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PubMed1989

[A study of secondary caries in cast restored teeth].

The purpose of this study was to investigate the state of the natural secondary caries and in vitro artificial secondary caries, associated with cast restorations cemented with zinc phosphate cement, histopathologically. For this study, the method of making and staining ground serial sections of teeth with cemented cast restorations was established. The material consisted of 50 extracted human permanent teeth with cemented cast restorations, and 12 human premolar teeth with in vitro secondary caries produced by the acid-gelatin system (pH 4.0). These specimens were embedded in MMA resin and then they were sliced to serial thin sections. Each section was etched by 0.1 N HCl, and stained with methylene blue fuchsin, and then observed with optical microscope, microradiography, and SEM. The result were as follows: 1. When the margin of restoration was set on dentine (cementum), the typical shape of natural secondary caries was found out. 2. The rate of natural secondary caries in case of margin set on dentine was about four times as many as the rate in case of margin set on enamel. 3. The shape of artificial secondary caries was very similar to the shape of natural secondary caries. 4. The resistance to secondary caries in case of the margin set on enamel was higher than the resistance in case of the margin set on dentine.

Crowns↗
PubMed2004

[Influence of cavity lining on marginal leakage beneath cast restoration].

PURPOSE: This study investigated the effect of a cavity lining on marginal leakage of a cast restoration. METHODS: MOD cavities were prepared on human extracted upper third molars. Additional hemispherical cavities (1.6 mm diameter), simulating deep caries, were prepared on axial walls, and they were restored with lining materials including a glass-ionomer, a resin-modified glass-ionomer, and a low viscosity composite for a lined group. Metal inlays were cast with a 12% Au-Ag-Pd alloy and luted with four luting agents including a zinc phosphate(HZ), a conventional glass ionomer (FI), a resin-modified glass ionomer (VL), and an adhesive resin (SB). The specimens were stored in 37 degrees C distilled water for 24 hours and subjected to 5,000 thermo-cycles, and then, dye penetration was evaluated after 24 hr immersion in 2% erythrosine solution. Metal disks were luted to dentin disks, which have the same-sized spherical cavities in the central area, with the same luting agents. Shear bond strengths were evaluated for both lined and non-lined specimens after the same storing and thermo-cycle processes. RESULTS: The inlay specimens luted with SB exhibited no dye penetration, while the specimens luted with HZ presented dye penetration reaching to the pulp chamber. The specimens luted with FI and VL showed moderate dye penetration and the values of dye penetration for the cavity-lined group were significantly less compared to those for the lined group (p<0.05). The shear bond strength of the specimens luted with SB and VL was significantly affected by the lining material. The shear bond strength of the specimens luted with HZ or FI was 0 MPa. CONCLUSIONS: The marginal leakage of a cast restoration is affected by the cavity lining but can be improved by using adhesive resin.

English Abstract↗
PubMed2006

Removal resistance of glass-fiber and metallic cast posts with different lengths.

This study evaluated the strength required to remove glass-fiber and metallic cast posts with different lengths. Sixty endodontically treated canines were included and their roots were embedded in acrylic resin after discarding the crowns. Samples were randomly assigned to 3 groups according to the post length (n = 20): I- 6 mm, II - 8 mm and III- 10 mm. Each group was divided into 2 subgroups based on the post material (n = 10): A- glass fiber or B- metallic cast. Post-space was prepared with Fibrekor Post Kit attached to a parallelometer. In subgroup A, prefabricated glass fiber posts from Fibrekor Post Kit were utilized. In metallic post group (subgroup B), an impression of post space was obtained, followed by casting. All posts were luted with Panavia F cement. A universal testing machine determined the force required to dislodge each post. ANOVA analysis indicated significant differences (P < 0.01) among post length. Tukey test showed that posts with 10 mm-length showed higher resistance on removal than posts with 6 mm-length. Posts with 8 mm-length did not exhibit difference when compared to 6 and 10 mm posts. No significant differences (P > 0.05) were observed between the tested post materials. It was concluded that the type of post did not influence the removal resistance and that posts with 10 mm-length required greater force to be dislodged.

