Objective: The aim of the present study is to assess the effect of doxycycline hydrochloride (DH) on smear layer removal on intracanal walls and as antimicrobial agent against selected microorganisms.

Methodology: Twenty freshly extracted human teeth were collected, the teeth were cleaned and washed to remove any debris, calculus attached to it .The crowns of the teeth were sectioned at the cemento enamel junction. Isolated 24 hr colonies of pure cultures grown on mixture of 10% sheep blood agar and Brain Heart Infusion (BHI) agar plates were collected with the help of a wired loop and suspended in sterile 0.85% Nacl solution. The cell suspension was adjusted spectrophotometrically to match the turbidity of a McFarland 0.5 BaSO4 standard. Thereafter the suspension was poured in T C plate 24 wells with the micropippetes and the specimens were dipped in the suspension and kept in the incubator for 7 days at 37*C. The canals were dried by sterile paper points and the swab taken with the help of sterile paper point which is placed in a sterile appentoff filled with .5 ml of saline and then vortexed for maximum leaching of bacteria from the paper point

Scanning electron microscopic evaluation:–

The specimens were scanned as a whole initially and representative photomicrographs were obtained. Each stub of the scanning electron microscope was given a code number to keep record for reference. The apical two–third area was scanned at the 2000x magnification and photomicrographs were taken. The photomicrograph were coded and evaluated in terms of evaluation of the number of open dentinal tubules. The teeth were subjected to SEM analysis to check the effect of the irrigant on the smear layer. Data’s thus obtained were subjected to the statistical analysis using ANOVA test.

Results: This study supports that doxycycline is the irrigating solution for root canals. As it can  open the dentinal tubules and penetrate the surface of dentinal tubule to the deepest layer of dentine and makes the environment aseptic and definitely increase the success rate of root canal treatment.

Conclusion: Doxycycline was found to have better effectiveness against streptococcus pyogenes and enterococcus faecalis whereas it was found less effective against both the staphylococcus aureus, and MRSA(methicillin resistant staphylococous aureus)