Post Core Materials Research Articles

Comparative analysis of stress distribution in residual roots with different canal morphologies: evaluating CAD/CAM glass fiber and other post-core materials

BackgroundThe selection of post-core material holds significant importance in endodontically treated teeth, influencing stress distribution in the dental structure after restoration. The use of computer-aided design/computer-aided manufacturing (CAD/CAM) glass fiber post-core possesses a better adaptation for different root canal morphologies, but whether this results in a more favorable stress distribution has not been clearly established.Materials and methodsThis study employed finite element analysis to establish three models of post-core crown restoration with normal, oversized, and dumbbell-shaped root canals. The three models were restored using three different materials: CAD/CAM glass fiber post-core (CGF), prefabricated glass fiber post and resin core (PGF), and cobalt-chromium integrated metal post-core (Co-Cr), followed by zirconia crown restoration. A static load was applied and the maximum equivalent von Mises stress, maximum principal stress, stress distribution plots, and the peak of maximum displacement were calculated for dentin, post-core, crown, and the cement acting as the interface between the post-core and the dentin.ResultsIn dentin of three different root canal morphology, it was observed that PGF exhibited the lowest von Mises stresses, while Co-Cr exhibited the highest ones under a static load. CGF showed similar stress distribution to that of Co-Cr, but the stresses were more homogeneous and concentrated apically. In oversized and dumbbell-shaped root canal remnants, the equivalent von Mises stress in the cement layer using CGF was significantly lower than that of PGF.ConclusionsIn oversized root canals and dumbbell-shaped root canals, CGF has shown good performance for restoration of endodontically treated teeth.Clinical relevanceThis study provides a theoretical basis for clinicians to select post-core materials for residual roots with different root canal morphologies and should help to reduce the occurrence of complications such as root fracture and post-core debonding.

Biomechanical Analysis of Mandibular Premolar Restored with Different Custom Post Core

Abstract Objective This study investigated biomechanical behavior of custom post core made of six different materials on the tooth with and without the ferrule under different occlusal load. Materials and Methods Three-dimensional models of mandibular first premolar, with and without ferrule, reconstructed from micro-computed tomography image are restored with different custom post core and zirconia crowns. By using the finite element analysis, von Mises stress shown in MPa was measured under simulated axial and oblique load of 200 [N]. To compare the stress distribution, six different custom post core materials were chosen: zirconia, Ni-Cr alloy, gold alloy, glass fiber-polyether ether ketone, polyether ether ketone, and carbon fiber-polyether ether ketone. Results Custom post cores with a higher modulus of elasticity showed higher measured stress in the posts, but less stress in dentin. Measured stress in custom post core under oblique loading was approximately three times higher compared with axial loading. Stress in custom post core and in dentin under both types of loads was slightly higher in teeth without ferrule effect. Conclusion The use of custom cast post cores made of different alloys is recommended in restoration of endodontically treated teeth, with extensive loss of tooth structure especially in teeth without ferrule effect.

Effect of Ferrule Design on Stress Distribution of Maxillary Incisor Rehabilitated with Ceramic Crown and PEEK Post–Core Material: A 3D Finite Element Analysis

Endodontic-treated teeth with massive degrees of coronal tissue loss usually require rehabilitation with post-retained unitary crowns. This study aimed to evaluate the effect of ferrule design on the stress distribution of maxillary incisors rehabilitated with zirconia crowns using finite element analysis. Six three-dimensional models were generated according to the presence and location of ferrule (No Ferrule, Buccal Ferrule, Lingual Ferrule, Buccolingual Ferrule, and Full Ferrule). The post–core materials tested were Nickel–chromium (NiCr) and Polyetheretherketone (PEEK). A static load of 100 N at a 45-degree angle on the Lingual surface, in a region 2 mm below the incisive ridge, was applied. Von Mises stresses and contour plots of all of the models were collected and analyzed. A lower and more uniform stress distribution was observed in the Full Ferrule model compared with the remaining models. A reduction of 72% in the von Mises peak stresses was observed in the root when comparing the Full Ferrule and No Ferrule models, both with PEEK post–core material. In conclusion, the presence of an incomplete ferrule is beneficial to the stress distribution in restored post-retained crowns. The use of PEEK for post–core structures reduces the stress concentration on the posts, reducing the predisposition to irreparable root fracture.

