High Translucency Research Articles

Eggshell penetration by Salmonella Typhimurium in table eggs: Examination of underlying eggshell structures by micro-computed tomography and scanning electron microscopy

Horizontal infection of table eggs by food borne, human infection causative agents such as Salmonella is a serious concern for consumers and industry. In this study, we investigated the relationship between eggshell translucency, mammillary layer abnormalities and pore structure using Computed Tomography (CT) and scanning electron microscopy. The effects of eggshell pore structure, size and number on Salmonella Typhimurium penetration was also investigated. The eggs were infected with S. Typhimurium and were incubated at 37°C for 3 or 6days. Micro CT results comparing shell features to shell translucency found that there was a significantly increased incidence of externally branching pores found in the high translucency score eggshell group, and more straight pores found in the low translucency score group. Different pore structures, the total number of pores and the shell thickness do not appear to play a role in the horizontal infection of eggs by the S. Typhimurium strain used in this study. While it is likely that the presence of shell pores is responsible for shell penetration, other unknown shell factors must also play a role, and eggshells with a higher incidence of shell pores are not penetrated at a higher rate.

Effect of fat content and temperature on the translucency of Cheddar cheese

Cheese translucency is influenced by fat content, ripening and temperature and is traditionally determined by CIELAB whiteness. However, translucency is also affected by thickness of materials. The Kubelka-Munk method (K/S) estimates the ratio of absorbance to scatter from whiteness measurements on thin layers of materials above white and black backgrounds. The effect of fat content and temperature on Cheddar cheese translucency was evaluated using K/S and CIELAB methods. Cheddar cheeses varying in fat composition were made and translucency was measured during heating/cooling at 2 and 180 d of ripening. Low fat content in cheese was found to be related to high translucency at <30 °C. At 40 °C, translucency increased due to fat melting. At >60 °C, a reversible protein aggregation led to a reduction of translucency. Translucency increased as cheeses aged. CIELAB and K/S methods were highly correlated; K/S could therefore be useful for estimating cheese translucency.

Effect of Background Color to the Final Color of Four Highly Transparent Ceramics after Veneered

This study aimed to investigate the color value of four kinds of highly transparent ceramics (Zenostar Zirconia, Lava Zirconia, Cercon Zirconia and Upcera Zirconia)after veneered on three different post core materials including noble metal alloy, Co-Cr alloy and composite resin. Highly transparent ceramics after veneered were made into specimens with 10mm in diameter and 1.0mm in thickness. The color of core ceramics after veneered on different post core materials were measured with Color Analyzes. The results showed that their color value were significantly different from each other. Zenostar ZR Translucent and Lava Plus High Translucency Zirconia can be easily affected by the background color because of its high translucency. Therefore, resin post core materials should be selected without cause prosthesis mismatch of colors in clinical work. When making Cerconht full contour zirconia restorations, you could try to use a resin material as a post core material. And selecting precious metals, you had better make it opaque. Upcera zirconia owned a poor relative translucency, when making clinical restorations; you could use any kind of post core materials.

Contrast Investigation on Relative Translucency of Four Ultra-Transparent Dental Zirconia Materials after Veneered

The purpose of this article is to contrast the relative translucency of four ultra-transparent dental zirconia materials after veneered, including Cercon zirconia, Zenostar zirconia, Lava zirconia and Upcera zirconia. All zirconia ceramics were prepared into samples of diameter 10mm and thickness 0.5±0.01mm.The relative translucency of samples were measured with color difference meter and statistically analyzed with SPSS 17.0.This experiment confirms that the existence of statistically significant differences in the relative translucency between different zirconia ceramics. According to the numerical level, the relative translucency of zirconia materials from high to low is Zenostar ZR Translucent&gt;Lava Plus High Translucency zirconia&gt; Cerconht full contour zirconia &gt; Upcera zirconia. Zenostar ZR Translucent and Lava Plus High Translucency zirconia can be used to restore adjacent teeth that are higher translucent, while Cercon ht full contour zirconia and Upcera zirconia is better for molar teeth with poor relative translucency.

