Post Space Research Articles

Effect of different intraoral scanners on the trueness of custom post space scans with two different cervical diameters

Effect of different intraoral scanners on the trueness of custom post space scans with two different cervical diameters

Effect of Photodynamic Therapy with Four Light-Sensitive Materials on the Bond Strength of Fiber Posts to Root Dentin.

Introduction: Fiber-reinforced composite posts (FRCP) have become popular due to their multiple advantages in teeth with extensive crown destruction. Proper disinfection is essential for the successful bonding of these posts. Commonly used solutions for cleaning and disinfecting the root canals adversely affect the bond strength (BS). Photodynamic therapy is an alternative method for irrigating the root canal and disinfecting the post space.This study was designed to evaluate the impact of photodynamic therapy on the BS of fiber posts to root canal dentin. Methods: Human maxillary canines were recruited for this study. The tooth crowns were removed at the cervical line and endodontically treated. After fiber post spaces were prepared, the teeth were assigned to five groups based on the light-sensitive material: deionized water, indocyanine green and 810-nm laser, methylene blue and 660-nm laser, toluidine blue and 635-nm laser, curcumin and LED. The posts were cemented after photodynamic therapy. Cervical, middle, and apical samples were prepared by transverse sectioning. Push-out bond strength (PBS) values were measured in a universal testing machine. Finally, the data underwent statistical analyses with ANOVA and Howell-Games tests. Results: One-way ANOVA revealed no significant differences between the groups (P<0.001). The Games-Howell test showed that curcumin (7.23±3.75) and the control group (5.92±4.04) had a similar BS (P>0.005). The BS was lower in the methylene blue (3.34±2.15), indocyanine green (2.59±3.16), and toluidine blue (2.45±1.73) groups than in the control group (P<0.005). Conclusion: Unlike other light-sensitive materials, curcumin did not adversely affect the BS.

“Comparative Evaluation of Fracture Resistance of Custom Cast Post and Core, Pre-Fabricated Post and Core and CAD/CAM Fabricated Post and Core: An In-Vitro Study”

The aim of the study was to compare and evaluate fracture resistance of Custom Cast post and core, Pre-fabricated post and core and CAD/CAM fabricated post and core. Material and Methods: 60 transparent endoblocks with single root canal that simulated natural teeth were randomly divided into 3 groups of 20 endoblocks each. The working length of the root canal in the transparent endobloc was determined. The canals were prepared with K-file sizes 10,15 and 20 followed by Protaper Ni-Ti files (sizes S1, S2, F1 and F2); Dentsply by using the crown down technique to the full working length. Gutta percha was removed from the root canals with Peeso drills to a depth of 12 and post spaces were prepared in all groups with the special preparation drills of each system leaving 5mm of gutta percha in all specimens. For group 1, after root canal treatment of 20 samples, Prefabricated plastic burnout posts were coated with pattern resin and then inserted into the canal with slight pressure to take the canal impression which was further send for casting followed by using GC gold label glass ionomer resin for luting. For group 2, the Prefabricated EDELWEISS post and core were placed into the canal and the cement was allowed to set. For group 3 impression of the canal was made using pattern resin. The burnout post was scanned with a lab scanner and designing was done using the designing software. CAD-CAM fabricated post and core was placed into the canal and luted with the help of glass ionomer cement. Composite core fabrication was done and the specimens were secured in a universal load-testing machine at an angle of 1300 to the long axis of the tooth. Until fracture occurred, a compressive force was applied at a crosshead speed of 1 mm/min. The fracture loads were determined. Mean failure load for each group was recorded in N. Results: The mean fracture load of Group 1, was found to the maximum followed by Group 3 &amp; Group 2 samples, in decreasing order. Conclusion: The mean ......

