An object-relational model for structured representation of medical knowledge

Domain specific knowledge is often not static but continuously evolving. This is especially true for the medical domain. Furthermore, the lack of standardized structures for presenting knowledge makes it difficult or often impossible to assess new knowledge in the context of existing knowledge. Possibilities to compare knowledge easily and directly are often not given. It is therefore of utmost importance to create a model that allows for comparability, consistency and quality assurance of medical knowledge in specific work situations. For this purpose, we have designed on object-relational model based on structured knowledge elements that are dynamically reusable by different multi-media-based tools for case-based documentation, disease course simulation, and decision support. With this model, high-level components, such as patient case reports or simulations of the course of a disease, and low-level components (e.g., diagnoses, symptoms or treatments) as well as the relationships between these components are modeled. The resulting schema has been implemented in AMOS II, on object-relational multi-database system supporting different views with regard to search and analysis depending on different work situations.     

Pathological mandibular fractures following third molar removal

Seventeen patients, who presented mandibular fractures following third molar removal, were treated in the Department of Oral and Maxillofacial Surgery at the University Hospital Freiburg between 2000 and 2004. Clinical and radiological data were analysed to evaluate the possible risk of fracture following third molar removal. Our data show an increased rate of pathological mandibular fractures in males over 40 years of age, following removal of a difficult lower wisdom tooth with a high retention grade that necessitated bone removal. Fourteen out of 17 fractures occurred postoperatively. In six cases, no fracture was visible in radiographs during the primary investigation. Pathological mandibular fractures were typically located anterior to the mandibular angle (n=15). We recommend informing patients about possible risks and, in selective cases, a soft diet for up to 4 weeks after the operation. A cracking noise reported by the patient is the most important indication of a fracture. If, initially, the fracture is radiologically undetectable, we recommend the use of radiological controls.     

Copper-zinc superoxide dismutase activity in normal and inflamed human dental pulp tissue.

Information regarding the presence of the free radical scavenging (inactivating, dismutating) enzyme superoxide dismutase in human dental pulp was sought. Free radicals, such as the superoxide anion radical (O2-) and the hydroxyl anion radical (OH.), are powerful biological oxidants produced by phagocytes during the normal tissue response to injury and infection. Also produced is hydrogen peroxide (H2O2), an aggressive oxygen species formed by the reaction of superoxide with itself, i.e., a dismutation in which one molecule of O2- is oxidized by the other. These three reactive oxygen intermediates serve as part of the normal host biological defense mechanism for the inactivation of microorganisms and the breakdown of their toxic products. Both normal and inflamed dental pulps were assayed for the presence of this enzyme. Superoxide dismutase activity was identified in the normal pulpal tissues. There was a slight decrease in activity with age. In the inflamed pulpal tissues, enzyme activity was markedly and significantly increased in comparison to that in the normal tissues. These observations indicate that human dental pulp possesses an endogenous defense mechanism designed to protect the tissue components (cells and matrix) from the toxic effects of the reactive oxygen intermediates. In this regard, the inflammatory response of this specialized and somewhat isolated (compartmentalized) tissue is not unlike that seen in other connective tissues.     

Lymphocyte levels in subjects with and without amalgam restorations

The claim that mercury from dental amalgam produces "reduced immunocompetence" was examined by measuring the levels of the three major populations of lymphocytes on 37 subjects--21 with amalgam restorations and 16 without. The results of this study show no indication that amalgam restorations affect the human immune system nor do they support the "reduced immunocompetence" claim.     

Infection-mediated early-onset periodontal disease in P/E-selectin-deficient mice

BACKGROUND: Retrospective and correlation studies suggest that early-onset periodontal disease may be due to a deficiency in phagocyte function, a pathogenic oral biofilm, and/or dysregulated gingival cytokine expression. Increased susceptibility to periodontal disease is therefore thought to result from multiple risk factors. METHODS: We tested this hypothesis prospectively using P/E-selectin adhesion molecule deficient mice that mimic the human syndrome leukocyte adhesion deficiency II. RESULTS: Our studies demonstrate that, in comparison to wild type animals, P/E-/- mice exhibit: spontaneous, early onset alveolar bone loss which is significant by 6 weeks of age; a 10-fold elevation in bacterial colonization of their oral cavities; and elevated gingival tissue levels of the bone resorptive cytokine IL-1alpha. Alveolar bone loss is completely prevented by prophylactic antibiotic therapy. CONCLUSIONS: These experiments provide the first prospective evidence for the multiple risk factor hypothesis of periodontal disease, and validate the first animal model for early onset periodontitis in which both the microbiota and host response can be systematically manipulated. P/E-/- animals should be useful in testing the virulence of putative periodontal pathogens, in determining the role of host resistance factors in periodontitis, in exploring the proposed relationship(s) between infection mediated alveolar bone loss and systemic health disorders, and exploring their genetic relationships.     

