A Comparison of the Edge Testing of Indirect Composite Layered Zirconia Crowns and Monolithic Zirconia Crowns Without Aging: An In Vitro Study.

Introduction The main reason veneered zirconia restorations fail is due to porcelain veneer chipping. This chipping usually starts from wear marks on the chewing surface. As a result, small cracks under the contact area can grow into larger ones across the veneer layer. The veneer ceramic layer is more vulnerable to fractures because it has lower toughness and slightly lower stiffness compared to the base framework material. Thus, even when there's significant chipping, the main framework material usually stays protected with a thin layer of veneer ceramic on top. The aim of this in vitro study is to compare the edge strength of Monolithic Zirconia Crowns with that of Indirect Composite Layered Zirconia Crowns without aging. Materials and methods This research involved creating 12 hand-layered all-ceramic crowns and 12 indirect composite layered zirconia crowns. The sample size was determined using a G*Power calculation (Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany). The zirconia frameworks (Upcera HT White; UPCERA Dental America Inc., Cerritos, CA, US) were milled and sintered following the manufacturer's instructions. For the all-ceramic group, veneering porcelain (e.max Ceram; Ivoclar Vivadent, Schaan, Liechtenstein) was hand-applied. In contrast, the indirect composite group utilized Ceramage (Shofu, Kyoto, Japan). An Instron 4501 universal testing machine (Instron Corp., Canton, MA, USA) was employed for the edge chipping tests, and a Vickers indenter (Shanghai Toyo Diamond Tools Co., LTD, Shanghai, China) was used to apply the load. The mean value for edge chipping was analyzed using an unpaired t-test with IBM SPSS Statistics for Windows, Version 26 (Released 2019; IBM Corp., Armonk, NY, USA). The normality of the data was confirmed, and statistical significance was set at 0.05. Results Monolithic Zirconia Crowns (Group 1) require significantly more force (mean: 405 N) to induce an edge chip compared to Indirect Composite Layered Zirconia Crowns (Group 2) (mean: 300 N). The 95% confidence interval (83.43261 N to 109.90072 N) confirms the statistical significance of this difference. Conclusion In conclusion, when evaluating restorative materials based on both esthetic and functional criteria, monolithic zirconia stands out due to its combination of strength, esthetic potential, biocompatibility, and versatility.

A Comparative Evaluation of Frictional Resistance of Various Lingual Brackets With Nitinol (NiTi) Archwires of Different Dimensions: An In Vitro Study.

Introduction Orthodontic mechanics involves transferring some of the applied force to the tooth's supporting components via friction, which in turn allows the tooth to move more easily. Aim The purpose of this in vitro experiment was to examine the frictional resistance (FR) of different lingual brackets utilizing Instron universal testing machines and nitinol (NiTi) archwires of varying sizes. Materials and methods Twenty-four sectional anterior die stones were replicated from a study model. They were categorized into eight categories, with the Libral lingual bracket and the JJ lingual bracket having 0.012" and 0.014" inch NiTi archwire, which were further subdivided into six subgroups. Three brackets were bonded to the anterior teeth of the upper and lower segments and replicated on other models with the help of silicon putty. Elastomeric modules were ligated to two diameters of NiTi wire (0.012" and 0.014") in each model. An Instron universal testing machine was used to measure the frictional force. Numerical data and descriptive statistics such as mean and standard deviation have been shown. Results In the overall analysis, it was observed that among JJ Orthodontics samples using 0.012" NiTi archwires, the maxilla exhibited a higher FR (4.205N) compared to the mandible (4.092N). Similarly, in the case of Libral Orthodontics samples with 0.012" NiTi archwires, the maxilla also demonstrated a higher FR (5.10N) than the mandible (4.97N). However, this trend did not hold for samples using 0.014" NiTi archwires. There was a statistically nonsignificant difference (p > 0.05) in the values between all the pairs of groups. Conclusion The present study concludes that Libral lingual brackets produced overall more FR than JJ lingual brackets.

Effectiveness of Different Etching Agents on Enamel Surface and Shear Bond Strength: An In Vitro Evaluation.

