IPS E-max CAD Research Articles

Influence of thickness difference on color change of contemporary Computer Aided Designing/Computer Aided Manufacturing glass-ceramic materials

Purpose To study the effect of thickness difference on color change of glass ceramic materials. Patients and methods Sixty three specimens were divided according to type of the material into three groups (n = 21) as follow Leucite based glass-ceramic (IPS Empress CAD), lithium disilicate based glass ceramic (IPS EMAX CAD), zirconia reinforced glass ceramic (celtra duo) and each group was further subdivided into three subgroups according to thickness (0.7, 1, 1.2 mm) seven each. The specimens were sawed by using linear precision saw, were square in shape and their dimension was 10 mm of length, 10 mm of width and three difference thicknesses (0.7, 1, 1.2 mm). The final thickness of specimens was confirmed with a digital caliper for standardization. Each group of specimens was finished according to its material manufacturer instruction, Cary 5000 Spectrophotometer provided from Agilent Technologies was used to measure color difference. One-way analysis of variance used to compare materials after glazing, multiple comparison Tukey test to compare each two materials. Results There was significant difference between all groups. At color width 0.7 and 1 mm, Celtra duo recorded the lowest color difference value while Empress recorded the highest color difference value. There was highly significant difference after glazing between materials where P value more than 0,001. At color width 0.7 and 1.2 mm, there was a highly significant difference after glazing between materials where P value is 0.001. Celtra duo showed the lowest color difference value while Emax and Empress showed equal values where P value more than 0.993. At color width 1 and 1.2 mm, Empress recorded the lowest color difference while Emax recorded the highest value. There was a highly significant difference between Emax versus Empress and Celtra duo versus Empress where P value was 0.001. On the other hand there was no significance recorded between Emax vs celtra duo where (P > 0.984). Conclusion Masking abilities of glass ceramic are affected by ceramic thicknesses, background colors. The masking ability of glass ceramics tends to improve with greater thickness, while translucency decreased.

Evaluation of Discoloration After Thermocycling in CAD/CAM Blocks of Different Thicknesses

The study aims to evaluate the color of CAD/CAM blocks of different thicknesses after thermocycling as in-vitro. A total of 180 samples (n=10) were prepared in 2 thicknesses (0.5mm, and 1.0 mm) from various CAD/CAM blocks of different structures (Katana UTML, Prettau® 4 Anterior® Dispersive, IPS e-max Cad, Vita YZ-XT, Vita YZ-T, Vita Suprinity PC, Vita Enamic, Shofu HC, G-Ceram). The color values of the samples (L*, a*, b*) were measured before and after thermocycling. The discoloration (ΔE) data obtained were statistically compared with two way-ANOVA, Tukey HSD posthoc tests, and Paired Sample T-Test (p<0.05). The highest average discoloration was found in the Katana group (ΔE=3.07) with a thickness of 1 mm, while the lowest was found in the Shofu HC group (ΔE=0.49) with a thickness of 0.5 mm. In contrast, the ΔE value was significantly different in samples with a thickness of 1 mm and 0.5 mm (p<0.05), there was no difference in the ΔE values in the groups in themselves. Discoloration values of test materials depending on thickness varied, but the difference of thickness in the same material did not affect the color change. All the color changes were clinically accepted.

Esthetic Rehabilitation of Patient with Multiple Diastema following Orthodontic Treatment and Maxillofacial Surgery: a Case Report

