High Translucency Research Articles

Translucency and color stability of advanced lithium disilicate ceramic material: An in vitro study

Abstract Context: The dental restoration can closely resemble the tooth structure around it when the color and translucency are the right combination. Color stability and translucency are critical factors influencing the optical blending of restorations with natural dentition, enhancing their overall esthetics. Aim: This study aimed to compare the translucency and color stability of advanced lithium disilicate (ALD) ceramic material in comparison to conventional lithium disilicate ceramics. Materials and Methods: Eighty specimens, measuring 12 mm × 14 mm, were fabricated from two types of ceramics: lithium disilicate glass-ceramic (LDS) and ALD. Two types were used for each material, High translucency (HT) and Medium translucency (MT). The samples were divided into 4 groups (n = 20) based on the material and the translucency. Each group was subsequently separated into two additional subgroups based on thickness, specifically 0.5 and 1.0 mm (n = 10). The translucency parameter (TP) was determined by employing a spectrophotometer to measure color on both white and black backgrounds. The experiment involved subjecting samples with a thickness of 1 mm to a total of 10,000 thermocycles, followed by immersing them in coffee for 12 days. Color change (ΔE) was calculated using CIELAB color coordinates at the initial state, as well as after the application of TC and immersion. Results: A significant difference in TP existed between LDS (18.16 ± 2.149) and ALD (15.115 ± 0.877) for 0.5 mm thickness (P < 0.05). Color change for both materials was perceivable above ∆E 1.2. Only ALD MT showed ∆E 3.03 above the acceptability threshold. Conclusion: The translucency of LDS was more than ALD at a thickness of 0.5 mm. In both materials, the color change was above the perceptibility threshold but within the clinical acceptable limits except for ALD MT which had a color change above the clinical acceptability threshold.

An In Vitro Assessment of the Shear Bond Strength of Alkasite Restorative Material in Primary Molars Compared with Glass Ionomer and Resin-Modified Glass Ionomer Restorations.

(1) Background: Alkasite is a novel restorative material that has attracted interest in recent years because of its distinctive characteristics, including its high translucency and excellent biocompatibility. It is comparable to glass ionomer cement (GIC) and resin-modified glass ionomer cement (RMGIC) due to its fluoride-release ability and usage in esthetically concerned areas. This study aimed to assess the shear bond strength (SBS) of Alkasite restorative material in comparison with GIC and RMGIC (2) Methods: The study sample included 120 extracted sound primary molars and was randomly split into three groups, including group 1: RMGIC; group 2: Alkasite; and group 3: GIC. Each group was then sub-grouped into immediate and delayed loading. SBS was measured for each group using a universal testing machine. One-way analysis of variance with Tukey's post hoc test and an independent t-test were used for statistical analyses (3) Results: The immediate SBS was higher in Alkasite, followed by RMGIC and GIC, with means of 10.84 ± 1.96, 10.64 ± 1.74, and 6.09 ± 1.75, respectively. However, there was no significant difference between Alkasite and RMGIC (p = 0.94), whereas RMGIC and Alkasite showed significantly higher values than GIC, with p < 0.0001. Regarding delayed SBS, no significant difference was noted between Alkasite and RMGIC (p = 0.14), whereas both showed significantly higher values than GIC, with mean values of 6.30 ± 1.44, 5.556 ± 1.38, and 3.29 ± 0.61, respectively (p < 0.0001). (4) Conclusions: Our findings show that RMGIC and Alkasite have comparable outcomes to each other and better outcomes when compared with conventional GIC.

Colorimetric changes of zirconia-reinforced lithium disilicate with varied thicknesses under UV aging conditions

Background. Zirconia-reinforced lithium disilicate (ZLD) is a promising material for esthetic dental restorations due to its strength, translucency, and color stability. However, its durability under accelerated aging conditions needs further investigation. The present in vitro study evaluated the effect of UV accelerated aging on the translucency and color stability of ZLD at varying thicknesses, using IPS e.max Press (LD) as a reference. Methods. Seventy-two samples were divided into two groups: high translucent (HT) Vita Ambria (ZLD) and IPS e.max Press (LD) (n=36, each). Each group was further subdivided into four thicknesses: 0.5, 1.0, 1.5, and 2.0 mm (n=9). The samples were fabricated, polished, and subjected to UV weathering for 384 hours, simulating one year of clinical service. Translucency and color changes were assessed using a spectrophotometer. Data were analyzed using SPSS 20, with independent t-test, paired t-test, and one-way ANOVA at a significance level of P≤0.05. Results. Vita Ambria exhibited significantly higher translucency before and after aging compared to IPS e.max press at all thicknesses (P=0.000). In both materials, translucency decreased when the thickness increased (P=0.000), observed before and after UV aging. Vita Ambria also displayed a greater color change (ΔE=2000) compared to IPS e.max press across all thicknesses (P=0.000). Conclusion. ZLD exhibited higher translucency than LD before and after accelerated artificial aging, indicating that the accelerated aging process adversely impacted the optical properties of the tested material. However, LD demonstrated superior color stability.

