edges and long petioles. Reddish-green leaves in the style of palms [7]. One of the most valuable plants for the culinary and pharmaceutical industries is Hibiscus sabdariffa, which is used as a pleasant beverage, particularly after being sweetened with sugar. After concentration, the extract is regarded as a colourful and enhanced material for the unique Mlavour [8]. Karak tea, a popular beverage in the Middle East, is known for its robust Mlavor from black tea, sugar, milk, and a mixture of spices, including cloves, cardamom, cinnamon, and ginger. This aromatic concoction offers several health beneMits, primarily attributed to its in- dividual components. Karak tea combines the health-promoting properties of black tea and various spices, offering antioxidant, di- gestive, anti-inMlammatory, and metabolic beneMits. However, mindful preparation and consumption are essential to maximize its advantages while minimizing potential drawbacks [9]. Acrylic Denture Basis’ Long-Term Colour Stability Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1068 http://dentistry3000.pitt.edu 2 One of the most consumed drinks in the world, coffee is prized for its deep Mlavour and invigorating properties.It is made from roasted coffee beans, which come from the Coffee plant. The drink contains caffeine, a natural stimulant that helps boost energy and alertness. Coffee is consumed in various forms, including espresso, cappuccino, and instant coffee, and can be served hot or cold. In many cultures, coffee is not just a drink but also a social tradition, often enjoyed with friends, family, or during work breaks [10]. Materials and Methods This study aimed to evaluate the colour stability of acrylic denture bases. that were heat-cured and cold-cured using three widely consumed beverages as staining agents and distilled water as a control. Fifty- six (56) specimens were prepared with wax, separated into two primary classes based on the type of denture base material after being conventionally converted to acrylic. 28 spec- imens were prepared with heat cured acrylic resin and 28 specimens with cold cure acrylic resin. Each group was split up into four smaller groups, each with seven samples, based on the kind of staining solution that was submerged in it. In total, 7 specimens immersion in coffee, 7 specimens immersion in Karak tea, 7 specimens immer- sion in hibiscus tea and 7 specimens immer- sion in distilled water only as control for 24 hours, one week and two weeks. Mold Preparation For this study, brass matrices were manufac- tured to standardize the dimensions of the specimens (50 mm length, 20 mm wide, 2 mm thick). The brass matrixes were invested in a denture Mlask with type II stone cast, to obtain molds, which were used to manufac- ture the standardized specimens. Sample Preparation Preparation of the heat cured acrylic samples The mold was prepared using the traditional Mlasking method for full dentures. Following the manufacturer's directions, all materials were combined and worked in each step, from packing and curing to Minishing, polish- ing, and conditioning. Preparation of the cold cured acrylic sam- ples Following the manufacturer's instructions, a 3:1 by volume mixture of polymer and monomer was used to create the necessary amount of self-cure acrylic resin (Italy). Preparing staining solutions According to the guidelines provided by the manufacturer, 250 mL of water was mixed with 5 g of coffee (Jordan), Karak tea (Jordan), and hibiscus tea (Saudi Arabia). The mixture was then put over a low heat and taken off before boiling. A paper Milter was then used to Milter the mixture. Every day, new solutions were made. Each time, the samples were carefully cleaned with soft toothbrush and water for 30 seconds to get rid of each debris from immersion [11]. Spectrophotometer measurements Following polishing and Minishing, the speci- mens were submerged in staining solutions and washed with room-temperature dis- tilled water. As a control, untreated