Effect of environmental factors on serviceability of fibre-reinforced maxillofacial prostheses

Objective: To investigate mechanical integrity of maxillofacial silicone elastomers with embedded glass-fibre bundles and the effect of different aging-intervals on the bond-strength of the embedded glass-fibre bundles using a pull-out test.

Materials and Methods: Four groups (n=10) were fabricated by embedding EverStick glass fibre-bundles (diameter=1.50mm, length=20mm) into silicone. Each specimen was cylindrical (diameter=4.40mm, height=20mm), with the glass-bundle along its centre axis. Specimens were differently conditioned: dry storage for 24 h (group1, control); groups 2, 3 and 4 aged in an environmental chamber for 200, 400 and 600 h respectively, and subjected to complete weathering cycle of 120 min (18 min wet, then 102 min dry, with 20kLux Xenon lighting).

Bond-strengths between fibre-bundles and silicone were examined by Pull-out tests at 1 mm/min displacement. Maximum debonding force and work were recorded. One-way ANOVA and Bonferroni post-hoc tests were applied to find significant differences (p≤0.05).

Results: Mean±SD values of pull-out parameters at 0, 200, 400 & 600 h aging were, respectively: Maximum force (N): 13.63±7.45, 19.67±1.37, 13.58±2.61, and 10.37±2.52. Displacement-force was maximal after 200 h of aging (p≤0.05). Such increase suggests further polymerization of specimens by the environmental conditions of the aging chamber. Longer aging weakened the silicones and their interfacial strengths with the embedded fibres. However, Pull-out Work (N.mm) was calculated to be: 0.94±0.32, 0.48±0.30, 0.69±0.51 and 0.77±0.16, which was maximal at baseline and minimal after 200 h.

Conclusions: For fibre-reinforced maxillofacial prostheses; sufficient bond-strength was present between EverStick glass-fibre bundles and silicones, indicating a serviceable performance over time. Furthermore, bond strength was enhanced with accelerated aging, up to 200 h of exposure to environmental factors.