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Biomedical subjects

C M Cobb

Publications and source records attributed to C M Cobb.

At least 91 records · Page 5Linked to original sources
PubMed1989

The effect of 2% chlorhexidine digluconate irrigation on clinical parameters and the level of Bacteroides gingivalis in periodontal pockets.

Eight patients with moderate periodontitis volunteered to participate in a study to assess the effect of subgingival 2% chlorhexidine irrigation, with and without scaling and root planing, on clinical parameters and the level of Bacteroides gingivalis in periodontal pockets. Each quadrant was required to have at least one site with a probing depth of 6 mm or greater and bleeding on probing. The patients were treated following a randomized four quadrant design: one quadrant received no treatment; a second quadrant received scaling and root planing only; a third quadrant received chlorhexidine irrigation only; the fourth quadrant received scaling and root planing, plus chlorhexidine irrigation. Sites to receive chlorhexidine were irrigated at 0, 1, 2, and 3 weeks. Clinical and microbiological indices were measured and recorded at 0, 5, 7, 11, and 15 weeks. The clinical parameters measured included; Plaque Index (PI), Gingival Index (GI), probing depth (PD), Bleeding Tendency (BT), and attachment level (AL). The attachment level was measured using an occlusal stint as a fixed reference point. The level of Bacteroides gingivalis was measured by labeling the plaque sample with a polyclonal fluorescent antibody. The plaque smear was then read using a fluorescent microscope at 1000 magnification. The Spearman Rank-Order Correlation was used to determine the relationship between parameters at baseline. The effects of the treatment groups were compared using the Neuman-Keuls Multiple Comparison Technique. The results showed that a positive correlation existed between B. gingivalis (rs = 0.68) and Bleeding Tendency and between P1I (rs = 0.77) and GI.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Assessment of curette sharpness.

Nothing to date has appeared in the literature addressing the relationship of specific bevel dimension and clinical sharpness of curette blades. This study investigated the degree of clinical sharpness of Gracey curettes following four periods of simulated root planning and, using the scanning electron microscope (SEM), determined the approximate number of strokes at which loss of clinical sharpness became apparent. Seventy-five new stainless steel curette blades were standardized and randomly assigned to one of five groups: control, 30-stroke, 50-stroke, 70-stroke, and 90-stroke. With the exception of the control group, blades underwent a simulated root-planing procedure, on extracted, periodontally involved teeth, which employed a device to standardize pressure and stroke length. Blades were then tested for clinical sharpness using light reflection, with two degrees of magnification; and plastic stick, a tactile evaluation. Blades were photographed under the SEM at a magnification of x1,000. Bevel width was measured at 10 standardized locations on the photomicrographs, and a mean was calculated. Nonparametric data were analyzed using the Kruskal-Wallis statistical test and SEM parametric data using ANOVA and post hoc Newman-Kuels tests. Results showed no significant differences among treatment groups when either tactile or magnification sharpness tests were used. Analysis of the SEM data showed no statistically significant differences among bevel dimensions for any of the five groups. A Spearman rank order correlation, used to compare the clinical data to the SEM bevel measurements, showed no correlation of clinical sharpness and SEM-determined bevel dimension.

Dental Instruments↗
PubMed1989

Effects of an air-powder abrasive system on plasma-sprayed titanium implant surfaces: an in vitro evaluation.

The purpose of this study was to conduct an in vitro evaluation of the effects of an air-powder abrasive system, commonly used in clinical dentistry for periodontal maintenance, on the surfaces of plasma-sprayed titanium dental implants. Twenty-eight plasma-coated titanium implant specimens were divided into a sterile water-treated control group and an air-powder-abrasive-treated test group. All specimens were subjected to three different in vitro testing conditions and post-treatment evaluations by scanning electron microscopy (SEM): (1) Topographical features of implant surfaces were studied before and after direct exposure to the abrasive; (2) biocompatibility of treated implant surfaces was evaluated and compared with those of control specimens via in vitro fibroblast attachment studies; and (3) the attachment of a common oral microbe to the implant surface and its subsequent removal by exposure to the air-powder abrasive were also evaluated. Results indicate that exposure of implant specimens to the air-powder abrasive for various periods resulted in only slight changes in surface topography, i.e., rounding of angles and edges of the plasma-spray coating and occasional surface pitting. Examination by SEM and a statistical comparison of the difference between the mean numbers of attached fibroblasts between control and test groups revealed no statistical significance. In both specimen groups, fibroblasts exhibited uniform attachment over the entire implant surface. A comparison of test and control groups demonstrated 100% removal of bacteria from the surfaces of test specimens exposed to the air-powder abrasive and approximately a 75% removal from control specimens exposed to sterile water.

