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Results for “scanning electron microscope”

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At least 973 records · Page 54Linked to original sources

PubMed1996

Scanning electron microscopic evaluation of resin-dentin and calcium hydroxide-dentin interface with resin composite restorations.

Calcium hydroxide has been used as a liner in resin composite restorations to protect the pulp. Recent research has demonstrated that pulpal inflammation is caused by microleakage of restorations and by the subsequent passage of bacteria. The present study involved scanning electron microscopic observation of cross-sections of resin composite-dentin interfaces after the interposition of a layer of calcium hydroxide. A new-generation adhesive system that involves etching of the dentin was used. Ultrastructural analysis indicated that polymerization shrinkage of the resin composite caused the separation of the calcium hydroxide from the dentinal surface, forming 8- to 15-micron-wide interfacial gaps in 100% of the areas studied. Where the adhesive was applied directly to dentin, it adhered closely, forming a gap-free attachment with evidence of an acid-resistant hybrid layer (4 to 6 microns in thickness) and resin tags of various lengths that hermetically sealed the dentinal tubules.

Acid Etching, Dental↗

PubMed1990

Scanning electron microscope observation of canal cleanliness.

The aim of this study was to evaluate the cleansing efficiency of three root canal preparation techniques. The distal root canals of mandibular molars, divided into three groups of four teeth each, were prepared according to the following techniques: manual (serial), ultrasonic (Cavi-Endo), and automated (Canal Finder). The canal wall surfaces were examined under a scanning electron microscope at three levels. No preparation technique was found to result in any characteristic microscopic features that distinguished it from the other techniques. The lack of such differences makes it impossible to establish objective criteria for comparing these techniques in terms of root canal cleanliness. It was established that even canals that appeared to be clean included areas coated with smear layer and having uninstrumented areas and even pulpal tissue debris.

Dentin↗

PubMed1989

Ultrastructural comparisons of ceramic and titanium dental implants in vivo: a scanning electron microscopic study.

Identically prepared, screw-type ceramic and titanium endosteal dental implants were inserted in the jaws of adult mongrel dogs for periods of up to 6 months. Sixteen of the 32 total implants supported fixed bridgework. The interface of bone and soft connective tissues with the dental implants was examined by routine and innovative scanning electron microscopic (SEM) techniques using both secondary and backscattered electron imaging. Results demonstrated excellent bone adaptation to both titanium and ceramic implants. Direct adaptation of bone to the upper third of both type implants was observed with only minimal amounts of any intervening fibrous connective tissue. A composite of trabecular bone and fibrous connective tissue was observed in the lower two-thirds of the implants examined. Areas of bone alteration suggestive of osteoid were observed at the thread apicis of some loaded implants. From this investigation we concluded that similar longitudinal tissue responses were generated to one-piece, cylindrical screw-type titanium and alpha alumina oxide ceramic dental implants. Possible bone remodeling was observed at the thread apicis of the loaded implants, an area where occlusal forces may be distributed. We further suggest that one-stage endosteal implants are capable of maintaining a proportional bone-to-implant interface at the apical support region, similar to that suggested to two-stage implant systems.

Animals↗

PubMed1994

The Provox voice prosthesis and Candida albicans growth: a preliminary report of clinical, mycological and scanning electron microscopic assessment.

Provox voice prostheses are low-resistance speech values available since 1990 for post-laryngectomy voice rehabilitation. Candida spp. mycelial growth has always been a major problem in all prosthetic valves causing leakage and limiting valve life. We found that the Provox new valves were not exempt from the old problem. We performed a preliminary clinical, mycological and scanning electron microscopic assessment of Candida spp. growth on these valves. In contrast to studies done with other valves we found that the Candida mycelium on these new valves was a surface colony rather than growing into the valve substance, thus it might be feasible to control the mycelial growth by either mechanical cleansing or by using topical anti-fungal agents.

Candida albicans↗

PubMed1989

Scanning electron microscope evaluation of wear of stainless steel and high carbon steel curettes.

