الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
The purpose of this study was to compare the shaping ability and cleaning efficiency of two of the most popular rotary Ni-Ti instruments: ProTaper and RaCe systems.
Methodology A total of fifty extracted permanent human mandibular molars with mesiobuccal canal curvature between 30o and 45o and radius of curvature between 2-7mm, were used in this study. The mandibular molars were equally divided into two groups; twenty-five canals for each. Pre- and post-operative radiographs for both mesio-distal and bucco-lingual aspects were taken using direct digital radiography (Digora). Based on the radiographs taken after instrumentation with the master apical file inserted into the root canal, the following parameters were determined; the degree of canal straightening, canal transportation and centering ratio. Canal transportation and centering ratio were evaluated at five specific positions along the canal length, by measuring mesial and distal dentine thicknesses and following the formulas used by (Gambill et al 1996) (1). 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 (SEM). Canal wall cleanliness was evaluated at apical, middle and coronal thirds of the root canal.
Results Regarding the shaping ability, results showed that there was no statistically significant difference between the ProTaper and RaCe systems in either the degree of canal straightening or canal transportation. However, Mann-Whitney U test revealed that at the level of end of preparation (EP), ProTaper showed a statistically significant higher mean centering ratio than RaCe (P < 0.05). Regarding the cleanling efficiency,
there was no statistically significant difference between the two systems in terms of debris and smear layer at all levels (P > 0.05).
Conclusion: Both ProTaper and RaCe rotary systems are safe and efficient in shaping curved root canals. They maintained the canal curvature and remain centered in the canal with minimal transportation risk. Concerning the cleaning efficiency, both systems produced a relatively clean dentine surfaces at the middle and coronal thirds with the highest debris and smear layer scores at the apical third. This highlights the importance of irrigation as crucial for sufficient disinfection of the root canal system.