Replica Technique Research Articles

Comparison of the marginal and internal fit of PMMA interim crowns printed with different layer thicknesses in 3D-printing technique.

The aim of this in vitro study was to compare the effect of printing layer thickness on the marginal and internal fit of interim crowns. A maxillary first molar model was prepared for ceramic restoration. Thirty-six crowns were printed with three different layer thicknesses using a digital light processing-based three-dimensional printer (25, 50, and 100 µm [LT 25, LT 50, and LT 100]). The marginal and internal gaps of the crowns were measured with replica technique. An analysis of variance was conducted to determine if there were significant differences between the groups (ɑ = .05). The marginal gap of LT 100 group was significantly higher than that LT 25 (p = .002) and LT 50 groups (p ≤ .001). The LT 25 group has significantly larger axial gaps than LT 50 group (p = .013); however, there were no statistically significant differences between other groups. The LT 50 group showed the smallest axio-occlusal gap. The mean occlusal gap differed significantly by printing layer thickness (p ≤ .001), with the largest gap occurring for LT 100. Provisional crowns printed with 50 µm layer thickness provided the best marginal and internal fit. It is recommended that provisional crowns be printed with a 50 µm layer thickness to ensure optimal marginal and internal fit.

Time-like entanglement entropy in AdS/BCFT

We study the entanglement entropy for time-like subsystem in two-dimensional boundary conformal field theory (BCFT) both from the field theory and holographic point of view. In field theory, we compute the time-like entanglement entropy of a pure time-like interval at zero and finite temperature using the replica technique and analytical continuation. We find that, similar to the ordinary space-like entanglement entropy in BCFT, the time-like entropy also has a bulk phase and a boundary phase which corresponds respectively to the dominance of the identity block in the bulk and boundary OPE channels. However, we find that in Lorentzian BCFT, the time-like entanglement entropy posses a third Regge phase which arises in the Regge limit of the interval, when one endpoint of the time interval approaches the light cone of the mirror image of the other endpoint. We determine the phase diagram for the time-like entanglement entropy. We find that while the time-like entropy is complex in the bulk phase and has a boundary term in the boundary phase, there is no boundary entropy in the Regge phase. Moreover, it can be real or complex depending on which side the Regge limit is approached from. On the gravity side, we obtain the holographic time-like entanglement entropy from the corresponding bulk dual geometries and find exact agreement with the field theory results. The time-like entanglement entropy may be useful to describe the entanglement of a quantum dot on a half line.

Impact of different CAD/CAM materials on internal and marginal adaptations and fracture resistance of endocrown restorations with: 3D finite element analysis

PurposeTo assess and compare the impact of various computers aided design/manufacturing (CAD/CAM) materials on internal and marginal discrepancies, fracture resistance and failure probability of Endocrown restorations with 3D Finite Element analysis.Material and methodsForty devitalized human maxillary first molars were collected. After endodontic treatment, they classified into 4 groups (n = 10) based on the materials used for endocrown fabrication. Group V (Vita-Enamic), Group N (Nacera Hybrid), Group T (Translucent Prettau Zirconia) and Group P (Pekkton ivory). All samples were exposed to artificial aging method simulating one year of clinical service. Silicone replica technique and stereomicroscope (25X) utilized to evaluate the marginal and internal gaps of endocrowns at different areas. Fracture resistance test used for cemented specimens followed by qualitative investigation utilizing Stereomicroscopy. Four models representing four endocrown systems used for restoration of severely-damaged endodontically treated upper first molar were generated for finite element analysis (FEA). Axially and centrally static occlusal compressive load was applied. Modified Von Mises and maximum principal stress values on the remaining tooth structure, cement lines and restorative materials were assessed independently. Resulted data were statistically analyzed at P-value ≤ 0.05.ResultsIn the current study, the highest mean values of internal and marginal discrepancies (μm) among studied groups were reported for Zirconia group (100.300 and 102.650) respectively, while the lowest mean value of internal discrepancy (μm) was observed for Nacera group (69.275) and the lowest mean value of marginal discrepancy (μm) was observed for PEKK group (78.4750). Regarding internal discrepancy, Vita-Enamic and PEKK groups did not exhibit any statistically significant differences (P = 0.293), however zirconia and the other tested groups exhibited statistically significant differences in the mean values of the marginal gap region (p 0.05).On the other hand, PEKK group showed the highest mean value of fracture resistance (1845.20 N) and the lowest value was observed for Vita-Enamic group (946.50 N). Regarding to stress distributions through 3D FEA, and according to modified von Mises (mvM) analysis, the greatest possible stress values were noticed in PEKK model in relation to tooth structure, cement line, and flowable composite as the following: (93.1, 64.5, 58.4 MPa) respectively, while Zirconia revealed lower maximum stress values (11.4, 13.6, 11.6 MPa) respectively.ConclusionsStatistically excellent marginal and internal fit was observed for PEKK in relation to other used endocrown materials. Also, PEKK material explained fracture resistance comparable to zirconia value while the lowest value was detected for Vita Enamic material.