Root planing depends on quality instrument cutting edges. The sharpness and wear of stainless steel (SS) and high carbon steel (HCS) dental curettes were compared before and after standardized root planing procedures. Forty working edges of dental curettes, 20 of each alloy, were examined by scanning electron microscope (SEM) prior to any root planing (control), after 15 strokes, and after 45 strokes. Root planing was carried out on freshly extracted, single-rooted teeth, mounted in natural positions in mannikin jaws. Working areas measuring 3 x 5 mm were marked on root surfaces previously exposed by periodontitis. Each working edge was examined at points 1 mm and 2 mm from the tip under the same magnification (x 240). Microscopic observations showed that edge deformation increased from the control (factory sharpened) group, to the "15 stroke" group, and from the "15" to the "45 stroke" group, in both SS and HCS curettes. SS curettes, however, demonstrated significantly more wear than HCS curettes. After 45 strokes, only 5% of the SS curettes were sharp, compared to 20% of the HCS curettes. While 65% of the SS curettes showed severe edge deformation by the end of the study, only 20% of the HCS curettes were severely deformed (P less than 0.01). The results indicate that HCS curettes are more resistant to wear than SS curettes. Further study is indicated to evaluate the relationship between actual bevel dimensions and root planing effectiveness.

Alloys↗

PubMed2001

Scanning electron microscopic description of cellular activity and mineral changes in feline odontoclastic resorptive lesions.

The cellular activity and changes in mineral composition of dental tissues involved in feline odontoclastic resorptive lesions were investigated. Teeth with at least 1 lesion (n = 10) were extracted from 10 different cats that were presented primarily for chronic gingivostomatitis and/or severe periodontal disease. Scanning electron microscopic methods were used to determine the presence of resorptive cells in 8 teeth while 2 teeth were evaluated for pathologic changes in dental mineral composition. Observations were complicated by the presence of organic wear on the dental surfaces, however resorptive cells could be clearly identified in feline odontoclastic resorptive lesions. Resorptive cells had morphologic features indicative of "osteoclast-like" cells or odontoclasts. Resorptive cell activity created a resorption area of darker dentin continuous with physiologic dentin. The darker dentin area seemed poorly mineralized and showed a significantly lower calcium/phosphorous ratio compared with adjacent physiologic denting in 1 tooth. A significantly higher level of magnesium combined with available carbonate ions may have increased the solubility in areas of darker dentin.

Animals↗

PubMed2004

A scanning electron microscope study of plaque accumulation on silk and PVDF suture materials in oral mucosa.

AIM: To examine plaque accumulation on silk and polyvinylidene fluoride (PVDF) sutures at different time intervals. METHODOLOGY: Twenty-one male albino rabbits received sutures under general and local anaesthesia. After 3, 5 and 7 days sutures were removed and processed for scanning electron microscope (SEM) observation. The Friedman and the Wilcoxon tests were used to compare contamination on PVDF and silk suture materials at different time intervals. RESULTS: At all time intervals, the whole surface of silk sutures was covered with a thick layer of bacterial plaque and debris. Microorganisms and blood cells on the surface and between the filaments of the silk suture material were observed. Light debris appeared around the knot area of PVDF sutures after 3 days. At 5 and 7 days, contamination could be seen in scattered areas along the suture material. The average contaminated area was smaller on PVDF suture materials, which were removed at 5 than at 7 days after insertion. At 3 days, PVDF sutures showed significantly less contamination than at 5 and 7 days (P = 0.002). There were statistically significant differences between silk and PVDF sutures at 3, 5 and 7 days. CONCLUSION: SEM observation showed that PVDF sutures were contaminated less than silk sutures at 3, 5 and 7 days.

Animals↗

PubMed1988

New type of end-to-side anastomosis for small arteries: a technical and scanning electron microscopic study in rats.

A new type of end-to-side anastomosis between small arteries is described. The anastomosis is made for three-quarters of its circumference with a nonoccluded recipient artery. The recipient artery must be occluded for only 3 to 5 minutes to complete the anastomosis. The anastomosis site was studied with the scanning electron microscope at different times (1 hour to 3 months) after the operation in 20 rats. In every case, the anastomosis was widely patent and a gradual endothelialization of the anastomosis site was observed. After 7 to 10 days, the endothelialization was more or less complete and, during the following weeks, a further smoothing of the ridge protruding into the anastomosis was noted. As an addendum, the authors describe an improvement of this technique that was developed after the sapphire tip of the neodymium: YAG laser became available. Now the anastomosis is fully completed and the connection between the two vessels is made by the laser tip introduced via a side branch of the donor vessel. The recipient artery need not be occluded at all. The results are promising.

Anastomosis, Surgical↗

PubMed1985

The carotid siphon: a scanning electron microscope assessment of its embolic potential.