Systematic approach to preparing ceramic–glass composites with high translucency for dental restorations

ObjectiveCeramic composites are promising materials for dental restorations. However, it is difficult to prepare highly translucent composites due to the light scattering that occurs in multiphase ceramics. The objective of this work was to verify the effectiveness of a systematic approach in designing specific glass compositions with target properties in order to prepare glass infiltrated ceramic composites with high translucency. MethodsFirst it was necessary to calculate from literature data the viscosity of glass at the infiltration temperature using the SciGlass software. Then, a glass composition was designed for targeted viscosity and refractive index. The glass of the system SiO2–B2O3–Al2O3–La2O3–TiO2 prepared by melting the oxide raw materials was spontaneously infiltrated into porous alumina preforms at 1200°C. The optical properties were evaluated using a refractometer and a spectrophotometer. The absorption and scattering coefficients were calculated using the Kubelka–Munk model. ResultsThe light transmittance of prepared composite was significantly higher than a commercial ceramic–glass composite, due to the matching of glass and preform refractive indexes which decreased the scattering, and also to the decrease in absorption coefficient. SignificanceThe proposed systematic approach was efficient for development of glass infiltrated ceramic composites with high translucency, which benefits include the better aesthetic performance of the final prosthesis.

Evaluation of a novel multiple phase veneering ceramic

ObjectivesTo produce a new veneering ceramic based on the production of a multiple phase glass–ceramic with improved performance in terms of strength and toughness. MethodsA composition of 60% leucite, 20% diopside and 20% feldspathic glass was prepared, blended and a heat treatment schedule of 930°C for 5min was derived from differential thermal analysis (DTA) of the glasses. X-ray diffraction (XRD) and SEM analysis determined the crystalline phases and microstructure. Chemical solubility, biaxial flexural strength (BFS), fracture toughness, hardness, total transmittance and coefficient of thermal expansion (CTE) were all measured in comparison to a commercial veneering ceramic (VITA VM9). Thermal shock resistance of the leucite–diopside and VITA VM9 veneered onto a commercial high strength zirconia (Vita In-Ceram YZ) was also assessed. Statistical analysis was undertaken using Independent Samples t-test. Weibull analysis was employed to examine the reliability of the strength data. ResultsThe mean chemical solubility was 6μg/cm2 for both ceramics (P=1.00). The mean BFS was 109±8MPa for leucite–diopside ceramic and 79±11MPa for VITA VM9 ceramic (P=0.01). Similarly, the leucite–diopside ceramic demonstrated a significantly higher fracture toughness and hardness. The average total transmittance was 46.3% for leucite–diopside ceramic and 39.8% for VITA VM9 (P=0.01). The leucite–diopside outperformed the VITA VM9 in terms of thermal shock resistance.Significance This novel veneering ceramic exhibits significant improvements in terms of mechanical properties, yet retains a high translucency and is the most appropriate choice as a veneering ceramic for a zirconia base core material.

Highly-translucent, strong and aging-resistant 3Y-TZP ceramics for dental restoration by grain boundary segregation

Latest trends in dental restorative ceramics involve the development of full-contour 3Y-TZP ceramics which can avoid chipping of veneering porcelains. Among the challenges are the low translucency and the hydrothermal stability of 3Y-TZP ceramics. In this work, different trivalent oxides (Al2O3, Sc2O3, Nd2O3 and La2O3) were selected to dope 3Y-TZP ceramics. Results show that dopant segregation was a key factor to design hydrothermally stable and high-translucent 3Y-TZP ceramics and the cation dopant radius could be used as a controlling parameter. A large trivalent dopant, oversized as compared to Zr4+, exhibiting strong segregation at the ZrO2 grain boundary was preferred. The introduction of 0.2mol% La2O3 in conventional 0.1–0.25wt.% Al2O3-doped 3Y-TZP resulted in an excellent combination of high translucency and superior hydrothermal stability, while retaining excellent mechanical properties.

