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Biomedical subjects

C M Cobb

Publications and source records attributed to C M Cobb.

At least 55 records · Page 3Linked to original sources
PubMed1995

Microscopic appearance of enamel white-spot lesions after acid etching.

Ultrastructural changes in surface characteristics of enamel white-spot lesions were compared with changes in the adjacent clinically sound enamel after they were etched with 30% phosphoric acid. Ten human permanent first molars exhibiting natural white-spot lesions were used as study specimens. The lesion surfaces and their adjacent sound enamel were etched with 30% phosphoric acid for 60 seconds. Specimens were then evaluated by polarized light microscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The acid etching produced a porous surface on both the white-spot lesion and the surrounding sound enamel. However, the lesion surface appeared to be more resistant to acid and dissolved less than adjacent enamel. This difference in acid solubility produced a steplike appearance between a white-spot lesion and its adjacent enamel surface. Energy-dispersive spectroscopy demonstrated no difference in relative calcium-phosphorus ratios among the acid-etched white-spot lesion, acid-etched sound enamel, and unetched sound enamel.

Acid Etching, Dental↗
PubMed1995

Histologic evaluation of alveolar bone following CO2 laser removal of connective tissue from periodontal defects.

This study was undertaken to examine histologically the healing response of alveolar bone following removal of granulation and/or connective tissues from interproximal craters by manual curettage or ablation by carbon dioxide laser. The time required to complete each type of degranulation procedure was also compared. Four interproximal treatment sites in each quadrant of two dogs were randomly assigned to each treatment modality. Neither treatment modality was totally effective in removing all suprabony connective tissue. Healing was clinically uneventful and histologically similar for both treatment groups at all time intervals. Laser-treated specimens exhibited little or no inflammatory cell infiltrate, areas of heat-induced tissue necrosis, accumulations of carbonized debris that initially was surrounded by macrophages and eventually phagocytized by multi-nucleated giant cells, and spicules of nonvital bone that exhibited a surface layer of osteoid. Although manual curettage was found to be statistically significantly faster, the difference between mean times was roughly 55 seconds and therefore unlikely to be clinically significant.

Alveolar Bone Loss↗
PubMed1994

Dentinal tubule anastomosis: a potential factor in adhesive bonding?

This study investigated adhesive tag formation within dentinal tubules and the anastomosing of lateral canals observable with scanning electron microscopy. This mechanism of micromechanical bonding had not been studied previously. The following brands of adhesives were applied to the prepared dentin surface of unerupted human third molars: Scotchbond Multipurpose, C&B Metabond, All-Bond 2, both etched and unetched, Tenure Solution, and XR-Bond. The experimental specimens were decalcified and prepared for SEM examination. Many tubule resin tags with lateral branching were observed. The resin branches were the result of primer, adhesive, or both entering lateral canals and communicating with adjacent tubules. The polymerization of adhesive in lateral canals was more prevalent with Scotchbond Multipurpose, C & B Metabond, and etched All-Bond 2 adhesives. The network of interconnected adhesive tags formed with these materials may be fundamental to the development of a stronger dentin/resin bond.

Acid Etching, Dental↗
PubMed1994

Scanning electron microscopy of Eikenella corrodens colony morphology variants.

Eikenella corrodens is a gram-negative, human pathogen which exhibits colony morphology variation. Scanning electron microscopy (SEM) was used to examine large (non-corroding) and small (corroding) colony variants from the type strain (ATCC 23834) and two clinical isolates (strains VA1 and CM1). Large colonies were large, flatter, and appeared relatively featureless compared to small colonies and had even, smooth colony margins. Small colonies were more raised from the medium surface, and often had a central raised region surrounded by flatter border. Cells on the surface of large colonies were more regularly arranged at the colony edge, and end-to-end rows of cells around the colony were seen in some strains. Cells in the center of the upper surface of small colonies were usually randomly arranged. Within cross sections of small colonies, cells were arranged randomly or perpendicular to the medium; in large colonies, cells were random or arranged horizontally. Amorphous, "slime" material was often seen covering groups of cells in large and small variants. An unusual variant, possibly a mutant, which combined features of both colony types was isolated.

