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Biomedical subjects

M A Listgarten

Publications and source records attributed to M A Listgarten.

At least 73 records · Page 4Linked to original sources
PubMed1986

A perspective on periodontal diagnosis.

Periodontal diseases are best considered as the outcome of an imperfect host-parasite interaction. In most cases, diagnosis involves labelling certain clinical manifestations without a complete understanding of the causes of the disease. Therefore, treatment based on the "diagnosis" is not necessarily logical or effective. As the causes which underly the disease become more evident, the underlying mechanisms of disease can be used to refine our diagnostic methods. For example, deficiencies in host defenses, or the presence or increased proportions of certain bacterial pathogens may be indicative of imbalances in the normal host-parasite equilibrium. For a laboratory test to be reliably applied to the diagnosis of a clinical condition, it is essential that an absolute criterion of the clinical disease first be established. Then the sensitivity and the specificity of the test can be determined using appropriate experimental designs. The demonstration of a good correlation between a test outcome and a clinical condition is, of itself, insufficient grounds to use the test for diagnostic purposes.

Adolescent↗
PubMed1986

Pathogenesis of periodontitis.

Periodontitis is an inflammatory disease of the periodontium which is characterized by a progressive destruction of the tissues supporting the tooth. Its primary etiology is an ill-defined series of microbial infections which may be composed of only some of the more than 300 species of bacteria currently recognized in the oral cavity. The disease is currently considered to progress as periodic, relatively short episodes of rapid tissue destruction followed by some repair, and prolonged intervening periods of disease remission. Despite the apparent random distribution of episodes of disease activity, the resulting tissue breakdown exhibits a symmetrical pattern of alveolar bone loss and pocket formation which is common to several forms of periodontitis, although the distribution of the most affected teeth and surfaces may vary among diseases (e.g., juvenile periodontitis versus adult periodontitis or rapidly progressive periodontitis). Several reports have indicated that bacterial cells can be found in the pocket wall of periodontitis lesions. The translocation of bacteria into the tissues from the pocket environment is quite common, as evidenced by the common occurrence of bacteremias in patients with periodontitis following relatively minor events such as chewing and oral hygiene procedures. However, it is important to distinguish between the passive introduction of bacteria into periodontal tissues and frank invasion as might occur in an acute infection, since the pathological implications may be quite different.

Adult↗
PubMed1986

Ultrastructure of durapatite-periodontal tissue interface in human intrabony defects.

The ultrastructure of the interface between Durapatite (hydroxylapatite) and human periodontal tissues was examined. Durapatite was implanted into the intrabony periodontal defects during periodontal surgery. Reentry procedures were performed after 1 year and the tissues in the defects were biopsied and processed for transmission electron microscopy. Nineteen tissue blocks from four patients were examined, 17 contained Durapatite particles embedded in fibrous tissue and two contained particles encased in bone, all without inflammation. The fibrous connective tissue consisted of densely packed collagen fibrils surrounding the implant particles. The bone surrounding the Durapatite consisted in one case of relatively mature bone, and in the other of osteoid tissue. A granular, amorphous, collagen-free, electron-dense layer was routinely observed between implant and tissue. This layer was thicker in the bone-encased samples than in those surrounded by fibrous connective tissue. Except for the particle surrounded by mature bone, this layer was continuous with an organic meshwork located on the periphery of the implant spaces. The ultrastructural features of the interface are consistent with the existence of a mucopolysaccharide "bonding zone" described by other investigators. The organic meshwork appears to outline areas similar in size and shape to the individual crystallites of hydroxylapatite. This may indicate that the reactive surface of hydroxylapatite is much larger than merely the exterior surface of the implant, a finding which may explain the apparently good tissue adhesion to the implant.

Alveolar Process↗
PubMed1985

3-year longitudinal study of the periodontal status of an adult population with gingivitis.