Fit and fatigue behavior of CAD-CAM lithium disilicate crowns

Statement of problemNew computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate glass-ceramics have been marketed. However, information concerning their biomechanical behavior is lacking. PurposeThe purpose of this in vitro study was to compare the fit and fatigue behavior of two recently introduced CAD-CAM lithium disilicate materials with the standard IPS e.max CAD ceramic and to investigate the effect of the thermal treatment for crystallization on crown fit. Material and methodsMonolithic crowns (n=15) were milled from 3 CAD-CAM lithium disilicates: IPS e.max CAD (Ivoclar AG), Rosetta SM (Hass), and T-lithium (Shenzhen Upcera Dental Technology). Marginal and internal fit were evaluated using the replica technique before and after crystallization, and the fatigue behavior of the luted crowns was evaluated by the step-stress method. One-way ANOVA and the Tukey test were used to compare fit among the materials. Fatigue failure load was evaluated by the Kaplan-Meier and Mantel-Cox tests. The effect of crystallization on fit was evaluated with the paired t test (α=.05). ResultsMarginal fit was different between IPS e.max CAD (74 μm) and Rosetta SM (63 μm) (P=.02). T-lithium was similar to the other ceramics (68 μm) (P>.05). Occlusal internal space was similar among all materials (P=.69). Fatigue failure loads of Rosetta SM (1160 N) and T-lithium (1063 N) were similar to IPS e.max CAD (1082 N) (P>.05). The fatigue failure load of Rosetta SM was higher than that of T-lithium (P=.04). Crystallization reduced the axial internal space of all materials (P<.05) without significantly affecting marginal fit (P>.05). ConclusionsThe fit and fatigue behavior of Rosetta SM and T-lithium were similar to that of IPS e.max CAD. Crystallization reduced the internal space of the crowns.

Evaluation of Internal Adaptation and Marginal Fit of Onlays Fabricated Using Computer-Aided Design (CAD)-Computer-Aided Manufacturing (CAM) and Three-Dimensional Printing Techniques: An In Vitro Study.

Background This in-vitro study aimed to evaluate the internal adaptation, marginal fit, and applicability of digital intraoral impression techniques for onlays fabricated using computer-aided design (CAD)-computer-aided manufacturing (CAM) and three-dimensional (3D) printing techniques using a stereomicroscope and micro-CT scan. Methodology A total of 20 extracted mandibular first molars were selected for this study. The teeth were then divided into two groups. Onlay cavities were prepared involving the mesiobuccal cusp of the mandibular first molar in both groups. After preparation, both blocks were sent to the laboratory for fabrication of onlays using digital impressions (Shinning 3D scanner). Once the onlays were fabricated using CAD-CAM and 3D printing, a replica technique with monophase medium body impression material was used to assess the marginal fit and internal adaptation. The accuracy of internal adaptation was evaluated and compared using a stereomicroscope at 20× magnification. Measurements were taken at proximal margins, the inner axial wall, and the occlusal cavosurface area according to the Molin and Karlsson criteria. The same samples of both groups were studied for marginal fit using a micro-CT scan and values were recorded. The data collected were statistically analyzed using an independent Student's t-test. Results Independent Student's t-test results demonstrated that the mean thickness values of the material in the CAD-CAM group at occlusal cavosurface area, proximal area, and axial area were significantly higher when compared to the 3D printing group at p <0.001 and 0.005, respectively. Conclusions Internal adaptation and marginal fit of 3D-printed onlays were significantly lower than CAD-CAM onlays whereas the accuracy of 3D-printed onlays was significantly better than CAD-CAM onlays.

