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PubMedDate not supplied

Load fatigue of teeth restored with cast posts and cores and complete crowns.

Twenty-five extracted human central incisors were divided into five groups and prepared for complete cast crowns. Test teeth had cast dowel cores fabricated with the ferrule height varying from 0.5 to 2.0 mm in 0.5-mm increments. The five control teeth did not have cast dowel cores. A 4.0-kg load was applied to each of the restored teeth at an angle of 135 degrees to the long axis of each tooth. This load was applied cyclically at a rate of 72 cycles per minute. The load application point was predetermined by a waxing jig that was used to wax all crowns. The primary variable was the ferrule length. The independent variable was the number of load cycles required to create preliminary failure. Preliminary failure was defined here as the loss of the sealing cement layer between crown and tooth. An electrical resistance strain gauge was used to provide evidence of preliminary failure. The results of this study showed that the 0.5 mm and 1.0 mm ferrule lengths failed at a significantly lower number of cycles than the 1.5 mm and 2.0 mm ferrule lengths and control teeth.

Analysis of Variance↗

PubMed1993

Ischemia/reperfusion injury of the ascending colon in ponies: a correlative study utilizing microvascular histopathology and corrosion casting.

Volvulus of the ascending colon (ACV) in the horse results in microvascular injury and necrosis of the intestinal mucosa. This study investigated the site and type of microvascular injury which occurs within the mucosa and submucosa following ACV. Histopathology of volvulus treated ponies demonstrated mucosal necrosis with microvascular hemorrhage and thrombosis. Thrombi occurred within the subepithelial capillaries and edema and hemorrhage developed throughout the mucosa and submucosa. Vascular casts allowed 3-D viewing of samples obtained from the entire pelvic flexure and demonstrated two distinct microvascular changes: 1) disruption of the colonic glandular capillary network occurred concomitantly with the mucosal injury, and 2) extensive endothelial leakage from the submucosal microvasculature contributes to edema formation. Thus, microcorrosion casting of the equine pelvic flexure provided an effective means to characterize the location and severity of vascular leakage and visualize the extent and severity of injury to the capillary network not easily depicted by histopathology. Microvascular casting in conjunction with routine histopathology provided additional information on the pathomorphologic changes in this model of ischemia/reperfusion injury.

Animals↗

PubMed1993

Technical improvements in corrosion casting of small specimens: a study on mesonephric tubules and vessels of chicken embryos.

The injection technique for corrosion casting of small, embryonic material can be improved by using a "chemical ligature" (cyanoacrylate). With this simple method, leakage of the resin at the injection site is prevented and the mechanical stability of the cannula-vessel coupling is improved. The blood vascular system of chicken embryos as small as Hamburger-Hamilton stage 24 (approximately 4.5 days of incubation) has successfully been injected using this procedure. Corrosion casts of the mesonephric tubular system have been made in a similar manner. Additionally, a simple way for secure transport of the fragile casts by immersion in 10% gelatin is suggested.

Animals↗

PubMedDate not supplied

Evaluation of therapy for cast nephropathy: failure of colchicine to alter urinary Tamm Horsfall glycoprotein excretion in normal subjects.

Tamm Horsfall glycoprotein (THG) is a major constituent of renal tubular casts including the light chain casts of myeloma. Animal studies suggest that the anti-inflammatory agent colchicine reduces urinary THG excretion and prevents light chain cast formation. Six normal male subjects were given therapeutic doses of colchicine (0.5 mg twice daily for 6 days) and excretion of THG, albumin, creatinine and N-acetyl glucosaminidase (NAG) was determined. Colchicine therapy had no effect on the urinary excretion of THG, albumin or NAG or on renal function as assessed by creatinine clearance. This suggests that colchicine will not be a useful therapeutic adjunct to the treatment of light-chain nephropathy.

Acetylglucosaminidase↗

PubMed1994

Lung lymphatics increase after hyperoxic injury. An ultrastructural study of casts.

