Mechanical Characterization of a Novel Regenerative and Anti-bacterial Composite Material

Secondary caries is one of the most frequently described causes of restorations failure and subsequent dental pulp infection resulting in tooth necrosis and tooth loss. Objectives:  To fabricate and characterize novel composite materials that are able to heal and regenerate the lost dental tissues structure under a bacteria-free environment. Methods: A commercial composite (COMP) is modified by incorporating a new Ag-doped bioactive glass (Ag-BG) in powder form at various concentrations (0%, 5 wt%, 15 wt %). Microtensile test method is used to measure total bond strength (TBS) as an initial means of characterizing the BG/COMP materials. Additionally, antimicrobial properties of the materials are tested against several bacteria.  Results: Baseline studies on uncut enamel yielded mean TBS (Stdev) values for the control and 15 wt% of Ag-BG/COMP were 4.87 MPa (2.26) and 3.63 MPa (3.25), respectively. On dentin, TBS (Stdev) mean values are 9.70 MPa ( 4.11) for the control and 5.81 MPa (2.58) for the 15 wt% of Ag-BG/COMP. TBS values are higher for composite samples that contain only 5 wt% of Ag-BG/COMP (mean value of 6.58), compared to that of the 15 wt% sample set. In regards to the anti-bacterial properties, 15 wt% of BG/COMP was the only composition to exhibit strong bacteria inhibition and significant antimicrobial properties compared to control and to 5 wt% of BG/COMP.  Conclusion: Increase in the percentage of Ag-BG incorporated within the COMP results in a decrease of the mechanical properties of the COMP, but increases the antimicrobial properties. The less potent antibacterial behavior in case of 5 wt% of BG/COMP may be assigned, at least in part, to the change in the increase of the surface roughness which enhances bacteria attachment. Further tests using intermediate concentrations and/or different methods of integration are needed to optimize this novel material for future clinical applications.