Marginal and internal discrepancies associated with carbon digital light synthesis additively manufactured interim crowns

Statement of problemThe carbon digital light synthesis (DLS) or continuous liquid interface production (CLIP) technology is an innovative additive manufacturing technology using oxygen-inhibited photopolymerization to create a continuous liquid interface of unpolymerized resin between the growing component and the exposure window. This interface eliminates the need for an incremental layer-by-layer approach, allowing for continuous creation and increased printing speed. However, the internal and marginal discrepancies associated with this new technology remain unclear. PurposeThe purpose of this in vitro study was to evaluate the marginal and internal discrepancies by using the silicone replica technique of interim crowns fabricated by 3 different manufacturing technologies: direct light processing (DLP), DLS, and milling. Material and methodsA mandibular first molar was prepared, and a crown was designed with a computer-aided design (CAD) software program. The standard tessellation language (STL) file was used to create 30 crowns from the DLP, DLS, milling technologies (n=10). The gap discrepancy was determined using the silicone replica approach, with 50 measurements made with a ×70 microscope for each specimen for the marginal and internal gaps. The data were analyzed using 1-way ANOVA, followed by the Tukey HSD post hoc test (α=.05). ResultsThe DLS group had the least marginal discrepancy compared with the DLP and milling groups (P<.001). The DLP group showed the highest internal discrepancy followed by the DLS and milling groups (P=.038). No significant difference was found between DLS and milling in terms of internal discrepancy (P>.05). ConclusionsThe manufacturing technique had a significant effect on both internal and marginal discrepancies. The DLS technology showed the smallest marginal discrepancies.

Synthesis and characterization of a novel multifunctional magnetic bioceramic nanocomposite

An emerging approach in tissue engineering, especially in cases where large bone cavities remain unfilled after tumor removal, is the implementation of bioceramic scaffolds with magnetic properties for bone augmentation. The fabrication of bioactive porous scaffolds with adequate mechanical characteristics and sufficient porosity represents to assist bone regeneration. one of the most important difficulties in tissue engineering. The final goal is, the in situ apatite formation, a synergistic result of bioceramics, and stem cell activation/differentiation to promote bone regeneration via magnetically driven osteogenic lineage. This study focuses on the development of a novel multifunctional three-dimensional scaffold with certain physicochemical and biological features, addressing diverse difficult issues, such as bioactivity and biocompatibility, as well as bone tissue malignancies. The synthetic approach initiates with the synthesis of CoFe2O4 nanoparticles (NP), followed by the fabrication of Mg2SiO4–CoFe2O4 nanocomposite (NC), employing a two-pot sol-gel synthesis method. Finally, three-dimensional scaffolds (MS) are fabricated via the polymer foam replica technique. X-Ray Diffraction, Thermogravimetry, and Fourier transform infrared spectroscopy, reveal the occurrence of the constituent materials (forsterite: Mg2SiO4 and cobalt iron oxide). Static magnetic characterization at each fabrication stage outlines the collective magnetic features while magnetic particle hyperthermia highlights the heating efficiency quantified as specific loss power (SLP) and specific absorption rate (SAR) in W·g−1 (NP: 19 - 43 °C in 100 s, SLP = 450 W g−1, NC: SLP = 200 W g−1, SAR= 1,07 W g−1). This opens promising pathways in bone tissue regeneration cancer treatments combined with targeted delivery of active/pharmaceutical substances and magnetic hyperthermia.

Effect of cement space settings on the marginal and internal fit of 3D-printed definitive resin crowns

Statement of problemThe cement gap setting affects the marginal and internal fits depending on the crown material and manufacturing method (subtractive or additive manufacturing). However, information on the effects of cement space settings in the computer-aided design (CAD) software program, which is used to aid the manufacturing with 3-dimensional (3D) printing-type resin material, is lacking, and recommendations for optimal marginal and internal fit are needed. PurposeThe purpose of this in vitro study was to evaluate how cement gap settings affect the marginal and internal fit of a 3D-printed definitive resin crown. Material and methodsAfter scanning a prepared typodont left maxillary first molar, a crown was designed with cement spaces of 35, 50, 70, and 100 μm by using a CAD software program. A total of 14 specimens per group were 3D printed from definitive 3D-printing resin. By using the replica technique, the intaglio surface of the crown was duplicated, and the duplicated specimen was sectioned in the buccolingual and mesiodistal directions. Statistical analyses were performed using the Kruskal–Wallis and the Mann–Whitney post hoc tests (α=.05). ResultsAlthough the median values of the marginal gaps were within the clinically acceptable limit (<120 μm) for all the groups, the smallest marginal gaps were obtained with the 70-μm setting. For the axial gaps, there was no observed difference in the 35-, 50-, and 70-μm groups, and the 100-μm group showed the largest gap. The smallest axio-occlusal and occlusal gaps were obtained with the 70-μm setting. ConclusionsBased on the findings of this in vitro study, a 70-μm cement gap setting is recommended for optimal marginal and internal fit of 3D-printed resin crowns.

