Megapascals Research Articles

The effect of repeated baking of porcelain on its bonding strength to a Co-Cr alloy 3D-printed by selective laser melting

ObjectivesThis study aimed to evaluate the effect of multiple baking cycles of porcelain on its shear bond strength to a cobalt-chromium (Co-Cr) alloy that is three-dimensionally printed using Selective Laser Melting (SLM) technique. Materials and methodsThe research sample comprised forty-eight discs measuring 5 mm × 3 mm, divided into four groups according to: the manufacturing method (SLM, casting) and the number of porcelain baking cycles (1, 3) as follows: Group A: Co-Cr alloy by SLM with one baking cycle; Group B: Co-Cr alloy by SLM with three baking cycles; Group C: Ni-Cr alloy by casting with one baking cycle; Group D: Ni-Cr alloy by casting with three baking cycles. Then, porcelain was melted on disks, shear testing was performed and the values of the Shear Bond Strength (SBS) in MegaPascals (MPa) were calculated. ResultsThe mean SBS values for each group were (A: 25.69 - B: 19.51 - C: 35.72 - D: 28.67 MPa). Statistical analysis showed that the manufacturing method and the number of porcelain baking cycles had a significant influence on shear bond durability (P > 0.05): the strength of this bond decreased when baking cycles increased. The Co-Cr samples manufactured by SLM also showed a decrease in binding strength compared to the Ni-Cr samples made by casting. ConclusionRepeated baking of porcelain reduces the strength of the porcelain bond with the Co-Cr alloy made by Selective Laser Melting (SLM) technique.

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.

Comparison of interfragmentary compression across simulated condylar fractures repaired using four techniques.

Equine condylar fractures are commonly repaired using cortex screws applied in lag fashion. Inadequate interfragmentary compression can lead to post-operative complications. Lateral condylar fractures were simulated in 21 cadaver limbs (8 third metatarsals, 13 third metacarpals). In each limb, pressure-sensitive film (Prescale®, Fuji Photo Film Co.) was placed in each osteotomy prior to repair with 4.5 mm diameter cortex screws placed in lag fashion. Screws were placed in linear (L), triangular (T), linear plus a washer (LW) and sequentially tightened triangular configurations (TD1). All screws were tightened to a torque of 4 Nm. Pressure prints obtained were scanned using dedicated software (Fuji FPD-8010E, Fuji Photo Film Co.). A Bayesian Network (BN) model was developed to investigate the impact and interrelationship of each factor on interfragmentary compression. Sixty-three repairs (20*L, 24* T, 11*TD1, and 8*LW) performed on 21 limbs were included in the analysis. The BN predicted mean contact area (±s.d.) for pressures within the operating range of the prescale film [≥2.5 Megapascals (MPa) ≤ 10 MPa] by L, T, TD1 and LW repairs were 403mm2 ± (140), 411 mm2 ± (120), 403 mm2 ± (120), and 366mm2 ± (70). The mean contact area (± s.d.) created by L, T, TD1 and LW repairs at pressures >10 MPa were 112 mm2 ± (48), 167 mm2 ± (67), 142 mm2 ± (50), and 100mm2 ± (27). When pressures ≥2.5 MPA to ≤10 MPa were considered, the construct (T or L), washer and screw tightening sequence variables had a very low effect on interfragmentary contact area. At pressures >10 MPa BN sensitivity findings were 16.3, 5.03, and 0.133% for construct, washer and screw tightening sequence. The BN model indicated that triangular repair configuration had a weak influence in the ≥2.5 MPa ≤ 10 MPa range and a moderate influence in the <10 MPa range, on interfragmentary compression. The addition of a washer and the screw tightening sequence had a weak influence on interfragmentary compression at all pressure ranges. The results show that triangular repairs create larger interfragmentary contact areas at greater interfragmentary pressure in simulated condylar fractures, however it is unknown if this results in improved repair stability in the clinical scenario.

