All-ceramic Systems Research Articles

Effect of Different Surface Treatments on Surface Roughness and Vickers Micro-Hardness of Feldspathic Porcelain: An In Vitro Study

Background: Several new all-ceramic systems with superior aesthetic qualities such as translucency similar to natural tooth have been developed over the last two decades in response to the demand for metal-free and more natural-looking restorations. To achieve that, all-ceramic restorations, need characterization and glaze.
 Materials and methods: Twenty-four layered zirconia discs (10 mm in diameter and 2 mm thickness) were designed by a special Sketchup 3d software program and saved as an (STL) file. All specimens were subjected to the polishing by using 600, 800, and 1200 grit of aluminum oxide paper in sequence. The specimens were divided into three groups each with eight samples (n=8) the first group was treated with glaze (G), the second group was polished with polishing kit (PK), and the third group was polished with polishing diamond paste (DPP). After the surface treatments were performed, the surface roughness was measured by using a profilometer and Vickers microhardness (VHN) was measured by using a digital microhardness tester. The surface characteristics changes were examined using a scanning electron microscope (SEM). Data were statistically tested with one-way ANOVA, Post-hoc Tukey’s test, and Least Significant Difference (LSD).
 
 Results: Glazing and polishing techniques significantly affected the (Ra) and VHN of feldspathic ceramic. Group G showed significantly the lowest surface roughness (50±0.26) µm in comparison with groups PK (1.00±0.30) µm and DPP (70±0.42) µm. The largest VHN was obtained in a PK group (658.9±66) and the lowest VHN value was shown with the G group (538.4±36), while the VHN of DPP group was (652.8±66).
 Conclusions: Glazed surface group had the lowest surface roughness and microhardness compared to the polishing kit and polishing paste groups. Therefore, glazing is recommended for finishing feldspathic porcelain, as it is more clinically acceptable, and it causes less wear to the antagonist's teeth.

Evaluation of Flexural Strength of different all-ceramic porcelain systems

ABSTRACT Statement of problem protective and restorative dentistry's basic function is to protect the continuity and integrity of the tissues and to restore function, phonation, and esthetics lost due to any cause. The success of dental ceramics is affected by flexural strength, but little data are available on their clinical performance. Purpose: This study evaluated the flexural strength of the İn-Ceram Alumina, In-Ceram Zirconia, and Finesse press all-ceramic porcelain systems. The success of dental porcelains is partly related to their flexural strength. The values of flexural strength of three porcelain Systems were measured to include In-Ceram Alumina, In-Ceram Zirconia, and Finesse press all ceramic porcelain systems. Material and methods: The flexural strengths of the three porcelain systems were determined by employing the method ISO specification 6872. For the statistical evaluations of the flexure strength values, Kruskal Wallis and Mann-Whitney U tests were used. Results: When the flexural strengths of In-Ceram Alumina, In-Ceram Zirconia, and Finesse groups were compared, the differences were found to be statistically significant. Conclusion: The highest flexural strength was observed for In-Ceram Zirconia, followed by In-Ceram Alumina and Finesse porcelain system. Clinical implications: In this in vitro study, In-Ceram Alumina, In-Ceram Zirconia, and Finesse all-ceramic systems were compared concerning flexural strength. The differences between the groups are significant (p<0.05).

Assessment of Different Techniques for Adhesive Cementation of All-Ceramic Systems.

Background and Objectives: Modern esthetic dentistry is based on all-ceramic restorations. Dentists still have reservations about using these restorations due to a lack of understanding of the cementation technique, which depends on the type of ceramic used. The aim of the study is to evaluate the approaches and practices of clinicians regarding the adhesive cementation of all-ceramic restorations. Materials and Methods: An online questionnaire regarding the use of all-ceramic restorations and their bonding methods was designed by distinguishing the cementation of oxide and silica-based ceramics. The survey included dentists practicing in Timiș County, Romania. The questionnaire and the evaluation of the answers were designed based on the techniques and evidence from the literature. Results: Considering the work experience, we obtained two groups: group 1—1 to 6 years and group 2—6 to 9+ years. The results revealed significant values when comparing the two groups in the surface protocol and decontamination (p = 0.005), type of cement used (p = 0.002), and isolation techniques (p = 0.002). Conclusions: The results show that many clinicians need additional training to improve their cementing technique and avoid the confusion caused by insufficient information about the interrelationship between the type of ceramic and the cementation procedure.