To perform esthetic rehabilitation with diastema closure of a patient after ortho-surgical treatment using lithium disilicate veneers. A 22-year-old male patient with multiple diastema in the maxillary arch following orthodontic treatment and maxillofacial surgery applied for prosthodontic treatment. Digital planning was done on preoperative photographs in 3Shape Smile Design software. The width/length ratio of the central incisors had key importance when choosing a triangle tooth form with a Proportional Smile Design. Study casts were mounted by facebow and bite records for analog wax-up (KaVo Protar evo 5B Articulator). Wax-up was guided by the contour line of smile design. A silicone block was prepared for the functional mock-up which was found esthetic and comfortable for the patient. A 0.4 mm width butt joint preparation was used for IPS e-max CAD lithium-disilicate veneers. Two phases one-time A-silicone impression was taken with double-cord technique. Veneers were delivered by superimposing the abutment teeth and the wax-up STL files in CAD software (Ceramill Mind). Restorations were manufactured from IPS e-max CAD lithium-disilicate MT A2 blocks and were individually characterized. The final restoration was cemented with LC adhesive resin cement (Variolink Esthetic LC) in rubber dam isolation. The patient was satisfied with the esthetic and functional outcome of the final restorations. Analog/digital workflow following treatment planning with 3Smile Design software makes treatment predictable. Proportional Smile Design is an effective method for designing a smile balanced with the face. High-quality CAD/CAM materials offer superior esthetics for patient satisfaction in the case of minimal invasive preparation.

Lithium disilicate and zirconia reinforced lithium silicate glass-ceramics for CAD/CAM dental restorations: biocompatibility, mechanical and microstructural properties after crystallization

ObjectivesThe objective of this study was to define the impact of heating rate on the crystal growth, the mechanical properties, and the biocompatibility of three different kinds of CAD/CAM glass-ceramics treated with a conventional furnace. MethodsLithium disilicate (IPS EMax-CAD, Ivoclar Vivadent) (LS2) and two zirconia reinforced lithium silicate (ZLS) ceramics (Vita Suprinity PC, VITA Zahnfabrik; Celtra Duo, Dentsply Sirona) (ZLSS; ZLSC) were used. The mechanical properties and the crystal growth were evaluated on 42 specimens (n = 14 per group). The thermal treatments recommended by the manufacturers were carried out. All groups were tested for fracture toughness (Ft) and Vickers hardness (Hv). Scanning electron microscope (SEM) images were taken after a slight surface etching with hydrofluoric acid solution (1% for 20 s). Differential Thermal Analysis (DTA) was performed and cellular adhesion with human periodontal ligament stem cells (hPDLSCs) culture was qualitatively assayed. Data were analyzed with Repeated Measurements ANOVA and ANOVA followed by Tukey post hoc test. ResultsThe crystals’ mean size (±SD) after heat treatment was 1650.0 (±340.0) nm for LS2, 854.5 (±155.0) nm for ZLSS and 759.9 (±118.4) nm for ZLSC (p < 0.05 among the groups). As consequence of crystallization, the Hv was 6.1 ± 0.3 GPa for LS2, 7.6 ± 0.7 GPa for ZLSS and 7.1 ± 0.5 GPa for ZLSC (p < 0.05 for LS2 vs ZLSS and ZLSC), while the Ft was 2.2 ± 0.1 MPa m1/2 for LS2, 4.7 ± 0.8 MPa m1/2 for ZLSS and 3.8 ± 0.6 MPa m1/2 for ZLSC (p < 0.05 among the groups). The DTA curves showed a crystallization process for LS2, ZLSS and ZLSC at a temperature range 810–840 °C. The amount of adherent hPDLSCs was superior on LS2 than on ZLS. ConclusionsAll the CAD/CAM materials can be properly crystallized if heat treated following the manufacturers’ instructions. The crystallization process highly depends on temperature. ZLS glass ceramics show significantly inferior crystals dimensions and higher fracture toughness and Vickers hardness than LS2 ceramic. hPDLSCs cultured on LS2 have a superior adhesion than those cultured on ZLS. Clinical significanceThe value of this study relies on the demonstration that a proper heat-treatment of CAD/CAM lithium disilicate and ZLS glass ceramics generates products that are suitable for clinical use . The differences highlightable in mechanical properties and biocompatibility behavior do not affect their successful clinical application.