Competing Global South and Global North knowledge sets contending for dominance in the post Covid-19 Higher Education space

This article introduces this JIS Special Issue which focusses on competing Global South and Global North knowledge sets contending for dominance in the post Covid-19 Higher Education space and asks the question if GS-GN discourses and practices are expanding hegemonies or generating authentic reciprocity?&#x0D;

Evaluation of Sealer Remnants Using a Bioceramic Sealer Single-cone Technique after Post Space Preparation and its Influence on the Adhesion of Fibre Posts in vitro.

To compare calcium silicate-based endodontic sealer and epoxy resin-based sealer remnants on root canal walls after post space preparation and their influence on the bond strength of fibre posts fixed with a dual-cured resin cement. Thirty-six extracted single-root mandibular premolars were instrumented and divided randomly into two equal groups with different endodontic sealers. iRoot SP (Innovative BioCeramix, Vancouver, Canada) was employed in the experimental group and AH Plus (Dentsply Sirona, Charlotte, NC, USA) was used in the control group. Sealer remnants were observed under an endodontic microscope after root canal therapy and post space preparation. Fibre posts were fixed with dual-cured resin cement. Specimens were taken at each third of the post space. The push-out bond strength was measured using a universal testing machine and fracture modes were assessed. Statistical analysis was performed using an independent samples t test and one-way analysis of variance. There was no statistically significant difference in bond strength of fibre posts between the control and experimental group (P > 0.05); however, sealer remnants were observed in 38.9% of the samples treated with iRoot SP and none of the samples treated with AH Plus. The major fracture mode in samples treated with iRoot SP was adhesive failure between the resin cement and the post, and no adhesive failure between the resin cement and dentine occurred at the site of the sealer remnant. The presence of iRoot SP remnants on the root canal walls after post space preparation did not interfere with bonding. iRoot SP is a viable option for root canal obturation before fibre post cementation.

Fundamental Study of Spacer‐Insulation‐Performance Improvement by Nonlinear‐Resistance Material

Coating the surface of insulators used in a gas‐insulated switchgear (GIS) with nonlinear‐resistance material is expected to increase breakdown voltage by reducing the electric‐field concentration when metal particles adhere to the insulators. In this study, an epoxy resin with zinc oxide was used as a nonlinear‐resistance material. Tensile strength, adhesion by heat cycle test, hardness, and resistance to decomposition products of sulfur hexafluoride gas were evaluated for the nonlinear‐resistance material. It was confirmed that there were no problems with mechanical properties for application to GIS. The nonlinear‐resistance material was spray‐coated on actual post spacers, and the breakdown voltage was evaluated when metallic particles adhered to the post spacers. When the coating thickness was 20–35 μm, the breakdown voltage increased by about 8%. When the coating thickness was 50– 68 μm, however, the breakdown voltage increased by 23%, confirming that the breakdown voltage of an actual spacer improved. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Fracture resistance of endodontically treated teeth, restored with two post-core systems in different post space diameters (in vitro study)

BackgroundFracture resistance of post-core restoration depends on the design of the post, post diameter, post length, the type of adhesive cement used along with material of the core. Despite the different studies concerning the effect of post space diameter on the fracture resistance of endodontically treated teeth, more information regarding fracture resistance and the effect of different post space systems/materials and diameters is required.Aim of the studyThis study aimed to evaluate fracture resistance of endodontically treated teeth, restored with two post-core systems in different post space diameters.Materials and methodsTwenty freshly extracted maxillary central incisors were collected for this study. They were randomly divided into four groups according to intracanal post and its diameter. Group GN (glass-fiber post of 10-mm length and 1.3-mm diameter with composite core), group GW (glass-fiber post of 10-mm length and 1.75-mm diameter with composite core), group ZN (custom-made zirconia one-piece post-core of 10-mm length and 1.3-mm diameter) and group ZW(custom-made zirconia one-piece post-core of 10-mm length and 1.75-mm diameter).Fracture resistance for all samples was evaluated using the universal testing machine under a static load. The data was collected and statistically analyzed using One-Way ANOVA test. Modes of failure were assessed using stereomicroscope for each group.ResultsThe highest mean fracture resistance was recorded in group GW (638.7 ± 285.1 N), followed by group ZW (598.5 ± 127.6 N), then GN group (442.8 ± 65.38 N). The lowest mean fracture resistance was recorded in group ZN (435.3 ± 117.3 N). One-Way ANOVA test revealed that there was no statistically significant difference in fracture resistance values among the groups.ConclusionPost space diameter had an impact over the fracture resistance of endodontically treated teeth. Modulus of elasticity of post material had a major effect on the fracture resistance and mode of failure along with the restorability of the restored tooth. However, there was no statistically significant difference among the tested groups.