69 adults ranging in age from 20 to 73 (mean age: 37) were randomly assigned to a control (C) and a test (T) group. Of these, 61 completed the 3-year longitudinal study. All subjects had varying degrees of gingivitis at the start, but no overt periodontitis. Following a base line examination for P1I, GI, probing depth (PD) and recession, a differential darkfield microscopic (DDFM) count of subgingival bacterial morphotypes was carried out on a pooled sample originating from one tooth surface in each sextant with the greatest probing depth. Examinations were repeated every 6 months for 3 years. The C group received regular prophylaxes every 6 months. The T subjects received prophylaxes according to a previously described schedule, and on the basis of the DDFM test outcome. Recall intervals at the end of the study for the T group ranged from 1 to 24 months (mean: 15.7 months). Of 30 subjects in the T group at the end of the study, one half had not had their teeth cleaned for periods of 18 to 36 months without any detectable deterioration in their periodontal status by comparison with the other T subjects or the patients in the C group. Both C and T subjects exhibited increased mean P1I and GI scores as compared to base line during the first half of the study. However, mean PD measurements remained unchanged. Increases in PD from base line of 3 mm or more were observed only in approximately 1 out of a 1000 individual tooth surface comparisons, a frequency comparable to that expected to occur by chance alone. This observation indicates that in this population, little if any pocket formation occurred during the study period. GI score increases of 2 units or more occurred in relatively few subjects. 2 of 31 C patients accounted for 42% of the affected dental units, while 5 out of 30 T subjects accounted for 40.8% of the affected dental units in that group. These observations suggest that despite the relatively high prevalence and incidence of gingivitis, the subjects were relatively resistant to periodontitis. Neither preventive schedule was effective in eliminating gingivitis. The lack of significant destructive disease in this population prevented any meaningful comparison of the relative effectiveness of the two preventive maintenance regimens in preventing recurrences of periodontitis.

Adult↗
PubMed1985

The colonization and establishment of invading bacteria in periodontium of ligature-treated immunosuppressed rats.

The morphologic features and pattern of bacterial invasion of the periodontal tissue in ligature-induced periodontal defects of immunosuppressed rats were studied. Silk ligatures were placed circumferentially on the maxillary left second molar of 24 Sprague-Dawley rats. The treatment group (14 rats) received Cytoxan (75 mg/kg) the day after ligature placement and at Day 4. The control group (10 rats) received no medication. All animals were sacrificed on Day 8 and the maxillae processed for light and electron microscopy. Only ligated sites in immunosuppressed animals exhibited bacterial invasion. Invading bacteria consisted of microcolonies of Gram-negative and Gram-positive coccoid cells and rods located near the tissue surface. Each microcolony consisted of morphologically homogeneous microorganisms. The deeper sites revealed a diffuse invasion of Gram-negative rods which appeared morphologically similar. Other features associated with invasion were complete destruction of epithelial tissue next to the ligature and the lack of inflammatory cells in the gingival region. These findings, when compared to those of other reports of tissue penetration by bacteria, point to the necessity of differentiating between bacterial invasion of gingival tissues, associated with penetration of tissues by proliferating bacteria, and bacterial translocation, a situation in which bacteria are passively carried into the tissues, for example by mechanical manipulation immediately before or during biopsy taking, or possibly during processing for histology.

Alveolar Process↗
PubMed1984

Helical flagellation in Centipeda periodontii, a gram-negative, anaerobic bacillus from periodontitis lesions.

The insertion pattern of flagellation of Centipeda periodontii was determined from electron micrographs of negatively stained cells treated with various detergents to remove their outer cell wall layer(s) selectively. The best results were obtained with 0.2% sodium dodecyl sulphate and a treatment time of 1-2 min. Detergent-treated cells displayed a unique helical pattern of flagellation which we designate as helicotrichous (Gk n. helix, helix + Gk n. thrix, hair). Flagella originated from an electron-dense region approximately 180 nm wide, which spiraled around the cell body. The length of the insertion path averaged 2.6 micron per 360 degrees turn; its periodicity was 2.5 micron. An average of 19 flagella were inserted per 1 micron length of the electron-dense region. The effects of cell division and branching on flagellation were also examined.

Bacteria, Anaerobic↗
PubMed1984

Comparative differential dark-field microscopy of subgingival bacteria from tooth surfaces with recent evidence of recurring periodontitis and from nonaffected surfaces.

