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Biomedical subjects

W R Moorer

Publications and source records attributed to W R Moorer.

At least 37 records · Page 2Linked to original sources
PubMed1989

Particles and molecules in endodontic leakage.

It is assumed that above a critical level, microleakage causes periapical disease and jeopardizes periapical tissue repair. The purpose of this investigation was first to find out to what degree obturation prevents leakage of bacteria-sized particles or large protein molecules, and second if leakage of the commonly used dye methylene blue is comparable with that of a small bacterial metabolic product of similar molecular size. Sections, 9 mm long, obtained from 46 extracted human incisor roots had their root canals prepared in a standardized manner and obturated in four experimental ways using gutta-percha. The root sections were mounted in the middle of tubes that were closed at both ends with rubber membrane stoppers, which permitted sampling from the apical reservoir. The coronal reservoir was filled with a solution of 1 mg/ml latex beads, 4 micrograms/ml endotoxin, 0.5 per cent butyric acid, 0.1 per cent valeric acid and 0.1 per cent methylene blue water. After 1 and 2 weeks, samples were taken from the apical reservoir and tested for the presence of latex beads by phase-contrast microscopy, for endotoxin with a limulus lysate test, for butyric acid with gas-chromatography and for methylene blue with spectrophotometric analysis. Leakage of bacteria-sized particles and large-sized protein molecules could be prevented only when both sealer and pressure were used in obturating root canals with gutta-percha. Leakage of butyric acid proved to be comparable with leakage of methylene blue; microleakage of these small molecules could not be prevented in this study whatever method of filling was used.

Dental Leakage↗
PubMed1989

Capacity of anaerobic bacteria enclosed in a simulated root canal to induce inflammation.

In an effort to simulate the infected dental root canal, bacteria were enclosed in polyethylene tubes that were subcutaneously implanted into rats. Four different bacterial combinations, selected from nine oral species, were tested. The contents of 144 inoculated and implanted 'root canals' were analysed after 2 and 4 weeks of implantation. Bacteroides, Streptococcus, Actinomyces and Fusobacterium were inoculated in low numbers but dominated the mixed flora at the end of the experiment. The bacteria-filled tubes induced inflammation of the rat tissue at the implant opening ('foramen'). It is confirmed that mixed bacterial populations survive, show succession and develop within an enclosed environment. Such florae cause significant inflammation at the interface with the host tissues.

Animals↗
PubMed1989

[Pain, flare-ups and failures in root canal therapy].

In this overview the incidences and causes of pain, flare-ups and failures that occur after root canal therapy are discussed. Infection is considered the most important single, underlying determinant of the many factors that may cause pain and failures. Therefore, strict adherence to recognized therapeutic principles of shaping, disinfection and filling, in addition to proper aftercare, is of importance to diminish postoperative sequelae.

Humans↗
PubMed1986

Experimental gingivitis in relation to susceptibility to periodontal disease. II. Phase-contrast microbiological features and some host-response observations.

In the present investigation, a number of histological and immunohistochemical characteristics of periodontal tissues as well as the phase-contrast microscopy of dental plaque were studied after experimentally-induced gingival inflammation in relation to susceptibility to periodontal disease. The study included a younger (mean age 34.1 years) and an older age group (mean age 48 years) with a reduced but healthy periodontium. Both age groups had the same amount of loss of attachment which may suggest that they had different degrees of susceptibility to periodontal disease. At the start of the experiment, each patient was instructed to abstain from oral hygiene in one quadrant of the mouth for a period of 18 days. At the end of the 18-day period, supra-gingival plaque and gingival tissue samples were taken. As determined by phase-contrast microscopy, the plaque samples of both age groups contained relatively high proportions of spirochetes. This may indicate that the patients are at risk for recurrence of periodontal breakdown. The general histopathologic picture of the gingival tissue samples of both age groups was similar to the so-called 'early lesion'. However, IgA-producing plasma cells were found in most tissue samples of both age groups. The first part of this study showed that the younger, in comparison to the older, patients developed inflammation in terms of bleeding on probing more rapidly. These clinical results cannot be explained by the host-parasite parameters investigated in the present study.

Adult↗
PubMed1986

Bleeding/plaque ratio and the development of gingival inflammation.