Background Enamel etching is of utmost importance during the orthodontic bonding procedure. Phosphoric acid, hydrofluoric acid, and citric acid are used in specific concentrations to create surface irregularities on enamel surfaces, enhancing the bond strength of the orthodontic attachment. Therefore, it is essential to evaluate the type of etchant for reliable orthodontic bracket bonding with minimal damage to the enamel surface. Aims and objectives This study aimed to investigate the morphological changes on the enamel surface after treatment with different surface etchants, assess the depth of penetration, and evaluate the shear bond strength (SBS) of orthodontic brackets. Materials and methods One hundred and one extracted premolar teeth were used to investigate morphological changes on the enamel surface treated with 37% phosphoric acid, 11% hydrofluoric acid, and 20% citric acid. It was evaluated on a scanning electron microscope (Jeol Scientific Equipment, Jeol Limited, Akishima, Japan), and the SBS of brackets on enamel treated with different etching agents was evaluated using an Instron Universal Testing Machine (UTM; Instron Model: 5982, Universal Testing Systems, Norwood, MA). Group A had 60 test samples. Group B had 40 test samples. One control without any acid etching was used in both groups. Subgroup A1 (n = 30) was evaluated for surface characteristics of acid-etched enamel. Subgroup A2 was assessed for the penetration depth of various etchants. Group B (n = 40) was tested for SBS. The results were tabulated and analyzed using IBM SPSS Statistics, version 20.0 (IBM Corp., Armonk, NY). Post hoc Tukey HSD test and one-way analysis of variance were used to assess SBS and penetration depth of etchants (P ≤ 0.05). Pearson's correlation test was used to correlate SBS, etching pattern, and penetration depth. The chi-square test was used to test the frequency of types of etching patterns.  Results Intergroup correlations between etching depth, etching pattern evaluated on SEM, and SBS evaluated on the UTM showed a high statistical correlation between etching depth & SBS, etching depth & etching pattern, and SBS & etching pattern between A1, A2, and group B (P ≤ 0.001). A highly significant negative correlation between SBS & etching pattern (P = 0.42) was observed among intra-group correlation. Non-significant correlations were found between etching depth & SBS and etching depth & etching pattern within the 20% citric acid etch group (P = 0.370 and 0.141, respectively). Conclusion Penetration depth obtained was highest with 11% hydrofluoric acid, followed by 37% phosphoric acid and 20% citric acid. In addition, 11% hydrofluoric acid showed the highest bond strength. Acid etching showed better penetration depth and bond strength than control.

Comparative Evaluation of Shear Bond Strength of Resin-modified Glass Ionomer Cement with ProRoot MTA and MTA Angelus.

AIM: The aim of the present study was to evaluate the shear bond strength of resin-modified glass ionomer cement with two different types of mineral trioxide aggregate at different time intervals. MATERIALS AND METHODS: A total of 80 cylindrical blocks were prepared using a self-cure acrylic resin with a central cavity of 4 mm internal diameter and 2 mm height. The prepared samples were randomly divided into two groups (n = 40 each) according to the type of MTA cements used (ProRoot MTA and MTA Angelus). Two groups were further sub-divided into four sub-groups of 10 samples each according to the different time intervals. ProRoot MTA and MTA Angelus were placed in the prepared cavity and a wet cotton pellet was placed over the filled cavity. A hollow plastic tube was placed over the MTA surface and resin-modified glass ionomer cement (RMGIC) was placed into the hollow plastic tube and light-cured (Spectrum 800, Dentsply Caulk Milford, DE, USA) according to the time intervals decided. After light curing the plastic tubes were removed carefully and the specimens were stored at 37°C and 100% humidity for 24 hours to encourage setting of MTA. The specimens were mounted in a universal testing machine (ADMET) and a crosshead speed of 0.5 mm/min was applied to each specimen by using a knife-edge blade until the bond between the MTA and RMGIC failed. The data were statistically analyzed using ANOVA, post hoc Tukey's t-test and Fisher's t-test and p-value ≤ 0.5 was considered significant. RESULTS: For both ProRoot MTA and MTA Angelus there was no statistically significant difference between 45 minutes and 24 hours (p-value ≥ 0.8). For ProRoot MTA, shear bond strength value at 10 minutes were significantly lower than 45 minutes and 24 hours group. However, for MTA Angelus, shear bond strength value at 10 minute was not significantly different from 45 minutes group (p-value ≥ 0.3). For both ProRoot MTA and MTA Angelus shear bond strength value at 0 minute were the least and were significantly lower than 10 minutes, 45 minutes, and 24 hours, respectively (p-value ≥ 0.000). CONCLUSION: Resin-modified glass ionomer cement can be layered over MTA Angelus after it is allowed to set for 10 minutes. However, ProRoot MTA should be allowed to set for at least 45 minutes before the placement of RMGIC to achieve better shear bond strength. CLINICAL SIGNIFICANCE: Due to the variety of types of mineral trioxide aggregate cements available in dentistry, it is justifiable to emphasize on different time intervals as it may affect the shear bond strength of restorative cements. Such information is pivotal for the clinicians while using mineral aggregate-based cements that receive forces from the condensation of restorative materials or occlusion, as the compressive strength may be affected due to different time intervals. How to cite this article: Tyagi N, Chaman C, Anand S, et al. Comparative Evaluation of Shear Bond Strength of Resin-modified Glass Ionomer Cement with ProRoot MTA and MTA Angelus. J Contemp Dent Pract 2024;25(1):35-40.

