Aim: The aim of the present study was to compare and evaluate the flexural strength of heat-polymerized Lucitone 199 and SR Ivocap denture base resin materials which uses polymerization techniques of compression molding and injection molding respectively and effect of artificial saliva and distilled water on long-term. Materials and methods: Ninety specimens each from both the materials measuring 65 × 10 × 3 mm were prepared. After the polymerization, flexural strength was calculated after 24 hours (control group) without immersing in the liquid medium. The test group specimens immersed in saliva and distilled water at 370C was calculated for the flexural strength at 2 weeks, 1 month, 2 months and 4 months. The flexural strength was measured using a universal testing machine. One-way analysis of variance (ANOVA) method was used to analyze the data, pairwise comparisons were done using Bonferroni post hoc test with a probability of less than 0.05 were considered to be statistically significant. Results: The evaluation showed that, despite the duration of immersion and type of acrylic resin, high flexural strength was seen with specimens immersed in saliva than specimens under distilled water. The higher flexural strength was seen in SR Ivocap compared to that of Lucitone 199 with the p value less than 0.05 which showed significant statistically. Conclusion: From the results, we can conclude that the higher flexural strength was shown in specimens of SR Ivocap fabricated through injection molding technique compared to specimens of Lucitone 199 fabricated through compression molding technique after immersion in artificial saliva and distilled water for long term. Clinical significance: The homogeneous copolymer beads, the difference in the water sorption and powder to liquid ratios also affect the mechanical properties of the resins other than the type of resin used in the dentures base.