Efficacy of the self-adjusting file system on cleaning and shaping oval canals: a microbiological and microscopic evaluation.

INTRODUCTION

The shaping ability of root canal instruments is determined by a complex interrelationship of parameters such as cross-sectional design and the ability to remove debris and the smear layer. The self-adjusting file (SAF) consists of a hollow, flexible instrument in the form of a compressible, thin-walled, pointed cylinder. The aim of this study was to compare the SAF with the ProTaper rotary file system, evaluating debris and smear layer removal and the presence of bacteria by using microbiological and scanning electron microscopy (SEM) evaluation.

METHODS

Fifty maxillary premolars were inoculated with Enterococcus faecalis for 30 days and then randomly distributed into 2 groups. Group 1 was prepared with ProTaper rotary instruments and irrigated with 30-gauge side-vented needles. Group 2 was prepared by using the SAF system with continuous irrigation. Bacteriologic samples were taken before and after preparation. All samples were then longitudinally split and analyzed under scanning electron microscopy. The scoring was carried out by 3 blinded evaluators.

RESULTS

In group 1, 40% of samples had negative cultures with postinstrumentation samples taken with paper points (S2a) and 45% with postinstrumentation dentin samples (S2b). In group 2, 20% of samples had negative cultures with S2a and 15% with S2b. Intragroup analyses evaluating the reduction in the number of colony-forming units (CFUs) from S1 to S2a and S2b demonstrated both preparation techniques were highly effective (P < .01). Further reduction of CFUs was observed when comparing S2a and S2b in group 1 (P < .05), whereas no difference was observed in group 2. Intergroup analysis demonstrated a statistically significant difference of CFUs at S2a and S2b (P < .05). SEM scores were consistent with the microbiology findings.

CONCLUSIONS

The SAF system does not allow control of the apical enlargement, thus limiting the ability of the irrigants to achieve effective and predictable disinfection.