Analysis of apical root canal disinfection prepared at three different working lengths with either continuous or reciprocating movement systems and two irriganting substances: in vitro study

Abstract Introduction The preparation of the root canal is fundamental for the success of endodontic therapy, especially the apical third, since it contains the root foramen, where the endodontium and the periradicular tissues communicate. Objective The present study evaluated the contamination of the apical third after the root canal instrumentation in three different lengths, through two types of automated instrumentation (continuous or reciprocating rotating) and two irrigating substances used. Material and method Sixty-six biradicular maxillary premolars were selected, which had their crowns removed and roots separated, totaling 132 specimens. In the first phase, six experimental groups were divided according to the length of instrumentation (before, beyond and in the radicular foramina) and the type of instrumentation (continuous or reciprocating rotatory) with sodium hypochlorite as irrigator. In the second phase the same protocol was repeated, using sodium chloride as the irrigant. In order to confirm the results, two control groups were created: positive and negative, each with six specimens. Result For the same irrigant, no differences were found between the groups with continuous or reciprocating rotational instrumentation in their different working lengths. The groups irrigated with hypochlorite showed no bacterial growth, whereas those irrigated with sodium chloride remained contaminated after instrumentation. Conclusion Mechanical action of endodontic instruments, without bactericidal irrigating substance, does not promote the apical root canal disinfection and the choice of kinematic type of endodontic instruments (continuous or reciprocating rotatory) does not significantly influence the reduction of bacteria within the root canals as well instrumentations ranging from one millimeter before to one millimeter beyond the foramen also did not present differences in the reduction of bacteria in this research.