Opaque Shades Research Articles

Thermal performance of shaded roofs: investigating the impact of material properties and efficacy of building performance simulation

This research investigates the thermal performance of shaded roofs in the composite climate of Roorkee, India, by examining four shading materials (three opaque, one translucent) over an unobstructed roof for eight consecutive days. Using ‘Designbuilder’ software simulations and a mathematical model, the study meticulously triangulates experimental, simulated, and modelled data. The hourly temperature profile of the roof under different shades is analysed and the results showed negligible differences among opaque shading materials, while the translucent material significantly altered the roof’s thermal performance due to solar transmittance. Opaque shades reduced peak heat gain through the roof by up to 77% and 71.5% on cloudy and sunny days, respectively, and reduced nighttime heat loss by 40% and 33%, respectively. This research underscores the importance of considering shading material properties in sustainable building design and confirms the reliability of simulation tools. Highlights The study finds that in parasol roofs, the shading material's thermal properties do not impact the roof's thermal performance, but the solar transmittance does. The study also found that opaque shading could reduce the hourly peak heat gain through the roof by up to 77% and 71.5% on a cloudy day and sunny day, respectively, and reduced the nighttime hourly peak heat loss from the roof by up to 40% and 33%, respectively. Despite considering shading elements in BPS tools to be thermally inactive, the tools perform valid energy simulations.

Future indoor overheating risk for urban village housing in subtropical region of China under long-term changing climate

Over the last two decades, China has witnessed a surge in the emergence of urban villages characterized by high building density and significant migrant populations, primarily due to shifts in land use during urbanization. Housings in urban villages with low-cost design strategies, potentially exposing them to indoor overheating risks under climate changes. Given the scarcity of literature analyzing thermal performance of these houses, this study aims to assess the future indoor overheating risk of common urban village house types based on different construction material in subtropical China with two metrics which are Indoor Overheating Hours (IOH) and Indoor Overheating Degree (IOD), and explore effective methods to counter outdoor thermal stress. A four-month on-site measurement was conducted to calibrate the building thermal environment calculation model. Results demonstrate pronounced indoor overheating risks for both selected houses, Traditional Urban Village House (TUVH) and Contemporary Urban Village House (CUVH), particularly under the Representative Concentration Pathways (RCPs) 8.5 scenario. TUVH and CUVH may experience up to 2111 and 4325 overheating hours, respectively, with the IOD reaching 7.1 °C and 10.9 °C. Moreover, employing a global sensitivity analysis, we found that adding opaque shading for external wall is an effective retrofit strategy for TUVH and CUVH. This study contributes to evaluating the thermal performance of urban village houses under long-term climate changes with the findings promoting future retrofit strategy research for urban village houses focusing on housing types and usage pattern of the housings.

The Effect of Feldspathic Thickness on Fluorescence of a Variety of Resin Cements and Flowable Composites

(1) Background: The shade of resin-based materials and ceramic thickness influence the optical color of laminate restorations. The purpose of this study is to evaluate—in vitro—the effect of resin-based cement shade and ceramic thickness on fluorescence of feldspathic laminate veneers; (2) Methods: 180 samples of feldspathic ceramic A2 shade with two different thicknesses (0.5 and 0.8 mm) were obtained. The samples were cemented to composite resin substrates with one of the following materials in different shades (n = 10): resin cement (Variolink Esthetic in Light, Neutral and Warm shades; or RelyX Veneer in B0.5 /white, Translucent and A3 Opaque/yellow opaque shades); flowable composite resin (G-aenial Flo in A2 and A3 shades) or a pre-heated composite resin (Filtek Supreme XTE, A3 body shade). The fluorescence spectra were obtained by means of a spectrofluorometer. Two-way ANOVA, Tukey, and Student’s t-tests were performed (α = 0.05); (3) Results: Fluorescence values were significantly influenced by the resin-based agent tested (p < 0.001), the thickness of ceramic (p < 0.001), and their interaction (p < 0.001). The lowest fluorescence values were achieved by RelyX Veneer resin cement regardless its shade and the ceramic thickness; (4) Conclusions: both the shade of resin-based agent and the feldspathic ceramic thickness influenced the fluorescence of laminate restorations.