Mechanical properties, biosafety, and shearing bonding strength of glass fiber–reinforced PEEK composites used as post-core materials

ObjectiveTo investigate the mechanical properties, biosafety, and shearing bonding strength of glass fibers–reinforced polyether-ether-ketone (PEEK-GF) for post-core materials. MethodsPEEK-GF composites with different glass fiber contents were prepared by extrusion injection and named PEEK-GF30, PEEK-GF40, and PEEK-GF50. Mechanical properties including flexural modulus, flexural strength, Vickers hardness, and compression strength were tested. The cross-sectional morphology was examined using scanning electron microscopy (SEM). Cytotoxicity was studied in vitro with Cell-counting kit-8 (CCK-8). Cell morphology was observed under a microscope. Cell growth on the composites’ surfaces was analyzed with DAPI staining. The shearing bonding strength (SBS) of PEEK-GF50 was assessed after applying different pretreatments. Failure modes were evaluated by microscopy. SEM and contact-angle measurements were performed on the surfaces. Statistical analysis was conducted using one-way ANOVA (P < 0.05). ResultsThe mechanical properties of PEEK-GF composites improved with increased GF content. The PEEK-GF50 group exhibited flexural modulus (17.4 ± 0.5 GPa) close to that of dentin (18.6 GPa) and showed the highest flexural strength (350.0 ± 2.9 MPa), Vickers hardness (47.6 ± 4.5 HV), and compressive strength (264.0 ± 18.0 MPa). The SEM analysis demonstrated that the PEEK matrix combined well with glass fibers. The CCK-8 results confirmed the biosafety of all groups. DAPI staining indicated that cells were growing well on the composites’ surface. The sample that was pretreated with sandblasting and plasma showed the highest SBS (16.0 ± 1.7 MPa). SignificanceThe PEEK-GF composites demonstrated excellent mechanical properties, biosafety, and SBS, and have great potential to serve as post-core materials.

Fracture Resistance of Different Post-Core Systems: An In vitro Study.

Reasons for the failed endodontic teeth which had an extensive restoration can be attributed to the multiple materials that were used in it. Various post-core materials that are commonly used are compared for fracture resistance in the current study. Fourty maxillary incisors that needed root canal therapy were allocated into four groups of 10 each. Using adhesive resin cement, teeth were repaired in three experimental groups with ceramic fiber post, glass post, and stainless steel post. All these posts with composite post and core. Samples that still had their coronal structure were considered as controls that were without any post-cores. Every sample was ready for the best abutment preparation. Using the universal testing machine, all the specimens were examined for the compressive strength at 130° until fracture was experienced. The data for the force levels at which the fracture occurred were noted and compared for significance using analysis of variance (ANOVA), keeping P < 0.05 as significant. The fracture resistance values were significantly variable among all the groups, with P < 0.05. The stainless steel post exhibited the highest strength before it succumbed to the fracture. The glass posts showed better restorability and were esthetically acceptable. The least fracture resistance was demonstrated by teeth that had no post-core, highlighting the necessity of strengthening the tooth. Among all the experimental groups, the one that demonstrated the highest fracture resistance was composite core and steel posts.

