Resin cements exhibited a greater reduction in the marginal discrepancy than the resin modified glass ionomer following luting in All ceramic complete veneer crowns. Hence resin cements are more preferable to GIC for luting All ceramic complete veneer crowns.

Context:Marginal discrepancy influenced by the choice of processing material used for the ceramic laminate veneers needs to be explored further for better clinical application.Aims:This study aimed to evaluate the amount of cervical and incisal marginal discrepancy associated with different ceramic laminate veneering materials.Settings and Design:This was an experimental, single-blinded, in vitro trial.Subjects and Methods:Ten central incisors were prepared for laminate veneers with 2 mm uniform reduction and heavy chamfer finish line. Ceramic laminate veneers fabricated over the prepared teeth using four different processing materials were categorized into four groups as Group I - aluminous porcelain veneers, Group II - lithium disilicate ceramic veneers, Group III - lithium disilicate-leucite-based veneers, Group IV - zirconia-based ceramic veneers. The cervical and incisal marginal discrepancy was measured using a scanning electron microscope.Statistical Analysis Used:ANOVA and post hoc Tukey honest significant difference (HSD) tests were used for statistical analysis.Results:The cervical and incisal marginal discrepancy for four groups was Group I - 114.6 ± 4.3 μm, 132.5 ± 6.5 μm, Group II - 86.1 ± 6.3 μm, 105.4 ± 5.3 μm, Group III - 71.4 ± 4.4 μm, 91.3 ± 4.7 μm, and Group IV - 123.1 ± 4.1 μm, 142.0 ± 5.4 μm. ANOVA and post hoc Tukey HSD tests observed a statistically significant difference between the four test specimens with regard to cervical marginal discrepancy. The cervical and incisal marginal discrepancy scored F = 243.408, P < 0.001 and F = 180.844, P < 0.001, respectively.Conclusion:This study concluded veneers fabricated using leucite reinforced lithium disilicate exhibited the least marginal discrepancy followed by lithium disilicate ceramic, aluminous porcelain, and zirconia-based ceramics. The marginal discrepancy was more in the incisal region than in the cervical region in all the groups.

Data showing the direct influence of substituents in the pyridine ring on the electron density at the azomethine function in 2- aminopyridine derivatives and their contrasting behaviour as compared to the aniline analogoues are presented. Results point out tautomeric equilibration and extended conjugation in title compounds.

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The kinetics and product analyses of the amine exchange reactions of two 2-aminopyridine derived Schiff-base ligands and their monomeric bischelate and dimeric copper(I1) complexes have been studied. The Schiff-base ligands investigated underwent m i n e exchange reactions with n-butyl, cyclohexyl, t-butyl amines. The coordination of the Schiff-base ligands to copper(I1) rendered the amine exchange reactions slower. With n-butyl and cyclohexyl amines, parallel first-and second-order terms on their concentrations are observed for the amine exchange reactions of copper(I1) bischelates and dimer. The kinetic data favor a mechanism involving a rate-limiting elimination of 2-aminopyridine from a diaminoacetal intermediate in preference to a scheme in which a dissociation of the complexes into free ligands and Cu(I1) may precede the amine exchange. The steric factors influence the amine exchange reactions of Cu(I1) bischelates with the bulkier amines reacting slower as given by the order t-butylamine (3.3 f 0.3 X dm3/mol.s) < cyclohexylamine (0.2 f 0.03 dm3/mol-s) < n-butylamine (2.2 f 0.2 dm3/mol.s). The bulkiness of the t-butyl group and the constraints imposed by the changes in the coordination geometry of Cu(I1) on amine exchange not only render the reactions of Cu(1I) bischelates slower but also make the formation of the mixed adduct ( [ N -(5-methyl) -2-pyridyl salicylaldimine] [ N -t -butyl salicylaldimine] Cu(I1)) more favored.

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