Crosshead Speed Research Articles

Evaluation The Effect of Incorporation of Different Herbal Extract Powders (Either Neem or Aloe Vera) On Thermal Conductivity and Shear Bond Strength of Acrylic Soft Denture Liner Material

The main drawbacks of the soft liners were poor thermal conductivity and poor bonding between denture base and soft lining. The purpose of this study was to analysis the influence of incorporating either Neem or Aloe Vera on thermal conductivity and shear bond strength of heat cure acrylic soft liner. Sixty heat cure acrylic soft liner specimens were prepared and classified as two major groups based on tests that evaluated (thermal conductivity and shear bond strength), each major group sub classified for three groups based on incorporated material: The control group (10) specimens, (10) specimens with 10% by weight of Neem powder; (10) specimens with 10% by weight of Aloe Vera powder. Thermal conductivity specimens were fabrication with dimensions of (40 mm diameter × 2.5 mm thickness). Two acrylic block of shear bond strength specimens with dimensions (75mm × 25mm × 5 mm length, width, depth respectively) was fabrication. The reline material application on space between two acrylic blocks. The (Lee disc) equipment was used to assess thermal conductivity. With a crosshead speed of 0.5mm/min, a shear bond strength was measured. Data statically analyzed by One-way ANOVA and LSD tests. The results showed the Neem group had highest mean value of thermal conductivity and shear bond strength than aloe Vera and control groups at p<0.01. Either Neem or Aloe Vera increased thermal conductivity and shear bond strength of soft liner.

Comparison of retention of monolithic zirconia crowns with alumina airborne-particle abraded and nonabraded intaglio using three different cements: A clinical simulation

The necessity of roughening the intaglio surface of zirconia crowns to achieve adequate retention is unclear. The purpose of this clinical simulation study was to evaluate the retention of airborne-particle-abraded and nonabraded monolithic zirconia crowns using 3 different cement types. Extracted human molars were used and prepared with a 10-degree taper. Impressions were made of the prepared teeth with a polyvinyl siloxane (PVS) material, and dies were made with Type 4 gypsum. Each die was scanned with a NobelProcera 1G Scanner, and the standard tessellation language (STL) files were transferred electronically to the Nobel Biocare production site, where a bar was added virtually on top of each crown and parameters were set for milling. Seventy-two Procera zirconia crowns were generated, of which half were airborne-particle abraded on the intaglio surface with 50-µm alumina particles at 400 to 500 kPa for 15 seconds. The other 36 received no intaglio treatment other than cleaning. Both groups of 36 crowns were divided into 3 subgroups of 12 specimens. The area of each preparation was calculated using a computer-aided design software program. The specimens were distributed to attain similar mean surface areas among the cementation groups. The crowns were cemented onto the specimen with a controlled force of 196N. The 3 cements used were self-adhesive, modified resin RelyX Unicem Aplicap, resin-modified glass ionomer RelyX Luting, and a composite resin, Panavia F2.0 with ED Primer A & B. All specimens were thermocycled (5 °C to 55 °C) for 5000 cycles and then removed axially with a universal testing machine (Instron Model 5585H) at a crosshead speed of 0.5mm/min. The removal force was recorded, and stress of dislodgement was calculated for each crown. A 2-way analysis of variance was used for statistical analyses. The type of failure was analyzed with the chi-squared test of association for independent samples (α=.05 for all tests). The mean dislodging force for crowns with airborne-particle abraded intaglio was 5.4MPa, which was statistically greater than the mean of 3.2MPa for nonabraded specimens (P<.001). No significant differences related to the dislodging stresses were detected among the 3 cements (P=.109). The mode of failure was similar whether abraded or not, with 50% of specimens retaining cement in the crown after separation. Alumina airborne-particle abrasion of the intaglio of zirconia to create surface roughness is beneficial in retaining the crowns, regardless of the cement type. The nonabraded crowns demonstrated significantly lower retentive stress with crown removal. The principal mode of failure was similar whether the zirconia intaglio was airborne-particle abraded or not. The most common mode of failure (>50% of specimens) was at least three-fourths of the cement remaining within the crown.

