الفهرس 
Evaluation of the Effect of Enlargement of the Apical One Third by Protaper Universal Rotary Files System on Elimination of Enterococcus Faecalis and Surface Irregularities in Single Canaled Premolars. (An in-Vitro Study)
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Abstract
This study aimed to evaluate the effect of the increase in instrumentation size of root canals of extracted single rooted human teeth on Enterococcus Faecalis reduction, remaining debris and surface irregularities in their apical thirds using two different file sizes, F3 and F4 of Protaper Universal rotary system. Regarding E.Faecalis count reduction, twenty four extracted human premolars were collected, prepared and inculated with E.Faecalis. The teeth were then divided into two groups according to file size used (n=12). Mechanical preparation using saline irrigation was carried out up to size F3 (group I), or F4 (group II). Bacterial sampling was done before and after the mechanical preparation. Bacterial assessment was done by means of Colony-Forming-Unit to assess the amount of E.faecalis reduction. For the root canal surface topography and debris assessment, the prepared samples of both groups were longitudinally sectioned, gold plated, and examined under the SEM. Irregularities and remaining debris were then assessed for the apical one third. Irregularities were categorized as either absent, isolated irregularities, partially irregular with grooves, or irregular with grooves. Remaining debris at the apical one third were assessed using the following parameter; absent minimal presence, often present, or present everywhere.The results concerning bacterial reduction revealed that group II (F4), showed a significantly higher E.faecalis reduction than group I (F3) (P=0.025)