Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SILICATE CEMENT”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources
PubMed1983

Acid resistance of enamel exposed to fluoride-containing orthodontic cements.

In a previous study enamel fluoride uptake from fluoride-containing orthodontic cements was evaluated after a 21-day period. The enamel fluoride uptake from a zinc phosphate cement (A), a zinc phosphate cement containing 5 per cent stannous fluoride by weight (B), and a silicophosphate cement (C) was compared. The results indicated that there was a net loss of fluoride from enamel beneath the orthodontic bands cemented with A while the enamel beneath B and C acquired significant amounts of fluoride. The purpose of the present study was to evaluate enamel fluoride uptake after 12 weeks and the effect of the fluoride uptake or loss by the enamel on acid resistance. Five teeth each had bands cemented with cements A, B and C, respectively, and were individually suspended in synthetic saliva for 12 weeks at 37 degrees C. Following this period the bands were removed, the cements were carefully cleaned off the teeth, and the crowns of the teeth were individually suspended in a lactic acid buffer at pH 4 for 4 weeks. Each tooth crown was then sectioned longitudinally and examined microradiographically to study the degree of enamel demineralization. Characteristic subsurface enamel carieslike lesions were noted on all the specimens studied. The carieslike lesions in the enamel exposed to the fluoride-containing cements were considerably reduced. The enamel which had acquired fluoride from the fluoride-containing cements was apparently more resistant to artificial caries attack.

Acids↗
PubMed2006

Effect of die spacer thickness on shear bond strength of porcelain laminate veneers.

STATEMENT OF PROBLEM: The application of die spacer may affect the shear bond strength (SBS) of porcelain laminate veneer (PLV). However, there is no standard for the amount of die spacer necessary for the fabrication of PLV restorations. PURPOSE: The purpose of this study was to evaluate the SBS differences between enamel and a feldspathic PLV as a function of die spacer thickness. MATERIAL AND METHODS: Eighty rectangular (5 x 3 x 1 mm) PLV (Super Porcelain EX-3) specimens were made using stone blocks on which die spacer (Nice Fit) was applied in different thicknesses (0, 2, 4, or 6 coats) (n = 20). Before bonding, all PLV specimens were pretreated with airborne-particle abrasion (1-, 2-, 3-, or 4-bar pressure; 10 sec/10-mm distance or 5 sec/20-mm distance) and cleaned with an ultrasonic cleanser. A vertically flat surface on the labial enamel of 80 freshly extracted sound teeth was prepared with a low-speed diamond-coated saw. The PLV specimens were bonded to the etched enamel specimens using a composite resin cement (RelyX Veneer). Forty enamel-ceramic specimens (Group NTc) were maintained in deionized water at room temperature for 1 week after cementation, and the other 40 specimens (Group Tc) were subjected to thermal cycling treatment (2500 cycles, 5 degrees C to 60 degrees C, 15-second dwell time). The SBS measurement was performed with a universal testing machine. The results were compared with a 2-way analysis of variance (ANOVA), and mean values were compared with Fisher's Protected Least Significant Difference (PLSD) intervals (alpha = .05). RESULTS: For Group NTc specimens, the SBS values (MPa) were 8.7 +/- 2.6 (no coat), 12.6 +/- 4.8 (2 coats), 10.7 +/- 2.9 (4 coats), and 9.6 +/- 2.8 (6 coats). For Group Tc specimens, the SBS values were 4.1 +/- 2.0 (no coat), 7.1 +/- 3.4 (2 coats), 6.8 +/- 2.1 (4 coats), and 6.1 +/- 2.4 (6 coats). Two-way ANOVA showed that the SBS was influenced by the thermal cycling and the number of coats, but there was no significant interaction between the 2 variables. The Fisher's PLSD interval for the SBS for comparisons among the number of coats was 0.95. The group with 2 coats of die spacer showed higher SBS values than the group with no coat, whereas groups with more than 2 coats of die spacer resulted in similar SBS values when compared to each other. The thermal cycling treatment resulted in a significant decrease of the SBS. Group Tc showed a trend similar to Group NTc. CONCLUSION: Within the limitations of this study it was found that the appropriate application of die spacer exerts a favorable influence on the SBS of composite-bonded PLV. The 2-coat application of die spacer provides suitable space to accommodate the cement thickness.

Acid Etching, Dental↗
PubMed2006

Advances in cement solidification technology for waste radioactive ion exchange resins: a review.