Amount of Residual Cement at the Margin of Implant-Supported Crowns Cemented Using the Polytetrafluoroethylene Tape, Replica Technique, and Conventional Cementation Technique

Background: This study compared the amount of residual cement at the margin of implant-supported crowns cemented using the polytetrafluoroethylene (PTFE) tape, replica technique, and conventional cementation technique. Methods: In this in vitro experimental study, a mandibular model underwent full-arch scanning. The right first molar tooth was eliminated on the scan using Exocad software, and a regular implant analog was modelled using the Exocad model creator. The designed abutment was then printed. The implant analog was fixed in place with acrylic resin and scanned using a scan body. A full-zirconia custom abutment was then designed by Exocad. Abutments were fabricated using zirconia and sintered. Twenty-seven resin crowns were fabricated for the abutments, and their fit was assessed. Nine crowns were conventionally cemented by filling half of the crown space with cement, 9 crowns were cemented using PTFE tape, and the remaining 9 were first placed on a resin replica and then cemented on the abutments. The residual cement was weighed using a digital scale, and the groups were compared by one-way ANOVA and LSD test (α=0.05). Results: The amount of residual cement was significantly different among the three groups, indicating that the amount of residual cement was the highest in conventional cementation, and the lowest in the replica group (P &lt; 0.05). Pairwise comparisons showed significant differences between all groups (P &lt; 0.05). Conclusions: The replica technique followed by the PTFE tape resulted in the minimum amount of residual cement at the margin of implant-supported cement-retained crowns and are preferred for use in the clinical setting.

Study on the fabrication and performance of 3D-Network SiC/Cu composites

ABSTRACT 3D-Network SiC ceramic was prepared using a polymer sponge replica technique with SiC ceramic slurry (77 wt% solid content). The triangular hole defects in 3D-Network SiC ceramic were reduced and the mechanical properties were improved by high-pressure spraying and vacuum infiltration. The 3D-Network SiC/Cu composite material was fabricated by the gravity casting technique, and the interfacial bonding and abrasion resistance of the composites were tested and analyzed. The results show that the compressive strength of high-pressure sprayed 3D-Network SiC ceramic increased slightly from 0.67 Mpa to 0.74 Mpa due to the triangular hole defects left when the polymer sponge was decomposed at high temperatures. The mechanical properties of 3D-Network SiC ceramics that have been vacuum infiltrated in alumina and a mixture composed of alumina and andalusite were greatly improved, and their compressive strength was increased to 1.02Mpa and 1.57Mpa, respectively. The interface between SiC and Cu in the 3D-Network SiC/Cu composites prepared by different processes shows excellent bonding, and the abrasion resistance of the 3D-Network SiC/Cu composites prepared by different processes was 2.02–9.18 times that of pure copper respectively.

Influence of Direct and Indirect Digital Data Capturing Techniques on Marginal Accuracy and Internal Fit of CAD/CAM Fabricated PEEK and Zirconia Crowns

Purpose: The aim of this study was to evaluate the marginal and internal fitness of PEEK and Zirconia crowns fabricated by three different impression techniques. Materials and methods: Thirty standardized acrylic die models were prepared. Dies were divided into two main groups (n= 15): Group 1: CAD/CAM fabricated zirconia crowns. Group 2: CAD/CAM fabricated PEEK crowns. Each group was subdivided into three subgroups (n= 5), according to the impression technique using for data acquisition: Sub-group (A): direct digital scans of the model used intraoral digital scanner. Sub-group (B): indirect digital scans of the silicon impressions using extraoral scanner. Sub-group (C): indirect digital scans of the stone casts obtained from silicon impressions using extraoral scanner. Crowns were then designed and fabricated. Marginal and internal gaps were measured using silicone replica technique and field digital microscope. Results: Independent t-test was used for comparison between groups. Comparisons between subgroups were performed by one-way analysis of variance (ANOVA) test, followed by Bonferroni’s post hoc test. In Zirconia group, the highest mean value was recorded in stone cast scan group, followed by intraoral scan, with the least value recorded in impression scan subgroup. In PEEK group, the highest mean value was recorded in stone cast group, followed by impression scan, with the least value recorded in intraoral scan subgroup. Conclusions: All tested crowns showed marginal gap distance values within the clinically acceptable levels. PEEK crowns had lower vertical marginal gap distance than zirconia crowns with different scanning techniques.