The Effect of Immediate Dentin Sealing Using Different Universal Adhesives on the Bond Strength of Pretreated Monolithic Zirconia to Dentin and Microscopic Morphological Alterations.

This study evaluated the effects of immediate dentin sealing (IDS) using different universal adhesives on microtensile bond strength (μTBS) of pretreated monolithic translucent tetragonal polycrystalline zirconia-based CAD/CAM restoration to dentin and microscopic morphological alterations. Mid-coronal dentin were obtained from 32 human molars and randomly allocated into 8 groups according to the presence/absence of IDS, universal adhesives for IDS (Single Bond Universal/SBU, Clearfil Quick Bond/CUQ, Optibond Universal/OBU) and zirconia surface pretreatments (tribochemical silica coating-30 μm CoJet particles/TSC, sandblasting-50 μm Al2O3/SB): Group TSC, Group TSC+SBU, Group TSC+CUQ, Group TSC+OBU, Group SB, Group SB+SBU, Group SB+CUQ, Group SB+OBU. CAD/CAM restorations (Lava Plus High Translucency Zirconia Disc) were produced, luted, and subjected to 10.000 thermocycles (5°C-55°C). Zirconia-dentin bars (2 × 2 × 8 mm) were subjected to μTBS test (n = 16). Surface morphology of zirconia and zirconia-dentin interfaces were analyzed under SEM (n = 1). Two-way ANOVA and Bonferroni tests were used for statistical analyses (p < 0.05). Regarding the presence of IDS, Group TSC + OBU showed statistically higher μTBS than Group TSC (p < 0.05). Comparing the IDS applied groups, Group TSC+OBU and Group SB+OBU showed statistically higher μTBS than Group TSC+CUQ and Group SB+CUQ, respectively (p < 0.05). According to the surface pretreatments, no significant differences in μTBS were found (p > 0.05). A thick, intact hybrid layer with long resin tags were observed for Group TSC+OBU and Group SB+OBU. After tribochemical silica coating or sandblasting pretreatments of monolithic zirconia, IDS procedure with Optibond Universal could affect the bond strength to dentin and morphological appearance, positively.

Effect of Repeated Firings on Color Stability of Zirconia- Reinforced Lithium Silicate and Lithium Disilicate Ceramics.

The purpose of this invitro study was to assess the changes in the color attributes of high-translucency (HT) lithium disilicate and zirconia-reinforced lithium silicate in BL3/0M1, A1, A2, and A3 shades during first, second, and third firing cycles. Eighty specimens of two ceramic systems (IPS e.max CAD and Vita Suprinity) in BL3/0M1, A1, A2, and A3 shades, were prepared in thickness of 1 mm (n=10). Each group was subjected to 3 firing cycles and the CIE L*a*b* color parameters of specimens were measured after each firing cycle by a reflectance spectrophotometer. The color change (ΔE) between each two firing cycles was calculated by the relevant equation. Data were analyzed by one-way ANOVA and Tamhane post hoc test. All ΔE values were significant (P⟨0.001) except for ΔE2-1 (color difference between second and first firing) and ΔE3-2 (color difference between third and second firing) in A2 shade of IPS e.max (P=0.436) and ΔE2-1 and ΔE3-2 in 0M1 shade of Suprinity (P=0.345). Repeated firing resulted in generally higher ΔE in ZLS than LDS, and 0M1 Suprinity experienced maximum ΔE after repeating firing.

