This work reports on a study that was designed to investigate teaching interventions, starting from high school students' misconceptions about vision and light propagation concepts. A standard test was applied to detect these misconceptions and its results obtained were discriminated in categories as a threshold for the organization of teaching. These categories were formulated analogously to the models created in the History (eye, light bath, intermediate and scientific ones). The intervention was elaborated assuming the strategy of conflict or instability of cognitive nature, carried out through debates of open problematic situations. The results acquired after post-testing evaluation reveal that this methodology is quite advantageous owing the confirmation of successful retention learning, through the annihilation of misconceptions and the belief in the scientific model.
Recently most analyses of Ca and P in different parts of tooth enamel have been performed semi-quantitatively. A direct and semi quantitative method for the determination of major and trace elements in human teeth by X-ray spectrometry is reported. The ratio Ca/P has been determined in the surface enamel of the third molar teeth. The surfaces were irradiated with short pulse laser Nd:YAG. The modifications in human dental enamel chemical composition for major and trace elements is here outlined. The accuracy of procedures was performed by analysis of natural hydroxyapatite as standard reference material. Results are consistent with other studies and they have indicated greater ratio Ca/P in irradiated groups in comparison to the non-irradiated group.