The Effect of Microwave Irradiation and Some Denture Cleansers on The Bond Strength of Soft Liner to CAD/CAM-Milled Acrylic Resin

Disinfection of dentures and denture liners was desired for cross-contamination prevention and improved safety. Nonetheless, it has been discovered that these procedures impact the physical and mechanical features of denture liners.To assess the impact of different disinfection procedures on the tensile bond strength of an acrylic-based soft liner with CAD/CAM-based acrylic denture resin. Material and Methods: 25 specimens were collected and randomly divided into five groups (sodium hypochlorite, chlorohexidine, cleansing tablet, microwave, and control groups), following the daily disinfection protocol, the samples were stored at room temperature (23±2°C) in distilled water. After 30 days, the tensile bond strength was determined using universal testing equipment (Gester, China). The specimens were subjected to force by the machine at a steady crosshead speed of 5 mm/minute till the failure was recorded. The data were analyzed using statistics software (SPSS). Results: Showed that the control group had a higher mean value for bond strength, whereas the chlorhexidine group had a lower value. There was no significant difference between the control and cleansing tablet groups. However, they were significantly different from the microwave, CHX, and NaOCl groups. The NaOCl soft liner group is significantly different from all the other groups. No significant difference is found between microwave and CHX disinfected liner groups. Conclusion: The tensile bond strength of all disinfected soft liners decreased as compared with the control, which was not significant with the protefix tab but significant with the NaOCl, CHX, and microwave groups.

Effect of desensitizing agents on the resin bond strength to sound dentin.

This study aimed to evaluate the effect of dentin hypersensitivity treatments on immediate and long-term shear bond strength (SBS) of composite restorations. Ninety non-carious extracted human molars were cut to expose dentin, which was embedded in acrylic resin, and randomly divided into three groups (n = 30/group) according to surface treatment: 1) no treatment (C and C*; control); 2) silver diamine fluoride with potassium iodide (SDF/KI and SDF/KI*; Riva Star); and 3) nano-hydroxyapatite (nHAp and nHAp*; PrevDent). The specimens were etched through the etch-and-rinse technique, followed by universal adhesive application and resin composite cylinders (2.38mm in diameter × 3.5mm high). The SBS was tested immediately (24h after the restoration) and after thermocycling (*) (5000 cycles, 5°C to 55°C) at a 0.5mm/min crosshead speed using a universal testing machine. A stereomicroscope was used to evaluate the mode of failure, and representative scanning electron microscopy (SEM) images were also acquired. Data normality was verified, and two-way ANOVA and Tukey's post hoc tests were performed for multiple comparisons (α = 0.05). The control group presented the highest SBS (27.10MPa), while SDF/KI* had the lowest values (6.87MPa). nHAp-based desensitizer exhibited higher SBS than SDF/KI for both immediate (22.6MPa) and thermocycled (19.03MPa) conditions. No intragroup difference was evidenced between immediate and thermocycled samples for any group. Most specimens for the C and nHAp groups presented mixed failure, while the SDF/KI groups presented comparable adhesive and mixed failures. The SBS of adhesive restorations after the application of desensitizing agents is material dependent, where SDF/KI reduces SBS values below the acceptable minimum bond strength, while the nHAp application meets the minimally required bond strength.

