Microhardness and fluoride release of restorative materials in different storage media

This study evaluated the surface microhardness and fluoride release of 5 restorative materials - Ketac-Fil Plus, Vitremer, Fuji II LC, Freedom and Fluorofil - in two storage media: distilled/deionized water and a pH-cycling (pH 4.6). Twelve specimens of each material, were fabricated and the initial surface microhardness (ISM) was determined in a Shimadzu HMV-2000 microhardness tester (static load Knoop). The specimens were submitted to 6- or 18-h cycles in the tested media. The solutions were refreshed at the end of each cycle. All solutions were stored for further analysis. After 15-day storage, the final surface microhardness (FSM) and fluoride release were measured. Fluoride dose was measured with a fluoride-specific electrode (Orion 9609-BN) and digital ion analyzer (Orion 720 A). The variables ISM, FSM and fluoride release were analyzed statistically by analysis of variance and Tukey's test (p<0.05). There was significant difference in FSM between the storage media for Vitremer (pH 4.6 = 40.2 ± 1.5; water = 42.6 ± 1.4), Ketac-Fil Plus (pH 4.6 = 73.4 ± 2.7; water = 58.2 ± 1.3) and Fluorofil (pH 4.6 = 44.3 ± 1.8; water = 38.4 ± 1.0). Ketac-Fil Plus (9.9 ± 18.0) and Fluorofil (4.4 ± 1.3) presented higher fluoride release in water, whereas Vitremer (7.4 ± 7.1), Fuji II LC (5.7 ± 4.7) and Freedom (2.1 ± 1.7) had higher fluoride release at pH 4.6. Microhardness and fluoride release of the tested restorative materials varied according to the storage medium.

Influence of bleaching treatment on flexural resistance of hybrid materials.

The aim of this study is to evaluate the flexural resistance of three types of restorative materials: compomer (Freedom), resin-modified glass-ionomer (Vitremer) and composite resin (Esthet-X), observing whether the application of bleaching agent can cause alterations of their flexural properties. Sixty samples were made using a 10 x 1 x 1 mm brass mold, and divided into three groups: G1- Freedom (SDI); G2- Vitremer (3M ESPE); G3- Esthet-X (Dentsply). On half of the samples of each group (10 samples) the bleaching treatment was applied and the other half used as control, was stored in distilled water at a temperature of 37 degrees C. Whiteness HP Maxx bleaching system was applied on the sample surface following the manufacturer's recommendations, simulating the bleaching treatment at the clinic. After this period, a flexural strength (three-point bending) test was conducted using (EMIC DL 1000) machine until the samples fractured. The data were submitted to ANOVA and Tukey tests. Of the restorative materials studied, G3-(87.24 +/- 31.40 MPa) presented the highest flexural strength, followed by G1-(61.67 +/- 21.32 MPa) and G2-(61.67 +/- 21.32 MPa). There was a statistical difference in flexural strength after the bleaching treatment. It was concluded that the use of a beaching agent can promote significant alteration of the flexural strength of these restorative materials.

Locke, on freedom and will

This article aims to discuss Locke`s compatibilism, that is, the lokean thesis that freedom is compatible with the natural necessity. To this end, it is analized the chapter Of The Power (XXI, book II of the An Essay concerning Human Understanding), in which Locke clarifies the concepts of freedom and will. Although Locke, at times, involves himself with the incongruent thesis on compatibilism, he is a compatibilist. The impression that Locke would defend incompatibilists` theories ends up being abandoned when we analyze carefully his general argument about will and freedom. Locke literally defends that the volunteer does not differ from the necessary. As a compatibilist, Locke maintains that will is not free. Thus, the free man can not be the one that is free to want. A man regarded as a free agent is the one that has freedom of action, not freedom of will.