The role of the carotid siphon as a source of embolic material has had limited morphological or clinical study. The morphologic data available suggests that the siphon plays only a small role in embolic cerebrovascular disease. Clinical studies, however, suggest that it has a significant ischemic potential. To clarify this apparent discrepancy, we have designed a scanning electron microscope study of the carotid siphon. Eighty percent of the specimens from the carotid bifurcation and 30% of the siphon specimens showed evidence of damaged endothelium with attached red cell and platelet debris. The embolic potential of the siphon is estimated to be between 1/3 to 1/2 that of the carotid bifurcation. This supports the most recent clinical studies.

Arteriosclerosis↗

PubMed1995

[Scanning electron microscopic study of the development of crystalline lens fiber].

To elucidate the 3-dimensional structural development of the albino rabbit lens fiber, and to study how cataracts affect these fibers, the lenses from rabbits 1, 2, 4, and 8 weeks old, and from 8 week old rabbits with cataracts caused by naphthalene were examined with a scanning electron microscope. The results were: 1) Normal rabbit: The ratio of the length of the anterior suture line to the diameter of the lens gradually rose from 1 to 4 weeks and then reached a plateau. The ratio of the length of the posterior suture line was constant from the first week on. Fibers were wider in lenses from older rabbits, except for those in the middle of the suture line. Ball-and-socket junctions were common on the anterior side and were concentrated in the area of the paraanterior suture line of lenses from older animals. The lateral large processes were only noted near the anterior suture line, and in extended direction from its end. The likelihood of finding edge processes, especially in the area of middle anterior and posterior sections, rose with age. 2) Rabbit exposed to Naphthalene: The rate of increase of the length of the anterior suture line and the diameter of the lens were both low, but their ratio did not differ from that of a normal rabbit's lens. On the contrary, the growth rate of the posterior suture line was much greater than that of the diameter. The peculiarity of distribution of edge processes and width found in normal lens fibers was not found in naphthalene-affected fibers.

Animals↗

PubMed1983

The localization of histochemical and autoradiographic products in the scanning electron microscope by means of atomic number contrast.

The role of atomic number contrast and backscattered imaging in the localization of histochemical products and reagents is reviewed. Particular attention is given to the localization of enzymatically released products. A backscattered imaging method is presented which permits the simultaneous demonstration of two label elements in a cryosection examined in the scanning electron microscope. An azo-dye method for the localization of acid phosphatase is combined with an autoradiographic technique for demonstrating [3H]thymidine incorporation. Atomic number contrast, produced by backscattered electrons, permits the detection of a bromine-labelled azo dye, denoting sites of acid phosphatase activity within a cryosection and the simultaneous display of the sites of the silver deposited in an overlying photographic emulsion. The former reveals acid phosphatase to be predominantly associated with thymocyte death and macrophage activity in mouse thymus. The latter pin-points the thymocytes as the main sites of [3H]thymidine incorporation. Atomic number contrast has a useful potential for differentiating between spatially separated histochemical products of differing atomic number in a structural context and also allows a flexible degree of subsurface localization.

Animals↗

PubMed1995

[Scanning electron microscopic study of the sensory hairs of the organ of Corti using transtympanic infusion of fluids with different osmotic pressure].

Morphological examination of the sensory hairs of the lower half of the 2nd turn of the organ of Corti of the guinea pig after transtympanic infusion of the aseptic fluids with different osmotic pressure was performed using a scanning electron microscope. Group A fluids (0-315 mosmol/l) did not have any injurious effect on the sensory hairs of the OHCs (outer hair cells) or IHCs (inner hair cells). In contrast, Group B fluids (720, 743 mosmol/l) appeared to cause disarrangement of the stereocilia of the OHCs. Alterations were found to be more extensive and severe in the 3rd row of OHCs. Group C fluids (1224, 1248 mosmol/l) induced total loss of sensory hairs in the 3rd and 2nd row of OHC. The remaining stereocilia in the 1st and 2nd rows showed coalescence of adjacent stereocilia. Based on these findings, the authors concluded that there is a close relationship between osmotic induction/deduction by transtympanic infusion of fluids and high osmotic pressure on the hairs of the organ of Corti.

Animals↗

PubMed1986

[Spontaneous transection of a Raimondi peritoneal catheter--a case report with scanning electron microscopic study of the transected tube].