Effect of aging on the translucency of lithium disilicate and zirconia reinforced lithium silicate ceramics: An in vitro study

BackgroundTranslucency of dental ceramics have great impact on the esthetic and success of dental restorations. The goal of the study is to investigate the effect of the aging process on the translucency of zirconia-reinforced lithium silicate ceramic material, and lithium disilicate ceramic material made using CAD/CAM and press processes. MethodsThirty disc-shaped specimens with 0.5 mm thickness and 10 mm diameter were fabricated of IPS e.max Press (n = 10), IPS e.max CAD (n = 10), and VITA Suprinity (n = 10) (Vita). All ceramic specimens were fabricated with shade that corresponded to A2 with high translucency (HT) and subjected to measurement of relative translucency parameter (RTP) with a spectrophotometer machine prior to and following thermocycling. The results were analyzed using the one-way ANOVA and Bonferroni methods. To identify any statistically significant change in translucency after thermocycling, paired t-tests were utilized. ResultsThe mean ΔRTP00 after aging was 3.23 ± 0.36, 0.60 ± 0.34, 3.05 ± 0.90 for IPS e.max CAD, IPS e.max Press, and Suprinity respectively. The mean RTP values in IPS e.max CAD and Suprinity decreased significantly after aging (p˂0.05). However, there was no statistically significant difference between the RTP00 values of the IPS e.max Press before and after aging (p > 0.05). ConclusionPrior to aging, there was no difference between the three materials in terms of the translucency parameter. However, the translucency of CAD/CAM lithium disilicate and zirconia reinforced lithium silicate was negatively influenced by aging.

Masking ability of CAD-CAM resin-matrix ceramics with different translucencies and thicknesses combined with four cement shades against varying background colors when facing veneer restorations

BackgroundTo evaluate the comprehensive effect of translucency, thickness, cement shades, and background color on the masking ability of resin-matrix ceramic veneer restorations.MethodsResin-matrix ceramic specimens with 2 translucencies (LT, HT) and 3 thicknesses (0.5, 1.0, and 1.5 mm) were made of Upcera Hyramic (A2 shade). Cement specimens were made of Variolink N in 4 shades (yellow, white, transparent, and bleach XL). Five background specimens were made of IPS Natural Die Material in 5 shades (ND1, ND2, ND3, ND4, and ND5). Color coordinates of 120 subgroups (n = 5) of combined specimens composed of different ceramic, cement, and background specimens were obtained using a spectroradiometer. Color difference (ΔE00) compared with a 4-mm thick specimen of LT and HT ceramics was calculated and four-way ANOVA was used for statistical analysis (α = 0.05).ResultsTranslucency, thickness, cement shade, background color, and their interaction had significant effects on ΔE00 (p < 0.001). ΔE00 values of HT groups were always higher than that of LT groups and were greater than 1.8 against all background colors. ΔE00 values of LT groups could be achieved to be less than 1.8 with appropriate thickness and cement shade. ΔE00 value decreased with increasing ceramic thickness. The effect of cement shade on ΔE00 had no obvious regularity, but ΔE00 values of bleach XL cement shade group were always lower than other cement shade groups under ND3 and ND5 background color.ConclusionsThe masking ability of CAD-CAM resin-matrix ceramics can be simultaneously affected by translucency, thickness, cement shade, and background color. Resin-matrix ceramics with low translucency has a better masking ability than that with high translucency. The masking ability of CAD-CAM resin-matrix ceramics increase with increasing thickness. Cement shade has less impact on the final color of resin-matrix ceramic restorations.

Impact of liner treatment on the translucency of CAD/CAM multi-colored lithium disilicate and multi-layered zirconia implant-supported crowns, and evaluation of fracture strength of ceramic crowns.

This study aimed to evaluate the optical properties of liner-treated CAD/CAM Multi-colored lithium disilicate (Amber Mill Direct; AMD) and multi-layered zirconia (Omega multi; OM) implant-supported crowns, as well as their effect on the fracture strength of Ti or Zr abutments to which they were applied. After sintering AMD and OM ceramic blocks, they were classified into three groups: untreated, liner-treated, and liner-treated with added color. Optical properties were evaluated by analyzing color differences using background materials to assess translucency and the masking ability of liner-treated ceramics. Subsequently, the fracture strength of implant-supported crowns applied to Ti or Zr abutments was measured, and statistical analysis was conducted using Weibull statistics. Untreated AMD exhibited the highest translucency. Liner treatment reduced translucency in both ceramics, while color-added liner treatment increased translucency. Liner-treated AMD showed greater color difference compared to OM, whereas color-added liner treatment reduced the color difference. Fracture strength was highest in Ti abutment-OM crowns (548.03 N) and lowest in Zr abutment-AMD crowns (283.58 N). Additionally, the Weibull coefficient was over twice as high in Ti abutment-AMD crowns (m = 17.500). Color liners can adjust the high translucency of lithium disilicate ceramics to block discoloration, providing natural tooth-like color and enabling the creation of esthetic restorations. Furthermore, lithium disilicate ceramic crowns applied to Ti abutments exhibited high Weibull coefficients and fracture strengths.

