Search Results (257)

This work aims to find a chemical process that modifies the surface finish of precision metal spheres to enable their use as reference elements in optical metrology. The chemical process should not substantially alter the original quality or dimensional accuracy, but it should give the spheres a matte finish, eliminating reflections. The spheres used are AISI 316L stainless steel bearing spheres, which are of low cost, high availability and great dimensional accuracy, making them suitable as reference elements if their high gloss is removed. Two procedures are tested in the research. On the one hand, different passivation acids are tested, and on the other, a chemical attack with a much more aggressive acid, aqua regia (hydrochloric acid, HCl, and nitric acid, HNO₃, in a 1:3 ratio). Tests showed that none of the passivation methods sufficiently eliminated glare and reflections. However, chemical etching by immersion in aqua regia did produce a matte and homogeneous surface finish, reducing reflectivity and promoting the diffusion of incident light without loss of precision. The paper presents the tests to find the optimal exposure time to aqua regia as well as the influence of chemical etching from a dimensional and geometrical point of view, both in contact and laser sensor optical measurement. The research has considered a representative series of the chemical attack procedure to validate the repeatability of the method. Finally, it has been verified that the method is repeatable and that improvements (close to 45%) in the metrological accuracy of the laser sensor measurements are achieved when using spheres treated with aqua regia compared to original spheres. In conclusion, it has been demonstrated that the chemical attack with aqua regia is not only a valid method for generating matte surfaces suitable for optical metrology, but a process that can also be implemented at low cost and with high reproducibility. Full article

Glued-laminated timber (GLT) and cross-laminated timber (CLT) panels are increasingly used as exposed structural elements in representative buildings. These structures are often part of public-use areas, which require the application of restrictive fire-safety measures without significantly affecting the color of exposed wooden surfaces during the service life of these building elements. The effect of fire-retardant treatments on the color of Scots pine (Pinus sylvestris L.) wood was evaluated using five impregnation agents with different active substances. Changes in gloss and color characteristics—lightness (L*), green-red coordinate (a*), and blue-and-yellow coordinate (b*)—were measured sequentially directly after impregnation, after exposure to variable humidity conditions and after exposure to UV radiation. The total color difference (ΔE*) ranged from 2.82 to 17.76 after impregnation and increased to 6.31–20.71 after aging, indicating a risk of aesthetic deterioration of fire-retardant-treated wood surfaces under typical service conditions for timber structures in representative buildings. The most pronounced color changes were observed for the fire retardant containing potassium and copper compounds (FR4) and the combination of 2-aminoethanol with boric acid (FR5). Full article

Background/Objectives: Lithium disilicate (LD) veneers are widely used for minimally invasive anterior rehabilitation because of their favorable optical and mechanical properties. Fully digital workflows have been proposed as alternatives to conventional milling. These approaches combine computer-aided design and manufacturing (CAD/CAM) with 3D-printed burn-out patterns and subsequent heat pressing of LD ingots. However, clinical documentation of multi-unit anterior cases fabricated exclusively through this additive-plus-pressing route remains scarce. This case report aims to describe a fully digital additive-plus-pressing workflow for four maxillary anterior LD veneers and to report 48-month clinical outcomes. Case Presentation: A 52-year-old female presented with esthetic concerns involving the maxillary central and lateral incisors (teeth 11, 12, 21, and 22). After clinical and radiographic evaluation, a minimally invasive veneer-based rehabilitation was planned. Preparations were performed under magnification, and immediate dentin sealing was applied. Digital impressions were obtained with an intraoral scanner, and veneers were designed using CAD software(Exocad DentalDB 3.0 Galway (Exocad GmbH, Darmstadt, Germany). Castable resin patterns were 3D-printed, invested, and heat-pressed using LD ingots, followed by finishing and glazing. Adhesive cementation was performed under rubber dam isolation after hydrofluoric acid etching and silanization of the intaglio surfaces and conditioning of the tooth substrates according to the adhesive protocol, using a dual-cure resin cement. At the 48-month follow-up, all veneers remained intact, with clinically acceptable marginal adaptation, stable color and surface gloss, and no signs of secondary caries or marginal discoloration. The patient reported sustained esthetic satisfaction and comfortable function without postoperative sensitivity. Conclusions: This single-patient report suggests that a fully digital additive-plus-pressing workflow may be clinically viable for high-demand anterior LD veneers, providing favorable medium-term esthetics and patient-centered outcomes with no technical or biological complications. The reproducible protocol described may facilitate the integration of 3D printing and heat pressing into digital veneer rehabilitation and supports further controlled clinical investigations. Full article

