Ameloblastomatous changes in dentigerous cyst

A bstract — A rare case of an ameloblastomatous lesion occurring within a dentigerous cyst is reported. Differing opinions regarding this lesion are presented, and the significance, with regard to management, is discussed.     

Effect of bite force on the masseteric electromyographic silent period in man

The duration of the masseteric EMG silent period as induced by tapping on the chin was measured at different levels of sustained bite force. Under both open bite and normal occlusion, the duration of the silent period was inversely related to the magnitude of the bite force. For bite force of the same magnitude, the value of the silent period remained relatively constant for the same subject in different trials (SEM ? 1 per cent), whereas the absolute values of the silent periods ranged far and wide for different individuals even under similar experimental conditions.     

A new approach in construction of nasal septal obturators

Nasal septal obturators are used to mechanically close nasal septal defects. The use of an impression of the nasal septal defect in the construction of nasal septal obturators is mandatory. A heat-cured, highly polished acrylic resin button constructed from an accurate impression is less likely to induce crusting and bleeding, or to be dislodged, than a Silastic button.     

Reflectance spectra of composite resins on liners

The reflectance spectra of two types of composite resins were determined on various backgrounds. It was found that the shade differences caused by different "whitish" liners were perceptible only for thin resin specimens and were smaller than those caused by varying the resin type and thickness. Employing a light brown liner gave rise to a difference in shade which was also perceptible on resin specimens of 2.5 mm thickness. Shade differences due to varying the thickness of the specimens were more pronounced on white than on black backgrounds. The clinical significance and the qualitative physical interpretation of the results were discussed.     

The basic proline-rich proteins in human parotid saliva from a single subject.

Eleven Chromatographic fractions of basic proline-rich proteins isolated from parotid saliva from a single donor showed similar but not identical chemical compositions; proline, glycine and glutamic acid-glutamine accounted for 70–80 per cent of the total residues in the proteins. The basic amino acids, lysine and arginine, accounted for a further 10 per cent. All the proteins were in freshly-collected saliva and did not result from post-secretory proteolysis. The most basic of the proline-rich proteins, I-B9, was purified and characterized. The amino terminal residue was serine and the carboxyl terminal residue arginine. The molecular weight determined by quantitative end-group analyses was 9000–9500. Protein I-B9 was resistant to hydrolysis by collagenase and Staphylococcus aureus protease, whereas papain and subtilisin extensively degraded it. I-B9 fragments from clostripain and elastase digestions were isolated for use in sequence determination. Basic proline-rich proteins, acidic proline-rich proteins and proline-rich glycoprotein accounted for 23, 30 and 17 per cent, respectively of the total protein in the parotid saliva.     

Cultivable microbial flora associated with persistent periapical disease and coronal leakage after root canal treatment: a preliminary study

AIM: To identify the cultivable bacterial flora in root filled teeth with persistent periapical lesions and to locate their distribution within the root canal system using an in vitro sampling protocol. METHODOLOGY: Eight freshly extracted root filled teeth were collected from the Oral and Maxillo-facial Surgery Department, Eastman Dental Hospital. Seven teeth were associated with persistent apical periodontitis and also showed evidence of coronal leakage. Teeth were transferred to an anaerobic chamber immediately after careful extraction and sectioned transversely to give a crown (in all but one case) and two root segments (coronal and apical). Two samples were obtained from each segment, one from dentine and the other from the restoration or gutta-percha (GP) root filling (46 sites in total). The samples were dispersed, serially diluted and cultured on blood agar and fastidious anaerobic agar (with 5% defibrinated horse blood). The primary growth was subcultured to obtain pure isolates, which were identified by routine microbiological techniques and commercial enzyme tests. RESULTS: A total of 252 strains were isolated from all the teeth. Of all the isolates, the most prevalent bacteria were Gram-positive facultative anaerobes 189/252 (75%) with staphylococci (48/252, 19%), streptococci (44/252, 17%), enterococci (20/252, 8%) and Actinomyces species (20/252, 8%) being found in most of the teeth (6/8, 6/8, 5/8, 5/8 and 7/8, respectively). Of the obligate anaerobes (17%), peptostreptococci (7%) were also present in most teeth (7/8). A statistical association between bacterial flora and site (crown/coronal/apical) or surface (dental/GP/restoration) could not be shown. CONCLUSIONS: The predominant group of bacteria in root filled teeth with persistent apical periodontitis and coronal leakage was Gram-positive facultative anaerobes of which staphylococci followed by streptococci and enterococci were the most prevalent.     

"Moebius syndrome": a case report

Moebius syndrome is an extremely rare disorder characterized by a lifetime facial paralysis, involving sixth and seventh cranial nerves with malformations of orofacial structures and the limbs. In this case, an 8 year old girl with Moebius syndrome is presented, clinical findings are described and management aspects are discussed. Early dental evaluation and parental counselling as a part of preventive dental regimen can go a long way in providing complete psychosocial rehabilitation for such physically disabled children.     

Dealloying and electroformation in high-Pd dental alloys.

OBJECTIVE: The corrosion of high-Pd dental alloys, depending on their composition, is postulated to be associated with dealloying and electroformation. The aim of this study was to obtain additional information to support these postulations. METHODS: The corrosion characteristics of two commercial high-Pd alloys, Naturelle (79Pd-10Cu-2Au-9Ga wt%) and Rx 91 (54Pd-37Ag-9Sn), and their elemental components were evaluated in a phosphated buffer saline (PBS) solution. Indium, a common element in high-Pd alloys, was also included. The corrosion characteristics measured for each material were the 24 h open circuit potential (OCP) and the potentiodynamic anodic polarization curve. Additionally, the surface composition of the two alloys, before and after immersion corrosion in PBS for 2 months, was analyzed by X-ray photo electron spectroscopy (XPS). RESULTS: Of the pure metals, Ga had the most electroactive OCP followed in order by In, Sn, Cu, Ag, Au, and Pd. The anodic polarization data showed all base metals to be unstable in PBS. The electroformation of AgCl was evidenced in the polarization curve of pure Ag. Both electrochemical characteristics of the PdCu-based alloy were very similar to that of pure Pd. The PdAg-based alloy displayed corrosion behavior resembling that of Ag. XPS data showed that the corrosion of the PdCu-based alloy was associated with a decrease in surface content of Cu and Ga but an increase in Pd and Au. The PdAg-based alloy surface during corrosion showed a decrease in Sn, an increase in Ag, and an unaltered Pd content. The behavior of the PdCu-based alloy is attributed to the operation of a galvanic interaction that causes dissolution of base metals and surface enrichment with primarily Pd. Dealloying, Ag-enrichment, and AgCl formation are thought to have contributed to the observed behavior of the PdAg-based alloy. These mechanisms are consistent with data from published ion release studies. SIGNIFICANCE: The allergenic potential of any Pd alloy is dependent on its propensity to develop a Pd-rich surface and thus release Pd+2 ions. The present study, though limited, has shown that electrochemical characteristics, namely OCP and polarization curves, can be used to identify such alloys. Further studies are warranted to evaluate the widespread applicability of these characteristics in distinguishing between Pd alloys that are biologically safe and those that are not.