Magnesium oxide is slight alkali in water, and may alter the setting characteristics of alginate. Objectives: A purpose of this study was to confirm the influence of MgO on working time and elastic recovery of alginate. Methods: Seven algiantes were manufactured experimentally. Composition of a control group was sodium alginate 15%, sodium phosphate 2%, calcium sulfate 14%, titanium fluoride 3% and diatomite 66% without MgO. MgO was added as 1%, 2%, 3%, 4%, 5%, 6% with decreased diatomite contents for experimental groups. So, number of experimental group was six. P/L ratio was 10g/25cc. Working time was measured on viscosity change charts drawn by Thermal Scanning Rheometer at 25'C. Elastic recovery was measured by method described in ISO 1563. 10 measurements were done for each groups and for each test items. One-way ANOVA and Duncan's test was done between groups. Results: Results are presented as mean and s.d. with unit of min. for working time and % for elastic recovery. * is a control group.
|
Groups |
Working Time |
Duncan's group |
Elastic recovery |
Duncan's group |
|
Control * |
1.75(0.00) |
D |
97.39(0.17) |
A |
|
MgO 1% |
3.12(0.10) |
C |
97.12(0.17) |
A |
|
MgO 2% |
4.36(0.21) |
B |
97.09(0.44) |
A |
|
MgO 3% |
4.25(0.12) |
B |
97.19(0.29) |
A |
|
MgO 4% |
4.25(0.08) |
B |
97.35(0.41) |
A |
|
MgO 5% |
4.18(0.15) |
B |
97.27(0.26) |
A |
|
MgO 6% |
5.11(0.32) |
A |
97.35(0.37) |
A |
Magnesium oxide made working time longer significantly (y=0.4321x+2.5663, r2=0.7243), but did not alter the elastic recovery(p=0.27). Conclusion: These results indicate that magnesium oxide maybe suitable to lengthen the working time without any alteration of elastic recovery of alginates. Lhonam@khu.ac.kr