Silicone Rubber Impression Research Articles

Wear and microwear on the teeth of a moose (Alces alces) population in Manitoba, Canada

A group of wild moose from Manitoba, Canada, were documented as having excessive tooth wear. Replicas of one incisor tooth were collected from 16 individuals and from 19 controls for comparison by volumetric and scanning electron microscopic analysis. All animals were aged from tooth cementum lines. Tooth replicas were cast from silicone rubber impressions in epoxy resin and sputter coated with gold. Tooth wear with age was compared statistically by measuring crown height, percent tooth loss, interfacet distance, and facet area on the incisors. The unique pattern of wear on the anterior teeth of affected moose was described. In affected animals, crown heights were significantly reduced and percent tooth loss was excessive. Microwear analysis found that an abrasive agent, acting predominantly in a lingual to labial direction, had been responsible for loss of enamel and dentine incisally and interproximally, and on the facial and lingual surfaces to a lesser extent. Interdental facets became involved by vertical abrasion. Control teeth showed fewer but coarser scratches and only approached the pattern of wear found in affected moose in a few individuals in old age. The loss of tooth structure would lead to diminished cropping efficiency and damage to the periodontium.

印象材および合着材の根管内送入用器具 Ｓｃｒｅｗ Ｂｕｒの開発とその有用性に関する実験的研究

Impression materials or cement should be delivered smoothly into the prepared root canals. A spiral instrument, made for endodontic treatment, has been traditionally used for this purpose.This report deals with the efficiency of this conventional instrument in comparison with the “Screw Bur” which we have developed for prosthodontic procedures. A translucent acrylic model was used so that the materials in the canal could be directly observed. The movement of the materials-polysulfide rubber and silicone rubber impression materials and zinphosphate cement-was taken on 8 mm film for analysis.The results may be summarized as follows:1. Impression material and cement were delivered into the canal more rapidly when the diameter of the spiral instrument was bigger.2. It took longer than expected to fill the canal with materials using the conventional instrument. It was too thin for prosthodontic use.3. High velocity rotation of the instrument delivered materials more efficiently into the canal.4. The new instrument “Screw Bur”, with a thicker diameter of 0.9mm, shortened delivery time required by the conventional instrument by 1/5 to 1/7.5. Clinical trial use has confirmed that “Screw Bur” is effective, safe and reliable for taking impressions and when setting post crowns or cast cores onto teeth.

Pitting and bubbling artefacts in surface replicas made with silicone elastomers.

Pitting or bubbling on the surface of epoxy resin replicas is a frequently encountered artefact associated with the use of silicone rubber impression materials. Several variants of this type of artefact are illustrated. It is suggested that bubbles or pits form at the mould:epoxy interface during curing of the epoxy, and that they are caused by gas escaping from the mould material itself. Duration of silicone rubber polymerization, base-catalyst ratios, and surface porosity of the object may all influence the occurrence of mould degassing.

Scanning electron microscopy of endothelium around an experimental stenosis in the rabbit aorta using a new casting material

Four New Zealand White rabbits had bands fitted to their thoracic aorta causing a 73 ± 2 (SD) % reduction in cross-sectional area. The resulting stenosis produced a slight pressure drop and a post-stenotic dilatation that was evident at the time of preparation for microscopy 47 ± 2 days after fitting the band. Four other rabbits served as unoperated controls In all animals a portion of the thoracic aorta was glutaraldehyde-fixed and the lumenal surface cast by injecting a silicone rubber impression material. Casts were photographed and measured before being viewed under the scanning electron microscope. Micrographs were taken from predetermined areas and nuclear numerical density measured. No significant dorso-ventral differences in nuclear numerical density appeared in any aorta and no significant differences existed between sites in the 4-cm region of thoracic aorta sampled from control animals. Endothelial cells upstream to stenoses appeared identical to those from control arteries, although there was a greater incidence of spindle cells and cellular adherence than elsewhere. Nuclear density here was significantly higher than in control arteries but not different to any other region in the stenosed aorta. However, cells from within the stenosis and from just downstream were noticeably altered. Within the stenosis the cast reproduced longitudinal folds and the cells were strictly oriented with the long axis of the vessel. Nuclear density here was higher than any other region except just distal to the stenosis where there was a marked loss of normal longitudinal orientation and a change in the shape of some cells from elongated to polygonal. Swirling patterns and other zones of disorientation were evident up to 2 diameters distal to the stenosis, while within 2–4 diameters distal the cells appeared somewhat rounder and less strictly oriented than in control vessels. Beyond 4 diameters downstream, the cells appeared identical with those of control arteries and were of the same density as in mid-dilatation or in controls. These observations relate to expected local flow patterns, and are relevant to the role of haemodynamic factors in atherosclerosis.