Volumetric-acoustic study of Disodium Ethylenediaminetetraacetic acid with Propylene and Hexylene glycol at different temperatures

The present study shows the molecular interactions at constant pressure of 0.1 megapascals (MPa) and a range of temperatures from (288.15, 298.15, 308.15, 318.15 K) in aqueous solution of Disodium EDTA in (0.01, 0.02, 0.03) mol.kg-1 along with Propylene glycol and Hexylene glycol. Speed of sound and density data is determined using Anton Paar DSA 5000 M. Various thermo-acoustic parameters are calculated using the obtained data. Experimental density values determined apparent Molar Volume (Vϕ), Partial Molar Volume (Vϕ°) as well as Partial Molar Volume of Transfer (ΔVϕ°) along with Partial Molar Expansibility (Eϕ°) and thermal expansion coefficient (α). While speed of sound determined the Apparent Molar Isentropic Compression (Kϕ,S), Partial Molar Isentropic Compression (Kϕ,S°) as well as Partial Molar Isentropic Compression of Transfer (ΔKϕ.S°). Pair and Triplet Coefficients along with Empirical constants have also been estimated. FTIR spectroscopic research had been carried out in the binary mixture. From propylene through hexylene glycols, these factors provide data related to significant interactions between solute and solvent.

Investigation of Microstructure and Mechanical Properties of Layered Material Produced by Adding Al2O3 to 316L Stainless Steel

This study developed new advanced composite materials consisting of functional grading of 316L and Al2O3 specially designed for potential biomedical applications. Mechanical properties were characterized by tensile testing, and microstructural properties by optical microscope, scanning electron microscope (SEM), and Energy Dispersive X-Ray (EDX) analyses. The uniform mixture in the material, up to 40% by weight of Al2O3, is uniformly distributed in the 316L matrix that shows disintegration. Then, samples with 2, 3, 4, and 5 layers were produced in functionally graded 6, 7, 8, and 9 material types, respectively. The layer thicknesses were formed with an average of 900 µm. The results show that new composite materials can be produced functionally using 316L and Al2O3 in a layered manner. As a result of the mechanical experiments, it has been observed that the tensile strength of the layered composite structures remains within the range of 91–191 MPa, depending on the layer type. It has been observed that the elongation varies between 3.16 and 12.46%. According to these results, the materials obtained are considered suitable for use as an alternative prosthetic material in biomedical applications. The tensile strength, % elongation of the Composition 7, and yield strength of functionally graded (316 + (316L-10 Al2O3) + (316L-20 Al2O3) + (316L-30 Al2O3)) material are 123 megapascals (MPa), 7.3%, and 111MPa, respectively, and according to the literature, the mechanical strength of human bone is very close to this composition properties.

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

The current research had an aim to evaluate the shear bond strength of two different pit and fissure sealants in deciduous teeth. 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). 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. The current research arrived at a conclusion that self-adhering flowable sealants exhibited superior shear bond strength in comparison to conventional sealants.

The compressive strength and static biodegradation rate of chitosan-gelatin limestone-based carbonate hydroxyapatite composite scaffold

