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At least 1,135 records · Page 63Linked to original sources
PubMed1976

[Studies on high temperature oxidation of noble metal alloys for dental use. (II) Effects of high temperature oxidation on casting (author's transl)].

The specimens which were cast from commercial alloys were polished metallographically and then oxidized at 800 degrees C for 1 hour in air. The results obtained were as follows: 1. The reduction rate of Cu aginast the original Cu amount in the alloy is given by the following equation: (see article) where S is surface area of the casting, KW is oxidation rate constant, t is time, Wc is weight of the casting, Ccu is weight percent of Cu, and n is between 1 and 2. 2. Owing to decrease of the Cu concentration in the outer layer of the alloy, the age-hardening did not appear in that layer. 3. Reflexibility of the polished surface of alloys became lower than that of the matrix due to precipitation of the oxide particles. 4. Hardness numbers of the internal oxidation zone (oxide particles, ZnO) decreased to 1/2 of the matrix. 5. The surface roughness of specimens after pickling was affected by the shape of oxide particles in the internal oxidation zone and varied with the different commercial alloys. 6. The dimensional change of casting due to oxidation is given by the following equation: (see article) where sigmacu is density of copper, KW is oxidation rate constant, t is time and n is between 1 and 2.

Copper↗
PubMed2000

Clinical evaluation of fiber-reinforced epoxy resin posts and cast post and cores.

PURPOSE: This retrospective study evaluated treatment outcome of cast post and core and Composipost systems after 4 yrs of clinical service. MATERIALS AND METHODS: 200 patients were included in the study. They were divided in two groups of 100 endodontically treated teeth restored with a post. Group 1: Composipost systems were luted into root canal following the manufacturer's instructions. Group 2: Cast post and cores were cemented into root canal preparations with a traditional technique. The patients were recalled after 6 months, 1, 2 and 4 yrs and clinical and radiographic examinations were completed. Endodontic and prosthodontic results were recorded. RESULTS: Group 1: 95% of the teeth restored with Composiposts showed clinical success; 3% of these samples were excluded for noncompliance and 2% showed endodontic failure. Group 2: Clinical success was found with 84% of teeth restored with cast post and core. 2% of these samples were excluded for noncompliance, 9% showed root fracture, 2% dislodgment of crown and 3% endodontic failure. Statistical evaluation showed significant differences between Groups 1 and 2 (P < 0.001). The results of this retrospective study indicated that the Composipost system was superior to the conventional cast post and core system after 4 yrs of clinical service.

Boron Compounds↗
PubMed2002

Laboratory diagnosis of hymenoptera venom allergy: comparative study between specific IgE, western blot and allergen leukocyte stimulation (CAST).

Allergy to hymenoptera venom is a classical IgE mediated disease with a potentially fatal course. Specific venom immunotherapy (SIT) is the most effective mean of treating this serious condition, after the diagnosis has been clearly established by a clinical history, in-vivo and in vitro tests. We have evaluated the usefulness of a cellular test (CAST) which is a recently developed ELISA method based on the evaluation of sulfidoleukotriene secretion by leukocytes stimulated with specific antigen. We also evaluated the correlation of CAST with skin tests, specific IgE (sIgE) and western blot for sIgE for hymenoptera venom sIgE. We have included in this study 14 patients, with a clinical history suggestive of hymenoptera venom allergy. None of them had previously been subjected to immunotherapy. A good correlation was obtained between skin tests, sIgE and western blot. However, there was no correlation between these methods and CAST. We conclude that the positivity of CAST method raises some questions about other mechanisms, which maybe non-IgE dependent. Although the number of patients in this study is quite small, the immunoblot analysis may be a valuable additional method in insect venom allergy.

Antibody Specificity↗
PubMedDate not supplied

Elements released from dental casting alloys and their cytotoxic effects.

