الفهرس 
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Abstract
The Aim of this study was to determine the antibacterial efficacy of intracanal medicament formulation calcium hydroxide mixed with iodoform and silicone oil “Metapex” using in vitro model of E.faecalis dentinal tubules infection , at different dentine depths and at two different observation periods “after 24hrs , after 7 days”.
A total of one- hundred human permanent incisors and canines were used in this study. samples were divided into 5 groups equally .each group was divided into 2 sub-groups according to observation period. then ,each sub-group was further sub divided equally into two division according to the depth by using 2 sizes of Gates Glidden burs; a)size #4 b)size #6. 7-mm root cylinder was prepared , the root cementum of each cylinder was removed to create a patency and facilitate the intracanal contamination procedure . The specimens were autoclaved for 30 minutes at 1210c. The specimens were divided into 4 groups of 20 and one negative control group . the tooth specimen together with 1 ml of E.faecalis broth were incubated for 21 days at 370 c in anaerobic chamber. After this period , all tooth sections were washed 3 times with phosphate-buffered saline, then, were placed in sterile Petri dishes , the tested intracanal medicaments were placed in the lumen of the tooth sections , then, the sealed Petri dishes were placed in an incubator at 370 c for 24h then for 7 days.
The antibacterial efficiency was evaluated at two different dentine depths using sterile Gates Glidden burs size # 4, #6 at low speed .
The evaluation was done at 1 day and after 7 days intervals. The dentine powder was collected and mixed with 1ml of freshly prepared Tryptic Soy broth for each tooth specimen and incubated at 370 c for 1 hour .
Three serial dilutions were done (1/10, 1/100, 1/1000), then we cultivated o.1ml on the blood agar plates and incubated for 24hrs at 370 c , finally , after incubation, the total colony forming units “cfus” were counted.
Results:
The results showed that all the tested materials had high mean of colony forming units “ cfus” of recovered bacteria by using the two sizes of Gates Glidden burs.
Statistically there was highly significant different between the experimental groups and the positive control group at two different observation periods.
In general, there was high statistical significance between the tested materials at the different observation periods at 1 day , after 7 days, also at the two different dentine depths by using two sizes of burs. There was high statistical difference between groupI ‘pulpdent Paste’ and group II “Ca(OH)2 gutta percha points” after 7 days by using the two burs.
There was high statistical difference between the group I and group III (Metapex) after 7 days mainly by using the Gates Glidden size #6.
There was high statistical difference between the group II and group III at both observation periods using the two sizes of burs.
In case of Pulpdent ,there was statistical significance between the two observation periods by using size #4 Gates Glidden bur.
No statistical difference was found between the two different observation periods by using Gates Glidden size #6
In case of group ‘Metapex’’ there was a highly statistically significance between the two different periods by using the Gate Glidden size #4 . On other hand, there was statistical significance between the two different periods by using Gates Glidden size #6.
There was no statistical difference between the two sizes of gates Glidden used after 7 days in case of group I or group II.
In case of Metapex , there was no statistical difference at the first day between the two sizes of burs used . After 7 days , there was high statistically difference between the two sizes of the burs used.
Conclusion:
Under conditions of this study we can concluded that:
1- The effect of time on the antibacterial activity of the tested materials was very important. in case of Ca(OH)2 gutta percha points , short time application “ 24hr” was very effective for release of hydroxyl ions and elimination of E.faecalis.
2-The type of intracanal medicament vehicle has a very important role in dissociation of Ca(OH)2 into hydroxide ions and calcium ions which in turn important for its antibacterial activity.
3-Group I “ Metapex” was more effective than Ca(OH)2 gutta percha points or Pulpdent paste for disinfection of dentinal tubules infected with E.faecalis after 7 days.
4-GroupI I “ calcium hydroxide gutta percha points” are not useful therapeutic dressing materials for delivery of calcium hydroxide as an effective intracanal antibacterial agent .
5-The presence of Ca(OH)2 in paste formulation as in case of group III“ Pulpdent paste” allows formation of a more stable physical barrier which remain in the root canal for a longer period and thus delay recontamination.
6-E.faecalis is still the most resistant micro-organism to various forms of calcium hydroxide intracanal medicament that had been used in this study.
7-E.faecalis had been recovered at different dentine depths whatever using size #4 or size #6 Gates Glidden burs .
8-24hr observation period was very short duration for evaluation of antibacterial activity , But , 7 days observation period was valuable for release of hydroxyl ions and better evaluation of antibacterial activity .This was true especially with GroupI“Metapex” and Group III “pulpdent paste”.
9-The use of intracanal medicament between the root canal therapy appointnents is a must for elimination of micro-organisms between the subsequent sessions and delay recontamination .
Recommendation:
Further “in vivo” studies can be employed for evaluation the antibacterial activity of the Metapex at different dentine depths and at different observation periods.