Background: One of the main components in tissue engineering is the scaffold, which may serve as a medium to support cell and tissue growth. Scaffolds must have good compressive strength and controlled biodegradability to show biological activities while treating bone defects. This study uses Chitosan-gelatin (C–G) with good flexibility and elasticity and high-strength carbonate hydroxyapatite (CHA), which may be the ideal scaffold for tissue engineering. Purpose: To analyze the compressive strength and static biodegradation rate within various ratios of C–G and CHA (C–G:CHA) scaffold as a requirement for bone tissue engineering. Methods: The scaffold is synthesized from C–G:CHA with three ratio variations, which are 40:60, 30:70, and 20:80 (weight for weight [w/w]), made with a freeze-drying method. The compressive strengths are then tested. The biodegradation rate is tested by soaking the scaffold in simulated body fluid for 1, 3, 7, 14, and 21 days. Data are analyzed with a one-way ANOVA parametric test. Results: The compressive strength of each ratio of C–G:CHA scaffold 40:60 (w/w), 30:70 (w/w), and 20:80 (w/w), consecutively, are 4.2 Megapascals (MPa), 3.3 MPa, 2.2 MPa, and there are no significant differences with the p= 0.069 (p&gt;0.05). The static biodegradation percentage after 21 days on each ratio variation of C–G:CHA scaffold 40:60 (w/w), 30:70 (w/w), and 20:80 (w/w) is 25.98%, 24.67%, and 20.64%. One-way ANOVA Welch test shows the result of the p-value as p&lt;0.05. Conclusion: The compressive strength and static biodegradation of the C–G:CHA scaffold with ratio variations of 40:60 (w/w), 30:70 (w/w), and 20:80(w/w) fulfilled the requirements as a scaffold for bone tissue engineering.

Impact of a High-Power Light-Emitting Diode Unit With Reduced Curing Times on the Shear Bond Strength of Orthodontic Brackets and Their Adhesive Remnant Index Scores.

This study aims to evaluate the curing time minimally required for bonding stainless-steel (SS) brackets using a high-power light-emitting diode (LED) light curing unit (LCU) and examine the debonded enamel surface for adhesive remnant. Based on the LED LCU and curing time employed, 80 human maxillary first premolar teeth were equally segregated into four groups. Three groups were cured using a high-power LED unit (Guilin Woodpecker Medical Instrument Co., Ltd., Guilin, Guangxi, China) for one, two, and three seconds. The fourth group served as a control and was bonded with another intensive LED unit (Elipar™ S10 LED Curing Light; 3M, Saint Paul, Minnesota, United States) for 20 seconds. Transbond™ XT Light Cure Adhesive (3M, United States) adhesive was used for bonding the SS brackets. All the samples were exposed to shear bond strength (SBS) testing after a 24-hour immersion period in distilled water at 37°C. A stereomicroscope was used to examine and score the adhesive remnant on the debonded surface using a modified adhesive remnant index (ARI). Kruskal-Wallis-ANOVA and post-hoc Mann-Whitney U tests for multiple pairwise comparisons were performed to analyze the data. Time and intensity significantly affected the SBS (P<0.001). A higher SBS value (16.04 megapascals (MPa)) was obtained in the six-second group when compared to the three-second (11.58 MPa), one-second (10.69 MPa), and 20-second control (13 MPa) groups. The ARI was significantly affected by the curing method. Higher SBSs were recorded for the six-second group using the high-power LED. A greater ARI score is associated with a reduced curing duration and vice versa.

In Vitro Analysis of Hydrophilic and Conventional sealants - A comparative study

Background: According to the World Health Organization, filling up the pits and fissures is one of the most efficient, least invasive ways to completely protect the occlusal surface from the carious phenomena. In vitro tests are essential for quickly delivering the knowledge required about the effectiveness of more recent sealant brands. Consequently, the objective of the current study was to assess and contrast the viscosity and length of resin tags on permanent molars of conventional and hydrophilic sealants. Materials and Methods: Twenty extracted third molars were split into two groups at random, one receiving conventional sealant (Clinpro 3M ESPE), and the other receiving hydrophilic sealant (UltraSeal XT Hydro). Each tooth's occlusal surfaces underwent an acid etchant pretreatment before the appropriate sealants were applied. Afterwards thermocycling and longitudinal sectioning were applied to both groups. For the purpose of measuring the length of the resin tag, the sectioned tooth specimens were examined under a scanning electron microscope. An Anton Paar viscometer was used to measure viscosities. The difference between the mean resin tag length of Group I and Group II sealants was compared using an independent t-test. Results: The mean resin tag length of Group II (10.07+/- 1.01m) was found to be higher than Group I (7.49+/- 0.94m), and this difference was statistically significant (P = 0.001). The viscosity measurements of Groups I and II were determined to be 0.8 mega Pascal (MPa) and 0.6 MPa, respectively. Conclusion: Based on the findings of the current investigation, it can be said that Group II sealants generated resin tags of sufficient length and had lower viscosities than Group I sealants. Thus, a hydrophilic sealant outperformed a conventional sealant in terms of performance.

