No abstract

The purpose of this study was to evaluate the flexural strength, flexural modulus, modulus of resilience, and water sorption of four flowable light-cured composite resins (FCRs). Results were then compared with four conventional composite resins (CCRs) and a minifilled hybrid light-cured composite resin, which served as a control. Twenty specimens were flexural tested immediately after curing, while others were stored in water at 37℃ for 1 month, 3 months, 6 months, or 1 year before flexural testing. The 1-year specimens were weight-measured at designated time intervals to examine water sorption. All FCRs, except Point 4 Flowable, showed higher flexural strength values than their CCR counterparts (p<0.05, Scheffé' s test). After one-year water storage, the flexural strengths and flexural moduli of FCRs increased 1.5-fold or more when compared with the immediate condition. In most cases, the moduli of resilience of FCRs were higher than those of CCRs. In conclusion, it was found that FCR and CCR with the same brand name had very different characteristics and mechanical properties.

This study investigated the effects of spherical silica filler (SSF) on the workability and mechanical properties of resin-modified glass ionomer cements for luting (RMGICL). Varying powder/liquid ratios (P/L=2.0, 2.2, 2.4, and 2.6) of a commercially available glass ionomer cement (Fuji Lute, GC Corp.) were mixed with SSF at different weight percentages (5, 7.5, and 10%). On film thickness, statistically significant effects of SSF addition were noted at 2.5 minutes after mixing started, notably at P/L=2.4 and 2.6 when 7.5 and 10 wt% of SSF were added. The same result was also obtained for consistency evaluation. On mechanical and bonding strengths to the tooth substrate, no statistically significant differences were observed among all the SSF weight percentages within each P/L ratio. SSF-added RMGICL at a higher powder/liquid ratio exhibited increased mechanical and bonding strengths when compared to a control without SSF addition, but nonetheless maintained the film thickness with no further increase.