Evaluation of stress distribution in maxillary central incisor restored with different post materials: A three-dimensional finite element analysis based on micro-CT data

Aim: Post-core restorations have been developed to restore and re-functionalize endodontically treated teeth. Today, post-core materials used to show stress distribution similar to a solid tooth are still being researched. This study aimed to compare the von Mises stress (σvm) distributions created by the Zirconium post (ZP), Titanium post (TP), and Glass Fiber post (GFP) materials in the permanent maxillary central incisor using finite element stress analysis (FEA).&#x0D; Methodology: A permanent maxillary central incisor tooth scanned using microcomputed tomography (µCT) was reconstructed, and a three-dimensional model was created. To these models, ZP, TP, and GFP were applied. Composite resin was modeled as the core structure and ceramic crown as the superstructure. Using FEA, 100 N static force was applied in three directions with vertical (F1-0°), oblique (F2-45°), and horizontal (F3-90°) angles to the models whose restoration was completed. As a result of the applied forces, the stresses on the dentine model (Dm), post model (Pm), and the cement model in between the dentine and the post (Cm) were compared.&#x0D; Results: The maximum von Mises stress (σvm max) distribution under F1 for Dm was: ZP = 6,07888 MPa, TP = 6,35719 MPa and GFP = 6,81946 MPa. The σvm max distribution under the force F2 for Dm was: ZP = 26,6542 MPa, TP = 27,3694 MPa, and GFP = 28,4495 MPa. The σvm max distribution under the force F3 for Dm was: ZP = 34,7371 MPa, TP = 34,9828 MPa, and GFP = 35,287 MPa.&#x0D; The σvm max distribution under the force F1 for Pm was: ZP = 17,0361 MPa, TP = 13,1567 MPa, and GFP = 7,85452 MPa. The σvm max distribution under the force F2 for Pm was: ZP = 73,7999 MPa, TP = 52,0089 MPa, and GFP = 25,9903 MPa. The σvm max distribution under the force F3 for Pm was: ZP = 78,8934 MPa, TP = 55,0424 MPa, and GFP = 27,1787 MPa.&#x0D; The σvm max distribution under the force F1 for Cm was: ZP = 7,95074 MPa, TP = 6,66092 MPa, and GFP = 4,60832 MPa. The σvm max distribution under the force F2 for Cm was: ZP = 16,8296 MPa, TP = 16,8514 MPa, and GFP = 16,526 MPa. The σvm max distribution under the force F3 for Cm was: ZP = 17, 5577 MPa, TP = 16,891 MPa, and GFP = 16,5209 MPa.&#x0D; Conclusion: In all three forces, the highest σvm max was at ZP, and the least was at GFP. ZP and TP accumulated forces internally rather than transmitting them to the tooth tissue. GFP distributed the forces more homogeneously to the dentine.&#x0D; &#x0D; How to cite this article: Yeniçeri Özata M, Adıgüzel Ö, Falakaloğlu S. Evaluation of stress distribution in maxillary central incisor restored with different post materials: A three-dimensional finite element analysis based on micro-CT data. Int Dent Res 2021;11(3):149-57. https://doi.org/10.5577/intdentres.2021.vol11.no3.3&#x0D; &#x0D; Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.&#x0D;

Comparison of the fracture strength of endodontically treated teeth restored with polyether ether ketone, zirconia and glass-fibre post-core systems.

This study aimed to compare the fracture resistance and fracture mode of maxillary central incisors restored with four different sizes and three different post-core systems. One hundred and twenty maxillary incisors were endodontically treated and randomly divided into three groups (12 subgroups). Post cavities for the narrow subgroups were prepared with 1.4-mm-diameter drills in lengths of 7.5mm (SN) and 10mm (LN). Post cavities for the wide subgroups were prepared with 1.6-mm-diameter drills in lengths of 7.5mm (SW) and 10mm (LW) (n=10). Group F was restored with glass-fibre post and composite resin core, Group P was restored with custom PEEK post-core and Group Z was restored with custom zirconia post-core. All posts were cemented with a dual-cure resin cement. Zirconia copings were cemented. Specimens were loaded on the palatal surface with a universal testing machine, and the fracture strengths of the teeth were statistically analysed using ANOVA and post hoc Tukey tests. Statistically significant differences existed between the fracture strengths of the post materials. The highest fracture strength was in Group F, and the lowest was in Group P. Evaluation of the fracture strengths of the post lengths and diameters demonstrated that the short-narrow group of Group Z had the lowest fracture strength (P<.05). The long-wide group of Group F showed the highest fracture resistance. In Group P, no statistically significant difference existed between the post-cores of different dimensions (P>.05). Irreparable fractures were observed mostly in Group Z, and decementation was more common in Group P. PEEK post-cores showed sufficient fracture strength for the anterior region, similar to the other two post-core materials. PEEK post-cores showed more decementation and repairable fractures at lower forces, while restoration failure was mostly catastrophic for glass-fibre and zirconia posts.