In multicolor painting for interior and exterior building finishes, a topcoat is often applied to protect the surface. Because topcoats are transparent, it is difficult to confirm whether one has been applied visually. However, Korean courts use empirical methods to determine whether topcoats have been applied in housing defect litigation. Typical empirical methods include observing gloss and assessing water-repellent properties. Pencils, water-based pens, and computer pens are used to assess graffiti-prevention properties. However, these empirical methods rely solely on appraisers’ experience and visual inspection, lacking standardized methods or detailed criteria. Furthermore, it is not even known whether each empirical method produces identical results. This study aimed to identify these inconsistencies by applying and comparing all known empirical methods to physical buildings. After assessing four locations in two apartment complexes, gloss was not found in any of the cases. The water-repellent and pencil tests showed a correlation coefficient of −1, demonstrating exactly opposite trends. The water-based pen test showed a correlation coefficient of 0.745 for black and blue, but none for red. The computer pen test results differed significantly from the other tests, and no correlation was found. These findings confirm that current empirical methods for detecting a topcoat in multicolor painting are inconsistent and should not be used. Full article

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

Background: This in vitro study compared color stability, surface properties, and microbial adhesion of four gingival epithesis materials (silicone: Gingivamoll^®; nylon: Valplast^®; PETG-based high-performance polymer: Eldy Plus^®; PMMA: Palapress^®) after staining. Methods: Standardized specimens (10 × 10 × 2 mm; n = 18/material) underwent 15 or 30 staining cycles (sequential immersion in coffee, curry, tea, and 40% alcohol). Color (CIELAB) and color difference (ΔE00), gloss (G), and surface roughness (Ra) were measured at baseline and after 15 and 30 cycles; surface morphology was assessed by SEM. Microbial adhesion was assessed using a six-species biofilm model and quantified as log CFU at baseline and after 15 and 30 cycles. Results: All materials showed clinically relevant discoloration (ΔE00 > 2). Valplast^® exhibited the greatest color change (p < 0.05), while color change in other materials remained lower. Gingivamoll^® showed the lowest gloss and highest roughness, whereas other materials remained smoother; roughness increased significantly over time (p < 0.05). SEM revealed a coating on the hard materials and nodular agglomerates on silicone. Biofilm CFU did not differ over time or between materials (all p > 0.05). Conclusions: Staining induced material-dependent changes in color and surface properties, with Valplast^® most prone to discoloration and silicone showing high roughness and nodular surface changes, contrasting with coatings on hard materials. Microbial adhesion analysis yielded pilot-level results, intended to inform the design of future investigations. Full article

Objectives: This systematic review evaluated enamel surface alterations and residual composite following the removal of clear aligner attachments, with particular emphasis on the influence of removal techniques, instrument selection, operator experience, and the use of magnification on enamel preservation and cleaning efficiency. Methods: A comprehensive electronic search was performed in PubMed, Scopus, Embase, Web of Science, and Scielo up to October 2025. In vitro, ex vivo, and clinical studies assessing enamel loss, residual composite, surface roughness, or removal time after clear aligner attachment removal were included. Study selection, data extraction, and methodological assessment followed the PRISMA 2020 guidelines and Cochrane Handbook recommendations. Risk of bias was evaluated using a modified Joanna Briggs Institute checklist for laboratory-based studies. Due to substantial methodological heterogeneity, a narrative synthesis was conducted. Results: Of 656 identified records, three in vitro/ex vivo studies were assessed for eligibility. Reported enamel loss ranged from approximately 15 µm to more than 50 µm, depending on the removal protocol and visualization conditions. Residual composite covered approximately 20–40% of the treated enamel surface. Multi-step protocols combining tungsten carbide burs with silicone polishers under magnification demonstrated the most favorable balance between composite removal efficiency and enamel preservation. Fiberglass burs were associated with smoother enamel surfaces but increased enamel loss, whereas one-step polishing systems (OneGloss, Enhance, SM104) resulted in reduced surface roughness and shorter procedural time. The use of magnification loupes (≥2.5×) consistently improved removal precision and reduced residual composite. Meta-analysis was not feasible due to heterogeneity in outcome measures and testing methodologies. Overall risk of bias was deemed acceptable. Conclusions: Based on the limited number of available in vitro/ex vivo studies, removal of clear aligner attachments appears to be associated with measurable enamel loss and residual composite, largely influenced by the instruments and visualization aids used. Sequential carbide–silicone polishing protocols performed under magnification appear promising based on limited in vitro/ex vivo evidence, demonstrating a favorable balance between composite removal and enamel preservation under controlled laboratory conditions. However, given the scarcity of evidence and absence of clinical trials, these findings cannot be directly extrapolated to routine clinical practice. Further well-designed studies are required before definitive clinical recommendations can be established. Full article

