Mechanics of particles system in the Theory of Relativity

Studying the mechanics of particle systems in special relativity is one of the most complex issues. However, this study sets us up to lay the groundwork for building a set of important laws. The motion of particle masses as a whole was determined by their energy, impulse and static mass. It was also found that the total energy of the system of mutual action requires taking into account the energies of these mutual acts between the particles. Contrary to the systems of the mutual acts of collisions, approximate formulas for interplay between charged particles were determined by studying the collision of relativistic particles-Compton's effect. Finally, the case of the movement of the charged particles of weak interacts was discussed, and the movement of the interconnected particles was discussed through mutual electromagnetic acts using the concept of mutual action between the particles of the system.

An In-Vitro Comparative Study of Apically Extruded Debris and Irrigants Using different Preparation Techniques

Aim: The aim of this study was to compare the weight of debris and irrigant that extruded apically during the preparation of root canal system using standardized technique, hand ProTaper, and rotary universal ProTaper. Materials and Methods: The sample was consisted of 30 single rooted teeth, with single canal and apical foramen, the working length was standardized and the access cavity prepared, each tooth was fixed with ruper stopper in glass vial contains agar 1.5% to simulate the periapical tissue. And the vial was fixed in a bigger vial to eliminate any unneccesry contact with the apparatus. The first vial was weighted before and after preparation. The sample was randomly divided into three groups, group A Standardized technique, B Hand ProTaper PTH , C Universal ProTaper PTU. Result: The three techniques caused apically extruded debris and irrigants, with statically significance between Standarized technique and Hand ProTaper(P= 0.024) while the first caused more debris and irrigants extrusion, also Universal ProTaper caused more extrusion than Hand ProTaper with statically significance (p= 0.050), but there was no significant differences between Standarized technique and Universal ProTaper P>0.05. Conclusion: Under the condition of this study, it can be concluded that both hand and rotary preparation technique will cause apical extrusion of debris and irrigants. And PTH was the least causing of apically extrusion.