BACKGROUND AND OBJECTIVE: Mechanical preparation of root canal system is an important objective of root canal therapy. Many rotary devices have been produced to decrease instrumentation time and improve its quality. The purpose of this study was to compare apical transportation in root canal treatment with three methods of hand, RECIPROCAL and rotary (Race) instrumentation.METHODS: In this experimental study 45 extracted human mandibular first molar were selected. The crown was cut at CEJ. The roots were mounted in acrylic resin material. The roots had a 20-40 degree canal curvature. Teeth were randomly divided into 3 groups. Group one was prepared with hand method and NiTi files, group two was prepared with Endogripper handpiece and NiTi files, group three was prepared with Race rotary system. By superimposing the initial file and MAF radiography the apical transportation was evaluated (double exposure radiography method(.FINDINGS: Race rotary system (group 3) had prepared canals without transportation and deviation in the original shape of canals. NiTi hand files (group 1) had prepared canals with 8 apical transportations out of 15 root canals. RECIPROCAL handpiece with NiTi files had prepared canals with 7 apical transportations. Race rotary system was prepared canals with significant the least apical transportations than other groups (p<0.05).CONCLUSION: The results showed that original canal shape in apical region had minimum transportation with race rotary system compare with hand or RECIPROCAL preparation.

Statement of Problem: Total removal of tissues and remnant microorganisms as well as canal shaping is the essential objectives of endodontic therapy. A successful endodontic treatment is obtained through Shilders principals, however; complete observation of this technique using stainless steel files manually is problematic and time-consuming. Modern technology, in order to eliminate such problems, has presented new facilities such as Nickel-Titanium (NiTi) files and engine driven instruments.Purpose: The aim of this in-vitro study was to compare the canal debridement efficiency of three engine driven instruments: Rotary, RECIPROCAL and Vertical.Materials and Methods: In this experimental study, 60 mesial roots of human first and second mandibular molars were divided into three groups randomly. In each sample, one canal was considered as case, the other one as control. Files used in RECIPROCAL and vertical groups were of handy Ni-Ti type and in rotary group, rotary Ni-Ti files were used. After debridement, the roots were sectioned at 3mm and 5mm from anatomic apex, stained and examined under light microscope. Comparison criteria between case and control groups were based on residual debris and predentin and the level of root canal preparation and shaping after debridement. Data were subjected to kruskal-Wallis non-parametric test.Results: There was no significant difference between the efficiency of debridement at 3mm and 5mm sections between all groups. But difference in time consumption was significant ranked from the shortest to the longest as rotary, RECIPROCAL and vertical.Conclusion: The efficiency of debridement between the three automated instruments was approximately equal, however; the instrumentation time was different between three groups. Rotary system was the fastest one, as compared with RECIPROCAL (second) and vertical (last). It may be concluded that rotary system has a superiority over the other two groups in conventional root canal therapies.

The energy of a graph $G$, denoted by $\mathcal{E}(G)$, is defined as the sum of absolute values of all eigenvalues of $G$. A graph $G$ is called RECIPROCAL if $ \frac{1}{\lambda} $ is an eigenvalue of $G$ whenever $\lambda$ is an eigenvalue of $G$. Further, if $ \lambda $ and $\frac{1}{\lambda}$ have the same multiplicities, for each eigenvalue $\lambda$, then it is called strong RECIPROCAL. In (MATCH Commun. Math. Comput. Chem. 83 (2020) 631--633), it was conjectured that for every graph $G$ with maximum degree $\Delta(G)$ and minimum degree $\delta(G)$ whose adjacency matrix is non-singular, $\mathcal{E}(G) \geq \Delta(G) + \delta(G)$ and the equality holds if and only if $G$ is a complete graph. Here, we prove the validity of this conjecture for some strong RECIPROCAL graphs. Moreover, we show that if $G$ is a strong RECIPROCAL graph, then $\mathcal{E}(G) \geq \Delta(G) + \delta(G) - \frac{1}{2}$. Recently, it has been proved that if $G$ is a RECIPROCAL graph of order $n$ and its spectral radius, $\rho$, is at least $4\lambda_{min}$, where $ \lambda_{min}$ is the smallest absolute value of eigenvalues of $G$, then $\mathcal{E}(G) \geq n+\frac{1}{2}$. In this paper, we extend this result to almost all strong RECIPROCAL graphs without the mentioned assumption.

Climate change is one of the most pressing problems among scientists worldwide, with experts warning about it and even referring to it as unfathomable human agony. In this study, we reviewed previous studies and examined two gaps in the existing approach to climate change studies. First, look at the "side EFFECTs" of global warming that have been overlooked in the process and then look at the leading "cause" of global warming, namely "humans" and not its "EFFECTs". The findings revealed that a 1. 4 °C temperature increase (as predicted by United National (UN) projections) would not only raise this amount but also trigger further global warming. As a result, the premise that global warming produces additional global warming was proven. In the Water Area (WA) class, radiant energy increased by 1194. 8%, compared to 1205. 8%, 1154. 9%, 1115. 6% and 1229% in the Vegetation Area Class (VAC), Agricultural Area Class (AAC), Bare Area Class (BAC) and Salt Lake Class (SLC), respectively. Although the Land Surface Temperature (LST) of all classes has only increased by about 0. 4 °C, these changes in radiant energy are much more pronounced. The current study also revealed that most legitimate research on this subject has focused on the EFFECTs of global warming on environmental variations. These studies, which see these changes as "results" of climate change and global warming, have overlooked the primary cause, "human demands", which has prompted humans to alter or exploit their surroundings actively. This study found that concentrating on humans and encouraging them to focus on happiness rather than pleasure is more helpful in addressing global warming issues than focusing on its impacts, such as rising sea level, storms, drought, etc. The results of this study are helpful for a deeper understanding of global warming and a careful study of the cause and dimensions of this phenomenon.

Recently, Hua et al. defined a new topological index based on degrees and inverse of distances between all pairs of vertices. They named this new graph invariant as RECIPROCAL degree distance as RDD(G) =å{u,n}ÍV(G)(d(u) + d(n))[d(u,n)]-1, where the d(u,n) denotes the distance between vertices u and n. In this paper, we compute this topological index for Grassmann graphs.