To Evaluate and Compare the Effect of Various Surface Treatment Modalities on Shear Bond Strength of Composite to Polyetherketoneketone and SEM Analysis: An In vitro Study.

Context: It is a challenge to bond resin materials with polyetherketoneketone (PEKK). To increase the bond strength, surface treatments using chemical adhesion, mechanical adhesion, or a combination of both can be used. Aims: The objective of the present study was to evaluate and compare the shear bond strength of PEKK to the composite resin after various surface treatments and to evaluate the fracture mode analyses. Materials and Methods: One hundred and twenty PEKK specimens were randomly divided into four groups (n = 30) after three different surface treatments (95% sulfuric acid etching, airborne abrasion with 110 µm aluminum-oxide, and 99% acetone). With the help of polytetrafluorethylene tube, resin composite (3M ESPE) was bonded on all the specimens, thermocycled, and subjected to shear bond strength testing. Thereafter, 15 samples from each group were assessed for fracture mode analyses using a scanning electron microscope. Statistical Analysis Used: Mean, Standard deviation, one-way analysis of variance (ANOVA) f-test, post hoc Tukey's test. Results: Statistical analysis using one-way ANOVA f-test revealed that the results were significant with a P < 0.05 with the maximum value obtained in the case of air abraded group and the minimum value obtained in the case of the untreated group. Adhesive failure mode was the most common among the air-abraded group. Conclusions: The mechanical surface treatment group (air abrasion) showed higher shear bond strength than the chemical surface treatment groups (sulfuric acid and acetone). The mixed-type fracture mode was most commonly noted in the air-abraded group.

Assessment of Occlusal Load Strength of Glass Ionomer Cement and Composite in Class V Cavities: An In-Vitro Study.

BACKGROUND:  Glass ionomer cement (GIC) is widely used in dentistry due to its chemical adhesion to dental tissues, biocompatibility, and anti-cariogenic potential but they have relatively weak mechanical properties. Resin composites have been widely regarded as the first choice for direct restorations but their polymerization shrinkage has remained a major problem. It has the potential to cause tooth debonding. The composite interface leads to postoperative sensitivity, secondary caries, enamel cracks, and microleakage. A restorative material's capacity to withstand occlusal stresses and support the remaining tooth structure depends on this property. Although class V restorations are predominantly done with GIC, this study was done to compare the strength of composite with the same. The GIC restore glass which is commonly used was tested against restofill composite. The main objective of conducting the study was to compare the compressive strength of the composite vs GIC in cervical cavities. So the aim of the study is to assess the occlusal load strength of GIC and composite in class V cavities using the universal testing machine. MATERIALS AND METHODS:  This study was employed as an in vitro study involving 20 natural central incisor teeth without any carious lesions. Class V cavity preparation was done and the selected teeth were divided into two groups of ten each. The cavities were filled with D Tech Restore GIC and composite restorations (restofill), respectively, polished, and then subjected to testing. An eccentric load was applied to the tooth structure using an Instron (Instron E3000 Electropuls, Instron, Norwood, United States) - Universal testing machine with a cross-head speed of 1mm per minute, and the stresses were further analyzed in the presence of an occlusal loading test using a stainless steel jig of 1mm diameter which led to the sectioning of the tooth buccolingually under the applied load. RESULTS:  An independent t-test was used to assess the results, and it was concluded that the results were statistically significant (p<0.05) at p=0.034. CONCLUSION:  Conclusively, the results suggested that the occlusal load strength of the composite is greater when compared to GIC.

An In vitro Assessment of the Shear Bond Strength of Two Different Pit and Fissure Sealants in Primary Teeth.