Ninety-two subjects with a history of treatment for chronic periodontitis were monitored on a regular basis for an average period of 10.7 months. During this monitoring period, in spite of their participation in a preventive maintenance program, 19 subjects out of 92 showed evidence of significantly increased probing depth (greater than or equal to 3 mm from base line measurements) on at least one tooth surface, or approximately 1% of the dental units at risk in this population. A comparison of differential microscopic counts of subgingival bacteria from the affected tooth surfaces with a pooled sample of 6 other surfaces with the greatest probing depth, in the same mouth, taken at the same appointment, revealed no significant differences between proportions of coccoid cells, spirochetes, motile rods or other cell types. These findings suggest that disease recurrence, as measured by a comparatively rapid increase in probing depth, might be accounted for on the basis of the following hypotheses: an alteration in the host response without a detectable change in the composition of the subgingival microbiota, a qualitative change in the microbial flora not detectable by a microscopic assay, relatively brief episodes of disease activity which may be accompanied by brief, transient, qualitative changes in the local microbiota that cannot be readily detected by biannual examinations.

Bacteria↗
PubMed1984

Suppression of human lymphocyte responses by oral spirochetes: a monocyte-dependent phenomenon.

Spirochetes have been implicated in the pathogenesis of several human infections including syphilis, yaws, Lyme disease, and periodontal diseases. We examined soluble sonic extracts of oral spirochetes (Treponema denticola and T. vincentii) for their ability to alter human lymphocyte function. These organisms were isolated from subgingival plaque of patients with periodontitis. We found that sonicates of several but not all strains of T. denticola caused a dose-dependent inhibition of human lymphocyte responsiveness to Con A, PHA, PWM, and the recall antigen SKSD. Suppression involved alterations in DNA, RNA, and protein synthesis; there was no effect on cell viability. In contrast, sonicates of T. vincentii (medium-sized spirochetes) had no demonstrable effects on lymphocyte activation. The suppressive factor derived from T. denticola is heat-labile with a m.w. of approximately 100,000. To achieve maximal suppression, sonicates had to be added during the first 24 hr of incubation; there was no inhibition observed when added at 48 or 72 hr (along with 3H-TdR). Suppression was dependent on the presence of adherent monocytes; removal of these cells prevented spirochete-induced suppression of lymphocyte proliferation. Furthermore, the combination of indomethacin and catalase were able to reverse (or prevent) the inhibitory effects of the spirochete extracts, demonstrating a requirement for both prostaglandins and hydrogen peroxide. The potential role of such suppressive factors in periodontal disease is discussed.

Humans↗
PubMed1982

Differential dark field microscopy of subgingival bacteria as an aid in selecting recall intervals: results after 18 months.

Differential dark field microscopic examination of subgingival microbial forms has been used to assign customized recall intervals to a population of adults with minimal periodontal disease. Results after 18 months indicate that a substantial proportion of the test subjects remained in good periodontal health despite the absence of regular biannual prophylaxes. One half of these subjects, who had not received a prophylaxis for periods of 15-18 months, did not demonstrate any detectable worsening of their periodontal status. No correlation could be established in this population between proportions of certain microbial forms and susceptibility to gingivitis.

Adult↗
PubMed1982

Bacterial variability within diseases periodontal sites.

The purpose of this study was to examine the variability in bacterial proportions between individual periodontal sites in patients with chronic periodontitis by means of differential dark-field microscopy. Fourteen patients with untreated, moderate to advanced disease were included. Probing depth, plaque and gingival index scores were recorded for each patient. Microbial samples were collected from the tooth surface with the greatest proving depth in each sextant and examined individually by dark-field microscopy. The results indicated that proportions of spirochetes and motile rods at any given probing depth varied considerably, ranging from those expected at healthy sites to those expected at diseased sites. In accordance with previous studies, mean percentages of spirochetes tended to vary directly with increased PD, PlI and GI scores, while mean percentages of coccoid cells tended to follow a reverse pattern. However, no significant correlations could be demonstrated when measurements from individual sites were analyzed. Most of the variance in the data was due to differences between subjects rather than differences between sites. It is postulated that the large variance between subjects and sites is due in part to the cyclical nature of the disease and to the lack of synchrony between remissions and exacerbations at different sites and in different patients.

Adult↗