5 - Effect of Roughness on Flexural Strength of Dental Lithium-Disilicate

A common process in dental clinics is to perform small fitting adjustments of dentures after testing in the patient's mouth using the micro-grinding tool. This procedure promotes a local roughness increase and can lead to the formation of microcracks on the prosthesis surface. The aim of this work was to investigate the benefits of a post-finishing heat treatment on the surface roughness smoothing and crack healing of lithium disilicate dental glass ceramics, and its effect on the flexural strength. Commercially available lithium metasilicate, Li 2 SiO 3 (IPS e-maxCAD), samples were heat treated at 840C-7min. The material was characterized by X-ray diffraction, Scanning Electron Microscopy, Vickers hardness, Youngs modulus and fracture toughness. One of the surfaces of the samples was machined, aiming to simulate the fitting procedure of dentures in the dentist's laboratory, generating a rough surface. Half of the samples were tested by biaxial flexural testing (3B-P) and the other half were submitted to a rapid heat treatment (840C-3min) and later tested by biaxial strength, with statistical analysis by Weibull. The Roughness parameters (Ra, PV and Rz) were measured using Zygo New View 7100 Optical Profiler. After the crystallization heat-treatment protocol suggested by the manufacturer, the formation of elongated lithium disilicate crystals, Li 2 Si 2 O 5 , with 36% residual amorphous phase was observed. In addition, the Vickers hardness of 6.1±0.3 GPa, fracture toughness of 1.90± 0.2 MPa.m1/2 and modulus of elasticity values of 91 ±2 GPa were obtained. The samples from the group without rapid heat-treatment showed bending strength of 203.5 ±33 MPa, with roughness values of Ra=0.6 ±0.2 μm, Rz=22 ±6 μm and PV=28 ±7 μm. After the rapid heat treatment, the roughness parameters Ra, Rz and PV were 0.3 ±0.2 μm, 9 ±6 μm and 5 ±4 μm, respectively. With this reduction in roughness, the flexural strength increased by 65%, with mean values of 336.6 ±32 MPa. Weibull modulus values were in the order of 5 for both groups. In the need for finishing machining of lithium disilicate-based glass-ceramic dental prostheses, the use of a rapid heat treatment at 840 C allows considerable gains in flexural strength. Increasing the service life of the prosthesis, due to a reduction on the surface roughness, promoted by the softening of the remaining amorphous phase in the glass-ceramic.

Wear behavior of current computer-aided design and computer-aided manufacturing composites and reinforced high performance polymers: An in vitro study.

To analyze the wear rate of computer-aided design and computer-aided manufacturing (CAD/CAM) composites, polyetheretherketones and glass ceramics. Our study groups were prepared from two different resin-based composites (Brillant Crios, Cerasmart), a glass ceramic (IPS Emax CAD) and reinforced polyetheretherketone (BioHPP) material (n=10). Premolar teeth were used as antagonists. The specimens, which were subjected to two body wear tests (240,000 cycles, 1.2Hz, 50N) in the chewing simulator, were scanned with a 3D laser scanner both before and after the wear test. Volume loss and wear depth were determined by means of the obtained images software program. The wear pattern was examined by scanning electron microscopy. Kruskal Wallis test served for analyzing. The least volume loss and wear depth were seen in the polyetheretherketone material (0.06 ± 0.04 mm3 , 0.02 ± 0.01 mm), while the maximum volume loss was seen in the groups containing resin-based composite. (p=0.05). The volume loss value in glass ceramics is between CAD/CAM composites and polyetheretherketone. The behavior of polyetheretherketone against enamel was different from glass ceramics and composite materials in terms of the amount of wear. Polyetheretheketone can be considered as an alternative to other chairside materials in terms of wear resistance.

Influence of the Multiple Layers Application and the Heating of Silane on the Bond Strength between Lithium Disilicate Ceramics and Resinous Cement.