In a recent publication, it was hypothesized that the ratio between bleeding and plaque scores may act as a prognostic indicator for periodontal breakdown. Furthermore, it was found that the rate of development of gingival inflammation in terms of bleeding on probing during experimental gingivitis is more rapid in patients susceptible to periodontal breakdown than in subjects insusceptible to periodontal breakdown. The purpose of the present investigation was to compare the gingival reaction to dental plaque in an experimental gingivitis study in individuals without periodontal breakdown, having either a low or a high bleeding/plaque ratio. A group of 8 volunteers (18-23 years) with a low bleeding/plaque ratio and 7 volunteers (19-22 years) with a high bleeding/plaque ratio were selected. In both groups, an experimental gingivitis study of 23 days duration was carried out. Results showed that individuals with a high bleeding/plaque ratio developed significantly more clinical inflammation in terms of bleeding and swelling of the gingiva than individuals with a low bleeding/plaque ratio. After 23 days of plaque accumulation, gingival biopsies as well as supragingival plaque samples were taken from both groups. Phase-contrast microscopy of the plaque samples showed no significant differences between the 2 groups. Low %s of spirochetes and motile rods were found. Stereologic point-counting procedures showed equal amounts of infiltrated connective tissue in both groups. However, significant differences in composition of the infiltrate appeared to be present. The high ratio group showed more IgA producing plasma cells and complement activation than the low ratio group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Abscess formation induced in rabbits with bacteria-filled subcutaneous implants that simulate the infected dental root canal.

Short-term and semi-long-term tissue reactions to a mixture of "endodontopathic" bacteria are described. The bacteria are enclosed in experimental implant tubes simulating some aspects of the infected dental pulp. Localized abscesses develop in response to mixed bacterial contents of the implants. No abscess formation occurred with pure cultures (that is, either component of the mixture). Pathogenic inocula attract leukocytes to the adjacent tissues, which become inflamed and cause influx of leukocytes into the lumen of the implant proper.

Abscess↗
PubMed1985

[Focal infection].

Explore the source record for details and available documents.

Focal Infection, Dental↗
PubMed1984

Plaque and systemic disease: a reappraisal of the focal infection concept.

The review presented here covers metastatic local and systemic disease secondary to the accumulation of plaque or the formation of other pathogenic microbial depots in the mouth. At least 3 pathways may link oral infection to secondary disease, to wit metastatic infection due to transient bacteremia, metastatic immunological injury, and metastatic toxic injury. The available evidence is presented and examples are provided. They concern among others such divergent diseases as acute bacterial myocarditis, infective endocarditis, brain abscess, uveitis and iridocyclitis, trigeminal and atypical facial neuralgia, unilateral facial paralysis, fever of "unknown' origin, and neutrophil dysfunction.

Antibodies, Bacterial↗
PubMed1982

Evidence for antibacterial activity of endodontic gutta-percha cones.

In the presence of endodontic gutta-percha cones, several species of bacteria were killed in vitro. Silver points, when compared with gutta-percha cones, were not or were considerably less effective against the target organism. Staphylococcus aureus, in our assay system. Growth of bacteria in serum could be abolished by the mere presence of gutta-percha, especially when time was allowed for previous contact between the serum and the cones. It is concluded that gutta-percha cones possess a slowly acting, relatively weak, but, in our opinion, significant inherent antimicrobial property.

Bacteria↗
PubMed1982

Antibacterial activity of gutta-percha cones attributed to the zinc oxide component.

Growth of several species of bacteria was inhibited by the presence of endodontic gutta-percha cones. Microbiologic analysis, measurement of osmolarity, microscopy, x-ray diffraction analysis, and scanning electron micrography were used to identify the biologically active component that slowly leaches from gutta-percha cones. This component is zinc oxide in the form of small solid particles, from which active, soluble Zn2+ ion is mobilized by hydrolysis. A hypothesis on the "depot" effect of the ZnO particles is formulated, and is used to discuss some earlier reported literature on toxic and antibacterial activity of zinc oxide-containing materials. It is concluded that zinc oxide is not to be considered an inert compound. Its widespread uses in medicine and dentistry seem to reside in its "inert," biocompatible, and astringent properties mainly. The biologically active role of zinc oxide, however, merits further investigation.

Bacteria↗