The research on optical properties of four all-ceramic veneer materials

To analyze the color parameters and translucency of four frequently-used veneer materials. Forty disc specimens[(1.00±0.01) mm in thickness, 10 mm in diameter] were fabricated according to the manufacturer's instructions with IPS Empress(®) CAD[A2, high translucency (HT)], IPS e.max(®) Press(A2, HT), IPS e.max(®) CAD (A2, HT) and VITABLOCS(®) Mark II (A2) respectively and were divided into Groups A, B, C, D. All of the specimens were ground and polished on a grinding machine. Then color parameters (L*, a*, b*) and transmittance (τ) were measured using spectrocolorimeter and transmissivity testing device. The color parameters of the specimens were compared to the color parameters of A2 shade of Ivoclar Vivadent A-D shade guide. The data were analyzed with one-way analysis of variance (ANOVA), and mean values were compared by the Tukey's test (α = 0.05). There was no statistical difference between the color parameters L*, a*, b* and C*ab of Group A and Group D (P > 0.05). But the color parameters of those two ceramic materials were statistically different from the color parameters of Group B and Group C (P < 0.05). There was no statistical difference between color parameters b* and C*ab of Group B and Group C(P > 0.05). However, the color parameters L* and a* of the two materials were statistically different(P < 0.05). The color differences (ΔE) between Group A, B, C, D and standard A2 were 6.05±0.12, 5.11±0.27, 3.73±0.27, 6.30±0.38 respectively. The transmittances of Group A, B, C, D were (29.69±0.31)%, (25.83±0.36) %, (28.92±0.47)% and (26.94±0.33)% respectively. The color parameters of these four materials are different. Their transmittance are relatively high but statistically different. The color difference (ΔE) between IPS e.max(®) CAD (A2, HT) and standard A2 is lowest among all the groups.

Effect of fiber addition on slow crack growth of a dental porcelain

AimsTo evaluate the effect of the processing method (conventional sintering, S, and heat-pressing, HP) and addition of potassium titanate fibers, PTF, on the microstructure, mechanical properties (flexural strength, σf, and Weibull parameters, m and σ5%), slow crack growth parameters n (stress corrosion susceptibility coefficient), and optical properties (translucency parameter, TP, and opalescence index, OI) of a feldsphatic dental porcelain. MethodsDisks (n=240, Ø12×1mm) of porcelain (Vintage-Halo, Shofu) were produced using S and HP methods with and without addition of 10wt% (conventional sintering) or 5wt% (heat-pressing) of PTF. For the S method, porcelain was sintered in a conventional furnace. In the HP technique, refractory molds were produced by lost wax technique. The porcelain slurry was dry-pressed (3t/30s) to form a cylinder with 12mm (diameter) and 20mm (height), which was heat-pressed for 5min/3.5bar into the mold. Specimens were tested for biaxial flexural strength in artificial saliva at 37°C. Weibull analysis was used to determine m and σ5%. Slow crack growth (SCG) parameters were determined by the dynamic fatigue test, and specimens were tested in biaxial flexure at five stress rates: 10−2, 10−1, 100, 101 and 102MPa/s (n=10), immersed in artificial saliva at 37°C. Parameter n was calculated and statistically analyzed according to ASTM F394-78. Optical properties were determined in a spectrophotometer in the diffuse reflectance mode. ResultsThe highest n value was obtained by the combination of heat-pressing with fiber addition (37.1) and this value was significantly higher than those obtained by both sintered groups (26.2 for control group and 27.7 for sintered with fiber). Although heat-pressing alone also resulted in higher n values compared to the sintered groups, there were no significant differences among them. Fiber addition had no effect on mechanical strength, but it resulted in decreased TP values and increased OI values for both processing methods. Heat-pressing alone was able to reduce the porosity level of the porcelain. ConclusionsAddition of PTF combined with heat-pressing can reduce strength degradation of a dental porcelain compared to sintered materials with or without fibers. Heat-pressing (HP) alone should be considered as a good alternative for clinical cases where high translucency is required.