Objective This study aimed to evaluate the bond strength between lithium disilicate ceramic and resinous cement when silane (Prosil, FGM) was applied in different amounts of layers under heating or not. Materials and Methods Sixty IPS E-max CAD ceramic (Ivoclar) was used. They were conditioned with 10% hydrofluoric acid for 20 seconds. The samples were distributed in six groups ( n = 10): 1Sil, 1 layer of silane without heating; 1SilAq, 1 layer of silane with heating; 2Sil, 2 layers without heating; 2SilAq, 2 layers with heating; 3Sil, 3 layers without heating; and 3SilAq, 3 layers with heating. After each layer, a jet of cold air was applied for 20 seconds in groups 1Sil, 2Sil, 3Sil, and jet of hot air (50°C) in groups 1SilAq, 2SilAq, and 3SilAq. Subsequently, an adhesive layer was applied, and fourcylinders were made on the ceramic with a resin cement AllCemVeneer and photoactivated for 20 seconds. The samples were stored at 37°C for 24 hours and analyzed to the microshear test at EMIC. Statistical Analysis Data were submitted to ANOVA and Tukey’s test (α = 0.05). Results The results showed that there was no statistical interaction between the factors studied. The “heating” factor was not statistically significant; however, the “silane layers” factor showed differences between groups. The analysis of the results showed that the use of one (66%) or two layers (67%) of silane regardless of heating, produced higher values of bond strength, when compared with the group of three layers (62%). Conclusion The use of silane with one or two layers provided a greater bond strength between lithium disilicate ceramic and resinous cement and that the heating did not influence the results.

Fracture resistances of CAD/CAM monolithic crowns with different occlusal thickness.

Purpose: This study was designed to examine fracture resistances of different monolithic crowns made by computer-aided design and computer-aided manufacturing (CAD/CAM) on dental implants with different occlusal thickness. Materials and methods: 20 molar crowns were fabricated of four different monolithic ceramic blocks (n=5): Group I: Vita Enamic (V.enamic), GroupII: IPS E-max CAD(e.max), GroupIII: Celtra Duo(CD), GroupIV: Functional explore (f.explore);using CAD/CAM system with different occlusal thickness (1 and 1.5mm). All crowns were cemented on implant abutments using self adhesive resin cement. Combined thermal cycling and mechanical loading was performed under a chewing simulator, A universal testing machine was used to apply load to crown until fracture. The fractured specimens were examined with a scanning electron microscopy. Results: The highest fracture resistance was recorded with f.explore group followed by CD group then e.max group while the lowest fracture resistance mean value recorded with V. Enamic with statistical significance (P=0.0001 0.05) higher fracture resistance mean value than 1mm occlusal thickness except for f.explore group.Conclusions: The fracture resistance of monolithic crowns were differently influenced by the ceramic materials and changes in occlusal thickness. Within the limitations of this study, all the tested crowns withstood the physiological masticatory loads both at the recommended and reduced occlusal thickness.

Impact of Bleaching before or after Veneer Preparation on Color Masking Ability of Laminate Veneers: An In Vitro Study.

Purpose This study evaluates the effect of bleaching before or after veneer preparation and the depth of preparation on color masking ability of laminate veneers. Methods. Sixty extracted premolars were artificially stained to vita shade A4, verified by digital spectrophotometer (Vita Easy Shade V), and then divided into three groups: NB = nonbleached, BBP = bleaching before preparation, and BAP = bleaching after preparation. Based on the preparation depths, each group was further divided into two subgroups: S1 = 0.5 mm and S2 = 1.0 mm. BBP and BAP were subjected to one session of in-office bleaching using 35% hydrogen peroxide. IPS e-max CAD veneers of 0.5 and 1.0 mm thickness (corresponding to the preparation depths) of the same shade and translucency (HT A1) were cemented immediately to the bleached surfaces. Immediately after cementation, the color change ΔE between the baseline (after staining) and the resulted shades was measured using the Vita Easy Shade V digital spectrophotometer and CIELab color system. Results Bleached groups exhibited a significant ΔE value compared to the nonbleached group (p < 0.05). BAP showed the highest ΔE value. No significant difference was found between BBP and BAP. S2 revealed a significant ΔE value than S1 (p < 0.05). No significant difference was found between S1of BAP and S2 of NB, BBP, and BAP (p > 0.05). Regarding the color coordinates, the difference between the tested groups was highly significant in lightness (ΔL∗) (p < 0.001), while no significant differences were found in green/red value (Δa∗) and yellow/blue value (Δb∗) (p > 0.05). Conclusions In cases of severe tooth discoloration, one session of in-office bleaching before or after veneer preparation and the preparation depth do not influence the color masking ability of laminate veneers.

