Quasi-elastic neutron scattering demonstrates proton mobility within dental cements as a function of time and temperature.
Heloisa Bordallo and Ana Benetti in the lab at NBI.
PHOTO: Ola J. Joensen, NBI
COPENHAGEN and LUND — A research collaboration between scientists at the University of Copenhagen (KU) and the European Spallation Source (ESS) has advanced the prospects for using glass ionomer cement (GIC) as a replacement material for common dental fillings.
GIC has several properties that make it an ideal tooth cement: its ability to directly bond to teeth; the fact that it contains and releases fluoride; and its similar thermal expansion coefficient to the teeth to which it is bound. There is only one problem: in its existing forms it is not a mechanically strong enough material for fillings.
The research team includes, among others, Heloisa Bordallo, associate professor and materials researcher at KU’s Niels Bohr Institute (NBI), and an ESS adviser and Science Focus Team member; Ana Benetti, dentist and researcher at the Odontological Institute at KU; and Markus Strobl, deputy head of instruments and instrument scientist at ESS.
Using neutron and X-ray instruments at Helmholtz-Zentrum Berlin, the KU-ESS team has gained further insight into the complex pore structure of GIC as well as the movement of hydrogen within these pores—two key factors in establishing the material’s durability. Neutron-enabled observations of the reactions between the GIC powder, acid additives, and water, in different combinations and at different stages of the curing process, has revealed a way forward for research in this area. The results have been published in a paper, How mobile are protons in the structure of dental glass ionomer cements?, on March 10 in Scientific Reports, and also reported on at the NBI and HZB websites.
The relationship between microstructure, hydrogen mobility and strength brings insights into the material's durability, also demonstrating the need and opening the possibility for further research in these dental cements.
-from the abstract
Pores and cracks are better visible in the X-ray images due to better resolution (a, c, e). Poor adaptation (*) of the more viscous restorative cement (Poly) at the bottom of the cavity is observed (e), while this problem is less evident for the less viscous cement (a, c). The presence of liquid inside or adhered to the internal walls of some of the larger pores is evident (in red, due to the higher attenuation coefficient of hydrogen) in the neutron image (b). The neutron images also suggest that interconnecting pores or cracks are filled with liquid (b, f), while some of the larger pores seem to be empty (d).