Search Results (25)

This study evaluated the effect of acidic environment and tooth brushing on the color stability and translucency of stained 3D-printed ceramic-reinforced composite (CRC) resins for indirect restorations and hybrid prostheses. Twelve specimens were prepared from each 3D-printing resin material: Ceramic Crown (CC), OnX (ONX), and Tough 2 (T2), and one CAD/CAM milling resin, Lava Ultimate (LU). After preparation, all specimens were stained, then immersed in either water or citric acid. Subsequently, the specimens underwent simulated tooth brushing for 3650 cycles. Color stability (ΔE) and translucency parameter (TP) were measured using a spectrophotometer. Data were analyzed using ANOVA, post hoc Tukey tests, and independent Student t-tests (α = 0.05). Material type, immersion medium, and their interaction did not significantly influence the mean ΔE (p > 0.05). The lowest ΔE value was for LU in acid (ΔE = 1.11 ± 0.39), and the highest for T2 in water (ΔE = 2.09 ± 1.47). Except for ONX and LU in acid, all materials had ΔE values above the perceptibility threshold (ΔE = 1.2). The mean TP was significantly affected by material type, immersion medium, and their interaction (p < 0.05). The lowest TP value was for group CC in acid (0.91 ± 0.26); the highest was for group LU in acid (6.24 ± 0.56). After immersion and subsequent tooth brushing, TP values decreased for all materials. Exposure to an acidic environment and tooth brushing did not affect color stability but significantly reduced translucency. Both the 3D-printed CRCs and milled resin material displayed comparable color stability below clinically acceptable thresholds, though the translucency of 3D-printed materials remained lower compared to milled material. Full article

This study aimed to assess the effect of acidic storage and simulated brushing on the translucency and color stability of 3D-printed resins for prosthodontic applications. Three 3D printed resin materials—Ceramic Crown (CC), OnX (ONX), and Tough 2 (T2)—were compared with a CAD/CAM milled nano-ceramic resin material (Lava Ultimate, LU). Twelve specimens were fabricated from each material and were allocated into two groups based on the storage medium (water or citric acid), followed by simulated tooth brushing for 3650 cycles. The specimens’ translucency (TP) and color stability (ΔE) were determined using a spectrophotometer. The data was compared using ANOVA, independent student t-tests, and a post hoc Tukey test (p < 0.05). Multiple comparisons of mean differences in TP revealed significant differences between the tested materials (p < 0.001), except for groups CC and ONX. Irrespective of the groups, all materials showed decreased TP values after simulated tooth brushing. Regarding color stability, CC (0.66 ± 0.42) and T2 (1.40 ± 0.34) in acid demonstrated the least and greatest color changes, respectively. The ΔE did not vary between the materials or between the storage media (p > 0.05). Except for T2 and LU in water, the other materials showed ΔE values below the perceptibility threshold of 1.2. The material type and storage media affected the translucency of the tested materials. However, regardless of the material type and storage media, there was no discernible impact on the color change of the tested materials. Full article

Shitsukan, which encompasses the perception of roughness, glossiness, and transparency/translucency, represents the comprehensive visual appearance of objects and plays a crucial role in accurate reproduction across various fields, including manufacturing and imaging technologies. This study experimentally examines the impact of the pixel–aperture ratio on the perception of roughness, glossiness, and transparency. A visual evaluation experiment was conducted using natural images presented on stimuli with pixel–aperture ratios of 100% and 6%, employing an RGB sub-pixel array. The results demonstrated that the pixel–aperture ratio significantly affects the perception of glossiness and transparency, with the 100% pixel–aperture ratio producing a statistically significant effect compared to the 6% condition. However, roughness perception varied substantially among the observers, and no statistically significant effect was observed. Nonetheless, when comparing two observer clusters identified through clustering analysis, the cluster favoring the 100% pixel–aperture ratio exhibited “Huge” effect sizes for all perceptual attributes. Additionally, the findings indicate that the degree of influence of pixel–aperture ratio on glossiness and transparency is not constant and can vary depending on individual observer differences and image characteristics. Full article