Influence of Direct and Indirect Digital Data Capturing Techniques on Marginal Accuracy and Internal Fit of CAD/CAM Fabricated PEEK and Zirconia Crowns

Purpose: The aim of this study was to evaluate the marginal and internal fitness of PEEK and Zirconia crowns fabricated by three different impression techniques. Materials and methods: Thirty standardized acrylic die models were prepared. Dies were divided into two main groups (n= 15): Group 1: CAD/CAM fabricated zirconia crowns. Group 2: CAD/CAM fabricated PEEK crowns. Each group was subdivided into three subgroups (n= 5), according to the impression technique using for data acquisition: Sub-group (A): direct digital scans of the model used intraoral digital scanner. Sub-group (B): indirect digital scans of the silicon impressions using extraoral scanner. Sub-group (C): indirect digital scans of the stone casts obtained from silicon impressions using extraoral scanner. Crowns were then designed and fabricated. Marginal and internal gaps were measured using silicone replica technique and field digital microscope. Results: Independent t-test was used for comparison between groups. Comparisons between subgroups were performed by one-way analysis of variance (ANOVA) test, followed by Bonferroni’s post hoc test. In Zirconia group, the highest mean value was recorded in stone cast scan group, followed by intraoral scan, with the least value recorded in impression scan subgroup. In PEEK group, the highest mean value was recorded in stone cast group, followed by impression scan, with the least value recorded in intraoral scan subgroup. Conclusions: All tested crowns showed marginal gap distance values within the clinically acceptable levels. PEEK crowns had lower vertical marginal gap distance than zirconia crowns with different scanning techniques.

The effect of preparation design on the fracture resistance and adaptation of the CEREC ceramic endocrowns.

The purpose of this experimental in vitro study was to assess the effect of having one or two intact axial walls on the improvement of the fracture resistance, and marginal and internal adaptation of computer-aided design/computer-aided manufacturer fabricated ceramic endocrowns. Thirty-six endodontically treated mandibular molars were divided into three groups (n = 12). Group A, represented teeth that all of their axial walls were reduced till they all had 3 mm height. In group B, the buccal wall had 5 mm height and the others were reduced to 3 mm. Specimens of the group C had 5-mm-height buccal and one 5 mm-height proximal wall, with all other walls of 3 mm height. All teeth were scanned using intraoral scanner, and endocrowns were milled from zirconia lithium silicate ceramics blocks. The marginal and internal discrepancy of restorations were evaluated with the replica technique. Fracture resistance was also measured after cementation and modes of failure were observed. One-way analysis of variance and Tukey HSD multiple comparisons were used to analyze the data (α = .5). Significant differences were observed within the groups in terms of the axial discrepancy (p = .022); group A had significantly higher amounts of axial discrepancy compared to group B (p = .001) and group C (p = .003). Preservation of the intact axial walls did not result in a statistically significant decrease in marginal (p = .21) and pulpal (p = .31) discrepancy values. Also, concerning the fracture resistance no significant difference was observed among the groups (p = .51). Preservation of at least one of the axial walls could reduce the amount of the axial discrepancy and, therefore, improves the adaptation of the restoration. However, based on this study, it did not improve fracture resistance.

Effect of a new support design on the marginal and internal gap of additively manufactured interim crowns using direct light deposition technology.