Aim: The current research had an aim to evaluate the shear bond strength of two different pit and fissure sealants in deciduous teeth. Materials and Methods: Forty deciduous teeth were part of this research. Inclusion criteria were teeth having an unbroken occlusal surface, whereas samples having developmental defects/afflicted with caries were subjected to exclusion from this research. Each specimen tooth was assigned at random to one of the two groups constituting 20 specimens each by means of a computer-generated randomization with two alphabets (A, B). Group 1: Conventional sealant, Group 2: Self-adhering flowable sealant. Following sealant coating, a shear load was placed via a universal testing apparatus in a manner parallel to the bonded edge at a speed of 0.5 millimeter/minute till the occurrence of a breakdown. Bond strength was subsequently measured in Mega Pascals (MPa). Results: 13.86 ± 0.23 was the mean shear bond strength of self-adhering flowable sealant versus 11.48 ± 0.52 Mpa of conventional sealants. Statistically significant differences amid both groups were noted. Conclusion: The current research arrived at a conclusion that self-adhering flowable sealants exhibited superior shear bond strength in comparison to conventional sealants.

Comparative Evaluation of Effect of Different Antioxidants on Shear Bond Strength of Composites on Bleached Enamel: An In Vitro Study.

Aim: To evaluate the effect of antioxidants on the shear bond strength of composite resin to bleached enamel. Materials and methods: A total of 120 extracted permanent anterior teeth were split into four major groups, one among them being a control group. Group I (bleaching + without antioxidant), group II (bleaching + 10% sodium ascorbate), group III (bleaching + 5% grape seed extract), and group IV (bleaching + 5% pine bark extract). All of the groups were bleached using a gel containing 35% carbamide peroxide, and then they were divided into two subgroups depending on when the bonding operation was to be completed-subgroup A was done in 24 hours, while subgroup B took 3 weeks. The universal testing machine was used to measure the shear bond strength. Results: Subgroup IA showed poor shear bond strength than other groups, there was no statistically significant difference between subgroup IB, IIA, and IVA. Subgroup IIIA showed the highest shear bond strength than the remaining groups. Between subgroups IIA and IIB, IIIA and IIIB, and IVA and IVB there was no statistically significant difference. This shows that delaying the bonding procedure for 3 weeks shows similar shear bond strength when compared to groups that were immediately bonded after antioxidant applying groups. Conclusion: All the antioxidants' immediate application could reverse compromised bond strength. Among them, 5% grape seed extract shows the highest increase in shear bond strength. How to cite this article: Maddula DC, Vasepalli M, Martha S, et al. Comparative Evaluation of Effect of Different Antioxidants on Shear Bond Strength of Composites on Bleached Enamel: An In Vitro Study. Int J Clin Pediatr Dent 2023;16(1):87-92.

The influence of Zirconia and Fiber posts with different lengths on Fracture strength of Maxillary Central Incisors restored with zirconia crowns - An in vitro study.

PURPOSE: Endodontically treated teeth are more susceptible to fractures than vital teeth because of significant coronal and radicular dentin loss during endodontic therapeutic procedures. The objective of this study was to estimate and compare the influence of length and post type on the fracture strength of endodontically treated maxillary central incisors. MATERIAL AND METHODS: In this in vitro study, sixty extracted human maxillary central incisors were decoronated 2 mm above the cemento-enamel junction.They were selected and subjected to standard endodontic treatment ,resulting in preparation with lengths of 5 mm (group 5mm),7,5 mm (group 7,5 mm) and 10 mm (group 10mm). Each group was randomly divided into 2 subgroups according to the post type , zirconia and fiber post. After appropriate surface treatment,they were cementet with resin adhesive cement and restored with zirconia crowns. Thermocycling (5 -55°C, 60 seconds, 1500 cycles) was performed after cementing the zirconia crowns on each tooth. Prepared samples were subjected to compresive static load of 0.5mm / min, at an angle of 130° to the long axis of the roots, using Universal Testing Machine (Matest ) at an cross head speed of 0.5 mm / min, until fracture.The significance of the results was assessed using 2-way ANOVA and the Tukey-Kramer test (α=0.05) Results:The ANOVA analysis indicated significant differences (P<0.05) between the groups. Tukey test revealed no significant difference among the zirconia posts of 5-mm length (26.5 N ±13.4) 7,5-mm length (25.2 N ±13.9), and 10-mm length (17.1 N ±5.2). Also, in the fiber post group, there was no significant difference when posts of 7.5-mm length (13.4 N ±11.0) were compared with the 5-mm (6.9 N ±4.6) and 10-mm (31.7 N ±13.1) groups. The 10-mm long post displayed superior fracture strength, and the 5mm-long post showed significantly lower mean values (P<0.001). CONCLUSION: The fracture strength of zirconia posts (5-mm and 7,5- mm length)was found to be significantly higher than those of fiber posts (5-mm and 7,5- mm length). The 10-mm long fiberpost group demonstrated significantly higher values of fracture strengths and the 5-mm long fiberpost group showed the lowest values for the force resulting in root fracture; these groups were significantly different from each other (P<.001).The fracture strength analysis with Universal Testing Machine is the only method that enables us to estimate the differences between zirconia and fiber posts with different lengths on endodontically treated teeth.