Influence of post-core material and cement peculiarities on stress of post-cores under ultrasonic vibration: a three-dimensional finite element analysis.

To analyse the effect of post-core, and cement materials and thickness of the cement lute on the stress in post-core systems under ultrasonic vibration at different frequencies and amplitudes using three-dimensional finite element analysis. Eight three-dimensional finite element models of a maxillary central incisor with post-cores were established. Two post-core materials (Au and Ni-Cr alloys), two cements (glass ionomer (GI) and zinc phosphate (ZP)) and two cement layer thicknesses (50 and 150μm) were considered. Vibration loads were applied near the neck on the buccal side of the core at frequencies of 10-40kHz and amplitudes of 10-50μm. The maximum shear stress of the cement layer and maximum principal stress of the roots and their distributions were investigated. The stresses on cements and roots increased with an increase in the frequency and amplitude of the vibration load and elastic modulus of the cements, and decreased with increasing thickness of the cement layer and elastic modulus of the post-core. Maximum cement stress was observed on the contralateral upper part of the loading side, whereas the maximum root stress was found on the ferrule where the load was applied. In this simulated model, the frequency and amplitude of ultrasound needed to remove a post-core were positively related to the elastic modulus of the post-core and thickness of the cement layer and negatively related to the elastic modulus of the cements.

Fatigue failure load of immature anterior teeth: influence of different fiber post-core systems.

The aim was to explore the fracture-behavior, survival and marginal-microgaps within the root-canal of immature anterior teeth restored with different fiber-reinforced post-core composites (FRCs). 180 bovine-incisors were randomly divided into 6 groups (n = 30). One group served as control (group 6). The rest of the teeth were prepared to an internal diameter of 1.6mm and the apex was sectioned. After application of an MTA-plug, teeth were restored with FRC materials: Group 1: Bioblock technique with short fiber-reinforced composite (SFRC); Group 2: Bioblock technique with flowable SFRC; Group 3: Individually-made FRC post; Group 4: Conventional FRC post; Group 5: dual-cure core build-up composite. After restorations were completed, teeth (n = 5/group) were sectioned and then stained. Specimens were viewed under a stereo microscope and the percentage of microgaps within the root-canal was calculated. Fatigue-survival was measured using a cyclic-loading testing machine in the rest of the specimens. Flowable SFRC application in the root-canal (Group 2) did not differ from intact-teeth regarding fatigue-survival (p > 0.05). The rest of the groups produced significantly lower survival (p < 0.05) compared to intact-teeth. Post/core restorations made from conventional FRC post (Group 4) exhibited a high number of microgaps (38.3%) at the examined interphase in the root-canal. The restoration of immature incisors with the use of flowable SFRC as post-core material displayed promising performance in a matter of fatigue-resistance and survival.

Fracture resistance and marginal gap formation of post-core restorations: influence of different fiber-reinforced composites

