Surface properties and the bioactivity of glass-ionomer dental cements and related materials

The improvement and modification of the surface hardness of glass-ionomer dental cements was investigated in the studies discussed in this thesis to allow the range of clinical applications of these cements to be extended. Storing the cements in non-aqueous media whilst heating at 60 oC increased the surface hardness compared to storage in water at 37 oC. The corresponding compressive strength showed no significant changes. \n \nThe bioactivity of two commercially available glass-ionomer dental cements was investigated after it was established that the surface hardness of a dental cement was improved by storing the materials in biologically natural bovine milk. In particular the observations of the appearance of the surface were noted as well as cation release studies and calcium to phosphorus ratios calculated. The results indicated that a surface layer of calcium phosphate had formed and created a barrier around the cement preventing the loss of strengthening ions. \n \nAn investigation was also made into formulating a novel hybrid cement. This process included the deployment of additives/co-reactants within the cement formulation. By incorporating zinc phosphate into a strontium based glass-ionomer elevated levels of fluoride release were obtained when compared to the original commercially available glass-ionomer. SEM images show that this additive had an effect on the surface morphology of the glass. The bioactivity studies performed on these cements show the uptake of calcium over one week, indicating that there is the possibility that these new hybrid cements are bioactive. Refinement of the new hybrid materials has produced cements with antimicrobial properties as well as higher surface hardness values than the original glass-ionomer.