An In Vitro Study to Evaluate the Effect of Artificial Aging on Translucency, Contrast Ratio, and Color of Zirconia Dental Ceramic at Different Sintering Levels

Increasing demands for aesthetically pleasing dental restorations have promoted the use of materials that display superior optical properties. Zirconia-based all-ceramic systems have good optical properties, thus providing the desired esthetics for dental restorations. The altered oral conditions impact the physical properties of these materials. Multiple studies have been conducted to evaluate the effect of aging on the mechanical properties of computerized-aided design and computerized-aided manufacturing (CAD/CAM)-based zirconia; however, there is a scarcity of literature discussing the effect of aging on change in translucency, contrast ratio, and color. Therefore, this research aimed to evaluate the effect of accelerated artificial aging on translucency parameter (TP), contrast ratio (CR), and color of CAD/CAM zirconia at different sintering temperatures. Twenty-eight rectangular-shaped specimens were obtained by CAD/CAM milling of zirconia blank. Sintering of the samples was carried out at four different temperatures 1350 °C, 1400 °C, 1450 °C, and 1500 °C, respectively. Thermocycling of the samples was performed in a thermocycler. TP, CR, and color evaluation of all the samples was done again using a Spectrophotometer. Data acquired were statistically evaluated by one-way ANOVA and Post Hoc test. The highest amount of change in TP was recorded for specimens sintered at 1400 °C (1.86), whereas the least change was attributed to 1350 °C (0.51). The highest change in CR was observed in specimens sintered at 1500 °C (0.0971), and the least change in CR was observed at 1450 °C (0.0086). The highest ΔE values were recorded for 1400 °C against both white (1.86) and black background (2.17), whereas the least change was attributed to 1350 °C against white (0.86) and against a black background (1.41). The changes in TP were significant, but CR did not show any significant change. ΔE values for all the experimental groups were significant, but were below the clinically perceptible range. An increase in sintering temperature increased the translucency.

Varied Simulation-based Stress Analyses on Zirconia All-ceramic Crowns

The development of high-strength ceramics and its use in posterior areas has been a field of constant investigation. The performance of all-ceramic molar crowns fabricated with new CAD/CAM techniques is a subject of interest. The studies available in literature focused on the analysis of all-ceramic restorations failures, investigating several parameters involved on the tooth structure. The goal of this study was to investigate the stress distributions of zirconia - all ceramic crowns, under loads using varied stress distribution analyses. A static structural analysis was performed to calculate the stress distribution using the computer-aided engineering software. Equivalent stresses were recorded in the tooth structures and in the restoration for all these designs. Since ceramic materials exhibit brittle behavior, the first principal stress criterion was adopted to compare the stress values and distribution with those obtained for the first simulations. Under the same loading conditions, the stress distribution patterns for the zirconia all-ceramic crown using differential stress analyses exhibited similarities. Only the values are lower for the maximal principal stresses. The present study suggests that varied simulation methods are promising to assess the biomechanical behaviour of all-ceramic systems.

Effect of Luting Cement and Convergence Angle of the Preparation on the Internal Fit of Zirconia Restorations.

The objective was to evaluate the effect of luting agents and the preparation design on the internal fit of zirconia restorations. Sixty dies were prepared and divided in occlusal convergence angle of 6° (OC6) and 12° (OC12). CAD/CAM zirconia copings were fabricated (Lava All-Ceramic System). A zinc phosphate cement (ZPC); a glass ionomer cement (GIC); and a resin cement (RC) were studied. Specimens were sectioned and coping/die discrepancies were evaluated through Stereoscopic Microscopy. A closer fit was observed in OC12 when compared to OC6 (p < 0.001). For OC6 no significant differences were observed in between ZPC, GIC, and RC (p > 0.05). For OC12, a significantly closer fit was recorded on the ZPC subgroup when compared to the GIC subgroup (p < 0.001). Preparations of 12 degrees demonstrated a closer internal fit when compared to 6 degrees. Preparations of 12 degrees achieved better internal fit values with ZPC (Fortex) followed by RC (RelyX Unicem), and GIC (Ketac Cem). No differences were found when comparing different luting agents over 6° degrees preparations.