(1) Background: The intra-oral behavior of clear thermoplastic dental materials can be influenced by various intrinsic and extrinsic factors. Aim: The purpose of this in vitro study was to evaluate the optical properties, color changes and whiteness variations of four thermoplastic polymers used for dental appliances, in a simulated oral environment. (2) Methods: Customized thermoformed specimens of four PETG thermoplastics were selected and investigated in this study: Leone [L], Duran [D], Erkodur [E] and Crystal [C]. The thermoplastic samples were divided into three groups related to pH values (neutral, acidic and basic). A period of 14 days was simulated. Five stages resulted: I. dessicated specimens; II. hydrated in artificial saliva; III. subsequent desiccated; IV. artificial aged; V. further dessicated. Optical CIE L*a*b* coordinates were determined and optical properties, like TP (translucency), OP (opalescence) values, color differences ΔE-NBS, white indexes in dentistry WI_D and white index differences ΔWI_D were calculated for all stages of the study, for each group of the materials. Statistical analyses were performed. (3) Results: Optical properties of PETG clear thermoplastic materials, like TP and OP, increase in a simulated oral environment and the changes become significant after artificial aging. Related to pH values, the optical behavior between the materials is significantly different. During artificial aging, the tested materials behave significantly differently in terms of optical properties. (4) Conclusions: After the simulated period of 14 days, TP and OP values increase, with a migration of the color towards red and yellow. Color changes in some cases even reach the level of extremely marked. Whiteness increases, and the differences are mostly perceptible, but partially exceed the limit of acceptability. Full article

Objectives: This randomized clinical trial evaluated the microbiological efficacy and the ergonomic impact of three prototypes of a device to reduce aerosol dispersion during dental procedures. Methods: Sixty patients undergoing dental care using high-speed turbines and/or ultrasonic tips were randomly assigned to 4 groups (n = 15): CG: control group, with standard personal protective equipment (PPE); G1: PPE + acrylic device (AD) with aspiration; G2: PPE + AD without aspiration; and G3: PPE + polyvinyl chloride device. The device prototypes consisted of a rigid translucent acrylic structure (G1 and G2), or a rigid PVC tube structure surrounded by layers of translucent flexible PVC films (G3), adjusted to the dental chair, involving the patient’s head, neck and chest. The main outcome was the microbiological analysis (mean Δ of CFU at 10 different sites), and the secondary outcome was the ergonomic evaluation (questionnaire to dentists and patients). Results: The final sample comprised 59 participants (mean age 38.6 ± 11.4 years, 55.2% male). The overall mean time for dental procedures was 32.4 ± 16.9 min, with no differences between groups (p = 0.348). Microbiological analyses showed that the use of the device significantly reduced contamination in the light reflector (01.46 ± 4.43 ΔCFU in G2 vs. 19.25 ± 36.50 ΔCFU in CG; p = 0.028), apron (09.11 ± 12.05 ΔCFU in G3 vs. 21.14 ± 43.41 ΔCFU in GC; p = 0.044), and face shield (08.80 ± 32.70 ΔCFU in G1 vs. 56.78 ± 76.64 ΔCFU in the GC; p = 0.017). The device was well accepted by patients and increased the dentists‘ perception of safety and protection (p < 0.001), but significantly decreased ergonomics related to the clinical view, space, agility and access to the patient, and ease of performing procedures (p < 0.001). Conclusions: The tested device can be an additional tool for infection prevention and control in dentistry, not only during the COVID-19 pandemic, but also for the control of future infectious diseases and epidemics. Full article

This study aimed to investigate the effects of shade, thickness, and the application of an opaquer on the masking ability and translucency of direct gingiva-colored giomer. Five shades of giomer, namely Gum-Light-Pink, Gum-Dark-Pink, Gum-Brown, Gum-Violet, and Gum-Orange, were evaluated at thicknesses of 0.5, 1.0, 1.5, and 2.0 mm. Color measurements were obtained using a spectrophotometer against white, black, and giomer backgrounds. The results were analyzed using the CIEDE2000 color-difference formula and interpreted based on the 50:50% thresholds for excellent perceptibility (ΔE₀₀ < 1.1) and acceptability (ΔE₀₀ < 2.8). Measurements were repeated after applying an opaquer. Acceptable masking ability was achieved at 0.5 mm for all shades. Excellent masking ability was achieved at 1.5 mm for all shades, except Gum-Brown, which required 1.0 mm. The opaquer increased masking ability in all specimens. Translucency decreased as thickness increased (p < 0.0001). Gum-Brown and Gum-Light-Pink, as well as Gum-Orange and Gum-Dark-Pink, demonstrated similar translucency at 0.5, 1.0, and 1.5 mm (p > 0.05). After applying the opaquer, there were no statistically significant differences in translucency among shades at 1.5 mm and 2.0 mm (p > 0.05). In conclusion, increasing thickness improved masking ability but reduced translucency of gingiva-colored material. The opaquer further enhanced masking ability and reduced translucency. The clinical significance of these results are that gingiva-colored restorations mask discolored tooth defects in the pink aesthetic area with minimal 0.5 mm tooth preparation, achieving acceptable results. The addition of an opaquer enhances masking ability for excellent outcomes. Full article

