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At least 883 records · Page 49Linked to original sources
PubMed2006

The effect of adding a stone base on the accuracy of working casts using different types of dental stone.

AIM: Gypsum products are used for the preparation of stone casts of oral and maxillofacial structures and as important adjuncts to dental laboratory operations involved in the production of dental prostheses. The aim of this study was to determine the effect on the dimensional accuracy of a working cast of adding a stone base using different stone products. METHODS AND MATERIALS: A total of forty impressions of a mandibular dentoform were made. The impressions were dried with compressed air and stored at room temperature for 24 hours before pouring stone casts. The forty impressions were randomly divided into four groups of ten each. All forty impressions were poured once using one pre-weighed 140 Gm package of Silky Rock (SR) Type IV improved stone (Whip Mix Corporation, Louisville, KY, USA ) per impression. All working casts and the die setups were prepared according to the manufacturer's recommendations for pin placement (M.R. Dual pin and sleeve). Four different types of dental stone (II, III, and IV) and Flow Stone (FS) were used as bases for the working models. They were mixed according to the manufacturer's recommendations. The lower posterior teeth were flattened on the dentoform prior to taking the impressions. All were indexed using a mounted abrasive disc. Four teeth were selected as follows: 21, 28, 30, and 18. These represented A, B, C, and D landmarks, respectively. All measurements (five times for each specimen) were made with a Universal measuring microscope (Unitron Instruments, Inc., Bohemia, NY, USA). After the pre-sectioned measurements were recorded, the stone base was poured. A manual hand saw was used to section and fabricate removable dies for the mandibular landmarks A, B, C, and D. The dies were later seated and removed ten times to simulate the average amount of handling during laboratory procedures. Each die was carefully seated and measurements were made using the same technique as for the master model and unsectioned casts. Multivariate repeated measures analysis of variance (MANOVA) was used to test the difference in three different landmark distances (AB, AC, and AD) among the master model before and after sectioning of the working dies and among the four different base materials. Univariate analysis of variance (ANOVA) was conducted for each measurement, AB, AC, and AD to test the difference in landmark distances on the master model at pre sectioning and then at post sectioning using four different base materials. When there was a significant main effect (p < .05), the Student-Newman-Keul's (SNK) were used to test for pair wise comparison of means (P<0.05). RESULTS: The results of the MANOVA indicated there was a significant difference in three landmark measurements on the master model before and after sectioning of the working dies for the four different base materials (F = 6.60, p = 0.0001). In addition there was a significant difference in three landmark measurements on the master model at: (1) pre sectioning (p = 0.0001), (2) between the master model and SR material (p = 0.0002), (3) between the master model and Laboratory Plaster (LP) material (p = 0.0001), (4) between the master model and Quick Stone (QS) material (p = 0.0001), and (5) between the master model and FS material (p = 0.0001).

Calcium Sulfate↗
PubMedDate not supplied

Effect of water temperature on the accuracy of stone casts recovered from addition-reaction elastomeric impression materials.

This study investigated the accuracy of casts produced by mixing dental stone with water at different temperatures. Consecutive impressions of an acrylic resin model of the mandibular arch, on which the occlusal surfaces of three teeth had been indented with reference points, were made in two poly(vinyl siloxane) impression materials using a one-stage technique. After 1 hour these were cast in one of two stones using water at temperatures of 18 degrees C, 20 degrees C, or 24 degrees C. Five impressions were cast for each material at each temperature. The distances between the points were measured using a reflex microscope, and the difference between each cast and the model was calculated. Analysis of variance of the mean differences showed that there was no significant interaction between the temperature of the water and the accuracy of casts (P greater than 0.05).

Calcium Sulfate↗
PubMed1990

Relationship between critical convergence angle and surface defects in stone casts.