An original simple technique for diagnosis of Microsporidia using glycerol jelly direct smear.

Microsporidia spp. are obligate intracellular parasites which are very minute with sizes ranging from 1 to 10 μm. They have been increasingly recognized as human pathogens in AIDS and immunocompromised patients, mainly associated with life-threatening chronic diarrhea and systemic disease. For accurate identification of Microsporidia, permanent staining techniques are used to enable the examiner to use the ×100 objective which reveals the important details needed for diagnosis. On the other hand, ×10 and ×40 objectives are of no value in detection of such a minute organism. Until now, there is no study that demonstrates a rapid satisfactory technique for routine examination of wet mount by the oil-immersion lens. Glycerol jelly (GJ) reagent was previously studied for its benefit in fixing the cover slide of direct wet mounts instantly enabling the use of oil-immersion lens in examination that magnifies its role as a rapid technique for direct examination. The aim of this research is to identify Microsporidia by wet mounts immediately, using GJ reagent that enables the examiner to use the ×100 objective and to evaluate GJ wet mount as a method of identification. Glycerol jelly reagent was prepared (7 g gelatin dissolved in 50 ml boiling water was added to 10 ml glycerol) and added to fecal wet mounts stained by iodine and methylene blue. Wet mounts were examined using the ×100 objective. Satisfactory results were achieved in spite of the small size of Microsporidia, as both iodine and methylene blue stained the cytological structures; GJ reagent fixed the cover slide, maintained the high translucency of the films, and enabled the examiner to use the ×100 oil-immersion objective. We also compared fecal wet mounts stained by iodine and methylene blue + GJ with a stool sample stained by permanent stain modified Ziehl-Neelsen without GJ, and we found that fecal wet mounts stained by iodine and methylene blue + GJ were more clear. We concluded that glycerol jelly wet mount is an easy, fast, reliable, and cheap technique for identification of Microsporidia in direct smear, using the ×100 oil-immersion objective.

Ceramic materials for porcelain veneers: Part II. Effect of material, shade, and thickness on translucency

Information regarding the differences in translucency among new ceramic systems is lacking. The purpose of this study was to compare the relative translucency of the different types of ceramic systems indicated for porcelain veneers and to evaluate the effect of shade and thickness on translucency. Disk specimens 13 mm in diameter and 0.7-mm thick were fabricated for the following 9 materials (n=5): VITA VM9, IPS Empress Esthetic, VITA PM9, Vitablocks Mark II, Kavo Everest G-Blank, IPS Empress CAD, IPS e.max CAD, IPS e.maxPress, and Lava Zirconia. VITA VM9 served as the positive control and Lava as the negative control. The disks were fabricated with the shade that corresponds to A1. For IPS e.maxPress, additional disks were made with different shades (BL2, BL4, A1, B1, O1, O2, V1, V2, V3), thickness (0.3 mm), and translucencies (high translucency, low translucency). Color coordinates (CIE L∗ a∗ b∗) were measured with a tristimulus colorimeter. The translucency parameter was calculated from the color difference of the material on a black versus a white background. One-way ANOVA, the post hoc Tukey honestly significant difference, and the Ryan-Einot-Gabriel-Welsch multiple range tests were used to analyze the data (α=.05). Statistically significant differences in the translucency parameter were found among porcelains (P<.001) according to the following rank: VM9>PM9, Empress Esthetic>Empress CAD>Mark II, Everest, e.max CAD>e.max Press>Lava. Significant differences also were noted when different shades and thickness were compared (P<.001). Different ceramic systems designed for porcelain veneers present varying degrees of translucency. The thickness and shade of lithium disilicate ceramic affect its translucency. Shade affects translucency parameter less than thickness.

