RESUMO
Algorithms that automatically explore the chemical space have been limited to chemical systems with a low number of atoms due to expensive involved quantum calculations and the large amount of possible reaction pathways. The method described here presents a novel solution to the problem of chemical exploration by generating reaction networks with heuristics based on chemical theory. First, a second version of the reaction network is determined through molecular graph transformations acting upon functional groups of the reacting. Only transformations that break two chemical bonds and form two new ones are considered, leading to a significant performance enhancement compared to previously presented algorithm. Second, energy barriers for this reaction network are estimated through quantum chemical calculations by a growing string method, which can also identify non-octet species missed during the previous step and further define the reaction network. The proposed algorithm has been successfully applied to five different chemical reactions, in all cases identifying the most important reaction pathways.
RESUMO
Se han reportado en los últimos años que los análisis de Moyers y de Tanaka-Johnston no son muy efectivos para predecir la suma de los anchos mesiodistales de caninos y premolares no erupcionados cuando son realizados en poblaciones caucásicas. Este estudio toma una muestra de 400 escolares de Lima Metropolitana para probar una nueva ecuación de dentición mixta basada en una población peruana. Se crean cuatro ecuaciones de predicción tanto para varones como para mujeres y se establece las diferencias que se obtienen entre los valores predecidos por el análisis de Moyers y con los valores predecidos por el análisis de Tanaka-Johnston. Al comparar las diferencias entre los tres análisis, se obtiene que las Nuevas Ecuaciones creadas en este estudio demostraron tener mayor eficacia para la predicción de la suma de los caninos y premolares permanentes en cada cuadrante para determinar el espacio requerido en el análisis de predicción en dentición mixta. Por lo tanto las ecuaciones producto de esta investigación podrían usarse en poblaciones de características similares a este estudio.
It has been reported in recent years that analysis of Moyers and Tanaka-Johnston are not very effective to predict the sum of the mesiodistal widths of unerupted canines and premolars when performed in populations of different ethnic groups for which they were created. Both tests conventionally used for mixed dentition orthodontic diagnosis were performed in Caucasian populations. This study took a sample of 400 schoolchildren in metropolitan Lima to create a mixed dentition analysis based on a Peruvian population. It creates four prediction equations for both men and women and establishes the differences obtained between the values predicted by the new equations with those with the canines and premolars per quadrant. It also establishes the difference in millimeters between the actual values with the values predicted by the analysis of Moyers and the values predicted by the Tanaka-Johnston analysis. By comparing the differences between the three tests, we found that the new equations developed in this study demonstrated to be more effective in predicting the sum of permanent canines and premolars in each quadrant to determine the space required on the mixed dentition prediction analysis. Equations therefore product of this research could be used in the peruvian population.