Surface defects on stone casts threaten the accuracy of cast restorations. The aim of this study was to examine the relationship between critical convergence angle and voids in stone casts. Three addition silicone materials, one condensation silicone material, and one polyether impression material were used. The highest convergence angle at which voids presented at the tip of the specimens was recorded, and the number of voids found at margins and line angles of the tooth preparations were counted. Results showed a positive and significant correlation between the critical convergence angle and the number of voids at margins and line angles of stone casts. Casts poured from polyether impressions registered significantly lower critical convergence angle values and presented with fewer voids than did those fabricated from silicone materials.

Calcium Sulfate↗
PubMed1990

Accuracy of complete dental arch impressions and stone casts using a three-dimensional measurement system. Effects on accuracy of rubber impression materials and trays.

The purpose of this study was to investigate and compare the accuracy of complete dental arch impressions and stone casts made with two kinds of impression materials (addition-type silicone and polysulfide rubber) and trays (custom tray and modified custom tray). In addition, the effect of the quantity of stone was examined. Impressions were made from a metallic model of a simplified maxillary dentition. Impressions and stone casts were measured respectively with a three-dimensional measuring microscope. The results were as follows: 1. Distortions of impressions were so small that the reproducibilities of impressions were superior three-dimensionally. These kinds of impressions and trays did not influence the accuracy of impressions. 2. The setting expansion of the stone in the impression occurred in the outward direction and was affected by the kinds of impressions and trays. 3. The arch widths and lengths of the stone casts tended to increase in number. 4. Stone casts made with addition-type silicone impression material and a custom tray were the most accurate because the combination of the impression material and tray effectively suppressed the setting expansion of stone. 5. The accuracy of stone casts could be improved by controlling the quantity of stone.

Calcium Sulfate↗
PubMed1990

[Bond strength of dental luting cements to titanium castings].

This study compared the tensile bond strength of dental luting cements to the titanium castings with gold alloy (Type IV), 12% Au-Ag-Pd alloy and Ni-Cr alloy in dental clinical practice. In this experimental condition, the zinc phosphate cement did not adhere to any dental casting alloy tested. The tensile bond strength of polycarboxylate cement to the titanium castings was 96 kg/cm2, about two times as high as that gold alloy (Type IV). The tensile bond strength of the glass ionomer cement to titanium castings was 32 kg/cm2, about two times as high as that of dental precious alloys. The tensile bond strength of the adhesive resin cement to titanium castings was 220 kg/cm2, about three times as high as that of dental precious alloys.

Dental Alloys↗
PubMed1988

Characterization of solid tumor microvasculature: a three-dimensional analysis using the polymer casting technique.

Using a polymer casting technique in conjunction with scanning electron microscopy, the three-dimensional characterization of tumor microvasculature as a function of age of renal adenocarcinoma in the rat kidney is undertaken. The microvasculature of the rat tumor model is compared with VX2 carcinoma in the rabbit leg muscle. Light microscopy and transmission electron microscopy on the rat tumor model are performed to correlate the features seen under scanning electron microscopy of vascular casts. The casts show marked differences between tumor and normal microvasculature. The tumor vascular architecture appears disarrayed with prevalent atypical features such as coils, ribbons, sheets, dense capillary networks, saccular dilatations, leaky and otherwise highly irregular vessels. Sprouts of new growth capillaries are seen throughout the tumor casts. Compressed vessels are present and become more pronounced in older tumors. These features are not observed in normal controls treated under identical conditions. The application of this high resolution three-dimensional casting technique to tumor studies is promising for research in basic tumor mechanics as well as in the effects of tumor vasculature on mediating radiation and chemotherapy and the fundamental mechanisms of metastasis.

Adenocarcinoma↗
PubMed1986

Quantitative vascular casting of the post-ischemic hydronephrotic kidney.

