Glass Ionomer Cements with Improved Bioactive and Antibacterial Properties

Chen, S. 2016. Glass Ionomer Cements with Improved Bioactive and Antibacterial Properties. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1413. 62 pp. Uppsala: Acta Universitatis Upsaliensis. ISBN 978-91-554-9670-8. Dental restorative cements are placed in a harsh oral environment where they are subjected to thermal shock, chemical degradation, and repeating masticatory force. The ideal restorative dental cements should have superior mechanical properties, chemical stability, aesthetic, good handling properties, biocompatibility, antibacterial properties, and preferably bioactivity. This thesis presents research on dental restorative cements with enhanced properties. The overall aim was to increase the bioactivity and antibacterial properties of dental restorative cements without affecting their other properties. The effect from adding calcium silicate to glass ionomer cement (GIC) was investigated. The results showed that calcium silicate could increase the bioactivity and reduce the cytotoxicity of conventional glass ionomer cement without compromising its setting and mechanical properties. Hydroxyapatite (HA) with a high aspect ratio and thin nacreous-layered monetite sheets were also synthesized. Nano HA particles with an aspect ratio of 50 can be synthesized by both precipitation and hydrothermal methods. The aspect ratio was controlled via the pH of reaction medium. Thin nacreous-layered monetite sheets were synthesized through a self-assembly process in the presence of an amine based cationic quaternary surfactant. Temperature, pH, and presence of surfactant played essential roles in forming the nacreous-layered monetite sheets. Then the effect from adding silver doped HA and monetite particles was investigated. The results showed that the antibacterial properties of GIC could be increased by incorporating silver doped HA and monetite particles. Further examination showed that the pH change, F ion release, and concentration of released Ag ions were not responsible for the improved antibacterial properties. The quasi-static strengths and compressive fatigue limits of four types of the most commonly used dental restorations were evaluated. In our study, resin modified GIC and resinbased composite showed superior static compressive strength and fatigue limits compared to conventional GIC. The static compressive strength of dental cements increased with the aging time. However, aging had no effect on the compressive fatigue limit of resin modified GIC and resin-based composite. The compressive fatigue limit of conventional GIC even showed a drastic decrease after aging.