Aluminum↗
PubMed2002

Scanning electron microscopy of vascular corrosion casts and histologic examination of pulmonary microvasculature in dogs with dirofilariosis.

OBJECTIVE: To characterize structural changes in pulmonary vessels of dogs with dirofilariosis. ANIMALS: 8 dogs with dirofilariosis and 2 unaffected control dogs. PROCEDURE: Pulmonary artery pressure was measured in affected dogs, and dogs then were euthanatized. Scanning electron microscopy was used to examine vascular corrosion casts of pulmonary vasculature. Tissue sections of pulmonary vasculature were evaluated by use of histologic examination. RESULTS: Pulmonary artery pressure was higher in dogs with severely affected pulmonary vessels. In tissue sections, dilatation, as well as lesions in the tunica intima and proliferative lesions resulting in constriction or obstruction, were frequently observed in branches of the pulmonary artery. Numerous dilated bronchial arteries were observed around affected pulmonary arteries. Hyperplastic venous sphincters were observed in small pulmonary veins and venules. In corrosion casts, affected pulmonary lobar arteries had dilatation, pruning, abnormal tapering, constriction, and obstruction. In small arteries and arterioles, surface structures representing aneurisms and edema were seen. Bronchial arteries were well developed and extremely dilated, and they formed numerous anastomoses with pulmonary arteries at all levels, from the pulmonary trunk to peripheral vessels. Capillaries in the lungs were dilated with little structural change. Small pulmonary veins and venules had irregular annular constrictions that were caused by hyperplastic smooth muscle cells of venous sphincters. CONCLUSIONS AND CLINICAL RELEVANCE: Scanning electron microscopy of microvascular casts delineated links between the bronchial and pulmonary circulations in dogs with dirofilariosis. Results of scanning electron microscopy provided a structural explanation for the development of pulmonary circulatory disturbances and pulmonary hypertension in dogs affected by dirofilariosis.

Animals↗
PubMed1990

Pecten of the chick eye demonstrated by vascular casts.

Vascular casts demonstrated the capillary network and characteristic features of the inner surface of the capillaries in the chick pecten oculi. Pecten capillaries anastomosed free with each other to form a complicated network of many layers of capillaries. The capillary diameter varied from capillary to capillary, and sometimes ampulla-like features were seen. Numerous pores in the casts of the capillaries corresponded to endothelial processes. Pits represented of nuclear imprints. These scanning electron microscopic findings in vascular casts were not incompatible with those seen by transmission electron microscopy.

Animals↗
PubMedDate not supplied

Casts and crusts of the tympanic membrane.

Casts and crusts of the tympanic membrane were removed from patients with previous otitis media. Casts are formed of adherent keratinocytes in a matrix of dried exudate. Detachment from the drumhead leaves the underlying epidermis intact. Casts are defined as those crusts that have detached spontaneously from the surface of the drum. A mechanism based on epithelial proliferation induced by inflammation within the middle ear, with subsequent keratinocyte retention and thickening, is proposed.

Adolescent↗
PubMedDate not supplied

Particle transport through a hollow canine airway cast by high-frequency oscillatory ventilation.

High-frequency oscillatory ventilation (HFV) of the mammalian respiratory tract can maintain good respiratory ventilation, even with tidal volumes less than half of the anatomic dead space. A steady bidirectional drift is established in airways when the frequency is greater than 2 Hz, resulting in quasi-steady axial streams in the airways. Convective transport from the trachea to peripheral airways takes place in the central core of the bifurcating network of the bronchial tree. It takes place in the opposite direction in the annular regions near the airway walls. In this study, aerosol particle transport was measured in a hollow cast of a canine tracheobronchial tree that extended from the trachea to terminal bronchioles. The 0.5 micron particles, placed in the upper trachea as a bolus, were transported rapidly to the terminal airways of the cast by HFV with tidal volumes of less than one third the volume of the cast. Carrier gases of different kinematic viscosity were used to investigate the fluid dynamics of the transport. Particle transport during HFV was fastest in a gas of high kinematic viscosity (helium), and slowest in a gas of low kinematic viscosity (sulfur hexafluoride). The results are consistent with the application of lubrication theory, improve our understanding of convective processes involved in HFV, and provide new insights into particle penetration in the airways and other aspects of respiratory ventilation.