Flexural strength and Vickers hardness of milled and 3D-printed resins for provisional dental restorations

Various forms of temporary resins are offered on the market; however, the properties of temporary resins obtained by milling and 3D printing have not been fully examined. This study aimed to compare the flexural strength and Vickers hardness of milled and 3D-printed resins. Methods: Three resins were tested: Evolux PMMA (milled resin), Cosmos Temp (3D-printed resin), and Structur 2 SC (bis-acrylic resin, group control). Specimens were prepared with rectangular shapes (n = 12) for flexural strength measurements and disc shapes (n = 9) for Vickers hardness tests. Flexural strength tests were performed at a crosshead speed of 0.75 mm/min, and the Vickers hardness was measured under a load of 20 N for 10 s. The obtained data were subjected to the Kruskal–Wallis test. Results: A significant difference (p &lt; 0.05) in flexural strength was observed among the three sample groups: Evolux PMMA (111.76 MPa), Structur 2 SC (87.34 MPa), and Cosmos Temp (56.83 MPa). No significant difference (p &lt; 0.05) was observed between the Vickers hardness values of Structur 2 SC (33.37 VHN) and Evolux PMMA (29.11 VHN); however, both materials were statistically superior to Cosmos Temp (10.90 VHN). Conclusion: While the mechanical properties of the milled resin were superior or similar to those of the bisacrylic resin, the 3D-printed resin was statistically inferior to both the milled and bis-acrylic resins.

Comparative Evaluation of Application of Universal Bonding on the Microtensile Bond Strength of Light Cure and Dual Cure Composites Bonded to Dentin.

Objectives: There is limited knowledge on the efficacy of universal adhesives when used in different etching modes. The aim of this study was to evaluate the microtensile bond strength (µTBS) to dentin using universal adhesives with light-cure and dual-cure composites. Materials and Methods: In this in vitro experimental study, the occlusal third of 60 caries-free human molars were removed and the exposed surfaces were treated and allocated to 10 groups (N=6). Two different bonding agents (Single Bond Universal, G-Premio) were used to bond 2 different composite resins (Z250 light-cure and CoreFlo DC dual-cure) to dentin, using etch-and-rinse (E&R) and self-etch (SE) modes. Single Bond 2 was applied in E&R mode on wet dentin to serve as control. The specimens were sectioned into 1×1 mm2 sticks with a precision saw. A microtensile testing machine was used to measure the µTBS of the specimens with a crosshead speed of 0.5 mm/min. Data were analyzed using three-way ANOVA and Bonferroni post-hoc test (α=0.05). Results: The Single Bond Universal group in SE mode with light-cure composite yielded the highest (39.24MPa), and the G-Premio SE group with dual-cure composite produced the lowest (13.65MPa) mean µTBS (P<0.05). The dominant failure mode was adhesive, in all groups. Conclusion: The bonding agent had a significant effect on µTBS of composite to dentin, but different composites and different etching modes were not significantly different in this respect.

Comparison of Fracture Resistance between Different Treatment Modalities of Mutilated Endodontically Treated Teeth Using Polyether Ether Ketone.

To compare fracture resistance of multiple treatment modalities intended for mutilated teeth using polyether ether ketone (PEEK) and zirconia materials. The study was divided into four groups according to treatment modality adopted (n = 14): fiber post (F), Nayyar core (N), endocrown (E), and Richmond crown (R). Each group was further subdivided into two groups (n = 7) according to the type of material used: zirconia (Z) and PEEK (P). Using computer-aided design/computer-aided manufacturing, restorations were constructed from both materials following tested treatment options and manufacturer direction. Finished restorations were then tried, seated, and cemented to their corresponding acrylic teeth. All specimens were tested for fracture resistance in universal testing machine with cross head speed of 0.5 mm/min speed until failure, which was confirmed by a sudden drop in the measurements of the testing machine. Results were recorded, tabulated, and statistically analyzed. Shapiro-Wilk normality tests were considered to evaluate the normality of the data distributions. One-way analysis of variance (ANOVA) followed by Tukey's post hoc analysis was conducted to analyze the fracture resistance significant differences. Descriptive statistics of the restoration material revealed statistically a higher mean value for PEEK material (3609 ± 188.1) than zirconia (2404 ± 425.6). One-way ANOVA revealed statistically significant differences between zirconia group (p < 0.0001). Regarding zirconia group statistical significance was detected between fiber post vs endocrown (p = 0.0299), fiber post vs Richmond crown (p < 0.0001), and Nayyar core vs Richmond crown (p = 0.0004). However, there was no statistically significant difference between PEEK group (P = 0.1614). Polyether ether ketone could present a reliable treatment option in endodontically treated teeth. Using one-piece Richmond crowns constructed of PEEK could present a viable treatment option against conventional treatment options of root canal treatment (RCT) single-rooted teeth.

