Generally, in vitro oral biofilm models are commonly used to help in understanding the complex processes and the factors affecting oral diseases. They help to accurately predict, in a controlled and simplified way, a clinical outcome which can lead us to preventive actions for a disease (Salli and Ouwehand, 2015).The complexity of biofilm research requires different approaches to address various questions. Furthermore, models cannot capture all of the details involved with disease formation, however it is considered a way of performing a reproducible experiment under controlled conditions. Obviously there are ethical limitations with in vivo studies in relation to caries and periodontal diseases. Therefore, different in vitro techniques have been developed and are continuously improved to better address the study question, to help interpret the results and to obtain as much information as possible with other than clinical testing (Salli and Ouwehand, 2015).This project aimed at developing a robust in vitro oral biofilm model to determine the effectiveness of enhanced dental restorative materials using antimicrobial additives. It is focused on the antibacterial and mechanical properties of novel silver formulations that have been combined with glass ionomer cement. Three out of nine bacterial species considered to be early colonisers (Streptococcus oralis, Streptococcus mutans, & Neisseria subflava) were inoculated at 0.1 OD600 into wells containing sterile glass-ionomer disks. The established artificial saliva media DMM (Defined Medium Mucin) was used for 24-48Hrs studies, conducted under aerobic and anaerobic conditions.Following incubation, the disks were washed with PBS (Phosphate Buffer Saline) in a series of up to five, twelve minute steps. The bacterial community within the well, loosely attached to the well surface and the disk, and finally the bacteria intimately attached to the surface were determined using a viable count of Colony Forming Unit Count (CFUs), a MTT metabolic assay and DNA quantification. Three silver solutions were developed with different ionic concentrations, 5mg/ml, 10mg/ml and 13mg/ml. The addition of polyvinyl alcohol to stabilise the 10mg/ml solution was investigated and along with the MIC/MBC and the effect on the ability of three bacterial species to survive and colonise glass ionomer disks was determined. In addition, compressive strength, hardness and adhesive shear bond strength of each glass-ionomer silver disk was assayed and compared with the base line glass-ionomer.The biofilm model favoured survival of S. oralis under aerobic conditions and N. subflava and S. oralis under anaerobic conditions. Silver formulations proved to have effects on both strength and antimicrobial activity. Specifically, 5mg/ml proved more antibacterial than 10mg/ml silver. Compressive strength was enhanced for both concentrations of additive, however bond strength became compromised at the higher concentration.This model proved its efficiency to test the antibacterial activity of silver enhanced glass ionomer cement in the presence of artificial saliva. Furthermore, addition of 5mg/ml silver to the glass ionomer cement enhanced antibacterial activity and physical properties significantly.
|Date of Award||2018|
|Sponsors||University of Jordan|
|Supervisor||Mark Hector (Supervisor) & David Edwards (Supervisor)|