The aim of this study was to evaluate the effect of various curing conditions in a pressure cooker on the
flexural strength of hard chairside reline resins. One hundred and forty hard chairside reline resin (UnifastTM Trad and
Tokuyama® rebase II Fast) specimens were prepared per ISO 20795-1 (2013) and divided into 14 groups. Each material
was cured following the manufacturer’s instructions as a control group and six experimental groups: cured under
1,500 mmHg air or nitrogen compressed pressure cooker at 55ºC for 10, 15 or 20 minutes. The specimens were
stored in water at 37±1 ºC for 50±2 hours before testing. The three-point bending test was performed using a universal
testing machine at a cross-head speed of 5 mm/min. One-way ANOVA and post hoc Tukey’s analysis at a 95%
confidence level were used to statistically compare the mean flexural strengths of the groups. For each material,
the flexural strength of the air and nitrogen compressed groups were significantly higher compared with the control
group (P<0.05). The flexural strength of the 10-min nitrogen group was significantly higher compared with the 10-min
air group (P<0.05). There was no significant difference in flexural strength between the 15-min nitrogen and 15-min
air groups (P>0.05). However, the flexural strength of the 20-min nitrogen group was significantly higher compared with
the 20-min air group (P<0.05). The flexural strength in the 10, 15, and 20 min curing time groups of each reline
material with the same curing environment in the pressure cooker were not significantly different (P>0.05). Under
the same curing conditions, UnifastTM Trad had significantly higher flexural strength compared with Tokuyama® rebase
II (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 increased the flexural strength compared with using air
pressure.