Translucency of HT lithium disilicate specimens with different thicknesses – preliminary study

Introduction The main advantage of using an all-ceramic system is to achieve a superior aesthetic result by increasing the translucency [1]. When dealing with darkened substrates, it is important to understand the level of translucency of the restorative materials according to their thickness, in order to adapt their application to specific clinical situations. Studies evaluating the translucency of different thicknesses of lithium disilicate, for CAD/CAM technology, are limited. This study aims to evaluate and compare the translucency of high translucency (HT) lithium disilicate with different thicknesses. Materials and methods Lithium disilicate blocks IPS e.max® CAD HT (Ivoclar Vivadent®), shade A3, were sintered in a furnace (Vita Vacumat 6000 MP). The sintered blocks were cut, with a hard tissue microtome (Accutom-50; Struers Inc), in quadrangular specimens (n = 20). Four subgroups (n = 5) were defined, according to thickness (0.5, 1.0, 1.5, and 2.0 mm). The translucency of the specimens was measured using the spectrophotometer SpectroShade Micro (MHT S.p.A., Arbizzano di Negar, Italy) (λ = 410–680 nm). All measurements were made from 6 different areas of each specimen against a white background (Comission Internationale de L’Eclairage (CIE) L*=94.5, a*=–0.3, b*=–1.5) and against a black background (CIE: L*=6.1, a*=1.4, b*=–4.0), in order to obtain their L* (value coordinate), a* (red-green coordinate) and b* (yellow-blue coordinate) values under natural light (D65) [2,3]. Based on the obtained values, the translucency was calculated using the translucency parameter (TP) and the contrast ratio (CR) formulas [4]. Resulting TP and CR data were submitted to descriptive statistical analysis. Results Mean TP values ranged from 15.5 (±0.4) to 31.6 (±2.3) and mean CR values ranged from 0.65 (±0.03) to 0.84 (±0.01). Thinner thicknesses showed higher translucency. Discussion and conclusions Translucency is a fundamental optical property and a determinant factor when it comes to selecting the restorative material for highly aesthetical areas. This study had, therefore, the purpose of understanding which data may or may not be useful in clinical practice. The dentist should be familiar with the properties and characteristics of new and innovative materials in order to pick the one that better adapts to a certain clinical situation [3]. HT Lithium disilicate specimens showed that as thickness decreases, translucency values increase.

Ocena szczelności brzeżnej elementów antyrotacyjnych w układzie implant – łącznik hybrydowy oraz implant – łącznik całoceramiczny

Ocena szczelności brzeżnej elementów antyrotacyjnych w układzie implant – łącznik hybrydowy oraz implant – łącznik całoceramiczny

Effect of different liner techniques and argon plasma treatment of zirconia base on the adhesion and color change of veneering ceramic

This in vitro study aimed to investigate the bond strength and discoloration between the zirconia framework and veneer ceramic applied after liner and argon plasma treatment with two different techniques. A total of 200 zirconium substructures of 12 mm length, 10 mm width, and 0.7 mm thickness were divided into five subgroups for the application of different thicknesses of liner: C (no liner application), L1 (0.1 mm), L2 (0.2 mm), L3 (0.1 mm + 0.1 mm) and LA (0.1 mm + 0.1 mm + argon plasma). The zirconia substructures were fabricated by two different techniques (A: layering, B: press-on). The specimens of the three subgroups Control, Group L3, and Group LA were tested for color difference. Color parameters were measured using a spectrophotometer before and after thermal cycling, and differences (CIEDE 2000 [ΔE00]) were calculated. The shear bond strength was applied to all subgroups using a universal testing machine. The data were analyzed statistically using the Shapiro–Wilk, Levene, and Kruskal–Wallis tests. The interface and fractured surfaces of the specimens were also evaluated by scanning electron microscopy (SEM). Significant differences were found between the groups (p < 0.05) in terms of shear bond strength and color differences (p < 0.001). Group LA showed significantly higher bond strength and color stability than the other groups (p < 0.001). The results of the study demonstrated that the application of liner and argon plasma between the upper and lower structures of all-ceramic systems significantly affects the bond strength and final colour of the restorations.

Effect of substrate and cement on the final color of zirconia-based all-ceramic crowns.

