Comparison of the Depth of Cure of Flowable Composites Polymerized at Variable Increment Thicknesses and Voltages: An In vitro Study

Abstract

Objectives: The aim of this study is to compare the depth of cure of two composite materials (SDR and Filtek bulk-fill) cured at variable increment depths (2, 4, and 6 mm) and voltages (180 and 220 volts).

Materials and methods: Each sample of the composite material was packed in a mold of 2 mm, 4 mm, and 6 mm and curing light (quartz tungsten halogen) of optimal intensity was exposed for 20 s at 2 different voltages on each specimen. After curing, the specimens were removed and the composite on the nonexposed end was scraped with a plastic instrument. The remaining composite thickness was measured using a digital Vernier caliper. The reading was divided by half to follow the ISO 4049 method. Independent sample t-test, one-way ANOVA, and linear regression analysis were applied. Level of significance was kept at 0.01.

Results: The mean DOC of SDR and Filtek were 1.93 ± 0.82 and 1.77 ± 0.65 mm. Lowering the voltage from 220 to 180 volts reduced the depth of Filtek from 1.87 ± 0.74 to 1.67 ± 0.54 mm, whereas the DOC of SDR remained unchanged at 1.93 mm at the two voltages. The adjusted R ² for the depth of cure was 0.93 when the increment thickness, voltage, and restorative material were taken together in the regression model.

Conclusions: There was no statistically significant difference between SDR and Filtek for the depth of cure at 2 and 4 mm increments. However, at 6 mm increment, the SDR cured significantly deeper than the Filtek. Around 91% variation in the depth of cure of these composites materials is explained by increment thickness alone.

Keywords: Dental composite restoratives; depth of cure; polymerization.

Figure 1

Study flow diagram

Figure 2

Armamentarium of the experiment. (a) Capsules of the Filtek bulk-fill and SDR restorative material. (b) Plastic molds for packing composites (2, 4, 6, 8 mm depth). (c) Voltage converter. (d) Quartz-Tungten– Halogen curing light

Figure 3

Data collection steps. (a) Curing the composite increment. (b) Cured samples of SDR and Filtek bulk-fill 2, 4 and 6 mm. (c) Scraping the composite according to the ISO 4049 method. (d) Measuring the depth of cure with a digital vernier caliper

Figure 4

Depth of cure of the two materials at variable increment thickness. *Independent sample t-test reveals a statistically significant difference at 6 mm increment