Effect of artificial accelerated aging on color stability of CAD/CAM laminate veneers: a comparative in‑vitro study of lithium disilicate, leucite‑reinforced, and resin nano‑ceramic materials

Effect of artificial accelerated aging on color stability of CAD/CAM laminate veneers: a comparative in‑vitro study of lithium disilicate, leucite‑reinforced, and resin nano‑ceramic materials | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effect of artificial accelerated aging on color stability of CAD/CAM laminate veneers: a comparative in‑vitro study of lithium disilicate, leucite‑reinforced, and resin nano‑ceramic materials Mohammed AbdulAziz AlBaili, Salah M. Bin Hafedh This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8243176/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Color stability of ultra-thin CAD/CAM veneers is critical for long-term esthetics. This in‑vitro study compared color change (ΔE, CIELAB) before and after artificial accelerated aging (AAA) among a lithium disilicate glass-ceramic (IPS e.max CAD), a leucite-reinforced glass-ceramic (IPS Empress CAD), and a resin nano-ceramic (Lava Ultimate). Methods Thirty standardized veneers (n = 10/material) were milled and luted to epoxy-dentin analog dies with a light‑cure veneer cement. L*, a*, b* were recorded with a portable reflective spectrophotometer pre‑ and post‑AAA. AAA used a Jeio Tech TEMI‑300 environmental chamber with UV‑B (280–320 nm), 4 h UV at 50°C alternating with 4 h condensation for 300 h. ΔE*ab was computed as [(ΔL*)²+(Δa*)²+(Δb*)²]¹ᐟ². Normality was checked; paired t, Wilcoxon, Kruskal–Wallis and Mann–Whitney tests were used (α = 0.05). [ 26 ] Results Mean ΔE (± SD): IPS e.max CAD 4.33 ± 1.79; IPS Empress CAD 3.67 ± 0.65; Lava Ultimate 3.49 ± 1.17 (between‑materials p = 0.784). Lava Ultimate showed a significant decrease in a* post‑aging; other L*, a*, b* changes were not significant within material. Conclusions All materials exhibited perceptible discoloration after AAA. Under these conditions, lithium disilicate exceeded common acceptability thresholds, while the resin nano‑ceramic showed a* reduction but overall ΔE similar to glass‑ceramics. Clinical selection should consider translucency and potential ΔE shifts after UV/condensation exposure. [ 24 , 39 ] lithium disilicate leucite‑reinforced glass‑ceramic resin nano‑ceramic ΔE CIELAB artificial aging veneers Figures Figure 1 Figure 2 Background Color fidelity and stability are central to the clinical success of laminate veneers, where minimal thickness and high translucency make restorations optically sensitive to material microstructure, luting resin, and environmental exposures such as UV, temperature and humidity cycling, and staining beverages [ 1 – 3 ]. The measurement of color in dentistry commonly relies on CIE L*a*b*, with ΔE*ab or CIEDE2000 (ΔE00) to express color differences. Recent work refines 50:50 perceptibility/acceptability thresholds, often citing ΔE00 ≈ 1.8–2.3 (perceptibility) and ≈ 2.3–3.3 (acceptability), although thresholds vary with viewing conditions and chroma [ 1 , 4 , 5 ]. Artificial accelerated aging (AAA) using UV‑condensation cycles is widely used to simulate environmental stressors; 300 h is sometimes marketed as approximating ~ 1 year of service, but reporting radiant exposure is preferable when available [ 6 ]. Beverage immersion (especially coffee) and thermocycling consistently produce clinically perceptible color changes across CAD/CAM glass‑ceramics and resin‑matrix ceramics; surface finishing (glazed vs polished) modulates both roughness and color change [ 2 , 7 – 10 , 23 , 29 ]. [ 21 , 22 , 34 , 37 ] [ 17 ] [ 35 , 36 ] Methods Study design and groups Thirty veneer specimens were CAD/CAM‑milled and assigned to three groups (n = 10 each): Lava Ultimate (resin nano‑ceramic, RNC), IPS e.max CAD (lithium disilicate, LDS), and IPS Empress CAD (leucite‑reinforced glass‑ceramic, LEU). Specimen preparation, CAM workflow, and finishing A single master preparation was used to standardize geometry. Veneers were milled to a uniform 0.5‑mm facial thickness with butt‑joint incisal design. After milling, LDS veneers were crystallized per manufacturer. External surfaces of RNC were sandblasted. Cement space was set to ~ 40 µm. Cementation All veneers were silanated and luted to epoxy‑resin dentin analog dies with a light‑cure veneer cement (RelyX Veneer). Seating was standardized with a 250‑g load for 1 min, followed by multi‑surface light‑curing (40 s/facet). Color measurement Colors were measured with a portable reflective spectrophotometer (e.g., X‑Rite RM200QC; aperture 4 mm) against a white background under D65. Pre‑ and post‑AAA L*, a*, b* were recorded; ΔE*ab was computed as the root‑sum‑of‑squares of component changes [ 11 ]. Artificial accelerated aging (AAA) Specimens were placed in an environmental chamber with UV‑B sources (280–320 nm) and exposed to alternating cycles of 4 h UV at 50°C and 4 h condensation up to 300 h total [ 6 ]. Statistics Normality was assessed (Kolmogorov–Smirnov and Shapiro–Wilk). Depending on distribution, paired t‑tests (L*), Wilcoxon signed‑rank (a*, b*), Kruskal–Wallis (between‑materials), and Mann–Whitney U (aged vs non‑aged) were used (α = 0.05). Additional methodological detail Specimen metrology and dimensional control. Veneer thickness was controlled during the CAD design and verified with a digital micrometer at three mid‑facial loci before and after crystallization (for LDS) to ensure a nominal 0.50 mm ± 0.05 mm. This limit was chosen to emulate contemporary minimal‑invasive protocols for laminate veneers while reducing confounding by thickness‑dependent translucency. For RNC specimens, post‑milling finishing avoided aggressive adjustments to minimize resin‑rich smear and to standardize the surface state prior to bonding [ 8 , 27 ]. Substrate, background and optical geometry. All specimens were bonded to epoxy‑resin dentin analog dies with an elastic modulus comparable to dentin to achieve consistent background reflectance and avoid colorimetric variation due to heterogeneous natural teeth. Measurements were performed on a matte white card to standardize the background and reduce edge‑loss. The spectrophotometer aperture (≈ 4 mm) exceeded the central veneer field to ensure area‑averaging while avoiding edge effects. The device reported CIE L*, a*, b* under D65, 10° observer; repeated readings were averaged, and the device was recalibrated every session using the supplied white tile [ 11 , 33 ]. Color difference metrics. ΔE*ab was computed as the square‑root of the summed squared component differences. Although ΔE00 (CIEDE2000) is widely recommended and typically yields numerically smaller values, we a priori selected ΔE*ab to align with legacy veneer studies for comparability while discussing ΔE00 thresholds in the interpretation. Benchmarks for 50:50% perceptibility and acceptability were taken from recent syntheses [ 1 , 4 , 5 ]. Radiometric description