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The Silicone Rubber Impression Material Vulcanized by Addition Reaction on Several Physical Properties

The Silicone Rubber Impression Material Vulcanized by Addition Reaction on Several Physical Properties

Studies on Characters of Various Impression Materials by means of Holography

The present study is desined to Silicone Rubber Impression materials on manipulated condition, that is impression thickness, making and remove of impression its time elapse of mixing, have influence on occulusal surface and axial surface used with Holography.As the results of these effort, the following conclusions were obtained.1. This study is good method used with the Holography. This method can measured deformation and infinitesimal displacement of dental materials, don't touch the object and that can observe with the bodily eye.2. Silicone Rubber Impression materials showed various displacement volume severally on manipulated conditions.3. Impression surface of axial surface condition that impression thickness 1, 0mm, making of impression after 75 seconds, removed after 5 minutes its time elapse of mixing showed minimum. And the state added between occulusal surface and axial surface, that condition showed minimum displacement volume too.4. Silicone Rubber Impression materials surface keep on after 60 minutes displacement all condition that this study established.

Addition curing silicone rubber impression materials. An appraisal of their physical properties

Addition curing silicone rubber impression materials. An appraisal of their physical properties

Stomatal Behaviour of Tea (Camellia sinensis) in Relation to Environment

SUMMARY (1) Observations were made of the stomatal behaviour of tea growing in Malawi. Measurements of stomatal conductance made with an automatic diffusion porometer were consistent with measurements of stomatal aperture made with silicone rubber impressions. (2) Except for the 2- to 3-month annual dry season, stomatal conductance was principally determined by incident irradiahce; it was independent of shoot water potential, vapour pressure deficit and the rate of photosynthesis. Within the dry season, conductance remained unaffected by shoot water potential and vapour pressure deficit but became more closely related to the rate of photosynthesis. (3,) It is suggested that a factor, associated with climatic change at the beginning and end of the dry season, alters the sensitivity of the stomata towards one or other of the two principle mechanisms by which they respond to light. (4) Two anomalous forms of stomatal behaviour were observed: a transient opening in the middle of the day and a temporary closure in the middle of the morning. (5) The different diurnal patterns in the wet and dry seasons, and the anomalous stomatal movements, illustrate the diversity of stomatal response which can occur in a woody perennial species.

A surface impression and scanning electron microscopic study of porokeratosis of Mibelli

A silicone rubber impression technique, together with scanning electron microscopy, was used to study the surface detail of porokeratosis of Mibelli. The lesions are propagated by a bud-like spreading of the active edge. The keratotic rim is produced by the condensation of squamous cells from both within and without the lesion.

Stomatal Behavior of Wheat Cultivars in Relation to Their Transpiration, Photosynthesis, and Yield1

AbstractWheat cultivars were found to differ widely in their stomatal aperture under conditions of adequate moisture supply. A field study was carried out to determine whether these differences were related to short‐term transpiration (measured by a hygrosensor cuvette over periods of less then 1 min), short‐term photosynthesis (measured by the uptake of 14CO2 over a period of 20 sec), long‐term water consumption (determined from soil moisture data over periods of several weeks), and grain yield. Rank correlations between the various attributes were determined. Ten wheat cultivars were used in 1 year, 11 cultivars in the other year. Leaf permeability (measured by means of a viscous‐flow porometer) was well correlated to stomatal aperture (measured by means of silicone rubber impressions), and was therefore used as an index of stomatal aperture. Leaf permeability was significantly rank‐correlated with short‐term transpiration (r = 0.97 to 0.98), with short‐term photosynthesis (r = 0.86 to 0.84) and with grain yield (r = 0.70 to 0.74), but not with water consumption (r = 0.01 to 0.22), which was nearly the same for all cultivars. Yields of the cultivars ranged between 4,000 and 5,200 kg ha−1 in the first year, and between 4,250 and 6,150 kg ha−1 in the second year. It is suggested that wheat cultivars having wider somatal aperture produce higher yields without consuming more water, and that the porometer method may be employed in wheat breeding programs.

A Study on Setting Process of Silicone Rubber Impression Materials

A Study on Setting Process of Silicone Rubber Impression Materials

Studies on Characters of Various Impression Materials by means of Holography

The present study is desined to Silicone Rubber Impression materials on manipulated condition, that is impression thickness, making and remove of impression its time elapse of mixing, have influence on occulusal surface and axial surface used with Holography.As the results of these effort, the following conclusions were obtained.1. This study is good method used with the Holography. This method can measured deformation and infinitesimal displacement of dental materials, don't touch the object and that can observe with the bodily eye.2. Silicone Rubber Impression materials showed various displacement volume severally on manipulated conditions.3. Impression surface of axial surface condition that impression thickness 1, 0mm, making of impression after 75 seconds, removed after 5 minutes its time elapse of mixing showed minimum. And the state added between occulusal surface and axial surface, that condition showed minimum displacement volume too.4. Silicone Rubber Impression materials surface keep on after 60 minutes displacement all condition that this study established.

Silicone rubber stent. An improved form of ear packing.