The renal microvasculature (afferent arteriole) and glomeruli were examined and quantitated by two methods in the post-ischemic hydronephrotic (PIH) kidney. The methods used were: an in vivo examination and controlled perfusion-fixation, quantitative vascular casting examined by scanning electron microscopy. The second method was also applied to the vasculature of the contralateral, functional kidney. The goals of the study were to: validate the quantitative vascular casting method by comparing PIH renal microvascular data from the casting method with in vivo values and determine the extent of microvascular dimensional difference of the PIH kidney from its contralateral functional counterpart. It was determined that the casting values were consistent with the data obtained from the in vivo examination of the afferent arteriole and glomeruli. This finding provides further support for the quantitative renal microvascular casting technique. Using that technique it was determined that the dimensions of the microvasculature and glomeruli of the PIH kidney were severely (and significantly, p less than 0.05) reduced compared to its functional mate. Since these PIH vessels show a significant decrement in size, vascular reactivity and functional data based on the PIH vessels should be looked at cautiously. The vasculature and glomeruli of the PIH kidney might not be totally normal, however structurally, the glomeruli do not appear to be dramatically altered.

Animals↗
PubMed1981

Cast vs extruded Biomer for biomedical applications.

The properties of solution grade and extrusion grade Biomer have been investigated and compared. In vivo blood compatibility studies using arteriovenous (AV) shunts of the cast and extruded materials show that extruded Biomer is more thromboresistant than solution cast Biomer. This has important implications for long-term implantation studies, since solution cast Biomer is used in artificial hearts. This study also indicates that extruded Biomer, dissolved in DMA and then solution cast, is more thromboresistant than cast solution grade Biomer. Surface studies using ESCA indicate a correlation between thromboresistance and surface soft segment concentration.

Animals↗
PubMed1980

Replica casts of the entire respiratory airways of experimental animals.

A method is presented for producing silicone rubber replica casts of the entire respiratory airways (nasal cavity, pharyngeal region, and lungs) for toxicological assessment of inhaled particles and gases. Established methods for producing casts of the lungs are combined with other methods for faithful casting of the nasopharyngeal region to simultaneously cast all the respiratory regions of a given animal. The resulting detailed, flexible casts can be examined for comparison of the features and relative positions of the regions of the respiratory tracts of various animal species.

Animals↗
PubMed1981

Morphology of renal tubular hyaline casts.

The structure of renal tubular hyaline casts in kidney biopsies from patients with the nephrotic syndrome was studied and defined by light, immunofluorescence, and electron microscopies. Two distinct types of casts were identified. One, intensely stained with periodic acid-Schiff's reagent, was formed almost exclusively of myriads of fine, hollow tubular fibrils of indefinite length and approximately 40 Angstroms in width. The other, of slight periodic acid-Schiff positivity, was made up chiefly of a finely granular, medium dense matrix, often, however, with similar filaments as above but in considerably lesser quantities, as well as numerous remnants of degenerating cytoplasm. The fibrillar matrix of both of these casts is clearly Tamm-Horsfall protein, previously demonstrated to have identical fine structural features when studied as filaments isolated from urine. Furthermore, with the use of specific fluoresceinated antiserum, most casts were shown to consist of Tamm-Horsfall protein. The filaments comprising the casts may be confused with amyloid because of ultrastructural similarities, especially when observed in urinary sediments.

Biopsy↗
PubMed1995

Morphological remodeling of the motor end plate in rat soleus muscle after limb immobilization by casting.

The effects of muscular inactivity on motor end plate(MEP) structures of the rat soleus muscle were studied qualitatively and quantitatively. Eight adult rats were divided into two equal groups. One group had their right hind limbs immobilized by application of plaster casts. After 14 days in the casts, the soleus muscles of all the animals were removed. Three groups of MEPs were analyzed to compare their structural characteristics: the immobilized group (the MEPs of the casted soleus muscles), the contralateral group (the MEPs of soleus muscles which were in legs contralateral to the casted legs), and the control group (the MEPs of normal soleus). The MEPs were examined in a teased preparation of soleus muscles stained by silver-impregnation. The architecture of the MEPs was measured by an "AMS VIDS III Image Computerized System" which was mounted with a light microscope for morphological analysis. The measured parameters were the structural elements of MEPs. The results of the present study showed that: MEPs of the immobilized group exhibited more complex and highly branches structures than the other two groups. The total number of branches and the length of the terminal perimeter in the immobilized group increased significantly. Concomitantly, the amount of swollen terminals of this group were obviously larger than in the other two groups. The results demonstrated that the muscular inactivity of the casted limbs produced denervation-like changes at branches of nerve terminals. These changes were the result of altered muscular function, and led to structural remodeling of MEPs of the muscles.

