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This in vitro study aimed to assess and compare premolars cuspal deflection that restored with different bulk fill resin materials types (SonicFillTM2, Beautifil Bulk Fill restorative, and FiltekTM Bulk Fill posterior restorative) to those incrementally restored group with conventional composite restorations (low shrinkage universal Tetric Evoceram). A total of 40 intact human maxillary first premolars were prepared into large MOD. Then teeth were randomly classified into four groups (n=10 for each group) according to restorative materials as following: Group A: Teeth were restored with Sonic FillTM2 composite, Group B: restored with Beautifil Bulk Fill restorative material, Group C: Teeth were restored with Filtek BulkTM Fill posterior restorative, and Group D: Teeth were restored with Universal Tetric Evo Ceram®. Digital microscope was used to measure intercuspal distance between two index reference points on the tips of the cusps before preparation, after preparation, and 15minutes after completion of restorations. The differences registered as cuspal deflection. All teeth were exposed to inward cuspal deflection after restoration and all groups that restored with bulk fill restoration reported lower cuspal deflection in compared to group D that restored with conventional composite in layering technique. Beautifil Bulk Fill restorative produced significantly greater cuspal deflection than other bulk fill groups. The study concluded that the use of new bulk fill restorative materials might reduce amount of cuspal deflection significantly. However, type of bulk fill restorative materials also influenced on amount of cuspal deflection so restoration with Sonic Fill™2 composite and Filtek Bulk™ Fill posterior reported lower cuspal deflection than Beautifil Bulk Fill restorative material.

Background: The purpose of this study was to evaluate and compare centering ability and canal transportation of simulated S-shaped canals instrumented with four different types of rotary nickel-titanium systems. Materials and Methods: Forty simulated S-shaped canals in resin blocks were divided into four groups of ten each and were instrumented to an apical size 25 by different instrumentation technique using ProTaper Universal files (group A), ProTaperNext (group B), Reciproc (group C) and WaveOne (group D).Centering ability and canal transportation was measured at (11) measuring points from D0 to D10 bysuperimposion of the pre-and postoperative images obtained by using digital camera in standardized manner. An assessment of the canals shape was determined using Photoshop CS2 and AutoCAD software. The data were analyzed statistically using ANOVA and LSD test. Results: In terms of centering ratio values, there was no statistically significant difference among the four groups at the coronal portion of the canals, with ProTaper system showing the least centering ability at all levels except at apical foramen. At the apical curvature, the Reciproc and WaveOne groups showed better centering ability than ProTaperNext and the difference was statistically highly significant among them at these points, while at the coronal curvature the ProTaperNext showed better centering ability than Reciproc and WaveOne. Canal transportation was seen in all groups but the ProTaper systems showed more transportation values at almost levels when compared with the other groups with the least values by ProTaperNext at the coronal curvature and the least values by Reciproc and WaveOne at the apical curvature. Conclusions: Under the conditions of this study, ProtaperNext ,WaveOne and Reciproc instruments maintained the original curvature significantly better than ProTaperUniversal at almost levels. ProtaperNext showed a better shaping ability than Reciproc and WaveOne at the coronal curved section while at apical curved section Reciproc and WaveOne showed a better shaping ability than ProtaperNext.

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