A BSTRACT Objective: The objective of this study was to assess in vitro the structural changes in translucency and opacity of tooth enamel following a direct demineralization process. Materials and Methods: This experimental in vitro study evaluated 45 thirds (cervical, middle, and occlusal) of the tooth enamel surface of premolar teeth extracted from young adults divided into three groups of 15 specimens each: Group 1 (solution based on calcium, phosphorus, and fluorine), Group 2 (orthophosphoric acid 37%), and control group (distilled water). All underwent optical macroscopic examination with ×3 magnification to determine the initial translucency according to the variation of the medium in their intercrystalline spaces, and Thylstrup and Fejerskov Index was used. The experimental groups were then subjected to an artificial caries process during which the specimens were placed in an inorganic and organic solution of calcium, phosphorus, and fluorine at 37°C for 90 days with the acidic solution at pH 5 and the neutral solution at pH 7. The control specimens were placed in distilled water. Finally, all the specimens were assessed by polarization microscopy. Results: In relation to the occlusal third, the highest proportion in Groups 1 and 2 was in Grades 2 and 3 (80%). A significant association was only observed between the experimental groups in the degree of translucency in the occlusal third ( P = 0.002), whereas no association was found in relation to the degree of opacity in the middle and cervical thirds in either study group ( P > 0.05). Conclusion: The resistance of enamel hydroxyapatite crystals increases from occlusal to cervical due to the greater presence of aprismatic enamel in the cervical horizontal third.

RESUMENEl presente artículo es una síntesis de las investigaciones teóricas y metodológicas de las formas histórico generales de la personalidad en el Perú, esto es desarrollado desde los campos de la psicohistoria y neurociencias. Se plantea y desarrolla la categoría de formas histórico generales de la personalidad. Se explica su devenir en la evolución de los hombres del Perú, desde la época prehispánica hasta el período republicano, incluyendo la Colonia. Los datos históricos y sociales de cada época se integran dentro de una interpretación psicológica de los patrones más generales de personalidad. Seguimos un método de análisis cualitativo a partir de datos históricos. Desde una reelaboración psicohistórica, interrelacionamos e integramos construcciones transdisciplinarias, neurocientíficas, psicológicas, históricas y etnohistóricas. En las conclusiones, resaltamos el valor heurístico de la categoría formas histórico generales de la personalidad, para el desarrollo de la psicohistoria, de la psicología, y de las neurociencias de base científico social.Palabras clave: Formas histórico generales de la personalidad, Esencia humana, personalidad, Psicohistoria, Neurociencia, Etnohistoria, Dualidad histórica. ABSTRACTThe present paper is a synthesis of the theoretical and methodological investigations about the general historical forms of personality in Peru, which is developed from the fields of psychohistory and neurosciences. We propose and develop the category of general historical forms of personality. We explain their development in the evolution of people from Peru, from the prehispanic time, until the republican period, including the colony. The historical and social data of each time are integrated inside a psychological interpretation of the most general patterns of personality. We follow a method of qualitative analysis starting from historical data. From a psychohistoric restructuring, we interrelate and integrate transdisciplinary, neuroscientific, psychological, historical and ethnohistorical constructions. In the conclusions, we stand out the heuristic value of the category general historical forms of personality, for the development of psychohistory, psychology, and social scientist based neurosciences.