Treatment and disposal of waste radioactive ion exchange resins is one of the most urgent problems for nuclear industries in China. Cement solidification technology has many advantages, such as requiring simple equipment, easy scaling-up, low working temperature, no trouble of gas cleaning and low cost. It is a suitable technology for treatment of waste radioactive resins, and has been widely used. The new developments and theoretical basis of cement solidification of radioactive resins were introduced in this paper. The cement solidification technology suitable for China and the questions needed to solve were also discussed.

Hot Temperature↗
PubMedDate not supplied

A two-year clinical evaluation of TPH for restoration of Class II carious lesions in permanent teeth.

To evaluate the clinical suitability of a barium silicate-filled composite (TPH) for restoration of posterior teeth, 50 Class II restorations were restored in 36 patients. Restorations included 22 molars and 32 premolars. Cavity preparations were protected with calcium hydroxide or a resin-modified glass ionomer cement, or both. Enamel was etched for 30 seconds with 37 percent H3PO4. All dentin surfaces were treated with a dentin bonding system that was placed, cured, and restored in 2 microns increments. The restorations were finished using diamond burs, polishing points, and paste. Evaluation periods were at zero (50 restorations), 6 months (35 restorations), 1 year (31 restorations), and 2 years (29 restorations), using the USPHS System and M-L indirect scale. At zero time, 50 restorations were scored "a" in all categories by using two independent evaluators. After 6 months, 35 restorations were graded with one "a" in postoperative sensitivity. After 1 year, 31 restorations were evaluated with one additional "b" for marginal integrity. After 2 years, 2 additional "b" for marginal integrity and 1 "b" for surface staining were noted. No "c" was observed in any categories throughout this study. Wear analysis revealed, on average, 2 microns of wear after 6 months, 7.8 microns of wear after one year, and 10.3 microns of wear after 2 years.

Adult↗
PubMed1987

Thermal diffusivity of glass-ionomer cements.

Thermal diffusivity, a property related to the thermal insulative efficiency of a material, was measured in nine glass-ionomer cements and compared with results from a silicate and a polycarboxylate cement. Each cement was mixed at various powder-liquid ratios (P/L) and moulded into a rectangular prism of approximate dimensions 2 cm cube with a thermocouple embedded in it. The prism was immersed in a constant-temperature bath at 1 degree C, and the fall in temperature was observed over a period of three min. Except for the initial and later stages, the plot of the logarithmic difference between external and internal temperatures of each block of cement against time showed a straight line in accord with theoretical prediction. From the slope, the thermal diffusivity of the material was calculated. The values for the silicate, polycarboxylate, and glass-ionomer-metal (cermet) showed a marked rise with increasing P/L, whereas at higher P/L, glass ionomer cements showed gradual change, with values being only slightly higher than the thermal diffusivity of dentin. Glass-ionomer cements are good thermal insulators over a wide range of P/L, and close agreement between experimental and theoretical data shows that glass-ionomer cements are homogenous isotropic materials.

Dental Cements↗
PubMed2004

Wear and mechanical properties of nano-silica-fused whisker composites.

Resin composites must be improved if they are to overcome the high failure rates in large stress-bearing posterior restorations. This study aimed to improve wear resistance via nano-silica-fused whiskers. It was hypothesized that nano-silica-fused whiskers would significantly improve composite mechanical properties and wear resistance. Nano-silicas were fused onto whiskers and incorporated into a resin at mass fractions of 0%-74%. Fracture toughness (mean +/- SD; n = 6) was 2.92 +/- 0.14 MPa.m(1/2) for whisker composite with 74% fillers, higher than 1.13 +/- 0.19 MPa.m(1/2) for a prosthetic control, and 0.95 +/- 0.11 MPa.m(1/2) for an inlay/onlay control (Tukey's at 0.95). A whisker composite with 74% fillers had a wear depth of 77.7 +/- 6.9 mum, less than 118.0 +/- 23.8 microm of an inlay/onlay control, and 172.5 +/- 15.4 microm of a prosthetic control (p < 0.05). Linear correlations were established between wear and hardness, modulus, strength, and toughness, with R = 0.95-0.97. Novel nano-silica-fused whisker composites possessed high toughness and wear resistance with smooth worn surfaces, and may be useful in large stress-bearing restorations.

Bisphenol A-Glycidyl Methacrylate↗
PubMedDate not supplied

Correlation between microleakage and cement thickness in three Class II inlay ceramic systems.