Eikenella corrodens↗
PubMed1993

Microbial colonization on natural tooth structure compared with smooth and plasma-sprayed dental implant surfaces.

The purpose of this study was to characterize and compare by scanning electron microscopy (SEM) the maturation of supragingival microbial plaque on enamel and smooth titanium and that of subgingival plaque on cementum, plasma-sprayed titanium and hydroxyapatite surfaces. Specimens (6.5 x 2 x 1 mm) were obtained from titanium implants with smooth transmucosal collars and plasma-sprayed endosseous posts of titanium or hydroxyapatite. Unerupted third molars were sectioned to similar dimensions that included equal lengths of enamel and root surface. Ten patients with post-treatment pocket depths of > 6 mm on 3 non-adjacent teeth were selected and each had 1 set of the 3 specimen types bonded by random assignment to the selected teeth. Specimens were positioned so that enamel and/or smooth titanium surfaces were supragingival and cementum and titanium or hydroxyapatite plasma-sprayed surfaces were subgingival. Patients were instructed to stop oral hygiene, after which 2 specimen sets were removed at 1, 3, 5, 7 and 10 days. Two specimens of each type were examined by SEM at each time interval for supra- and subgingival plaque. The sequence of appearance of various microbial morphotypes in supra- and subgingival plaque was similar regardless of surface. In both supra- and subgingival plaque, depending on time interval, cocci, rods of various lengths, filamentous organisms, fusiforms, spirochetes and corn-cob formations were observed. Mineralized plaque was noted on most subgingival specimens by day 10. These observations indicate that surface of natural teeth, smooth titanium and plasma-sprayed titanium and hydroxyapatite support the maturation of microbial plaque with the successive inclusion of a variety of morphotypes.

Bacteria↗
PubMed1993

Glycosaminoglycans and periodontal disease: analysis of GCF by safranin O.

The purpose of this study was to quantify glycosaminoglycans (GAG) released into the gingival crevicular fluid (GCF) during health, gingivitis, and adult periodontitis. The investigation tested the hypothesis that increased amounts of GAG can be measured in GCF associated with gingivitis and adult periodontitis as compared to health. An individual patient's sampling sites were assigned to either a health (control) group or 1 of 3 experimental groups, gingivitis, periodontal "maintenance" (perio-M), or periodontal "non-maintenance" (perio-NM) according to standard clinical criteria of pocket probing depth, bleeding on probing, and radiographic evidence of bone loss. The perio-M group was defined as a periodontal patient who had received a dental prophylaxis and/or root planning within 6 months prior to GCF collection. The perio-NM group had received no periodontal therapy during the previous 6 months. Subsequent to air-drying and isolation, GCF was collected by a microcapillary pipette held at the gingival margin. All fluid samples were digested overnight at 37 degrees C with 25 micrograms of papain and analyzed for GAG content using a chondroitin-4-sulfate standard. Data generated from safranin "O" dye binding assays of GAG revealed 4.41 +/- 9.82 ng GAG from the health (control) group (n = 23); the gingivitis group (n = 13) showed 15.23 +/- 11.85 ng GAG/sample; perio-M group (n = 11) showed 23.64 +/- 12.98 ng GAG/sample and the perio-NM group (n = 12) exhibited 119.08 +/- 33.14 ng GAG/sample.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Photoelastic stress analysis of natural teeth and three osseointegrated implant designs.

This study used photoelastic stress analysis to compare the location and magnitude of periradicular stresses created by load application directed through two anatomically different natural teeth and three different implant designs. Also studied was the contribution made by the periodontal ligament in the transfer of these stresses. Within the limits of this study, results suggest that the abutment structures with the greatest amount of periodontal support tend to distribute stresses in the most favorable manner. Also, the conical shape of the tooth root, with its large cervical area, has a distinctly positive effect on stress distribution.

Birefringence↗
PubMed1993

The dentinal surface: its influence on dentinal adhesion. Part III.