group specimens were employed. The colour change was measured with a spectrophotometer, after 24 hours, 1 week, and 2 weeks [12]. Results (Tables 1-6 and Figures 1-3) There was a statistically signiMicant differ- ence between cold and hot distilled water (p = 0.041). The difference between hot and cold coffee was statistically signiMicant (p = 0.002). A difference between cold and hot hibiscus was observed (p = 0.008). There was no statistically signiMicant differ- ence between cold and hot Karak (p = 0.216). For distilled water, cold versus hot did not signiMicantly affect consumption. For coffee, karak, and hibiscus, the tempera- ture did have a statistically significant effect, with cold drinks being preferred for Karak and hibiscus, and hot coffee being preferred over cold. No significant difference was found between cold and hot variants for distilled water. Hot coffee significantly differed from cold coffee, with hot coffee having a higher mean. Hot Karak significantly differed from cold Karak, with hot Karak having a higher mean. Hot hibiscus significantly differed from cold hibiscus, with hot hibiscus having a higher mean. Hot beverages generally showed significant differences, except for distilled water (hot). For cold beverages, distilled water showed the only significant difference for cold. Karak and hibiscus showed differences for hot conditions. Only cold coffee (cold), and hot and cold hi- biscus showed statistically significant differ- ences implying that time (24 hours versus 1 week) affected their consumption in mean- ingful ways. Other beverages like distilled water and Karak did not show significant differences in either hot or cold conditions between 24 hours and 1 week. There was a significant difference between cold and hot coffee, and hot Karak. Hibiscus also showed signiMicant differences for both cold and hot. Discussion Since colour is regarded as a crucial component of any denture material, its stability during the course of the material's survival is seen as a key determinant of the success or failure of the prosthesis . All denture base materials were found to undergo colour changes, and these changes grew for every group during the immersion period. Denture base materials may change colour for a variety of reasons, which can be separated into intrinsic and extrinsic factors. These include the chemical makeup of the material, any remaining monomers, water absorption, the breakdown of intrinsic pigments, component leaching, stain accumulation, and surface roughness. Nevertheless, the types of food consumed are also important factors that contribute to colour stability over an extended length of time, in addition to polishing ability and material structure [13]. The base material used to make dentures is exposed to a variety of environments with Mluctuating oral temperatures, salivary pH levels, and their constituents. It also has to come into contact with a number of foods, beverages, and drinks consumed at different temperatures, making it vulnerable to changes in its physical composition and appearance as a result of the absorption of various contaminants [14]. Colour stability is the ability of a material to hold onto its colour over time in a speciMic environment. It is thought to be an essential physical property of dental materials [15]. By forming micro cracks associated with absorption and hydrolytic degradation of the polymer, water molecules that are absorbed by acrylic resin function as plasticizers to weaken the material's mechanical resistance, causing linkage cleavage and the slow deterioration of its infrastructure [16]. Because coffee is typically utilized in vitro research, it was chosen as the staining material for this investigation. Because coffee is yellow-brown, tannic acid has been identiMied as the main staining agent [17]. The Mindings demonstrated that all denture material types utilized in this study had color changes after immersion in staining solution, depending on