Silicone rubber impression material was adapted as a postoperative otologic stent. This material fulfilled all criteria for the ideal ear packing; in addition, it offered the benefit of ease of application and less tissue reactivity during the initial healing phase.

Scanning electron microscope investigation of cracks in teeth through replication

A reliable and accurate technique is described for the in vivo and in vitro replication of teeth to be studied by scanning electron microscopy. The use of a silicone rubber impression material and low viscosity casting epoxy resin in replica fabrication provides a reliable method for in vitro and in vivo investigation of cracks in teeth. Cracks in the tooth enamel contribute to structural degradation. Observation in this study of the size and apparent sealing of these cracks in vivo may explain why little if any evidence exists on the contribution of the cracks to caries formation.

Fabrication of temporary crowns and fixed partial dentures

The methods of temporary crown or bridge fabrication described in this article have some distinct advantages over the use of preformed temporary prostheses. 1. Tooth form and position can more closely duplicate the patient's natural teeth. This is very important esthetically in the anterior portion of the mouth. 2. Tooth form can be more closely duplicated for posterior teeth. This allows stabilization of the prepared teeth in anteroposterior as well as occlusal relationships during fabrication of the permanent appliance. 3. Alginate, silicone, and thiokol rubber impression materials can be used, but they are either more inaccurate, costly, or time-consuming to use. It is difficult to remove the temporary protection from some of these impressions without danger of breakage. It is difficult to fabricate the appliance to the correct occlusal relationship when the patient cannot close his teeth into centric occlusion.

Minimum acceptable laboratory procedures for satisfactory fixed partial dentures

Diagnostic casts should be made of hydrocal stone poured into the impressions. Dies may be copper-plated (if the impressions are in compound), or they may be made of improved stone, or silver-plated (if the impressions are made of an elastic material) or they may be made of silver amalgam or epoxy resin. Working casts should be made of hydrocal stone after the dies are properly placed, if full plaster impressions have been supplied. When castings are placed in the impression, they are treated to permit the use of low-fusing metal in them and hydrocal stone is poured in the remainder of the impression to form the cast. Impressions made in elastic materials may be silver-plated or hydrocal stone can be poured directly into them. The cast of the opposing arch may be poured in stone, or a combination of low-fusing metal can be used in the imprints of the teeth, and the remainder of the cast can be made of hydrocal stone. Casts should be poured immediately after impressions made in alginate (irreversible colloid) and agar (reversible hydrocolloid) in]pression materials are removed from the mouth. Thiokol and silicone rubber impressions should have casts poured in them within two hours after removal from the mouth. Casts made of hydrocal stone should be placed in a humidor until the set is complete (see manufacturer’s directions).

A NOTE ON THE MEASUREMENT OF STOMATAL APERTURE

SummaryCellulose acetate replicas were made from silicone rubber impressions of the abaxial surfaces of perennial ryegrass leaves. Apertures between 1 μ and 4 μ (mean 2 μ) were measured in replicas from leaves which had been exposed to conditions expected to close the stomata. This discrepancy is explained by observations of the ventral walls of guard cells in transverse sections of stomata, and by Araldite impressions of the cut ends of ryegrass leaves. These show that when a stoma is closed the ventral walls make contact below the paradermal walls of the guard cells and consequently a small depression is left between the cells. These depressions are similar in width to the apparent apertures in the cellulose replicas which may be wrongly interpreted as slightly open stomata. In some species the silicone impression method is incapable of giving an accurate measurement of stomatal aperture. Consequently, in attempts to relate such measurements to stomatal function or rate of transpiration it should be established that small apertures shown in cellulose acetate replicas are not the result of depressions between the external surfaces of guard cells in closed stomata.

Stomate Density and its Relationship to Water‐Use Efficiency of Blue Panicgrass (Panicum antidotale Retz.)1

Six clones of blue panicgrass (Panicum antidotale Retz.) representing three diverse sources of germ plasm were used to evaluate the association between stomate density and water‐use efficiency. Silicone rubber impressions were taken on the abaxial and adaxial leaf surfaces of four plants from each clone. Leaves were selected from the top, middle, and base of the culm and impressions were taken at the base, middle, and tip of each leaf.Stomate density of blue panicgrass clones ranged from 78 to 165 per mm2. Leaves adjacent to the inflorescence had significantly lower stomate density than those at the middle and base of the culm. No difference was found among stomate densities at the three positions on a leaf.A nonsignificant association was obtained when wateruse efficiency and stomate density were correlated for the six clones. Drouth tolerant clones had fewer stomates per unit area than drouth susceptible clones.

Parallel-pin splints for periodontally involved teeth

A simplified technique for the construction of parallel-pin splints has been described. A matrix with metal guides is used to insure parallelism of tooth preparations. Patterns for the castings are made on investment casts poured into mercaptan or silicone rubber impressions. The finished castings are cemented permanently into the mouth with oxyphosphate of zinc cement.