ObjectivesThe aim was to explore the fracture behavior and marginal gap within the root canal of endodontically treated (ET) premolars restored with different fiber-reinforced post-core composites (FRCs). Further aim was to evaluate the composite curing at different depths in the canal.Materials and methodsEighty-seven intact upper premolars were collected and randomly divided into six groups. After endodontic procedure, standard MOD cavities were prepared and restored with their respective fiber-reinforced post-core materials: group 1: prefabricated unidirectional FRC-post + conventional composite core; group 2: prefabricated unidirectional FRC-post + short fiber composite (SFRC) core; group 3: individually formed unidirectional FRC-post + conventional composite core; group 4: randomly oriented SFRC directly layered as post and core; group 5: individually formed unidirectional FRC + randomly oriented SFRC as post and core. After restorations were completed, teeth (n = 3/group) were sectioned and then stained. Specimens were viewed under a stereo microscope and the percentage of microgaps within the root canal was calculated. Fracture load was measured using universal testing machine.ResultsSFRC application in the root canal (groups 4 and 5) showed significantly higher fracture load (876.7 N) compared to the other tested groups (512–613 N) (p < 0.05). Post/core restorations made from prefabricated FRC-post (group 1) exhibited the highest number of microgaps (35.1%) at the examined interphase in the root canal.ConclusionsThe restoration of ET premolars with the use of SFRC as post-core material displayed promising performance in matter of microgap and load-bearing capacity.Clinical significanceFracture resistance of ET premolar restored by bilayered composite restoration that includes both SFRC as post-core material and surface conventional resin seems to be beneficial.

Biomechanical Evaluation of a Tooth Restored with High Performance Polymer PEKK Post-Core System: A 3D Finite Element Analysis.

The aim of this study was to evaluate the biomechanical behavior and long-term safety of high performance polymer PEKK as an intraradicular dental post-core material through comparative finite element analysis (FEA) with other conventional post-core materials. A 3D FEA model of a maxillary central incisor was constructed. A cyclic loading force of 50 N was applied at an angle of 45° to the longitudinal axis of the tooth at the palatal surface of the crown. For comparison with traditionally used post-core materials, three materials (gold, fiberglass, and PEKK) were simulated to determine their post-core properties. PEKK, with a lower elastic modulus than root dentin, showed comparably high failure resistance and a more favorable stress distribution than conventional post-core material. However, the PEKK post-core system showed a higher probability of debonding and crown failure under long-term cyclic loading than the metal or fiberglass post-core systems.

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

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

Comparison of influence of resin core on overall bending strength of fiber post-core restoration

Objective To compare the influence of resin core on overall bending strength of fiber post-core restoration. Methods 60 mandibular first premolar extracted because of orthodontic treatment was selected.3M light -cured composite resin P60,medental dual-cured resin,pulpdent dual-cured resin combined with viva carbon fiber reinforced glass fiber post were applied.The changes of teeth in vitro were observed when strength was given on. Results The flexural strength of 3M light-cured composite resin was(80.182±9.512)N,Medental dual-cured resin was(87.805±11.649)N,Pulpdent dual-cured resin was(85.458±10.845)N.The flexural strength of 3M lightcured composite resin was lower than that of medental dual-cured resin and pulpdent dual-cured resin(t=5.758,3.084,both P 0.05). There was large area of resin broken off after 3M light-cured composite resin core fracture.There was only fracture of medental dual-cured resin core and pulpdent dual-cured resin core. Conclusion The bending strength of dual-cured resin is better than that of highly filled light curing composite resin in large tooth hard tissue defect restoration with fiber post-core, and core broken off is rare. Dual-cured resin is better post-core materials. Key words: Fiber post; Post core crown restoration; Dual-cured resin; Light curing composite resin; Bending strength

Effects of post core materials on stress distribution in the restoration of mandibular second premolars: A finite element analysis