Effect of heat treatment on the microstructure and properties of lithium disilicate glass-ceramics

The effect of heat treatment on microstructure and properties of SiO2–Li2O–K2O–Al2O3–ZrO2 glass-ceramics was investigated. The glasses were subjected to a multi-stage heat treatment. At the first stage at 650°C, Li2SiO3 was the main crystalline phase of all samples, which had a dimensional change with prolonging the heating time from 3h to 72h. After the second stage treatment at 830°C for 3h, all the Li2SiO3 crystals decomposed and Li2Si2O5 crystals formed with an opposite dimensional change from that of Li2SiO3. These Li2Si2O5 crystals were small, which could contribute to forming high translucency. The third stage at 550°C would release the internal strain and improve samples' bending strength, which could reach up to above 560MPa. The sample treated for 48h at the first stage had the smallest crystals and also obtained a highest real in-line transmission of 29% at 650nm with a thickness of 1.45mm and a bending strength above 581±25MPa.

Effect of varying core thicknesses and artificial aging on the color difference of different all-ceramic materials

Objective. Clinicians should reserve all-ceramics with high translucency for clinical applications in which high-level esthetics are required. Furthermore, it is unclear whether a correlation exists between core thickness and color change. The aim of this study was to examine the effects of different core thicknesses and artificial aging on the color stability of three all-ceramic systems. Materials and methods. Ninety disc-shaped cores with different thicknesses (0.5 mm, 0.8 mm and 1.0 mm) were prepared from three all-ceramic systems, In-Ceram Alumina (IC), IPS e.max Press (EM) and Katana (K). The colors of the samples were measured with a spectrophotometer and the color parameters (L*, a*, b*, ΔE) were calculated according to the CIE L*a*b* (Commission Internationale de L'Eclairage) color system before and after aging. Results. The effects of aging on color parameters were statistically significant (p < 0.001), regardless of core thickness. For all systems, the CIE a* values increased as the thickness of the core increased. Conversely, such increases in core porcelain thickness were correlated with decreasing CIE L* and b* values. Core thickness had a statistically significant effect on color change among the groups. Conclusions. Different core thicknesses (from 1.0–0.5 mm) and artificial aging affected color stability of the all-ceramic materials tested.

Comparative analysis of transmittance for different types of commercially available zirconia and lithium disilicate materials.

PURPOSETranslucency and colour stability are two most important aspects for an aesthetic dental restoration. Glass ceramic restorations are popular amongst clinicians because of their superior aesthetic properties. In the last decade, zirconia has generated tremendous interest due to its favorable mechanical and biological properties. However, zirconia lacks the translucency that lithium disilicate materials possess and therefore has limitations in its use, especially in esthetically demanding situations. There has been a great thrust in research towards developing translucent zirconia materials for dental restorations. The objective of the study was to evaluate and compare the transmittance of a translucent variant of zirconia to lithium disilicate.MATERIALS AND METHODSTwo commercially available zirconia materials (conventional and high translucency) and 2 lithium disilicate materials (conventional and high translucency) with standardized dimensions were fabricated. Transmittance values were measured for all samples followed by a microstructural analysis using a finite element scanning electron microscope. One way analysis of variance combined with a Tukey-post hoc test was used to analyze the data obtained (P=.05).RESULTSHigh translucency lithium disilicate showed highest transmittance of all materials studied, followed by conventional lithium disilicate, high translucency zirconia and conventional zirconia. The difference between all groups of materials was statistically significant. The transmittance of the different materials correlated to their microstructure analysis.CONCLUSIONDespite manufacturers' efforts to make zirconia significantly more translucent, the transmittance values of these materials still do not match conventional lithium disilicate. More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration.

How will surface treatments affect the translucency of porcelain laminate veneers?

