Bonding strength of 3D printed silicone and titanium retention magnets for maxillofacial prosthetics application

Purpose: To assess the bonding between conventional and additively manufactured silicone elastomers and cylindrical retention titanium magnets for anchorage of facial prostheses. Methods: The customized titanium retention magnets were embedded in conventional and additively produced silicone blocks without primer application (n = 20) and with two commercially available primers G611 (n = 20) and A304 (n = 20) applied onto the magnet surface. The pull out test was performed in the universal testing machine using 45 degrees and 90 degrees angulation and the pull out strength was measured for each group. Additionally the SEM images of the pulled out magnets' surface were obtained and the amount of residual silicone onto the magnet surface was quantified. Results: Significantly higher pull out strength values (p < 0.05) were revealed for 90 degrees specimens (0.11 - 0.17 +/- 0.01 N/mm(2)) compared to the 45 degrees group (0.03 +/- 0.02 N/mm(2)). The pull out test with primer revealed no significant differences between the G 611 and A 304 primers in the additive group. However, significantly (p < 0,05) higher values were observed for conventional specimens in the A304 group (1.10 +/- 0.21 N/mm(2)) compared to the G611 group (0.59 +/- 0.27 N/mm(2)). Conclusion: The application of both used primers may be an acceptable technical option for the anchorage of retention titanium magnets in silicone facial prostheses, produced additively in a fully digital workflow.