Effect of cigarette smoke on aesthetic brackets: an in vitro study.

ABSTRACTObjective: The objective of this study was to evaluate the effect of cigarette smoke (CS) on physical and mechanical properties of ceramic, polycarbonate and alumina ceramic brackets. The null hypothesis tested was that aesthetic brackets would not be influenced by CS. Methods: Ninety aesthetic brackets were allocated to three groups (n = 30): ceramic (GCE), polycarbonate (GCO) and alumina ceramic (GPS). Ten samples of each group were assigned to color and surface roughness analysis, performed before (T0) and after (T1) exposure to CS; and twenty samples were allocated into control and experimental groups (n = 10) (not exposed and exposed to CS, respectively) for shear bond strength test (SBS). Exposure to CS followed an adaptation of the method described by Le Mesurier. Colorimetric reading, surface morphology and roughness, SBS and adhesive remnant index (ARI) were assessed. Statistical analysis comprised independent and paired t-tests, ANOVA/Tukey and Fisher’s exact tests (α = 0.05). Results: Changes were observed in brackets’ color (NBS: GCE = 2.4; GCO = 1.9; GPS = 2.1), surface roughness (ΔRa: GCE = 1.1 ± 0.8 µm; GCO = 1.9 ± 1.5µm; GPS = -0.3 ± 0.1 µm / ΔRz: GCE = 1.4 ± 1.0 nm; GPS = -0.5 ± 0.1 nm); and SBS (GPS - experimental = 221.8 ± 48.6 N) after exposure to CS (p< 0.05). Conclusions: Exposure, in vitro, of aesthetic brackets to CS resulted in changes of color to darker and more opaque shades, surface roughness alterations, and higher SBS values. ARI scores were not associated with exposure to CS.

Judged Beauty of Fractal Symmetries

Fractals are patterns that show self-similarity at different levels of scale. Typically they appear in nature and this degree of similarity is approximate or statistical. However, artificial or exact fractals have also been studied and the advantage of these stimuli is the ability to more carefully control the relationships that occur across various hierarchies. In two experiments we studied the perceived beauty of a novel class of exact visual fractal in which we introduced reflection, rotation, translation, and random symmetries that repeated at a local and global levels. Rotation and reflection were consistently preferred to translation and randomness. Only reflected patterns were preferred at a vertical orientation. For all other symmetries there was no difference in preference between vertical and horizontal. In a second experiment we progressively eliminated the salience of local symmetry through opaque shading . Perceived beauty decreased with an increase in shading . For these patterns greater discriminability of their fractal quality makes them more aesthetically appealing.

Translucency of Cad/Cam Veneers Using Different Internal Relief Spaces and Luting Cement Shades

Statement of Problem: Many studies have investigated translucency of ceramic veneers in association with different trial insertion paste materials.1,2,3. Little information is available on the ef- fect of cement space thickness on the final shade color of glass ceramic, feldspathic and zirconia reinforced glass ceramic veneers. Purpose: The aim of the study is to evaluate translucency of three different CAD/CAM ve- neer materials with different internal relief spaces and different cement shades. Material and Method: Sixty samples were constructed and classified according to the type of materials into three main groups ( I ) IPS e.max CAD MT , ( II ) VITA Vitablocs Mark II and group ( III ) Vita Suprinity (20 samples each). Each group were subdivided into two subgroups (10 samples each) according to the internal relief space (100 µm and 30 µm).The internal relief space was determined based on data from a previous 123 study and available resources. Each subgroup were further subdivided into six classes according to the 4 type of trial cements used : the control class ( glycerine ) and five trial paste class- es according to their shade (Translucent Shade, White Opaque Shade, A1/Light Yellow Shade, A3 Opaque/Yellow Opaque Shade and B0.5/ White Shade (10 sam- ples each) according to shade of the trial cement used. The color test was done using reflectance spectrophotometer device ( Vita Easy shade V). Color coordinates were measured in the body region of all laminate ve- neers with different combinations of laminate veneer material, internal relief space, and trial insertion paste color on composite resin abutment A3 . Results: The consistency of the translucency among the tested specimens was confirmed using a 2-way ANOVA and the Tukey HSD post hoc test (P&lt;.05). The luminous transmittance exhibited a statistically significant dependence on different ceramic restorations with a cad cam veneers in various internal relief space and different cement shades combinations. (P&lt;.05). Conclusions: The underlying color of the tested trial insertion pastes caused color change (?E &gt;3.7) for all ceramic material used in this study.

