1. Poster Templates photog@imvs.sa.gov.au Ionic exchange between Riva Self Cure ® GIC and demineralized dentine Ionic exchange between Riva Self Cure ® GIC and demineralized dentine 1 J McIntyre, 2 J Cheetham, 1 Mulyani D 1 Adelaide University, Australia, 2 SDI Limited, Victoria, Australia Abstract: Objectives: To determine changes in profiles of Ca, P, F and Sr across demineralized dentine following its direct contact with Riva Self Cure GIC using an Atraumatic Restorative Technique (ART) model, and to analyse for any resultant changes in its microhardness. Methods: Six intact extracted human molars had cavities prepared occlusally into dentine. The cavity floors were demineralized for 14 days. Half the cavity floor was painted with varnish from labial to lingual and Riva Self Cure GIC material inserted. The crowns were stored at 37 o C for 14 days in an artificial saliva before being hemi-sectioned vertically from mesial to distal through the restorations. One side of each crown was prepared for Electron Probe Microanalysis of the pre-demineralized dentine from both protected (control) and unprotected (test) floor surfaces. The remaining side was prepared for Microhardness testing of both surfaces. Results: Relative weight percentages (RWP) of Sr and F reached mean peak values of 3.6 and 1.7 respectively in the test side specimens of demineralized dentine. These compared favourably with those found in previous experiments to result after 21 days exposure to Fuji IX (Ngo,2005). The Microhardness of the test side dentine increased proportionally to the peak RWP of Strontium, in comparison to the control values. The Ca/P ratios within the test dentine remained constant throughout, irrespective of the concentrations of Strontium present. Conclusion: Ion exchange between Riva Self Cure GIC and demineralized dentine compares well with that previously observed when Fuji IX was used. A high uptake of Sr results in significantly increased microhardness of the demineralized dentine. The chemical and physical form by which Strontium is present in Introduction: Methods: Table I: Dentine Mineral Content (Ca, P, F and Sr) of Control and Test Samples ( N:6) as determined from measurements of area under profile curves (Student ‘t’ test of significance of difference) Results: Conclusion: Figure 2 Objectives: Figure 1 Ngo (2005) has demonstrated a substantial transfer of strontium (Sr)and fluoride ion (F) from Fuji IX into demineralised dentine using a model simulating both the indirect pulp capping technique and the Atraumatic Restorative method of restoration placement. To determine changes in profiles of Ca, P, F and Sr across demineralized dentine following its direct contact with Riva Self Cure GIC using this model, and to analyse for any resultant changes in its microhardness. Six intact extracted human molars had cavities prepared occlusally into dentine. The crowns were sectioned from roots and all surfaces except he cavity floor painted with nail varnish. The cavity floors were demineralized for 14 days using the ten Cate and Duijsters (1982) artificial caries demineralising solution. Half the cavity floor was painted with varnish from labial to lingual and Riva Self Cure GIC material inserted. The crowns were stored at 37 o C for 14 days in an artificial saliva before being hemi-sectioned vertically from mesial to distal through the restorations. One side of each crown was prepared for Electron Probe Microanalysis (EPMA) of the pre- demineralized dentine from both protected (control) and unprotected (test) floor surfaces. The remaining side was prepared for Microhardness testing of both surfaces. Representative EPMA profiles of Sr, F, Ca and P in both background and test sides of a lesion are presented in Figs 1 and 2. Note that the relative weight percentages (RWP) of Sr and F should be read from the right side of the chart, and Ca and P from the left as viewed. Table 1 presents the mean ‘area under the curve’ data for each element in background and test sides for all specimens. RWP of Sr and F reached mean peak values of 3.6 and 1.7 respectively in the test side specimens of demineralized dentine. These compared favourably with those found in previous experiments to result after 21 days exposure to Fuji IX (Ngo,PhD Thesis; Adelaide University; 2005). Figure 3 shows the mean Vickers hardness readings for test and background sides from all specimens. The difference was not significant at the 0.05 level using the student ‘t’ test of differences. However it was noted that the Vickers microhardness readings of the test side dentine increased proportionally with the peak RWP of Strontium in each specimen, in comparison to the control values. For example, when RWP Sr peaked at 2.5%, there was a slight reduction in hardness. When at 3.5%, there was a 25% increase in Vickers hardness, and when the RWP peaked at 4%, there was a 33% increase. The Ca/P ratios within the test dentine remained constant throughout, irrespective of the concentrations of Strontium present. Ion exchange between Riva Self Cure GIC and demineralized dentine compares well with that previously observed when Fuji IX was used as the restorative material in a simulated ART model. A high uptake of Sr results in increased microhardness of the demineralized dentine. The chemical and physical form by which Strontium is present in the dentine in not known. The data indicate that Riva Self Cure GIC should be a suitable material with which to carry our ART Restorations and indirect pulp capping. Figure 3 GroupCalciumPhosphorusFluorideStrontium MeanSDMeanSDMeanSDMeanSD Control6988.44956.383440.33494.6286.25*28.5843.88+31.60 Test6918.961326.693445.88775.56304.16*102.97648.73+189.72 ( *, + : Significant difference at p< 0.05, as per Student ‘t’’ test of difference)