Climate and colonialism

Recent years have seen a growth in scholarship on the intertwined histories of climate, science and European imperialism. Scholarship has focused both on how the material realities of climate shaped colonial enterprises, and on how ideas about climate informed imperial ideologies. Historians have shown how European expansion was justified by its protagonists with theories of racial superiority, which were often closely tied to ideas of climatic determinism. Meanwhile, the colonial spaces established by European powers offered novel ‘laboratories’ where ideas about acclimatisation and climatic improvement could be tested on the ground. While historical scholarship has focused on how powerful ideas of climate informed imperial projects, emerging scholarship in environmental history, history of science and historical geography focuses instead on the material and cognitive practices by which the climates of colonial spaces were made known and dealt with in fields such as forestry, agriculture and human health. These heretofore rather disparate areas of historical research carry great contemporary relevance of studies of how climates and their changes have been understood, debated and adapted to in the past

Retention force assessment in conical crowns in different material combinations

The puprose of this study was to evaluate retention force of conical double crowns in two material connections: gold casting alloy/gold casting alloy and gold casting alloy/gold electroforming alloy. 12 crown pairs of both material connections with the cone angles of 2°, 4° and 6° were made. Experiment of 10.000 in-and-out cycles was performed using a new device which allows the retentive force to be measured in continuous way without necessity of moving the samples to another device. It has been found that the higher the retentive force values, the lower the cone angle. Dispersion of the retention value was similar in both groups, but when cone angle was 2° or 4°, stability of retention force with the passage of time was higher in combinations with electroformed copings. The optimum solution was the cast alloy/cast alloy connection but only with cone angle 6°. However, retentive values seem to be too low to achieve proper retention of dentures

Denticles. A literature review

Denticles are pulp degenerations in the form of calcified deposits of mineral salts, usually found in molars and lower incisors, as well as in impacted teeth and deciduous molars. Denticles may come in various sizes, from microscopic particles to larger mass that almost obliterate the pulp chamber and are visible only on X-ray images. Denticles form as a result of chronic inflammatory lesions, but may also be caused by injuries and conservative treatment. They are most frequently found in necrotic foci. Denticles may cause problems for root canal treatment, as their presence might make it difficult to obtain proper access to the pulp chamber bottom and the canal orifices. There is also the increased risk of bending or breaking the endodontic instruments. Sometimes, denticles fill the entire space of the tooth chamber and pushing the pulp to the edges of the chamber. Denticles can cause pain due to the pressure on the nerves and blood vessels supplying the internal tissue of the tooth. The presence of large denticles might eventually lead to necrosis of the pulp. Denticles accompany certain diseases, such as dentin dysplasia, odontodysplasia or Albright hereditary dystrophy