An Evaluation of the Fracture Resistance of Endodontically Treated Teeth Restored With Two Types of Posts (Diamond Posts and Fiber Posts): An In Vitro Study.

The aim of this study is to compare the fracture resistance and the mode of failure of endodontically treated permanent mandibular premolars restored with two types of posts: diamond posts and glass-fiber posts. Fortyhuman mandibular premolars indicated for orthodontic extraction were collected for this studyand were similar in shape, size, and length. The teeth were sectioned horizontally, 1 mm above the cementoenamel junction.Root canal treatment was carried out on all specimens, and obturation was done by lateral condensation. The teeth were randomly divided into two groups. The post space was prepared in the first group to receive the diamond posts and in the second group to receive the fiber posts. A dual-cure resin material was used for cementing the posts and building up the cores. Then, they were subjected to a compressive load at a cross-head speed of 1 mm per minute and at an angle of 135 degrees to the long axis of the tooth until a fracture occurred using a universal testing machine. Fracture resistance and the mode of failure were assessed. The fracture above the acrylic block level was considered favorable, and the fracture below the acrylic block level was considered unfavorable. The data were analyzed statistically. The statistical analysis of fracture resistance between the two groups was carried out with a t-test. The statistical analysis for the failure mode of the teeth was carried out with a chi-square test. There was a statistically significant difference showing that the diamond posts had better fracture resistance when compared with glass-fiber posts, while there was no statistically significant difference in terms of the failure mode between the two posts. Within the limitations of this study, it can be concluded that diamond posts showed higher fracture resistance than glass-fiber posts. Glass-fiber posts showed more favorable failure modes but were statistically insignificant compared to diamond posts.

Effects of glass fibers reinforced and non-reinforced composite resin on fracture behavior of severely destructed primary incisors and restored with post and core system

ObjectiveTo evaluate fracture resistance and failure type of coronally rehabilitated primary incisors with EverX Flow or Grandio Core post and core with or without fiber post. Materials and MethodsForty-eight extracted maxillary primary incisors were root canal treated and obturated with Metapex. The coronal 4-mm of Metapex was removed to create 3-mm intracanal post space. Next, coronal enamel and radicular dentin surfaces were acid-etched, and a bonding agent was applied and light-cured. Based on intracanal post and 2-mm height core buildup materials, specimens were divided equally (n = 12) into 4 groups as follow; Group I (EverX Flow), Group II (Grandio Core), Group III (Fiber post, and EverX Flow), and Group IV(Fiber post and Grandio Core). The coronal restorations were finalized to 4-mm height using G-aenial Anterior composite and specimens were tested for fracture resistance. Force required to induce fracture was recorded and failure type was examined. ResultsFracture resistance of Fiber post and EverX Flow group was statistically significant high than other tested groups. However, fracture resistance of EverX Flow group showed non-statistically significant difference from that of Fiber post and Grandio Core group. Regarding failure type, no specimen presented root fracture, and all failures were favorable and repairable. ConclusionEverX flow post and core with or without fiber post enhanced fracture resistance of restored primary incisors compared to Grandio Core alone. Clinical relevanceEverX flow post and core system with or without fiber post could be a promising restorative option for severely destructed primary incisors.

