Relining of prosthesis with auto‐polymerizing hard denture reline resins: effect of post‐polymerization treatment on flexural strength

Abstract

It has been suggested that microwave irradiation and prosthesis immersion in hot water after its polymerization may improve mechanical and viscoelastic properties of acrylic resins. This study was proposed to verify the influence of microwave post-polymerization (PP) treatment over the flexural strength of thermo-polymerizing acrylic resin specimens (QC-20) relined or not with two different composition hard chairside auto-polymerizing reliners [Kooliner (K) and New Truliner (NT)]. For this study, 50 specimens of 64 x 10 x 3.3 mm were polymerized and distributed into five groups. G1 (control) specimens without relining and PP; G2 specimens relined with K, without PP; G3 specimens relined with NT, without PP; G4 specimens relined with K, with PP (microwave irradiation with 650 W for 5 min); G5 specimens relined with NT, with PP. Tests were performed on a universal testing machine Instron 4411 with compression speed of 5 mm/min. Specimens of K without PP did not show statistically different results (p < 0.05) when compared with control. However, when submitted to PP these specimens showed a significant increase in flexural strength. Specimens of NT showed the lowest flexural strength of all groups, with or without PP when compared with control and K groups. Microwave PP (650 W for 5 min) proved to be an effective method of improving the flexural strength of K relined prosthesis. However, it did not seem to affect NT specimens.