Evaluation of stress distribution patterns produced with the Advansync2 class II corrector - A finite element analysis.

This study used finite element modeling to investigate stress distribution patterns during treatment with Advan Sync 2 Class II correctors. - A 3-D finite element model of the skull was constructed from images obtained from cone-beam computerized tomography images. Surface data of the AdvanSync2, brackets and archwires were derived and used to construct 3-D models. Stress distribution patterns and variations were assessed and quantified during appliance simulation and after advancement by 4mm using spacers, on the finite element model. Stress levels were recorded in Megapascals (MPa) and were visualized with a color scale. Maximum stress was evident in the mandible near the neck of condyle, anterior part of ramus and medial part of the coronoid process. Maxillary and mandibular teeth experienced negligible stress. Stress levels increased on advancing the appliance with spacers, though the regions and patterns of stress concentration in the maxilla and mandible remained constant to a great extent. The AdvanSync2 is an appropriate fixed functional appliance to correct Class II malocclusions with a retrognathic mandible, as it does not apply unnecessary and deleterious stresses on the maxillary and mandibular teeth.

Methods for Assessment of Early Age Shrinkage Cracks in Higher Strength Concrete: A Review

High-strength concrete is a type of concrete with compressive strength greater than 40 MPa (megapascals), which is much higher than the strength of normal concrete. High-strength concrete is often used in construction projects where greater strength is required, such as high-rise buildings, bridges, and other structures that need to withstand heavy loads or harsh environments. The high strength is achieved through the use of high-quality materials and careful proportioning and mixing of the concrete. Higher strength concrete experiences excessive early age cracking due to low water binder ratio. This early age shrinkage cracking directly affects the strength and durability of concrete. This paper discusses a review of methodologies used to assess the early age shrinkage cracks in concrete which will help in further high strength concrete shrinkage cracking study. In this review restrained shrinkage ring test, free shrinkage tests are discussed

Evaluation of the pattern of fracture formation from trauma to the human mandible with finite element analysis. Part 2: The corpus and the angle regions.

Although the mandible is the largest and strongest bone of the facial skeleton, it is frequently broken. The fracture location in the mandible depends on the biomechanical features, direction and angle of the trauma, and masticatory muscles. This study aimed to evaluate the stresses caused by trauma to the corpus and angle regions from different angles. After computer-based mandible models were created using finite element analysis, a force of 2000 Newton(N) was simulated with the mouth open or closed to the corpus and the angle. To the corpus: at 90° (Model 1) in the lateromedial direction, 45° (Model 2) in the lateromedial-inferosuperior direction, and 90° (Model 3) in the inferosuperior direction. To angle: 90° (Model 4) in the lateromedial direction and 45° (Model 5) in the lateromedial-inferosuperior direction. The resulting stress intensity was assessed using FEA. Following the simulated forces, the maximum stress in the mandible occurred in the condylar region, except in Model 3 (Left(L)Corpus2[36 megapascals(MPa)]) in the mouth-closed condition. After traumas in Model 1 (open-mouth: LCondyle2[547 MPa]) and Model 4 (closed-mouth: LCondyle2[607 MPa]), higher stress values occurred in the condyle. In the mouth open-closed state, there was no significant stress change in the condyle region in Model 1 (open-mouth: LCondyle2[547 MPa], closed-mouth:LCondyle2[546 MPa]) or in Model 2 (open mouth: Right(R)Condyle2[431 MPa], closed-mouth:LCondyle2[439 MPa]). In Model 3, lower stress values occurred in the closed-mouth rather than the open-mouth (LCondyle1[167 MPa]) state. In Models 4 and 5, the stress values increased in the mouth-closed condition compared with the mouth-open condition. Stress in the mandible is affected by the location of the trauma and the angle of incidence of the blow. In trauma to both the corpus and the angle, the most common area to be fractured is the condyle.