This final paper in a series of three uses transmission and scanning electron microscopy to compare the category III dentinal adhesive systems--those with shear bond strength values near or exceeding 17 MPa. Contemporary commercial dentinal adhesive systems such as Superbond and Scotchbond Multi-Purpose, chosen for their varied chemical pretreatments, are contrasted; a contemporary commercial system (Prisma Universal Bond 3) with characteristics of category I and II dentinal adhesives is also included for comparison. The shear bond strength values attained with most category III systems are high enough to cause cohesive failure of the dentin during bond strength testing. This result is attributed to a combination of factors that include effective wetting and penetration of the prepared dentinal surface as well as a tendency to leave collagen fibers at the adhesive-dentin interface in an apparently structurally intact state.

Boron Compounds↗
PubMed1993

Gingival response to subgingival placement of monolithic tetracycline-impregnated fibers: microscopic observations.

This study examines and characterizes the soft tissue wall of periodontal pockets after a 10-day in vivo exposure to monolithic tetracycline-impregnated fibers, with and without root planing. Four teeth from each of eight patients were randomly assigned to (1) nontreatment (controls), (2) treatment by root planing only, (3) treatment by tetracycline fiber only, or (4) treatment by scaling and root planing and tetracycline fibers. Ten days after initial therapy, all teeth were extracted with associated soft tissue pocket walls intact. Three specimens were obtained from each tooth for examination by scanning microscopy, energy dispersive spectroscopy, and light microscopy. Results indicated that use of tetracycline-impregnated fibers over a 10-day period did not adversely affect the epithelial lining and had no significant effect on the density or character of the inflammatory response present in adjacent soft tissue and confirmed the antimicrobial effects of the fibers.

Analysis of Variance↗
PubMed1993

Evaluation of site-specific chemotherapeutic agents in periodontal treatment.

The rapid evolution of chemotherapeutic agents and site-specific treatment of adult periodontitis using controlled delivery systems require critical evaluation by the clinician. At present there are no defined guidelines to assist clinicians in their decision-making process. This paper offers background information and guidelines that can be applied to new and established chemotherapeutic agents and site-specific controlled delivery treatment modalities. The guidelines are not intended to be all inclusive or represent a definitive treatise on the subject. However, it is hoped that the factors addressed will serve as impetus for a discriminating consideration of the problems inherent to the evaluation of new therapeutic products, particularly those intended for use as site-specific controlled delivery modalities in the treatment of adult periodontitis.

Anti-Infective Agents, Local↗
PubMed1992

Serum levels of tetracycline during treatment with tetracycline-containing fibers.

Four adult patients with at least 8 teeth that had attachment loss of 5 to 10 mm which bled on probing were included in this study. Polymeric tetracycline (TCN) containing fibers were placed and left in the pockets for a period of 10 days. Plasma samples were collected at baseline, 1 hour, 3 hours, 3 days, and 10 days after fiber placement. The mean length of fiber used averaged 187 cm with a range of 160 to 222 cm. The maximum TCN dose per patient averaged 105 mg with a range of 91 to 126 mg producing no detectable serum level greater than 0.1 micrograms/ml. This level was found in 3 of the 4 subjects at 3 hours after fiber placement and in 1 subject at 3 days after fiber placement. Transient and insignificant levels of TCN became available systemically shortly after the placement of multiple fibers. The dose of TCN in each patient was well tolerated and was not associated with any serious adverse effects.

Adult↗
PubMed1992

Tissue concentration and localization of tetracycline following site-specific tetracycline fiber therapy.