Comparative Evaluation of Compressive Strength of Self-cure, Dual-cure, and Light-cure Glass Ionomer Cements in a Simulated Oral Environment: An In Vitro Study.

Background: In primary dentition, glass ionomer cements (GICs) have unique benefits as a restorative material. Various types of GICs are available in the market. In pediatric dentistry, the choice of GI materials is generally focused on handling convenience with adequate consideration for mechanical qualities, including compressive strength to withstand occlusal stresses in the oral environment. Aim of the study: To evaluate the compressive strength of self-cure, dual-cure, and light-cure GI-based cements using a universal testing machine. Materials and methods: The study population comprised 30 cylindrical restorative blocks for compressive strength assessment. The restorative materials used for the studies were self-cure GIC (ChemFil Rock and GC Fuji IX GP Fast GIC), dual-cure GIC (Equia Forte and Ionolux GIC), and light-cure GIC (GC Fuji II LC and Ketac N 100 GIC). The cylindrical blocks were prepared using prefabricated Teflon mold measuring 4 mm diameter and 6 mm height from respective restorative materials and divided into three major groups and were subdivided into six groups comprising two materials in each group. Using an Instron universal testing machine, compressive strength was assessed. Data obtained were tabulated, and statistical analysis was done using Statistical Package for the Social Sciences (SPSS v22.0) software. Results: On individual comparison of GI-based types of cement, Ketac N100 GIC showed the highest compressive strength, and Fuji IX GP Fast GIC showed the least compressive strength. Conclusion: Light-cure GIC exhibited the highest compressive strength in comparison to dual-cure and self-cure GICs with regard to the nature of curing. How to cite this article: Chandru TP, Chandran S, Peedikayil FC, et al. Comparative Evaluation of Compressive Strength of Self-cure, Dual-cure, and Light-cure Glass Ionomer Cements in a Simulated Oral Environment: An In Vitro Study. Int J Clin Pediatr Dent 2023;16(5):707-710.

Mechanical Properties and Microstructural Evolution of TiNi-Based Intermetallic Alloy with Nb Addition.

TiNi intermetallic alloys were prepared with 2, 4 and 6 at.% niobium (Nb) addition. The mechanical properties and microstructures of the alloys were investigated under both static (1 × 10-1 to 1 × 10-3 s-1) and dynamic (4 × 103 to 6 × 103 s-1) loading conditions. The intermetallic alloy structures and surface morphologies of the alloys were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. In addition, the fracture morphologies were observed by optical microscopy (OM). It was shown that the addition of 2 to 4 at.% Nb increased the strength of the TiNi alloy. However, as the level of Nb addition was further increased to 6 at.%, a significant reduction in strength occurred. For a constant Nb addition, the plastic flow stress and strain rate sensitivity increased with increasing strain rate under both loading conditions (static and dynamic). The XRD and SEM results showed that the original surface morphologies were composed primarily of dendritic structures and fine ß-Nb + TiNi eutectic systems. Moreover, the OM results showed that the alloys underwent a transition from a brittle fracture mode to a ductile fracture mode as the level of Nb addition increased.

Comparative Evaluation of Frictional Resistance Between Different Types of Ceramic Brackets and Stainless Steel Brackets With Teflon-Coated Stainless Steel and Stainless Steel Archwires: An In-Vitro Study.