To investigate the design and location of supporting structures on the marginal and internal gap of interim restorations. A mandibular right first molar resin tooth was prepared for a full coverage crown and scanned using a laboratory scanner (3Shape D900). The scanned data were converted into standard tessellation language (STL) format and an indirect prosthesis was designed using computer-aided design (CAD) software (exocad DentalCAD). The STL file was used to fabricate a total of 60 crowns with a 3D printer (EnvisionTEC Vida HD). The crowns were printed using E-Dent C&B MH resin and divided into 4 groups based on four different support structure designs, including supports on the occlusal (0° group), buccal and occlusal (45° group), buccal (90° group), and a new design consisting of horizontal bars placed on all surfaces and line angles (Bar) (n=15). The silicone replica technique was used to determine the gap discrepancy. Fifty measurements were obtained for each specimen to examine the marginal and internal gaps by using a digital microscope (Olympus SZX16) at ×70 magnification. Additionally, the marginal discrepancy at different locations of the tested crowns, including buccal (B), lingual (L), mesial (M), and distal (D), as well as the maximum and minimum marginal gap intervals among groups, were analyzed. The collected data were analyzed using factorial ANOVA, followed by the Tukey HSD test for multiple comparisons (a=0.05). There was a significant difference in marginal and internal gaps among the groups (p<0.001). The buccal placement supports (90° group) had the least marginal and internal discrepancies (p<0.001). The new design group showed the highest marginal and internal gap. The marginal discrepancy in different locations of the tested crowns (B, L, M, D) was found to be significantly different among the groups (p<0.001). The mesial margin of the Bar group had the largest marginal gap, whereas the buccal margin of the 90° group had the lowest marginal gap. The new design had a significantly smaller difference between the maximum and minimum marginal gap intervals than other groups (p<0.001). The location and design of the supporting structures affected the marginal and internal gaps of an interim crown. The buccal placement of supporting bars (90° printing orientation) showed the smallest mean internal and marginal discrepancies.

In-Vitro Investigation of Marginal Adaptation and Fracture Resistance of Resin Matrix Ceramic Endo-Crown Restorations

The aim of this study was to evaluate the fracture resistance and marginal adaptation of endo-crown restorations produced from different resin-matrix ceramics (RMS) and the effects of these materials on marginal adaptation and fracture resistance. Three frasaco models were used by preparing (first) premolar teeth in three different margin preparations: butt-joint, heavy chamfer and shoulder. Each group was further divided into four subgroups according to the type of restorative material used: Ambarino High Class (AHC), Voco Grandio (VG), Brilliant Crios (BC) and Shofu (S) (n = 30). Master models were obtained using an extraoral scanner and fabricated with a milling machine. Marginal gap evaluation was performed with a silicon replica technique using a stereomicroscope. Replicas of the models (n = 120) were produced with epoxy resin. The fracture resistance of the restorations was recorded using a universal testing machine. The data were statistically analyzed using two-way ANOVA, and a t-test was applied for each group. Tukey's post-hoc test was performed to compare significant differences (p ≤ 0.05). The highest marginal gap was observed in VG, and the best marginal adaptation and the highest fracture resistance were found in BC. The lowest fracture resistance in Butt-joint preparation design was found in S. In addition, the lowest fracture resistance value in the heavy chamfer preparation design was found in AHC. The heavy shoulder preparation design displayed the highest fracture resistance values for all materials.

Composite PLGA–Nanobioceramic Coating on Moxifloxacin-Loaded Akermanite 3D Porous Scaffolds for Bone Tissue Regeneration

Silica-based ceramics doped with calcium and magnesium have been proposed as suitable materials for scaffold fabrication. Akermanite (Ca2MgSi2O7) has attracted interest for bone regeneration due to its controllable biodegradation rate, improved mechanical properties, and high apatite-forming ability. Despite the profound advantages, ceramic scaffolds provide weak fracture resistance. The use of synthetic biopolymers such as poly(lactic-co-glycolic acid) (PLGA) as coating materials improves the mechanical performance of ceramic scaffolds and tailors their degradation rate. Moxifloxacin (MOX) is an antibiotic with antimicrobial activity against numerous aerobic and anaerobic bacteria. In this study, silica-based nanoparticles (NPs) enriched with calcium and magnesium, as well as copper and strontium ions that induce angiogenesis and osteogenesis, respectively, were incorporated into the PLGA coating. The aim was to produce composite akermanite/PLGA/NPs/MOX-loaded scaffolds through the foam replica technique combined with the sol-gel method to improve the overall effectiveness towards bone regeneration. The structural and physicochemical characterizations were evaluated. Their mechanical properties, apatite forming ability, degradation, pharmacokinetics, and hemocompatibility were also investigated. The addition of NPs improved the compressive strength, hemocompatibility, and in vitro degradation of the composite scaffolds, resulting in them keeping a 3D porous structure and a more prolonged release profile of MOX that makes them promising for bone regeneration applications.