Aerosols↗
PubMed2004

Bond strength of permanent cements in cementing cast to crown different core build-up materials.

The purpose of this laboratory investigation was to evaluate the bond strength of permanent cement (Duo-cement Kit, Meron, Durelon) to commonly used core build-up materials (President, Dyract AP, Ionofil, Vitremer). Sixty specimens (five of each product) were fabricated as a canine core build- up. Full crown castings were made to fit each core specimen. Full crown castings were cemented to core samples and stored at 37 degrees C and 100% humidity for 10 days. After storage, the bond strength was measured with a Haunsfield tensometer in tensile mode at a crosshead speed of 5 mm/min. Statistical evaluation was performed with univariate analysis of variance (P<0.001). The cement types affected the bond strength of full crown castings to core materials (F: 14.80; P<0.001). The interaction between the cement and core materials was significant (F: 3.69; P<0.01). According to the Duncan's test it was found that the values of Duo-cement were statistically different from the other cements.

Analysis of Variance↗
PubMed1997

Retrospective survey of resin-retained cast-metal palatal veneers for the treatment of anterior palatal tooth wear.

Anterior palatal tooth wear is easily recognized, but its precise pathogenesis remains unknown. Treatment of this condition with cast-alloy palatal veneers used in combination with an adhesive cement is described. Forty-eight patients, aged 11 to 71, were treated with a total of 210 cast metal veneers over a period of 56 months. Twenty-three of the restorations failed, resulting in an overall success rate of 89%. All failures were confined to 13 patients. A glass polyalkenoate cement was less effective than a chemically active resin composite luting agent. Nickel-chromium veneers cemented with activated resin composite recorded a survival probability of 0.74 at 56 months. Adhesive cast-alloy veneers provided a useful method of restoring maxillary anterior teeth affected by acid erosion.

Acrylic Resins↗
PubMed2001

Patterns of variation in a caste-cluster of Dhangars of Maharashtra, India.

We study patterns of variation among the 20 endogamous groups of Dhangars, a caste-cluster from Maharashtra State of India, who are semi-nomadic shepherds and cattle herders. To understand patterns of variation, we subjected the data on fourteen anthropometric measurements of about 2,500 adult males and data on 6 genetic markers, published among 13 of the 20 Dhangar castes, to R-matrix analysis, Harpending and Ward model of regression of heterozygosity on the distance from centroid of the populations, spatial autocorrelation analysis and Mantel statistics of matrix correspondence of the distances--geographic, anthropometric and genetic. Results of multiple regression analysis suggest a high degree of association between allele frequencies and the geographic longitude and latitude; R2 value suggests that about 70% of the variance in RH7 and ACP can be assigned to geographic distribution of groups. In case of anthropometry, this association with body size is found to be even stronger. Results of spatial autocorrelation analysis, as suggested by Moran's (I), are somewhat complementary to those based on multiple regression analysis. Mantel test indicates significant association between anthropometric distances and the geographic distances, not between geographic and genetic distances. The extent of differentiation of Dhangar sub-castes is much higher in anthropometric traits (F(ST) = 0.068) when compared to the genetic markers (F(ST) = 0.023). Yet, the F(ST) value obtained forgenetic markers is larger than the average for the Indian populations, based on similar class of markers. The positioning of the groups in the multivariate space reflects primarily geographic proximity of the groups with reference to anthropometric dimensions while no tangible pattern is evident forgenetic markers. The plot of average heterozygosity of the groups versus their distance from the gene frequency centroid seems to reflect population size variation, rather than group variation in external gene flow.