The microscopic lymphatics of the lung can be cast and studied with scanning electron microscopy. This technique shows several different forms of lymphatics and the interstitial space that leads into lymphatics as no other method can. To study changes in lymphatic forms, rats were placed in 85% oxygen for 7 days to produce pulmonary edema. Methyl methacrylate resin was injected into the lung vasculature at various times after the animals were removed from hyperoxia. In the animals not exposed to hyperoxia, no artery, vein, or airway was surrounded by a lymphatic cast. However, in rats that were in the hyperoxic chamber, 22% of arteries, 30% of veins, and 51% of indeterminate blood vessels (which could be arteries or veins) were encompassed by saccular lymphatic casts. These lymphatics were still observed 7 days after recovery from hyperoxia. Fourteen days after hyperoxia, the lymphatics returned to control values. Only 9% of the pleural surface of the animals not exposed to hyperoxia had initial lymphatics. Fifty-two percent of the hyperoxia-exposed animals had initial lymphatics, measured 3 days after exposure. This decreased to 14% 14 days after exposure to hyperoxia (P < 0.01). Conduit lymphatics were found on the pleural surfaces of 33% of animals exposed to ambient air and 100% of animals exposed to the high-oxygen environment (P < 0.05). The median percentage of the pleural surface covered with lymphatics was 0 in the animals exposed to ambient air. It was 65% in animals exposed to hyperoxia, 3 days after returning to room air. It was again 0 in animals exposed to hyperoxia, 14 days after returning to room air (P < 0.001). The lymphatics around veins expanded more than around arteries (P < 0.0001). These results indicate that in the rat all compartments of the lung lymphatics expand after the injury and edema caused by oxygen and return to normal with the resolution of the edema.

Animals↗

PubMed1993

Evaluation of a new glass ionomer cement "visible light cured" as a core buildup under a cast restoration.

Proper restoration of endodontically treated teeth is a frequent challenge to many clinicians. The majority of restorations are using various types of vertical support that can be placed in teeth, these include different prefabricated post systems as well as cast posts and cores. Less emphasis, unfortunately, has been placed on the materials utilized for final build up. Unless the tooth being treated undergoes minimal loss of tooth structure some from of augmentation will be necessary to increase the tooth strength and provide adequate support and retention for the final cast restoration. It is generally accepted that the ideal methods of corono-radicular buildup for nonvital teeth is a properly fabricated cast post and core.

Acrylic Resins↗

PubMed1993

A new method of attaching cast gold occlusal surfaces to acrylic resin denture teeth.

Historically, cast gold occlusal surfaces for complete or removable partial dentures have been fabricated with retentive loops or beads and luted to prepared denture teeth with acrylic resin or attached to tooth-colored, heat-processed acrylic resin. At present, alternatives to mechanical retention for attaching resin to metal include chemical bonding of the resin after placement of intermediate ceramic or tin layers and the use of chemically adhesive resin cements. Compared to mechanical retention, the chemical bonding of resin to metal requires less gold and allows more room for properly contoured and esthetic resin. Additionally, this chemical bond limits microleakage at the resin-metal interface. In the following technique, cast gold occlusal surfaces are fitted to onlay preparations of acrylic resin denture teeth set in a processed denture base. The castings are air-abraded, tin plated, and luted to the denture teeth with Panavia dental adhesive. This method is quick, easy, and economical.

Acrylic Resins↗

PubMedDate not supplied

[Covering dental defects with aluminum cast dowel construction and technology of their manufacture].

Clinical and laboratory studies have revealed benefits of aluminum cast constructions. Its cast dowel inserts are used in the system of fixed metal-free dentures made from ceramics (dental bridges, single crowns, etc.). The high efficiency, availability of casting technology for aluminum reduces patients' treatment periods and ensures accurate attachment of dowel insets to the root canal and stump of a tooth.

Adult↗

PubMed1977

[Surgical removal of cast calculi using extensive longitudinal nephrotomy].

The results of the operative treatment of 21 large longitudinal nephrotomies on account of the existence of cast calculi of the renal calyx are reported and discussed. In complete cast calculi with participation of the whole renal pelvis and all renal calyces this operation method leads to satisfactory results. Of the 12 cases (57-1%) with ideal postoperative morphological findings 83-3% became bacteriologically sterile; according to our opinion the lesion of the parenchyma due to operation is to be accounted for. In stone formations which do not fill all the calyces and yet in many cases in literature are called cast calculi, a pyelotomy or resection of the renal pole may by all means be the therapy of choice.

Adult↗

PubMedDate not supplied

The effect of using custom or stock trays on the accuracy of gypsum casts.

This study examined the linear dimensional stability of nonaqueous elastomeric impressions made from stock and custom trays by measuring casts derived from those impressions at 1 hour, 1 day, and 1 week. There was a small statistical difference among casts produced from stock versus custom trays compared to the master model. However, there was no significant difference in casts produced from impressions poured at 1 hour, 1 day, and 1 week. A custom tray with a 2.0 to 2.5 mm tray spacing had the least amount of variation, yet the differences between custom and stock trays may not be clinically significant.

Analysis of Variance↗

PubMed1996

Genetic diversity of PTC taste sensitivity among tribal and caste populations of Andhra Pradesh, India.

