الفهرس 
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Abstract
The aim of the present study was to investigate and compare between the antimicrobial effect of three intracanal pastes on microorganisms located in necrotic primary molars.
These pastes were:
• Calcium hydroxide mixed with iodoform (Metapex) mixed with propolis.
• Zinc oxide eugenol mixed with propolis.
• Propolis paste.
Thirty five healthy children of both sexes with age range 4-8 years old were selected from the outpatient Pediatric Dentistry clinic, faculty of Dentistry Ain Shams University.
These children were complaining from necrotic primary molars that required pulpectomy procedure. This study was approved by the ethical committee of faculty of dentistry Ain Shams University. The aim of the study and the procedure of samples collection were detailed verbally to the patients and their care givers. An informed consent was taken from parents and caregivers of the participants before the commencement of the study.
The study consisted of clinical phase and microbiological phase.
Clinical phase
I. Clinical procedure:
A detailed medical, dental history and history of antibiotic use was recorded before the collection of the samples. Pre-operative periapical radiograph was done on each selected molar to assess the case and to determine the working length.
After partial isolation of the tooth, all carious tooth structure was removed then access cavity was formed. According to the radiographic measurements, the canals were prepared using endodontic files .The working length was established 1 to 2 mm short of radiographic length in order to avoid overextension. The canals were enlarged up to minimum final size of 30 to 35. No antiseptic irrigating solution was used until the samples were collected.
II. Bacterial samples collection:
For samples collection sterile absorbent paper points #30-35 compatible with root canal diameter up to the working length, were introduced into the most accessible root canals and left for approximately one minute. Then the paper points were removed from the canals and introduced in BHI transport medium. The tube was tightly closed and the microorganisms that grew in the medium were stored.
III. Pastes preparation:
Paste1: mixture of propolis (EEP) and metapex prepared with paste consistency by mixing 10 mg EEP with 120 mg metapex …………………………………………………….(Study group 1).
Paste 2: mixture of propolis (EEP) and zinc oxide eugenol prepared with paste consistency (2gm zinc oxide powder :
1gm propolis : 1ml eugenol)…………………..(Study group 2).
Paste 3: Ethanol extract of propolis paste prepared by mixing
10 g of propolis to 100 ml of solvent (ethanol 80%v/v), ……………………………………………………...(Study group 3).
Paste 4 : Metapex ( Calcium hydroxide mixed with iodoform) ……………………………………………………(Control group 1).
Paste 5: Zinc oxide and eugenol prepared according to manufacturer instructions by mixing three scopes of zinc oxide powder with four drops of eugenol………………(Control group 2).
Microbiological phase
IV. LABORATORY PROCEDURE
It involved two phases:
A. Identification of bacterial morphotypes from necrotic pulp samples
Bacterial morphotypes from each sample were directly determined by gram staining to identify the most predominant organism found in each sample.
B. Antimicrobial activity test:
The agar-well diffusion technique was used to determine the antimicrobial activity of the experimental pastes against the root canal samples. The inoculum was prepared with an overnight culture of root canal samples in an anaerobic atmosphere at 370c. Then after confirming bacterial growth, Mueller hinton agar was inoculated with the bacterial suspension.
Each plate was divided into five portions, according to the previously mentioned pastes numbers, in which five equidistant wells 5 mm in diameter and 4 mm deep were done in each plate. The wells were completely filled with the test materials using sterile syringes. Plates were incubated in an anaerobic jar at 370c for 48 hours.
Antimicrobial activity was determined by measuring the diameters of polymicrobial growth inhibition zones around each one of the five pastes in millimeters
Results
Statistical analysis of different types of bacteria collected from samples revealed that Gram positive cocci were present in 30 samples with percentage of 85.7% of the samples, while gram negative bacilli were present in 20 samples with percentage of 57.1% and Gram positive bacilli were present in 3 samples with percentage of 8.6%. The presence of bacteria in the samples showed statistical significant difference.
Results showed that there was a statistically significant difference between inhibition zone diameters of the different paste types (P-value <0.001). Pair-wise comparisons between the paste types revealed that there was no statistically significant difference between Paste 2 (EEP + ZOE) and Paste 5 (ZOE); both showed the statistically significantly highest mean inhibition zone diameter values. There was no statistically significant difference between Paste 1 (EEP + metapex), Paste 3 (EEP) and Paste 4 (metapex); all showed the statistically significantly lowest mean inhibition zone diameter values.