Effect of sintering cycle on the strength and translucency of multilayered zirconia.

A newly introduced sintering protocol promises to offer higher translucency while not significantly compromising the flexural strength of the material. However, the effect of the novel sintering protocol has not been thoroughly validated. The purpose of this study was to measure and compare the effect of two sintering protocols on the translucency and flexural strength of two multilayered zirconia materials. Two types of multilayered zirconia materials (ZirCAD Prime and Prime esthetic) were selected. Presintered disk specimens were obtained from Translucent, Gradient, and Dentin layers (n = 20). The disks were allocated to 2 groups: standard sintering protocol (peak temperature 1500°C) and high translucency sintering protocol (peak temperature 1600°C). After the sintering process, 10 specimens from each group were randomly selected. The optical values (L*, a*, b*) were measured and used to assess translucency using the relative translucency parameter (RTP00) and translucency differences (ΔRTP00). Then, all 20 specimens were tested for biaxial flexural strength. The outcomes were analyzed. The analysis of variance is used to analyze any significant effects on translucency and flexural strength. Then, any significant difference in the translucency and flexural strength between all pairs of materials was analyzed using Bonferroni-corrected Student's t-test (α = 0.05). The high translucency sintering protocol significantly decreased biaxial strength in the Prime translucent and dentine layer, Prime esthetic translucent, and gradient layer. RTP00 was significantly reduced in the Prime gradient and Prime esthetic gradient layer when sintered with a high translucency protocol. The lowest ΔRTP00 was observed in the Prime dentine layer, while the highest ΔRTP00 was observed in the Prime esthetic dentin layer. High translucency protocol significantly lowers the biaxial flexural strength of both multilayered materials, but the alteration in translucency is within clinically acceptable thresholds (TAT00 = 2.62).

Silica infiltration as a strategy to overcome zirconia degradation

The excellent clinical performance of yttria-partially stabilized zirconias (Y-SZs) makes them promising materials for indirect restorations. However, the Y-SZ phase stability is a concern, and infiltrating Y-SZs with a silica nanofilm may delay their degradation processes. In this study, we analyzed stabilities of silica-infiltrated zirconia surfaces after exposure to artificial aging (AA).Four zirconia materials with different translucencies (n = 40) were used, including low translucency 3 mol% Y-SZ (3Y-LT, Ceramill ZI, Amann Girrbach); high translucency 4 mol% Y-SZ (4Y-HT, Ceramill Zolid); and two high translucency 5 mol% Y-SZs (5Y-HT, Lava Esthetic, 3M and 5Y-SHT, Ceramill Zolid, FX white). Sintered specimens were exposed to 40 cycles of silica (SiO2) through room temperature atomic layer deposition (RT-ALD) using tetramethoxysilane (TMOS) and ammonium hydroxide (NH4OH). AA was applied for 15 h in an autoclave (134°C, 2 bar pressure). Stabilities of zirconia-silica surfaces were characterized in terms of hardness and Young's modulus using nanoindentation techniques and crystalline contents using x-ray diffraction (XRD) analyses. Silica deposition was also characterized by X-ray photoelectron spectroscopy (XPS).There was a significant effect of the interaction of materials and surface treatments on the hardness and Young's modulus values of zirconia-silica surfaces (p < 0.001). Silica deposition on zirconia surfaces improved the material resistance to degradation by AA.

Comparison of Optical Properties and Fracture Loads of Multilayer Monolithic Zirconia Crowns with Different Yttria Levels.

Multilayer monolithic zirconia, which incorporates polychromatic layers that mimic natural tooth gradients, offers enhanced aesthetics and functionality while reducing debonding risks and improving fabrication efficiency. However, uncertainties remain regarding the fracture characteristics of multilayer monolithic zirconia crowns under occlusal loading, whether composed of uniform or combined yttria levels. The current study investigated how variations in yttria levels and thicknesses affected the optical properties and fracture loads of multilayer monolithic zirconia. Samples of multilayer monolithic zirconia in the Vita A1 shade were used, while employing 3Y (SZ) and 4Y + 5Y (AZ) yttria levels. The optical properties, including the color difference (ΔEWS) and translucency parameters (TP00), were measured using a digital colorimeter. The fracture loads were analyzed using a universal testing machine, and fractured surfaces were examined under a stereomicroscope. Statistical analyses assessed the impacts of the yttria levels and sample thicknesses on the optical properties. The ΔEWS values of SZ ranged 3.6 to 4.0, while for AZ, ΔEWS at 0.5 mm was 3.9 and <2.6 for other thicknesses. The TP00 values decreased with an increased thickness, with AZ generally exhibiting greater translucency than SZ. In the fracture load investigations, SZ (>1600 N) generally exceeded AZ (>1260 N), with fracture loads notably increasing with thickness, particularly for premolars (SZ > 3270 N, AZ > 2257 N). SZ predominantly exhibited partial and complete fractures, whereas AZ showed fewer non-fracture categorizations. Complete fractures began with dense, irregular cracks that extended outward to reveal smooth surfaces, while premolars subjected to higher loads exhibited concentric ripple-like structures. Partial fractures revealed radial textures indicative of areas of stress concentration. In summary, higher yttria levels were correlated with increased translucency, while variations in the fracture loads primarily stemmed from differences in the tooth position or thickness. Overall, multilayer monolithic zirconia incorporating combined yttria levels of 4Y + 5Y (AZ) offered high translucency, precise color matching, and substantial fracture resistance, rendering it highly suitable for aesthetic and functional dental applications.