PURPOSE: This in vitro study investigated the element release from seven commercially available dental casting alloys and tested their cytotoxic effects. MATERIALS AND METHODS: The casting alloys tested were one high-noble alloy (Bioherador N) and six base-metal alloys, including four Ni-Cr alloys (Remanium CS, Heranium NA, Wiron 99, CB Soft), one Co-Cr alloy (Wirobond C), and one Cu-based alloy (Thermobond). Ten specimens from each alloy were prepared in the form of disks, and each of the seven dental casting alloys (10 disks per group) were conditioned in distilled water at 37 degrees C for either 72 or 168 hours. The conditioning media were analyzed for element release, and the cytotoxic effects were assessed on Balb C fibroblasts using MTT assay. RESULTS: Element release was greater at 168 hours of conditioning than at 72 hours. The extract from the high-noble alloy showed the least amount of element release (only Zn), with no cytotoxic effects. The greatest amount of element release was detected in the Cu-based alloy Thermobond and the Ni-Cr alloy CB Soft; their extracts were significantly more toxic than all the other alloy extracts. The cytotoxic effects of the other Ni-Cr alloy extracts were not statistically significantly different from the high-noble alloy extract. However, the Co-Cr alloy (Wirobond C) extract was significantly more cytotoxic than the high-noble alloy extract. CONCLUSION: Element release from casting alloys is proportional to the conditioning time. The content of Cr and Mo in the alloy protects the alloy from dissolution, while the Cu content makes it more susceptible to corrosion and dissolution, rendering it more cytotoxic.

Analysis of Variance↗
PubMed2003

A biomechanical study in cadavers of cast boots used in the early postoperative period after first metatarsophalangeal joint arthrodesis.

OBJECTIVES: To compare the effectiveness of 3 common models of walking boots (Walkabout, Samson Walker and Equalizer Premium Walker) to that of a fibreglass cast in protecting an arthrodesis of the first metatarsophalangeal (MTP) joint in the early postoperative period, we carried out a biomechanical study in cadavers in the bioengineering laboratory at Memorial University of Newfoundland. METHODS: Two cadaver models of a first MTP joint arthrodesis were prepared by placing a strain gauge at the joint. This provided a measure of the bending moment across the fusion site. Walking was simulated by applying a force to the sole of the cadaver foot at multiple positions from heel to toe, representing the stages of gait from heel strike to toe off. RESULTS: For both cadaver specimens, the Walkabout boot had the lowest mean moment. The Walkabout and Sampson Walker boots were better than the Equalizer Premium Walker boot and the fibreglass cast (p < 0.05), but the Walkabout boot was the best (p < 0.05). Also, for both specimens, the Walkabout boot had the smallest absolute maximum moment (p < 0.05). CONCLUSION: On a first MTP joint arthrodesis site, removable cast boots provide the same, if not more, reduction of force as a traditional cast.

Arthrodesis↗
PubMedDate not supplied

Influence of timing of coronal preparation on retention of cemented cast posts and cores.

PURPOSE: This study investigated the effect of coronal preparation by high-speed handpiece on the retention of cemented cast posts and cores. MATERIALS AND METHODS: Cast posts and cores were fabricated for 90 extracted single-rooted human teeth cemented with zinc-phosphate cement and randomly divided into six groups of 15 specimens each. The six groups were matched randomly two by two, such that one of each of the matched groups was subjected to a 4-minute period of high-speed preparation of the cores. Castings from the first pair (1 and 2) were subjected to an axially directed removal force using a universal testing machine 15 minutes from the start of cement mixing; castings from the second (3 and 4) and third (5 and 6) pairs were tested at 1 hour and 24 hours, respectively, having been stored in water at 37 degrees C for the waiting periods. The forces required for dislodgment of posts from their prepared spaces were recorded. Data were statistically analyzed using two- and one-way ANOVA and the Student's t test. RESULTS: The results showed increased mean retentive strengths of posts as the time to testing increased for both unprepared and prepared groups. Significantly higher mean retentive strengths of posts were recorded for unprepared compared to prepared groups tested at 15 minutes and 1 hour after cementation. CONCLUSION: High-speed preparation had a significant negative effect on the retentive strengths of posts tested at 15 minutes and 1 hour after cementation, but not on those tested at 24 hours.

