Correlation between clinical performance and degree of conversion of resin cements: a literature review

AbstractResin-based cements have been frequently employed in clinical practice to lute indirect restorations. However, there are numerous factors that may compromise the clinical performance of those cements. The aim of this literature review is to present and discuss some of the clinical factors that may affect the performance of current resin-based luting systems. Resin cements may have three different curing mechanisms: chemical curing, photo curing or a combination of both. Chemically cured systems are recommended to be used under opaque or thick restorations, due to the reduced access of the light. Photo-cured cements are mainly indicated for translucent veneers, due to the possibility of light transmission through the restoration. Dual-cured are more versatile systems and, theoretically, can be used in either situation, since the presence of both curing mechanisms might guarantee a high degree of conversion (DC) under every condition. However, it has been demonstrated that clinical procedures and characteristics of the materials may have many different implications in the DC of currently available resin cements, affecting their mechanical properties, bond strength to the substrate and the esthetic results of the restoration. Factors such as curing mechanism, choice of adhesive system, indirect restorative material and light-curing device may affect the degree of conversion of the cement and, therefore, have an effect on the clinical performance of resin-based cements. Specific measures are to be taken to ensure a higher DC of the luting system to be used

Influence of ceramic thickness and polymerization mode of a resin luting agent on early bond strength and durability with a lithium disilicate-based ceramic system

Statement of problem. Attenuation of polymerization light energy by translucent all ceramic materials may result in insufficient polymerization of underlying resin luting agents and inadequate early bond strength and durability. There is little information regarding the selection of in appropriate polymerization mode for cementing translucent all-ceramic restorations

An alternative method for fabricating a custom-made metal post with a ceramic core

The restoration of anterior non-vital teeth with metal posts and cores and all-ceramic restorations may lead to compromised esthetics because of the semitranslucence of ceramics and the metallic color of the underlying post and cores. This article presents a technique that combines the optical properties of ceramic cores with the mechanical properties of custom-made cast metal posts. The technique involves heat pressing of the core from leucite-enriched glass-ceramic to the underlying custom-made metal post and may provide additional esthetic benefit for anterior teeth especially with little remaining coronal dentin and with small root volume

Effect of tuf-coat on feldspathic porcelain materials

Ion exchange has been shown to increase the fracture strength of not only industrial glasses but also dental porcelains. Tuf-Coat, an ion exchange material, has been introduced as a simple method to strengthen dental porcelain restorations. Our experimental investigation aims to evaluate the effect of the ion exchange (Tuf-Coat) on the flexural strengths of specimens made with Vita VMK 68, Ceramco veneer, IPS and Matchmaker body porcelain. Eighty specimens were fabricated as discs 13 mm in diameter and 2 mm thick according to manufacturers' recommendations. Specimens were tested using a universal testing machine with a crosshead speed of 0.5 mm/min. by a method of biaxial flexural strength test. The results were evaluated using one-way variance analysis and 'Student's t' test to compare results at P < 0.05 level. Among the porcelains tested only Vita VMK 68 has been statistically affected by the ion exchange method Tuf-Coat

Energy calculations of quantum dot

We calculated the total energy of a semiconductor quantum dot formed in gate and etching defined devices. A 3D Poisson equation is solved self-consistently to obtain the electron density and potential profile. The total energies of electrons in the quantum dots with two different sizes are calculated with three different approximations by using the density and potential obtained from self-consistent procedure. In our calculation we used a recently developed energy functional called "orbital-free energy functional", Thomas-Fermi approximation and standard local-density approximation within density functional theory. The comparison of these methods reveals the efficacy of the used newly developed orbital-free energy functional which facilitates the calculation of Hartree integral for treatment of electron-electron interaction. (C) 2011 Elsevier B.V. All rights reserved

Understanding how consumers categorise nutritional labels: A consumer derived typology for front-of-pack nutrition labelling.

Significant ongoing debate exists amongst stakeholders as to the best front-of-pack labelling approach and emerging evidence suggests that the plethora of schemes may cause confusion for the consumer. To gain a better understanding of the relevant psychological phenomena and consumer perspectives surrounding FoP labelling schemes and their optimal development a Multiple Sort Procedure study involving free sorting of a range of nutritional labels presented on cards was performed in four countries (n=60). The underlying structure of the qualitative data generated was explored using Multiple Scalogram Analysis. Elicitation of categorisations from consumers has the potential to provide a very important perspective in this arena and results demonstrated that the amount of information contained within a nutrition label has high salience for consumers, as does the health utility of the label although a dichotomy exists in the affective evaluation of the labels containing varying degrees of information aggregation. Classification of exiting front-of-pack labelling systems on a proposed dimension of 'directiveness' leads to a better understanding of why some schemes may be more effective than others in particular situations or for particular consumers. Based on this research an enhanced hypothetical front-of-pack labelling scheme which combines both directive and non-directive elements is proposed