Investigation of an optimized hot press process design for manufacturing structural polyethersulfone foams

Semi-finished thermoplastic foam panels can be transformed into structural foams—a sandwich-like structure with high-density skins—through thermoforming. This transformation enables the production of mono material sandwich panels, which allow a significant increase in bending properties without increasing the part weight. This study describes the effect of process parameters on skin formation in thermoplastic structural foams manufactured in a two-step isochoric and isothermal hot press process. Process data recorded during foam manufacturing was analyzed and compared to foam behavior in quasi-static isothermal compression tests performed at different levels of temperature and crosshead speeds. The effect of skin-core structure on bending properties is compared to theoretical models from the established literature. It was found that a rule of linear mixture that considers the relative skin thickness allows adequate prediction of both bending modulus and strength. Preferable process design—especially combinations of tool temperature and maximum compaction speed—is described based on the comparison of measured and predicted performance.

Effects of the application of sodium ascorbate after in-office bleaching on the penetration of hydrogen peroxide, color change, and microtensile bond strength.

This study aimed to evaluate the effects of the application of 10% sodium ascorbate (SA) after in-office bleaching on the penetration of hydrogen peroxide (HP) into the pulp chamber, color change, and microtensile bond strength (µTBS) to the resin-enamel interface. Thirty premolars and thirty molars were randomly divided into three groups (n = 20 each). One group was exposed to deionized water (negative control). The other two groups were bleached with 35% HP in a single session for 3x15 minutes for each application. However, in only one of them, SA was applied for 10 minutes after bleaching. After, the concentration (µg/mL) of HP in each pulp chamber was evaluated by UV-Vis spectrophotometry. Color changes (ΔEab, ΔE00, and ΔWID) were evaluated with a digital spectrophotometer before and in the first week after bleaching. After treatment, molars were restored and sectioned to obtain resin-enamel interface sticks for µTBS at a crosshead speed of 1 mm/min until failure. The HP concentration and µTBS data were analyzed using one-way ANOVA and Tukey tests, and color changes were analyzed by t-tests (α = 0.05). SA application significantly improved the µTBS values and reduced the HP concentrations within the pulp chambers (p < 0.0001). The application of SA significantly interfered with the color changes after bleaching when compared to the control group (p < 0.05). Application of 10% SA after in-office bleaching successfully reduced the penetration of HP into the pulp chamber; however, it decreased color change.

Load capacity and fracture modes of instrumented tooth roots under axial compression.

To investigate the influences of root canal instrumentation on the load capacity and fracture modes of tooth roots under axial compression by performing mechanical tests and finite element analysis (FEA). Thirty bovine incisor roots were trimmed into cylinders of 5.0mm diameter. They were randomly divided into two groups, one with root canals instrumented to ∼2.0mm in diameter, and one without instrumentation. The specimens were fractured under uniaxial compression at a crosshead speed of 0.2mm/min, and then micro-CT was used to reveal the fracture patterns in three dimensions. FEA was further performed, using the extended finite element method (XFEM), to compare the compression-induced stress distributions and the initiation and propagation of root fractures in both groups. The mean fracture load of the non-instrumented group (2334±436N) was statistically significantly higher than that of the instrumented group (1857±377N) (p<0.01). Three types of root fractures were identified according to the path and length of the cracks: end-face crack, partial-length crack, and full-length crack. As to the fracture modes, the incidence of partial-length root fracture was the highest in both groups (60% for the non-instrumented group and 53.3% for the instrumented group), followed by that of full-length fracture (26.7% and 40%, respectively) and then end-face fracture (13.3% and 6.7%, respectively). The percentage of full-length fracture was slightly higher in the instrumented group. FEA showed that the compression induced higher Tresca stresses but lower maximum principal stresses in the canal walls of the instrumented group. The XFEM simulations predicted that the fracture of both groups initiated from the outer root surface near an end face and propagated axially to the middle third of the root and radially towards the root canal. These numerical results agreed well with our experimental findings. Within the limitation of this study, it was found that root canal instrumentation could significantly decrease the load capacity of tooth roots and potentially increase their susceptibility to full-length root fracture under uniaxial compression.