the length of time. This is likely since denture base materials collect deposits and stains in the same way as natural teeth, but that hard deposits and stains, like those from coffee, Karak, and hibiscus, are much harder to remove. The material's surface has a certain amount of porosity and surface roughness, as well as an organic mucin and inorganic. The Mindings that demonstrated the surface characteristic, porosity that allows particles to accumulate and cause noticeable discolor- ation. This clariMied the Mindings that Acrylic Denture Basis’ Long-Term Colour Stability Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1068 http://dentistry3000.pitt.edu 3 indicated notable distinctions between heat- cured and cold-cured acrylic resin. The impact of solutions on the colour variations of denture base materials was found to be comparable in the current investigation. Coffee and hibiscus had the biggest colour change, whereas Karak showed the least. Compared to cold methyl methacrylate resin provisional materials, hot methyl methacrylate resin provisional materials were more colour stable [18]. Conclusion The following results were reached within the constraints of this investigation: 1. The denture base's discoloration rose in direct proportion to the immersion duration. 2. The instant coffee solution was determined to be the most chromogenic staining solution. References 1. Mikael J, Al-Samaraie S, Ikram F. Evalu- ation of Some Properties of Acrylic Resin Denture Base Reinforced with Calcium Carbonate Nano- Particles. Erbil Dental Journal (EDJ). 2018 Jun 6;1(1):41-7. 2. Alqutaibi AY, Baik A, Almuzaini SA, Far- ghal AE, Alnazzawi AA, Borzangy S, et al. Polymeric Denture Base Materials: A Review. Vol. 15, Poly- mers. Multidisciplinary Digital Publishing Insti- tute (MDPI); 2023;15:3258. 3. Keyf F, Etikan I. Evaluation of gloss changes of two denture acrylic resin materials in four different beverages. Dental Materials. 2004;20:244-51. 4. Madhyastha, Prashanthi S., et al. Effect of staining solutions on color stability of silorane & methacrylate restorative material. International Journal of Biomedical Science: IJBS, 2015, 11.1: 29. 5. Hong G, Murata H, Li Y, Sadamori S, Hamada T. Inaluence of denture cleansers on the color stability of three types of denture base acrylic resin. J Prosthet Dent 2009;101:205-13. 6. Sham ASK, Chu FCS, Chai J, Chow TW. Color stability of provisional prosthodontic mate- rials. Journal of Prosthetic Dentistry. 2004;91:447-52. 7. Al-Kahtani N, Almurayh A, Subbarayalu AV, Sebastian T, Alkahtani H, Aljabri D. Sustaining blended and online learning during the normal and new normal conditions in a Saudi higher edu- cation institution: health science students' per- spectives. Heliyon. 2022 Oct 1;8. 8. Shruthi VH, Ramachandra CT, Udayku- mar Nidoni UN, Sharanagouda Hiregoudar SH, Na- garaj Naik NN, Kurubar AR. Roselle (Hibiscus sabdariffa L.) as a source of natural colour: a re- view. Plant Archives 2016;16(2):515-522. 9. Ahmed S. The Drink of Dearborn. Kennesaw State University 2024. English 1101 Showcase 37. 10. 10-Myhrvold, Nathan. Coffee Encyclo- pedia Britannica, 18 Mar 2025. 11. Valizadeh S, Asiaie Z, Kiomarsi N, Kha- razifard MJ. Color stability of self-adhering compo- site resins in different solutions. Dental and Medi- cal Problems. 2020 Jan 1;57(1):31-8. 12. Prasad DK, Alva H, Shetty M. Evaluation of colour stability of provisional restorative mate- rials exposed to different mouth rinses at varying time intervals: an in vitro study. The Journal of In- dian Prosthodontic Society. 2014 Mar;14(1):85- 92. 13. Hollis S, Eisenbeisz E, Versluis A. Color stability of denture resins after staining and expo- sure to cleansing agents. The Journal of Prosthetic Dentistry. 2015 Nov 1;114(5):709-14. 14. Assunção WG, Barão VA, Pita MS, Goiato MC (2009). Effect of polymerization methods and thermal cycling on color stability of acrylic resin denture teeth. J Prosthet Dent, 102, 385-392 15. Goiato MC, Nóbrega AS, Santos DM, An- dreotti AM, Moreno A. Effect of different solutions on color stability of acrylic resin-based dentures. Brazilian Oral Research. 