Bacterial Adhesion↗
PubMed1988

Ultrastructural examination of human periodontal pockets following the use of an oral irrigation device in vivo.

To date, there are no ultrastructural studies that have examined untreated chronic periodontal pockets immediately following dental debridement with an oral irrigation device. This study used both scanning electron microscopic and transmission electron microscopic methodology to examine previously untreated human periodontal pockets after their exposure to a pulsating oral irrigation with saline solution. A comparison of 16 untreated controls with 16 test specimens revealed qualitative differences in microbial morphotypes at various pocket depths. Control specimens at all pocket depths examined (0-6 mm), exhibited a mixed microbial flora consisting of cocci, short rods, and filamentous organisms. Specifically at 3- to 4-mm and 5- to 6-mm levels in control specimens, spirochetes, fusiforms, and branching organisms were obvious. In contrast, test specimens exhibited a few cocci and short rods at 0- to 2-mm and 3- to 4-mm levels and a mixed flora at the 5- to 6-mm level. There was no observable difference between control and test specimens concerning epithelial topography, cavitations, microulcerations, spatial relationships, and individual cell appearance. Both control and test specimens exhibited a mild spirochete invasion of the epithelial strata. Collectively these observations suggest that pulsating oral irrigation effects a qualitative change on subgingival plaque and is not injurious to the soft tissues.

Adult↗
PubMed1987

Effect of an air-powder abrasive system on root surfaces in periodontal surgery.

The purpose of this study was to compare the effectiveness of an air-powder abrasive technique to conventional root planing during periodontal surgery. 7 patients scheduled for multiple extractions of periodontally-involved teeth were selected. Full thickness mucoperiosteal flaps were reflected, and proximal surfaces of 32 teeth were either ultrasonically scaled and exposed to the air-powder abrasive, or ultrasonically scaled and then manually root planed. Following extraction, teeth were stained for residual plaque and photographed, or prepared for scanning electron microscopy. The air-powder abrasive technique used for surgical root preparation was found to produce a root surface favorably comparable to manual root planing with regard to removal of plaque, calculus, and exposed cementum. A mean of 80 micron of cementum was abraded away after 40 s of exposure to the air-powder spray. The air-powder abrasive spray demonstrated an advantageous ability to remove plaque and cementum from areas of difficult access, such as furcations and root flutings.

Dental Prophylaxis↗
PubMed1984

The effect of an air-powder abrasive system on in vitro root surfaces.

An air-powder abrasive system, the Prophy-Jet model C-100, is now available for use by the dental community. However, its use has been restricted to cleaning enamel surfaces of stain and dental plaque. The purpose of this investigation was to ascertain the effects of this air-powder abrasive system on root surfaces of extracted human teeth. Thus, root surfaces of 20 teeth were covered with a template consisting of a metal band with a centrally located 2-mm diameter hole. The banded root surfaces, under controlled conditions, were exposed to the air-powder abrasive for 30 seconds. The resulting defects were measured by using a light microscope equipped with a graduated focus knob. Three teeth were randomly selected for examination by scanning electron microscopy and one was selected for histologic evaluation by light microscopy. Untreated extracted teeth were used as controls. In addition, one untreated tooth root was exposed to the air-powder abrasive without use of the template. In this instance, a brush stroke was used for approximately 1 minute, as might be done in a clinical situation. This tooth root was also examined by scanning electron microscopy. The Prophy-Jet air-powder abrasive system removed an average of 636.6 micrometers of root structure in 30 seconds of exposure time. The resulting surface was smooth, free of connective tissue fibers and debris, and all cementum was removed. Few open dentin tubules were observed since most appeared to have been obliterated. The powder crystals, as viewed by scanning electron microscopy, were sharp-pointed, somewhat elongated and of varying lengths. The Prophy-Jet air-powder abrasive system appears to have considerable potential for treatment of periodontally diseased root surfaces. However, its use should be tempered by the results of this and future research and sound clinical judgment.

Air↗
PubMed1983

Acute necrotizing ulcerative gingivitis. A transmission electron microscope study.

The purpose of this study was to provide additional evidence that in the lesions of acute necrotizing ulcerative gingivitis (ANUG), spirochetes and other microorganisms are capable of invading the nonnecrotic lamina propria of affected gingivae. Biopsies from eight patients with pathognomonic signs of ANUG were obtained under local anesthesia and processed for light and transmission electron microscopy. The results indicated that spirochetes and other bacteria are capable of penetrating the viable connective tissues of the lamina propria. The four zones of the ANUG lesion as first described by Listgarten were observed without difficulty. The maximum depth of bacterial infiltration into the lamina propria ranged from 155 to 400 microns from the nearest epithelial basal lamina. The histologic picture of the ANUG lesion did not always conform to the acute clinical manifestations.