Comparative Evaluation of the Mechanical Properties of a Bioactive Material Enhanced by Phytosynthesized Nanoparticles: An In vitro Study.

The aim was the study was to evaluate and compare the mechanical properties of ACTIVA Bioactive Base/Liner (ABBL) enhanced with phytosynthesized titanium dioxide nanoparticles (nTiO2) and nano-curcumin (nCur). Thirty samples each of ABBL (Group 1), ABBL + nTiO2 (Group 2), and ABBL + nCur (Group 3) were prepared for testing the compressive strength (CS) and flexural strength (FS). Forty-five cylinders (15 per group) (6 mm × 4 mm) were fabricated for CS and 45 for three-point bending FS measurements (22 mm × 2 mm × 2 mm). They were tested in a universal testing machine at a crosshead speed of 0.5 mm/min for CS and 0.5 mm/min with 20 mm space between the two supports for FS measurements. Intergroup comparison of CS and FS was assessed using one-way ANOVA. The level of significance was set at 0.05. Intergroup comparison showed an overall significant difference (P = 0.016 for CS) and (P = 0.001 for FS), where Group 1 had the highest and Gr 3 the least strength. No significant difference was observed between Group 1 and Group 2, while Group 3 showed significantly low strength when compared to Group 1. ABBL + 3% nTiO2 showed nonsignificant decrease while ABBL + 7% nCur showed significant decrease in mechanical properties.

Evaluation of Retention and Fracture Strength of All Ceramic Crowns with Three Different Esthetic Cast Post-Core Systems.

This study investigates the fracture and retention strength of all-ceramic crowns with modified composite resin and ceramic cores compared to conventional casted post and core systems. A prepared human central tooth was initially scanned to design and 3D print the post and core. Subsequently, 40 bovine teeth were adjusted to accommodate the fabricated post and cores. They were then divided into four groups of 10 each: group 1 comprised cast cores without cover (control group), group 2 involved cast cores reduced and replaced with IPS Empress material (IPS group), group 3 consisted of cast cores covered with opaque composite (composite group), and group 4 included cast cores covered with opaque ceramic (ceramic group). Zirconia crowns were cemented onto all samples. After an aging process, pull-off and fracture strength tests were conducted. Fracture strength was determined by applying a compressive force at an angle of 135° to the tooth's longitudinal axis until the fracture occurred. For retention strength assessment, a universal testing machine with a 10 mm/min crosshead speed was employed. The resulting data underwent statistical analysis utilizing two-way analysis of variance (ANOVA) and Mann-Whitney U tests. The analysis revealed no significant difference in fracture strength among the groups (P-value = 0.997). However, the retention strength of the control and IPS groups was significantly higher than that of the other groups. There were no discernible distinctions among the three study methods regarding fracture strength. Nonetheless, the retention strength of the IPS group resembled that of the control group, surpassing that of the composite and ceramic groups.

