Mechanical properties and bonding of maxillofacial silicone elastomer mixed with nano-sized anti-microbials

The antibacterial efficacy of silicone is improved by impregnating it with antimicrobials such as chlorohexidine and zinc oxide. The purpose of this study was to examine mechanical properties and bonding of maxillofacial silicone elastomer mixed with Zinc Oxide nanoparticles (ZnO-NP), and Chlorohexidine Diacetate Salt (CHX) at three different concentrations (1 %, 3 %, and 5 %).

Specimens of a silicone elastomer (M511) were prepared and divided into 7 groups. Group 1 was control of no additive. Groups 2-4 included silicone elastomer mixed with ZnO-NP (surface area = 67 m2/g) at 3 different concentrations (by weight %); 1 %, 3 % and 5 %. Groups 5-7 included silicone elastomer mixed with CHX at the same concentrations. Tear and tensile strengths, elongation percentage, modulus of elasticity, and shear bond strength to primed acrylic resin surfaces were evaluated. Data was analyzed with 1-way ANOVA, Bonferroni, and Dunnett's T3 post-hoc tests (P < 0.05).

There was significant effect of the additives on the tensile strength, elongation percentage, tear strength, and shear bond strength (P < 0.05). Shear bond strengths ranged from 0.55 to 0.96 MPa. Silicone elastomer mixed with CHX (5 %) resulted in the highest shear bond strength (P < 0.05). Non-linear regressions between tensile strength and ZnO and CHX additives were 0.95 and 0.96 respectively.

All additives reduced the tensile strength of the silicone. However, CHX at 5 % optimized shear bond strength and thus is proposed in order to fabricate maxillofacial prostheses of sufficient mechanical properties, bonding and antimicrobial activity.