Effect of thermocycling on the mechanical properties of soft liners

Objectives: To evaluate the effect of thermocycling on the mechanical properties of one acrylic based and three poly(siloxane) soft liners. Methods: A total of 120 specimens from an acrylic based; Astron Light (AL) and three polysiloxane based ; Molloplast B (MLP), Silagum Comfort (SC), and GC Reline Soft (GC) materials were tested. Dumbbell and trouser leg specimens of each material were prepared for tensile and tear testing respectively. Specimens were divided into three test groups (n=5) and were either stored for 24 hours in distilled water at (37±1)°C (Control) or thermocycled for 1000 or 3000 cycles between (5±1) and (55±1) °C. Tensile strength and tear resistance values were determined using a testing machine at a crosshead speed of 50 mm/min. Data were analyzed with one-way ANOVA and Tukey HSD to determine significant differences. Results: Tensile strength and tear resistance results are presented in the table. Tensile strength and tear resistance showed significant differences among the tested materials (p<.05). Thermocycling did not result in significant changes on tensile strength (p>.05) except AL. Both thermocycling and number of cycles caused significant differences in tear resistance for AL, MLP and GC (p<.05). AL showed apparent hardening after thermocycling. Conclusion: Thermocycling has variable effects on the mechanical properties of soft liners. Poly(siloxane)s were more stable whereas acrylic based material had improved mechanical properties accompanied with hardening of the material.