Marginal accuracy of different CAD/CAM monolithic crowns cemented on implant abutments

Purpose: The aim of this study was to evaluate the marginal adaptation of four monolithic CAD/CAM all-ceramic crowns cemented on implant abutments after fatigue loading. Materials and methods: A lower right first molar was designed in CAD/CAM software and twenty crowns were machine milled using four different monolithic ceramic blocks (n=5): Group I: Vita Enamic (V.enamic), GroupII: IPS E-max CAD(e.max), GroupIII: Celtra Duo(CD), GroupIV: Functional explore (f.explore). The crowns were fabricated using CAD/CAM system. All crowns were cemented on implant abutments using self adhesive resin cement. Vertical margin gap distance of all crowns was measured using a digital microscope. All the samples were subjected to fatigue cyclic loading for 75.000 cycles. The vertical marginal gap distance for all samples were subsequently remeasured after the fatigue loading testing. Data were collected, tabulated and statistically analyzed. Results: The highest marginal gap mean value was for CD group followed by f. Explore group then V. Enamic group while the lowest marginal gap mean value was recorded with e.max group and this was statistically significant between the groups (P=0.0013< 0.05). The total marginal gap mean values with all types of ceramics were higher after aging than before with significant difference (P=<0.0001< 0.05). Conclusions: all-ceramic crown materials that are used for chair-side CAD/CAM systems demonstrated clinically acceptable marginal adaptations. V. Enamic and LD provided better marginal fit than CD and f.explore zirconia. Fatigue loading had a detrimental influence in the vertical marginal gap distance for all ceramic types except f.explore zirconia.

Wear resistance and surface roughness of two types of monolithic glass ceramics: An in vitro study

Aim: The purpose of study was to evaluate wear and surface roughness of ZLS compared to lithium disilicate glass ceramic before and after simulated mastication. Materials and Methods: Thirty samples were divided according to material of construction into three groups (n = 10). Group (1): E Max-CAD, Group (2): Celtra duo ZLS, Group (3): Celtra press ZLS. The sectioned samples of E-max CAD blocks were polished and crystalized. The sectioned samples of Celtra Duo ZLS blocks were glazed and fired. The Ingots of celtra press were lab pressed, sectioned, glazed and power fired. The two-body wear testing was done using chewing simulator. Each ceramic sample was weighed and evaluated for surface roughness before and after wear simulation test using electronic analytical balance and the optical profilometry, respectively. Results: IPS E-max CAD revealed highest amount of weight loss with no statistically significant difference between groups. The change in weight for each group was non-significant . The roughness mean value for E-max CAD was significantly decreased and recorded the lowest roughness change. No significant difference in the roughness mean value between the two celtra materials. The roughness change for either Celtra Duo or Celtra Press groups was non-significantly increased. Conclusions: ZLS Celtra ceramics had insignificant less wear and significant higher surface roughness with enamel antagonist compared to E-max CAD. Although wear and roughness were affected by the surface finishing of glass ceramics, the construction method of ZLS restorative materials had no significant impact on both.

COLOR DUPLICATION IN LITHIUM DISILICATE RESTORATIONS FABRICATED BY CAD-CAM USING VISUAL AND INSTRUMENTAL SHADE MATCHING SYSTEMS

ABSTRACT Introduction: Color reproduction is one of the most challenging issues encountered by clinicians because of the complexity of visual properties of natural teeth. Objectives: This study aimed to assess color differences among intended and fabricated shades of lithium disilicate restorations fabricated by CAD-CAM after using visual and instrumental shade matching systems. Materials and Method: IPS Emax CAD blocks measuring (12.4mm width x 14.5mm length x 18 mm thickness) were cut under continuous water irrigation using diamond-impregnated slicing wheels mounted on a slow-speed saw microtome (Isomet; Buehler) to yield 16 rectangular specimens measuring (12.4 x 14.5x 1.5 mm). Then they were subjected to the crystallization cycle. Then IPS Emax glaze paste was applied with uniform thickness onto the crystallized specimen surface. Each master disk represented the color of a shade guide tab in the Vita Classic (16 shades). Shade selections for these master disks were carried out following visual and instrumental methods. Accordingly, 16 visual and 16 instrumental experimental disks were fabricated. After analysis, color differences (∆E) between the master and the fabricated ceramic discs were measured using the equation. Results: On comparing Visual Emax CAD and instrumental Emax CAD, the mean(∆E) for visual (2.96± 1.90) was lower than the mean(∆E) for instrumental (22.22± 4.73) with a significant difference between them p < 0.001. Conclusions: Visual shade selection using classical shade guide showed lower delta E than that of instrumental shade matching using Easyshade. Keywords: Color duplication, lithium disilicate, E-max, Visual, Instrumental. Running title: Color duplication using visual and instrumental methods.