Optical characteristics and microstructure of multilayered zirconia with different yttria contents in each layer can be influenced differently with a layer after speed sintering. The layer-wise translucency and opalescence of dental zirconia (E.max, E.max ZirCAD prime; Cercon, Cercon ht ML) after conventional (control) and speed sintering were analyzed using a spectrophotometer (n = 5). Specimens were subjected to microstructural analyses (n = 2) using field-emission scanning electron microscopy (FE-SEM) and phase analyses (n = 1) using high-resolution X-ray diffraction (HRXRD) and Rietveld refinement. The translucency parameter (TP) and opalescence parameter (OP) were analyzed using a 3-way ANOVA, followed by Scheffé’s post hoc test (α = 0.05). The average grain size was analyzed using the Welch’s t-test and Kruskal–Wallis test, followed by the Bonferroni–Dunn post hoc test (α = 0.05). Changes to the TP and OP after speed sintering were only observed in the dentin layers. Although the TP of E.max increased (p < 0.05), the difference was below the 50:50% perceptibility threshold (ΔE₀₀ = 0.8). The OP of E.max decreased slightly, whereas that of Cercon increased slightly (p < 0.05). The microstructure and phase fraction of both zirconia barely changed. Therefore, speed sintering is considered to have a negligible clinical impact on the optical characteristics and microstructure. Full article

Distinguished from conventional lighting, the LED vertical surface light source (VSLS) is directly exposed to human view, and the effects of which form it takes on visual perception are non-negligible. In the current discomfort glare evaluation system, the solid angle and the position index, which represent the relative relation between the glaring light source and human visual field, are not completely applicable for large-area VSLS, and hence are awaiting supplementation and modification. In this study, a physical experimental setup was established to conduct an evaluation experiment on discomfort glare, employing an LED display and white translucent frosted film to simulate vertical surface light sources (VSLS). The experiments were arranged with 21 VSLS shapes (comprising 3 areas and 7 length-to-width ratios) and 11 mounting positions. Subjective ratings and four eye-movement data parameters—namely, the change rate of pupil diameter (CRPD), mean saccadic amplitude (SA), blinking frequency (BF), and saccadic speed (SS)—were collected from 24 participants under each working condition using the Boyce Evaluation Scale and eye tracking techniques. The main results of this study are the following: (a) CRPD is the most appropriate eye-movement index for characterizing VSLS glare perception; (b) The area of the VSLS is the primary shape element influencing discomfort glare. Furthermore, with the same surface area, the lateral view angle (LaVA) and the longitudinal view angle (LoVA) perceived by the human eye also impact glare perception; (c) A functional equation between the VSLS area, LaVA, and LoVA to the borderline luminance between comfort and discomfort (BCD luminance) is fitted; (d) Based on the eccentric angle and the azimuthal angle, a modified position index P’ is proposed to represent the relative position of the VSLS in the visual field, and the ratio function of BCD luminance of the VSLS at non-central positions and the central position is fitted. Full article

The appearance of a surface depends on four main appearance attributes, namely color, gloss, texture, and translucency. Gloss is an important attribute that people use to understand surface appearance, right after color. In the past decades, extensive research has been conducted in the field of gloss and gloss perception, with different aims to understand the complex nature of gloss appearance. This paper reviews the research conducted on the topic of gloss and gloss perception and discusses the results and potential future research on gloss and gloss perception. Our primary focus in this review is on research in the field of gloss and the setup of associated psychophysical experiments. However, due to the industrial and application-oriented nature of this review, the primary focus is the gloss of dielectric materials, a critical aspect in various industries. This review not only summarizes the existing research but also highlights potential avenues for future research in the pursuit of a more comprehensive understanding of gloss perception. Full article