Predicting the lifetime of CPVC under increasing temperature and crosshead speed

CPVC is an increasingly popular material for plumbing pipes and other applications that require strong and temperature-resistant material. This resin is created using a chlorination process, giving it Chlorine levels that range from 63 to 69% and thus a unique set of characteristics that make it ideal for certain applications. CPVC's combination of corrosion-resistance and low installation costs make it a great substitute for copper in environments with non-ambient conditions such as higher temperatures. This makes it an economic choice for many projects that require smaller budgets. With a variety of applications, CPVC provides a great alternative requiring strong and durable material. The aim of this paper is to characterize the mechanical characteristics of chlorinated PVC (CPVC). Tensile tests were carried on the compounds at different temperatures ranging from -20 to 90°C and crosshead speeds from 5 to 500 mm/min. The results were analyzed to determine how crosshead speed and temperature affected on the mechanical characteristics of CPVC specimens. Two damage models are then developed, one model obtained through by adapting the unified theory version and the other quasi-experimental static model based on ultimate stress. These models allow us to evaluate the damage evolution of CPVC samples and to determine the safety and maintenance intervals of this material.

The impact of print orientation on the fracture resistance and failure patterns of additively manufactured cobalt-chromium post and cores.

The aim of this study was to evaluate the impact of the print orientation of direct metal laser sintering (DMLS) posts and cores on the fracture resistance and failure patterns of endodontically treated mandibular premolar teeth. Sixty intact human mandibular premolars were endodontically treated. The teeth were then randomly divided into four groups (n = 15). Cobalt-chromium (Co-Cr) metal posts were fabricated by traditional casting (Group C), and DMLS method in 0-, 45-, and 90-degree print orientations (Group DMLS 0, Group DMLS 45, and Group DMLS 90). The posts and cores were cemented with composite resin cement and subjected to compression test at a crosshead speed of 1mm/min. Data was analyzed by using one-way analysis of variance ANOVA and multiple comparison post hoc Tukey tests (α = 0.05). Specimens were viewed under a stereo microscope with x20 magnification to evaluate the fracture types. No significant differences were found among the groups tested in terms of fracture resistance (p>0.05). Group C and Group DMLS 0 group exhibited similar fracture patterns. It is possible to produce post and core restorations with the DMLS technique and use them clinically. Print orientation did not influence the fracture resistance. However, fracture patterns were different. Group C outperformed all DMLS groups in terms of fracture patterns.

A comparison of the shear bond strength between denture teeth and denture base resins manufactured either conventionally or with a 3D printer

Statement of problemLimited information is available on the shear bond strength (SBS) between denture teeth and denture base resins fabricated using a stereolithography (SLA) 3-dimensional (3D) printer. PurposeThe purpose of this in vitro study was to evaluate the SBS between denture teeth and the denture base resins produced with the conventional method and with a 3D printer. Material and methodsConventional or 3D printed denture teeth were included in the study. The denture base resins were manufactured either conventionally or with a 3D printer. Four subgroups were tested: conventional teeth-conventional base resin (CT-CB), conventional teeth-printed base resin (CT-PB), printed teeth-conventional base resin (PT-CB), and printed teeth-printed base resin (PT-PB). The maxillary molars were combined with Ø5×2.5-mm-cylindrical denture base resin. Shear bond testing was performed by applying a parallel force to the denture teeth-denture base resin interface by using a blade-edge chisel with a crosshead speed of 1 mm/min until failure occurred. SBS and elastic modulus (EM) were recorded. One-way ANOVA followed by the Dunnett T3 post hoc test was used for the statistical analysis (α=.05). The failure modes of the specimens were also analyzed. ResultsA statistically significant difference (P<.05) was found between the evaluated groups for the SBS and EM values. PT-PB showed the highest SBS value (15.4 ±2.7 MPa), and CT-PB showed the lowest (0.9 ±0.7 MPa). The PT-CB group showed the highest EM value (62.74 ±20.80 GPa), and the CT-PB group showed the lowest (29.46 ±28.40 GPa). The CT-CB and CT-PB specimens showed mostly adhesive failure; none of the PT-PB specimens showed adhesive failure. ConclusionsThree-dimensional printing led to a better bond between the denture teeth and the denture base resin compared with the conventional method. Although these findings need to be supported by clinical studies, the use of 3D printers is appropriate in the production of denture teeth and denture bases.

Rheological and Mechanical Properties of an Acrylic PSA.