Different Designs of Deep Marginal Elevation and Its Influence on Fracture Resistance of Teeth with Monolith Zirconia Full-Contour Crowns.

Background and objectives: Even with the demand for high esthetics, the strength of the material for esthetic applications continues to be important. In this study, monolith zirconia (MZi) crowns fabricated using CAD/CAM were tested for fracture resistance (FR) in teeth with class II cavity designs with varying proximal depths, restored through a deep marginal elevation technique (DME). Materials and Methods: Forty premolars were randomly divided into four groups of ten teeth. In Group A, tooth preparation was conducted and MZi crowns were fabricated. In Group B, mesio-occluso-distal (MOD) cavities were prepared and restored with microhybrid composites before tooth preparation and the fabrication of MZi crowns. In Groups C and D, MOD cavities were prepared, differentiated by the depth of the gingival seat, 2 mm and 4 mm below the cemento-enamel junction (CEJ). Microhybrid composite resin was used for DME on the CEJ and for the restoration of the MOD cavities; beforehand, tooth preparations were conducted and MZi crowns were and cemented using resin cement. The maximum load to fracture (in newtons (N)) and FR (in megapascals (MPa)) were measured using the universal testing machine. Results: The average scores indicate a gradual decrease in the load required to fracture the samples from Groups A to D, with mean values of 3415.61 N, 2494.11 N, 2108.25 N and 1891.95 N, respectively. ANOVA revealed highly significant differences between the groups. Multiple group comparisons using the Tukey HSD post hoc test revealed that Group D had greater DME depths and showed significant differences compared with Group B. Conclusions: FR in teeth decreased when more tooth structure was involved, even with MZi crowns. However, DME up to 2 mm below the CEJ did not negatively influence the FR. Strengthening the DME-treated teeth with MZi crowns could be a reasonable clinical option, as the force required to fracture the samples far exceeded the maximum recorded biting force for posterior teeth.

Effects of Al2O3, SiO2 nanoparticles, and g-c3n4 nanosheets on biocement production from agricultural wastes

Environmental issues are brought up concerning the production of Portland cement. As a result, biocement serves as a reliable substitute for Portland cement in green construction projects. This study created a brand-new technique to create high-quality biocement from agricultural wastes. The technique is based on nanomaterials that improve and accelerate the "Microbially Induced Calcite Precipitation (MICP)" process, which improves the quality of the biocement produced. The mixture was further mixed with the addition of 5 mg/l of graphitic carbon nitride nanosheets (g-C3N4 NSs), alumina nanoparticles (Al2O3 NPs), or silica nanoparticles (SiO2 NPs). The cement: sand ratio was 1:3, the ash: cement ratio was 1:9, and water: cement ratio was 1:2. Cubes molds were prepared, and then cast and compacted. Subsequent de-molding, all specimens were cured in nutrient broth-urea (NBU) media until testing at 28 days. The medium was replenished at an interval of 7 days. The results show that the addition of 5 mg/l of g-C3N4 NSs with corncob ash delivered the highest “Compressive Strength” and the highest “Flexural Strength” of biocement mortar cubes of 18 and 7.6 megapascal (MPa), respectively; and an acceptable “Water Absorption” (5.42%) compared to all other treatments. This treatment delivered a “Compressive Strength”, “Flexural Strength”, and “Water Absorption” reduction of 1.67, 1.26, and 1.21 times the control (standard Portland cement). It was concluded that adding 5 mg/l of g-C3N4 NSs to the cementitious mixture enhances its properties, where the resulting biocement is a promising substitute for conventional Portland cement. Adding nanomaterials to cement reduces its permeability to ions, increasing its strength and durability. The use of these nanomaterials can enhance the performance of concrete infrastructures. The use of nanoparticles is an effective solution to reduce the environmental impact associated with concrete production.