Evaluation of the Effects of Different Types of Resin Cement Systems on the Push-Out Bond Strength of the Fiber Post to Intracanal Dentin in Anterior Primary Teeth.

This study aimed to evaluate the effects of using three different resin cements on push-out bond strength (PBS) of fiber posts to root canal dentin of primary teeth. Fifty primary canines were randomly divided into five experimental groups according to the type of the luting agent used for fiber post cementation after endodontic treatment and post space preparation as the following: Group 1: glass ionomer cement (GIC), Group 2: flowable resin composite, Group 3: etch and rinse (E&R) resin cement, Group 4: self-etch (SE) resin cement, Group 5: self-adhesive (SA) resin cement. The PBS values of the cemented fiber posts to root canals were measured. The data were statistically analyzed using a one-way analysis of variance, followed by Tukey's post hoc test. The highest mean PBS value was observed in Group 4 (SE resin cement), followed by Group 3 (E&R resin cement), and the lowest PBS value belonged to Group 1 (GIC), followed by Group 5 (p-values < 0.05). The mean PBS of Group 3 (E&R resin cement) was significantly higher than those of Groups 1 (GIC), 2 (flowable resin composite), and 5 (SA resin cement) (p-values < 0.05). However, no significant difference was found between the mean PBS of GIC and SA resin cement (p-value >0/05). Using SE resin cement for fiber post cementation in primary anterior teeth showed the best results, followed by E&R resin cement. The lowest PBS was observed for GIC, followed by SA resin cement.

Evaluation of the accuracy of direct intraoral scanner impressions for digital post and core in various post lengths: An in-vitro study.

Despite the growing utilization of direct intraoral scanners (IOSs) in dentistry, there is a scarcity of research investigating their accuracy, specifically in post and core. Few studies have conducted comprehensive three-dimensional assessments and comparisons of IOSs with the conventional impression technique, particularly in different post space lengths. The purpose of this in vitro study was to digitally assess the accuracy of direct intraoral scanner (IOS) impressions for different post space lengths, specifically 6, 8, and 10 mm. A total of 45 typodont teeth (maxillary central incisors) were selected for this study. The teeth underwent endodontic treatment and were divided into three subgroups, each with 15 teeth, based on the desired post space lengths: 6, 8, and 10 mm. Intraoral scans of all specimens were acquired directly using the CEREC Primescan intraoral scanners by two trained examiners. The obtained scan data were compared with conventional impressions obtained using light and heavy bodies of polyvinyl siloxane (PVS). As a control, the conventional impressions were subsequently scanned using an inEos X5a lab scanner. The accuracy of the digital scans was evaluated in the coronal, middle, and apical thirds using the Geomagic Control X software. Statistical analysis was performed using Bonferroni Post-hoc and One-way ANOVA tests to analyze the data. The overall mean root mean square (RMS) deviations for the different post lengths across the three thirds groups were 58, 81, and 101 μm for the 6, 8, and 10 mm subgroups, respectively. There were no statistically significant differences in the accuracy of the coronal and middle thirds among all subgroups (p > 0.5). However, in the apical third, the 10 mm subgroup exhibited a significantly lower accuracy (163 μm) compared to the 6 mm (96 μm) and 8 mm (131 μm) subgroups (p < 0.05). These results suggest that while the accuracy of intraoral scans using direct IOS impressions was consistent in the coronal and middle thirds regardless of the post length, there was a noticeable decrease in accuracy in the apical third, particularly with longer post lengths. Considering the limitations of this in vitro study, chairside direct IOS impressions offer a viable and clinically acceptable alternative to the conventional impression technique for post space lengths of 6 and 8 mm. However, as the post space length preparation increases, the accuracy of IOS decreases. The Chairside direct IOS enables expedited and efficient digital impression capture within the root canal, ensuring acceptable accuracy for intracanal post length preparation of up to 8 mm.