Machinability of Zirconia Toughened Mica Glass Ceramics for Dental Restorations

Objective: For a dental material to be machinable for CAD/CAM technology, it must offer convenient machining, under a given set of cutting conditions. Quantitative evaluation of machinability has been assessed in literature through various parameters such as tool wear, penetration rates, surface roughness, cutting force and power. A machinable ceramic will typically demonstrate a higher tool penetration rate with signs of reduced diamond tool wear and edge chipping. The purpose of this in vitro study was to evaluate the feasibility of machining an experimental ceramic, 20 wt.% zirconia reinforced mica glass ceramics (G20Z) for indirect dental restorations and compare the tool penetration rates of G20Z to commercially available dental ceramics, Presintered Zirconia (PSZ) and IPS emax CAD. Material and Methods: Precursors of base glass (SiO2 -Al2O3 -K2O -MgO-B2O3 -F) were melted at 15000C for 2 h in a platinum crucible and quenched in deionised water. The glass frit was ball milled with 20 wt. % YSZ (G20Z) and subject to two stage heat treatment in a muffle furnace. Specimens of G20Z (12 X 2 mm) were evaluated for their feasibility of machining under varying spindle speed, depth of cut, and feed rates. Influence of depth of cut, spindle speed and feed rate (vc=8000-16000 rpm, d=0.4-0.8 mm, f=0.1- 0.3 mm/tooth) on cutting forces, material response, surface roughness and tool wear were investigated. Tool penetration rates, tool wear and margin chipping were also evaluated and compared with Pre-sintered Zirconia (PSZ) and e.max CAD in a custom dental milling surveyor at 30,000 rpm with a load of 0.98 N under water lubrication for 6 min. Tool penetration rates were calculated as the ratio of length of cut and milling time with a measuring microscope and scanning electron microscope was used for tool wear and edge chipping. ANOVA and Tukey Kramer tests were used for statistically comparing the means of each group. Results: Spindle speed and feed rate play a significant role in influencing surface roughness, thrust force, cutting forces and tool wear. Penetration rates of G20Z (0.32 ±0.12 mm/min) was significantly greater than PSZ (0.26 ±0.06 mm/min) and IPS e.max CAD (0.21 ±0.05 mm/min). SEM observations reveal tool abrasion and edge chipping regardless of the ceramic type. Conclusion: High spindle speeds delivers low cutting forces with an average surface roughness of 1.61 µm, with abrasive wear of the tool insert and brittle fracture of zirconia mica glass ceramic composites. G20Z with its machinable nature demonstrates greater tool penetration rates than PSZ and IPS e.max CAD. Tool wear and edge chipping is seen in all the investigated ceramics. Keywords Machinability, Dental Ceramics, Mica Glass-Ceramics, Dental Zirconia, Tool penetration rates.

