• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.289-299
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• 2002

The bond strength is one of the most important factor in establishing long-term success of esthetic restorative dentistry. So, various restorative materials have been introduced to improve the esthetic and physical properties. Ormocer (organically modified ceramic) was developed as a result of such efforts. This study was performed to compare the shear bond strength of ormocer based adhesive with that of existing dentin adhesive. In this study $Admira^{(R)}$ and $Admira^{(R)}$ bond of the ormocer system are grouped together for ADM, Single $Bond^{(R)}$ which is an one-bottle adhesive and Z-250TM which is hybrid composite resin of BIS-GMA system for SIN, and $Definite^{(R)}$ of ormocer and Etch & $Prime^{(R)}$ 3.0 which is a self etching priming/ bonding agent for ETC. The results of this study were as follows. : (1) In the comparison of shear bond strength according to different adhesive system, shear bond strength was increased in the order of ETC group, SIN group, ADM group. There was no significant difference between ADM group and SIN group. However, there was a significant level of difference between ADM and ETC groups as well as SIN and ETC groups( p<0.05). (2) Examination by a scanning electron microscope showed a well established hybrid layer and resin tag in both ADM group and SIN group, while ETC group showed a minimal formation of the hybrid layer when compared with ADM and SIN groups. From the above results, it may be reasonable to start the clinical application of ormocer system, and it is recommended that ormocer system should be used along with an ormocer based adhesive because ormocer system showed the lower shear bond strength when it used with other existing self etching priming/bonding agent. The self etching priming/bonding agent showed relatively low shear bond strength, and it is considered that the further study should be needed.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2861-2866
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• 2012

Results of the comparisons of various density functional theory (DFT) methods with different basis sets for predicting the molecular geometry of TPOP24N-Oxide macrocycle, an oxoporphyrin N-oxide, are reported in this paper. DFT methods, including M06-2X, B3LYP, LSDA, B3PW91, PBEPBE, and BPV86, are examined. Different basis sets, such as 6-$31G^*$, 6-31+G (d, p), 6-311+G (d, p), and 6-311++G (d, p), are also considered. The M06-2X/6-$31G^*$ level is superior to all other density functional methods used in predicting the geometry of TPOP24N-Oxide. The geometries of regioisomeric chlorin N-oxide and oxoporphyrin N-oxide are reported using M06-2X/6-$31G^*$ method. The geometry effects of oxoporphyrin and chlorin N-oxide regioisomers are increased ${\beta}-{\beta}$ bond lengths by N-oxidation because the bond overlap index due to charge transfers is decreased. In N-oxidation ring (II, III), angles that include ${\beta}-{\beta}$ bond length increase as the bond overlap index of ${\beta}-{\beta}$ bond is decreased by N-oxidation. The potential energy surfaces of chlorin N-oxide and oxoporphyrin N-oxide are explored by M06-2X/6-$31G^*$, and single-point calculations are performed at levels up to M06-2X/6-311++G (d, p). Total and relative energies are then calculated. The results indicate that chlorin 24 N-oxides are more stable than chlorin 22 N-oxides in chlorin N-oxide regioisomers. Moreover, TPOP24N-Oxide is less stable than TPOP22N-Oxide.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1641-1647
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• 2006

Vibrational relaxation and competitive C-$H_{methyl}$ and C-$H_{ring}$ bond dissociations in vibrationally excited methylpyrazine in the collision with HF have been studied by use of classical trajectory procedures. The energy lost by the vibrationally excited methylpyrazine upon collision is not large and it increases slowly with increasing total vibrational energy content between 20,000 and 45,000 $cm^{-1}$. Above the energy content of 45,000 $cm^{-1}$, however, energy loss decreases. The temperature dependence of energy loss is negligible between 200 and 400 K, but above 45,000 $cm^{-1}$ the energy loss increases as the temperature is raised. Energy transfer to or from the excited methyl C-H bond occurs in strong collisions with HF, that is, relatively large amount of translational energy is transferred in a single step. On the other hand, energy transfer to the ring C-H bond occurs in a series of small steps. When the total energy content ET of methylpyrazine is sufficiently high, either or both C-H bonds can dissociate. The C-$H_{methyl}$ dissociation probability is higher than the C-$H_{ring}$ dissociation probability. The dissociation of the ring C-H bond is not the result of the direct intermolecular energy flow from the direct collision between the ring C-H and HF but the result of the intramolecular flow of energy from the methyl group to the ring C-H stretch.