To evaluate the influence of the substrate and the cement on the final color of ceramic crowns. Prosthetic crowns (framework + porcelain) were fabricated using two all-ceramic systems (YZ, 3mol% yttria-stabilized tetragonal zirconia; IZ, alumina-based zirconia-reinforced glass-infiltrated ceramic) and a metal-ceramic system (MC; n=8). Metal (M) and resin (R) were used as substrate abutments. For R substrate, crowns were evaluated as seated (R) and after cementation (R-C). CIELAB color coordinates were obtained using a dental spectrophotometer with D65 light illumination. CIELAB, CIEDE2000 (1:1:1) and CIEDE2000 (2:1:1) color difference metrics were used. Data were analyzed using 95% confidence intervals and compared to perceptibility (PT) and acceptability (AT) thresholds. The , ∆E00 (1 : 1 : 1), and ∆E00 (2 : 1 : 1) values of the restorative systems evaluated using different substrates (M.R) were similar to the AT values of each metric. When non-cemented and cemented crowns were evaluated (R.R-C), MC had color difference values at PT and below AT; while YZ and IZ showed similar values to AT, for and ∆E00 (1 : 1 : 1) metrics. The substrate and cement affected the final color of zirconia-based all-ceramic crowns, but the color differences corresponded to an acceptable match. As both substrate and cement influence the final color of multi-layered ceramic prosthesis, dentists and dental technicians should understand the optical properties of dental ceramics to reproduce the natural appearance of dental structures and maximize the chance for excellent color matches.

Effect of Repeated Firings on the Color Change and Surface Roughness of Two All-ceramic Systems

Purpose: This study aimed to evaluate the effect of repeated firings on the color change and surface roughness of two all-ceramic systems. Materials and Methods: Forty disc shaped ceramic specimens ( 10 mm x 1 mm ) were fabricated from two commercially available all-ceramic system (IPS E.max press, Ivoclar-Vivadent, Schaan, Liechtenstien, Germany and zirconia Nacera Pearl, DOCERAM Medical Ceramics, Germany) (N=20). Color measurement of the specimens was made using Reflective spectrophotometer and surface roughness (Ra) was measured using USB digital profile guage, (Elcometer 224/2, Elcometer Instruments, Great Britain) after 1, 3, 5 and 7 repeated firing. Results: The mean color change (ΔE) was clinically acceptable for both types of ceramics. As regards the effect of ceramic material on (ΔE), e.max showed statistically significantly higher mean color change (ΔE) than Zirconia. As regards the effect of repeated firings on (ΔE), 7 repeated firings showed statistically significantly higher mean (ΔE) than 5 repeated firings which in turn showed statistically significantly higher mean (ΔE) than 3 repeated firings. Surface roughness measurements showed that there were significant difference between E.max and zirconia and that zirconia showed higher mean (Ra) than e.max. Also the results of the current study showed that there were a significant difference between mean (Ra) and numbers of firing as roughness decrease with increasing the number of firing. Conclusions: Repeated firings negatively affecting the color change and surface roughness and should be minimized as possible.

Effect of Surface Treatment and Type of Resin Cement on Marginal Fit of Zirconia Crowns

“As esthetic restorative materials for crowns and fixed partial dentures (FPDs), all-ceramic systems can be used as alternatives...

Full Ceramic Aesthetic Applications: 3 Case Reports

One of the most important issue of today’s dentistry is the preservation of tooth structure. Following biomimetic principles, employing minimally invasive applications and adhesive technologies are of paramount importance for successful restorations. Ceramics are materials that allow minimally invasive approach in the anterior region. As ceramic materials develop and patients demand for aesthetic restorations goes up, practitioners must keep up with the material science. The authors suggest guidance to the practitioner in selecting the proper all-ceramic systems for crowns when faced with different aesthetic desires. In this article, three cases of full ceramic restorations were obtained by different production techniques are presented.

The effects of core material and cooling rate on fabrication defects in the veneer of bi-layered all-ceramic systems

Abstract The purpose of this study was to investigate the effects of framework thickness and cooling rate on the characteristics of fabrication defects in veneer ceramic of bi-layered lithium disilicate glass-ceramic (LDG) and zirconia. Eighty discs of 0.5-mm- and 1.0-mm-thick LDG/zirconia core were manually fabricated and veneered. Samples were divided into 8 groups according to the cooling rate, core material and core thickness, with 10 samples per group. All discs were scanned by micro-CT and 3D-reconstructed. Volume, position and sphericity of each pore defect were measured, and curves were fitted. Pore defect sizes of all samples were algorithm-fitted in two groups: 95% small defects and the rest large defects. Pore defects in veneer in LDG groups were smaller, rounder and farther from the interface with the core (p 0.01), yet the pores in 1.0-mm-thick veneer in the zirconia core group were smaller, closer to the veneer surface, and rounder than in the 0.5-mm-thick group (p

An in vitro study to compare the influence of different all-ceramic systems on the polymerization of dual-cure resin cement.