Influence of trapping efficiency on the pile-up geometry of granular flows behind slit dams

The post spacing of slit dams is a key parameter that controls the trapping efficiency of these open-type countermeasures. In this study we conduct flume experiments of quasi-monodisperse spherical particles passing through slits to investigate the relationship between the trapping efficiency and the pile-up geometry, as well as the impact of the latter on the interaction between granular flows and slit dams. The ratio of the slit width relative to the particle size b/d is varied while the flume inclination is held constant. Tests reveal that at a critical ratio b/d∼2.3 trapping is most unstable. The trapping efficiency influences the geometry of the granular pile-up that deposits behind the dam after it has been jammed. When >52% of the granular mass is trapped (occurring at b/d≤2.3), the height of the final deposit changes with the trapping efficiency, whereas below this threshold value (when b/d≥3.1)the flow-wise length becomes more sensitive to the trapping. Impact force measurements further shed light on the mechanisms relating the trapping efficiency and the geometry and their effect on the total force fluctuations.

Comparative evaluation of accuracy of post space scanned with three different techniques

The aim of this in vitro study is to compare three different techniques of scanning post space at different depths.The important factor for success of treatment depends on endodontic treatment as well as by restoring it with prosthodontic treatment. The post is mainly used to retain and hold the core so that crown prosthesis can be given.Fifteen freshly extracted single rooted teeth were selected and endodontically treated. Post space were created. Total Sample size taken was fifteen. There were three groups each with sample size of five. First group consist of Post space scanned with Omnicam intra oral scanner. Second group consist of Post space pattern scanned with InEos X5 Extraoral scanner. Third group consist of Post space impression made with Addition silicone, Poured and scanned with InEos X5 Extraoral scanner. Scanning files of all the three techniques were then converted to standard STL files. Diameter was measured at three different depths i.e., 3mm, 6mm &amp; 9mm. Also, height &amp; diameter was measured by 2 examiners to reduce bias.: The intra oral scanner showed the best accuracy of diameter and as the depth increases the accuracy decreases.Intraoral scanners showed the better accuracy and precision for scanning the post space as compared to extra oral scanner.

Assessment of post space volume change after removal of fiber post by two techniques using CBCT

Assessment of post space volume change after removal of fiber post by two techniques using CBCT

Poly-Ether Ether-Ketone Post Conditioned with Sulfuric Acid, Rose Bengal Activated by Photodynamic Therapy and Sandblasting on Pushout Bond Strength to Radicular Dentin Luted with Methyl Methacrylate and Composite-Based Cement.

Objective: Assessment of post surface conditioners [sulfuric acid (SA), Rose Bengal (RB), and sandblasting (SB)] and different luting cements [methyl methacrylate (MMA)-based cement and composite-based cement] on pushout bond strength (PBS) of poly-ether ether-ketone (PEEK) post bonded to canal dentin. Materials and methods: Endodontic treatment was performed on 120 single-rooted human premolar teeth. The preparation of the post space was performed and 4 mm of gutta-percha was retained in the apical region of the root. One hundred and twenty PEEK posts were fabricated from a PEEK blank utilizing a Computer aided design-Computer aided manufacture (CAD-CAM) system. The PEEK posts were allocated randomly into four groups based on post surface conditioning (n = 30). Group A: SA, Group B: RB, Group C: SB, and Group D: No conditioning (NC). Each group was further divided into two subgroups based on the luting cement used for bonding (n = 15). Group A1, B1, C1, and D1 specimens were cemented using composite-based resin cement. However, Group A2, B2, C2, and D2 posts were luted with MMA-based resin cement. PBS assessment using a universal testing machine was performed. Failure modes were analyzed under a stereomicroscope. The data relating to the effects of surface treatment and luting types of cement were analyzed using one-way analysis of variance (ANOVA) and Tukey's post hoc test (p = 0.05). Results: Coronal section of Group B2: RB+Super-Bond C&B [9.61 ± 0.75 megapascals (MPa)] displayed the highest bond scores of PEEK after root dentin. Whereas it was also discovered that Group D1: NC+Panavia®V5 (2.05 ± 0.72 MPa) presented the lowest PBS scores. Intergroup comparison analysis revealed that Group A2: SA+Super-Bond C&B and Group B2: RB+Super-Bond C&B displayed no significant difference in their bond scores. Conclusions: RB and SA possess the potential to be used as a PEEK post conditioner. MMA-based cement displayed better performance than composite-based cement.

