الفهرس 
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Abstract
This study was conducted to correlate between the fracture resistance and the percentage of filled area of root canals which were filled with different root canal sealers and obturation techniques.
A total of 80 human intact mandibular premolars with single root canals were used in this study. Decoronation was done to a standard length of 13±1mm. Instrumentation was done using Fanta rotary files till 40 taper 4%. Samples were divided into two experimental groups (A, B) (n = 40) according to the obturation technique used (lateral compaction & single cone). Each group was further divided into two subgroups (1, 2) according to type of sealer used (AH Plus & Totalfill) (n=20). Each sub group was further subdivided according to the method of evaluation being carried out as fracture resistance (n=10) and percentage of root filled area (n =10).
For evaluation of fracture resistance; universal testing machine was used after simulation of periodontal ligaments and bone. The mean value of fracture resistance for each sealer was calculated. For the evaluation of percentage of filled areas of root canals; roots were horizontally sectioned using microtome saw at apical, middle and coronal thirds, after being embedded in acrylic resin and examined using digital stereomicroscope and measured by a ruler tool in image J software. The value of gutta-percha, sealer and voids was calculated and converted into percentage. Data was collected and statistically analyzed.
Results showed that roots obturated with Totalfill showed statistically significantly higher mean fracture resistance (356 70.9) than AH Plus. Regardless of the sealer, single cone obturation technique showed statistically significant higher mean fracture resistance (401.5±31.7) than lateral compaction technique.
There was no statistically significant difference between fracture resistance of samples obturated with Totalfill BC sealer and AHplus resin sealer using lateral compaction technique which was lower than the same sealers with single cone technique.
Regarding the percentage of filled area, higher percentage of gutta percha with both sealers was calculated using lateral compaction technique than single cone technique while the amount of sealer was higher with single cone technique. More gaps were observed in samples which were obturated using lateral compaction technique. More gaps were observed at the apical level of both sealers types than at the middle and coronal levels for both sealers.
Under the conditions of the present study, it can be concluded that:
1. TotalFill bioceramic sealer increase the force required to fracture in single-rooted endodontically treated premolar teeth.
2. Lateral condensation technique creates stresses in the root during obturation, which caused a marked reduction of the fracture resistance of endodontically treated teeth.
3. Lateral compaction technique provided more gutta-percha percentage but higher voids than single cone regardless of the sealer used.
4. A trend for increased amount of gutta-percha from apical to coronal direction could be observed.
5. There was no correlation between fracture resistance and percentage of gutta-percha and sealer filled area.
6. Increasing the percentage of voids in root canal obturation could lead to decrease of the fracture resistance of endodontically treated teeth.