• Restorative Dentistry and Endodontics
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• v.26 no.2
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• pp.153-161
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• 2001

The purpose of this study was to evaluate microleakage of six current dentin bonding systems. In this in vitro study, class V cavities were prepared on buccal and lingual surfaces of thirty extracted human molars. Each margin was on enamel and dentin/cementum. Experimental teeth were randomly divided into six groups of 5 each. Group 1 : Scotchbond Multi-Purpose; Group 2 : Single Bond; Group 3 : Prime&Bond NT ; Group 4 : Clearfil Liner Bond 2 ; Group 5 : MAC Bond II ; Group 6 : One-up Bond F. The bonding agent and composite resin were applied to class V cavities according to manufacturer's directions. After thermocycling, the specimens were immersed in 0.5% basic fuchsin dye solution for 6 hours and sectioned longitudinally through the center of the restoration with a low speed diamond saw. The degree of microleakage was measured as the extent of dye penetration under the stereomicroscope at $\times$20. The data were analyzed using one way ANOVA. When significant differences found. multiple comparisons were made using Duncan's Multiple Range Test. The results of this study were as follows: 1. In all groups, leakage value seen at the enamel margin was significantly lower than that seen at the dentin margin(P<0.001). 2. At the enamel margin, none of the dentin bonding systems used in this study showed statistically significant difference in leakage values(P<0.05). 3. At the cementum margin, group 3 showed the highest leakage value, and others were decreased as group 5, 6, 4 in that order, and group 1, 2 showed the lowest leakage value. There was statistically significant difference between group 3 and the other groups except for group 5(P<0.05).

• Restorative Dentistry and Endodontics
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• v.44 no.2
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• pp.13.1-13.9
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• 2019

Objectives: This study evaluated the effect of dentin pretreatment with silver nanoparticles (SNPs) and chlorhexidine (CHX) on the microshear bond strength (${\mu}SBS$) durability of different adhesives to dentin. Materials and Methods: Occlusal surfaces of 120 human molars were ground to expose flat dentin surfaces. The specimens were randomly assigned to six groups (n = 20). Three groups (A, B, and C) were bonded with Adper Single Bond 2 (SB) and the other groups (D, E, and F) were bonded with Clearfil SE Bond (SEB). Dentin was pretreated with CHX in groups B and E, and with SNPs in groups C and F. The specimens were restored with Z250 composite. Half of the bonded surfaces in each group underwent ${\mu}SBS$ testing after 24 hours and the other half was tested after 6 months of water storage. Results: SNP application was associated with a higher ${\mu}SBS$ than was observed in the CHX and control groups for SEB after 24 hours (p < 0.05). A significantly lower ${\mu}SBS$ was observed when no dentin pretreatment was applied compared to dentin pretreatment with CHX and SNPs for SB after 24 hours (p < 0.05). The ${\mu}SBS$ values of the 6-month specimens were significantly lower than those obtained from the 24-hour specimens for all groups (p < 0.05). This decrease was much more pronounced when both adhesives were used without any dentin pretreatment (p < 0.05). Conclusions: SNPs and CHX reduced the degradation of resin-dentin bonds over a 6-month period for both adhesive systems.

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.95-104
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• 2019

PURPOSE. To evaluate the effect of surface treatments and repair materials on the shear bond strength and to measure the fracture toughness of CAD/CAM provisional restoration materials. MATERIALS AND METHODS. Four CAD/CAM (3D printing: Nextdent C&B and ZMD-1000B Temporary, CAD/CAM resin block: Yamahachi PMMA disk and Huge PMMA block) and four conventional (monometacrylate: Jet and Alike, dimetacrylate: Luxatemp and Protemp 4) materials were selected to fabricate disk-shaped specimens and divided into six groups according to surface treatment (n=10). CAD/CAM materials were repaired with Jet or Luxatemp, while conventional materials were repaired with their own materials. The shear bond strength was measured by using universal testing machine. Ten rectangular column-shaped specimens for each material were fabricated to measure the fracture toughness by single edge v notched beam technique. Statistical analysis was performed by one-way ANOVA. RESULTS. The highest shear bond strength of CAD/CAM materials was achieved by SiC paper + sandblasting. It was also accomplished when repairing 3D printing materials with Luxatemp, and repairing CAD/CAM resin blocks with Jet. Yamahachi PMMA disk showed the highest fracture toughness. Nextdent C&B showed the lowest fracture toughness value but no statistically significant difference from Alike and Luxatemp (P>.05). CONCLUSION. In order to successfully repair the CAD/CAM provisional restoration, mechanical surface treatment and appropriate repair material according to the CAD/CAM material type should be selected. The CAD/CAM provisional materials have proper mechanical properties for clinical use as compared to conventional materials.