Comparative Study of Bond Strength of Resin-Modified Glass Ionomer Cement and Flowable Composite with Glass Fiber Posts by Push-Out Test

Introduction: posts that have been properly fitted can withstand torsion and provide better retention. The purpose of this study was to evaluate the push-out bond strength of glass fiber posts cemented with different luting agents. The push-out bonding strength of glass fiber posts to the root canal was evaluated using resin-modified glass ionomer cement (RMGIC) and flowable composite (FC). Materials and Methods: Thirty single-rooted extracted human mandibular premolars were sectioned 2 mm coronal to the most incisal point of the cementoenamel junction. Root canals were instrumented and obturated with laterally condensed gutta-percha and root canal sealer (ADSEAL). Gutta-percha was removed from the canals to a depth of 11 mm and diameter post spaces with a 1.5 mm were prepared. The specimens were divided into the following 3 groups according to the luting agent used (n=10). The first group utilized FC (HARVARD, Germany) to coat the post, whereas the second group used RMGIC (Meron plus QM, VOCO, Germany). whereas the third group used Resin Cement (ITENA clinical, France) was used as the control. The specimens were cross-sectioned after 24 h. Specimens were cross-sectioned six millimeters thick into coronal using a sectioning machine. The strength of the bond between the luting cement and the posts was measured using push-out bond strength testing. We loaded the components at a cross speed of 0.5 mm/min on a universal testing machine until the bond failed. Results: The FC group had a 73.53N push-out bond strength, whereas the RMGIC group had a 133.55N, whereas the Resin Cement group had a 137.47N push-out bond strength. Conclusion: FC’s mean push-out bond strength score is lower than RMGIC’s and Resin Cement.

Effect of chlorhexidine and benzalkonium chloride on the long-term push-out bond strength of fiber posts.

Fiber posts are widely used in endodontically treated teeth with extensive loss of coronal structure. The purpose of this study was to investigate immediate and the long-term effects of chlorhexidine (CHX) and benzalkonium chloride (BAC) application, on the push-out bond strength of fiber posts. Sixty mandibular premolars were decoronated, and root canal treatment was performed. After post space preparation, the specimens were divided into three groups according to the post space-surface pretreatment (n = 20); no surface treatment (control group-Group 1), 2% CHX application (Group 2), and 1% BAC application (Group 3). A self-curing adhesive cement and an etch and rinse adhesive were used for the cementation of posts. Three sections (one cervical, one middle, and one apical) of 1 mm thickness were prepared from each specimen. A push-out test was performed immediately on the half of the specimen sections (n = 10). The other half of the specimen sections were subjected to 20.000 thermal cycles before applying the push-out test (n = 10). The failure mode of each specimen was observed under a stereomicroscope at ×40 magnification. The data were analyzed by one-way analysis of variance (ANOVA), Tukey Honestly significant difference (HSD), and Tamhane tests (P = 0.05). The cervical thirds displayed the highest, and the apical thirds showed the lowest values in all groups (P < 0.05), except the control-aged group (P = 0.554). The aged control groups' values were found to be significantly lower than the aged CHX and BAC groups (P < 0.001). Aging significantly reduced the bond strength values of specimens in control groups (P < 0.001). However, aging did not significantly affect the push-out bond strength values of CHX and BAC groups (P > 0.050). The failure types were adhesive between the post and cement (type 1) in all groups, except control-aged group (type 2). The application of 2% chlorhexidine or 1% BAC may be an essential step that can be taken to preserve the bond strength of fiber posts.

