الفهرس 
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Abstract
The aim of this study was to evaluate different types of endodontic access cavity designs using two different rotary filing systems clinically in terms of canal transportation, centering ability and postoperative pain and laboratory in terms of canal transportation and centering ability.
Twenty patients had been selected according to the inclusion and exclusion criteria, where each patient had both the right and left mandibular molars treated with root canal treatment. The patients were randomly classified into 2 groups (N=10 patients) as follow: group Ia; where ten patients with ten teeth had traditional endodontic cavities (TECs), and then the canals were instrumented by HyFlex EDM single file. (n=10 teeth), group Ib; where ten patients with ten teeth had contracted endodontic cavities (CECs), and then the canals were instrumented by HyFlex EDM single file. (n=10 teeth), group IIa; where ten patients with ten teeth had traditional endodontic cavities (TECs), and then the canals were instrumented by ProTaper Next files. (n=10 teeth), and group IIb; where ten patients with ten teeth had contracted endodontic cavities (CECs), and then the canals were instrumented by ProTaper Next files. (n=10 teeth). All teeth were scanned using CBCT to detect the canals’ shape before instrumentation.
After the access cavity preparation, the working length was established then glide path preparation was performed using Pathfiles. group I was instrumented using HyFlex EDM single file , while group II was instrumented using X1,X2 ProTaper Next files. Canals were irrigated during instrumentation with 5.25% NaOCl and 17% EDTA, at the end of the instrumentation passive ultrasonic activation with NaOCl was done.
For evaluation of the transportation and the centering , the canals were scanned after the mechanical instrumentation preparation using CBCT, then before and after scans were superimposed and only the mesiobuccal root canal was evaluated.
Results showed that summing of the total amount of transportation instrumented by HyFlex EDM and ProTaper Next files, there was statistically significant difference between TECs and CECs. By comparing between the root levels, there was statistically significant difference between TECs and CECs instrumented by HyFlex EDM single file at the apical, middle and coronal root level, while there was statistically significant difference only at the apical and middle root level between TECs and CECs when instrumented by ProTaper Next files. Summing of all root levels of teeth instrumented by HyFlex EDM single file showed statistically significant difference between TECs and CECs, as well as the summing of all root levels of teeth instrumented by ProTaper Next files showed statistically significant difference between TECs and CECs.
Regarding the total centering ability of HyFlex EDM and ProTaper Next files together, there was no statistically significant difference. By comparing between the root levels, there was statistically significant difference between TECs and CECs instrumented by HyFlex EDM single file, as well as between TECs and CECs instrumented by ProTaper Next files at the apical, middle and coronal root levels. Summing of all root levels of teeth instrumented by HyFlex EDM showed statistically significant difference between TEC and CEC, while summing of all root levels of teeth instrumented by ProTaper Next files showed no statistically significant difference between TECs and CECs.
Postoperative pain was of significant difference between TECs and CECs when evaluated at 24 hours, 48 hours and 72 hours only, where pain was diminished at the 7th day.
Age, sex and tooth location did not show any significant difference between HyFlex EDM and ProTaper Next in relation to postoperative pain.
Laboratory test was done on 40 intact mature human 2 rooted maxillary premolars. group allocation was performed randomly into 4 groups(n=10 teeth) as follow: group 1; where ten teeth had traditional endodontic cavities (TECs), and the canals were instrumented by HyFlex EDM single file, group 2; where ten teeth had contracted endodontic cavities (CECs), and the canals were instrumented by HyFlex EDM single file, group 3; where ten teeth had traditional endodontic cavities (TECs), and the canals were instrumented by ProTaper Next files ,and group 4; where ten teeth had contracted endodontic cavities(CECs),and the canals were instrumented by ProTaper Next files. All teeth were scanned using CBCT to detect canals shape before instrumentation.
After access preparation, the working length was established and instrumentation using either HyFlex EDM or ProTaper Next files according to the groups allocation. For evaluation of the transportation and centering, the root canals were scanned after the mechanical instrumentation using CBCT, then before and after instrumentation scans were superimposed and only the buccal canals were evaluated.
Laboratory transportation results showed statistically significant difference between TECs and CECs at the apical, middle and coronal root levels when instrumented with HyFlex EDM as well as ProTaper Next files. Summing of all root levels of each file system used also showed statistically significant difference between TECs and CECs. Summing of all results obtained from both filing showed statistically significant difference between TECs and CECs.
Regarding the centering ability, no statistically significant difference was shown between TEC and CEC at the apical, middle and coronal root levels when instrumented by HyFlex EDM, as well as the summing of all root levels of TECs instrumented by HyFlex EDM did not showed statistically significant difference than CECs instrumented by HyFlex EDM. No statistically significant difference was shown between TEC and CEC at the middle and coronal root levels when instrumented by ProTaper Next files and there was statistically significant difference apically. Summing of all root levels of TECs instrumented by ProTaper Next files did not showed statistically significant difference than CECs instrumented by ProTaper Next files. Summing of all TECs, instrumented by HyFlex EDM and ProTaper Next files showed no statistically significant difference than their correspondence of the CECs.