• Restorative Dentistry and Endodontics
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• v.46 no.4
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• pp.59.1-59.14
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• 2021

Objectives: This study compared the Biodentine, MTA Repair HP, and Bio-C Repair bioceramics in terms of bond strength to dentin, failure mode, and compression. Materials and Methods: Fifty-four slices obtained from the cervical third of 18 single-rooted human mandibular premolars were randomly distributed (n = 18). After insertion of the bioceramic materials, the push-out test was performed. The failure mode was analyzed using stereomicroscopy. Another set of cylindrically-shaped bioceramic samples (n = 10) was prepared for compressive strength testing. The normality of data distribution was analyzed using the Shapiro-Wilk test. The Kruskal-Wallis and Friedman tests were used for the push-out test data, while compressive strength was analyzed with analysis of variance and the Tukey test, considering a significance level of 0.05. Results: Biodentine presented a higher median bond strength value (14.79 MPa) than MTA Repair HP (8.84 MPa) and Bio-C Repair (3.48 MPa), with a significant difference only between Biodentine and Bio-C Repair. In the Biodentine group, the most frequent failure mode was mixed (61%), while in the MTA Repair HP and Bio-C Repair groups, it was adhesive (94% and 72%, respectively). Biodentine showed greater resistance to compression (29.59 ± 8.47 MPa) than MTA Repair HP (18.68 ± 7.40 MPa) and Bio-C Repair (19.96 ± 3.96 MPa) (p < 0.05). Conclusions: Biodentine showed greater compressive strength than MTA Repair HP and Bio-C Repair, and greater bond strength than Bio-C Repair. The most frequent failure mode of Biodentine was mixed, while that of MTA Repair HP and Bio-C Repair was adhesive.

• Steel and Composite Structures
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• v.51 no.5
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• pp.509-527
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• 2024

Bonding carbon fiber-reinforced polymer (CFRP) laminates have been extensively employed in the restoration of steel constructions. In addition to the mechanical properties of the CFRP, the bond strength (P_U) between the CFRP and steel is often important in the eventual strengthened performance. Nonetheless, the bond behavior of the CFRP-steel (CS) interface is exceedingly complicated, with multiple failure causes, giving the P_U challenging to forecast, and the CFRP-enhanced steel structure is unsteady. In just this case, appropriate methods were established by hybridized Random Forests (RF) and support vector regression (SVR) approaches on assembled CS single-shear experiment data to foresee the P_U of CS, in which a recently established optimization algorithm named Aquila optimizer (AO) was used to tune the RF and SVR hyperparameters. In summary, the practical novelty of the article lies in its development of a reliable and efficient method for predicting bond strength at the CS interface, which has significant implications for structural rehabilitation, design optimization, risk mitigation, cost savings, and decision support in engineering practice. Moreover, the Fourier Amplitude Sensitivity Test was performed to depict each parameter's impact on the target. The order of parameter importance was t_c> L_c > E_A > t_A > E_c > b_c > f_c > f_A from largest to smallest by 0.9345 > 0.8562 > 0.79354 > 0.7289 > 0.6531 > 0.5718 > 0.4307 > 0.3657. In three training, testing, and all data phases, the superiority of AO - RF with respect to AO - SVR and MARS was obvious. In the training stage, the values of R² and VAF were slightly similar with a tiny superiority of AO - RF compared to AO - SVR with R² equal to 0.9977 and VAF equal to 99.772, but large differences with results of MARS.

• Computers and Concrete
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• v.19 no.6
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• pp.641-649
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• 2017

The discovery of the Interfacial Transition Zone (ITZ) by Farran in 1956 initiated a new era in the study of the behaviour of concrete. Acknowledged as the weak link, this ITZ was studied extensively, numerically as well as experimentally. While the complementary experimental tests illustrated the visual behaviour of this specimen under increasing monotonic compression loading, a perfect bond within the ITZ has also been studied by using finite element analysis for comparison purposes. Finite element analysis was used to evaluate the degree of correctness and precision of the proposed ITZ model. This paper discusses the use of the cutoff bar in finite element modeling, representing the ITZ of a single aggregate (inclusion) in a mortar matrix. Experiments were conducted to investigate the influence of the ITZ model on the single inclusion specimen's strength. The model was tested for some inclusions that varied in dimension and shape. The effect of inclusion shape on the stress concentrations of the specimens was examined. The aim of this research work is to propose a simple yet accurate ITZ model to be used in the commercially available finite element software packages.

• Journal of Integrative Natural Science
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• v.8 no.3
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• pp.192-203
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• 2015

In view of the growing medicinal importance of pyrazole and its derivatives, the single crystal X-ray diffraction study was carried out for the potential active 2-Benzyl-3-[3-(4-bromo-phenyl)-1-phenyl-1H-pyrazol-4yl]-4,6-dioxo-5-phenyl-octahydro-pyrrolo[3,4-C]pyrrole-1-carboxylic acid ethyl ester ($C_{37}H_{31}BrN_4O_4$, H2O). In the title compound are two molecules exist in the asymmetric unit. It crystallizes in the monoclinic space group $P{\hat{i}}$ with unit cell dimension $a=13.361(18){\AA}$, $b=13.424(17){\AA}$ and $c=21.649(2){\AA}$ [${\alpha}=80.745(9)^{\circ}$, ${\beta}=79.770(10)^{\circ}$ and ${\gamma}=60.788(6)^{\circ}$]. The pyrazole ring adopts planar conformation. The sum of the bond angles at nitrogen atom of the pyrazole ring indicates the $Sp^2$ hybridized state. The crystal structure is stabilized by intramolecular C-H...O hydrogen bond interaction.