Vision-based perception modules are increasingly deployed in many applications, especially autonomous vehicles and intelligent robots. These modules are being used to acquire information about the surroundings and identify obstacles. Hence, accurate detection and classification are essential to reach appropriate decisions and take appropriate and safe actions at all times. Current studies have demonstrated that “printed adversarial attacks”, known as physical adversarial attacks, can successfully mislead perception models such as object detectors and image classifiers. However, most of these physical attacks are based on noticeable and eye-catching patterns for generated perturbations making them identifiable/detectable by the human eye, in-field tests, or in test drives. In this paper, we propose a camera-based inconspicuous adversarial attack (AdvRain) capable of fooling camera-based perception systems over all objects of the same class. Unlike mask-based FakeWeather attacks that require access to the underlying computing hardware or image memory, our attack is based on emulating the effects of a natural weather condition (i.e., Raindrops) that can be printed on a translucent sticker, which is externally placed over the lens of a camera whenever an adversary plans to trigger an attack. Note, such perturbations are still inconspicuous in real-world deployments and their presence goes unnoticed due to their association with a natural phenomenon. To accomplish this, we develop an iterative process based on performing a random search aiming to identify critical positions to make sure that the performed transformation is adversarial for a target classifier. Our transformation is based on blurring predefined parts of the captured image corresponding to the areas covered by the raindrop. We achieve a drop in average model accuracy of more than $45\%$ and $40\%$ on VGG19 for ImageNet dataset and Resnet34 for Caltech-101 dataset, respectively, using only 20 raindrops. Full article

We propose a method of reproducing perceptual translucency in three-dimensional printing. In contrast to most conventional methods, which reproduce the physical properties of translucency, we focus on the perceptual aspects of translucency. Humans are known to rely on simple cues to perceive translucency, and we develop a method of reproducing these cues using the gradation of surface textures. Textures are designed to reproduce the intensity distribution of the shading and thus provide a cue for the perception of translucency. In creating textures, we adopt computer graphics to develop an image-based optimization method. We validate the effectiveness of the method through subjective evaluation experiments using three-dimensionally printed objects. The results of the validation suggest that the proposed method using texture may increase perceptual translucency under specific conditions. As a method for translucent 3D printing, our method has the limitation that it depends on the observation conditions; however, it provides knowledge to the field of perception that the human visual system can be cheated by only surface textures. Full article

The use of lubricants during restorative procedures is a clinically common practice to alleviate the stickiness of resin-based composite (RBCs) materials and to improve its handling. This study evaluated the effects of three modeling liquids (ML) and one universal adhesive (UA) used as lubricants during composite layering on the color stability and translucency of RBCs. Methods. The following materials were applied between every 1 mm RBC layer (total restoration height of 4 mm): GC modeling liquid (GCML, GC Corporation, Tokyo, Japan), composite wetting resin (UPWR, Ultradent Products, South Jordan, UT, USA), Bisco modeling resin (BSMR, Bisco Inc., Schaumburg, IL, USA) as an ML and Clearfil Universal Bond Quick (KUBQ, Kuraray Noritake Dental, Tokyo, Japan) as a UA. Lubricant-free specimens were used as the control. Color coordinates (L*, a* and b*) were recorded at baseline and after a simulation of 1 month of coffee consumption. Data were analyzed using ANOVA and a post hoc Tukey test (p < 0.05). Results. All lubricants induced a color change higher than the perceptibility threshold (ΔE00 > 0.81). GCML showed the highest color stability. The use of KUBQ resulted in significantly higher a* values (p = 0.001) at baseline and after staining. KUBQ and UPWR significantly influenced the color stability (ΔE00, p = 0.0001) after staining, overcoming the clinical acceptability threshold (ΔE00 > 1.77). Conclusions. The use of lubricants may affect color stability at baseline and after simulation of staining. Translucency was not affected at baseline nor after staining. Clinical Significance. Clinicians should be aware that some lubricants may affect color stability, even at baseline. Full article