Adult↗
PubMedDate not supplied

Silicon cast method for quantification of photoablation.

BACKGROUND: Topometry and measurement of photoablation patterns are key questions for keratorefractive photoablation. Ablation rates have been determined previously by either tissue perforation or by micrometry performed on histologic sections. METHODS: A three-dimensional cast of cornea after irradiation was made by using a two-component silicon gel that polymerizes within minutes, thus preserving the corneal topography immediately after photoablation. Polymerization is athermal and nontoxic. The resulting silicon blocks were cut perpendicularly to the anterior surface and measured by calibrated light microscopy. RESULTS: The silicon surface is extremely smooth and the accuracy of the cast is better than 0.25 micron. Reproducibility and long-term stability were demonstrated for casts of photoablated polymethylmethacrylate. Thus, ablation rates and profile, volumetry, and topometry can be determined following laser ablation. The method has been applied for 193-nanometer excimer laser in vitro irradiation of the human cornea. Ablation rates in Bowman's layer and stroma for various radiant energies and distinct pulse numbers were found to be in agreement with published data, and an incubation effect for the first laser pulses could be demonstrated. CONCLUSIONS: The method is nondestructive, accurate, inexpensive, practical, and reduces requirements for laboratory animals.

Animals↗
PubMed2003

[Clinical value of cast post-core porcelain fused to metal crown in restorating residual root and crown of molars].

OBJECTIVE: To investigate the effect of cast post-core porcelain fused to metal crown on the restoration of residual root and crown of molars. METHODS: One hundred and sixty-four residual roots and crowns of molars were treated with root canal therapy and restored by cast core porcelain fused to metal crown. The restoration effect was assessed at the 3rd, 6th, 12th and 24th month. RESULTS: The strength of dental prosthesis retention, marginal fitness, and strength of crowns were satisfactory. The effective rate reached 95.12% during the 2 year follow-up. CONCLUSION: The cast post-core porcelain fused to metal crown is a better method in treating the residual root and crown of molars.

Adult↗
PubMedDate not supplied

A comparison of cast reorientation methods in the anterior and sagittal planes.

Errors in cast reorientation may result in fabrication of a removable partial denture with a different path of insertion than the dentist intended. This study utilized tripoding and scoring to compare the accuracy of a new method of cast reorientation. The results of this study support the accuracy of a new device for recording and reproducing cast orientation on a survey table over conventional methods.

Analysis of Variance↗
PubMedDate not supplied

Long-term survival of repaired amalgams, recemented crowns and gold castings.

This retrospective longitudinal study compared the long-term survival rate of repaired versus replaced amalgam restorations and recemented crowns and gold castings versus non-recemented similar restorations. Private general dental practitioners treated adult subjects at three city practices. No significant survival differences were found between the repaired and replaced amalgams at five years, although the repaired amalgams showed higher failure rates by 10 years (p=0.37). However, there were significantly higher failures by five years for recemented crowns (p<0.001) and recemented gold castings (p=0.01) when compared with the initially cemented restorations. After 10 years, the repaired amalgams had survival rates of approximately 37 +/- 15 (SEr) percent, recemented crowns 28 +/- 15 (SEr) percent and recemented gold castings 42 +/- 17 (SEr) percent.

Adult↗
PubMedDate not supplied

Influence of fatigue loading on the performance of adhesive and nonadhesive luting cements for cast post-and-core buildups in maxillary premolars.