Influence of drinking cups of different materials on emotional and acceptance responses, and perception of sensory attributes of soft drinks

The aim of this study was to investigate whether drinking cups made of different materials (white polystyrene, crystal-clear polystyrene, paper, Styrofoam, and glass) can influence the response to soft drinks in terms of emotions, acceptance and perception in younger adult consumers. Experiments were conducted with three different groups of university students who (1) participated in the survey on expectations of disposable cups, (2) performed sensory tests on emotional and hedonic responses and (3) evaluated selected sensory characteristics of soft drinks served in the test cups. The characteristics of the cups influenced the overall acceptability of the soft drink, while the flavor acceptability and the perception of flavor intensity were not affected. Compared to the heavier cups, the soft drink served in lighter cups was perceived as more viscous. The soft drink was rated most acceptable when consumed from the glass and least acceptable when tasted from the Styrofoam. The Styrofoam, paper and white polystyrene had an impact on reducing the overall acceptability of the soft drink. The emotional map identified in the study for the consumption of soft drinks from different cups could be related to the sensory characteristics of the cups. Glass can be considered a more acceptable vessel for soft drink consumption compared to disposable cups, while crystal–clear polystyrene is more acceptable than paper, Styrofoam and white/opaque polystyrene. When selecting materials for disposable cups, preference should be given to materials that have similar properties to glass, such ashigher weight, low flexibility, low surface graininess and high translucency.

Effect of thickness on the translucency of machinable and printable ceramic-glass polymer materials

ObjectivesTo assess the translucency of machinable and printable ceramic-glass polymer materials with different thicknesses. MethodsFive ceramic-glass polymer materials were tested: one 3D-printable material, Permanent Crown resin (3D), two machinable materials available at low translucency (LT) and high translucency (HT) levels, VITA Enamic (VE) HT/LT, and Cerasmart 270 (CS) HT/LT. A total of 100 specimens were produced across 10 subgroups (n = 10) with thicknesses of 1 mm and 1.5 mm. The colour coordinates of the specimens were measured against black and white backgrounds using a spectrophotometer. Translucency was quantified using the Relative Translucency Parameter (RTP), calculated via the CIEDE2000 formula. A two-way ANOVA followed by post-hoc tests with Bonferroni correction (α = 0.05) was used for statistical analysis. ResultsThe RTP for both thicknesses were ranked as follows: CSHT > VEHT > CSLT > 3D > VELT. The RTP of the 3D was lower than that of the HT machinable materials (CSHT and VEHT) for both thicknesses (p < 0.05). No significant difference was observed between the RTP of 3D and CSLT at 1.5 mm (p = 1.000); however, at 1 mm, the RTP of the 3D was lower than that of the CSLT (p < 0.05). Notably, the 3D showed the least translucency difference with a 0.5 mm increase in thickness. ConclusionsPrintable ceramic-glass polymer materials demonstrated lower translucency than HT machinable ceramic-glass polymer materials. Both the thickness and type significantly influenced the translucency of the LT machinable counterparts compared to the printable ceramic-glass polymer material. Clinical significancePrintable ceramic-glass polymer resins may be a suitable option for minimally invasive procedures, especially when attempting to mask undesirable-coloured abutments. When selecting HT machinable ceramic-glass polymers, clinicians should pay greater attention to the abutment colour and thickness of the restorative material.

Compressive modulus, translucency, and irradiance transmittance of clear PVS materials used for resin injection molding technique.

