Bond strength of silicone to polyurethane following immersion of silicone in cleaning solutions

Statement of problem. The use of polyurethane liners beneath silicone facial prostheses is recommended to improve the effectiveness of water-based adhesives, reduce bacterial colonization, and allow very thin margins. Patients using silicone prostheses with a polyurethane lining often observe different degrees of debonding which may lead to failure of the prosthesis. Aggressive cleaning may be associated with debonding of the silicone to polyurethane. Purpose. The purpose of this investigation was to determine the effect on bond strength of soaking specimens of silicone to Polyurethane in hot or room-temperature soapy water. Material and methods. Specimens of silicone to primed polyurethane were divided into 3 groups of 16 specimens for testing: control (no soak), room-temperature soapy water soak, and hot soapy water soak. The soaked specimens were placed in soapy water at different temperatures for 1825 minutes to simulate 1 year of a 5 min/day cleaning cycle. One examiner performed the assessment of T-peel strength (N/mm) for all specimens. Each specimen was attached to an adhesive testing machine and separated in tension at the crosshead speed of 25.4 mm/min. Data were analyzed with a 1-way ANOVA followed by post hoc pairwise testing using the Tukey test (alpha = .05). Results. A significant difference in bonding strength between the 3 groups was found (P < .001), with post hoc tests indicating that the control group bonding strength (6.06 +/- 1.84 N/mm) was significantly higher than both room-temperature water soapy soak (3.93 +/- 1.84 N/mm; P = .005) and the hot soapy water soak group values (2.49 +/- 1.75 N/mm; P < .001). However, there was no significant difference found between the hot and room-temperature soapy soak values. Conclusion. Within the limitations of this study, soaking in hot or room-temperature soapy water produced a significant reduction of bond strength of silicone to polyurethane.