The effect of prophylactic polishing pastes and toothbrushing on the surface roughness of resin composite materials in vitro

Polishing composite restorations at recall prophylaxis may affect their surface roughness. This investigation evaluated the effect of prophy paste on the surface roughness of a microfilled (Filtek A110) and a microhybrid (Filtek Z250) resin composite before and after simulated toothbrushing. Twenty, two-sided samples of both materials were fabricated in acrylic molds against a Mylar strip (baseline). Three roughness readings were recorded for each surface using a Surfanalyzer 5400 to determine the mean roughness. The samples were finished and polished with the Sof-Lex disk system and the surface roughness (Ra) was re-measured. Samples were randomly assigned and five surfaces for each material were polished with Nupro coarse, medium, fine or Clinpro prophy paste and the surface roughness measured again. All surfaces were brushed 60,000 times at 1.5Hz using a 2N brush-head force (Manly V-8 cross-brushing machine) in a 50:50 (w/w) slurry of toothpaste and water. The surface roughness was measured followed by the application of prophy paste as previously described and this final roughness recorded. Data were analyzed using repeated measures two-factor ANOVA with TUKEY HSD pairwise comparison as appropriate (alpha = 0.05). No significant difference in surface roughness was determined between the microfilled and microhybrid materials at baseline or disk treatment, yet significant differences were observed following brushing and/or prophy paste application. In conclusion, although baseline and disk treated surfaces were not significantly different in microfilled versus microhybrid composites, subsequent prophy paste application and/or simulated toothbrushing caused significant differences.     

A rare complication of idiopathic osteosclerosis

Idiopathic osteosclerosis (IO) is described as a localized no expansible radiopacity with unknown etiology. The IO is generally asymptomatic and could appear as round, elliptical or irregular in shape. The internal aspect is usually uniformly radiopaque. IO should be distinguished from condensing osteitis of dental origin, or other alveolar bone related radiopacities such as periapical cemental dysplasia. This condition may cause changes in tooth position or problems during orthodontic treatment. The purpose of the present study is to report a case of tooth resorption caused by ectopic eruption rote caused by IO. This condition represents a rare complication of IO.     

The prevalence of dental erosion in a United States and a United Kingdom sample of adolescents

PURPOSE: A high prevalence of tooth surface loss due to erosion is well recognized in the United Kingdom (UK), but not in the United States (US). This could be due to prevalence or perception or a combination of both. The aim of this study was to measure the prevalence of erosion of the upper permanent incisors in US and UK samples of 11-13 year old children. METHODS: Convenience samples of 129 subjects were examined in the US and 125 in the UK by two trained examiners. The palatal and buccal surfaces of the upper permanent incisors were assessed for the presence of erosion. Subjects also completed a questionnaire investigating any association between the presence of erosion and possible etiological factors. RESULTS: The prevalence of erosion was 41% in the US and 37% in the UK samples, this difference was not statistically significant. Similarly no statistically significant difference was found between the sexes. The erosion present was confined to enamel in the vast majority of subjects. The questionnaire did not detect any link between the presence of erosion and possible etiological factors. CONCLUSION: The results of this study suggest that dental erosion is common in both US and UK adolescent populations. There is a need for a larger study to investigate this issue further.     

Racial/ethnic variations of practicing dentists

BACKGROUND: In recent years, the dental school population has changed from being predominantly white male to a more diverse racial and ethnic makeup. Noting this change in the student population, the American Dental Association undertook an in-depth study of the various racial/ethnic groups. METHODS: Questionnaires were sent to approximately 8,000 dentists nationwide. Samples were drawn for each of the following racial/ethnic groupings: white, black, Hispanic, Native American and Asian. The survey instrument asked questions about personal characteristics, work and private practice issues, household and practice income, and patient characteristics; it also asked for dentists' opinions. A final adjusted response rate of 57.0 percent was achieved. RESULTS: The majority of all dentists responded that they were "very satisfied" with their profession, but the survey found variations in patient mix, employment history and provision of free or discounted care. CONCLUSIONS: The survey examined dentists by race/ethnicity to identify differences and similarities. Cultural and ethnic minorities are the fastest growing segment of the U.S. population. As the profession becomes more diverse, practice patterns will affect the overall dental profession. PRACTICE IMPLICATIONS: Dentists' racial/ethnic backgrounds may change the provision of care as patient mix varies, with each dentist group treating a specific group of patients in regard to family income, racial/ethnic background and subgroups for whom they offer free or reduced-rate dental care.