Electron microscopy of satellite tobacco mosaic virus crystals: metal-coated, negatively stained and stereo pairs

Highly purified virions of satellite tobacco mosaic virus (STMV) were found to crystallize at relatively low concentrations (300-500 microg ml(-1)) in pure water. Small crystals of these preparations were examined in the transmission electron microscope after either being rotary shadowcast with metal or negatively stained with 4% uranyl acetate. Stereo views were also obtained of both types of preparations. Stereo pairs of metal-coated crystals provided good three-dimensional images. When stereo pairs of negatively stained crystals were printed from second negatives, they provided striking images although the three-dimensional aspect was not so pronounced. Images of both types of preparations were compared with a computer-generated model of the virus. This model was based on data obtained in earlier X-ray diffraction crystallographic studies. Measurements of crystal axes on the EM images were somewhat lower than those of the computer model. It is assumed the reason for this is the dehydration of crystals during preparation for electron microscopy. The EM images did verify the type of crystal lattice determined in the X-ray diffraction studies. Conversely, knowing the exact unit cell parameters and the distribution of virions in the crystal from X-ray diffraction data aids in the further interpretation of electron micrographs of virus crystals

Sympathomimetic effects of chronic methamphetamine abuse on oral health: a cross-sectional study

Background: Methamphetamine, a highly addictive sympathomimetic stimulant, is currently widely abused worldwide and has been associated with devastating effects on oral health, resulting in the term "meth mouth". However, "meth mouth" pathology is primarily based on case reports with a lack of systematic clinical evaluation. Therefore, we have conducted a systematic study to investigate (1) the pharmacological impact of methamphetamine on oral health with regard to saliva function, including the parameters saliva flow rate and total saliva production (ml/5 min) and the buffering capacity of saliva;(2) the contribution of the symptoms of bruxism and muscle trismus to potential oral health damage. Methods: We assessed the data of 100 chronic methamphetamine abusers and 100 matched-pair comparison participants. Primarily, we conducted an anamnesis with all methamphetamine abusers with regard to saliva dysfunctions, jaw clenching and pain in the temporomandibular joint. Subsequently, in the first part of the clinical enquiry, we tested the saliva flow rate and the total saliva production (ml/5 min) by using the sialometry method and the buffer capacity of saliva by determining the pH-value. In the second part of the clinical enquiry, we evaluated bruxism symptoms with respect to generalized tooth attrition, dentine exposure and visible enamel cracks and examined a potential muscle trismus by measuring the maximal opening of the mouth. Results: The majority of methamphetamine abusers reported a dry mouth (72 %) and jaw clenching (68 %). Almost half of all methamphetamine abusers experienced pain in the temporomandibular joint (47 %). With regard to the clinical findings, methamphetamine abusers showed significantly lower total saliva production (ml/5 min) (p 0.05). Conclusions: The sympathomimetic effects of chronic methamphetamine abuse may lead to dry mouth and extensive bruxism and therefore can increase the risk for caries decay, periodontal lesions and tooth wear. Furthermore, a significant decline of saliva buffer capacity in methamphetamine abusers may trigger the risk for dental erosions. Methamphetamine abusers and practitioners should be aware of these symptoms

Short-Term Analysis of Human Dental Pulps After Direct Capping with Portland Cement

This study evaluated the short-term response of human pulp tissue when directly capped with Portland cement. In this series of cases, twenty human third molars that were scheduled for extraction were used. After cavity preparation, pulp exposure was achieved and Portland cement pulp capping was performed. Teeth were extracted after 1, 7, 14 and 21 days following treatment and prepared for histological examination and bacterial detection. Each group had 5 teeth. The results were descriptively analysed. Dentin bridge formation was seen in two teeth with some distance from the material interface (14 and 21 days). Soft inflammatory responses were observed in most of the cases. Bacteria were not disclosed in any specimen. PC exhibited some features of biocompatibility and capability of inducing mineral pulp response in short-term evaluation. The results suggested that PC has a potential to be used as a less expensive pulp capping material in comparison to other pulp capping materials

Influence of test parameters on in vitro fracture resistance of post-endodontic restorations: a structured review

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75093/1/j.1365-2842.2009.01940.x.pd

Management of Crown-related Fractures in Children: An Update Review

Traumatic dental injuries (TDIs) are a serious public health problem. Epidemiology of dental trauma indicates that these injuries are more prevalent in child population of the world. Children are the sufferers in two-thirds of all TDIs observed. Although being a major fraction, crown-related fractures are a less severe form of TDIs with respect to their complications and sequelae. However, as with other types of traumatic injuries, the delay in seeking for immediate care following a traumatic injury and the lack of appropriate treatment may compromise long-term outcomes. This article reviews the occurrence, management, and prognosis of crown-related fractures in primary and permanent teeth in light of the recent literature

Treatment of early caries lesions using biomimetic self-assembling peptides – a clinical safety trial

Objective We previously reported that a rationally designed biomimetic self-assembling peptide, P11-4, nucleated hydroxyapatite de novo and was apparently capable of in situ enamel regeneration following infiltration into caries-like lesions. Our present aim was to determine the safety and potential clinical efficacy of a single application of P11-4 on early enamel lesions.Materials and methods Fifteen healthy adults with Class V 'white spot' lesions received a single application of P11-4. Adverse events and lesion appearances were recorded over 180 days.Results Patients treated with P11-4 experienced a total of 11 adverse events during the study, of which two were possibly related to the protocol. Efficacy evaluation suggested that treatment with P11-4 significantly decreased lesion size (p = 0.02) after 30 days and shifted the apparent progression of the lesions from 'arrested/progressing' to 'remineralising' (p <0.001). A highly significant improvement in the global impression of change was recorded at day 30 compared with baseline (p <0.001).Conclusions The results suggest that treatment of early caries lesions with P11-4 is safe, and that a single application is associated with significant enamel regeneration, presumably by promoting mineral deposition within the subsurface tissue