Background Orthodontic tooth movement relies on sliding mechanics usually achieved by sliding the archwire through brackets. Sliding causes friction which is a force resisting the relative motion of two contacting objects. Frictional resistance is undesirable in orthodontic tooth movement because the archwire might bind with the bracket and prevent tooth movement. In addition, friction causes bending of the archwire leading to unwanted tooth movement or space loss through anchorage interference, prolonging the treatment time and root resorption. This study was performed to compare the frictional resistance produced by different types of ceramic brackets and stainless steel brackets with Teflon-coated stainless steel and stainless steel archwires. The surface texture of the wire before and after friction test was also evaluated using a scanning electron microscope (SEM). Methodology A total of 48 samples were tested. In total, 12 premolar brackets each of stainless steel (Ortho technology, Carlsbad, CA, USA), monocrystalline ceramic (Ortho technology, Carlsbad, CA, USA), polycrystalline ceramic (Ortho technology, Carlsbad, CA, USA), and ceramic bracket with a metal slot (Ortho technology, Carlsbad, CA, USA) having an 0.022-inch slot were coupled with 0.019 × 0.025-inch stainless steel and Teflon-coated stainless steel wires. Each bracket-wire assembly was vertically mounted and clamped to the jaws of the universal testing machine. The wire was pulled across the bracket with a cross head speed of 10 mm per minute. The readings obtained were recorded. To evaluate the surface roughness, wires were examined using an SEM (in four magnifications 250×, 500×, 1,000×, and 5,000×) before and after testing. Results Under the testing conditions, the stainless steel bracket-stainless steel wire combination produced the least frictional resistance, and the polycrystalline ceramic bracket-stainless steel wire combination produced the highest frictional resistance. Ceramic brackets with a metal slot generated lesser friction than other types of ceramic brackets but more friction than stainless steel brackets. Moreover, for all bracket-archwire combinations, Teflon-coated wires generated reduced frictional resistance compared to stainless steel wires. The surface examination of Teflon-coated stainless steel wire and conventional uncoated stainless steel wire revealed that Teflon-coated wire had a smoother surface compared to uncoated stainless steel wire. Conclusions Within the limitations of this study, it was concluded that the stainless steel bracket produced the lowest frictional resistance and the polycrystalline ceramic bracket produced the highest frictional resistance. Ceramic brackets with a metal slot showed a coefficient of friction that was more than but comparable to that of stainless steel brackets. Monocrystalline ceramic brackets generated lesser friction compared to polycrystalline ceramic brackets. Further, Teflon coating of stainless steel archwires can reduce frictional resistance compared to conventional uncoated stainless steel archwires. The surface of Teflon-coated stainless steel wires was found to be smoother than uncoated stainless steel wires.

In Situ Micro-Observation of Surface Roughness and Fracture Mechanism in Metal Microforming of Thin Copper Sheets with Newly Developed Compact Testing Apparatus.

A better understanding of material deformation behaviours with changes in size is crucial to the design and operation of metal microforming processes. In order to facilitate the investigation of size effects, material deformation behaviours needed to be determined directly from material characterizations. This study was aimed at the design and manufacture of a compact universal testing machine (UTM) compatible with a 3D laser-confocal microscope to observe the deformation behaviour of materials in real-time. In this study, uniaxial micro tensile testing was conducted on three different thin (0.05 mm, 0.1 mm, and 0.3 mm) copper specimens with characteristic dimensions at micro scales. Micro tensile experimental runs were carried out on copper specimens with varying grain sizes on the newly developed apparatus under a 3D laser-confocal microscope. Microscale experiments under 3D laser-confocal microscope provided not only a method to observe the microstructure of materials, but also a novel way to observe the early stages of fracture mechanisms. From real-time examination using the newly developed compact testing apparatus, we discovered that fracture behaviour was mostly brought about by the concave surface formed by free surface roughening. Findings with high stability were discovered while moving with the sample grasped along the drive screw in the graphical plot of a crosshead's displacement against time. Our results also showed very low mechanical noise (detected during the displacement of the crosshead), which indicated that there were no additional effects on the machine, such as vibrations or shifts in speed that could influence performance. The engineering stress-strain plots of the pure copper-tests with various thicknesses or samples depicted a level of stress necessary to initiate plastic flowing inside the material. From these results, we observed that strength and ductility declined with decreasing thickness. The influence of thickness on fracture-strain, observed during tensile testing, made it clear that the elongation-at-break of the pure-copper foils intensely decreased with decreases in thickness. The relative average surface-roughness Ra was evaluated, which showed us that the surface-roughness escalated with the increasing trend of plasticity deformation (plastic strain) ε. For better understanding of the effects of plastic strain on surface roughness prior to material fractures, micro tensile tests were performed on the newly developed machine under a 3D laser-confocal-microscope. We observed that homogeneous surface roughness was caused by plastic strain, which further formed the concave surface that led to the fracture points. Finally, we concluded that surface roughness was one of the crucial factors influencing the fracture behaviour of metallic sheet-strips in metal microforming. We found that this type of testing apparatus could be designed and manufactured within a manageable budget.

Fracture Resistance of Primary Zirconia Crowns: An In Vitro Study.

