Synthesis and characterization of novel dental adhesives with enhanced antibacterial and mechanical properties

Objectives: The dental bonding agents adhere to composite restoration and tooth structure. Besides composites, it is also very desirable for bonding agents to be antibacterial to inhibit recurrent caries at the tooth-composite margins. This work is focused on the development of dental adhesives with enhanced antibacterial and mechanical properties.
Methods: Novel methacrylate-based dental adhesives were developed containing titanium dioxide and an ionic liquid TEAF (triethanol amine formate) as antibacterial agents. The biocompatible ionic liquid TEAF not only show the antibacterial property but it also acts as coupling agent. The weight ratios were varied in order to obtain optimum antibacterial efficiency and mechanical properties. The obtained materials were characterized with Fourier Transform Infrared Spectroscopy, Thermogravimetric Analysis/Differential Scanning Calorimetry and Knoop Hardness testing. Non-carious human extracted premolars were used to evaluate the shear bond strength of the adhesive using Universal Testing Machine (Testometric M500-50AT). Antibacterial (Staphylococcus aureus) studies were done by disc diffusion method using nutrient agar plates.
Results: Antibacterial tests showed that an adhesive composed of 5 wt% titanium dioxide and 3% ionic liquid TEAF showed enhanced antibacterial activity against Staphylococcus aureus compared to the control (Tetric N-Bond). FTIR spectra indicated the presence of titanium dioxide and ionic liquid in the adhesive. TGA/DSC results showed improved thermal stability compared to control. The mechanical properties of the developed dental adhesive were not significantly changed compared to the control adhesive.
Conclusions: It appeared that this experimental dental adhesive might potentially be developed into a clinically attractive dental adhesive due to its high mechanical strength and antibacterial function. Future work will be focused on the long-term in vivo evaluations of developed antibacterial adhesives using standardized protocols.