Shear Bond Strength, Bonding Time and Adhesive Remnant Index of Adhesive Precoated Flash Free Adhesive System vs Conventional Adhesive System using Metal Brackets: An In-vitro Study

Introduction: With advances in materials for bonding in orthodontics, errors regarding amount of adhesive to be used can be controlled. Adhesive Precoated (APC™) Brackets were introduced to reduce the step of applying conventional adhesive on base of the bracket. Moreover, APC™ Flash Free Adhesive System (FFAS) eliminated the step of removal of excessive adhesive around the brackets. Aim: To compare Shear Bond Strength (SBS), Bonding Time (BT) and Adhesive Remnant Index (ARI) between Conventional Adhesive System (CAS) and APC™ FFAS using metal brackets Materials and Methods: This in-vitro study was carried out in the Department of Orthodontics and Dentofacial Orthopaedics at Bharati Vidyapeeth (Deemed to be University) Dental College and Hospital, Sangli, Maharashtra, India. A total of 78 teeth with metal braces were split into two groups, with 39 samples each receiving treatment with the CAS and the APCTM FFAS. Shear bond forces were applied to each sample using a universal testing machine and recorded in Megapascals (MPa) to provide an indication of SBS. Both Groups’ BT was quantified in terms of seconds. The stereomicroscope indexes of Artun J and Bergland S were used to determine ARI. Microsoft Excel was used for data entry, while Statistical Package for Social Sciences (SPSS) version 24.0 was used for analysis. The normality of the data was tested using two different t-tests. In terms of mean and standard deviation, descriptive statistics were represented. A significant level of 0.05 was used. Results: SBS values were 10.35±3.55 MPa and 11.23±3.82 MPa in CAS and FFAS respectively. No significant difference was found among the two groups (p≤0.29) in SBS. BT was significantly (p≤0.001) less in FFAS (95.54±8.72 seconds) compared to CAS (140.85±16.62 seconds). ARI was significantly (p≤0.002) less in FFAS (1.79±0.80) in comparison with CAS (1.23±0.74). Conclusion: FFAS brackets perform better in comparison to CAS in case of BT and ARI. Both groups show no significant difference in SBS.

Stress distribution in lower second molar mesialization using mini-implants: a pilot study using 3D finite element analysis

Objective: to analyze the stress distribution in a 3D model that simulates second molar mesialization using twodifferent types of mini-implants. Material and Methods: a mandible bone model was obtained by recomposinga computed tomography performed by a software program. The cortical and trabecular bone, a lower secondmolar, periodontal ligament, orthodontic tube, resin cement and the mini-implants were designed and modeledusing the Rhinoceros 4.0 software program. The characteristics of self-drilling orthodontic mini-implants were:one with 7 mm length, 1 mm transmucosal neck section and 1.6 mm diameter and another with 5 mm lengthand 1.5 mm diameter. A total of 235.161 and 224.505 elements were used for the mesh. These models wereinserted into the bone block and then subjected to loads of 200 cN (centinewton). The results were calculatedand analyzed by the Ansys 17.0 software program for qualitative verification through displacement and maximumprincipal stress maps. Results: it was possible to observe that the periodontal ligament presented low displacementand stress values. However, the physiological values presented are among those capable to provide orthodonticmovement, with compression and tensile area visualization staggered between 0.1 and -0.1 MPa (megapascal).Conclusion: within the limitations of the study, the mini-implants tested showed similar results where theload on the tooth allowed dental displacement (molar mesialization), with a tendency to rotate it, theoreticallyallowing the second molar to take the location of the first molar. KEYWORDSFinite element analysis; Orthodontic anchorage procedures; Fixed orthodontic appliances; Mini dental implants;Tooth dislocation.