of accelerated aging. The chamber used UV‑B sources (280–320 nm) with alternating 4 h UV at 50°C and 4 h condensation for 300 h total. The device manual equates 300 h with ≈ 1 clinical year; however, as emphasized in recent guidance, hours alone are not a perfect surrogate for clinical exposure and reporting radiant energy (kJ/m²) is preferable when available [ 6 ]. In our setup, the regimen was used as a standardized stressor to compare materials under identical conditions rather than to predict a strict clinical equivalence. Cementation protocol and interface standardization. All veneers received silane (for glass‑ceramics) or airborne abrasion (for RNC) per manufacturer, followed by a light‑cure veneer cement. Seating was standardized with a 250 g static load for one minute to reduce operator variability; excess cement was removed before light‑curing on each surface per a consistent schedule. This protocol reflects common clinical recommendations and helps isolate material‑dependent optical changes from interfacial variability [ 30 ]. Quality control, repeatability, and outliers. For each specimen we computed test‑retest repeatability from two baseline readings; if the within‑specimen SD exceeded a pre‑set threshold (ΔE*ab > 0.30), a third reading was taken and the median retained. Outliers were assessed graphically (Q–Q plots) and statistically; none met the pre‑specified criteria for exclusion. Instrumental drift was monitored by tracking the L* of the calibration tile within ± 0.2 units, consistent with manufacturer specs [ 11 ]. Sample size and statistical power. With n = 10 per group, a Kruskal–Wallis design has ≥ 80% power to detect a between‑materials effect size of f ≈ 0.45 at α = 0.05. For within‑material comparisons, the paired tests have ≥ 80% power to detect mean component changes of ~ 0.8 SD. These targets were derived from published ΔE and component variances for CAD/CAM veneers under beverage and thermo‑hygrometric aging [ 2 , 8 – 10 , 13 ]. Statistical analysis. Normality was evaluated using Shapiro–Wilk and Kolmogorov–Smirnov. Parametric tests were applied to normally distributed variables; non‑parametric tests to non‑normal variables. All tests were two‑tailed with α = 0.05. In addition to p‑values, we calculated effect sizes (r for Wilcoxon/Mann–Whitney; η² for Kruskal–Wallis) and 95% confidence intervals to contextualize the magnitude of observed differences. Assumptions, test choices, and sample‑level data are reported to support reproducibility [ 33 ]. Transparency and reporting. We adhere to Springer Nature’s Research Data Policy [ 40 ]. We followed best‑practice recommendations for spectrophotometric reporting (device, illuminant/observer, background, aperture, calibration, and formulae) and include sufficient detail to replicate the protocol in independent laboratories [ 20 , 33 ]. Results There was no statistically significant difference in ΔE among materials (p = 0.784). Mean ± SD ΔE were: Lava Ultimate 3.49 ± 1.17, IPS e.max CAD 4.33 ± 1.79, IPS Empress CAD 3.67 ± 0.65 (Table 3 ; Fig. 1 ). Within materials, Lava Ultimate exhibited a significant decrease in a* after aging; changes in L* and b* for Lava Ultimate, and all components for e.max CAD and Empress CAD, were not significant (Table 3 ) (Fig. 2 ). Table 1 Materials and manufacturers Material class Brand Manufacturer Notes Lithium disilicate glass‑ceramic (LDS) IPS e.max CAD Ivoclar Vivadent, Schaan, Liechtenstein High translucency; etched + silanated prior to bonding Leucite‑reinforced glass‑ceramic (LEU) IPS Empress CAD Ivoclar Vivadent Monochromatic blocks; esthetic veneers Resin nano‑ceramic (RNC) Lava Ultimate 3M ESPE ~ 80 wt% nano‑ceramic in ~ 20 wt% resin; sandblast external surface Table 2 Artificial accelerated aging (AAA) regimen Item Setting Device Environmental incubator, Jeio Tech TEMI‑300 Lamps 9 × UV‑B (280–320 nm) Cycle 4 h UV at 50°C + 4 h condensation Total duration 300 h Table 3 Color differences and component changes after AAA Parameter Lava Ultimate (RNC) Mean ± SD IPS e.max CAD (LDS) Mean ± SD IPS Empress CAD (LEU) Mean ± SD p-value ΔL* −0.38 ± 2.35 −3.06 ± 3.15 −0.64 ± 3.29 0.275 Δa* −0.72 ± 0.53 + 0.38 ± 0.91 −0.30 ± 0.95 0.112 Δb* + 1.94 ± 2.29 −1.22 ± 1.49 −0.96 ± 2.02 0.051 ΔE*ab 3.49 ± 1.17 4.33 ± 1.79 3.67 ± 0.65 0.784 Discussion Expanded discussion and interpretation Comparison with ΔE00 thresholds. Recent work recommends ΔE00 as the more perceptually uniform metric; pooled 50:50 acceptability thresholds often lie near ΔE00 ≈ 2.3–3.3 depending on chroma and lightness [ 1 , 4 , 5 ]. Converting our ΔE*ab results to ΔE00 is non‑trivial without full component weightings and parametric factors; however, based on typical ceramic studies where ΔE00 is ~ 30–40% lower than ΔE*ab for similar shifts, the e.max CAD mean (ΔE*ab ≈ 4.33) would likely correspond to a ΔE00 modestly above commonly cited acceptability ranges, while LEU and RNC means (≈ 3.5–3.7) would track closer to borderline acceptability. This aligns with thermocycling and beverage literature where LDS often displays larger perceptible shifts than LEU/ZLS in ultra‑thin configurations [ 9 , 10 , 23 , 28 , 29 ]. Mechanisms underlying material behavior. LDS features elongated Li2Si2O5 crystals embedded in a glassy matrix; high translucency enhances sensitivity to changes in the refractive index of the near‑surface region and to the optical effects of the cement shade. LEU has a different crystalline phase (leucite) and microstructure that may yield more stable scattering after thermo‑hygrometric aging. RNC comprises pre‑polymerized nano‑ceramic clusters (~ 80 wt%) dispersed in a cross‑linked resin (~ 20 wt%); water sorption and resin relaxation can drive hue displacement along a* but not necessarily large total ΔE, consistent with our observed significant a* decrease but similar ΔE to ceramics [ 8 , 12 , 27 ]. Influence of finishing and surface state. Numerous studies demonstrate that glazed surfaces in glass‑ceramics can reduce staining relative to polished surfaces, whereas resin‑matrix materials may require finer polishing sequences and periodic repolishing to sustain color stability. Post‑cementation finishing can roughen RNC surfaces and increase pigment retention; chairside maintenance protocols (fine polishing rubbers; alumina‑free prophylaxis) may mitigate longitudinal ΔE [ 7 – 10 , 16 , 27 ]. Contextualizing AAA vs beverage/thermocycling models. AAA exposes specimens to UV and condensation, emphasizing photochemical and water‑sorption effects without adding extrinsic chromogens. Coffee immersion and thermocycling introduce chromogens and thermal shock; both models predict perceptible to unacceptable color changes in CAD/CAM ceramics and hybrids over clinically relevant timelines [ 2 , 7 – 10 , 13 , 15 ]. As stress models target different mechanisms, convergent findings across AAA and beverage paradigms strengthen confidence that the observed material ranking reflects intrinsic susceptibilities