Morphological and chemical characterization of cambucizeiro fruits

The cambucizeiro (Campomanesia phaea), belonging to the Myrtaceae family, is a native plant of the Brazilian Atlantic Forest. The description of the characteristics of the cambucizeiro fruits is important to support new genetic improvement works and its commercial exploitation, especially regarding the processing of the fruit. The present work aimed to perform the morphological and chemical characterization of the cambucizeiro fruits. Fifty-eight accessions, from different locations in the Atlantic Forest and Serra do Mar in the state of São Paulo, were collected, propagated by seeds and one specimen of each accessory is at the Seedling Production Center in São Bento do Sapucaí (SP). Forty fruits from each access were collected in May and submitted to the following analyses: longitudinal and transversal diameter, total fruit fresh mass, number and mass of seeds, total soluble solids, % citric acid, ratio, firmness, vitamin C and coloration. Fruit conformation varies intensely among accessions. The number of seeds is not a good indicator for the relation with the fruit mass, but the mass of one thousand seeds. Some accessions have high soluble solids content, but, on the other hand, the vast majority have fruits with high acidity. Cambuci is an excellent source of vitamin C. The fruits of the accessions are green in color, persisting an opaque shade when ripe.

Influence of Different Cements on the Color Outcomes of Titanium-Based Lithium Disilicate All-Ceramic Crowns and Peri-implant Soft Tissue.

To evaluate the influence of different cements on the color outcomes of CAD/CAM lithium-disilicate implant crowns cemented to titanium-base abutments utilizing spectrophotometric analysis. A clinical situation with a missing lateral incisor was mimicked using a maxillary plastic model. Titanium-base-supported monolithic lithium disilicate crowns with identical designs were fabricated using a laboratory CAD/CAM system. The crowns were cemented with three provisional cements and with six definitive cements on both nonsandblasted and sandblasted titanium-base abutments for a total of 15 test groups. As a control group, identical crowns were attached with try-in paste on composite die abutments that duplicated the shape of the titanium-base abutments. The colors of the labial surfaces of the crowns and the peri-implant artificial soft tissue were measured with a spectrophotometer and recorded in CIE L*a*b* parameters. Color differences between the test and control groups were calculated as: ΔE = ([ΔL*]2 + [Δa*]2 + [Δb*]2)1/2. Kruskal-Wallis test was used to compare ΔE values across different groups. The median ΔE values reported for crowns cemented with different definitive cements on titanium-base abutments ranged from 1.4 to 2.9 for the crown surface and from 1.7 to 1.9 on the peri-implant artificial soft tissue; when the titanium-base abutments were sandblasted, the respective median ΔE values ranged from 0.8 to 4.0 and from 1.4 to 2.2. Ceramic crowns cemented with Multilink HO 0 cement presented significantly (P < .01) lower ΔE values than the other cement types for the crown surface independent of sandblasting and for the artificial soft tissue surface when the titanium abutments were sandblasted (P = .011). Within the limitations of this study, Multilink HO 0 (Ivoclar Vivadent) cement showed the most favorable masking ability and the most favorable color outcome among the evaluated definitive cements. Cements of more opaque shades appeared in general to be more favorable in terms of masking the gray color of the titanium-base abutments.

Subcell Modeling of Partially Shaded Photovoltaic Modules

Increased photovoltaic installations in densely built-up areas give rise to non-uniform irradiation causing partial shading. Non-uniform irradiation further leads to non-uniform temperature, leading to a reduction in output and the formation of deteriorating hotspots. A detailed model involving subcell level behavior is pivotal in understanding the impact of partial shading. In this paper, such a model is developed that analyzes the output of photovoltaic (PV) modules under different translucent and opaque shades while incorporating the diffused light effects. This model further includes the temperature variation of the module and also captures the bypass diode characteristics. The proposed model is experimentally validated for horizontal, vertical, slant, and patch shading patterns with varying shading intensities. This subcell model is shown to perform better than four existing methods of partial shading output prediction. It improves the output open-circuit voltage and short-circuit current prediction accuracy by more than 10% when compared with the average irradiance-based modeling approach, which is the best among the existing methods. Overall, an output prediction accuracy of more than 93% is achieved for opaque shading and more than 95% for translucent shading. As this paper provides the output of PV modules under partial shading, it finds direct application in partial shading detection, prevention of hotspots, and global maximum power point tracking, thereby enhancing their life and efficiency.