The adhesion of pressure-sensitive adhesives (PSAs) is a complex phenomenon that can be understood through the characterization of different properties, including viscoelastic, mechanical, and fracture properties. The aim of the present paper is to determine the viscoelastic behaviour of an acrylic PSA and place it in the viscoelastic window, as well as to determine the tensile strength of the material. Additionally, different numbers of stacked adhesive layers and two crosshead speeds were applied to characterize the tensile strength of the adhesive in the different conditions. Adding a new interface between layers showed a negative influence in the tensile strength, while a higher crosshead speed implied a considerable increase in the same value. Finally, double cantilever beam (DCB) fracture tests were performed, and the J-integral approach was used to evaluate the fracture energy throughout the tests. The substrate roughness, the number of stacked layers, and the thickness of the PSA proved to decrease the performance of the PSA in fracture tests. While tensile bulk tests in viscoelastic materials are not easily found in the literature, as well as DCB tests, for fracture characterization, the obtained results allowed for the characterization of those properties in an acrylic PSA.

Shear Bond Strength of Light Cured Resin Composite to Bleached Enamel Pre-Treated with Probiotic

Aim: To assess the Shear Bond Strength (ShBS) of light cured composite resin to bleached enamel pre-treated with probiotic. Materials and Method: 40 extracted permanent maxillary central incisors teeth were obtained, decoronated, mounted on resin blocks and grouped into four namely Group 1: Resin Composite restoration done without bleaching (positive control), Group 2: Vital bleaching is done with 40% hydrogen peroxide for 20 minutes followed by composite restoration (negative control), Group 3: Composite restoration delayed by 4 weeks after vital bleaching, Group 4: Composite restoration on bleached enamel pretreated with probiotic for 60 minutes. All the specimens were conserved for one day (24 hours) in deionized water and subjected to analysis for ShBS using cross head speed of 0.5 mm per minute. Statistical Analysis: Data was tabulated on excel sheet and analyzed statistically using SPSS software. Results: One way ANOVA statistical test showed a statistically significant difference in the mean ShBS values between the groups. Group 1 (positive control), Group 3 (delayed bonding), and Group 4 (probiotic) had considerably higher values of mean ShBS than Group 2 (immediate bonding). Conclusion: Probiotic pre-treatment on bleached enamel was able to effectively reverse the effect on ShBS of enamel treated with bleaching agent.

Effect of green tea extract antioxidant on dentin shear bond strength and resin-tag penetration depth after non-vital bleaching.

Background: 35% Hydrogen peroxide (H 2O 2) as an active material for internal bleaching can produce free radicals that can affect resin tag penetration into the dentinal tubules. Application of 10% and 35% green tea (GT) extract as an antioxidant after 2 minutes are expected to remove free radical residues and increase dentin shear bond strength and resin tags penetration depth after non-vital bleaching. Methods: 30 extracted healthy human premolars were cut horizontally 2 mm from the Cemento Enamel Junction margin to the crown part, then cut in a mesio-distal direction into two parts. The specimens were divided into five groups: normal dentin, post bleaching dentin, delayed 2 weeks, 10% GT, and 35% GT group. Non-vital walking bleach with 35% H 2O 2 gel was done to all groups except control group. Soon after, 10% and 35% GT extract gel were applied on dentin for 2 minutes, then the specimens were rinsed-off with aquabidest for 2 minutes and dried. All specimens were etched and bonded with an etch-and-rinse adhesive system and filled with resin composite. The shear bond strength assessment was carried out using a Universal Testing Machine (UTM) with a cross-head speed of 0.5 mm/minute. Confocal laser scanning microscopy (CLSM) with a wavelength of 560 nm and a lens magnification of 40x was used to analyze the resin tag penetration. Data were analyzed by one way ANOVA and t-test. Results: There was a significant difference in resin tag penetration depth and shear bond strength between applying 10% and 35% GT extract (p < 0.05). The 35% GT extract group resulted in a significantly longer resin tag penetration than the 10% GT extract group. Conclusions: The application of 35% GT extract is more effective than 10% GT extract as an antioxidant for increasing the shear bond strength of composite resin after internal bleaching.