In this study, we evaluated the fracture resistance of three commercially available prefabricated primary zirconia crowns and their correlation with dimensional variance. METHODS: a total of 42 zirconia crowns were selected from three companies, (1) NuSmile primary zirconia crowns, (2) Cheng Crowns zirconia, and (3) Sprig EZ crowns. The crowns were divided into two groups based on their location in the oral cavity and further divided into subgroups based on the brand. All of the samples were subjected to fracture tests using a universal testing machine. RESULTS: the mean load observed was highest with Cheng Crowns zirconia anterior crowns (1355 ± 484) and the least load was seen with Sprig EZ anterior crowns with a mean load of 339 ± 94. The mean load observed was highest with Cheng Crowns zirconia posterior crowns (1990 ± 485) followed by NuSmile posterior crowns and the least load was seen with Sprig EZ posterior crowns with a mean load of 661 ± 184. CONCLUSION: the Cheng crowns showed the highest fracture resistance amongst all three groups. Overall, the zirconia crowns (anterior and posterior) tested showed optimum mechanical properties to withstand the masticatory forces.

Experimental dataset for the macro-scale compression of Norway Spruce perpendicular to grain direction.

This article presents load and displacement data of Norway Spruce quasi-static compression test as well as video recordings of the experiment using the Universal Testing Machine (UTM). The specimens are 4 cm × 4 cm × 8 cm clear-wood cuboids with grain direction perpendicular to and loading direction parallel to the long axis. Due to the radially-arranged annual ring at such scale of the specimens, the plane of interest features significantly-varying orientation of the weak axes, namely the radial (R) and tangential (T) directions. A hemispherical knee joint underneath the specimen were fine-adjusted under preload before each experiment to ensure evenly-distributed load. Additionally, grids of 5 mm spacing were drawn on the plane of interest for better clarity of the deformed shape. Both load and displacement history recorded by the UTM as well as the deformation process recorded as video may provide valuable information for validation of wood material models or simulation methods with wood material implementations.

Effect of thermocycling on the flexural strength of two different composite filling materials: An in vitro study.

Flexural strength is the bend strength or stress which causes failure in bending of the material. Composite is the widely used restorative material in the era of esthetic dentistry as it provides better esthetic and mechanical support for both posterior and anterior teeth. The term "thermocycling" refers to the process of changing temperatures in the mouth. Thus, the aim of the study was to determine the effect of thermocycling on flexural strength in two different composite filling materials. Twelve samples of packable type composite filling material, among which four samples prepared were from Restofill l (Group 1) and four were prepared from Ivoclar Vivadent (Group 2) for the study. Bar-shaped composite resin specimens were prepared with dimensions of 2 mm × 2 mm × 25 mm. Then, the eight samples were subjected to a thermocycling process and four left as control. This was followed by the determination of maximum force by a universal testing machine, and then, the collected data were used to determine flexural strength using the formula. The determining flexural strength was analyzed using SPSS version 23.0 by Independent sample t-test. The mean flexural strength of thermocycled Restofill composite filling material is 6.73, whereas the nonthermocycled Restofill sample showed 5.58 and the mean flexural strength of thermocycled Ivoclar Vivadent composite filling material was 5.08. The difference was not statistically significant with P = 0.978 >0.05. The current study concludes that the flexural strength of the Restofill composite (Group 1) was higher than the Ivoclar composite (Group 2). Hence, thermocycling affects the flexural strength of composite resin.

Comparative evaluation of bioactivity, fluoride release, shear bond strength, and compressive strength of conventional glass ionomer cement incorporated with three inorganic bioactive nanoparticles: An experimental analysis.

Background: Over the course of four decades, the bioactive materials have changed. They have become more specialized, more manageable, possessing superior qualities. Thus, it should be encouraged to conduct ongoing research to improve these materials even further in order to meet the growing clinical and restorative needs. Aims and Objectives: To evaluate and compare bioactivity, fluoride release, shear bond strength and compressive strength of conventional GIC incorporated with three inorganic bioactive nanoparticles. Materials and Methods: For the study, total of 160 samples were included. The samples were divided in four groups (40 samples per group) i.e. 3 wt% of forsterite (Mg2SiO4) (Group 2), wollastonite (CaSiO3) (Group 3) and niobium pentoxide (Nb2O5) (Group 4) nanoparticles incorporated into GIC (Group 1). The bioactivity (FEG-SEM and EDX analysis), fluoride release (ion-selective electrode), shear bond strength testing (UTM followed by evaluation under stereomicroscope) and the compressive strength (UTM) was checked for each group. Results: Wollastonite nanoparticles (3wt %) incorporated to GIC showed maximum increase in the apatite crystal formation,Ca and P content and highest fluoride release. Mean shear bond strength was highest in niobium pentoxide nanoparticles (3wt %) incorporated to GIC while mean compressive strength was highest in forsterite nanoparticles (3wt %) added to GIC. Conclusion: Positive results were observed which showed increase in the bioactivity alongwith enhancement of the fluoride release, shear bond strength and compressive strength but further research on these materials is warranted before its use in clinical practice.