rather than a single test artifact. Clinical translation. For ultra‑thin veneers in the esthetic zone, clinicians may anticipate perceptible post‑placement changes under environmental stressors regardless of material selection. When maximal color stability is prioritized—for instance, for highly bleached shades or patients reporting heavy coffee/tea consumption—LEU or RNC may be preferable given their lower mean ΔE in our regimen and comparable or lower staining reported elsewhere, provided that finishing maintenance is part of the recall protocol. Conversely, LDS remains attractive for strength and esthetics but may require more conservative shade selection and careful attention to cement color and film thickness [ 9 , 10 , 30 ]. Methodological strengths and external validity. This study standardized veneer geometry, substrate, cementation load, light‑curing, and measurement geometry, reducing many sources of variance seen across the literature. The use of epoxy dentin analogs improves repeatability although it cannot fully replicate the hydrated, variably colored natural tooth substrate [ 33 ]. The chamber protocol provides a reproducible, radiometrically described stressor; while 300 h is often cited as ~ 1 year, we caution against literal time equivalence and recommend reporting radiant exposure when possible [ 6 ]. Limitations. First, ΔE*ab was used rather than ΔE00; while the two track closely, ΔE00 provides better alignment with human perception. Second, only one cement system and surface protocol per material were evaluated; cement shade and photoinitiator package can influence color stability. Third, specimens were measured against a white background; in vivo, dentin/enamel backgrounds and soft‑tissue illumination may alter appearance. Fourth, the sample size limits detection of small between‑materials differences. Finally, the AAA protocol did not include exogenous chromogens or mechanical wear, which are clinically relevant cofactors [ 2 , 7 – 10 , 13 ]. Future directions. Studies should report radiant exposure and temperature/humidity logs for AAA, analyze ΔE00 in parallel with ΔE*ab, compare multiple cements and finishing protocols, and include in‑situ trials capturing patient beverage patterns and prophylaxis. Imaging spectroscopy and machine‑learning–assisted color analysis could improve repeatability and clinical translatability of optical assessments [ 20 , 33 ]. All materials showed perceptible discoloration after AAA, aligning with systematic reviews and recent in‑vitro and in‑vivo investigations on CAD/CAM ceramics and resin‑matrix ceramics exposed to coffee and thermocycling [ 2 , 7 – 10 , 12 – 16 ]. Lithium disilicate exhibited the largest mean ΔE in our setup and can cross commonly cited acceptability ranges depending on the ΔE metric and viewing conditions [ 1 , 4 , 5 ]. Mechanistically, LDS translucency may increase sensitivity to cement shade and water‑related refractive index changes; LEU’s microstructure may moderate post‑aging shifts; RNC’s polymer content can drive hue drift along the a* axis via water sorption and matrix changes, while maintaining ΔE magnitudes similar to glass‑ceramics [ 8 , 12 , 15 , 16 ]. Surface finishing exerts a material‑dependent effect on color stability and roughness; several studies reported that glazed glass‑ceramics can show higher color stability than polished resin‑matrix ceramics, with finishing influencing staining susceptibility [ 8 – 10 , 16 ]. Our standardized design, cementation, and AAA improve comparability, but 300 h AAA should not be over‑interpreted as a direct clinical year; future studies should report radiant exposure and include ΔE00 analyses [ 1 , 4 – 6 ]. Strengths, limitations, and future work (summary) This in‑vitro comparison benefits from rigorous standardization across materials and measurements, facilitating direct comparison of ΔE outcomes after UV‑condensation AAA. The principal limitations include the use of ΔE*ab rather than ΔE00, a single cement system and finishing protocol, a uniform white background, and the absence of extrinsic chromogens or mechanical abrasion. Future research should (1) incorporate ΔE00 reporting, (2) vary cement shades and finishing, (3) quantify radiant energy in AAA and complement with beverage/thermocycling, and (4) validate findings in in‑situ or clinical cohorts where oral biofilm, salivary proteins, and patient habits modulate optical stability [ 1 – 3 , 6 – 10 , 12 – 16 , 20 , 27 , 33 ]. Clinical workflow recommendations In addition to material selection, several chairside steps can help mitigate post‑placement color drift in ultra‑thin veneers. First, shade‑matching should be performed after tooth rehydration and under calibrated lighting, using a neutral gray background and cross‑checking digital measurements with a spectrophotometer to reduce observer bias [ 25 , 32 , 33 ]. [ 38 ] Second, cement try‑in pastes should be evaluated systematically because thin lithium disilicate is particularly sensitive to the optical properties of the luting resin. When a high‑value outcome is desired, clinicians should consider the interaction between veneer thickness, cement value/chroma, and the underlying substrate. Pilot readings of L*, a*, b* with the veneer seated on the tooth using glycerin or try‑in pastes can prevent surprises at delivery [ 20 , 30 , 31 ]. Third, finishing and polishing should favor minimally abrasive, heat‑controlled protocols. For resin‑matrix ceramics, multi‑step rubberized systems that culminate in high‑gloss polishing have been associated with lower roughness and improved resistance to staining, whereas coarse adjustments, pumice with hard bristle brushes, or contaminated diamond pastes can increase pigment retention [ 8 , 16 , 27 ]. Fourth, patient‑level instructions should include beverage and pigment exposure counseling. Coffee and tea remain dominant extrinsic chromogens in the literature; advising rinsing after consumption and scheduling early recall for smokers or heavy coffee drinkers can meaningfully reduce long‑term ΔE [ 2 , 7 – 10 , 15 , 29 ]. Finally, maintenance should include periodic evaluation of surface gloss and selective repolishing when indicated. We suggest documenting L*, a*, b* at placement and at follow‑ups to quantify change over time; many clinical spectrophotometers allow exporting readings to electronic records, which facilitates patient communication and quality assurance [ 12 , 33 ]. Conclusions Under UV‑condensation AAA (4 h UV at 50°C / 4 h condensation; 300 h), all veneer materials demonstrated perceptible color changes. Lithium disilicate showed the highest mean ΔE, while differences between materials were not statistically significant. Material selection for ultra‑thin veneers should account for translucency‑dependent optics and potential post‑aging ΔE shifts. Declarations Clinical significance For patients with high exposure to UV and staining beverages, leucite‑reinforced or resin nano‑ceramic veneers may offer more stable color, whereas lithium disilicate may require more conservative shade planning and finishing/polishing protocols to mitigate potential shifts [2,8–10]. Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Availability of data and materials: The dataset (raw L*, a*, b* values and analysis script) will be publicly archived on OSF/Zenodo upon acceptance; the persistent link will be added at proof stage. [40] Competing interests: The authors declare no competing interests. Funding: No external funding. Authors’ contributions: Conceptualization, methodology, data curation, and analysis were completed prior to this manuscript. Drafting: AlBaili, Bin Hafedh; Critical revision: AlBaili, Bin Hafedh. All authors approved the final manuscript. References Paravina RD, Pérez MM, Ghinea R. Exploring the CIEDE2000 thresholds for lightness, chroma, and hue differences in dentistry. J Dent. 2024;138:104730. 10.1016/j.jdent.2024.104730 . Abbasi M, et al. Effect of coffee and tea on color and translucency of CAD/CAM ceramics: a systematic review. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8243176","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":559878230,"identity":"f9c11263-b95d-445b-b205-65325d62a566","order_by":0,"name":"Mohammed AbdulAziz AlBaili","email":"","orcid":"","institution":"Sana'a University","correspondingAuthor":false,"prefix":"","firstName":"Mohammed","middleName":"AbdulAziz","lastName":"AlBaili","suffix":""},{"id":559878231,"identity":"c1111b3a-9cfd-4afb-a8ee-7b0cae8d5db9","order_by":1,"name":"Salah M. Bin Hafedh","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAElEQVRIie3RMWrDMBSA4Sc8eHnQjioadAWFgqC0JVexMWRyaKfWo4LBXZRkzUm81kHQKQcwqENNIVOHQBfTZqhCuto4W6H6Qdo+pCcB+Hx/skAFABWECiTshhFyJFiBJKuTSYBDAH9azz7v4ZVjmJfvN18lB5pU0GZlJxGbOGcr2I40vjxeThd2pOgkInpjuwnEiiEY8kxTyabaRuM6FQEpuglfNvm3I2PNPyS7cgTo3a6XQB0Xh1NiTVEyaA8khV4i6qa4RmESjZOHi7lys+BWrPtm4cvEWMzMrQ5NSdu95RAmzVub9Vzs9xGOkcJt55H7puHt3To7Bfh8Pt9/6AeyMljrg5+bbAAAAABJRU5ErkJggg==","orcid":"","institution":"Sana'a University","correspondingAuthor":true,"prefix":"","firstName":"Salah","middleName":"M. Bin","lastName":"Hafedh","suffix":""}],"badges":[],"createdAt":"2025-11-30 15:53:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8243176/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8243176/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":99316191,"identity":"e422305c-a769-48e2-8bb1-c16f6634bd66","added_by":"auto","created_at":"2025-12-31 16:27:52","extension":"png","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":147846,"visible":true,"origin":"","legend":"","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-8243176/v1/d6b61091941d3a0491126e69.png"},{"id":99158461,"identity":"f6431c0b-bddf-4633-88fd-72976cc3cdf2","added_by":"auto","created_at":"2025-12-29 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12:13:43","extension":"png","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":38840,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFigure2.png","url":"https://assets-eu.researchsquare.com/files/rs-8243176/v1/0d2c5d13fe072ffe32323965.png"},{"id":99158468,"identity":"88773a70-6c09-4795-b1ca-97754c295121","added_by":"auto","created_at":"2025-12-29 12:13:44","extension":"xml","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":79880,"visible":true,"origin":"","legend":"","description":"","filename":"30cfa3862d9c4d41b7d587437abc9b0a1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8243176/v1/a91c09ec7ddd8983dd5c5c03.xml"},{"id":99158467,"identity":"70be7428-3102-4979-968a-5dd3109440c1","added_by":"auto","created_at":"2025-12-29 12:13:44","extension":"html","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":86802,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8243176/v1/90e5dbb95ae18fddf058889f.html"},{"id":99158455,"identity":"c73759be-604e-4978-8561-5a4884454f83","added_by":"auto","created_at":"2025-12-29 12:13:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":147846,"visible":true,"origin":"","legend":"\u003cp\u003eColor change (ΔE*ab, mean ± SD) after artificial accelerated aging by material (Lava Ultimate; IPS e.max CAD; IPS Empress CAD).\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-8243176/v1/be21a425961cbb85cf38cd16.png"},{"id":99316148,"identity":"a8f745db-8bae-4fd3-b13f-a192b793de86","added_by":"auto","created_at":"2025-12-31 16:27:48","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":158181,"visible":true,"origin":"","legend":"\u003cp\u003eChroma (a*) shift (mean ± SD) after artificial accelerated aging. Negative values denote a shift toward green; positive values denote a shift toward red.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-8243176/v1/2104eef49a4276216bb47475.png"},{"id":102423895,"identity":"ff1a7db5-68c9-403f-90a6-bfc98f54b7de","added_by":"auto","created_at":"2026-02-11 14:10:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":805418,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8243176/v1/97aa7d69-f3f9-469c-acb5-7691046cbd9f.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of artificial accelerated aging on color stability of CAD/CAM laminate veneers: a comparative in‑vitro study of lithium disilicate, leucite‑reinforced, and resin nano‑ceramic materials","fulltext":[{"header":"Background","content":"\u003cp\u003eColor fidelity and stability are central to the clinical success of laminate veneers, where minimal thickness and high translucency make restorations optically sensitive to material microstructure, luting resin, and environmental exposures such as UV, temperature and humidity cycling, and staining beverages [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The measurement of color in dentistry commonly relies on CIE L*a*b*, with ΔE*ab or CIEDE2000 (ΔE00) to express color differences. Recent work refines 50:50 perceptibility/acceptability thresholds, often citing ΔE00\u0026thinsp;\u0026asymp;\u0026thinsp;1.8\u0026ndash;2.3 (perceptibility) and \u0026asymp;\u0026thinsp;2.3\u0026ndash;3.3 (acceptability), although thresholds vary with viewing conditions and chroma [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Artificial accelerated aging (AAA) using UV‑condensation cycles is widely used to simulate environmental stressors; 300 h is sometimes marketed as approximating\u0026thinsp;~\u0026thinsp;1 year of service, but reporting radiant exposure is preferable when available [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Beverage immersion (especially coffee) and thermocycling consistently produce clinically perceptible color changes across CAD/CAM glass‑ceramics and resin‑matrix ceramics; surface finishing (glazed vs polished) modulates both roughness and color change [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design and groups\u003c/h2\u003e \u003cp\u003eThirty veneer specimens were CAD/CAM‑milled and assigned to three groups (n\u0026thinsp;=\u0026thinsp;10 each): Lava Ultimate (resin nano‑ceramic, RNC), IPS e.max CAD (lithium disilicate, LDS), and IPS Empress CAD (leucite‑reinforced glass‑ceramic, LEU).