Optimization of Facial Silicone Elastomers Antimicrobial Activity: In-Vitro Study

Abstract

Objective: Maxillofacial prostheses when worn can be contaminated by oral and skin microflora, which risk the patient’s tissue. Also, skin around craniofacial implants retaining maxillofacial prosthesis shows a microflora of potential pathogens causing peri-abutment infection. This study aimed to investigate the effect of Zinc Oxide nano particles (ZnO-NP) and Chlorohexidine Diacetate Salt (CHX) inserts on the antimicrobial activity of maxillofacial silicone elastomer at three difference concentrations (1%, 3%, and 5%).
Materials and Methods: a commonly used maxillofacial silicone elastomer (M511, Technovent, UK) was mixed with ZnO-NP and CHX at 1%, 3%, and 5% concentrations (by weight). Then it was packed inside disc-shaped steel molds (40 mm diameter and 0.5 mm height) and cured for 1 hour at 100? then smaller silicone discs (10 mm diameter) were produced. Sixty specimen per insert were made for the three concentrations. Each concentration included 20 sample which were divided equally between two inoculants; Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans). Eighty samples of silicone without any insert were made and divided into 4 groups acting as negative control (NC) and 4 groups acting as double negative control (DNC). The upper surface of each specimen was inoculated with 200µl of inoculant (106 cfu). NC specimens were inoculated with 200 µl of inoculant (S. aureus or C. albicans) without CHX or ZnO-NP. DNC specimens were inoculated with 200 µl sterile distilled water and it did not have CHX or ZnO-NP nor S. aureus nor C. albicans.
Results: There was an observed decrease in colony forming units of S. aureus and C. albicans when tested against 1%, 3%, and 5% concentrations of CHX and ZnO-NP. However, complete growth inhibition of both organisms was only obtained at 5% concentration of CHX where there was zero number of colonies (100% growth inhibition). No colonies were detected at the DNC disc as expected. The NC specimens showed numerous uncountable colonies as expected.
Conclusion: CHX exhibited antibacterial activity against some oral pathogenic strains better than ZnO-NP. It has the potential to completely eliminate bacteria when mixed at 5% (by weight), thus, contributing to the disinfection of silicone-based materials and the preventing infections caused by Candida albicans or Staphylococcus aureus.