The influence of nicotine on the bone loss rate in ligature-induced periodontitis. A histometric study in rats

Background: The present study investigated the possible influence of nicotine on the bone loss rate in the furcation region due to ligature-induced periodontitis in rats. Methods: Twenty adult male Wistar rats were included. After anesthesia, the tooth was randomly assigned to receive the cotton ligature in the sulcular area, while the contralateral tooth was left unligated. The animals were randomly assigned to one of the following treatments, including daily intraperitoneal injections: group A, 2 mul/g body weight of saline solution; group B, 2 mul/g body weight of a nicotine solution with 0.13 mul of nicotine/ml of saline solution; group C, 2 mul/g body weight of a nicotine solution with 0.19 mul of nicotine/ml of saline solution; and group D, 2 mul/g body weight of a nicotine solution with 0.26 mul of nicotine/ml of saline solution. Thirty days later, the animals were sacrificed and the specimens routinely processed for serial decalcified sections. Results: Intergroup analysis revealed greater bone loss in the ligated teeth of group B (1.01 +/- 0.61 mm(2)), group C (1.14 +/- 0.72 mm(2)), and group D (1.36 +/- 0.60 mm(2)) when compared with group A (0.64 +/- 0.62 mm(2)) (P <0.01). However, no statistically significant differences in bone loss were found among groups B, C, and D. In addition, no bone loss was observed for unligated teeth (P >0.01). Conclusions: Within the limits of the present study, nicotine enhanced the effects of the local components of periodontal disease in a non-dose-dependent way; nevertheless, the administration of nicotine did not produce periodontal bone loss by itself.7191460146

Exploiting chemically selective weakness in solids as a route to new porous materials

Weakness in a material, especially when challenged by chemical, mechanical or physical stimuli, is often viewed as something extremely negative. There are countless examples in which interesting-looking materials have been dismissed as being too unstable for an application. But instability with respect to a stimulus is not always a negative point. In this Perspective we highlight situations where weakness in a material can be used as a synthetic tool to prepare materials that, at present, are difficult or even impossible to prepare using traditional synthetic approaches. To emphasize the concept, we will draw upon examples in the field of nanoporous materials, concentrating on metal-organic frameworks and zeolites, but the general concepts are likely to be applicable across a wide range of materials chemistry. In zeolite chemistry, there is a particular problem with accessing hypothetical structures that this approach may solve