Heat damage is a common phenomenon that often occurs when drying and straightening hair. After heat damage, the hydrophobic barrier on the hair’s surface becomes disrupted, thereby altering the hair’s hydrophilicity. Meanwhile, during the process of heat damage, the rupture of the hair’s cuticles causes the hair to become dry and rough, with a decrease in gloss and a decline in mechanical properties. This study utilized epoxy silane and hydrolyzed wool keratin to synthesize a thermally responsive organic silicon-modified keratin (OSK) to prevent hair from heat damage. OSK was synthesized from epoxy silane and hydrolyzed keratin, with yield determined by quantifying free amino groups. Its hair-care performance was evaluated through assessments of hair surface morphology, mechanical properties, and optical gloss, and by combing test and contact angle measurements. Mechanisms underlying surface hydrophobicity and hair scale protection were investigated using FTIR, XPS, and DSC. Specific performance parameters were evaluated using a single-fiber strength tester and a multifunctional hair-testing instrument. FTIR confirmed successful covalent grafting, with synthesis optimized to a 90.67% yield. OSK forms a protective film on hair surfaces, verified by SEM, XPS, and TEM, restoring damaged hair hydrophobicity to a 117° contact angle and enhancing thermal protection to 136° upon heating. Beyond hydrophobic-barrier restoration, OSK improved hair gloss by 30.26% and reduced frizz by 39.33%, while restoring the key performance of virgin hair. It also provides exceptional water-repellency protection and sensory enhancement. Under thermal stress, the protective film mechanically increased tensile strength by 6.58% and yield zone tensile force by 4.65%. This article demonstrates that OSK is an effective heat-sensitive agent. When damaged by heat sources such as hair dryers, it will form a protective film on the surface of the hair, thereby protecting the surface properties of the hair. Full article

Objectives: This study investigated the effects of three over-the-counter (OTC) whitening products, whitening pen (WP, Dazzling White Instant Whitening Pen, Dazzling White, Grand Rapids, MI, USA), whitening mouthwash (MW, Colgate Optic White, Colgate-Palmolive, New York, NY, USA), and whitening toothpaste (TP, Crest 3D White, Procter & Gamble, Cincinnati, OH, USA), on the microhardness, gloss retention, and surface roughness of a nanofilled resin composite (Filtek Z350 XT Universal Restorative, 3M ESPE). Methods: Composite resin specimens were prepared and subjected to treatment with WP, MW, or TP. Microhardness, gloss retention, and surface roughness were measured before and after treatment. Data were subjected to statistical analysis, with normality assessed by Shapiro–Wilk testing. Parametric data were summarized as mean ± SD, and differences were evaluated using paired t-tests and one-way ANOVA with a significance level of p ≤ 0. 05. Results: All whitening products significantly altered the tested surface properties. Microhardness decreased in all groups (MD [95% CI]: 2.28 [1.84–2.71] for WP, 5.05 [4.22–5.88] for MW, and 3.09 [2.35–3.83] for TP; p < 0.001), with the greatest reduction observed in the MW group. Gloss retention also declined significantly (MD [95% CI]: 9.52 [6.28–12.76] for WP, 17.97 [14.92–21.01] for MW, and 18.92 [15.64–22.21] for TP; p < 0.001), with TP and MW showing greater loss compared to WP. Surface roughness increased significantly within each group (MD [95% CI]: −0.07 [–0.10 to −0.04] for WP, −0.23 [–0.30 to −0.16] for MW, and −0.25 [–0.38 to −0.13] for TP; p < 0.001), although no significant differences were found among groups in post-treatment values. Conclusions: OTC whitening products adversely affected the optical and mechanical properties of Z350 XT universal composite resin. Whitening MW caused the most pronounced microhardness reduction, while MW and TP induced greater gloss loss than WP. Clinicians should consider the potential impact of whitening products on resin composite restorations when advising patients on their use. Full article

