الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 108 |  |  |
| | | from | 108 | | |
Abstract
The present study aimed to evaluate the influence of the different sizes and tapers of mechanical preparation on root canal cleanliness using different irrigation protocols.
A total of 80 mesiobuccal root canals from the first lower mandibular molars were included. Mesial roots were numbered, equally and randomly assigned into 4 equal groups:
group I: MB canals were instrumented up to a tip size 25, .04 taper using K3XF NiTi rotary files.
group II: MB canals were instrumented up to a tip size 25, .06 taper using K3XF NiTi rotary files.
group III: MB canals were instrumented up to a tip size 30, .04 taper using K3XF NiTi rotary files.
group IV: MB canals were instrumented up to a tip size 30, .06 taper using K3XF NiTi rotary files.
Each group was further subdivided into 2 equal subgroups according to the irrigation protocol:
Subgroup (A): Conventional syringe irrigation:
During instrumentation, each root canal was irrigated using a Max I probe closed-end side vented 30-gauge needle adapted to a disposable plastic syringe inserted 1 mm short of the working length using 5 ml of 5.25% NaOCl for 1 minute followed by the same volume of saline. A final flush with 5 ml of 17% EDTA for 1 minute was used.
Subgroup (B): Ultrasonic activation:
The root canals were irrigated using 5 mL of 5.25% NaOCl which was activated intermittently for 1 minute (3 cycles of 20 s each) and replenishment of the solution was done in between each cycle. An intermediate rinse with the same volume of saline was used. Then, 5 ml of 17% EDTA was activated also intermittently for 1 minute (3 cycles of 20 s each). A final flush with 5 mL of sterile saline solution was performed in each root canal to wash out all irrigant remnants. The roots were then split longitudinally and all root canal thirds were observed through scanning electron microscopy (SEM) to evaluate the presence of smear layer using a scoring system.
Results showed that:
1. When using conventional irrigation technique there was a significantly more smear layer in the apical third, with no differences between the middle and coronal thirds in group I and group III. While in group II the apical level showed the statistically significantly highest smear layer, the middle level showed a significantly lower smear layer and the coronal level showed the statistically significantly lowest smear layer. In group IV there was no statistically significant difference in smear layer removal at different root levels.
2. There was no statistically significant difference between different irrigation groups in smear layer removal at different root levels except when canals were prepared using size 25, 0.06 taper and ultrasonic activation technique was used, where there was statistically significant higher smear layer removal than conventional irrigation technique.
3. There was no statistically significant difference between PUI groups in smear layer removal at different root levels.
4. There was no significant difference in smear layer removal between different tip sizes (25, 30) and different tapers (4%, 6%).
5. There was no significant difference in smear layer removal between different tapers (4%, 6%).
Under the conditions of the present study, the following could be concluded:
- No irrigation technique completely cleared the entire canal system from smear layer, Complete debridement of root canals is a challenge especially in the apical part.
- When the irrigation was ultrasonically activated, smaller preparations resulted in canals that were as clean as larger preparations