The present paper reports the variability of PTC taste sensitivity among eight endogamous tribal populations inhabiting the Eastern Ghats of North Coastal Andhra Pradesh. It was compared with the genetic diversity of PTC taste sensitivity among tribal and caste populations of Andhra Pradesh. The tribal and caste groups present a relatively high genetic diversity, of which a major proportion is due to genetic differences within populations rather than that between populations. Castes show a higher heterogeneity than tribes, the difference being significant. The high genetic diversity found among Andhra populations may be attributed to social stratification and the practice of strict endogamy.

Ethnicity↗

PubMedDate not supplied

Cast syndrome: the superior mesenteric artery syndrome.

Cast syndrome, clinically known as superior mesenteric artery syndrome (SMAS), is gastric dilatation with partial or complete obstruction of the duodenum. Although rare, it is most frequently seen in orthopaedic patients who have had spinal surgery or who are in hip spica or body casts. Obstruction occurs when there is compression of the duodenum between the superior mesenteric artery anteriorly and the aorta and spinal column posteriorly. Obstruction can occur within days of surgery or casting or may not develop for several weeks. Treatment for SMAS varies from conservative nonoperative to operative procedures. Complications can be severe if symptoms are not quickly recognized and treatment instituted in a timely manner.

Diagnosis, Differential↗

PubMed2000

A comparison of mechanical properties of all-ceramic alumina dental crowns prepared from aqueous- and non-aqueous-based tape casting.

Alumina-glass dental composites were prepared by aqueous- and non-aqueous-based tape casting and sintering at 1120 degrees C, followed by glass infiltration at 1100 degrees C. Flexural strength and fracture toughness of the composites were investigated in terms of influence of tape constituents, namely, alumina powder, binder, and plasticizer on the mechanical properties. For the alumina-glass composites prepared from the aqueous-based tapes, both strength and toughness increased with increasing alumina fraction ratio in tape constituents including organic substances, a/a+o, and binder content ratio in binder/binder + plasticizer mixture, b/b+p. For the composites prepared from the non-aqueous-based tapes, on the other hand, both strength and toughness increased with increasing the a/a+o ratio but decreased with increasing the b/b+p ratio. These observations were consistent with influence of the constituents on mean alumina particle distance in tapes, suggesting that high strength of the glass infiltrated alumina composites is related to toughening by crack bowing. The optimized strength of the aqueous and nonaqueous tape cast composites was 559 and 508 MPa, and the fracture toughness was 3.3 and 3.1 MPam(1/2), respectively.

Aluminum Oxide↗

PubMed1983

Casting accuracy of base metal alloys.

The effect of investment material on the casting accuracy of five base metal alloys was evaluated. Overall, the fit of the test castings was poor. Individual alloy-investment interaction appears to be significant. Although marketed for use with base metal alloys, it appears that investment manufacturers' recommended techniques require alteration to enhance the fit of base metal restorations.

Dental Alloys↗

PubMed1985

Internal setting expansion of a dental casting investment measured with strain gauges.

A study was undertaken to investigate the feasibility of using strain gauges to evaluate the internal setting expansion of dental casting investments. A strain gauge was invested in the center of a casting ring to determine the linear setting expansion at the site of the wax pattern. The findings suggest that strain gauges can be used to measure setting expansion internally more accurately than volumetric or external surface measurement techniques. It was also found that winged strain gauges were more stable in the investment than wingless strain gauges.

Chemical Phenomena↗

PubMed1995

Refining cast implant-retained restorations by electrical discharge machining.

The UCLA abutment was developed to create implant-retained restorations with ideal contours, excellent esthetics, and minimal vertical space requirements for restorative materials. A major drawback of this abutment is that casting inaccuracies in the lost-wax process are difficult to control. This article describes a method of refining cast implant-retained restorations by use of electrical discharge machining.

Dental Abutments↗

PubMed1983

The accuracy of occlusal cusp height in cast crowns.

Despite a good fit at the finish line, the occlusal cusp height decreased about 80 micron in gypsum-bonded cristobalite investments and increased about 40 micron in phosphate-bonded investments. Disks, tested as simulated occlusal portions of cast crowns, produced similar dimensional changes. This finding suggests that the occlusal cusp height is closely related to the thickness of the disk. An asbestos liner used with a gypsum-bonded investment failed to furnish adequate cushioning. The Kaowool liner provided good accuracy to the occlusal portion and finish line of cast complete crowns.

Calcium Sulfate↗

PubMed1998

A simple technique for exposing margins on a solid working cast.

Removable dies used in fixed prosthodontics typically exhibit movement. A solid working cast permits the technician to perfect the interproximal contacts of fixed prostheses. This saves the clinician time at the insertion appointment. This article describes a quick and easy procedure for making a solid working cast with easily visualized margins.

Calcium Sulfate↗