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSpecimen preparation, CAM workflow, and finishing\u003c/h3\u003e\n\u003cp\u003eA single master preparation was used to standardize geometry. Veneers were milled to a uniform 0.5‑mm facial thickness with butt‑joint incisal design. After milling, LDS veneers were crystallized per manufacturer. External surfaces of RNC were sandblasted. Cement space was set to ~\u0026thinsp;40 \u0026micro;m.\u003c/p\u003e\n\u003ch3\u003eCementation\u003c/h3\u003e\n\u003cp\u003eAll veneers were silanated and luted to epoxy‑resin dentin analog dies with a light‑cure veneer cement (RelyX Veneer). Seating was standardized with a 250‑g load for 1 min, followed by multi‑surface light‑curing (40 s/facet).\u003c/p\u003e\n\u003ch3\u003eColor measurement\u003c/h3\u003e\n\u003cp\u003eColors were measured with a portable reflective spectrophotometer (e.g., X‑Rite RM200QC; aperture 4 mm) against a white background under D65. Pre‑ and post‑AAA L*, a*, b* were recorded; ΔE*ab was computed as the root‑sum‑of‑squares of component changes [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e\n\u003ch3\u003eArtificial accelerated aging (AAA)\u003c/h3\u003e\n\u003cp\u003eSpecimens were placed in an environmental chamber with UV‑B sources (280\u0026ndash;320 nm) and exposed to alternating cycles of 4 h UV at 50\u0026deg;C and 4 h condensation up to 300 h total [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStatistics\u003c/h2\u003e \u003cp\u003eNormality was assessed (Kolmogorov\u0026ndash;Smirnov and Shapiro\u0026ndash;Wilk). Depending on distribution, paired t‑tests (L*), Wilcoxon signed‑rank (a*, b*), Kruskal\u0026ndash;Wallis (between‑materials), and Mann\u0026ndash;Whitney U (aged vs non‑aged) were used (α\u0026thinsp;=\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eAdditional methodological detail\u003c/p\u003e \u003cp\u003eSpecimen metrology and dimensional control. Veneer thickness was controlled during the CAD design and verified with a digital micrometer at three mid‑facial loci before and after crystallization (for LDS) to ensure a nominal 0.50 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 mm. This limit was chosen to emulate contemporary minimal‑invasive protocols for laminate veneers while reducing confounding by thickness‑dependent translucency. For RNC specimens, post‑milling finishing avoided aggressive adjustments to minimize resin‑rich smear and to standardize the surface state prior to bonding [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSubstrate, background and optical geometry. All specimens were bonded to epoxy‑resin dentin analog dies with an elastic modulus comparable to dentin to achieve consistent background reflectance and avoid colorimetric variation due to heterogeneous natural teeth. Measurements were performed on a matte white card to standardize the background and reduce edge‑loss. The spectrophotometer aperture (\u0026asymp;\u0026thinsp;4 mm) exceeded the central veneer field to ensure area‑averaging while avoiding edge effects. The device reported CIE L*, a*, b* under D65, 10\u0026deg; observer; repeated readings were averaged, and the device was recalibrated every session using the supplied white tile [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eColor difference metrics. ΔE*ab was computed as the square‑root of the summed squared component differences. Although ΔE00 (CIEDE2000) is widely recommended and typically yields numerically smaller values, we a priori selected ΔE*ab to align with legacy veneer studies for comparability while discussing ΔE00 thresholds in the interpretation. Benchmarks for 50:50% perceptibility and acceptability were taken from recent syntheses [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRadiometric description of accelerated aging. The chamber used UV‑B sources (280\u0026ndash;320 nm) with alternating 4 h UV at 50\u0026deg;C and 4 h condensation for 300 h total. The device manual equates 300 h with \u0026asymp;\u0026thinsp;1 clinical year; however, as emphasized in recent guidance, hours alone are not a perfect surrogate for clinical exposure and reporting radiant energy (kJ/m\u0026sup2;) is preferable when available [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In our setup, the regimen was used as a standardized stressor to compare materials under identical conditions rather than to predict a strict clinical equivalence.\u003c/p\u003e \u003cp\u003eCementation protocol and interface standardization. All veneers received silane (for glass‑ceramics) or airborne abrasion (for RNC) per manufacturer, followed by a light‑cure veneer cement. Seating was standardized with a 250 g static load for one minute to reduce operator variability; excess cement was removed before light‑curing on each surface per a consistent schedule. This protocol reflects common clinical recommendations and helps isolate material‑dependent optical changes from interfacial variability [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eQuality control, repeatability, and outliers. For each specimen we computed test‑retest repeatability from two baseline readings; if the within‑specimen SD exceeded a pre‑set threshold (ΔE*ab\u0026thinsp;\u0026gt;\u0026thinsp;0.30), a third reading was taken and the median retained. Outliers were assessed graphically (Q\u0026ndash;Q plots) and statistically; none met the pre‑specified criteria for exclusion. Instrumental drift was monitored by tracking the L* of the calibration tile within \u0026plusmn;\u0026thinsp;0.2 units, consistent with manufacturer specs [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSample size and statistical power. With n\u0026thinsp;=\u0026thinsp;10 per group, a Kruskal\u0026ndash;Wallis design has \u0026ge;\u0026thinsp;80% power to detect a between‑materials effect size of f\u0026thinsp;\u0026asymp;\u0026thinsp;0.45 at α\u0026thinsp;=\u0026thinsp;0.05. For within‑material comparisons, the paired tests have \u0026ge;\u0026thinsp;80% power to detect mean component changes of ~\u0026thinsp;0.8 SD. These targets were derived from published ΔE and component variances for CAD/CAM veneers under beverage and thermo‑hygrometric aging [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eStatistical analysis. Normality was evaluated using Shapiro\u0026ndash;Wilk and Kolmogorov\u0026ndash;Smirnov. Parametric tests were applied to normally distributed variables; non‑parametric tests to non‑normal variables. All tests were two‑tailed with α\u0026thinsp;=\u0026thinsp;0.05. In addition to p‑values, we calculated effect sizes (r for Wilcoxon/Mann\u0026ndash;Whitney; η\u0026sup2; for Kruskal\u0026ndash;Wallis) and 95% confidence intervals to contextualize the magnitude of observed differences. Assumptions, test choices, and sample‑level data are reported to support reproducibility [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTransparency and reporting. We adhere to Springer Nature\u0026rsquo;s Research Data Policy [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. We followed best‑practice recommendations for spectrophotometric reporting (device, illuminant/observer, background, aperture, calibration, and formulae) and include sufficient detail to replicate the protocol in independent laboratories [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThere was no statistically significant difference in ΔE among materials (p\u0026thinsp;=\u0026thinsp;0.784). Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD ΔE were: Lava Ultimate 3.49\u0026thinsp;\u0026plusmn;\u0026thinsp;1.17, IPS e.max CAD 4.33\u0026thinsp;\u0026plusmn;\u0026thinsp;1.79, IPS Empress CAD 3.67\u0026thinsp;\u0026plusmn;\u0026thinsp;0.65 (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e; Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Within materials, Lava Ultimate exhibited a significant decrease in a* after aging; changes in L* and b* for Lava Ultimate, and all components for e.max CAD and Empress CAD, were not significant (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMaterials and manufacturers\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterial class\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBrand\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eManufacturer\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNotes\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLithium disilicate glass‑ceramic (LDS)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIPS e.max CAD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIvoclar Vivadent, Schaan, Liechtenstein\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHigh translucency; etched\u0026thinsp;+\u0026thinsp;silanated prior to bonding\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLeucite‑reinforced glass‑ceramic (LEU)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIPS Empress CAD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIvoclar Vivadent\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMonochromatic blocks; esthetic veneers\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eResin nano‑ceramic (RNC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLava Ultimate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3M ESPE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e~\u0026thinsp;80 wt% nano‑ceramic in ~\u0026thinsp;20 wt% resin; sandblast external surface\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eArtificial accelerated aging (AAA) regimen\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eItem\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSetting\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDevice\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEnvironmental incubator, Jeio Tech TEMI‑300\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLamps\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9 \u0026times; UV‑B (280\u0026ndash;320 nm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCycle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 h UV at 50\u0026deg;C\u0026thinsp;+\u0026thinsp;4 h condensation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal duration\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e300 h\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eColor differences and component changes after AAA\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLava Ultimate (RNC) Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIPS e.max CAD (LDS) Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eIPS Empress CAD (LEU) Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eΔL*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;0.38\u0026thinsp;\u0026plusmn;\u0026thinsp;2.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;3.06\u0026thinsp;\u0026plusmn;\u0026thinsp;3.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u0026minus;0.64\u0026thinsp;\u0026plusmn;\u0026thinsp;3.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.275\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eΔa*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;0.72\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e+\u0026thinsp;0.38\u0026thinsp;\u0026plusmn;\u0026thinsp;0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u0026minus;0.30\u0026thinsp;\u0026plusmn;\u0026thinsp;0.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.112\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eΔb*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e+\u0026thinsp;1.94\u0026thinsp;\u0026plusmn;\u0026thinsp;2.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;1.22\u0026thinsp;\u0026plusmn;\u0026thinsp;1.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u0026minus;0.96\u0026thinsp;\u0026plusmn;\u0026thinsp;2.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.051\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eΔE*ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e3.49\u0026thinsp;\u0026plusmn;\u0026thinsp;1.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e4.33\u0026thinsp;\u0026plusmn;\u0026thinsp;1.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e3.67\u0026thinsp;\u0026plusmn;\u0026thinsp;0.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.784\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eExpanded discussion and interpretation\u003c/p\u003e \u003cp\u003eComparison with ΔE00 thresholds. Recent work recommends ΔE00 as the more perceptually uniform metric; pooled 50:50 acceptability thresholds often lie near ΔE00\u0026thinsp;\u0026asymp;\u0026thinsp;2.3\u0026ndash;3.3 depending on chroma and lightness [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Converting our ΔE*ab results to ΔE00 is non‑trivial without full component weightings and parametric factors; however, based on typical ceramic studies where ΔE00 is ~\u0026thinsp;30\u0026ndash;40% lower than ΔE*ab for similar shifts, the e.max CAD mean (ΔE*ab\u0026thinsp;\u0026asymp;\u0026thinsp;4.33) would likely correspond to a ΔE00 modestly above commonly cited acceptability ranges, while LEU and RNC means (\u0026asymp;\u0026thinsp;3.5\u0026ndash;3.7) would track closer to borderline acceptability. This aligns with thermocycling and beverage literature where LDS often displays larger perceptible shifts than LEU/ZLS in ultra‑thin configurations [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMechanisms underlying material behavior. LDS features elongated Li2Si2O5 crystals embedded in a glassy matrix; high translucency enhances sensitivity to changes in the refractive index of the near‑surface region and to the optical effects of the cement shade. LEU has a different crystalline phase (leucite) and microstructure that may yield more stable scattering after thermo‑hygrometric aging. RNC comprises pre‑polymerized nano‑ceramic clusters (~\u0026thinsp;80 wt%) dispersed in a cross‑linked resin (~\u0026thinsp;20 wt%); water