Solar Optiverter—A Novel Hybrid Approach to the Photovoltaic Module Level Power Electronics

In this paper, the concept of an Optiverter is proposed as a novel class of photovoltaic (PV) module level power electronics systems. Functionally, the Optiverter is a hybrid technology that combines the ultrawide maximum power point tracking (MPPT) voltage window of the PV power optimizers with the direct ac connectivity and inherent safety of the PV microinverters. Thanks to the advanced multimode control with variable dc-link and the shade-tolerant MPPT algorithm, the proposed Optiverter ensures efficient energy harvest from the PV module in different shading scenarios. To justify the superiority of the concept, the performance of a 300 W prototype of the PV Optiverter is experimentally compared to that of the industrial microinverters in different operation conditions, including an extreme case with opaque shading of two out of three substrings of the PV module.

The influence of different shades and brands of resin-based luting agents on the final color of leucite-reinforced veneering ceramic

ObjectivesThis study aimed to evaluate the influence of different shades and brands of resin-based luting agents on the final color of a leucite-reinforced veneering ceramic. MethodsThis in-vitro study was done on 36 ceramic discs (IPS Empress I, 11 × 0.5 mm, A2 shade) and 36 cement disks (11 × 0.2 mm) made of Panavia SA Cement Plus (Kuraray Medical Inc.) and Choice2 (Bisco Inc., Schumburg) brands in translucent, universal A2, and opaque shades (n = 6 per each color in each resin cement brand). Color parameters (CIEL*a*b*) of ceramic specimens were calculated without and with each brand/shade of resin-based luting agents by using a spectrophotometer, and put into CIELab formula. The color differences (ΔE) between the two sets of measurements were calculated and analyzed with two-way ANOVA and Tukey’s post hoc test (α = 0.05). ResultsBoth the resin-based luting agent shade (P < 0.001) and brand (P = 0.023) significantly affected the color differences. ΔE values were significantly different between Panavia-opaque and Choice2-opaque (P < 0.001). No significant difference existed between ΔE of the two brands in A2 (P = 0.178) and translucent shades (P = 0.079). The ΔE values of Panavia-A2 was significantly different from the translucent and opaque shades of the same brand. Moreover, the ΔE of Choice2-translucent shade was significantly lower than that of A2 and opaque shades. The ΔE values were higher than the clinically-acceptable threshold in all groups (ΔE > 3.7) except for Choice2-translucent (ΔE = 3.37). ConclusionsThe final color of leucite-reinforced veneering ceramic can be affected by the same shades of resin-based luting agents from different brands and different shades of resin-based luting agents from the same brand.

Color agreement between try-in paste and resin cement: Effect of thickness and regions of ultra-translucent multilayered zirconia veneers.

Background. The current study aimed at identifying the color agreement between try-in pastes and the respective resin cements and investigated the effect of thickness and regions of Ultra-Translucent Multilayered Zirconia Veneers. Methods. A total of 90 cubic zirconia discs were prepared at two different thicknesses (0.5 mm and 0.7 mm) (n=45) in five groups in terms of the shade of the try-in paste and resin cement as follows: Universal, Clear, Brown, White and Opaque. Try-in paste and the respective resin cement were applied between the specimens and composite substrate, respectively, and colorimetric evaluation was carried out using CIE-Lab system. For each specimen, ΔE between the try-in paste and cement was calculated. Data were analyzed with SPSS 17 using Multifactor ANOVA (P<0.05). Results. Multifactor ANOVA results showed that ΔE values were significantly affected by the resin cement shade and the thickness of ceramic veneer (P<0.05). The results showed better shade agreement between the try-in paste and the respective resin cement with thicker ceramic veneers. The results of Tukey HSD revealed that ΔE values for the Clear, Universal and Brown shades were less than those of the White and Opaque shades. Lighter shades exhibited better agreement between the try-in paste and the respective resin cement. Conclusion. Perceptible color difference was found between the try-in pastes and the respective resin cement in most colors investigated. Although, the agreement of the try-in pastes and the respective resin cement was affected by the thickness of zirconia veneers, the different regions of multilayered ultra-translucent zirconia ceramic showed no significant effect.