Reflected entropy for communicating black holes. Part I. Karch-Randall braneworlds

We obtain the reflected entropy for bipartite mixed state configurations of two adjacent and disjoint intervals at a finite temperature in BCFT2s with two distinct boundaries through a replica technique in the large central charge limit. Subsequently these field theory results are reproduced from bulk computations involving the entanglement wedge cross section in the dual BTZ black hole geometry truncated by two Karch-Randall branes. Our result confirms the holographic duality between the reflected entropy and the bulk entanglement wedge cross section in the context of the AdS3/BCFT2 scenario. We further investigate the critical issue of the holographic Markov gap between the reflected entropy and the mutual information for these configurations from the bulk braneworld geometry and study its variation with subsystem sizes and time.

Evaluation of the Marginal Fit of Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) Zirconia Bridges Fabricated With Different Firing Cycles of Veneering Porcelain: An In Vitro Study.

Introduction Zirconia provides adequate mechanical strength to be used as a framework for all ceramic prostheses. Such prostheses must be covered with suitable porcelain to obtain good aesthetic results. The aim To study the effect of the firing cycle numbers of veneering ceramics (one cycle, two cycles, and three cycles) on the marginal fit of computer-aided design(CAD) and computer-aided manufacturing (CAM)zirconia bridges. Materials and methods The sample consisted of 30 full ceramic zirconia bridges, designed by CAD/CAM on a metal bridge model that was designed for this purpose. The sample was divided into three groups (N = 10); group Aunderwent a single firing cycle, group Bunderwent two cycles, and group Cunderwent three cycles. The copper model of the bridge was prepared to be a three-unit bridge, and the impressions of the metal models were taken to make zirconia cores. After that, the veneering ceramic layer and the micro-marginal gap were measured (in microns) on both the buccal and lingual surfaces of each bridge in the sample using the replica technique. A one-way ANOVA test was used to detect statistically significant differences between the groups. Results There were no significant differences between the studied groups in binary comparison; however, the arithmetic mean values of the marginal gap in group C were greater than all the studied groups. Conclusion Within the limitations of the current work, we found that increasing the number of firing cycles of zirconia cores affects the marginal fit; thus, it is recommended to follow the two firing cycle protocol for better adaptation of the CAD/CAM zirconia bridges.

Clinical evaluation of marginal fit of uncemented CAD-CAM monolithic zirconia three-unit restorations in anterior areas, using scannable and conventional polyvinyl siloxane impression materials

BackgroundThe accuracy of impression techniques determines the marginal fit of fixed prostheses. Marginal accuracy plays a main role in the success and failure of treatments. This in-vivo study evaluated the marginal fit of anterior three-unit monolithic zirconia fixed partial dentures (FPDs) using conventional and scannable polyvinyl siloxane impression materials.MethodsTen patients were selected to replace the lateral teeth with a three-unit monolithic zirconia bridge. For each patient, in the first group, an impression was made with a two-step putty-wash technique using scannable polyvinyl siloxane material (BONASCAN; DMP, Greece). In the identical session, as the second group, an impression of conventional putty-wash polyvinyl siloxane was taken (BONASIL A+ Putty; DMP, Greece). The marginal discrepancy was measured through the replicas, which were cut perpendicularly within the buccolingual and mesiodistal directions. An Independent t-test was employed for data analyses (P < 0.05).ResultsThe marginal discrepancy in a conventional method for central abutment in mid-buccal, mid-lingual, mid-mesial, and mid-distal was higher than in the scannable method but it was not significant (P > 0.05). Also, the marginal discrepancy for canine abutment in the conventional method was higher than in the scannable method, but it was not significant, either (P > 0.05).ConclusionsFPDs fabricated from both scannable and conventional impression materials were not superior to each other in marginal fit for both central and canine abutments by evaluation using the replica technique.

Influence of ceramic Kelvin Cell's strut shape on mechanical properties

The replica technique is one of the most established manufacturing methods of highly porous scaffolds for bone tissue engineering. Despite a multitude of possible templates, this method is limited in terms of reproducibility and periodicity. We overcome this issue by 3D-printing of designed periodic polymer templates with varying strut shape and thickness which we further process with the replica technique to obtain cellular ceramics with adjustable micro- and macrostructure. The periodic structure (Kelvin cells) was created using computer-aided design (CAD) software. These 3D rigid polymer structures were coated with alumina slurry and transformed to ceramic structures. This combination of polymer 3D-printing and the replica technique enables the application-specific production of cellular structures in a flexible and cost-effective process.