The primary objective of this study was to evaluate the concentration and location of tetracycline hydrochloride in tissue adjacent to periodontal pockets treated with a tetracycline impregnated fiber. A secondary objective was to determine if the presurgical placement of fibers had any adverse effects on healing following periodontal surgery. The study population consisted of 10 patients with at least 2 pockets in both maxillary quadrants of > or = 5 mm in depth and exhibiting bleeding on probing. After an initial scaling and root planing, placebo or tetracycline fibers were randomly assigned by quadrant to 2 non-adjacent pockets. Fibers were removed at the time of surgery; i.e., day 8, and periodontal surgery was performed utilizing a flap incision that allowed biopsy of 1 interdental papilla from each of the 2 test sites in each quadrant. One biopsy was analyzed for tetracycline concentrations by high performance liquid chromatography (HPLC). The second biopsy was examined by both light and ultraviolet fluorescence microscopy to determine the location of residual tetracycline and the intensity of inflammatory cell infiltrates. Results showed that the tissue concentration of the antibiotic in tetracycline treated sites was 64.4 +/- 7.01 ng/mg (ng of tetracycline/mg tissue weight) which corresponds to 43 micrograms of tetracycline and was below levels of accurate measurement in placebo treated sites. Tetracycline tissue concentrations corresponded to the ultraviolet fluorescence microscopy with a Pearson correlation coefficient of r = 0.92. Tetracycline fluorescence was noted in the soft tissue wall ranging from 1 to 20 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Root surface characteristics associated with subgingival placement of monolithic tetracycline-impregnated fibers.

The purpose of this investigation was to inspect and characterize the subgingival root surface after a 10-day exposure in vivo to 25% tetracycline hydrochloride by weight in an ethylene vinyl acetate copolymer fiber matrix with and without root planing therapy. The root surfaces were examined by fluorescent-light microscopy (FLM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Thirty-two teeth were selected for study, 4 from each of 8 patients. The teeth of each patient were randomly assigned to one of four treatment groups: non-treated control (C), scaling and root planing only (RP), tetracycline-impregnated fiber only (F), and scaling and root planing with tetracycline-impregnated fiber application (RP/F). SEM revealed a visible reduction in the subgingival microbial flora in both the F and RP/F treatment groups in comparison with the C group specimens. Many of the residual bacteria observed in F and RP/F specimens appeared non-viable, exhibiting obvious loss of membrane integrity. In contrast, the RP specimens exhibited randomly distributed areas of residual subgingival plaque and calculus with newly developing plaque fronts; the plaque fronts undoubtedly having formed during the 10 days post-therapy. All RP/F specimens exhibited an incomplete removal of adsorbed root surface pellicle and demineralization of the subsequently exposed root surface. EDS analysis of large crystals adhering to root surfaces of F and RP/F specimens revealed high chloride peaks, suggesting the presence of residual tetracycline. FLM examination of F and RP/F treated specimens showed a superficial penetration of tetracycline into the root surface of about 10 microns. Areas of demineralized root showed slight tetracycline penetration into exposed dentinal tubules.

Adsorption↗
PubMed1992

The effects of the Nd:YAG laser on in vitro fibroblast attachment to endotoxin-treated root surfaces.

The purpose of this study was to evaluate the effects of the Nd:YAG laser on in vitro fibroblast attachment to endotoxin-treated root surfaces and to describe any laser-induced cementum surface alterations. Thirty 4 mm x 4 mm cementum segments were obtained from unerupted third molars. The treatment groups were as follows: 1) control, healthy root segment; 2) non-lased, endotoxin treated; and 3) lased, endotoxin treated. The endotoxin treated roots were soaked in E. coli 055:B5 lipopolysaccharide (556 EU/ml) for 72 hours. The lased, endotoxin-treated root segments were treated with a Nd:YAG laser using a 320 microns contact optic fiber handpiece with an energy setting of 80 mJ at 10 pulses per second for one minute. The root segments were subsequently placed in fibroblast culture dishes for 40 hours and then prepared for scanning electron microscopy (SEM) observation. SEM examination revealed two different types of attachment: flat and round. Flat cells represented firmly attached cells due to well-defined points of attachment and numerous lamellapodia. Round cells possessed few attachment processes and were, therefore, considered poorly attached. The lased, endotoxin-treated root segments had significantly decreased numbers of flat fibroblasts versus the control and non-lased, endotoxin-treated root segments. The absence of flat fibroblasts in the laser treated root segments was a consistent finding. The non-lased, endotoxin-treated root segments had significantly increased numbers of round fibroblasts versus the control and lased, endotoxin treated groups. The lased root segments exhibited surface alterations which included charring, crater formation, cementum meltdown, and tracking.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum Silicates↗
PubMed1992

Chemical characterization of lased root surfaces using Fourier transform infrared photoacoustic spectroscopy.

