Effect of Resin Infiltration on Bleached Enamel: An In Vitro Evaluation of Micromorphology, Resin Penetration and Microhardness

Background: Tooth bleaching is a promising aesthetic treatment for shaded teeth; however, demineralized lesions also occur after bleaching, and Icon resin can infiltrate into the demineralized lesions and then improve the color of teeth. This study aims to evaluate the effectiveness of resin infiltration on bleached teeth that are managed with different protocols by assessing the micromorphology of enamel surfaces, the depth of resin penetration and the microhardness of enamel after bleaching and Icon resin infiltration.Methods: A total of 150 noncarious premolars with sound coronal structure, which were extracted for orthodontic purposes, were obtained in this study in three parts: part Ⅰ“micromorphology of enamel surfaces”（n=60）；part II“observation the depth of the resin penetration”（n=30)；part III “Vickers hardness number values”（n=60). Both part Ⅰ and part III were divided into six subgroups. Part II was divided into three subgroups. 10 samples per subgroup. Data were analyzed using SPSS 22.0, Mann-Whitney test.Results: The surface roughness of the teeth increased after bleaching. When etched with 15 % HCl before the resin infiltration, it would result in further increase in roughness, but the surface of the bleached teeth could be as smooth as that of normal teeth after resin infiltration. There was a statistically significant increase in the mean resin penetration depth of the bleached teeth with 5-day delay of resin infiltration over the bleached teeth with resin infiltration immediately (Mann-Whitney test, P<0.05). Otherwise，the VHN values of delayed ones were similar to the normal one.Conclusions: It suggested that Icon resin infiltration treatment should be delayed after tooth bleaching but not performed right after tooth bleaching.

Graphical Evidence for the Solar Coronal Structure during the Maunder Minimum: Comparative Study of the Total Eclipse Drawings in 1706 and 1715

We discuss the significant implications of three eye-witness drawings of the total solar eclipse on 1706 May 12 in comparison with two on 1715 May 3, for our understanding of space climate change. These events took place just after what has been termed the “deep Maunder Minimum” but fall within the “extended Maunder Minimum” being in an interval when the sunspot numbers start to recover. Maria Clara Eimmert’s image in 1706 is particularly important because she was both a highly accomplished astronomical observer and an excellent artist: it was thought lost and was only re-discovered in 2012. Being the earliest coronal drawings of observational value yet identified, these drawings corroborate verbal accounts a corona without significant streamers, seen at totality of this and another eclipse event in 1652 during the Maunder Minimum. The graphical evidence implies that the coronal solar magnetic field was not lost but significantly weakened and the lack of coronal structure means there was little discernable open flux (either polar or at lower latitudes) even during the recovery phase of the Maunder Minimum. These observations provide evidence for a different state of oscillation of the solar dynamo and hence behaviour of the Sun in comparison with that during normal solar cycle minima (when a streamer belt between two polar coronal holes is visible) or near normal sunspot maxima (when coronal structure is caused by coronal holes at all latitudes) even to observers without a telescope.

A phylogenetic study of floral morphology of some members of Asclepiadaceae R.Br

Floral morphological diversity and phylogenetic relationship were studied in the family Asclepiadaceae. This family characterized by unique features that contributes to extreme floral complexity and diversity. In this paper, we used preliminary phylogenetic hypothesis for the family Asclepiadaceae to explore the mode of diversification in pollinarium and coronal structure. The occurance, size, shape, position, orientation of pollinia, mode of pollination and the presence of form of coralline corona and gynostegial corona were studied for similarity indices between two subfamilies Periplocoideae and Asclepiadoideae.