Previous studies have not resolved the question as to which post and core combination optimizes the stress distribution within the post restoration and tooth. The purpose of this study was to determine which post and core combination provides the most favorable stress distribution upon loading. Three-dimensional models of teeth were created with the Ansys program to simulate different materials used for post and cores (Ti, NiCr, AuPd, zirconia, zirconia post/composite resin core, glass fiber post/composite resin core, and carbon fiber post/composite resin core) and metal ceramic crowns (nickel chromium alloy [Group NiCr] and gold palladium alloy [Group AuPd]). A force of 400 N was applied to the occlusal surface, and von Mises equivalent stress values were calculated. Carbon fiber post/composite resin core/metal ceramic crowns with NiCr alloy core had the highest stress values in the weakened root, tooth/post interface, and post. NiCr post/NiCr core/metal ceramic crowns with NiCr alloy core had the lowest stress values in the weakened root and post. The zirconia post and core had the lowest stress value in the tooth/post interface. A post material with a high elastic modulus led to lower stress in the weakened root (approximately 6%) and tooth/post interface (approximately 12%) and to higher stress in the post (approximately 5 times). A composite resin core led to higher stress in the weakened root (approximately 11% to 17%) and lower deformation in the tooth/post interface (approximately 17.5%) and post materials (approximately 24%). Group AuPd resulted in lower stress in the root and high stress in the post (approximately 4.5% to 7%) and affected the amount of deformation in posts with a composite resin core.

Effect of Post-Core Materials on the Color Value of Four Dental All-Ceramic Cores

The aim of this study were to compare the color value of four kinds of dental all-ceramic cores (IPS e.max Press,Zenostar,Lava Zirconia and Upcera Zirconia) on three different post-core materials.All-ceramic core materials were made into samples at the diameter of 10mm and the thickness of 0.50.02mm.Their color value on the post-core material of noble metal,Co-Cr alloy and resin were respectively determined with chromatism instrument.It was showed that the color value of four all-ceramic cores were statistically different.IPS e.max Press was most obviously affected by post-core materials,while Upcera Zirconia the weakest.Lava Zirconia and Zenostar were influenced to a certain degree.In conclusion,non-mental post-core was preferable for IPS e.max Press,Upcera Zirconia was fit for any post-core materials.

Affection of Post-Core Materials on the Resultant Color of Lithium Disilicate Ceramic Restorations

Abstract. The purpose of the study was to evaluate the affection of post-core materials on the resultant color of lithium disilicate ceramic restorations. Twenty disk-shaped core-veneer specimens were prepared with IPS e.max Press and IPS e.max Ceram. Twenty-five substructure specimens were also prepared. Color measurements were performed for all specimens with each substructure by a calibrated spectrophotometer. Lab chromatic values were obtained. The chromatic aberration (△E) compared with dentine substructure was 1.33 for ziconia based combinations , 1.40 for resin based combinations, 4.37 for cobalt chromium alloy based combinations and 3.05 for gold metal alloy based combinations. The zirconia and resin post-core materials are recommended to form substructures for the lithium disilicate ceramic restorations. Cobalt chromium alloy and Gold metal alloy post-core materials are not recommended.

Effect of Background Color on In-Ceram and Cercon All-Ceramic Core Material

The present paper probes into the effect of background color of different post-core materials on the core materials of In-Ceram AL2 Electroformed Alumina, Z21 Electroformed Zirconia, Cercon base color Zirconia, and Cercon base Zirconia. The spectrocolorimeter was used to measure colorimetric values of all groups of samples against the background of noble metal, nickel-chromium alloy, silver amalgam and resin, and to calculate the color difference among the groups. The result showed that the color difference of Cercon base color Zirconia viewed against different backgrounds was identifiable by human eyes (ΔE &gt; 1.5). In contrast, the color differences of In-Ceram AL2 Electroformed Alumina, Z21 Electroformed Zirconia and Cercon base Zirconia viewed against different backgrounds were unidentifiable by human eyes (ΔE &lt; 1.5). Based on this, it can be stated that Cercon base color Zirconia is significantly affected by background color. Thus, proper method to shelter the background color should be adopted. In addition, AL2 Electroformed Alumina, Z21 Electroformed Zirconia, and Cercon base color Zirconia are less influenced by the background color, thus it is not necessary to cover the background color.