Recently lasers have been recommended as an alternative or adjunctive therapy in the control and treatment of periodontally diseased root surfaces. The purpose of this in vitro investigation was to characterize the chemical structure of lased root surfaces using Fourier transform infrared photoacoustic spectroscopy (FTIR/PAS). Cementum samples, 6 mm x 2 mm, were cut from the root surface of extracted non-carious, unerupted human molars. The experimental samples were lased with a Nd:YAG laser at an average energy of 80 mJ at 10 pulses per second. Total lasing time ranged from 1 minute 45 seconds to 4 minutes. A non-lased cementum sample served as the control. All spectra were recorded from 4000 to 400 cm-1 using the photoacoustic cell attachment on an Analect RFX-65 FTIR Spectrometer. Photoacoustic FTIR spectra of lased cementum samples showed a decrease in the protein/mineral ratio in comparison to the control. Breakdown of protein at the root surface potentially contributed to an ammonium band at 2010 cm-1. The decreased protein/mineral ratio and the potential surface contamination with protein by-products, may ultimately affect cell reattachment at the cementum surface.

Acoustics↗
PubMed1992

The effect of Nd:YAG laser exposure on root surfaces when used as an adjunct to root planing: an in vitro study.

The purpose of this study was to evaluate the effects of Nd:YAG laser treatment on root surfaces in vitro when used alone or in combination with conventional scaling and root planing. The study population consisted of 18 unerupted third molars, each with a 3 mm diameter treatment site outlined on the root surface. Three specimens were randomly assigned to each of 6 different treatment groups: 1) untreated control; 2) root planed only; 3) laser treated only using 1.25 W of energy; 4) laser treated only using 1.50 W of energy; 5) laser treated with 1.25 W of energy followed by root planing; and 6) laser treated with 1.50 W of energy followed by root planing. Following their respective treatment, all specimens were prepared for evaluation by scanning electron microscopy. Specimens from Group 2, root planed only, exhibited a smear layer of scale-like texture with parallel instrument tracks resulting from curet use. Specimens treated by laser only, Groups 3 and 4, featured various surface changes not observed in controls such as charring and carbonization of the cementum surface, randomly distributed pitting and crater formation, and melting of the root mineral phase with subsequent resolidification as porous globules. Those specimens treated by laser followed by root planing, Groups 5 and 6, exhibited surface characteristics similar to those noted in Group 2 specimens. Further, there were areas of exposed dentinal tubules resulting from a "peeling" of the cementum layer. The results of this in vitro study suggest that laser use during root preparation, even at relatively low energy levels, will result in physical changes to the root surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum Silicates↗
PubMed1992

A preliminary study on the effects of the Nd:YAG laser on root surfaces and subgingival microflora in vivo.

The purpose of this study was to examine the effects of root preparation using the pulsed Nd:YAG laser, either alone or in combination with manual instrumentation. Study specimens consisting of 18 teeth with associated periodontal pockets from 8 different patients were treated as follows: 5 specimens were root planed with curets followed by laser exposure for 3 minutes using energy settings of 3.0 W at 20 pps; 2 specimens were root planed and then laser treated for 3 minutes using settings of 2.25 W and 20 pps; 4 specimens were treated by laser for 1 minute at settings of 1.75 W and 20 pps followed by root planing; 4 specimens were treated by laser only for 1 minute using settings of 1.75 W and 20 pps; and the remaining 3 teeth served as untreated controls. Both prior to and after completion of the laser and root planing treatments, microbiological samples were obtained from the treated pockets and submitted to a commercial laboratory for analysis of levels of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia. With the exception of two 7-day specimens, all others were extracted immediately post-therapy and processed for SEM examination. All treated specimens, regardless of treatment sequence, exhibited some degree of laser-induced root surface alteration. Notably, laser-treated calculus deposits were free of their characteristic surface layer of microbial plaque. Microbial sampling indicated a post-therapy reduction in levels of all 3 putative microbial pathogens compared to pre-treatment samples and control specimens. However, SEM examination revealed residual deposits of plaque and calculus in all treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