Under the conditions of these in vitro leakage studies , it is concluded that smear layer removal improves the fluid-tight seal of the root canal system whereas other factors such as the obturation technique or the sealer , did not produce significant effects
The purpose of this systematic review was to determine whether smear layer removal reduces leakage of obturated human teeth in vitro .
Bacterial retention in canal walls in vitro: effect of smear layer.
When dentin is planed by endodontic instruments , a smear layer forms . Whether this layer should be removed is unknown and controversial . This study was conducted to assess the effect of the smear layer on retention of bacteria using an in vitro root canal bacterial colonization model . Canals of 26 extracted human canines were step-back prepared using 2.5 % NaOCl . Teeth were then r and omly divided into two groups based on the type of high volume final flush : 1 - 20 ml of sterile saline ( 0.85 % wt/vol ) or ( 2 - 10 ml of 17 % EDTA followed by 10 ml of 2.5 % NaOCl which removes smear layer . Streptococcus anginosus ( milleri ) was cultured in trypticase soy broth supplemented with 0.5 % yeast extract at 37 degrees C in 5 % CO2 . Cells were harvested by centrifugation and resuspended in fresh media . Serial dilutions were performed to achieve inocula of 10(6 ) colony-forming units in a 30-microliters volume . Teeth were inoculated and incubated for 2 h in 5 % CO2 at 37 degrees C. Following incubation , teeth were split and processed for microbiological analysis . Numbers of colonizing bacteria were determined by a spiral-plating system . Enumeration of the numbers of bacteria revealed a reproducible , order of magnitude difference ( p = 0.0002 ) between teeth with smear layer ( 10(4 ) colony-forming units ) versus teeth without smear layer ( 10(5 ) colony-forming units ) . This suggests that smear layer produced during root canal therapy may inhibit bacterial colonization of root canals . One suggested mechanism is that smear layer may block bacterial entry into dentinal tubules
Under the conditions of these in vitro leakage studies , it is concluded that smear layer removal improves the fluid-tight seal of the root canal system whereas other factors such as the obturation technique or the sealer , did not produce significant effects
The purpose of this systematic review was to determine whether smear layer removal reduces leakage of obturated human teeth in vitro .