Animals↗
PubMed1976

Experimental Bence Jones cast nephropathy.

C3H mice received intraperitoneal injections of a single dose of 50 to 200 mg. of purified lambda Bence Jones protein. Control animals received injections of comparable amounts of ovalbumin. The mice which received 200 mg. of lambda Bence Jones protein developed extensive cast formation in the distal renal tubules. By electron microscopy, the casts were found to contain elongated crystalloid structures. In some areas, these crystalloids appeared to penetrate into or be engulfed by tubular epithelial cells. By immunofluorescence, only lambda Bence Jones protein was detectable in the casts during the first 5 days. Thereafter, Tamm-Horsfall protein was also found in increasing amounts. The casts induced an inflammatory response characterized by the sequential appearance of polymorphonuclear leukocytes and mononuclear cells. The secondary tubular cell changes included atrophy, degeneration, and regeneration. Giant cells were present around many casts, but it could not be determined whether these derived from tubular epithelial or mononuclear inflammatory cells. Elevated blood urea nitrogen was found terminally in most animals. Smaller doses of the same protein as well as preliminary studies with two other lambda Bence Jones proteins failed to produce comparable changes. This experimental model of Bence Jones nephropathy closely resembles the morphologic features of so-called "myeloma kidney" in man.

Animals↗
PubMed1994

Blood groups, ABH saliva secretion and colour vision deficiency in Hindu castes and religious groups of West Godavari, Andhra Pradesh, India.

The distribution of A1A2B0 and Rh(D) blood groups, ABH saliva secretion and red-green colour blindness among fourteen Hindu caste groups, besides Christian and Muslim populations of West Godavari District, Andhra Pradesh, India, is reported. All the Hindu castes except Brahmin, Kshatriya and Reddy exhibit relatively higher frequency of group B over group A. The subtyping of group A reveals that group A2 records an incidence ranging from 0.98% to 7.78%. The interpopulation chi-square tests for A1A2B0 blood group distribution indicate significant variation between several Hindu castes. The Vysya, Reddy and Adi Andhra castes not only differ from each other but also register significant variation from a majority of other populations. In the ABH saliva secretion also Vysya deviate from all other populations by recording the highest incidence (37.70%) of non-secretors, while the lowest frequency (19.98%) was observed among Kamma. The Rh(D) negative blood group is observed in all Hindu castes and religious groups with an incidence ranging from 1.04% in Vysya to 8.11% in Kamma. All the sixteen populations investigated exhibit prevalence of red-green colour blindness with a relatively higher frequency of deutan type over protan.

ABO Blood-Group System↗
PubMed1996

Variation in palmar interdigital ridge-counts among the 20 Dhangar castes of Maharashtra, India.

Bilateral palmar prints of 2927 males of 20 endogamous Dhangar castes of Maharashtra, India, were studied for the distributions of a-b, b-c and c-d interdigital ridge-counts. The ridge-counts have been utilized for examining the inter-population affinities among the Dhangar castes. The distribution of a-b ridge-counts is symmetrical and normal in Dhangar castes. The distributions of b-c and c-d ridge-counts on both palms also show (nearly) normal distribution, but with a tendency of negative skewness and platykurtosis in c-d ridge-count. Equality of means and standard deviations depict significant heterogeneity. The decreasing order of magnitude of means of interdigital ridge-counts is a-b > c-d > b-c among all the Dhangar castes. Intercaste comparisons reveal a great deal of variations in all ridge-counts. The pattern of relationship between the Dhangar castes based on the three ridge-counts is in agreement with the expected patterns of affinities based on the known ethno-historical evidence. The significant finding of the study is that the palmar interdigital ridge-counts follow normal distribution and that they are useful in studying inter-population affinities.