2013 Dec 17;28:1-7. 16. Imirzalioglu P, Karacaer O, Yilmaz B, Ozmen Msc I. Color stability of denture acrylic res- ins and a soft lining material against tea, coffee, and nicotine. J Prosthodont. 2010; 19 (2):118-24. 17. Hollis S, Eisenbeisz E, Versluis A. Color stability of denture resins after staining and expo- sure to cleansing agents J Prosthet Dent. 2015;114: 709–14. 18. Bayindir F, Kürklü D, Yanikoğlu ND. The effect of staining solutions on the color stability of provisional prosthodontic materials. Journal of Dentistry. 2012 Dec 1;40:e41-6. Table 1. Results after 24 h. N Mean Standard Deviation P-value distilled water Cold 5 49.7840 4.48322 0.041 Hot 5 38.3400 3.08086 coffee Cold 5 26.7760 6.21864 0.002 Hot 5 56.7080 6.38243 Karak Cold 5 24.9640 3.65085 0.216 Hot 5 26.1900 2.36219 Hibiscus Cold 5 29.1780 2.02280 0.008 Hot 5 31.9700 1.41317 Acrylic Denture Basis’ Long-Term Colour Stability Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1068 http://dentistry3000.pitt.edu 4 Table 2. Results after 1 week. N Mean Standard Deviation P-value distilled water cold 5 38.526 3.284 0.176 hot 5 40.126 3.65267 coffee cold 5 32.75 2.64833 0.023 hot 5 38.352 3.27629 Karak cold 5 19.112 3.60012 0.048 hot 5 14.662 3.1038 Hibiscus cold 5 15.022 1.76379 0.047 hot 5 21.25 4.64618 0 10 20 30 40 50 60 cold hot cold hot cold hot cold hot distal water coffee karak Hibscus 49.784 38.34 26.776 56.708 24.964 26.19 29.178 31.97 Figure 1. Average AE values that were acquired from samples that were immersed in various solutions for 24 h. Acrylic Denture Basis’ Long-Term Colour Stability Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1068 http://dentistry3000.pitt.edu 5 Table 3. Results after 2 weeks. N Mean Standard Deviation P-value distilled water cold 5 26.622 36.48096 0.324 hot 5 27.282 37.3602 coffee cold 5 41.726 3.43239 0.000 hot 5 57.896 3.49028 Karak cold 5 21.95 1.98813 0.045 hot 5 24.384 2.0034 hibiscus cold 5 36.706 5.66449 0.005 hot 5 55.08 3.71653 0 5 10 15 20 25 30 35 40 45 cold hot cold hot cold hot cold hot distal water coffee karak Hibscus 38.526 40.126 32.75 38.352 19.112 14.662 15.022 21.25 Figure 2. Average AE values derived from samples that were immersed in various solutions one week. Acrylic Denture Basis’ Long-Term Colour Stability Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1068 http://dentistry3000.pitt.edu 6 Figure 3. Mean AE values obtained from the samples soaked in different solution for two weeks. Table 4. Comparison between 24 hours and 1 week. T P-value distilled water 24hr-1 week (cold) 2.335 0.047 24hr-1 week (hot) -1.589 0.187 Coffee 24hr-1 week (cold) -2.342 0.049 24hr-1 week (hot) 4.306 0.013 Karak 24hr-1 week (cold) 2.077 0.106 24hr-1 week (hot) 7.775 0.001 Hibiscus 24hr-1 week(cold) 9.572 0.001 24hr-1 week (hot) 5.344 0.006 .0000 10.0000 20.0000 30.0000 40.0000 50.0000 60.0000 cold hot cold hot cold hot cold hot distal water coffee karak Hibscus 26.6220 27.2820 41.7260 57.8960 21.9500 24.3840 36.7060 55.0800 Acrylic Denture Basis’ Long-Term Colour Stability Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1068 http://dentistry3000.pitt.edu 7 Table 5. Comparison between 24 hours and 2 weeks. t P-value distilled water 24hr -2 weeks (cold) 1.568 0.192 24hr -2 weeks (hot) 0.894 0.422 Coffee 24hr-2 weeks (cold) -4.283 0.013 24hr-2 weeks (hot) -0.327 0.76 Karak 24hr-2 weeks (cold) 1.582 0.189 24hr-2 weeks (hot) 1.49 0.21 Hibiscus 24hr-2 weeks(cold) -2.36 0.048 24hr-1 week (hot) -14.31 0.000 . Table 6. Comparison between 1 week and 2 weeks. t P-value distilled water 1 week-2 weeks (cold) 0.903 0.418 1 week-2 weeks (hot) 0.956 0.393 Coffee 1 week-2 weeks (cold) -8.282 0.001 1 week-2 weeks (hot) -10.443 0.000 Karak 1 week-2 weeks (cold) -1.225 0.288 1 week-2 weeks (hot) -6.905 0.002 Hibiscus 1 week-2 weeks (cold) -10.852 0.000 1 week-2 weeks (hot) -9.541 0.001