This in vitro study aimed to evaluate the effects of resin type, layer thickness, and printing orientation on the surface and mechanical properties of 3D-printed occlusal splints fabricated using digital light processing (DLP) technology. Three commercially available splint resins (KeySplint Hard, Freeprint Splint 2.0, and V-Print Splint) were used to fabricate 180 rectangular specimens with two-layer thicknesses (50 µm and 100 µm) and three printing orientations (0°, 45°, 90°). Surface roughness (Ra, Rz), gloss, microhardness, flexural strength, and elastic modulus were measured. Statistical analysis was performed using robust ANOVA with Bonferroni correction. Resin type and printing orientation significantly influenced all surface and mechanical properties (p < 0.001), while layer thickness had a limited effect. Keystone resin exhibited the smoothest surface and highest gloss, whereas Freeprint resin showed the highest microhardness and elastic modulus. Printing at 45° generally enhanced flexural strength and provided more balanced mechanical performance. SEM analysis confirmed that surface morphology varied with orientation, correlating with profilometric and gloss measurements. Resin composition and printing orientation are critical determinants of the mechanical and surface performance of 3D-printed occlusal splints. Optimizing these parameters can improve durability, esthetics, and clinical functionality. All tested materials achieved clinically acceptable surface smoothness, supporting their suitability for intraoral use. Full article

This study examines the pigment-dependent photoaging behavior of laboratory-prepared mock-up Chinese lacquer coatings colored with cinnabar, orpiment, and lapis lazuli under high-pressure mercury-lamp irradiation. Colorimetric results showed rapid changes within the first three days, with maximum ΔE values of 14.05 (red), 16.74 (yellow), and 17.97 (blue) after 30 days. Cinnabar-based films exhibited the highest color stability, whereas orpiment and lapis-lazuli coatings underwent pronounced hue shifts and chroma increases. Gloss loss and surface roughness evolution displayed a strong negative correlation: orpiment coatings experienced the most severe degradation, with gloss decreasing by over 60% and surface roughness increasing by approximately 70%, while cinnabar coatings showed the least decline (≈55% gloss loss; ≈27% roughness increase). SEM analysis further revealed extensive cracking and particle fragmentation in orpiment films, moderate surface disruption in lapis-lazuli films, and minimal microstructural damage in cinnabar films. Non-invasive reflection-mode FTIR spectroscopy confirmed these trends, showing minimal chemical change in cinnabar coatings but significant carbonyl growth, C–O–C band broadening, and aliphatic chain cleavage in orpiment and lapis-lazuli coatings. These results highlight the critical role of pigment chemistry in modulating UV-induced degradation pathways. Integrating optical, morphological, and chemical evidence, this study establishes a clear pigment-dependent degradation mechanism and provides valuable guidance for evaluating the long-term stability of lacquered cultural heritage and optimizing modern lacquer formulations. Full article

Lignin-based polyurethanes represent a promising strategy for developing more sustainable wood coatings by partially replacing fossil-derived polyols with renewable aromatic biopolymers. In this study, a polyurethane formulated with organosolv lignin (LPU) was synthesized and applied on two non-durable European wood species, Fagus sylvatica L. and Picea abies L., and compared with a commercial fossil-based polyurethane (CPU). Coated samples were evaluated for color stability, gloss evolution, wettability, adhesion, impact and scratch resistance, and biological durability. Accelerated ageing was performed under xenon-light irradiation, while decay resistance was assessed against Gloeophyllum trabeum and Trametes versicolor. Additional tests examined susceptibility to blue-stain fungi and surface morphology via SEM. LPU produced a matte film with intrinsically darker coloration but excellent chromatic stability and minimal gloss variation during ageing. Its initial hydrophobicity was higher on beech and comparable to CPU on spruce. Although CPU exhibited superior adhesion and slightly better mechanical resistance, LPU provided enhanced protection against blue-stain fungi—particularly on spruce—and a more uniform response to decay fungi across wood species. Overall, despite its darker appearance, the lignin-based formulation offered functional protection comparable to the commercial coating, confirming its potential as a viable bio-based alternative for above-ground wood applications. Full article

