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Resin Composite Depth of Cure Through Transparent Matrix Materials Used for Injection Molding
N C Lawson1, Z Greene2, N Machado3
1*Nathaniel C Lawson, DMD PhD, UAB School of Dentistry, Division of Biomaterials, Birmingham, AL, USA.
Objectives:
The purpose of this study was to compare the curing light transmittance and depth of cure (DOC) of resin composite through clear polyvinyl siloxane (PVS) impression materials and 3D printed clear matrix materials at various thicknesses.
Methods And Materials:
Cylindrical specimens (n=6) of three clear PVS materials (Affinity Crystal, Clear Bite Matrix, Exaclear) were fabricated in Teflon molds, and two 3D-printed clear matrix materials (Filtek matrix, IDB 2) were printed into specimens of five different thicknesses (2 mm, 4 mm, 6 mm, 8 mm, 10 mm). To measure light irradiance transmittance, specimens were placed on a radiometer (CheckUp), allowing the transmitted irradiance from a light-curing unit (Elipar DeepCure-S, 1450 mW/cm²) to be recorded. DOC of resin composite specimens was measured by placing flowable composite (PVS and IDB 2) or heated conventional composite (Filtek Matrix) into a split metal die with a 4 mm diameter opening. The composite was cured through the different matrix specimens using the Elipar DeepCure-S curing light for the manufacturer's recommended curing time (10 seconds) or double the curing time (20 seconds). The DOC of the composite specimens was measured according to ISO 4049 7.8, and the percentage of total cure (%TC) was calculated by dividing by the total cure (DOC with no matrix and 10-second cure). The correlation between irradiance transmittance and %TC was analyzed with Pearson's coefficient. For each matrix material, the %TC was compared to the total cure of the material using a Dunnett's test. The compressive modulus of each material was measured and compared with a one-way ANOVA.
Results:
There was a statistically significant, strong positive correlation between irradiance transmittance and %TC for 10 seconds (r=0.90 p<0.001) and 20 seconds (r=0.89 p<0.001). There was not a statistically different DOC for the total cure with Affinity (2 mm), Clear Bite (2 mm), Exaclear (2, 4, 6 mm), IDB2 (2, 4, 6, 8 mm), and Filtek Matrix (2,4 mm) if a 20-second cure was used.
Conclusions:
Decreased light irradiance from curing through clear matrix materials decreases the DOC of resin composites. Doubling the curing time when curing through some matrix materials at certain thicknesses allowed a total cure.
