Effect Of Various Curing Conditions In Pressure Cooker On Flexural Strength Of Denture Hard Relining Materials

Abstract

This study evaluated the effect of various curing conditions in pressure cooker on flexural strength of hard chairside reline resins (UnifastTM Trad, Tokuyama® Rebase II Fast with and without Hardener®). For each material, 70 specimens were prepared and divided into 7 groups consists of control group and 6 experimental groups: cured in 2 bars air or nitrogen pressure cooker at 55ºC for 10, 15 and 20 min respectively. For Hardener® groups, specimens were soaked in Hardener® for 3 min after curing. The flexural strength was tested using a Universal testing machine. The data were analyzed using Three-way ANOVA, One-way ANOVA and post hoc Tukey’s HSD analysis at a 95 % confidence level. Three-way ANOVA result was showed that types of materials and curing environments affected on the flexural strength (P<0.05) but curing time did not affect on the flexural strength (P>0.05). In each material, the flexural strengths of air and nitrogen compressed groups were significantly higher than that of control group (P<0.05). In each material, the nitrogen compressed groups also had significantly higher flexural strength compared with the air compressed groups (P<0.05) With the same curing conditions, the UnifastTM Trad groups had significantly higher flexural strength than the Tokuyama® Rebase II Fast groups with and without Hardener® (P<0.05). However, there was no significant difference in the flexural strength between the Tokuyama® Rebase II Fast groups with and without Hardener® (P>0.05). Curing in the pressure cooker increased the flexural strength of the hard chairside reline resins. Moreover, using nitrogen gas pressure with satisfactory curing duration also increased the flexural strength compared with using air pressure.