Evaluation of Mechanical Properties of Composite Materials Used in Dentistry Varying the Inorganic Composition

Abstract

The aim of this study was to determine the hardness and the elasticity modulus of the two composite resins base of BISGMA with different inorganic particles: a nanoparticulated with a ceramic withload, (Filtek Z350XT-3M) with and without thermal activation and a microhybrid with no ceramic load (Opallis-FGM). The samples were prepared and subjected to the tests of Vickers hardness (Shimadzu HMV) and acoustic excitation pulse (Sonelastic ®). The samples were divided into three groups: G1-Filtek Z350 XT; G2-Filtek Z350XT MO (subject to further polymerization microwave) and G3-Opallis. The results showed that the hardness of G2 was significantly higher than the groups G1 and G3. The elastic modulus was higher than the G2 to G1 and G3. One can conclude that the resins filled with inorganic ceramic filler showed higher hardness and elastic modulus. The thermal activation increased the hardness and the elasticity modulus of the resin with ceramic load.

Evaluation of Bonding Resistance after Surface Treatment of Two Glass-Ceramics Used in Dentistry

“…When the bonding resistance of both studied glass ceramics was compared, the e.max ceramic showed higher values than those of Suprinity in the three conditioning times. These results can be explained by the structural characteristics of the ceramics, where e.max press has elongated crystals of lithium disilicate and is a ceramic vitrified with one of lithium disilicate which represents around 70% in volume, and the crystals with 5 μm length and 0,8 μm diameter [2,8,19,20,21]. Melo-Silva et al [8] presented in a morphological qualitative analysis that the hydrofluoric acid is capable of dissolving the glass matrix of the lithium disilicate ceramic, exposing the crystals and giving an irregular surface, improving the micro mechanical retention between ceramic and luting agent.…”

“…In cases where restorations are made with glass ceramic, an effective adhesion can be obtained from two main mechanisms. One of these mechanisms consists of the ceramic conditioning with hydrofluoric acid that, given its corrosive nature, is capable of dissolving the glass matrix forming micro retentions on the ceramic surface [8]. The other principle bases itself on the chemical adhesion provided by the silane, a bifunctional structured molecule capable of bonding two substrates of distinct compositions (organic and inorganic) [9,10].…”

“…Another worrying motive regarding the usage of hydrofluoric acid is related to concentration and conditioning time which can compromise the bonding strength and/or the ceramic material resistance. Although the manufacturer indicates concentration of 5% and the time of 20 seconds of conditioning, there is controversy in literature about these parameters [8,13].…”