To evaluate the compressive modulus, translucency, and light curing irradiance transmittance of four clear polyvinyl siloxane (PVS) materials used for the injection molding technique at varying thicknesses, and to assess the correlation between color parameters and irradiance transmittance. Four clear PVS materials (Exaclear, Clear Bite Matrix, Affinity Crystal, and Memosil 2) were used in this study. Compressive modulus was measured by compressing cylindrical PVS specimens (n = 9; d = 10 mm; t = 6 mm) up to 30% strain using a universal testing machine. For the translucency analysis and irradiance transmittance, specimens (n = 5) were fabricated with five different thicknesses (d = 12 mm and t = 2, 4, 6, 8 and 10 mm). The L*, a, *b* values of specimens were obtained using a CIELab spectrophotometer (CMD-700, Konica Minolta) with calibrated white and black tiles; the translucency parameter was calculated. The same specimens were placed onto a spectrophotometer (MARC Light Collector) to measure irradiance transmitted through the specimens from a light curing unit (Valo Corded, Ultradent). Data were analyzed using analysis of variance (ANOVA) with Tukey post hoc test and the correlation between translucency and irradiance transmittance of materials for each thickness was evaluated using Pearson's correlation. Compressive modulus differences in PVS materials were significant (one-way ANOVA: df = 3, F = 76.27, p < 0.001); Affinity and Memosil 2 were highest with no significant difference between them (Tukey: t = -1.62; p = 0.382). Clear Bite was higher than Exaclear (Tukey: t = -3.70; p = 0.004). Exaclear was lowest. Translucency decreased with thickness (Two-way ANOVA: df = 3, F = 586.53, p < 0.001; thickness: df = 4, F = 1389.34, p < 0.001). Exaclear was most translucent at all thicknesses. L*, a*, b* values varied by material and thickness (L*: df = 3, F = 1213.32, p < 0.001; a*: df = 3, F = 10766.8, p < 0.001; b*: df = 3, F = 3260.42, p < 0.001). Memosil 2 had lowest b* values. Irradiance transmittance was affected by material and thickness (Two-way ANOVA: df = 4, F = 2388.86, p < 0.001). Exaclear had highest irradiance transmission, surpassing control at >6 mm. Violet/blue irradiance ratio decreased with thickness; Exaclear maintained a constant ratio, indicating preserved violet irradiance. There was a strong positive correlation between translucency and light irradiance (Pearson's r = 0.97, R2 = 0.86-0.96). Radiant exposure analysis suggests adjusting the curing time based on PVS thickness for optimal exposure (10 J/cm2) is achievable within 13-14 s for <2 mm and 21-30 s for 8-10 mm with Clear Bite, Affinity, and Memosil 2; whereas Exaclear requires less time. Compressive modulus in clear PVS materials varied by type; Affinity and Memosil 2 demonstrate higher modulus, offering more stability of the clear mold. Translucency and irradiance transmission through clear PVS materials decreased as their thickness increased, yet Exaclear exceled in maintaining high translucency and superior light transmission capabilities. Additionally, there is a strong positive linear correlation between translucency and light irradiance transmittance, offering a method to adjust curing times effectively based on material translucency. The light curing time to adequately polymerize composite through clear impression material may need to be increased, particularly with thicker matrices or less translucent materials.

Influence of different printing orientations and post-polymerization time on the translucency of three-dimensional (3D) printed denture base resins.

To evaluate the effect of different printing orientations and post-polymerization time with thermal cycling on the translucency of 3D-printed denture base resins. Heat-polymerized (HP) acrylic resin specimens were fabricated and 3D-printed denture base materials (NextDent, ASIGA, FormLabs) were printed with different printing orientations (0, 45, 90 degrees) and subjected to different post-polymerization times (15-, 30-, 60-, and 90-min). All specimens were polished and immersed in distilled water for 1day at 37°C. CIEDE2000 was used to measure the translucency parameters (TP00) before and after thermal cycling (5000 cycles) recording the color parameters (L*, a*, b*) against a black and white background using a spectrophotometer. k-factors ANOVA followed by post hoc Tukey's test (α=.05) was performed for statistical analysis. The k-factors ANOVA test showed a significant effect of resin material, post-polymerization time, and printing orientation on translucency (p<0.001). In comparison to HP, all 3D-printed resins showed lower translucency with all post-polymerization times and printing orientation (p<0.001) except FormLabs resin (p>0.05). For all 3D-printed resins, the translucency increased, with increasing the post-polymerization time (p<0.001) and 60- and 90-min showed the highest translucency. For printing orientation, 90 and 45 degrees significantly showed high translucency in comparison to 0 degrees (p<0.001). FormLabs showed significantly higher translucency when compared with NextDent and ASIGA per respective printing orientation and post-polymerization time. The translucency significantly decreased after thermal cycling for all tested resins (p<0.001). The findings of this study demonstrated that the translucency of 3D-printed resins is influenced by the printing orientation, post-polymerization time, and resin type. As a result, choosing a resin type, and printing orientation, with a longer post-polymerization time should be considered since it may improve the esthetic appearance of the 3D-printed resins.