Evaluation of custom posts and cores fabricated by two digital technologies in core and post space dimensions.

To evaluate the adaptability between posts and post spaces and the rationality of cores fabricated by two digital custom post-and-core processes. Titanium post-and-cores were fabricated by digital scanning impression technology or digital scanning wax-pattern technology on tooth defect molds of incisors, premolars, and molars, with traditional lost-wax casts of these teeth as the controls. Micro-CT and a laboratory scanner were used to determine intervals between post wall and root canal wall of the root apex, middle, and cervix of each sample in cross-, sagittal, and coronal sections; intervals between the end of post and tooth; diameters of cervical, middle, and incisal part at cross-, sagittal, and coronal sections of each sample, as well as shoulder widths. The three fabrication processes showed significant differences in intervals between post-and-core prostheses and root canal walls, diameters of all parts of cores, and shoulder widths. Scanning impressions showed significant advantages in the main part of post-and-cores in incisors and premolars, while the scanning wax-pattern process showed obvious inferiorities in premolars and molars. As to core spatial size, values of measured sites in the scanning impression process were closer to the standard than those of the traditional process, while differences between the measured value of the scanning wax-pattern process were much more obvious than in the traditional process. The use of digital custom post-and-core scanning impressions improved the rationality and precision of post-and-core dimensions compared with two other processes.

Effect of Ferrule Location on Fracture Resistance of Maxillary Premolars: An In Vitro Study.

The present study aimed to assess the effect of ferrule location on fracture resistance of maxillary premolars. A total of 72 extracted human maxillary premolars were selected and randomly assigned to six groups (n = 12 in each) considering ferrule location: circumferential ferrule (CF), without ferrule (WF), buccal ferrule (BF), lingual ferrule (LF), mesial ferrule (MF), and buccal-lingual ferrule (BLF). Cast posts were cemented into the prepared post spaces. Following conventional impression, Ni-Cr crowns were cemented to the specimens. After thermocycling (5,000 cycles, 5-55°C), the specimens were loaded at 45° in a universal testing machine until fracture. Data were analyzed with one-way ANOVA, Kolmogorov-Smirnov, and Tamhane tests. The maximum and minimum mean fracture resistance were related to the CF (1,143.84 N) and WF (514.89 N) groups, respectively, (P = 0.039). Fracture resistance in the BF (933.67 N) and BLF (874.01 N) groups was significantly higher than in the MF group (617.54 N) (P = 0.001). There was no significant difference between the MF, LF (722.89 N), and WF groups in terms of fracture resistance (P > 0.05). Teeth with CF showed maximum fracture resistance. The location of the ferrule effects on the fracture resistance of maxillary premolars and also the mode of failure.

Suppressing the pancake bouncing induced secondary contact on superhydrophobic surfaces via jet splash

Pancake bouncing of water droplets on superhydrophobic surfaces has been extensively studied, because the reduction in solid–liquid contact time shows great potential for self-cleaning, anti-icing, etc. However, the behavior of a pancake-bouncing droplet in the ambient air and its subsequent interaction with the underlying surface remain unrevealed, which is actually crucial for practical applications. In this Letter, we comprehensively investigate the overall dynamics of droplets on post-array superhydrophobic surfaces by extending the range of impact velocities. An unreported phenomenon was observed, whereby the retracting droplet undergoes vertical elongation and re-contacts the underlying surface following the pancake bouncing event. As the impact velocity increases, the submillimeter-scale posts notably influence the droplet splash, where tiny droplets are ejected from the edges of lateral liquid jets through the posts. Experimental results and scale analysis show that the critical Weber number for this jet splash phenomenon decreases with the post spacing and the post edge length over a certain range. The violent jet splash occurring at higher Weber numbers reduces the mass of the remaining droplet and, consequently, diminishes the diameter prior to retraction, thereby suppressing the secondary contact with the surface. Our findings are believed to provide valuable insight for the understanding and the application of the pancake bouncing effect.