Aim:The aim of the study is to compare the effect of composition of three different all-ceramic systems on the polymerization of dual-cure resin cement, using different curing cycles and evaluated immediately within 15 min and after 24 h.Materials and Methods:Resin cement disc samples were fabricated by polymerization through three different all-ceramic disc, namely: lithium disilicate discs – IPS e.max (Group B), leucitereinforced discs – IPS Empress (Group C), zirconia discs – Cercon (Group D), and without an intervening ceramic disc, as control (Group A). A total of 80 resin cement disc samples were fabricated for fur groups (n = 20). Each group further consisted of two subgroups (n = 10), t10 and t20 according to two different exposure times of 10 and 20 s, respectively. Each of the 80 resin disc samples was evaluated for their degree of polymerization achieved, by measuring the microhardness(Vickers hardness number) of the samples immediately within 15 min and after 24 h, giving us a total of 160 readings. Oneway analysis of variance test, ttest, and paired ttest were used for multiple group comparisons followed by Tukey's post hoc for groupwise comparison.Results:Direct activation of the resin cement samples of control (Group A) showed statistically significant higher mean microhardness values followed by Groups C then B and D, both immediately and after 24 h. The mean microhardness for immediate post-activation was always inferior to the 24 h post-activation test. For both 10 and 20 s curing cycle, there was a significant increase in the microhardness of the resin cement discs cured for 20 s through the different ceramics.Conclusion:Ceramic composition affected the polymerization of dual cured resin cement. Doubling the light irradiation time or curing cycle significantly increased mean microhardness value. Greater degree of conversion leading to an increase in hardness was observed when the resin cement discs were evaluated after 24 h.

Analyzing strain in samples with all-ceramic systems using the digital image correlation technique

Introduction/Objective. The study was conducted to identify the maximum strain generated in the samples composed of poly-methyl-methacrylate, StraumannR implants, and three types of ceramic systems. Methods. Three types of experimental models were used, loaded by external load of 100 N, 300 N, and 500 N and analyzed using the digital image correlation method. The models were composed of yttriastabilized zirconia, e.max lithium disilicate, and Vita EnamicR hybrid ceramics, placed on the StraumannR cylindrical dental implant systems (4 ? 10 mm) with straight abutments. Results. Significant differences in strain values between samples with different crown material groups were detected (p = 0.000). This suggests that strain values were dependent on the type of crown material. Strain values were also affected by the region of interest (p = 0.000). Application of two-way ANOVA enabled testing of the interaction effect between two independent variables, crown material and region of interest, where a significant difference was also found (p = 0.046). This indicates that strain values were also influenced by different combinations of material type and region of interest. The highest strain values were found for Z (0.383 ? 0.015) in the apical region, and the lowest for E (0.303 ? 0.015) in the middle region. Conclusion. The study shows maximum strain in the apical and marginal directions. When considered various all-ceramics, we noticed the minimum strain below Vita EnamicsR, while the maximum strain was found in samples with yttria-stabilized zirconia crown.

Fracture resistance of monolithic and veneered all-ceramic four-unit posterior fixed dental prostheses after artificial aging.

This study compared the fracture resistance of monolithic and veneered all-ceramic four-unit posterior fixed dental prostheses (FDPs) generated by computer-aided design/computer-aided manufacturing (CAD/CAM) after aging in a mastication simulator. Four-unit FDPs were designed from six different all-ceramic systems: 1) monolithic lithium disilicate (M-E), 2) monolithic zirconia (M-TZI), 3) veneered zirconia by conventional layering (V-L), 4) veneered zirconia by lithium disilicate pressing (V-P), 5) veneered zirconia by lithium disilicate fusing (CAD-F-E), and 6) veneered zirconia by feldspathic ceramic cementing (CAD-C-CB). The specimens were divided into control and aging groups (n = 10 per group). The aging process included both thermocycling and mechanical loading and was followed by fracture resistance testing. All specimens in the M-E, M-TZI, and V-L groups survived; however, all specimens in the V-P group were fractured during artificial aging. The highest fracture resistance values were observed in the M-TZI group. According to the fracture resistance test, connector fractures were the most frequent type of failure. M-TZI and M-E FDPs revealed no failures during aging and showed higher fracture resistance than the veneered groups. Among the veneered zirconia framework groups, V-L FDPs showed the highest success rate during aging, while the fracture resistance was similar among all the veneered zirconia groups.

