the ultimate goals of endodontic treatment are complete removal of bacteria , their byproducts , and pulpal remnants from infected root canals .
endodontic medicaments have been thought to be an essential step in killing the bacteria in root canals .
calcium hydroxide is the most widely used medication because of its well - documented antibacterial activity which can be use in various combinations . among these combinations metapex
( meta biomed co. ltd , cheongju , korea ) , a silicone oil - based calcium hydroxide paste containing 38% iodoform is very commonly used .
metronidazole has a wide spectrum of bactericidal action against oral obligate anaerobes , even against isolates from infected necrotic pulps , in fact , more than 99% of the bacteria found in carious lesions and infected root dentine .
biopure mtad ( dentsply tulsa dental , tulsa , ok ) is a mixture of a tetracycline isomer , an acetic acid , and tween 80 detergent ( mtad )  was designed to be used as a final root canal rinse before obturation .
it represents an innovative approach in simultaneous removal of endodontic smear layers and disinfection of root canals .
biopure mtad has been shown to be a clinically effective and biocompatible endodontic irrigant with potential antibacterial substantivity .
aztreonam , a monobactem , has been successfully used in medical field since long time as an antibacterial due to its high affinity against gram - negative bacteria .
this study was undertaken to evaluate the antimicrobial efficacy of metapex , metronidazole , biopure mtad and azetronam on bacteroides fragilis ( gram - negative strict anerobe ) and propionibacterium acne ( gram - positive strict anerobe ) .
the micro - organism employed in this study were two obligate anerobic bacteria i.e. , b. fragilis ( atcc 25285 ) and p. acnes ( atcc 6921 ) .
these strains were allowed to reactivate in media which contains brain heart infusion broth ( bhi ) ( difco co , becton dickinson , sparks , md ) supplemented with hemin ( 5 mg / l ) and menadione ( 0.5 mg / l ) .
biopure mtad ( dentsply tulsa dental , tulsa , ok ) prepared after mixing biopure mtad powder with the diluents as manufactures instruction .
metapex ( meta biomed co. ltd , cheongju , korea ) solution prepared by dissolving metapex in ethanol ( 99.9% ) , by heating until it completely dissolved ( 0.22 mg / dl conc ) .
other antibiotic discs used were of aztreonam and metronidazole from bd diagnostic . after revival of the organisms in about 48 hours , inoculum for each bacterial strain was prepared by picking up four to five colonies with the help of a circular , previously sterilized loop and dissolving them into respective test tube containing 5 ml of 0.85% saline solution - to produce a turbidity of 0.5 on mcfarland scale ( 1.5  108 cfu / ml ) .
these organisms were streak on wilkins - chalgren agar plate ( difco , becton - dickinson and co. ) in a form that lawn growth can be observed .
antibiotic discs and control discs were then aseptically transferred to the agar plate previously inoculated with bacteria .
plates were than incubated for 48 hours at 37c in an anerobic jar with mixture of gas ( n2 , h2 , and co2 used ) .
the values were statistically evaluated with one - way anova and the intergroup comparison was performed with the bonferroni multiple comparison test .
biopure mtad ( dentsply tulsa dental , tulsa , ok ) prepared after mixing biopure mtad powder with the diluents as manufactures instruction .
metapex ( meta biomed co. ltd , cheongju , korea ) solution prepared by dissolving metapex in ethanol ( 99.9% ) , by heating until it completely dissolved ( 0.22 mg / dl conc ) .
after revival of the organisms in about 48 hours , inoculum for each bacterial strain was prepared by picking up four to five colonies with the help of a circular , previously sterilized loop and dissolving them into respective test tube containing 5 ml of 0.85% saline solution - to produce a turbidity of 0.5 on mcfarland scale ( 1.5  108 cfu / ml ) .
these organisms were streak on wilkins - chalgren agar plate ( difco , becton - dickinson and co. ) in a form that lawn growth can be observed .
antibiotic discs and control discs were then aseptically transferred to the agar plate previously inoculated with bacteria .
plates were than incubated for 48 hours at 37c in an anerobic jar with mixture of gas ( n2 , h2 , and co2 used ) .
were statistically evaluated with one - way anova and the intergroup comparison was performed with the bonferroni multiple comparison test .
tables 1 and 2 show the diameters ( means and standard deviations ) of the zones of microbial growth inhibition ( in mm ) for the tested materials against b. fragilis [ figure 1 ] and p. acne , respectively .