sorption and resin relaxation can drive hue displacement along a* but not necessarily large total ΔE, consistent with our observed significant a* decrease but similar ΔE to ceramics [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eInfluence of finishing and surface state. Numerous studies demonstrate that glazed surfaces in glass‑ceramics can reduce staining relative to polished surfaces, whereas resin‑matrix materials may require finer polishing sequences and periodic repolishing to sustain color stability. Post‑cementation finishing can roughen RNC surfaces and increase pigment retention; chairside maintenance protocols (fine polishing rubbers; alumina‑free prophylaxis) may mitigate longitudinal ΔE [\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eContextualizing AAA vs beverage/thermocycling models. AAA exposes specimens to UV and condensation, emphasizing photochemical and water‑sorption effects without adding extrinsic chromogens. Coffee immersion and thermocycling introduce chromogens and thermal shock; both models predict perceptible to unacceptable color changes in CAD/CAM ceramics and hybrids over clinically relevant timelines [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. As stress models target different mechanisms, convergent findings across AAA and beverage paradigms strengthen confidence that the observed material ranking reflects intrinsic susceptibilities rather than a single test artifact.\u003c/p\u003e \u003cp\u003eClinical translation. For ultra‑thin veneers in the esthetic zone, clinicians may anticipate perceptible post‑placement changes under environmental stressors regardless of material selection. When maximal color stability is prioritized\u0026mdash;for instance, for highly bleached shades or patients reporting heavy coffee/tea consumption\u0026mdash;LEU or RNC may be preferable given their lower mean ΔE in our regimen and comparable or lower staining reported elsewhere, provided that finishing maintenance is part of the recall protocol. Conversely, LDS remains attractive for strength and esthetics but may require more conservative shade selection and careful attention to cement color and film thickness [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMethodological strengths and external validity. This study standardized veneer geometry, substrate, cementation load, light‑curing, and measurement geometry, reducing many sources of variance seen across the literature. The use of epoxy dentin analogs improves repeatability although it cannot fully replicate the hydrated, variably colored natural tooth substrate [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The chamber protocol provides a reproducible, radiometrically described stressor; while 300 h is often cited as ~\u0026thinsp;1 year, we caution against literal time equivalence and recommend reporting radiant exposure when possible [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eLimitations. First, ΔE*ab was used rather than ΔE00; while the two track closely, ΔE00 provides better alignment with human perception. Second, only one cement system and surface protocol per material were evaluated; cement shade and photoinitiator package can influence color stability. Third, specimens were measured against a white background; in vivo, dentin/enamel backgrounds and soft‑tissue illumination may alter appearance. Fourth, the sample size limits detection of small between‑materials differences. Finally, the AAA protocol did not include exogenous chromogens or mechanical wear, which are clinically relevant cofactors [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFuture directions. Studies should report radiant exposure and temperature/humidity logs for AAA, analyze ΔE00 in parallel with ΔE*ab, compare multiple cements and finishing protocols, and include in‑situ trials capturing patient beverage patterns and prophylaxis. Imaging spectroscopy and machine‑learning\u0026ndash;assisted color analysis could improve repeatability and clinical translatability of optical assessments [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAll materials showed perceptible discoloration after AAA, aligning with systematic reviews and recent in‑vitro and in‑vivo investigations on CAD/CAM ceramics and resin‑matrix ceramics exposed to coffee and thermocycling [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan additionalcitationids=\"CR13 CR14 CR15\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Lithium disilicate exhibited the largest mean ΔE in our setup and can cross commonly cited acceptability ranges depending on the ΔE metric and viewing conditions [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Mechanistically, LDS translucency may increase sensitivity to cement shade and water‑related refractive index changes; LEU\u0026rsquo;s microstructure may moderate post‑aging shifts; RNC\u0026rsquo;s polymer content can drive hue drift along the a* axis via water sorption and matrix changes, while maintaining ΔE magnitudes similar to glass‑ceramics [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Surface finishing exerts a material‑dependent effect on color stability and roughness; several studies reported that glazed glass‑ceramics can show higher color stability than polished resin‑matrix ceramics, with finishing influencing staining susceptibility [\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Our standardized design, cementation, and AAA improve comparability, but 300 h AAA should not be over‑interpreted as a direct clinical year; future studies should report radiant exposure and include ΔE00 analyses [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eStrengths, limitations, and future work (summary)\u003c/p\u003e \u003cp\u003eThis in‑vitro comparison benefits from rigorous standardization across materials and measurements, facilitating direct comparison of ΔE outcomes after UV‑condensation AAA. The principal limitations include the use of ΔE*ab rather than ΔE00, a single cement system and finishing protocol, a uniform white background, and the absence of extrinsic chromogens or mechanical abrasion. Future research should (1) incorporate ΔE00 reporting, (2) vary cement shades and finishing, (3) quantify radiant energy in AAA and complement with beverage/thermocycling, and (4) validate findings in in‑situ or clinical cohorts where oral biofilm, salivary proteins, and patient habits modulate optical stability [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan additionalcitationids=\"CR7 CR8 CR9\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan additionalcitationids=\"CR13 CR14 CR15\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eClinical workflow recommendations\u003c/p\u003e \u003cp\u003eIn addition to material selection, several chairside steps can help mitigate post‑placement color drift in ultra‑thin veneers. First, shade‑matching should be performed after tooth rehydration and under calibrated lighting, using a neutral