The investigation of the bonding properties of silicone based maxillofacial prosthetic materials to the framework materials

Rehabilitation process of the defects that are in the maxillofacial area caused by congenital malformations, trauma and cancer surgery is an expensive and long challenge both for the prosthodontist and the patient. The bonding failure that occurs between the maxillofacial silicone elastomer and the framework that supports the maxillofacial prosthesis, holds the bar-clips and the magnets that are used in the implant supported maxillofacial prosthesis causes important clinical problems. Recently, fiber reinforced composites are being used as frameworks. In this in vitro study, the bonding is compared with 180˚ peel test and shear test between experimental fiber reinforced composite (F), orthoacrylic (O) and light cure denture base material (U) frameworks to the additional type silicone elastomer. For the 180˚ peel test (N=45, n=15/group), 75×10×3 mm frameworks were produced. The bonding between the same diameters silicone elastomer and the frameworks was made by the flasking process by the aid of the primer (G611 platinum primer, Principality Medical, UK). The specimen were artificially aged in the Xenotest Alpha aging chamber for 200 hours. 180˚ peel test was carried out in the universal testing machine (Autograph Model AG-IS 100 kN, Shimadzu, Kyoto, Japan) with 10 mm/min crosshead speed. The shear test specimens (N=45, n=15/group) were prepared in cylindrical fixtures (25 mm length×16 mm diameter) made of autopolymerising acrylic (Duracryl Self Cure, Duradent Erk Dental, Turkey). The silicone elastomer (3 mm length, 8 mm diameter) was bonded with the aid of the primer in the flasking process. The specimen were artificially aged in the Xenotest Alpha aging chamber for 200 hours. The specimen were positioned in the apparatus made for this study and tested with the cross head speed of 10mm/min the universal testing machine. All specimen were inspected with a magnifier (10×) and the failure were grouped as adhesive, mix and cohesive. The mean SG (shear bonding strength) values of the frameworks were evaluated statistically (Kolmogorov- Smirnov, Chi-square , Anova, α=0,05), O(0,6600±0,0515), U(0,5993±0,5516) and F(0,6820±0,0553) were not found significantly different (p>0,05). The shear test subgroups' bonding failure type were significantly different (p<0,05). In the O group, 20% adhesive, 60% mix and 20% cohesive failure, in the U group, 13,3% mix and 86,7% cohesive failure, in the F group 6,7% adhesive, 6,7% mix and 86,7% cohesive failure were observed. In all of the shear test subgroups, 4% adhesive, 26,7% mix and 64,4% cohesive failure were observed. In the 180˚ peel test, the mean PG (peel bonding strength) was not found statistically different between the U(0,8953±0,1897) and F(0,8807±0,2259) groups (p>0,05). The O(0,3267±0,0952) group was found statistically lower than U(0,8953±0,1897) and F(0,8807±0,2259) groups (p<0,05). In the 180˚ peel test, there wasn't found any difference between the subgroups as the failure type was evaluated (p>0,05). The O group showed 100 % adhesive failure, the U group showed 100% adhesive failure and the F group showed 80% adhesive and 20% mix failure. In all the 180˚ peel test subgroups, 93,3% adhesive failure and 6,7% mix failure was observed and cohesive failure was not observed. In SEM analysis, the specimen which showed adhesive failure showed residuel silicone. Generally, the silicone failure surfaces were seen irregular. It is observed that the experimental fiber reinforced composite could be an alternative to the other frameworks but further investigation and clinical studies should be carried out on this new material.