Spontaneous transection of Raimondi peritoneal catheter is reported. A 6-month-old boy with communicating hydrocephalus had ventriculoperitoneal shunt surgery using Raimondi peritoneal catheter. Six months later, Raimondi catheter was found to be spontaneously transected in a peritoneal cavity. At the age of 5 year-old, the originally installed Raimondi catheter was again transected on the portion of chest wall. Scanning electron microscopic examination of the broken end of spring wire suggested that transection was caused by repetitive exertion of external forces. Mechanisms of transection of this catheter was discussed with review of the literature.

Cerebrospinal Fluid Shunts↗

PubMed1987

[Changes in the surface and cytoskeletal apparatus of the endotheliocytes of the rat aorta during division (based on scanning electron microscopic data)].

Endothelium of the abdominal aorta of 32 KWR-line rats was exposed to freeze injury. En face preparations were made to look for endothelial cells (EC) on different stages of mitosis. Specimens were dried by critical point technique, and the grid was placed on their surface. Then specimens were investigated in succession with light and scanning electron microscopes. The cytoskeleton of EC was investigated on detergent-extracting preparations. It is shown that the end of phase S of the cell cycle and the beginning of prophase are characterized with the lifting of the nuclear-containing zone. Fine microvilli appear on the EC surface during prophase. The cytoskeleton becomes more structured and polarized. During metaphase, EC becomes spherical, its microvilli are shortened. Fine cytoplasmic shoots are seen to extend from the cell poles to the substratum. The density of the fibrillar structures swiftly rise. During anaphase the EC surface is covered with blebs. During late telophase the surface of dividing EC becomes flatter. Their nuclei are connected with rare bundles of fibrillar structures. Mechanisms of EC surface changes during mitosis and the role of cytoskeletal elements are discussed.

Animals↗

PubMed1967

Tribolium castaneum: morphology of "aureate" revealed by the scanning electron microscope.

Counts of setae in "aureate" (au), spontaneous autosomal recessive mutation of good penetrance and viability, show that the au gene causes a three-fold increase in setation over the normal in the visible abdominal sternites but not in the membranous wings of the tenebrionid flour beetle Tribolium castaneum. Micrographs taken with the scanning electron microscope demonstrate that the au gene increases setation throughout the body.

Animals↗

PubMed1985

Effects of antifertility estrogens and progestins on the endometrial surface of early pregnant rats. A scanning electron microscopic study.

Two estrogens, mestranol and 3-methoxy-14 beta, 15 beta-methyleneestra-1,3,5(10)triene-17 beta-ol (STS 593), and two progestins, levonorgestrel and 17 alpha-cyanomethyl-17 beta-hydroxyestra-4,9(10)-diene-3-one (STS 557), all having antifertility properties in rodents, were examined for their effects on the uterine luminal surface of early pregnant rats. Scanning electron microscopic studies showed that there are clear qualitative differences between the effects of estrogens and progestins on both morphology and microvillous pattern of the endometrial surface while STS 557 showed intermediate effects. The results are discussed with respect to the anti-implantation activity of steroids.

Animals↗

PubMed1993

[Variations of the stereociliary bundles of the outer hair cells in guinea pigs. A scanning electron microscopic study].

Variations of the stereociliary bundles of the outer hair cells in guinea pigs observed under scanning electron-microscope were reported. Changes including transposition and distorted outlines of the stereociliary bundles were distributed in all turns of the cochlear duct and all rows of the outer hair cells, but not in inner hair cells. The possible pathogenetic significance of the changes was discussed.

Animals↗

PubMed1992

A scanning electron microscopic study of arterial endothelial repair under turbulent flow conditions.

In order to study the role of hemodynamic factors on the healing and native morphology of endothelium in vivo, turbulent arterial flow was created using a loop bypass model, with and without occlusion in the recipient vessel. In this model, several different patterns of turbulent arterial blood flow resulted. The scanning electron microscope (SEM) was used to evaluate endothelial morphology in the area of the anastomoses at 3 and 14 days post-operatively. Morphological changes in the native endothelium along the recipient vessel correlated well with the direction of blood flow and predicted patterns of turbulence. The morphology of the native endothelium was altered to reflect the direction and pattern (laminar versus turbulent) of blood flow by 3 days postoperatively. Based on endothelial morphology, very narrow zones of separation could be demonstrated between areas of laminar and turbulent blood flow. The degree of reendothelialization across the suture itself was greatly variable at 3 days and there seemed to be no relationship to the location of turbulent flow.

Anastomosis, Surgical↗