A scanning electron microscopic study of debris and smear layer remaining following use of GT rotary instruments.
OBJECTIVE
The aim of the present study was to assess debris and smear layer remaining following canal preparation with GT rotary instruments.


METHODS
Sixteen freshly extracted single-rooted premolar teeth were instrumented with GT rotary instruments using a crown-down preparation technique. All specimens were flushed with 2 mL of 5% NaOCl between each rotary instrument. At the end of instrumentation the following final irrigation sequence was repeated two times: 2 mL of EDTA + Cetrimide for 1 min (Largal Ultra, Septodont, France) and 2 mL of 5% NaOCl for 5 min. A final flush with saline solution was made to halt any chemical activity. Two other uninstrumented teeth that were not irrigated served as controls. All teeth were split longitudinally and prepared for SEM evaluation. The presence of debris and smear layer was evaluated from photomicrographs at x200 and x1000 magnification taken in the apical, middle and coronal thirds of the canals. Blind evaluation was performed by two trained observers and scores were compiled separately. A five category scoring system for debris and smear layer was used. Values obtained were tabulated and statistical analysis was carried out using a parametric chi-squared test.


RESULTS
Statistical analysis showed that there was no significant difference between the three regions of the root canals (P > 0.05) for debris. Comparison of the removal of the smear layer between the three regions showed that there was a statistically significant difference between all parts, especially between the coronal and apical thirds (P < 0.001). Overall, the coronal sections were cleaner than the middle and apical sections. The uninstrumented canals showed walls completely covered with tissue, confirming that specimen preparation alone did not remove tissue.


CONCLUSIONS
Under the conditions of the present study GT rotary instruments removed debris effectively, but left root canal walls covered with smear layer, particularly in the apical third.
Gambarini
G
G
Department of Periodontics-Endodontics, University of Rome, 'La Sapienza', Rome, Italy.
Laszkiewicz
J
J
D001641:Bicuspid; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000627:therapeutic use; D016009:Chi-Square Distribution; D003786:Dental Pulp Cavity / Q000648:ultrastructure*; D004492:Edetic Acid / Q000627:therapeutic use; D004867:Equipment Design; D006801:Humans; D008855:Microscopy, Electron, Scanning; D015588:Observer Variation; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D016369:Smear Layer; D012965:Sodium Chloride; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D013223:Statistics as Topic
D002593:Cetrimonium Compounds; D012388:Root Canal Irrigants; D012965:Sodium Chloride; D004492:Edetic Acid; D012973:Sodium Hypochlorite; D000077286:Cetrimonium