PURPOSEThe purpose of this study was to evaluate whether surface treatments affect the translucency of laminate veneers with different shades and thicknesses.MATERIALS AND METHODSA total of 224 disc-shaped ceramic veneers were prepared from A1, A3, HT (High Translucent) and HO (High Opaque) shades of IPS e.max Press (Ivoclar Vivadent) with 0.5 mm and 1.0 mm thicknesses. The ceramics were divided into four groups for surface treatments. Group C: no surface treatments; Group HF: etched with hydrofluoric acid; Group SB: sandblasted with 50-µm Al2O3; and Group L; irradiated with an Er;YAG laser. A translucent shade of resin cement (Rely X Veneer, 3M ESPE) was chosen for cementation. The color values of the veneers were measured with a colorimeter and translucency parameter (TP) values were calculated. A three-way ANOVA with interactions for TP values was performed and Bonferroni tests were used when appropriate (α=0.05).RESULTSThere were significant interactions between the surface treatments, ceramic shades and thicknesses (P=.001). For the 0.5-mm-thick specimens there were significant differences after the SB and L treatments. There was no significant difference between the HF and C treatments for any shades or thicknesses (P>.05). For the 1-mm-thick ceramics, there was only a significant difference between the L and C treatments for the HT shade ceramics (P=.01). There were also significant differences between the SB and C treatments except not for the HO shades (P=.768).CONCLUSIONThe SB and L treatments caused laminate veneers to become more opaque; however, HF treatment did not affect the TP values. When the laminate veneers were thinner, both the shade of the ceramic and the SB and laser treatments had a greater effect on the TP values.

Degree of conversion of a resin cement light-cured through ceramic veneers of different thicknesses and types.

During the cementation of ceramic veneers the polymerization of resin cements may be jeopardized if the ceramics attenuate the irradiance of the light-curing device. The aim of this study was to evaluate the effect of different types and thicknesses of ceramic veneers on the degree of conversion of a light-cured resin-based cement (RelyX Veneer). The cement was light-cured after interposing ceramic veneers [IPS InLine, IPS Empress Esthetic, IPS e.max LT (low translucency) and IPS e.max HT (high translucency) - Ivoclar Vivadent] of four thicknesses (0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm). As control, the cement was light-cured without interposition of ceramics. The degree of conversion was evaluated by FTIR spectroscopy (n=5). Data were analyzed with one-way ANOVA and Tukey's test (α=0.05). Significant differences were observed among groups (p<0.001). The degree of conversion was similar to the control for all light-cured groups with interposition of ceramics of 0.5 mm and 1.0 mm (p>0.05). Among 1.5-mm-thick veneers, IPS e.max LT was the only one that showed different results from the control (p<0.05). At the thickness of 2.0 mm, only the IPS e.max LT and HT veneers were able to produce cements with degrees of conversion similar to the control (p>0.05). The degree of conversion of the evaluated light-cured resin cement depends on the thickness and type of ceramics employed when veneers thicker than 1.5 mm are cemented.

The Use of Newer High Translucency Zirconia in Aesthetic Zone

Loss of anterior tooth causes aesthetic and functional disharmony. Although no restorative material can approach the appearance of intact tooth enamel, glass ceramic, at the increased risk of brittle fracture, can mimic original tooth color better than the other restorative options. The newest zirconia material comes with unparalleled individualization in aesthetics and optimal physical properties. One of the basic principles of tooth preparation is conservation of tooth structure. This clinical report describes the replacement of maxillary and mandibular incisor with latest generation zirconia adhesive fixed partial denture. The authors have achieved unmatched aesthetics with newer high translucency zirconia.