Comparison of Blue and Infrared Light Transmission Through Dental Tissues and Restorative Materials.

The depth of cure using blue-light photocuring units (BL) is limited by tooth structure and qualities of the restorative material through which the activating wavelength must pass. Recent developments incorporate an infrared (IR) activated upconversion (UC) fluorescence of a lining agent filled with nanocrystals of NaYF4 and doped with YB+3 and Tm+3 that emit both blue and violet light locally at the interface of the liner and restorative resin. The purpose of this study was to evaluate the BL and 975 nm infrared (IR) light power transmission through dental tissues and restorative materials. Power transmissions of the IR laser (975 nm) and a monowave blue-only light-curing unit (Bluephase 16i) through dental tissues (enamel, dentin, and enamel/dentin junction, or DEJ), eight (8) various dental resin composites, and eight (8) dental ceramics, each at four thicknesses (1, 2, 3 and 4 mm) were evaluated (n=5) using a thermopile sensor (PM10, Coherent Inc) connected to a laser power meter (Fieldmate, Coherent Inc). Power transmission values of each light source and restorative material were subjected to analysis of variance and Tukey test at a pre-set alpha of 0.05. A linear correlation (r=0.9884) between the supplied current and emitted IR power of the laser diode was found, showing no statistical power reduction with increased distances (collimated beam). For tooth tissues, the highest power transmissions for both light sources were observed using 1.0 mm enamel while the lowest values were found for 2.0 mm dentin and an association of 2.0 mm DEJ and 1.0 mm dentin. The only group where IR demonstrated significantly higher transmission when compared to BL was 1.0 mm enamel. For all resin composites and dental ceramics, increased thickness resulted in a reduction of IR power transmission (except for EverX Posterior fiber-reinforced composite and e.max HT ceramic). IR resulted in higher transmission through all resin composites, except for Tetric EvoCeram White. The highest BL transmission was observed for SDR Flow, at all thicknesses. Higher IR/BL ratios were observed for EverX Posterior, Herculite Ultra, and Lava Ultimate, while the lowest ratio was observed for Tetric EvoCeram White. Reduced translucency shades within the same material resulted in lower power ratio values, especially for BL transmission. Higher IR/BL ratios were observed for e.Max LT, VitaVM7 Base Dentin, and e.max CAD HT, while the lowest values were found for VitaVM7 Enamel and Paradigm C. IR power transmission through enamel was higher when compared to blue light, while no difference was observed for dentin. The power transmission of IR was higher than BL for resin composites, except for a high value and low chroma shade. Fiber-reinforced resin composite demonstrated the highest IR/BL power transmission ratio. A greater IR/BL ratio was observed for lower translucency ceramics when compared to high translucency.

Effects of Coloring Liquid Dipping Time and Surface Finishing Procedures on the Optical Properties of Monolithic Zirconia.

Monolithic zirconia restorations can be produced from self-colored or uncolored blocks. The coloring procedure of uncolored blocks and surface treatments may affect the appearance of the restoration. The purpose of this study is to evaluate the effect of liquid coloring and surface treatments on optical properties of translucent monolithic zirconia. All specimens were cut from zirconia blocks with a thickness of 1 mm. Specimens were dipped in the coloring liquids for 3 min, 5 min, and 7 min and then divided into groups of 10 specimens for surface treatments. Glaze and mechanical polishing were applied, and the color of the specimens was measured under the D65 lighting condition with a spectrophotometer device. Color values obtained from the CIE Lab formula and the translucency parameter (TP), opalescence parameter (OP), and contrast ratio (CR) were calculated. The normality of the data was confirmed with the Shapiro-Wilk test. A three-way analysis of variance (ANOVA) was used to assess the effect of dipping time, liquid shade, and surface treatments. The effect of liquid shade and dipping time on the TP, OP, and CR parameters were statistically significant, and the TP values were reduced with the application of coloring liquid. Mechanical polishing groups had higher OP values and lower TP values than glazed groups. In cases where high translucency is required, it may be advisable to use self-colored blocks and apply glaze as a surface treatment to achieve the desired optical properties.