Analysis of Variance↗
PubMed2004

Mammographic casting-type calcification associated with small screen-detected invasive breast cancers: is this a reliable prognostic indicator?

AIM: The aim of the present study was to establish whether mammographic casting-type calcification associated with small screen-detected invasive breast cancers is a reliable prognostic indicator. METHODS AND MATERIALS: We retrospectively identified 50 consecutive women diagnosed with an invasive cancer less than 15 mm who showed associated casting calcification on their screening mammograms. Controls were identified that showed no microcalcification and were matched for tumour size, histological type and lymph node status. A minimum of 5 years follow-up was obtained, noting recurrence and outcome. Conditional and unconditional logistic regression, depending on the outcome variable, were used to analyse the data, taking the matched design into account in both cases. Where small numbers prohibited the use of logistic regression, Fisher's exact test was used. RESULTS: Five deaths from breast cancer occurred out of the 50 cases, of which three were lymph node positive, two were lymph node negative and none were grade 3. None of the 78 control cases died from breast cancer. The difference in breast cancer death rates was significant by Fisher's exact test (p=0.02). Risk of recurrence was also significantly increased in the casting cases (OR=3.55, 95% CI 1.02-12.33, p=0.046). CONCLUSION: Although the overall outcome for small screen-detected breast cancers is good, our study suggests that casting calcification is a poorer prognostic factor. The advantage of a mammographic feature as an independent prognostic indicator lies in early identification of high-risk patients, allowing optimization of management.

Breast Neoplasms↗
PubMed2001

[Effect of graphite and phosphate investments on the biological characteristics of pure titanium castings].

OBJECTIVE: To investigate the effect of surface structural changes caused by graphite and phosphate investments on the biological characteristics of pure titanium castings. METHODS: Round casting pads of pure titanium were processed by graphite and phosphate investments respectively, then grouped into four. With the control of guta purca of the same size, Ultraviolet spectrometry was used to test the cytotoxicity of samples via the ISO, GB and Shanghai biomaterial research and testing center's standards. Mucous irritation test was performed on hamsters' pouch. RESULT: Titanium castings obtained from both investment materials have reached the national standard of cytotoxicity and mucous irritation test no matter they have been undergone surface treatment or not. CONCLUSION: Both investment materials cause no obvious changes on biological characteristics of pure titanium castings with the existing of surface structural changes.

English Abstract↗
PubMed1999

[The effect of EDTA with different density on adhesive power of casting post and its scanning electromicroscopy (SEM) observation]

OBJECTIVE:To evaluate the effect of EDTA with different density on adhesive power of casting post.METHODS:Four different density of EDTA(5%,10%,15%,17%)were used to rinse the smear layer of root canal for 60 extracted teeth before they were cemented with ZP;on the other,a SEM observation was made on the rinse of root canal and the combination of adhesive and root canal.Meanwhile,a comparison was also made, after the rinse of EDTA,of tensile strength of casting post after their cement.RESULTS:EDTA with different density have different effect in the rinse of smear layer of root canal,it was proved by both SEM observation and the records of tensile strength of casting post. CONCLUSION:EDTA with density 10% is more effective in both the rinse of smear layer of root canal and the enhancement of adhesive power of casting post.

Journal Article↗
PubMed1997

[Study on the compatibility of slip casting aluminous ceramic crowns]

One of the key factors for a good slip casting aluminous ceramic crown is good compatibility between its core material and the veneering porcelain.The chemical and thermal compatibility of two slip casting aluminous ceramic crown systems(In-Ceram and GI-I) were investigated by means of SEM and EDAX,thermal shock tests were also performed to evaluate the crazing resistance.The results showed: the crazing resistance of In-Ceram was 158 degrees centigrade,and that of GI-I was degrees centigrade;there existed tightly bonded interfaces between the slip casting aluminous ceramic cores and the veneering porcelains in both of the two systems,where ion transferences were found.The results also suggested good compatibility of the two slip casting aluminous ceramic crown systems.

