الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
The aim of the present study was to evaluate and compare the dentin micro-hardness, dentinal erosion, push out bond strength of resin sealer to dentin and antibacterial efficiency against E.faecalis after irrigation with sodium hypochlorite followed by grape seed extract solution versus irrigation with sodium hypochlorite followed by EDTA.
A total of 46 teeth were distributed according to testing methods into 3 main testing groups as follows; 16 teeth for dentin micro-hardness evaluation, 12 teeth for push-out bond strength test and 18 teeth for antibacterial efficiency test.
Regarding dentin micro-hardness test; each tooth was sectioned vertically into 2 halves giving 32 specimens which were divided into 2 groups; intervention and comparator groups; 16 specimens each according to the irrigation protocol. The dentin micro-hardness evaluation was performed for each specimen before and after irrigation at 3 thirds; coronal, middle and apical thirds. Two representative specimens were taken from each group for scanning electron microscope evaluation.
On the other hand, for bond strength evaluation 12 teeth were divided into 2 groups; 6 teeth each according to the irrigation protocol. Then each tooth was segmented into 3 thirds giving 18 specimens for each group which were further subdivided into 3 subgroups; coronal, middle and apical (n=6). For evaluation of antibacterial efficiency; 18 teeth were divided into 2 groups, 9 teeth each according to the irrigation protocol.
For evaluation of the effect of the two irrigation protocols on the root dentin micro-hardness, the VHN of 32 root half specimens (16 specimens for each group); were measured before and after exposure of the corresponding irrigant protocol. The results revealed that there was a significant reduction in the micro-hardness values of all the test groups after irrigation. Moreover, the irrigation with the comparator irrigation protocol (5.25% NaOCl+ 17% EDTA) caused significantly higher percentage reduction compared to the irrigation with the intervention irrigation protocol (5.25% NaOCl+ 13% GSE)
Four representative specimens from micro-hardness specimens (2 from each group) after treatment were analyzed for dentin surface examination for dentinal erosion using Scanning electron microscope (SEM). The result exhibited that the intervention irrigation protocol showed mild erosion and all tubules looked normal in appearance and size. While treatment with comparator irrigation protocol showed moderate to severe erosion where the peritubular and intertubular dentin were destroyed and some dentinal tubules were connected to each other.
In order to evaluate the effect of the two irrigation protocol on the push-out bond strength values of the resin sealer to root dentin, a total of 12 teeth were randomly divided into two groups and mechanical root canal preparation was performed coupled with application of the corresponding irrigant protocol for each group. Obturation was performed by means of lateral condensation technique with gutta percha and AH plus root canal resin sealer. Thermocycling of the specimens were then performed by subjecting the specimens to 3500 cycle between 5 ° and 55 °C. The immersion time was 30 seconds while the dwell time was 2 seconds. Each root was then horizontally sectioned into three sections; coronal, middle and apical to obtain segments of a standardized thickness of 2mm each. The specimens were then aligned over the universal testing machine’s support plate in an apical to coronal direction and push-out tests were performed by applying a compressive load to the apical aspect of each slice.
Results of the push-out bond strength test revealed no significant difference in the push-out bond strength values (MPa) of resin sealer to coronal, middle and apical radicular dentin between the intervention (5.25% NaOCl+ 13% GSE) and comparator (5.25% NaOCl+ 17% EDTA) irrigation protocols. Moreover, the push out bond strength value in the apical third of the intervention group was significantly higher than that in the coronal third and the middle third.
A total of 18 teeth (9 teeth in each group) were used to evaluate the antibacterial efficiency of the test groups against a standardized strain of E.faecalis suspension (ATCC 29212) using agar dilution method. Results revealed that both the intervention (5.25% NaOCl+ 13% GSE) and the comparator (5.25%NaOCl+ 17%EDTA) irrigation protocols showed no significant difference in the bacterial CFU/mL and percentage reduction in the bacterial CFU/mL. Moreover, the bacterial CFU/mL was significantly decreased after irrigation with the intervention and the comparator irrigation protocols that there was no significant difference between the groups.