The selection of brise soleil shading optical properties for energy conservation and glare removal: A case study in Qatar

Energy efficiency in buildings is crucial for the design of sustainable cities, especially in hot climates where demands are high. This study investigates the impact of the shading optical properties on the space energy demands when brise soleil is installed in offices with one fully-glazed façade in four different orientations. The criteria for the selection of best shading property are an office with minimal possible total energy demand and maximum outdoor view without any occupant sensation of visual discomfort caused by glare at any time of the year. In addition, this study examines the feasibility of integrating light dimming control to these offices.A simulation model of an office space with external shading on a fully-glazed façade in one pre-selected orientation was developed and validated. Parametric studies on the shading reflectance and transmittance properties were conducted and their effects on spaces energy demands were observed for Qatar's climate, mimicking a developing country with harshly hot weather conditions. In south-oriented offices, savings caused by the addition of brise soleil reach 36.3%; unreflective or barely transmissive slats are recommended and light dimming control is unjustified. Moreover, unreflective opaque shading without light dimming control is found to be optimal in east and west-oriented offices as it saves 37.2% of the space overall energy demand. In contrary, installing highly-transmissive shadings with light dimming control is justified in north-oriented offices as it keeps full outdoor visual sight and still saves energy of up to 11.6%.

Effect of priming agents on shear bond strengths of resin-based luting agents to a translucent zirconia material

PurposeThe purpose of the present study was to evaluate the effect of priming agents and artificial aging with thermocycling on shear bond strengths of two resin-based luting agents to a translucent zirconia material. MethodsA total of 308 pairs of translucent zirconia disk specimens were divided into seven treatment groups: Alloy Primer (ALP), Clearfil Ceramic Primer Plus (CCP), Meta Fast Bonding Liner (MFB), MR. bond (MRB), Super-Bond PZ Primer Liquid B (PZB), V-Primer (VPR), and an unprimed group (UP). The specimens in each group were bonded with Panavia V5 Universal (UNI) and Opaque shade (OPA). Shear bond strengths (n=11 each) were tested before and after 5000 thermocycles. The data were analyzed with the Kruskal–Wallis test and the Steel–Dwass test. ResultsFor both 0 and 5000 thermocycles, the ALP (47.8 and 41.5MPa, respectively) and CCP (45.8 and 42.3MPa, respectively) groups showed significantly higher bond strengths than other groups in the UNI luting agent. For the OPA luting agent, CCP group (45.8MPa) exhibited the highest pre-thermocycling bond strength in all groups. The ALP (32.4MPa) and CCP (36.5MPa) groups had significantly higher post-thermocycling shear bond strengths than other groups. In several groups, the shear bond strengths of the UNI luting agent were significantly higher than those of the OPA luting agent before and after thermocycling. ConclusionsApplication of priming agents containing hydrophobic phosphate monomer (MDP) yielded the durable bond strengths of resin-based luting agents to a translucent zirconia material.

Color difference of composite resins after cementation with different shades of resin luting cement

The purpose of this study was to evaluate the color difference of nanohybrid and ormocer-based composite resins with different thicknesses when 4 different shades of resin luting cement were used. 56 disc specimens of each composite resin (Aelite aesthetic enamel, Ceram-X mono) with 0.5 and 1mm thicknesses were fabricated. Baseline color measurements were performed using a clinical spectrophotometer. The specimens of each thicknesses of each resin were randomly divided into 4 groups according to the shades of resin luting cement (white/A1, yellow/universal/A3, transparent and white opaque) (n=7). Mixed resin cement was applied onto the resin specimens using a Teflon mold in 0.1mm thickness. Color measurements of cemented composite resin specimens were repeated and color difference (∆E) between baseline and after cementation measurements was calculated. ANOVA and Tukey's test were used for statistical analysis. The opaque shade had significantly increased ∆E values as compared to the other shades (p<0.05). For all shades except white opaque in both thicknesses, ∆E values of aelite aesthetic enamel were higher as compared to Ceram-X mono. There is no significant difference between 2 thicknesses for both resins in terms of ∆E values. The shade of resin cement and the type of the resin affected the final color; however, the thickness of composite resin had no influence on the final color of restoration. Selecting the shade of resin luting cement before cementation of indirect composite laminate restoration is important to achieve final color match.