Adolescent↗
PubMedDate not supplied

Comparative study between skin prick tests and TOP-CAST allergen leukocyte stimulation in diagnosis of allergic status.

A recently developed CAST-ELISA method was applied to determine allergen-induced leukocyte stimulation. This method is based on the measurement of sulfidoleukotriene secretion by peripheral blood leukocytes previously stimulated with specific allergen in the presence of interleukin 3. 24 patients allergic to different aeroallergens and some food allergens were included in this study. Subjects received no medication 2 weeks before the testing. Leukocytes were isolated by dextran sedimentation. After incubation with allergen at two concentrations, the cells were centrifuged and the concentration of sulfidoleukotrienes in supernatant was determined. The results were expressed in pg/ml after subtraction of values of spontaneous sulfidoleukotriene production in portions incubated without allergen. We observed a wide range of sulfidoleukotriene secretion upon allergen stimulation. Concentrations of leukotrienes ranged from 0 to 5780 pg/ml at lower allergen concentration and from 210 to 5680 at higher allergen concentration. On the basis of observed results, we conclude that the better allergen concentration is the higher one because there was no appearance of negative cell stimulation. In the lower allergen concentration we observed negative results in two cases. Sixteen healthy control subjects were also included in this study. Eleven subjects had negative skin prick tests (SPT) as well as CAST results. In 5 healthy subjects with positive SPT, we also observed positive CAST results in 4 persons. In 1 healthy person with positive SPT results, CAST results were negative. We conclude that TOP-CAST allergen is a valuable mixture of different aero and food allergens for determining the allergic status in patients with suspicious allergic status, although it cannot differentiate between health and disease states.

Allergens↗
PubMed1996

Physical properties of casts prepared from disinfected alginate.

The dimensional accuracy, surface hardness and reproduction of surface detail of stone casts produced from alginate impressions treated with 4.65% sodium hypochlorite, were investigated. To test dimensional accuracy, a Reflex Microscope was used to compare casts from 10 untreated impressions with casts from 10 impressions immersed in the solution for 30 mins. Surface detail and hardness were investigated on casts produced from impressions of a master stainless steel plate with 10 micro-indentations of increasing size. Surface detail of the casts were assessed by observation and surface hardness by a Vickers Hardness Machine. The dimensional accuracy test showed no significant differences between the experimental and control groups. Surface detail was unaffected after immersion of up to 10 mins. Surface hardness decreased linearly with respect to immersion time, when this was greater than 5 mins.

Alginates↗
PubMed2001

Calcium-phosphate surface coating by casting to improve bioactivity of titanium.

In order to improve the bioactivity of titanium, an original surface treatment was attempted with the use of a casting technique was attempted. Pure titanium was cast into a special graphite mold in which the cavity wall was coated with hydroxyapatite (HA) powder. According to analyses of X-ray diffraction and EDX, the existence of HA and CaO and uptake of Ca and P on the surface of the titanium castings were identified. By immersing the specimen in Hank's solution, the concentrations of Ca and P on the surface increased with immersion time, and the formation of a thin layer with characteristics of spherical HA precipitates was observed after 1 week. The concentrations of Ca and P elements and the Ca/P ratio on the HA layer increased with immersion time. The formation of the HA layer on the titanium cast by this treatment was significantly accelerated compared with pure titanium. The present surface treatment of Ti is expected to improve early bone fixation of Ti implants.

Biocompatible Materials↗
PubMed1980

The cast aluminum denture base. Part II: Technique.

A technique to wax-up and cast an aluminum base and a method to incorporate the base into the final denture base has been discussed. This technique does not use induction casting, rather it uses two casting ovens and a centrifugal casting machine.

Aluminum↗