This study investigates the substitution of fossil-based isocyanates with bio-based alternatives in polyurethane resin (PU) coatings and polyurethane dispersion (PUD) coatings, focusing on mechanical and thermal performance. The coatings were formulated using bio-based pentamethylene diisocyanate (PDI) and a range of fossil-based hexamethylene diisocyanate (HDI) trimers, combined with either a polyester polyol or a polyacrylate polyol. Differential-scanning calorimetry analysis revealed that PDI-based coatings exhibit higher reactivity during crosslinking, resulting in higher glass transition temperatures. Thermogravimetric analysis showed lower thermal stability compared to HDI-based polyurethanes, indicating increased rigidity but reduced thermal resilience. Mechanical testing of the coatings on wood showed superior microhardness, scratch resistance, and wear resistance for PDI-based coatings, particularly when combined with polyester polyols. Microscopic surface evaluation and roughness analysis confirmed smoother morphologies and lower crack densities in PDI-polyester coatings. Gloss and water contact angle measurements further demonstrated improved surface uniformity and hydrophobicity for PDI-based coatings. The FTIR spectroscopy validated the chemical integrity and more intense hydrogen bonding for PDI-based coatings. The post-wear spectra indicated chemical oxidation and surface rearrangements in PDI-based systems and mechanical degradation with chain scission for HDI-based coatings. Overall, the study highlights that bio-based PDI trimers can effectively replace fossil-based HDI trimers in PU and PUD coatings without compromising mechanical performance, especially when paired with polyester polyols. These findings support the development of more sustainable polyurethane coatings with enhanced durability and environmental compatibility. Full article

The objective of this study was to investigate the effect of surface disinfectant solutions against COVID-19 on the surface roughness, gloss, and color of removable denture materials. Fifty rectangular metallic specimens made of Co-Cr alloy and fifty disk-shaped specimens made of PMMA were prepared according to the manufacturers’ instructions. Fifty maxillary right central incisors were also included in the study. The above-mentioned specimens were equally divided into five groups (n = 10). Four disinfectant solutions were tested (0.1 wt% NaOCl, 0.5 wt% H₂O₂, 78 wt% ethanol, and 1 wt% Povidone Iodine), and freshly distilled water was used as the control. To simulate clinical practice, each specimen was immersed in the disinfectant solution 15 times. All specimens were marked, and surface roughness, gloss, and color were measured before and after immersion. All roughness parameters (Sa, Sq, Sz, Sc, and Sv) and gloss values before and after immersion were statistically compared. ΔE*ab values were statistically compared with perception and acceptability thresholds according to ISO/TR 28642. No significant differences were identified for surface roughness parameters for all groups tested. All materials demonstrated a significant increase in gloss after aging regime, while only the metallic specimens illustrated ΔE*ab values higher than the acceptability threshold after disinfection with H₂O₂. None of the surface properties deteriorated after exposure to tested disinfectants, and thus, all of them can be effectively implemented in everyday practice. Full article

Cellulose acetate (CA) is a semi-synthetic polymer widely present in modern and contemporary collections, yet its conservation poses major challenges due to its chemical and physical instability. Hydrolytic degradation, acetic acid release, plasticizer loss, and embrittlement compromise both structure and surface, making cleaning particularly difficult. Conventional cleaning methods may cause abrasion, extract additives, or alter gloss. Although hydrogels have shown promise for CA cleaning, the literature remains extremely limited. This study reports a preliminary investigation of gel-based cleaning on Le Rituel (1968), a heavily soiled cellulose acetate (CA) artwork by José Escada. The object’s condition was assessed through visual inspection, pH measurements, volatile acidity testing, and infrared spectroscopy. Cleaning tests were conducted on a CA replica (2006) with superficial soiling and on selected artwork areas. Two gel formulations were evaluated: the biopolymer agar-agar rigid gel and the synthetic viscoelastic poly(vinyl alcohol)-borax (PVAl-Borax) gel. Agar-agar was effective as a first step, reducing superficial soiling and humidifying adherent residues for subsequent removal, while PVAl-Borax was advantageous in the second step, as its viscoelastic properties enabled controlled mechanical action and facilitated the removal of more adherent residues. This case study demonstrates the potential of combined gel systems as versatile tools for CA conservation. Full article