Objectives: we have developed a low shrinkage resin composite. In the mean time, we have devised an original method for measuring polymerization shrinkage. The aim of this study was to examine and compare the polymerization shrinkage ratio of various resin composites in this method and the ISO draft method, which is considered to be the most accurate way to determine volumetric shrinkage rate.
Methods: six dental composite resins for filling [Experimental composite (GDLS-200, GC), Gradia direct P (GDP, GC), Premise (PR, Kerr corporation), Supreme DL (SU, 3M ESPE), Venus (VE, Heraeus Kulzer) and Estelite sigma quick (ES, Tokuyama Dental) were examined.
In our method, the linear shrinkage rate was determined in difference of sample thickness using CCD Laser Displacement sensor (Keyence corp.) before and after-curing.
The volumetric polymerization shrinkage ratio of resin composite was determined in difference of density between before and after-curing through density determinations in accordance with the buoyancy method (Archimedes' principle). Statistical analyses of linear shrinkage ratio were conducted using one-way ANOVA, and regression analysis was calculated for the results of two methods.
Results: Mean values of polymerization shrinkage ratio including standard deviations were shown as follows; (tests per material; n=5).
| Linear Shrinkage ratio (%) | Volumetric Shrinkage ratio (%) |
GDLS-200 | 1.25 (0.05) | 1.72 |
GDP | 1.62 (0.02) | 2.57 |
PR | 1.35 (0.04) | 2.03 |
SU | 1.74 (0.03) | 2.41 |
VE | 2.19(0.03) | 2.81 |
ES | 1.59(0.04) | 1.95 |
Linear polymerization shrinkage ratio of GDLS-200 was significantly lower than those for other samples (p<0.01). Strong correlativity between Linear and volumetric polymerization shrinkage ratio was shown (p<0.05)
Conclusion: Polymerization shrinkage ratios were different between various resin composites. GDLS-200 has significantly lower linear shrinkage ratio compared to other resin composites.
The result of the method for measuring polymerization linear shrinkage is reliable.