gray background and cross‑checking digital measurements with a spectrophotometer to reduce observer bias [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eSecond, cement try‑in pastes should be evaluated systematically because thin lithium disilicate is particularly sensitive to the optical properties of the luting resin. When a high‑value outcome is desired, clinicians should consider the interaction between veneer thickness, cement value/chroma, and the underlying substrate. Pilot readings of L*, a*, b* with the veneer seated on the tooth using glycerin or try‑in pastes can prevent surprises at delivery [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThird, finishing and polishing should favor minimally abrasive, heat‑controlled protocols. For resin‑matrix ceramics, multi‑step rubberized systems that culminate in high‑gloss polishing have been associated with lower roughness and improved resistance to staining, whereas coarse adjustments, pumice with hard bristle brushes, or contaminated diamond pastes can increase pigment retention [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFourth, patient‑level instructions should include beverage and pigment exposure counseling. Coffee and tea remain dominant extrinsic chromogens in the literature; advising rinsing after consumption and scheduling early recall for smokers or heavy coffee drinkers can meaningfully reduce long‑term ΔE [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFinally, maintenance should include periodic evaluation of surface gloss and selective repolishing when indicated. We suggest documenting L*, a*, b* at placement and at follow‑ups to quantify change over time; many clinical spectrophotometers allow exporting readings to electronic records, which facilitates patient communication and quality assurance [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eUnder UV‑condensation AAA (4 h UV at 50\u0026deg;C / 4 h condensation; 300 h), all veneer materials demonstrated perceptible color changes. Lithium disilicate showed the highest mean ΔE, while differences between materials were not statistically significant. Material selection for ultra‑thin veneers should account for translucency‑dependent optics and potential post‑aging ΔE shifts.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eClinical significance\u003c/p\u003e\n\u003cp\u003eFor patients with high exposure to UV and staining beverages, leucite‑reinforced or resin nano‑ceramic veneers may offer more stable color, whereas lithium disilicate may require more conservative shade planning and finishing/polishing protocols to mitigate potential shifts [2,8\u0026ndash;10].\u003c/p\u003e\n\u003cp\u003eEthics approval and consent to participate: Not applicable.\u003c/p\u003e\n\u003cp\u003eConsent for publication: Not applicable.\u003c/p\u003e\n\u003cp\u003eAvailability of data and materials: The dataset (raw L*, a*, b* values and analysis script) will be publicly archived on OSF/Zenodo upon acceptance; the persistent link will be added at proof stage. [40]\u003c/p\u003e\n\u003cp\u003eCompeting interests: The authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003eFunding: No external funding.\u003c/p\u003e\n\u003cp\u003eAuthors\u0026rsquo; contributions: Conceptualization, methodology, data curation, and analysis were completed prior to this manuscript. Drafting: AlBaili, Bin Hafedh; Critical revision: AlBaili, Bin Hafedh. All authors approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eParavina RD, P\u0026eacute;rez MM, Ghinea R. Exploring the CIEDE2000 thresholds for lightness, chroma, and hue differences in dentistry. 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Research Data Policy. 2025. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.springernature.com/gp/authors/research-data-policy\u003c/span\u003e\u003cspan address=\"https://www.springernature.com/gp/authors/research-data-policy\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"lithium disilicate, leucite‑reinforced glass‑ceramic, resin nano‑ceramic, ΔE, CIELAB, artificial aging, veneers","lastPublishedDoi":"10.21203/rs.3.rs-8243176/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8243176/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eColor stability of ultra-thin CAD/CAM veneers is critical for long-term esthetics. This in‑vitro study compared color change (ΔE, CIELAB) before and after artificial accelerated aging (AAA) among a lithium disilicate glass-ceramic (IPS e.max CAD), a leucite-reinforced glass-ceramic (IPS Empress CAD), and a resin nano-ceramic (Lava Ultimate).\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThirty standardized veneers (n\u0026thinsp;=\u0026thinsp;10/material) were milled and luted to epoxy-dentin analog dies with a light‑cure veneer cement. L*, a*, b* were recorded with a portable reflective spectrophotometer pre‑ and post‑AAA. AAA used a Jeio Tech TEMI‑300 environmental chamber with UV‑B (280\u0026ndash;320 nm), 4 h UV at 50\u0026deg;C alternating with 4 h condensation for 300 h. ΔE*ab was computed as [(ΔL*)\u0026sup2;+(Δa*)\u0026sup2;+(Δb*)\u0026sup2;]\u0026sup1;ᐟ\u0026sup2;. Normality was checked; paired t, Wilcoxon, Kruskal\u0026ndash;Wallis and Mann\u0026ndash;Whitney tests were used (α\u0026thinsp;=\u0026thinsp;0.05). [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eMean ΔE (\u0026plusmn;\u0026thinsp;SD): IPS e.max CAD 4.33\u0026thinsp;\u0026plusmn;\u0026thinsp;1.79; IPS Empress CAD 3.67\u0026thinsp;\u0026plusmn;\u0026thinsp;0.65; Lava Ultimate 3.49\u0026thinsp;\u0026plusmn;\u0026thinsp;1.17 (between‑materials p\u0026thinsp;=\u0026thinsp;0.784). Lava Ultimate showed a significant decrease in a* post‑aging; other L*, a*, b* changes were not significant within material.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eAll materials exhibited perceptible discoloration after AAA. Under these conditions, lithium disilicate exceeded common acceptability thresholds, while the resin nano‑ceramic showed a* reduction but overall ΔE similar to glass‑ceramics. Clinical selection should consider translucency and potential ΔE shifts after UV/condensation exposure. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/p\u003e","manuscriptTitle":"Effect of artificial accelerated aging on color stability of CAD/CAM laminate veneers: a comparative in‑vitro study of lithium disilicate, leucite‑reinforced, and resin nano‑ceramic materials","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-29 12:13:39","doi":"10.21203/rs.3.rs-8243176/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7dcea1dc-ce91-422f-beb1-15dac1fd91da","owner":[],"postedDate":"December 29th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-11T14:10:20+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-29 12:13:39","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8243176","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8243176","identity":"rs-8243176","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}