In vitro assessment of the effect of luting agents, abutment height, and fatigue on the retention of zirconia crowns luted to titanium base implant abutments

Statement of problemThe bonding of implant-supported prostheses is determined by abutment material, convergence angle, height, surface treatment, and luting agents. However, studies evaluating the bonding of luting agents to titanium base abutments with different heights under fatigue conditions are scarce. PurposeThe purpose of this in vitro study was to evaluate the retention of zirconia crowns bonded with different luting agents to titanium base abutments of different heights before and after fatigue testing. Material and methodsZirconia crowns were designed, milled, and distributed into 4 experimental groups according to the luting agents (G-Multi Primer/G-Cem LinkForce [MP/GC] and Scotchbond Universal/RelyX Ultimate [SU/RU]) and titanium base abutment heights (2.5 mm and 4 mm) (n=10). Pull-out testing was performed in a universal testing machine at a crosshead speed of 1 mm/min until crown displacement. Fatigue testing was performed by an electric precision fatigue simulator (1×106 cycles; 100 N; and 15 Hz), followed by pull-out testing of fatigued specimens. Collected data were statistically evaluated by using a linear mixed model after post hoc comparisons by the least significant difference test (α=.05). ResultsLuting agents, abutment heights, and fatigue influenced the bonding retention of zirconia crowns to titanium base abutments. SU/RU agents promoted higher pull-out compared with MP/GC for both abutment heights before and after fatigue. Higher abutment height increased pull-out regarding lower abutment height for SU/RU materials before and after fatigue testing. Although fatigue had no significant effect on the pull-out of MP/GC, lower bond retention was observed for SU/RU after fatigue, regardless of abutment height. ConclusionsLuting agent composition and the interaction with abutment height and fatigue influenced the retention of zirconia crowns to titanium base abutments.

The effect of final irrigation agents on push-out bond strength of calcium silicate-based cements to dentin

Aim: This aim of this study was to compare the effects of different chelating agents [ethylenediaminetetraacetic acid (EDTA), glycolic acid (GA) and citric acid (CA)] on the push-out bond strength (POBS) of two calcium silicate-based silicate cements (CSC) (Biodentine and PD MTA White). Methodology: Dentin discs of 1 ± 0.2 mm thickness were taken from the middle root region of thirty-nine extracted mandibular premolar teeth and two holes (1 mm diameter) were drilled in each disc (n = 78 holes). The samples were then randomly divided into three groups (n = 26 holes) according to the final irrigation agents: Group 1: 20% CA, Group 2: 17% EDTA, Group 3: 10% GA. Then, two different materials were applied to the holes in each group (n = 13 holes): a: PD MTA White, b: Biodentine. POBS test was performed at a crosshead speed of 0.5 mm/min. The dentin discs were examined under stereomicroscope (25×) to assess the bond failure type. Data were analyzed using a two-way analysis of variance (ANOVA) and comparison of main effects was examined with the Bonferroni test, and multiple comparisons were analysed with the Tukey HSD test. The level of signifcance was 5%. Results: Biodentine showed significantly higher POBS than PD MTA White (p &lt; 0.05). There was no significant difference between the final irrigation agents (p &gt; 0.05). CA – Biodentine group showed substantially higher POBS than EDTA – PD MTA White, CA – PD MTA White, and GA – Biodentine groups (p &lt; 0.05). Conclusion: While CA increased the POBS of Biodentine significantly, the POBS of PD MTA White was not affected by the final irrigation agents. How to cite this article: Yeniçeri Özata M, Falakaloğlu S, Batur M, Adıgüzel Ö, Goncharuk-Khomyn M. The effect of final irrigation agents on push-out bond strength of calcium silicate-based cements to dentin. Int Dent Res 2023;13(2):75-82. https://doi.org/10.5577/idr.2023.vol13.no2.5 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.