Physio-Chemical and Biological Characterization of Novel HPC (Hydroxypropylcellulose):HAP (Hydroxyapatite):PLA (Poly Lactic Acid) Electrospun Nanofibers as Implantable Material for Bone Regenerative Application

The research on extracellular matrix (ECM) is new and developing area that covers cell proliferation and differentiation and ensures improved cell viability for different biomedical applications. Extracellular matrix not only maintains biological functions but also exhibits properties such as tuned or natural material degradation within a given time period, active cell binding and cellular uptake for tissue engineering applications. The principal objective of this study is classified into two categories. The first phase is optimization of various electrospinning parameters with different concentrations of HAP-HPC/PLA(hydroxyapatite-hydroxypropylcellulose/poly lactic acid). The second phase is in vitro biological evaluation of the optimized mat using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay for bone regeneration applications. Conductivity and dielectric constant were optimized for the production of thin fiber and bead free nanofibrous mat. With this optimization, the mechanical strength of all compositions was found to be enhanced, of which the ratio of 70:30 hit a maximum of 9.53 MPa (megapascal). Cytotoxicity analysis was completed for all the compositions on MG63 cell lines for various durations and showed maximum cell viability on 70:30 composition for more than 48 hrs. Hence, this investigation concludes that the optimized nanofibrous mat can be deployed as an ideal material for bone regenerative applications. In vivo study confirms the HAP-HPC-PLA sample shows more cells and bone formation at 8 weeks than 4 weeks.

Universal adhesives applied to deep dentin with different bonding treatments.

To determine the bonding characteristics of universal adhesives applied to the deep pulp wall with different strategies, by means of shear bond strength and laser microscopy. Cavities 4 mm deep and maximum width were carved in 36 extracted molars. Nine groups were formed according to dental substrate treatment and adhesives, as follows: Total-etch: group 1-Monobond 7 self-etch, group 2-One coat 7 universal, and group 3-Single bond universal; Adamantine etch: group 4-Monobond 7 self-etch, group 5-One coat 7 universal, and group 6-Single bond universal; Self-conditioning: group 7-Monobond 7 self-etch, group 8-One coat 7 universal, and group 9-Single bond universal. Molars were filled following the manufacturer's instructions. Three specimens per group (27 altogether) were used to determine shear bond strength using a universal testing machine, while layer thicknesses were measured on the remaining specimens using microscope images and Olympus LEXT 3D Software. Analysis of variance was used to compare data. Mean (standard deviation) bond strength in megapascals (MPa) was: group 1: 7.06±3.01; group 2: 10.74±4.36; group 3: 8.20±3.92; group 4: 7.41±2.23; group 5: 6.84±1.50; group 6: 5.86±2.10; group 7: 5.83±1.94; group 8: 7.14±2.37; group 9: 8.06±3.51. Bond strength was higher (p=0.049) for total-etch (8.61±3.96) than for selective etch (6.71±1.98) and self-conditioning (6.91±2.68). No significant difference was found among the three adhesives (p=0.205). Adhesive layer in micrometers (μm) was total-etch 8.71±4.93, selective etch 5.49±1.70 and self-conditioning 6.27±3.01, with no significant difference. There were significant differences among bonding strategies, with the highest values for total-etch. No significant difference was observed between self-conditioning and selective etch. No significant difference was found among the adhesives, which all behaved similarly. The greatest adhesive layer thicknesses were recorded in the total-etch group, with no significant difference among the various adhesive approaches.

