Preventing Reinfection of the Root Canal with Endodontic Irrigants

Objective:

Both doxycycline and chlorhexidine are known to bind to root canal dentin.  The goal of this study is to determine if the amount of compound bound to the dentin is capable of preventing re-infection of the root canal.

Methods:

The two endodontic irrigants tested in this study were MTAD, a doxycycline-based irrigant, and Endo-CHX, a chlorhexidine based irrigant.  Standardized root canal spaces were prepared by instrumenting extracted human anterior teeth with a 1.2 mm diameter reamer and followed by sectioning into pieces 8 mm in length using a diamond disc.  The outer surfaces of the sections were then coated with 3 layers of nail polish. The canals were then autoclaved, one side of the root canal sealed with sterile wax, and then irrigated using one of three treatments.  The MTAD and Endo-CHX groups were irrigated according to their manufacturer’s instructions.  The positive control group was irrigated with only NaOCl and EDTA.  After irrigation, each section was infected with approximately 10 uL of tryptic soy broth containing about 10⁶ CFU of  Enterococcus faecalis (ATCC 4082).  The broth was changed every 24 hours.  The presence of viable CFU in the dentin was determined every 24 hours by rinsing the canal with sterile broth, enlarging the canal with a 1.4 mm diameter reamer, and plating aliquots of the dentin shavings collected.

Results:

The number of samples displaying growth were as follows:

Time (hrs)	Endo-CHX	MTAD	Positive Control
24	0/5	4/5	5/5
48	2/5	5/5
72	5/10	9/10

Endo-CHX significantly prevented re-infection of the root canal after 24 hours (P = 0.008)

Conclusions:

Unlike MTAD, Endo-CHX was capable of preventing re-infection of the root canal.