Enhancement of mechanical properties of experimental composite by Fuller's earth nanofibers for cervical restoration

Abstract

In this research, we studied improvement of mechanical properties of dimethacrylate-silica based dental composites by addition of Fuller's Earth (FE) clay. Three composites were made as base compounds consisting of 68, 58, and 48 wt % resin and 31, 41, and 51 wt % silica, respectively. Afterward, the composites were modified by adding FE. Mechanical properties including flexural strength, flexural modulus, work-of-fracture, fracture toughness, and microhardness were measured. Clay particles and fracture surface of composites consisting of 51 wt % silica (with and without FE) were examined by SEM. Measured results showed that flexural strength, work-of-fracture, flexural modulus, and microhardness of all composites increased by including FE nanofibers. Fracture toughness except for composite including 51 wt % silica had similar variations. It seems that locating FE nanofibers in weak resin region among silica particles leads to strengthening mechanisms, such as bridging and crack deflection, which cause improvement in mechanical properties.

Effect of nanofibers as reinforcement on resin-based dental materials: A systematic review of in vitro studies

“…Although the stress-induced phase transformation of zirconia contributes to the toughening effect, the authors also attributed this increase in FT to the incorporation of ZS nanofibers, which play the role of a “bridge” in the fracture regions [32] . Other studies also reported that the FT of resin-based composites is improved when they are reinforced with fibers [25] , [29] , [30] , [40] , [41] , [42] .…”

“…There are different compositions of glass fibers, such as S-glass or E-glass, representing different properties, although all of them are amorphous and atoms arranged randomly. Overall, glass fibers-reinforced composites provide high toughness, non-corrosiveness and aesthetic characteristics [24] , [29] , [30] , [40] , [42] , [43] , [45] , [47] , [48] , [49] , [50] .…”

“…This is due to the random orientation of microfibers in a resin matrix and the formation of a fiber network, which seemed to have enhanced the ability of the material to resist the fracture propagation as well as to reduce the stress intensity at the crack tip from which a crack propagates in an unstable manner. As a consequence, an increase in the flexural properties and FT can be expected [40] . This property is vital in dental composites because a bulk fracture is one of the main reasons for the reduced life spans of restorations.…”

“…Most of the studies presented herein evaluated materials containing glass fibers [24] , [29] , [30] , [40] , [42] , [43] , [45] , [47] , [48] , [49] , [50] , [51] , [52] . There are different compositions of glass fibers, such as S-glass or E-glass, representing different properties, although all of them are amorphous and atoms arranged randomly.…”

Nanotechnology for Dentistry: Prospects and Applications

“…Mechanical investigations showed that for 0.72 wt.% of nanofiller, the properties were the best, with a flexural strength of 105 MPa, flexural modulus of 2.79 GPa and a work-of-fracture (WOF) 8.19 kJ/m 2 , which is very important for cervical restorations. In comparison with the composite without filler, these values slightly increased [ 47 ]. However, clay substances can insignificantly affect some mechanical properties of the dental composite, as described by Mucci et al The authors introduced a polymer montmorillonite (MMT), which is composed of sheets of approximately 1 nm thickness and a diameter in the range of 50 nm to a few µm.…”