Influence of the interposition of ceramic spacers on the degree of conversion and the hardness of resin cements

This study evaluated: I) the effect of photo-activation through ceramics on the degree of conversion (DC) and on the Knoop hardness (KHN) of light- and dual-cured resin cements; and II) two different protocols for obtaining the spectra of uncured materials, to determine the DC of a dual-cured resin cement. Thin films of cements were photo-activated through ceramics [feldspathic porcelain (FP); lithium disilicate glass-ceramics of low translucency (e.max-LT), medium opacity (e.max-MO) and high translucency (e.max-HT); glass-infiltrated alumina composite (IC) and polycrystalline zirconia (ZR)] with thicknesses of 1.5 and 2.0 mm. DC was analyzed by Fourier transform infrared (FTIR) spectroscopy. Two protocols were used to obtain the spectra of the uncured materials: I) base and catalyst pastes were mixed, and II) thin films of base and catalyst pastes were obtained separately, and an average was obtained. KHN assessment was performed with cylindrical specimens. The results were analyzed by ANOVA and Tukey's test (α= 0.05). The light-cured cement showed higher DC (61.9%) than the dual-cured cement (55.7%). The DC varied as follows: FP (65.4%), e.max-HT (65.1%), e.max-LT (61.8%), e.max-MO (60.9%), ZR (54.8%), and IC (44.9%). The light-cured cement showed lower KHN (22.0) than the dual-cured (25.6) cement. The cements cured under 1.5 mm spacers showed higher KHN (26.2) than when polymerized under 2.0 mm ceramics (21.3). Regarding the two protocols, there were significant differences only in three groups. Thus, both methods can be considered appropriate. The physical and mechanical properties of resin cements may be affected by the thickness and microstructure of the ceramic material interposed during photo-activation.

Translucency of dental ceramics with different thicknesses

The increased use of esthetic restorations requires an improved understanding of the translucent characteristics of ceramic materials. Ceramic translucency has been considered to be dependent on composition and thickness, but less information is available about the translucent characteristics of these materials, especially at different thicknesses. The purpose of this study was to investigate the relationship between translucency and the thickness of different dental ceramics. Six disk-shaped specimens of 8 glass ceramics (IPS e.max Press HO, MO, LT, HT, IPS e.max CAD LT, MO, AvanteZ Dentin, and Trans) and 5 specimens of 5 zirconia ceramics (Cercon Base, Zenotec Zr Bridge, Lava Standard, Lava Standard FS3, and Lava Plus High Translucency) were prepared following the manufacturers' instructions and ground to a predetermined thickness with a grinding machine. A spectrophotometer was used to measure the translucency parameters (TP) of the glass ceramics, which ranged from 2.0 to 0.6 mm, and of the zirconia ceramics, which ranged from 1.0 to 0.4 mm. The relationship between the thickness and TP of each material was evaluated using a regression analysis (α=.05). The TP values of the glass ceramics ranged from 2.2 to 25.3 and the zirconia ceramics from 5.5 to 15.1. There was an increase in the TP with a decrease in thickness, but the amount of change was material dependent. An exponential relationship with statistical significance (P<.05) between the TP and thickness was found for both glass ceramics and zirconia ceramics. The translucency of dental ceramics was significantly influenced by both material and thickness. The translucency of all materials increased exponentially as the thickness decreased. All of the zirconia ceramics evaluated in the present study showed some degree of translucency, which was less sensitive to thickness compared to that of the glass ceramics.

Relationship between Color and Translucency of Multishaded Dental Composite Resins

The aim of the present study was to compare the translucency of different shades of two highly aesthetic multilayered restorative composite resins. In total nine shades from Esthet.X and ten shades from Filtek Supreme composite resins were chosen. Discs of each shade were prepared (N = 3) and light-cured. Total and diffuse transmittance values for each sample were measured. Statistical analysis showed that the opaque dentine shades of both composites were the least translucent and the enamel shades had the highest translucency. There was a significant decrease in translucency from A2 to C2 of regular body shades and also from A4 to C4 of opaque dentine shades of Esthet.X composite resin. Grey enamel shade had a significantly higher diffuse translucency compared to clear and yellow enamel shades. There was a significant decrease in translucency from A2B to D2B and also in diffuse translucency from A4D to C6D shades of Filtek Supreme composite resin. It can be concluded that the color of the composite resins tested in this study had a significant effect on their translucency. Information on the translucency of different shades of composite resins can be very useful for the clinicians in achieving optimal esthetic restorative outcome.