comparision of the antimicrobial effect of endodontic medicaments against bacteroides fragilis comparision of the antimicrobial effect of endodontic medicaments against propiobacterium acne zone of inhibition against b. fragilis by aztreonam , metronidazole and metapex metronidazole show the largest zone of inhibition size against both b. fragilis and p. acne . according to bonferroni
test significant differences in zone of inhibition size against b. fragilis were found between biopure mtad and metronidazole ( t = 4.83 , p < 0.01 ) , zone of inhibition was non - significant for biopure mtad and metapex ( t = 0.37 , p > 0.05 ) and biopure mtad and aztreonam ( t = 2.23 , p > 0.05 ) .
according to bonferroni test significant differences in zone of inhibition size against p. acne were found between biopure mtad and aztreonam ( t = 58.44 , p < 0.001 ) , biopure mtad and metronidazole ( t = 7.31 , p < 0.001 ) .
the selection of the test endopathogens for this study was arbitrary and not a random sampling from necrotic teeth .
nevertheless , an attempt was made to select representative bacteria that have been commonly isolated from necrotic canals .
agar disc - diffusion test method is a well - established technique for antibacterial study .
advantage of this method is that chemical properties of the medicaments are not changed and the antimicrobial resistance can be detected by challenging bacterial isolates with antimicrobial discs .
moreover , this is an easy and less technique - sensitive method . in the present study , antimicrobial efficacy of medicaments
were tested against b. fragilis because it is a gram - negative anerobic bacilli , commonly isolated bacteria in endodontic infections . in previous studies ,
p. acnes has been identified among the microfiora of endodontic infections which is the cause of its selection in the present study .
metapex in this study , showed antimicrobial effect against both b. fragilis and p. acnes which is an agreement with previous studies .
the antimicrobial effects of metapex may be due to the combination with iodoform and the viscous and oily vehicle , which may prolong the action of the medicament .
accordingly , gomes et al . , showed that oily vehicles increase the antimicrobial effects of calcium hydroxide which might be the reason of effect on p. acne .
calcium hydroxide usually increases ph and allowed an unfavorable microenvironment to the growth of b. fragilis strains .
metronidazole has shown effect against both b. fragilis and p. acne , which is in accordance with previous studies .
this action requires intracellular reduction of the nitro group of these prodrug to produce reactive radical species .
biopure mtad in this study has shown significant zone of inhibition against both b. fragilis and p. acne which might be due to presence of doxycycline ( broad - spectrum antibiotic ) , as shabahang et al .
previous literatures have proved the effect of doxycyline on b. fragilis and p. acne , by inhibiting the protein synthesis .
aztreonam is a novel monocyclic 1-lactam antibiotic which is highly active against aerobic gram - negative bacteria in vitro and in vivo .
it is relatively inactive against gram - positive organisms , such as staphylococcus aureus but it is little effective against b. fragilis which is in accordance with the present study .
aztreonam has shown significant effect on b. fragilis but it has low efficacy than metronidazole but higher efficacy than other endodontic medicaments .
metronidazole showed maximum antimicrobial efficacy against b. fragilis followed by azetronam , metapex , biopure mtad in descending order .
antimicrobial efficacy against p. acnes was again shown maximum by metronidazole followed by biopure mtad and metapex .
 aim : the purpose of this study was to evaluate the comparative antibacterial efficacy of biopure mtad , metapex , metronidazole , and aztreonam against two obligate anerobic bacteria.materials and methods : antimicrobial efficacy of selected medicaments against two obligate anaerobic bacteria bacteroides fragilis and propionibacterium acnes was done by agar disc - diffusion method . pre 
 - sterilized whatman paper discs , 6 mm in diameter and soaked with the test solution , were prepared and placed onto the previously seeded agar petri plates . 
 each plate was incubated in anaerobic jar for anerobic environment at 37c for 48 hours . 
 a zone of inhibition was recorded for each plate and the results were analysed statistically . saline and ethanol used as control group in this study.results:biopure mtad , metapex and metronidazole were effective against all the selected microorganisms . 
 aztreonam was effective against bacteroides fragilis . 
 saline and ethanol used as control were ineffective.conclusions:metronidazole showed the superior antibacterial property amongst the tested medicaments . 
INTRODUCTION
MATERIALS AND METHODS
Antibiotic preparation
Antibiotic discs preparation
Data analysis
RESULTS
DISCUSSION
CONCLUSIONS