Influence of CAD/CAM Material and Preparation Design on the Long-term Fracture Resistance of Endocrowns Restoring Maxillary Premolars

Objective: To evaluate the effect of different occlusal preparation designs and CAD/CAM materials on the fracture resistance of maxillary premolars endcrowns. Materials and Methods: sixty-four endodontically treated upper first premolars were randomly divided into four groups according to ceramic materials (Vita Enamic and IPS emax CAD) and occlusal preparation designs (Anatomical and horizontal butt joint). After teeth preparation, the restorations were all made by CAD/CAM system (Cerec MCXL). Half of each group had undergone cyclic fatigue testing of 105 cycles with 50N loading force at a frequency of 0.5Hz in a mechatronic chewing simulator machine, and then all samples were loaded to fracture using a universal testing machine with a cross head speed of 0.5mm/min recording the fracture resistance values in N . The specimens were measured and statistically analyzed using using three-way analyses of variance (ANOVA), followed by serial two-way and one-way ANOVAs at each level of the study. P-values were adjusted for multiple comparisons using BENFORRONI correction and the significance level was set at P ? 0.05 for all tests. Results: Vita Enamic endocrowns showed higher fracture resistance values than IPS e max specimens. Conclusions: Vita Enamic endocrowns with anatomical preparations were found to be more favourable restoring endodontically treated maxillary premolars. KEYWORDSEndocrowns; All-Ceramic; Fracture; Cyclic loading; CAD/CAM

Effect of Different Preparation Designs on the Fracture Resistance of IPS Emax CAD Endo-Crowns

Effect of Different Preparation Designs on the Fracture Resistance of IPS Emax CAD Endo-Crowns

Influence of thickness and background on the color changes of CAD/CAM dental ceramic restorative materials

This study aimed to compare the effect of thickness and background on the color changes of CAD/CAM materials (zirconia-reinforced lithium silicate (Suprinity), lithium disilicate (IPS E-max CAD), and hybrid ceramic (Enamic)). Twelve specimens for each thickness (0.4 mm, 0.5 mm, 1 mm, 1.5 mm, and 2 mm) were obtained by sectioning three CAD/CAM materials. A spectrophotometer was used to measure the color change of the specimens against different backgrounds (A2 enamel, A4 dentin, gray, and metal) using the CIELab color space system. Analysis of variance, sample t-test, and posthoc multiple comparison tests were used to evaluate and compare the color changes for different material types, thicknesses, and background colors, with a significance level of P ≤ 0.05. The result demonstrated that material type, the thickness of the material, and the color of the background had a significant effect on ΔE (P = 0.000). Regardless of the material thickness, Suprinity had the highest mean ΔE values (5.4 ± 1.9), and E-max had the lowest mean ΔE values (1.1 ± 0.6). At 2 mm thickness, Enamic presented the lowest ∆E values (0.5 ± 0.5) against the A2 background. The 0.5 and 1 mm specimens corresponded to the highest ΔE values, whereas the 1.5 and 2 mm thickness specimens predominantly gave the lowest ΔE values. All the independent factors, including the type and thickness of the material, and color of the background, contributed significantly to ΔE of the tested materials (P ≤ 0.05). The study confirms the high masking ability of the lithium disilicate (E-max) material. In clinical situations where the color of the core needs to be masked, it is recommended to use lithium disilicate (E-max).

Marginal Accuracy and Microleakage of Machinable Laminate Veneers

Purpose: The current study aimed to evaluate the marginal accuracy and microleakage of machinable laminate veneers. Materials and Methods: Twenty-four human maxillary central incisor teeth were collected and prepared (butt-joint preparation) to receive laminate veneers. They were divided into three groups (n=8) according to material of construction: Group I: IPS-Emax CAD, Group II: Vita Suprinity, Group III: Celtra-Duo. The veneers were milled from the blocks in a CEREC 3 Machine. All veneers were cemented with resin cement. All samples had been subjected to 1500 thermal cycles which are equivalent to one year and half of clinical use. Marginal gap (pre and post cementation) and microleakage were detected for all samples. Data were tabulated and statistically analyzed. Results: Regarding vertical marginal gap, E max CAD showed the highest mean value followed by Celtra Duo, while the lowest mean value was found in Vita Suprinity. The mean values before cementation were higher than after cementation. Regarding microleakage, the highest mean value was found in E max followed by Celtra Duo, while the lowest mean value was found in Vita Suprinity. Leakage at cervical margins showed higher mean values than incisal one. Conclusion: Under the test conditions, the following was concluded: Zirconia reinforced Lithium silicate restorations, particularly the partially crystalline form, introduced better marginal accuracy and microleakage than Lithium disilicate restorations. There is a direct correlation between marginal accuracy and microleakage.