SPECTROPHOTOMETRIC ANALYSIS OF DISCOLORED ANTERIOR TEETH RESTORED WITH PREFAPRICATED COMPOSITE RESIN VENEERS

INTRODUCTION: Veneers are considered the least invasive most reliable solution for treatment of discolored anterior teeth. Edelweiss system is a polymerized, prefabricated, laser-machined, radiopaque, highly-filled nano-hybrid composite enamel shells with a highly glossy inorganic surface. They have a facial anatomical pattern in the shape of a thin composite shell bonded to labial surface of anterior teeth with composite resin, which allows for easy direct veneering of single and multiple anterior teeth.OBJECTIVES Spectrophotometric analysis of discolored anterior teeth restored with Edelweiss veneer system bonded with different shades of composite resin.MATERIALS AND METHODS: Twenty Edelweiss veneers bonded with different shades of composite resin (A2, opaque white and translucent shades) to dies of different shades. Specimens were divided into four groups, each group consists of five specimens, according to the shade of the bonding composite resin used and the shade of the dies. Spectrophotometer was used to evaluate the effect of using different shades of the bonding composite on the final shade of the restoration. Also, to assess the light reflection, transmission and absorption of the Edelweiss Veneer System.RESULTS: The L*a*b* coordinates values of the Edelweiss Veneer Systems were affected by the shade of bonding composite (P<0.05). The use of an opaque bonding composite resulted in an increase of the color coordinates a*, b*, L*, producing the greatest effect on color change, light transmission and light reflection (P<0.05). Light absorption values of the specimens were not affected by the shade of the bonding composite. CONCLUSIONS: On using Edelweiss veneer system, the greatest color shifts and change in light transmission and light reflection were obtained when using opaque shade composite for bonding of the veneers to the substrates. While light absorption was of a non-significant value among the groups.

DIGITAL SPECTROPHOTOMETER EVALUATION OF THE INFLUENCE OF SCREW COLOR AND ACCESS HOLE FILL ON THE COLOR OF SCREW- RETAINED IMPLANT CROWNS

Statement of problem: Although screw-retained implant crowns are commonly preferred by clinicians, there remain a limited number of studies on how color affected by screw color and access hole fill. purpose: The purpose of this study was to determine the influence of screw color, opaque shade and composite thickness on the color of screw-retained implant crowns with use of digital spectrophotometer. materials and methods: eighty specimens were divided into two groups ,gray group (pure titanium) and golden-colored group (anodized titanium) which used as two backgrounds. Composite discs with 1mm, 2mm,0.5mm opaque+0.5mm composite and 0.5mm opaque+1.5mm composite were fabricated. Titanium specimens and composite discs were placed into a collective mold in various tested groups for color measurements. reSultS: Quantitative in concern to clinical color matching tolerance, It was found that, group 4A and 4B recorded the lowest ∆E as they could not detected by human eyes. Quantative color matching evaluation showed, no significant differences between gray and golden colored titanium(background), (P >0.05) while golden colored titanium gave higher ∆E than grey titanium group. For grey titanium; it was found that Group (4A) was the lowest ∆E value (1.20±0.4), followed by Group(2A) (4.00±1.3∆E), then Group (3A) (5.55±1.8 ∆E)while Group (1A) was the highest (7.6±2.53∆E) The difference in color change was significantly where (P= 0.001<0.05). For golden colored titanium; it was found that Group(4B) recorded the lowest ∆E value (1.15±0.38) followed by Group (2B)(3.65±1.26∆E) then Group (3B) (4.15±1.3∆E) while Group (1B) was the highest (5.55±01.8∆E). The difference in color change was significantly where (P= 0.0001<0.05). conclusion: composite thickness and opaque shade composite affected ∆E values (p 0.05) of the color of final restoration. clinical implications: Screw color and access hole fill play an important role on the color of screw-retained implant crowns. In present study, regardless the implant color, the use of 0.5mm opaque composite covered by 1.5 mm composite resin affected the color of final restoration significantly.