Journal Article↗
PubMedDate not supplied

Intermittent loading of teeth with tapered, individually cast or prefabricated, parallel-sided posts.

This study compared the resistance to intermittent loading of teeth with tapered, individually cast posts and cores or prefabricated parallel-sided posts (Para-Post, Whaledent) and composite cores. Bovine teeth mounted in acrylic resin blocks with a simulated periodontium were used for the study. Two conditions were studied. One group received individually fabricated posts and cores, the second had titanium prefabricated posts and resin composite cores placed. All teeth receiving posts and cores had cast crown restorations placed. Teeth were intermittently loaded using a force of 250 N twice each second at an angle 45 degrees to the long axis until failure occurred. Teeth with prefabricated posts and resin composite cores showed a significantly higher resistance to intermittent loading than did teeth with tapered, individually cast posts and cores. Additional restored teeth were sectioned and the adaptation of the posts to the root were measured. The adaptation of the prefabricated posts was better than that of tapered, individually cast posts.

Analysis of Variance↗
PubMed1992

Myeloma-like cast nephropathy caused by human recombinant soluble CD4 (sCD4) in monkeys.

CD4 is the receptor for human immunodeficiency virus (HIV) on lymphocytes and macrophages. Soluble CD4 (sCD4), a recombinant truncated form of CD4, has been shown to inhibit HIV-1 in vitro and is being tested as a therapy for AIDS. Preclinical studies in cynomolgus monkeys revealed a protein cast nephropathy after four daily intravenous doses of 100 mg/kg/day. Renal lesions were not found in monkeys that received 10 mg/kg/day. The renal lesions consisted of proteinaceous tubular casts associated with multinucleate giant cells and neutrophils located in the tubules of the distal nephron. The affected tubules were surrounded by an interstitial mixed inflammatory cell infiltrate. By electron microscopy, the casts were composed of moderately electron dense, paracrystalline material. Immunostaining demonstrated that the casts contained sCD4-derived material and Tamm-Horsfall protein. Moreover, biochemical analysis of urine showed that a portion of sCD4 was excreted as intact protein. Because infection with HIV-1 can be associated with clinically significant nephropathy, these data suggest that renal function should be closely monitored in patients receiving soluble forms of CD4.

Animals↗
PubMed2005

[Development and study of three-dimensional CT scanning system for dental cast measurement and analysis].

OBJECTIVE: To develop a computer assisted CT scanning system for 3D dental cast measurement and to study its reliability. METHODS: 20 dental stone casts were scanned by helical CT and captured a series digital sliced radiographs of them. The program which was developed by Visual C 6.0 language and run under the Windows surroundings rebuilt the 3D graphics and measured the coordinate of the dental cast. These dental casts were scanned and measured to test the reliability of the system, contrasting with manual measurement. RESULTS: There was no significant difference between 3D CT scanning and manual measurement (P > 0.05). CONCLUSION: The system is a valuable computer assisted system for clinical diagnosis and treatment of malocclusion.

Humans↗
PubMed2005

[The mechanic retention of the casting post with keeper in magnetic retentor overdenture].

