Influence of Storage Media on Color Stability of Different Resin Composites as Determined by \u394E and \u394E00

Objective: To evaluate the color stability of 3 different resin composites when exposed to storage in water, air or artificial saliva. Materials and Methods: Initial color of 81 specimens was assessed by a calibrated reflectance spectrophotometer over a black as well as a white background. Specifically, 9 disc shaped specimens made out of 3 resin composite materials were kept in distilled water, air and artificial saliva (Glandosane) at 37\ub0C. After a storage period of 4 weeks, spectrophotometric measurements were repeated and the color changes calculated by means of \u394E and \u394E00. Results: When analysed over a white background, median \u394E values varied from 0.6 (Filtek Supreme Dentin/water) to 7.1 (Filtek Supreme Enamel/Glandosane). When analysed over a black background median \u394E values varied from 0.4 (Filtek Supreme Dentin/water) to 5.0 (Filtek Supreme Enamel/Glandosane). When analysed over a white background, median \u394E00 values varied from 0.4 (Filtek Supreme Dentin/water) to 4.6 (Filtek Supreme Enamel/Glandosane). When analysed over a black background median \u394E00 values varied from 0.4 (Filtek Supreme Dentin/water) to 4.6 (Filtek Supreme Enamel/Glandosane). Statistical analysis performed by means of ANOVA and Fisher\u2019s LSD post hoc tests showed differences between groups. The correlation between \u394E and \u394E00 was 99.09% and 99.65% over black and white background, respectively. Conclusion: Within the limits of the present study, storage media significantly influenced color stability of resin composites

Influence of background on natural tooth colour coordinates: an in vivo evaluation

The aim of this study was to evaluate the influence of different backgrounds on spectrophotometric colour values of natural teeth. Twenty volunteers (10 males and 10 females) with a mean age of 25years and 9months (±3years and 2months) were each subjected to 4 spectrophotometric measurements of their upper right central incisor. Each sample was measured with alternatively black, 50% grey, white or no background (positive control). ΔE medians ranged from 0.9 to 5.9. All artificial backgrounds presented significant differences (p0.05). If an artificial background needs to be used, as for example when performing in vitro studies, preference should be given to a black background as it approaches best the clinical situation (i.e. no background). Even if no statistically significant differences were found when compared with the grey background, the black background should be preferred due to its lower ΔE medians, standard deviation as well as lower minimum and maximum values

Effect of hydraulic retention time on the electro-bioremediation of nitrate in saline groundwater

Bioelectrochemical systems (BES) have proven their capability to treat nitrate-contaminated saline groundwater and simultaneously recover value-added chemicals (such as disinfection products) within a circular economy-based approach. In this study, the effect of the hydraulic retention time (HRT) on nitrate and salinity removal, as well as on free chlorine production, was investigated in a 3-compartment BES working in galvanostatic mode with the perspective of process intensification and future scale-up. Reducing the HRT from 30.1 +/- 2.3 to 2.4 +/- 0.2 h led to a corresponding increase in nitrate removal rates (from 17 +/- 1 up to 131 +/- 1 mgNO3--N L-1d-1), although a progressive decrease in desalination efficiency (from 77 +/- 13 to 12 +/- 2 %) was observed. Nitrate concentration and salinity close to threshold limits indicated by the World Health Organization for drinking water, as well as significant chlorine production were achieved with an HRT of 4.9 +/- 0.4 h. At such HRT, specific energy consumption was low (6.8 center dot 10-2 +/- 0.3 center dot 10-2 kWh g-1NO3--Nremoved), considering that the supplied energy supports three processes simultaneously. A logarithmic equation correlated well with nitrate removal rates at the applied HRTs and may be used to predict BES behaviour with different HRTs. The bacterial community of the bio-cathode under galvanostatic mode was dominated by a few populations, including the genera Rhizobium, Bosea, Fontibacter and Gordonia. The results provide useful information for the scale-up of BES treating multi-contaminated groundwater

Resin-based composite materials and natural anterior teeth: an “aesthetic” challenge

This thesis aims to clarify several issues within the field of direct composite resin materials. A new classification system for composite materials has been suggested, on the basis of the two main components (fillers and the matrix). The mechanical performance of the material when subjected to an artificial fatigue load, simulating that of the oral cavity, has been assessed. An evaluation of colour compatibility, colour stability and contrast ratio of different resin composites and gloss retention and staining behaviour of these materials in response to normal conditions such as exposure to common foods, beverages and brushing habits, was then evaluated. The second part of this thesis is based on the optical characterisation of natural teeth, with particular emphasis on enamel and the enamel-dentine complex. An in-vivo evaluation using a spectrophotometer is proposed for measuring the mismatch between a composite restoration and the corresponding area of the contralateral sound tooth

Mega-abrasion: Case History Report on Management of a Fluorosis-Affected Patient

Different approaches ranging from veneers and crowns to employing the more conservative use of freehand resin composites have been proposed to correct esthetic problems caused by enamel fluorosis (EF). However, the protocol of mega-abrasion followed by microabrasion may be used as an alternative. It is less invasive and can minimize the unesthetic brown-to-whitish spots caused by EF. This article describes an easy and low-cost technique for managing enamel defects in a patient with severe enamel fluorosi

Évaluation de l'adaptation interne de moignons préprothétiques adhésifs après test de fatigue "in vitro" : influence du matériau de fabrication du tenon

Un test de fatigue non destructif a été appliqué à des tenons et moignons adhésifs standardisés, réalisés sur dents lactéales bovines, traitées endodontiquement. Six tenons de forme identique mais de composition différente ont été utilisés pour la fabrication des restaurations: 3 avec structure anisotrope (résine époxy et fibres de carbone, quartz et hybride carbone/quartz) et 3 avec structure isotrope (zirconium, acier inox et titane). Les échantillons ont été mis sous contrainte mécaniquement (1 million de cycles, charge de 50 à 100 N et fréquence de 1.5 Hz). L'adaptation interne des restaurations a été évaluée au microscope électronique à balayage sur des sections des échantillons. Les tenons isotropiques ont présenté plus de défauts d'adaptation au niveau de l'interface composite de scellement - dentine ou composite de scellement - tenon. En l'absence d'un effet de cerclage et d'une restauration prothétique, les tenons fibrés anisotropiques ont montré un meilleur potentiel de stabilisation de la structure préprothétique

Shade correction technique for free hand bonded restorations

The aim of this short communication is to describe an easy technique illustrating how to correct an esthetic mismatch between a natural tooth and a free hand bonded restoration

Biomimetic direct composite stratification technique for the restoration of anterior teeth

The aim of this article is to describe a simplified layering technique based on a biomimetic approach for large anterior Class 4 restorations. The proposed layering technique is based on a modified layering technique where palatal enamel and dentin masses are replaced with the same quantity of a microhybrid enamel and dentin shade composites, respectively, while for the thin buccal enamel layer a microfilled resin composite is used. Transparencies and, whenever necessary, white spot characterizations, are created by interposing blue and white effect masses between dentin mamelons, under buccal enamel. The combination of a microfilled composite with a microhybrid composite substituting the same quantity of lost enamel and dentin better mimics the physical and optical characteristics of the natural tooth. The biomimetic composite restoration may be considered an interesting alternative to ceramics, minimizing invasiveness, chair time, and costs for patients