In Vitro Evaluating the Effect of an Alcohol-Containing Mouthwash on Surface Roughness of Microhybrid and Nanohybrid Composite Resins Using Atomic Force Microscopy

Recent advances in the improvement of mechanical, physical, and esthetic properties of dental composites have greatly contributed to their increasing use. However, mouthwashes with an alcohol base may adversely affect some properties of composite resins, and cause problems such as discoloration, and composite wear. Considering the increasing use of composite resins, growing demand for esthetics, and increased consumption of mouthwashes, it is imperative to assess the effect of mouthwashes on the physical properties of composite resins, such as their surface roughness. This study aimed to examine the effect of an alcohol-containing mouthwash on the surface roughness of microhybrid and nanohybrid composite resins.

This experimental study was conducted with the code of ethics IR.IAU.DENTAL.REC.1399.049 on 3/24/2019 at the Faculty of Dentistry, Islamic Azad University of Medical Sciences, Tehran. Sixty IPS Empress Direct (Ivoclar) nanohybrid and Vit-l-essence (Ultradent) microhybrid composite resin specimens were fabricated were fabricated with 5 mm diameter and 2 mm thickness. The specimens were immersed in distilled water at 37°C for 24 hours and were then polished with aluminum oxide abrasive discs. The specimens were then immersed in 20 mL of distilled water for 24 hours. After 24 hours, the baseline surface roughness of specimens was measured by atomic force microscopy (AFM). IPS Empress Direct and Vit-l-essence composite specimens were randomly divided into two subgroups (n=15) for immersion in 20 mL of Listerine alcohol-containing mouthwash and Listerine non-alcoholic mouthwash and incubated at 37°C for 24 hours. This protocol simulated the daily use of mouthwash for 2 minutes for a one-year duration. Their secondary surface roughness was measured by AFM. The change in surface roughness of specimens was analyzed and compared by two-way ANOVA and t-test.

The measurement of the initial surface roughness showed higher values in the microhybrid composite than in the nanohybrid composite. The greatest change in surface roughness occurred in the Vit-I-essence micro-hybrid composite following immersion in alcoholic mouthwash; while the smallest change occurred in the IPS Empress nanohybrid composite immersed in non-alcoholic mouthwash. Two-way ANOVA showed that the roughness difference was significant for groups immersed in alcoholic mouthwash, indicating different behavior of the two composite types following immersion in alcoholic mouthwash. The results showed that immersion of composite specimens in mouthwashes increased their surface roughness. However, the change in surface roughness of IPS Empress and Vit-I-essence composite specimens was significantly different following immersion in alcoholic mouthwash, and Vit-I-essence experienced a significantly greater change in surface roughness than IPS Empress.

The surface roughness of both composite types increased following immersion in mouthwashes irrespective of the presence/absence of alcohol. The surface roughness of both composite types after immersion was<0.2 µm, and therefore, clinically acceptable. Listerine alcoholic mouthwash increased the surface roughness of both composite types significantly more than Listerine non-alcoholic mouthwash. The increase in surface roughness of microhybrid composite was greater than that of nanohybrid composite following immersion in alcoholic mouthwash.