To Compare and Evaluate the Shear Bond Strength of Sixth- and Seventh-generation Bonding Agents.

Aim: To compare and evaluate the shear bond strength of sixth and seventh-generation dentin bonding agents. Materials and methods: Around 75 extracted permanent mandibular premolars were selected and assigned into two groups. The samples were cleaned, cavities were prepared, and the bonding agent was applied and stored in distilled water for 24 hours. Shear bond strength testing was done using a universal testing machine at the crosshead speed of 1 mm/minute. Data were analyzed statistically by one-way analysis of variance (ANOVA) and paired test. Results: The greatest mean shear bond strength to dentin was exhibited by the sixth-generation dentin bonding agent due to the solvent present, which has a low concentration and low hydrophilicity than the seventh-generation. Conclusion: Sixth-generation adhesives showed significantly higher mean shear bond strength to dentin than seventh-generation adhesives. Clinical significance: Bond strength values are gross assessing tools for evaluating the efficacy of restorative bonding materials to dentin. And as the shear bond strength is less technique sensitive to perform, it will highlight the strength at the bonded interface. How to cite this article: Adyanthaya BR, Gazal S, Mathur M, et al. To Compare and Evaluate the Shear Bond Strength of Sixth- and Seventh-generation Bonding Agents. Int J Clin Pediatr Dent 2022;15(5):525-528.

Relationship between the Depth of Penetration and Fracture Resistance of Various Sealers: A Comparative Study.

AIM: The aim of this in vitro study was to estimate the penetration depth and fracture resistance of three different sealers and to verify the relationship between the penetration depth and fracture resistance. MATERIALS AND METHODS: Sixty single-rooted teeth were selected and root canal preparation was done. After the instrumentation, the teeth were divided into three groups of 20 each. The groups were then obturated with gutta-percha (GP)-AH Plus sealer, Resilon-Real Seal, and propoint-bioceramic sealers, respectively. Ten teeth from each group were sectioned at three different regions (i.e., coronal, middle, and apical thirds of the root canal) and were viewed under a confocal microscope to determine the penetration depth of the sealer. The remaining samples were subjected to fracture resistance under a universal testing machine and the statistical analysis was done by using one-way ANOVA and post hoc Bonferroni tests. RESULTS: Propoint-bioceramic group showed the highest fracture resistance values followed by GP-AH Plus sealer and Resilon-Real seal groups with no significant difference noticed between them. Depth of penetration was greater for GP-AH Plus sealer, propoint-bioceramic, with no significant difference followed by the Resilon-Real seal group. CONCLUSION: The newer obturating material propoint-bioceramic group showed a greater fracture resistance. No correlation could be established between the depth of sealer penetration and fracture resistance. CLINICAL SIGNIFICANCE: Fracture resistance of tooth obturated with propoint-bioceramic sealer combination is significantly greater than GP-AH Plus and Resilon-Real seal combination, thereby showing propoint-bioceramic as a promising obturating material.

Comparative analysis of flexural strength of abraded and polished porcelain surfaces - an in vitro study.

Typically, prosthodontists adjust ceramic restorations glazed surface by grinding prior to insertion. Such alterations of surfaces are necessary for the correction of occlusal interferences. We aimed to evaluate and compare the change in flexural strength of ceramic surfaces after re-glazing and polishing. This study included 40 samples of ceramic blocks that were fabricated and glazed, and then fired in accordance with the manufacturer's recommendations. The sample was randomly divided into four groups of 10 samples each. The first group was the control group with unaltered glazed samples. The second group was abraded with an extra-fine diamond bur followed by re-glazing, and the other two groups were polished with two commercially available polishing kits after abrading them with an extra-fine diamond bur. The samples were tested for their flexural strength using a universal testing machine. On the application of the F test on the means of all the groups, a value greater than 0.05 was found, which meant that there is no statistically significant difference in flexural strength values between the groups (P-value>0.05). Since the flexural strength values of the polished group were comparable to the other groups, polishing can be used instead of re-glazing for ceramic restorations. This reduces an additional clinical appointment for the patient and saves working time.