The colour properties of resin luting agents (RLAs) can influence the aesthetic of an indirect restoration. This in vitro study aims to evaluate the colour stability and translucency of RLAs cured using two different protocols by means of a spectrophotometer. Six RLAs were investigated: Enamel Plus Flow (MF), Enamel Plus (MH), light-cure Nexus Third Generation (NX3L), dual-cure Nexus Third Generation (NX3D), RelyX Veneer (RXL) and RelyX Ultimate (RXD). The samples were randomly divided into two groups (n = 5) according to the curing protocol used: the traditional protocol (P1), in which the samples were cured for 40 s, and the step luting protocol (P2), in which samples were cured for 5 s. Then, after 20 s, they were cured again for an additional 40 s. Colour changes and differences in translucency were calculated before (t0) and 1 day (t1) and 7 days (t7) after immersion of the samples in distilled water. Data were analysed using one-way ANOVA, Tukey’s test for multiple comparisons and a t-test for paired comparisons (α = 0.05). The colour and translucency of the RLAs changed between t0 and t7 (p < 0.05). In particular, only RXD showed a visually perceptible difference in colour and translucency between P1 and P2 (p = 0.00). The results of this study suggest that, except for RXD, the curing protocol does not affect the colour or translucency of the tested RLAs, even if all these materials underwent perceptible changes in colour and translucency. Full article

Facial prosthetics are currently constructed of materials that are far from optimal; superior materials with a “skin-like” feel are required. In this study, the property changes brought about by the consecutive additions of hydrophobic- and uncoated nano-SiO₂ to polydimethylsiloxane (PDMS) are assessed, and the alterations are compared with those observed for conventional submicron SiO₂-filled materials. In sequence, 0%, 0.5%, 5%, 10%, and 15% by weight of each filler type were successively added to vinyl-terminated PDMS. Tensile, tear, Durometer hardness, translucency, and viscoelastic properties were assessed, and hardness and translucency were further measured after 3000 h of outdoor weathering. The results showed that 15% coated nano- SiO₂-filled PDMS materials given the highest tensile strength, elastic modulus, storage modulus, loss modulus, tear strength, and durometer hardness (p < 0.05), whereas 15% submicron coated SiO₂-filled materials displayed the highest failure strain and translucency parameter (p < 0.05). Only 10%- and 15%-filled submicron SiO₂ PDMS materials were altered by outdoor weathering; nevertheless, the increases were assessed to be too small to be clinically perceptible. As increased filler levels provided protection against solar radiation, heat, and moisture, only unfilled and 0.5%-filled PDMS formulations discolored from weathering. 15%-filled superhydrophobic-coated nano- SiO₂-filled PDMS was found to produce the strongest, most tear-resistant, and least translucent materials, but it also produced materials with limited stretchability and high hardness, which were regarded to be downsides for creating a “skin-like” feel. Full article

The aim of this study was to evaluate the effects of at-home and in-office bleaching agents on esthetic CAD-CAM materials after red wine immersion by measuring their optical properties. Sixty specimens were prepared out of three esthetic CAD-CAM materials: Vita Enamic, Celtra Duo, and Ceresmart (n = 20). All specimens were immersed in a red wine solution, and color measurements were performed. Specimens were randomly divided (n = 10) according to the bleaching procedure (in office, at home), bleaching durations were set to 3 time points, and color measurements were performed. According to the Commission Internationale de l’Eclairage (CIE) L* a* b* parameters, CIEDE2000 color differences (ΔE₀₀), translucency parameters (TP₀₀), and whiteness index values (ΔWI_D) after wine staining and after bleaching were calculated. Data were analyzed using the Mann–Whitney U-test, the Kruskal–Wallis test, and a two-way analysis of variance (ANOVA) (α = 0.05). ΔE₀₀, ΔTP₀₀, and ΔWI_D decreased with an increase in bleaching treatment. ΔE₀₀ after the final bleaching treatment of in-office bleaching ranged from 1.7 to 2.0, whereas those of in-office treatment ranged from 0.4 to 1.1. All ΔTP₀₀ and ΔWI_D after the final treatment were below the 50:50% perceptibility thresholds (ΔTP₀₀ < 0.6, and ΔWI_D < 0.7). Significant differences in ΔE₀₀, ΔTP₀₀, and ΔWI_D among esthetic CAD-CAM materials were found between CD and CE. In the present study, color recovery after at-home and in-office bleaching appeared to be material-dependent. In-office bleaching showed more effective recovery comparing to at-home bleaching. Full article