Fracture Resistance and Retention of Three Different Endocrown Materials

Purpose: The purpose of the current study was to assess fracture resistance and retention of three different endocrown materials. Materials and Methods: Thirty (n=30) sound mandibular molars were endodontically treated and according to endocrown constructed material appointed arbitrarily into 3 groups (n=10 each); Group (1): IPS e.max CAD, Group (2): Vita Suprinity and Group (3): Vita Enamic. Samples of each group were additionally subdivided into2 subgroups (n=5 each) according to fracture resistance and retention tests. Subgroup (A): Samples subjected to fracture resistance test and mode of failure. Subgroup (B): Samples subjected to retention test and mode of failure. The samples were thermocycled and seated on a universal testing machine and subjected to fracture resistance and retention test, then Data were statistically analyzed. Results: The highest mean failure load was recorded for Vita Suprinity endocrowns, followed by IPS e-max endocrowns, while Vita Enamic endocrowns recorded the lowest mean failure load.A non-statistically significant difference between the three tested groups of subgroup (A) revealed by using ANOVA test.The highest debonding load was recorded for Vita Enamic endocrowns, followed by IPS e-max CAD endocrowns, while the lowest mean debonding was recorded for Vita Suprinity endocrowns. A non-statistically significant difference between the three tested groups of subgroup (B) revealed by using ANOVA test. Conclusions: Endocrowns of Vita Suprinity showed higher mean failure load value compared to endocrowns of E-max CAD and Vita Enamic. While endocrowns of Vita Enamic showed higher mean debonding load value compared to E-max CAD and Vita Suprinity.

Fracture Resistance and Retention of CAD/CAM Endo-Crowns Using Different Preparation Designs

Purpose: to study the influence of different preparation designs on fracture resistance and retention of CAD/CAM endocrowns. Materials and methods: Forty human mandibular molars were selected to conduct the present study. All teeth were randomly divided into 2 groups (n=20 each) according to the preparation design of endocrown, Group (1): Endodontically treated teeth without ferrule (butt joint). Group (2): Endodontically treated teeth with 1mm ferrule. All prepared teeth were restored using IPS e-max CAD endocrowns. After cementation of endocrowns all specimens were subjected to thermal cycling in automated thermocycling machine in order to mimic the intra-oral condition. Then retention was measured using material testing machine, also fracture resistance was measured using material testing machine. The recorded data were collected, tabulated and statistically analyzed. Results: Endodontically treated molar with 1mm ferrule showed high fracture resistance and retention than endodontically treated molar without ferrule. Conclusions: All obtained fracture resistance and retention values lie within the clinically accepted ranges, endocrowns with 1mm ferrule have fracture resistance and retention higher than endocrowns without ferrule (butt joint).

Effect of Surface Treatments on the Color Change and Shear Bond Strength of Porcelain Laminate Veneer

Effect of Surface Treatments on the Color Change and Shear Bond Strength of Porcelain Laminate Veneer Aim of the study: the purpose of this Invitro study to evaluate the effect of surface treatments on the color change and shear bond strength of lithium disilicate glass ceramic veneers. Materials & Methods: Twenty square samples with dimensions (8x8x2) and another twenty samples with smaller dimensions (4x4x2) were cut from five IPS e-max CAD blocks of shade A3. The discs were divided into two groups: 1) Half of the small and large blocks were subjected to hydrofluoric acid (HF); 2) the other half was subjected to Co2 laser irradiation. The conditioned samples were subdivided according to the bonding agent: A) Silane application for 60 seconds; B) Single bond universal light cured for 10 seconds. Each small sample was cemented on the top of a large sample using Rely-x veneer cement with translucent shade. The color change was measured using spectrophotometer. The shear bond strength was tested using a universal testing machine. Results: HF resulted in higher bond shear bond strength and ΔE than Co2 laser. Single bond universal resulted in higher shear bond strength values than silane. Conclusion: HF followed by either single bond universal or silane could be the best surface treatment for e-max CAD ceramic. However, Co2 laser could be a promising alternative surface treatment.