Influence of crown shade, translucency, and scan powder application on the trueness of intraoral scanners

ObjectivesNatural teeth and dental restorations present with various shades and levels of translucency. This study aimed to determine whether these variations in ceramic crowns and scan powder application affect the trueness of intraoral scanners. MethodsEight identical premade resin typodonts, each prepared for a crown on the maxillary right second molar, were used. Eight lithium disilicate crowns, distinguished by two levels of translucency (high and low) and four shades (BL1, A2, A3, and A4), were fabricated to an identical design and cemented onto each typodont, providing eight distinct experimental groups (2 levels of translucency × 4 shades). Reference scans were acquired using a desktop scanner. Test scans were performed ten times for each experimental group using two different intraoral scanners (Medit i700 and CEREC Primescan AC), with and without the application of scan powder (n = 10). Three-dimensional metrology software was used to assess the trueness of the intraoral scan datasets. Statistical analysis involved the Kruskal–Wallis H test, Mann–Whitney U test, and independent t-test (α=0.05). ResultsFor powder-free intraoral scan datasets, the crown shade did not significantly affect trueness within each translucency group (P = 1.000). For both intraoral scanners, compared with low translucency groups, higher marked deviations were exhibited by high translucency groups (P<.001). Scan powder use largely mitigated these differences (P>.05) and enhanced the trueness of the intraoral scan (P<.01). ConclusionsShade did not significantly influence the trueness of intraoral scans. High-translucency crowns were scanned with less accuracy than were low-translucency crowns. Clinical SignificanceUnlike tooth shade, translucency significantly affected the accuracy of intraoral scans. Therefore, considering the use of scan powder when scanning objects with high translucency may be beneficial.

Influence of Thickness and Translucency of Lithium Disilicate Ceramic on the Degree of Conversion of Resin Cements with Different Initiators.

The degree of conversion (DC) of resin cements can be affected by ceramics, and by the type of resin cement. The purpose was to evaluate the influence of thickness and translucencies of lithium disilicate ceramic on the DC of resin cements: two light-cure (Variolink LC; NX3 LC) and one dual-cure (NX3 Dual). IPS e.max Press ceramic (A2) discs were prepared in 4 thicknesses (0.3, 0.5, 1.0, and 1.5 mm) and in 3 translucencies: HT (high translucency), LT (low translucency), and MO (medium opacity). Subsequently, 234 samples of resin cement (5 x 1 mm) were light-cured through those ceramic discs. The DC was assessed by Fourier Transform Infrared Spectroscopy (FTIR). Ceramic thicknesses decreased DC of NX3 Dual through HT-1.0 and HT 1.5 (p=0.005). Between translucencies, only MO-0.3 affected Variolink LC DC (p=0.018). There was difference among light- and dual-cured resin cements (p=0.001). Increasing thickness and opacity lead to a decrease in the DC of all resin cements, with a significantly lower DC value in NX3 Dual (HT-1.0; HT-1.5), and in Variolink LC (MO- 0.3). Light- and dual-cured resin cements were different among each other. NX3 Dual achieved a significantly lower value than its counterpart NX3 LC.

Impact of CAD/CAM Material Thickness and Translucency on the Polymerization of Dual-Cure Resin Cement in Endocrowns.

The objective of this study is to evaluate the impact of the thickness and translucency of various computer-aided design/computer-aided manufacturing (CAD/CAM) materials on the polymerization of dual-cure resin cement in endocrown restorations. Three commercially available CAD/CAM materials-lithium disilicate glass (e.max CAD), resin composite (CERASMART), and a polymer-infiltrated ceramic network (ENAMIC)-were cut into plates with five different thicknesses (1.5, 3.5, 5.5, 7.5, and 9.5 mm) in both high-translucency (HT) and low-translucency (LT) grades. Panavia V5, a commercial dual-cure resin cement, was polymerized through each plate by light irradiation. Post-polymerization treatment was performed by aging at 37 °C for 24 h under light-shielding conditions. The degree of conversion and Vickers hardness measurements were used to characterize the polymerization of the cement. The findings revealed a significant decrease in both the degree of conversion and Vickers hardness with increasing thickness across all CAD/CAM materials. Notably, while the differences in the degree of conversion and Vickers hardness between the HT and LT grades of each material were significant immediately after photoirradiation, these differences became smaller after post-polymerization treatment. Significant differences were observed between samples with a 1.5 mm thickness (conventional crowns) and those with a 5.5 mm or greater thickness (endocrowns), even after post-polymerization treatment. These results suggest that dual-cure resin cement in endocrown restorations undergoes insufficient polymerization.