Structure-mechanical analysis of various fixation constructs for basicervical fractures of the proximal femur and clinical implications; finite element analysis

ObjectiveThis present study was conducted to determine the structural-mechanical stability of various fixation constructs through finite element (FE) analysis following simulation of a basicervical fracture and to introduce the clinical implications. Materials and MethodsWe simulated fracture models by using a right synthetic femur (SAWBONES®). We imported the implant models into ANSYS® for placement in an optimal position. Five assembly models were constructed: (1) multiple cancellous screws (MCS), (2) FNS (femoral neck system®), (3) dynamic hip screw (DHS), (4) DHS with anti-rotation 7.0 screw (DHS + screw), and PFNA-II (Proximal Femoral Nail Antirotation-II®). The femur model's distal end was completely fixed and 7° abducted. We set the force vector at a 3° angle laterally and 15° posteriorly from the vertical ground. Analysis was done using Ansys® software with von Mises stress (VMS) in megapascals (MPa) and displacement (mm) ResultsThe displacements of the proximal femur were 10.25 mm for MCS, 9.66 mm for DHS, 9.44 mm for DHS + screw, 9.86 mm for FNS, and 9.31 mm for PFNA-II. The maximum implant VMS was 148.94 MPa for MCS, 414.66 MPa for DHS, 385.59 MPa for DSH + screw, 464.07 MPa for FNS, and 505.07 MPa for PFNA-II. The maximum VMS at the fracture site was 621.13 MPa for MCS, 464.14 MPa for DHS, 64.51 MPa for DHS + screw, 344.54 MPa for FNS, and 647.49 MPa for PFNA-II. The maximum VMS at the fracture site was in the superior area with the high point around the posterior screw in the MCS, anterosuperior corner in the DHS, the posteroinferior site of the FNS, and posterosuperior site around the entry point in the PFNA-II. In the DHS + screw, the stresses were distributed evenly and disappeared at the maximum VMS fracture site. ConclusionBased on the fracture site and implant's stress distribution, the model receiving the optimal load was a DHS + screw construct, and the FNS implant could be applied to anatomically reduced fractures without comminution. Considering the high-stress concentration around the entry point, a PFNA-II fixation has a high probability of head-neck fragment rotational instability.

Comparative Evaluation of Microtensile Bond Strength in Three Different Dentin Luting Agents: An In vitro Study.

Long-term clinical success on indirect restorations is largely determined by bonding efficiency of the luting agent, with adhesion to dentin being the main challenge. Therefore, aim of this study was to assess the microtensile bond strength when using flowable resin composite, preheated resin composite and dual self-adhesive resin cement as dentin luting agents. Occlusal thirds of molar teeth were cut and randomly divided into 3 groups to be cemented: RelyX™U200, Filtek™ Z250 XT- preheated to 70° and Filtek Flow™ Z350XT. They were then thermocycled 5000 times between 5+/-2°C and 55+/-2°C. Subsequently, 10 microbars per group were prepared. The 30 samples were placed in saline solution for 24 hours at room temperature prior to microtensile test. This was performed with a digital universal testing machine at a crosshead speed of 0.5 mm/min. The bond strength values obtained were analyzed in Megapascals (MPa). Measures of central tendency such mean and measures of dispersion such standard deviation were used. In addition, the Kruskall Wallis non-parametric test with Bonferroni post hoc test was applied, considering a significance value of 5% (P < 0.05), with type I error. The dentin microtensile bond strengths of preheated resin composite, flowable resin composite and dual self-adhesive cement were 6.08 ± 0.66 Mpa, 5.25 ± 2.60Mpa and 2.82 ± 1.26Mpa, respectively. In addition, the preheated resin composite exhibited significantly higher microtensile bond strength compared to the dual self-adhesive cement (P < 0.001). While the flowable resin composite showed no significant difference with the dual self-adhesive cement (P = 0.054) and the preheated resin composite (P = 0.329). The microtensile bond strength in dentin was significantly higher when using a preheated resin composite at 70°C as a luting agent compared to dual self-adhesive cement. However, the preheated resin composite showed similar microtensile bond strength compared to the flowable resin composite.