Radiology’sLegacy: Rummaging through the Attic

Early articles in Radiology are based on conventional radiography and provide the foundation for both the way we think about extracting diagnostically important information from images and the spectacular technologic achievements in the decades that followed; therefore, we decided to include in this issue of Radiology a pictorial essay of select figures and our thoughts on the articles themselves to give a taste of the beginnings of so many of our current imaging and research activities.

Effect of Ultraviolet Aging on Translucency of Resin‐Cemented Ceramic Veneers: An In Vitro Study

The aim of this in vitro study was to evaluate the translucency of ceramic veneers cemented with light- or dual-cured resin cements after accelerated aging. A total of 392 specimens were made of shade A1 with 0.5- and 1.0-mm thickness. Light-cured RelyX Veneer and dual-cured Maxcem Elite and Variolink II resin cements were applied on the porcelain discs with a thickness of 0.1 mm. Translucency parameter (TP) values of the ceramic veneers after cementation and UV aging test were evaluated. Statistical analyses were done with ANOVA and Tukey's tests and paired sample t-test (p < 0.05). All the resin cements affected the TP values of 0.5-mm-thick ceramic, while RelyX Veneer Tr (TP = 11.15; p = 0.608), Variolink II Tr (TP = 10.98; p = 0.55), and Maxcem Clear (TP = 11.81; p = 0.702) did not affect the translucency of 1-mm-thick ceramics (TP = 11.38). The aging process affected TP values of both ceramics and cemented ceramics, as the TP values decreased after aging. Among the TP values of opaque shade resin cements, there were significant differences between the "ceramic," "ceramic + RelyX Veneer WO," "ceramic + Variolink II WO," and "ceramic + Maxcem WO" variables for both 0.5 and 1 mm thicknesses (p < 0.05). There were no significant differences between "ceramic," "ceramic + RelyX Veneer Tr," "ceramic + Variolink II Tr," and "ceramic + Maxcem Clear" variables at 0.5 mm thickness, and there were no significant differences between "ceramic," "ceramic + RelyX Veneer Tr," and "ceramic + Variolink II Tr" variables after aging (p > 0.05). The TP of the same color of resin cements varied related to the type or brand. Aging caused both the ceramics and cemented ceramics to become more opaque.

Principal component analysis for dental shade color

ObjectivesConventional 3-dimensional color spaces such as L*a*b* or L*C*h have a limitation in that colors of materials can only be separated on the same hyperplane. Therefore, it would be useful to find appropriate axes for dental color analysis by analyzing spectral data itself, rather than conventional 3-dimensional color spaces. MethodsHyperspectral data are detailed color spectra with narrow spectral bands over a continuous spectral range. We acquired hyperspectral data of the shade guides without specular reflection, and standardized them as reflectance data. Then, reflectance data were weighed by luminous efficiency function, and used in principal component analysis (PCA). Principal components (PCs) and their contribution, and values of respective shades to respective PCs were calculated as PC scores. ResultsCumulate contribution rate of 1st to 3rd PCs were approximately 100%, which meant shade colors were very similar to each other. Respective PCs showed specific figures, and values of shades showed sequences unique to each PC, which were independent of each other; values to the 1st PC showed gradual changes with change in shade numbering, values to the 2nd PC showed relatively high scores on opaque shades, values to the 4th PC showed lower scores on B and C group shades, and values to the 6th PC showed differences between manufacturers. SignificanceUsing PCA, we could find axes independent of the conventional 3-dimensional color spaces. These axes reflected certain changes which are not detected on conventional color spaces. Our methods are taking into account color matching under any illumination by focusing on the spectra themselves, and we can discuss about components of the teeth from spectra of resulting principal components. By applying our method to conventional systems, it would help diagnose color differences of dental materials.