PURPOSE: This study evaluated the influence of fatigue loading on the performance of an adhesive and a nonadhesive cement for cast post-and-core restorations in maxillary premolars. MATERIALS AND METHODS: The adhesive cement used was Panavia 21, a resin-based composite cement, and the nonadhesive cement was PhosphaCem/C, a zinc-oxy-phosphate cement. The coronal sections of single-rooted human maxillary premolars were removed at the level of the proximal CEJ. After endodontic treatment, a cast post and core was prepared for each tooth and cemented into the root canal with either Panavia 21 (n = 8) or PhosphaCem/C (n = 8). Half of the specimens from each cement group were exposed to fatigue loading almost perpendicular to the axial axis; the other half were used as controls. Three parallel transverse root sections were cut from each specimen and used for evaluation of the influence of fatigue loading. For each section, cement integrity was studied by SEM, and retention strength of the cemented post section was determined with a push-out test. RESULTS: For SEM evaluation and the push-out test, Panavia 21 proved significantly better than PhosphaCem/C. However, fatigue loading did not show any effect. CONCLUSION: Under the conditions of this study, fatiguing of cemented cast post-and-core restorations was not decisive as a single test to evaluate the quality of the cement.

Adhesives↗
PubMed2003

[The principles and techniques of cast application].

In this chapter, the chemical properties of the plaster cast and synthetic cast, the techniques of the plaster bandage, and its complications are discussed. The plaster cast is one of the useful materials in the treatment of the orthopedic surgery. Orthopedic surgeon must improve the skill of plaster bandage.

English Abstract↗
PubMed2004

[Clinical evaluation of extensively damaged pulpless anterior teeth restored with direct and indirect cast dowel-core crowns].

OBJECTIVE: To compare the clinical effects of the restoration of residual crowns and roots with direct and indirect cast dowel-core crowns. METHODS: The direct and indirect techniques were applied to fabricate cast dowel-core in 119 teeth of 91 patients. The direct dowel-cores were made by fabricating wax patterns in the prepared teeth in the patients' mouth; and the indirect dowel-cores were fabricated with wax patterns on casts poured by injecting agar impression material into the canal. Then the completed wax patterns were invested. After finishing the dowel-cores, they were cemented in the teeth. The metalceramic crowns were made to restore these teeth. RESULTS: Of the 119 teeth, 71 succeeded and 5 failed in 76 dowel-cores made by the direct method; and only 1 tooth failed among the 43 dowel-cores made by the indirect method. CONCLUSION: The indirect method using agar impression material can be manipulated easily and conveniently with accurate impressions. The dowel-core fits the root canal and the margin has good adaption. The retention is good and this method is practicable.

Adult↗
PubMed2005

Fabrication and data harvesting of casting sample of rat liver blood vessels.

BACKGROUND: The configuration and course of liver blood vessels (LBVs) are involved in the study of pathogenesis of hepatic diseases including liver cirrhosis, tissue engineering of the liver and surgical treatment of diseases of the liver and gallbladder. In the study of vascularization in tissue engineering of the liver in particular, the work we should do is to get the anatomy data of LBVs for computer-aided reconstruction of digital model of LBVs. In doing so, the casting sample of rat liver blood vessels (RLBVs) is fabricated and the data of each section of the sample is harvested. METHODS: Liquid polymer preparation (8%-10%), which was made of chlorinated poly vinyl chloride (CPVC) as a solute, acetone as solvent and pigment, was injected into the RLBVs of 40 rats. Once acetone evaporated, the preparation solidified. When the cells and connective tissue were dissolved by hydrochloric acid, a casting sample of RLBV was left. The sample was embedded in paraffin and cut into sections. The data of each section of RLBVs was collected by digital camera. RESULTS: In 36 rats, the casting sample of RLBVs was made successfully by this method. The diameter of the hepatic arteries varied from 0.8 to 0.2 mm, the portal veins from 2.0 to 0.1 mm, and the hepatic veins from 2.2 to 0.2 mm. In each rat, about 150 photographs of the sections of RLBVs were taken. CONCLUSION: The method described above is feasible for getting experimental data for computer-aided reconstruction of the digital model of RLBVs.

Acetone↗