Effect of E-Cigarette Liquids on Surface Hardness of Composite Materials

Objectives: The objective of the study is to evaluate the effects of electronic cigarette liquid (e-liquid) on the surface hardness of composite materials.
Methods: Thirty-two composite resin (Amelogen Plus®) specimens were fabricated and were randomly divided into four groups (n=4) according to the number of days of treatment (Day 1, 5, 10, 20). Half of the samples (n=16) were immersed in distilled water and were placed in an incubator at 37 degrees Celsius with 60-70% humidity. The other half (n=16) of the samples were directly applied with Virginia tobacco flavored e-liquid (Black Note, Inc.) with 18mg/mL nicotine content five times per day for ten minutes each time. Surface hardness was measured at the end of Day 1, 5, 10, and 20 at six different locations top and bottom each with a Barcol hardness tester.
Results: A two-way ANOVA and Tukey test were conducted at a significance level of p<0.05 to examine the effect of e-liquid and time over the hardness of composites. There was a statistically significant interaction between the effects of e-liquid treatment and time on the sample’s surface hardness F(3, 24) = 3.298, p=0.037. The analysis further showed that treatment time had a significant impact on surface hardness F(3, 24) = 7.201, p=0.0013.
Conclusions: Composite material shows a significant reduction in surface hardness over time for the control and treatment. Due to the significant interaction between e-liquid treatment and time, we can conclude that e-liquid has a significant effect only after a longer time period (>10 days). However, e-liquid does not show any significant effect on surface hardness over a short time period. Further analysis will be required to see the long-term effects of e-liquid on the dental materials.