An Overview of the Development and Strengthening of All-Ceramic Dental Materials

High-strength all-ceramic systems for fixed partial dentures (FPDs) are necessary for replacing missing teeth. The ability to fabricate a restoration outside the mouth and subsequently integrate it with a tooth extends the range of materials available to be utilized by a dentist. This article presents a review of the development of all-ceramic restorations, including the evolution and development of materials, technologies and how to improve the strength of all-ceramic restorations, with respect to survival, applications, strength, color, and aesthetics. New core/framework materials have developed and evolved over the last decade because of the growth of ceramic materials and systems currently available for utilization. A search of English language reviewed literature was undertaken, which focused on the evidence-based published research articles. This review also elucidates the various all-ceramic materials and systems currently available for clinical use, and that no single universal material or system exists for all clinical cases. Successful implementation depends on the clinicians, materials, manufacturing techniques, and individual clinical condition. Further longitudinal clinical studies are recommended for the development of ceramic materials and systems.

Effect of Veneering Techniques on Shear and Microtensile Bond Strengths of Zirconia-Based All-Ceramic Systems.

To evaluate shear (SBS) and microtensile (μTBS) bond strengths of zirconia cores veneered using different fabrication techniques. Seventy-five IPS e.max ZirCAD plates were fabricated and divided into three groups according to the following veneering techniques: layering, pressing, and CAD-on. The specimens of the layering group were veneered with IPS e.max Ceram, and the specimens of the pressing group were veneered with IPS e.max Zir- Press. Veneering ceramics in the CAD-on group were milled from IPS e.max CAD, fused with the core by using a glass-fusion ceramic, and then crystallized. Bond strength tests were performed using a universal testing machine at a crosshead speed of 0.5 mm/min for the SBS test and 1 mm/min for the μTBS test. Mean SBS and μTBS (MPa) were analyzed with one-way ANOVA and Tukey's HSD test (p < 0.05). Significant differences in SBS were observed between the groups (p < 0.05). The mean SBS for the CAD-on group was significantly higher (31.89 ± 5.83 MPa) than those of the layering (14.27 ± 4.45 MPa) and pressing (12.23 ± 3.04 MPa) groups. However, the mean μTBS of the CAD-on (30.41 ± 8.64 MPa), layering (21.71 ± 3.40 MPa) and pressing (20.74 ± 6.36 MPa) groups were not statistically significant (p > 0.05). The CAD-on technique showed the highest shear bond strengths of the tested groups, and most of the specimens failed cohesively instead of failing at the adhesive interface.

Influence of thermal and mechanical fatigue on the shear bond strength of different all-ceramic systems.

BackgroundTo evaluate the influence of thermal and mechanical fatigue on the shear bond strength of different all-ceramic cores and veneering porcelain interfaces.Material and MethodsAll-ceramic systems tested were lithium disilicate and zirconia veneered by layering technique. Sixty specimens (n=20) were subjected to shear bond strength. Ten of them were thermal and mechanical cycled. Fracture analysis was performed with stereomicroscopy and scanning electron microscopy. Energy dispersive X-ray spectroscopy analysis was performed across core/veneer interfaces.ResultsThermal and mechanical cycling did not influence on bond strength. However, there was significant difference among systems (<0.01). CoCr group presented the highest values, followed by lithium disilicate, and zirconia. Failure modes were predominantly adhesive for CoCr, cohesive in core for lithium disilicate, and cohesive in veneer for zirconia. Energy dispersive X-ray showed interaction zone for CoCr and lithium disilicate groups and was inconclusive for zirconia. Fatigue had no influence on bond strength of groups tested.ConclusionsThe results suggest that there is a chemical bond between core and veneer materials for CoCr and lithium disilicate groups. Key words:Ceramics, electron microscopy, fatigue, mechanical stress, shear bond strength.