The purpose of this study was to investigate the effects of silanized spherical silica fillers (SF) on the immediate and 24-hour marginal gaps of resin-modified glass-ionomer cement (RMGIC) in tooth cavities. In correlation with marginal gap formation in the tooth cavity, these influencing factors were also examined: marginal gap and setting shrinkage of cement in the Teflon mold, as well as the shear bond strength to tooth substrate.Moreover in correlation with caries prevention, fluoride release was examined too.In this investigation, the fillers were mixed into the RMGIC powder (Fuji II LC EM). Untreated spherical silica filler (UF)-added RMGIC was used as a comparison.When compared with the control (i.e., original RMGIC), the addition of SF significantly decreased immediate marginal gap in tooth cavities and setting shrinkage in Teflon mold up to 63% and 66% respectively.Fluoride release was significantly reduced too. Apart from these results, this study showed that addition of 5wt% SF increased the shear bond strength to human enamel and dentin.
This study investigated the effects of spherical silica fillers on the physical and mechanical properties of resin-modified glassionomer cement (RMGIC).Specimens were fabricated by mixing untreated (UF) or silanized (SF) spherical silica filler into the powder of a commercially prepared RMGIC. The original RMGIC and a preparation containing 20wt% spherical silica filler were also examined with regard to their fractured surface and fluoride release. The fillers increased the compressive strength remarkably:up to 17% in the case of SF and 9% in the case of UF. Both UF and SF increased the flexural strength by up to 17%. The addition of SF increased the DTS up to 38%, but UF decreased the DTS. The addition of SF improved the workability and the mechanical properties of the RMGIC.
INTRODUCTIONIt was reported 1-4) that in resin-modified glassionomer cements(RMGICs)is found the best of both glass-ionomer cements (GICs)and resin composites. From GICs, RMGICs acquire the inherent adhesion and cariostatic properties of GICs. From resin composites, RMGICs acquire the command setting behavior, as well as good mechanical properties and wear resistance. As a result, when compared with conventional GICs, RMGICs have been characterized as having a longer working time with rapid set, improved appearance and translucency, as well as higher early strength and higher bond strength to enamel and dentin 2,4-9) . Endowed with these advantageous properties, RMGICs therefore have less microleakage than conventional GICs 6-8,10,11) . Furthermore, the rapid setting of RMGIC is an advantage for color stability, as water no longer inhibits the setting reaction by the time photopolymerization is completed 12) . In previous studies 13,14) , it was reported that the addition of spherical silica filler to a RMGIC powder improved the flowability or workability of the cement -based on the latter's rolling performance. Silanization of filler depends on siloxane bridge(Si-O-Si) formation between the silica surface and the silane molecule 15), and addition of silanized spherical silica fillers(SF)to RMGIC has been shown to yield good results after 24 hours: increased compressive strength, diametral tensile strength and flexural strength, and reduced water uptake. Further, it was shown that SF improved the mechanical properties of RMGIC more than untreated spherical silica fillers (UF) 13,14) . Indeed, SF addition also reduced the immediate marginal gaps in tooth cavities and setting shrinkage of RMGIC in the Teflon mold by 63% 16) . However, the effect of SF addition on interfacial gapformation in Class V restorations, where RMGICs are usually used, has not been studied. It is usually recommended that restorations be polished after 24 hours 6,13,16,17) . However, for practical reasons, dentists seldom or never do that. As a matter of fact, most general practitioners would polish the restoration once it is cured or set. In this immediate condition, the mechanical strength of restorative materials is weaker than that after one-day storage 17). Moreover, the polishing technique or surface protector also influence microleakage and interfacial gap-formation at this condition 18-21) . Against this background, it is important to study and evaluate the mechanical properties of restorative materials in the immediate condition and their influence on immediate interfacial gap-formation in restorations.In the present study, the first hypothesis was that the addition of SF to RMGIC would reduce immediate interfacial gap-formation in Class V cavities. The aim of this study was to investigate how the addition of silanized spherical silica filler(SF)would influence the formation of summed, immediate interfacial gaps in Class V tooth cavities. Resin-modified glass-ionomer cement(RMGIC)is usually used for Class V restora...
To minimize gap formation, more fluid mixes could be used especially with Fuji II LC to give improved adaptation to the dentin. Secondly, whenever possible, polishing should be delayed on the final increment to permit maturation and minimize mechanical disruption of both increments.
In this study, we evaluated the effects of 10 wt% spherical silica filler (SSF) addition on 24-h compressive strength, modulus of elasticity, water uptake, and immediate setting shrinkage of conventional glass-ionomer (Fuji II and Experimental) and resin-modified glass-ionomer (Fuji II LC EM) cements. The glass-ionomer cement powders were modified by being mixed with 10 wt% SSFs with an average particle diameter of 0.3 microm. The materials were mixed to consistencies similar to the flow of Fuji II mixed with a powder-liquid ratio of 2.7:1 (w/w). The 24-h compressive strength, modulus of elasticity, water uptake, and immediate setting shrinkage were observed and the results compared with the original materials mixed with similar flow. The addition of SSF increased the compressive strength value to 1.1 times, while the increase of moduli of elasticity was 1.10 to 1.35 times. In general, the addition of SSF decreased the 24-h water uptake to 80-90% and reduced the immediate setting shrinkage to 70-79% of the original materials. The addition of 10 wt% SSF improved the characteristics of conventional and resin-modified glass-ionomer cement.
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