الفهرس 
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Abstract
This study was performed to evaluate some properties of a zinc oxide and eugenol sealer as well as a resin sealer after their modification with ethanolic extract of propolis (EEP) in terms of flow, setting time, film thickness, solubility, antibacterial activity and bond strength. The ease of cleanliness of the root canal walls after obturation was also evaluated.
Propolis was chemically analyzed using gas chromatography/mass spectroscopy (GC/MS), while the measurement of the total flavonoid content was conducted using spectrophotometer.
The liquid of zinc-oxide and eugenol sealer was modified with EEP in a ratio of 1:1 by volume, the powder was then mixed with the modified liquid according to the manufacturer instructions. The resin sealer was modified with EEP in a ratio of 2:1:1 (Base: Catalyst: EEP) according to a pilot study that has been performed.
Flow, setting time, film thickness and solubility of the four groups of root canal sealing materials were evaluated and compared according to the American National Standards Institute/American Dental Association (ANSI/ADA) specification No. 57 for endodontic sealing materials.
The antibacterial activity of the tested sealers was detected by the agar diffusion test against Staphylococcus aureus, Streptococcus mutans, Lactobacillus casei and Enterococcus faecalis.
Shear bond strength was assessed using a universal testing machine (Instron universal testing machine model 3354 instron instruments England) in a push out motion. After the test procedure, fractured surfaces were observed using a stereomicroscope (50X) to determine the failure mode.
Cleanliness of the root canal walls was determined using scanning electron microscope (SEM) 1000x after complete removal of the root canal filling materials using Protaper retreatment universal system.
Independent t-test was used to compare between different tested sealers and the effect of EEP addition for the results of this study that showed a parametric distribution. One Way ANOVA was used to study the effect of different tested groups followed by Tukay’s post-hoc test for pairwise comparison. While, Kruskal Wallis test was used to compare between different tested sealers and the effect of EEP addition for the results that showed a nonparametric distribution. Mann Whitney test was used for pairwise comparison when Kruskal Wallis test was significant.
Zinc oxide and eugenol demonstrated the highest mean value of flow, followed by resin then zinc oxide and eugenol modified with EEP, while resin sealer modified with EEP showed the lowest mean value of flow. The EEP application on both zinc oxide and eugenol and resin root canal sealers resulted in a significant decrease in their flow property.
As regarding setting time, zinc oxide and eugenol modified with EEP showed the highest mean setting time, followed by zinc oxide and eugenol then resin modified with EEP, while resin exhibited the lowest mean setting time. The EEP application on both zinc oxide and eugenol and resin root canal sealers resulted in a significant increase in their setting time.
Results of the mean film thickness showed that resin modified with EEP exhibited the highest mean value, followed by resin then zinc oxide and eugenol modified with EEP, while zinc oxide and eugenol showed the lowest mean value. The EEP application on both zinc oxide and eugenol and resin root canal sealers resulted in a significant increase in their film thickness.
The solubility test showed that zinc oxide and eugenol had the highest mean value, followed by resin then zinc oxide and eugenol modified with EEP. While resin modified with EEP exhibited the lowest mean value. The EEP application on both zinc oxide and eugenol and resin root canal sealers resulted in a significant decrease in their solubility and increase in weight indicating water sorption
The four tested groups and the control (EEP) showed antibacterial activity against the four tested strains. The application of EEP had a statistically significant effect on the antibacterial activity of zinc oxide and eugenol and resin sealers against Staphylococcus aureus and had no statistically significance effect against Streptococcus mutans, Lactobacillus casei and Enterococcus faecalis in both sealers.
Results of the shear bond strength using the push out test in the four tested groups showed that the cervical root section exhibited the highest statistically significant shear bond strength, followed by the middle root section then the apical root section. The EEP application on both zinc oxide and eugenol and resin root canal sealers resulted in a significant increase in their shear strength in all the root sections. These results were supported by the fracture mode analysis.
The descriptive characteristics of the dentinal tubules revealed by the scanning electron microscopic study indicated that zinc oxide and eugenol showed the largest number of clear den¬tinal tubules followed by resin sealer and zinc oxide and eugenol modified with EEP. While, resin modified with EEP, dentinal tubules orifices were filled by the sealer.
Conclusions:
Based on the results of this study as regard of the effect of the modification of zinc-oxide and eugenol and resin based sealers by EEP, it can be concluded that:
1. EEP improved solubility and was combined with water sorption of the sealers.
2. EEP improved bond strength of the modified sealers to dentin.
3. EEP improved the antibacterial activity of both sealers against Staphylococcus aureus, however no improvement was detected against Streptococcus mutans, Lactobacillus casei and Enterococcus faecalis.
4. EEP had a negative effect on flow, film thickness and setting time of the sealers, but still within the accepted ADA specifications.
5. EEP was an obstacle on the cleanliness of the root canal walls that were previously obturated.