Evaluation of Some Properties of Two Types of Bonding Agents After Modification with Ethanolic Extract of Egyptian Propolis

Abstract

This study was performed to evaluate the antibacterial activity and bond strength of two types of bonding agents after their modification with ethanolic extract of propolis (EEP). The Egyptian propolis used was chemically analyzed using gas chromatography/mass spectroscopy (GC/MS) and the total flavonoid content was measured using a spectrophotometer.The two bonding agents used were both two-step etch-and-rinse adhesives but with different solvents; ethanol and acetone. The bonding agents were modified with different ratios of EEP; the bonding agent to EEP ratios were 2:1, 1:1, and 1:2. These ratios were used based on a pilot study that was performed.The antibacterial activity of the bonding agents was tested using the agar disc diffusion test against the cariogenic bacteriaStreptococcus mutans and Lactobacillus caseai.The shear bond strength was assessed using the universal testing machine (Instron universal testing machine model 3354 Instron instruments, England) in a push-out motion. The specimens were then observed using a stereomicroscope (50X) to determine the mode of failure.The resin/dentin interface was evaluated using the scanning electron microscope (1500X) (Quanta 250 FEG (Field Emission Gun) attached with EDX Unit (Energy Dispersive X-ray Analyses) FEI company, Netherlands).The results were assessed using the Shapiro-Wilk test for normality and most of the data was normally distributed. The antibacterial activity and bond strength were described in terms of mean, median, standard deviation (SD) and range. The parametric data was then compared using paired t-test and the non-parametric data was compared using Mann-Whitney U-test.The mode of failure was described in terms of frequency and percentages. Spearman’s correlation coefficient was calculated to assess the relationship between the shear bond strength and mode of failure. In the antibacterial testing against Streptococcus mutans group B4 (acetone-based bonding agent to EEP 1:2) gave the largest inhibition zone followed by B3, B2, EEP, B1, A4, A3, A2 and A1. In Lactobacilli caseai group B3 gave the largest inhibition zone followed by B4, EEP, B2, B1, A4, A3, A2 and A1.The shear bond strength in a push-out motion was used to assess if the modification of the bonding agents with EEP would adversely affect the bond strength. Ethanolic extract of propolis was found to enhance the bond strength when added to the ethanol-based bonding agent in group A2 (ethanol-based bonding agent to EEP 2:1). The highest bond strength value was in group A2 followed by A1, B1, A3, A4, B2, B3 and then B4.The resin/dentin interface was evaluated using a scanning electron microscope (1500X). Resin tags were seen in all the groups but the number, frequency and thickness varied. Groups A1, A2 and B1 showed a large number of thick resin tags that covered the surface, while groups A3, A4, B2, B3 and B4 showed a small number of thinner resin tags.