Adolescent↗
PubMed1982

Connective tissue attachment to periodontally diseased roots after citric acid demineralization.

PREVIOUS INVESTIGATIONS have demonstrated that application of citric acid to a root surface results in exposure of dentin and/or cementum matrix collagen fibrils. Several studies have suggested a rapid and consistent connective tissue reattachment to citric acid treated roots. This study was initiated to determine if such an attachment was obtainable on human periodontally diseased teeth, in vivo, and could be confirmed through observations using the scanning electron and light microscopes. Full thickness flaps were raised on 18 single rooted teeth with moderate to advanced periodontitis. Citric acid (pH = 1.0) was applied to nine teeth with contralateral teeth serving as controls. Six to fifteen weeks later, the teeth with attached periodontal tissue were removed. Sagittal sections were obtained, with one-half of the root being processed for light microscopy and the remaining half studied by scanning electron microscopy. Six of nine citric acid treated roots provided evidence of fibrous attachment. Connective tissue was apposed directly to old or newly formed cementum, but never directly to dentin. Fibrous attachment was usually functionally oriented, i.e., perpendicular to the root surface. No evidence of fibrous attachment was found among the control specimens.

Citrates↗
PubMed1976

Activation of fibroblast procollagenase by mast cell proteases.

Proteases capable of activating procollagenase from gingiva and from fibroblast and macrophage monolayer cultures were harvested from homogenates of canine tumor mast cells. The mast cell proteases lysed casein and Azocoll but not native collagen. In low salt concentrations the enzymes existed at high molecular weight complexes, which were dissociated by increasing the salt concentration above 1.0 M (NaCl, KCl). Gel filtration in 1.4 M KCl separated the protease activity into three peaks, all of which activated procollagenase. Two of the enzymes showed substrate specificities (hydrolysis of p-tosyl-L-arginine methyl ester and benzoyl-tyrosine ethyl ester) and reactive center reactivities similar to pancreatic trypsin and chymotrypsin. Based on gel filtration, apparent molecular weights of 160 000 (p-tosyl-L-arginine methyl ester esterase), 90 000 (main procollagenase activator) and 36 000 benzoyl-tyrosine ethyl ester esterase) were determined. Activation of procollagenase resulted in a 18-20 000 decrease of the molecular weight. The activation was directly related to the amount of activator added within certain limits. Further addition of activator resulted in proteolytic inactivation of collagenase.

Animals↗
PubMed1976

Synthesis and release of procollagenase by cultured fibroblasts.

An inactive collagenase was harvested from both serum-free and serum-supplemented fibroblast monolayer cultures in periods of active collagen synthesis. The latent collagenase did not hydrolyze collagen and did not bind the potent collagenase inhibitor alpha2-macroglobulin. Activation with trypsin imparted to the enzyme the ability to hydrolyze collagen at neutral pH in a typical manner and to form an inhibited complex with alpha2-macroglobulin. The molecular weights, determined by calibrated gel filtration, were 78,000 and 60,000 for the latent and active enzymes, respectively. The data indicate that collagenase is released from the cells in inactive form, as a zymogen.

Amino Acids↗
PubMed1976

Procollagenase from bovine gingiva.

1. Collagenase (EC 3.4.24.3) is released from bovine gingival explants in vitro as a zymogen. The zymogen does not hydrolyze collagen and does not form a complex with alpha2-macroglobulin (alpha2-M). It elutes in gel filtration with an apparent molecular weight of approx. 80 000. 2. Incubation of the zymogen with trypsin results in a 15 000-20 000 dalton decrease in molecular weight and imparts to the enzyme the ability to hydrolyze collagen and to form a complex with alppha2-M. 3. The zymogen can be completely separated from the active enzyme to alpha2-M. Likewise, the zymogen can be harvested from cultures supplemented with serum.

Animals↗
PubMed1976

Potential of elastin and collagen as initiators of in vivo calcification.

The osseous repair response of the guinea pig to purified bovine elastin from ligamentum nuchae and decalcified rat femur collagen was studied by implantation of these materials into an extraction socket. A nylon mesh tube was used to carry the respective implant materials to place, and in one group of animals only the nylon tube was implanted, thereby serving as a control for the study. Neither the collagen or elastin matrix appeared to elicit an immune rejection response from the host animal. Histologic and quantitative results indicated that collagen implants accelerated the osseous repair of the extraction socket. Elastin implants, which characteristically resulted in ossicle formation, did not appear to accelerate healing, but the results were quantitatively similar to those in the experimental control animals.

Alveolar Process↗