Zirconia ceramic post systems: a literature review and a case report

Cast metal post-core systems have a long history of successful use because of their superior physical properties. However, their high elastic modulus can cause stress concentrations within the surrounding radicular dentin, resulting in root fractures. Moreover, the increasing demand for more esthetically appealing and biocompatible restorations has led to the development of tooth-colored, translucent, metal-free post-core systems. Notably, prefabricated zirconia ceramic post systems have been introduced to satisfy this trend toward a heightened awareness of esthetics, whereby the translucency of all-ceramic crowns can be successfully maintained with the use of ceramic post-core materials. Owing to the keen interest in and widespread use of zirconia ceramic post systems, many in vitro studies on zirconia posts have been published in the last 15 years. The aim of this article was to present data about the retention, fracture resistance, microleakage, light transmission, esthetic advantages, and radiodensity of zirconia posts. Two clinical survival rate studies were also presented. Based on the results of these studies, zirconia posts have been shown to improve the esthetic quality of all ceramic crowns and thus their usage is recommended. Apart from literature review, a case report in which a fractured fiber post was replaced with a custom-made zirconia post was also presented.

Effect of Different Cement Colors on the Final Color of IPS Empress Ceramic Restorations

ABSTRACTIn this study, the effects of the color of different post-core materials and different colored cements on the color and esthetic of all-ceramic restorations were investigated.Three groups of post-cores (ceramic, Cr-Ni and Cr-Ni + opaque), one sample per each group, were prepared as discs 14 ± 0.05 mm in diameter and 1.5 ± 0.05 mm in thickness. A total of 40 cement samples, 10 per each group (opaque white, white, yellow and brown) were prepared as discs 14 ± 0.05 mm in diameter and 0.1±0.01 mm in thickness. Two samples of dental ceramics, 1 per each group (IPS Empress and IPS Empress 2), were prepared as discs in similar dimensions. The effect of different cement colors was evaluated on the final color of IPS Empress restorations.In each group, while one post-core material and one all-ceramic material remained constant, 10 cement specimens which prepared from four different cement colors were studied. Bovine dentin was placed instead of post-core material as a control sample and colorimetric measurements were made. The color configurations were assessed with a colorimeter for each group. In the evaluation of cement colors, for IPS Empress system, when only ceramic post-core material was used, white, yellow and brown cements were found to be clinically acceptable (ΔE<1).For IPS Empress 2 system, all colors for ceramic and Cr-Ni + opaque post-core were clinically acceptable but only opaque white cement for Cr-Ni post-core were found to be acceptable clinically (ΔE<2). When ceramic post-core material was used, white, yellow and brown cements were more appropriate clinically than opaque white cement.

Influence of different post core materials on the color of Empress 2 full ceramic crowns

For esthetic consideration, dentin color post core materials were normally used for all-ceramic crown restorations. However, in some cases, clinicians have to consider combining a full ceramic crown with a metal post core. Therefore, this experiment was conducted to test the esthetical possibility of applying cast metal post core in a full ceramic crown restoration. The color of full ceramic crowns on gold and Nickel-Chrome post cores was compared with the color of the same crowns on tooth colored post cores. Different try-in pastes were used to imitate the influence of a composite cementation on the color of different restorative combinations. The majority of patients could not detect any color difference less than DeltaE 1.8 between the two ceramic samples. So, DeltaE 1.8 was taken as the objective evaluative criterion for the evaluation of color matching and patients' satisfaction. When the Empress 2 crown was combined with the gold alloy post core, the color of the resulting material was similar to that of a glass fiber reinforced resin post core (DeltaE = 0.3). The gold alloy post core and the try-in paste did not show a perceptible color change in the full ceramic crowns, which indicated that the color of the crowns might not be susceptible to change between lab and clinic as well as during the process of composite cementation. Without an opaque covering the Ni-Cr post core would cause an unacceptable color effect on the crown (DeltaE = 2.0), but with opaque covering, the color effect became more clinically satisfactory (DeltaE = 1.8). It may be possible to apply a gold alloy post core in the Empress 2 full ceramic crown restoration when necessary. If a non-extractible Ni-Cr post core exists in the root canal, it might be possible to restore the tooth with an Empress 2 crown after covering the labial surface of the core with one layer of opaque resin cement.