Objective:Analysis of shaping ability of four different rotary endodontic instruments using spiral computed tomography (CT).Materials and Methods:Eighty freshly extracted human mandibular first molars were used in the present study. Samples were randomly divided into four experimental groups with twenty samples in each group. Images of mesiobuccal canal of each sample were obtained pre- and post-operatively using spiral CT. All samples were prepared using their respective endodontic file systems (group I - ProTaper, group II - K3, group III - RaCe, and group IV - Mtwo). Image analyses were done using image analysis software for evaluation of canal transportation and centering ability. Data was then statistically analyzed using analysis of variance.Results:There was no statistically significance in transportation in their intergroup difference at any of the three locations (coronal, middle, and apical third). In centering ability there was no statistically significance in the coronal and middle third of the intergroup. However, there was a statistically significance of (P = 0.044) at the apical third between all the groups.Conclusion:Canals prepared with ProTaper had more canal transportation at all the three levels of root canal (coronal, middle, and apical third). Canals prepared with Mtwo were well centered at coronal and middle third whereas with RaCe canals were centered only at the apical third. All instruments showed some degree of canal aberrations in terms of shaping ability.

Aim:The present study aimed to compare the remaining dentin thickness (RDT) and fracture resistance of conventional and conservative access and biomechanical preparation in molars using cone-beam computed tomography (CBCT).Methodology:A total of 60 freshly extracted human molars were selected and were randomly divided into two groups of conventional and conservative access preparation group (n = 30). Samples were subjected to pre-CBCT scan at the pericervical region for the measurement of total dentin thickness. For the conventional group, samples were accessed and biomechanical preparation was done using K3 XF file. For conservative group, samples were accessed using CK microendodontic burs using a dental operating microscope and biomechanical preparation was done using self-adjusting file. After obturation and postobturation with nanohybrid composite restoration, samples of both groups were subjected to post-CBCT scan at pericervical region for the measurement of RDT. The samples were then loaded to fracture in the Instron Universal Testing Machine, and the data were analyzed using paired sample t-test and independent sample t-test.Results:The mean RDT was less in conventional group than conservative group. Pericervical dentin was preserved more in conservative group. The statistical difference among both the experimental group was highly significant (<0.001). The mean load at fracture was less in conventional group than conservative group (<0.001).Conclusion:Coronal dentin was conserved in molars when accessed through conservative than through conventional. The dentin conservation afforded an increased resistance to fracture in conservative group which is doubled the fracture resistance in conventional group.

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