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The purpose of this SEM study was to evaluate the cleaning effects of different manual and mechanical endodontic instruments. Sixty single canal human teeth were selected for this study. The root canals were instrumented by seven types of manual endodontic instruments (K-enlargers, K files Rattail files, K-Flexofiles, K Flex files, Hedstrom and NiTi Flex files) and five different mechanical endodontic instruments (Rispi, Rat tail Hedstrom, NiTi Flex files and K-enlargers). During and after the instrumentation, the canals were irrigated by 2.5% sodium hypochlorit. After splitting the roots longitudinally, the amount of debris and smear layer was quantified on the basis of a numerical evaluation scale, using scanning electron microscope. Results were statistically analysed using the Kruskal-Wallis test and t-test. There were no statistically significant differences between hand instrumentation and machine instrumentation with different endodontic instruments for any of the variables tested. Best instrumentation results in removing the smear layer and dentinal debris from the root canal were obtained with Kerr, NiTi and Hedstrom hand files and with K-enlargers, NiTi and Rat-tail mechanical files. In the apical thirds of root canals prepared using hand and mechanical endodontic instruments the smear layer and dentinal debris were always more abundant when compared with the middle and coronal thirds. In conslusion, cleaning efficacy differed slightly among the techniques and instruments, none of them completely removed smear layer and all left some debris.

Abstract Aim The aim of the present study was to assess debris and smear layer remaining following canal preparation with GT rotary instruments. Methodology 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 ×200 and ×1000 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,... [ABSTRACT FROM AUTHOR]

Various instrumentation techniques have been proposed and examined with conflicting results. They include hand and ultrasonic techniques and combinations of the two. In the present study we assesed the effectiveness of four preparation methods for cleaning small, curved root canals, using backscattered-imaging scanning electron microscopy (SEM). The methods were: (i) step-back without initial coronal flaring; (ii) step-back with coronal flaring; (iii) step-back with initial coronal flaring and finished by ultrasonic irrigation and (iv) ultrasonics only. Eighty freshly extracted maxillary and mandibular molars were randomly placed into four treatment groups of 20 teeth each. After preparation, roots were sectioned longitudinally and examined wet by SEM. Each canal was qualitatively evaluated and the groups compared for removal of debris and. smear layer, both overall and at each level (apical, middle and coronal). There were no statistically significant differences between the techniques., either overall or within any of the regions. When comparing regions (regardless of technique) the middle level was. cleaner than the apical or coronal levels. In conclusion, efficacy differed little among the techniques; none of them completely removed smear layer and all left debris. [ABSTRACT FROM AUTHOR]

Bechelli C, Zecchi Orlandini S, Colafranceschi M. Scanning electron microscope study on the efficacy of root canal wall debridement of hand versus Lightspeed™ instrumentation. International Endodontic Journal, 32, 484–493 1999. Aim The aim of this in vitro study was to compare the efficacy of root canal wall debridement following hand versus LightSpeedTM instrumentation. Methodology Twenty recently extracted single-rooted teeth were paired and randomly placed into two treatment groups of 10 teeth each. In group 1, a step-back instrumentation without initial coronal flaring with stainless steel Hedstroem files was used; group 2 was instrumented with Ni-Ti LightSpeedTM instru-ments. Both groups had the same irrigation regimen: 2.5% NaOCl and a 15% EDTA solution. The teeth were then decoronated and each root split longitudinally into two halves to be examined using the scanning electron microscope (SEM). The presence of superficial debris and smear layer was evaluated by a standardized grading system, and the resulting scores submitted to nonparametric statistics. Results Under the conditions of this study, the removal of superficial debris was generally excellent with both canal preparation techniques. Both techniques resulted in variable presence of residual smear layer, with a canal wall covered by smear layer as the predominant characteristic. Generally, the amount of smear layer was greater in the apical than in the middle third of the root, however, this difference was statistically significant (P 0.005) only in hand-instrumented teeth. The use of LightSpeedTM instruments was associated with significantly more (P 0.05) smear layer presence in the middle region of the root when compared with hand instrumentation. In addition, less smear layer was present in the apical region following LightSpeedTM instrumentation than stainless steel hand files, but this difference was not statistically significant.... [ABSTRACT FROM AUTHOR]