PURPOSE: To reduce the cost of the fabrication of the magnetic retentor,and meet the clinical requirements, nonprecious alloy such as Co-Cr alloy was used to fabricate the magnetic retentor in overdenture , instead of the precious alloy. METHODS: A mandibular canine was chosen for root canal preparation in vitro. Thirty two resin posts were made in the same root canal with self-curing resin. The 32 resin posts were randomly divided into 4 groups. Among them,2 groups were fabricated with soft Co-Cr alloy, gold alloy(55.6%Au) respectively in vitro. Another 2 groups were fabricated with Co-Cr alloy, and the surface of the root casting post with keeper were treated with gold deposit and gold coating technique. After that, test of dislodgment force was done and one-way ANOVA was performed with SAS 6.2 software package. RESULTS: The dislodgment force of the root casting posts with keeper which were fabricated with the Co-Cr, Ni-Cr, and gold alloy had significant difference(P<0.01). While after surface treatment by gold deposit and gold coating technique on root casting posts with keeper that were fabricated with Co-Cr and Ni-Cr alloy, there was no significant difference in dislodgment force, compared with that of gold alloy. CONCLUSIONS: After surface treatment of the root casting posts with keeper which were fabricated with the Co-Cr and Ni-Cr alloy, the same clinical retentive effect can be obtained as the one that was fabricated with gold alloy.

Chromium Alloys↗
PubMed2006

[Effects of different polishing methods on surface roughness of pure titanium castings].

OBJECTIVE: To evaluate the effects of different polishing methods on surface roughness of pure titanium castings. METHODS: 35 pure titanium castings were devided into 7 groups, used for control, mechanic polishing and electrolytic polishing, respectively. Surface roughness (Ra value) of each castings was measured with a profilometer. Surface microstructure was studied by a scaning electron microscopy, and the weight loss (Wt%) and height loss on unit area (H) before and after polishing was calculated. RESULTS: The effects of mechanic polishing with aluminium oxide or chromium oxide were acceptable. Surface smoothness was improved with acid treatment followed by electrolytic polishing. CONCLUSION: Aluminium oxide and chromium oxide can be used in mechanic polishing of pure titanium castings, and improvement should be made on electrolytic polishing methods.

Aluminum Oxide↗
PubMed2006

[A case of relapsed ischemic colitis with colon cast-like stripped mucosa].

An 82-year-old woman who had 5 relapses of ischemic colitis was admitted with sudden lower abdominal pain. Colonoscopic examination performed on the 2nd day revealed colon cast-like stripped colonic mucosa in the lower portion of the descending colon. She was treated conservatively. After 2 weeks, ischemic colitis healed, with slight residual stenosis. Most reports of colon cast indicated that colon cast was caused by abdominal aneurysm, operation, or external wound. The only predisposing conditions in this case were arteriosclerosis of abdominal aorta and chronic constipation. Arteriosclerosis and chronic constipation might be the important risk factors of ischemic colitis with colon cast and relapsing of ischemic colitis.

Aged, 80 and over↗
PubMed1991

[In vitro study on the corrosion behavior of two amalgams in direct contact to different cast metal alloys].

The direct contact between amalgam and cast metal may enhance electrochemical reactions. In a study to determine the amount of mercury released in these reactions, six cast metal alloys with increasing precious metal contents were placed in immediate contact (contact area 10 mm2) to two non-gamma 2-amalgams (Amalcap, Valiant) and incubated with artificial saliva at 37 degrees C for up to 8 weeks; then the salivary mercury concentrations were measured. After the end of the incubation period the case metal surfaces were analyzed by ESCA for metal appositions. The results showed that direct contact between amalgam and cast metal after storage in artificial saliva for 8 weeks resulted in a minor release of mercury (22.7 +/- 10.63 ng/ml Hg). On the cast metal plates themselves only smallest mercury concentrations could be demonstrated. These in vitro tests have shown again that, although charge transfers do occur when different metals are in direct contact, they do so only to a minor degree, because of the passivation processes involved.

Corrosion↗
PubMed1990

Improving the adaptation of denture bases by anchorage to the casts: a comparative study.

The purpose of this study was to investigate the adaptation of complete maxillary dentures to stone casts processed by the conventional, and two anchoring, methods. The anchoring methods used holes drilled on the cast and a special flange extended onto the posterior aspect of the maxillary cast. Both anchoring methods improved the adaptation of denture bases by minimizing the discrepancy between the denture base and cast. The greatest discrepancies observed in all methods were at the central portion of the posterior border.

Denture Bases↗