The objectives of this study include comparing the cement thickness and microleakage of Class II ceramic inlays built with three ceramic systems and verifying whether there was a correlation between those two variables. The ceramic systems used include: 1) Heat-pressed (IPS-Empress); 2) CAD-CAM (CEREC 2) and 3) Sintered (Colorlogic). Standardized MOD Class II inlay cavities with one proximal box extending below and the other extending above the cement-enamel junction (CEJ) were prepared in 30 extracted human molars and randomly assigned to three groups. The ceramic inlays were constructed according to manufacturer's instructions and cemented using a dual-cure resin cement (Variolink II). All teeth were mechanically cycled (100,000 cycles, 78N) and thermocycled (700 cycles, 5 degrees C-55 degrees C). After immersion in silver nitrate, the inlays were sectioned mesial-distally and evaluated with an optical microscope (40x). The cement thickness obtained by the Colorlogic system (enamel: 113 +/- 25 microm; dentin: 118 +/- 23 microm) was significantly higher than that obtained by CEREC (enamel: 78 +/- 14 microm; dentin: 87 +/- 13 microm) and Empress (enamel: 65 +/- 15 microm; dentin: 89 +/- 14 microm). Regarding dye penetration, there was no statistical difference among the three ceramic systems in enamel. At the dentin margins, the Colorlogic system resulted in a significantly higher penetration depth compared to CEREC and Empress, which had similar average values. No correlation was found between cement thickness and microleakage either in enamel or dentin for any of the ceramic systems.

Aluminum Silicates↗
PubMed1995

[Lung cancer mortality in Casale Monferrato (Italy) and attributable risk to occupations in the asbestos-cement production].

The study presents mortality rates for lung cancer in the town of Casale Monferrato, where the largest Italian asbestos cement-plant was located. Cases of lung cancer dying in 1989-94 were exhaustively searched for in the register of deaths. Each case of lung cancer has been identified as ever or never employed in the factory with a linkage to the rosters of employees in the plant. Women were also identified as ever or never married to an asbestos-cement worker. The number of person-years at risk for asbestos cement workers and their wives was measured on the basis of the most recent follow-up. Mortality rates were computed separately for those exposed (workers and wives of workers) and for those with no evidence of exposure. Mortality rates for non-exposed were similar to rates in Piedmont (the region where Casale is located). The relative risk (ever exposed vs. never exposed) was 2.8 among men and 2.1 among women. Attributable risk among the exposed was 64.5% for men and 53.1% for women while among the general population it was 18.1% for men and 13.2% for women. The study confirms the dramatic effect of occupational asbestos exposure in Casale Monferrato but does not suggest an increase in lung cancer mortality among people with no occupational activity in the asbestos-cement production.

Adult↗
PubMed1991

Preventive dental materials: sustained delivery of fluoride and other therapeutic agents.

In the 1940's, it was observed that silicate restorative cements were seldom associated with secondary caries. Fissure sealants, designed to protect caries-prone surfaces, appeared in the 1960's. The 1970's and 1980's have seen an increasing emphasis on the use of dental materials for preventive purposes. Glass ionomers, the modern version of silicates, release fluoride and have been available for some time. Polymeric materials that release various therapeutic agents are currently under development for use in topical anesthetic, endodontic, prosthodontic, and periodontal applications. An attachable membrane-reservoir device for oral fluoride delivery will soon be available for general clinical use. Several fluoride-releasing filling and adhesive resins have recently been marketed. These materials are the leading edge of a new class of preventive materials that serve as controlled-release and/or site-specific sources of therapeutic agents. This trend is expected to continue, and the near future should see the introduction of additional oral sustained-delivery systems for use in periodontal and other applications.

Biocompatible Materials↗
PubMed1997

[Clinical investigations and cytological examinations of the nose in subject exposed to cement dust].

Mucous membranes of the nose of 90 persons exposed to cement dust were investigated clinically and cytologically. We found atrophic changes in 37.8% persons and hypertrophic changes in 13.3%. In a halt of the investigated persons abnormality in epithelium forms in cytological examination was demonstrated. The connection of inflammatory changes and pathological forms of the epithelium has been documented. The correlation between presentation of cement deposits and inflammatory infiltrations and atrophic and hypertrophic changes was confirmed.

Adult↗
PubMed1980

Biological implications of dental materials.

Testing of the biologic effects of dental materials has lagged far behind the characterization of their mechanical and physical properties. Various biologic-type tests, whether in vitro or in vivo, have often produced conflicting or confusing data. The objective of this article was to bring together the results of various investigations to form guidelines for the safest use of dental materials. Since many interactions between dental materials and living tissue have not been definitively established, a conservative approach was taken. The clinician who heeds the data summarized for the dental materials presented here will have the greatest probability of obtaining a benign chemical response of soft and hard tissues.

Biocompatible Materials↗
PubMed2002

Bacterial microleakage and pulp inflammation associated with various restorative materials.

OBJECTIVES: Many restorative materials are claimed to be successful in preventing bacterial microleakage and minimizing pulp inflammation. However, information regarding the in vivo performance of materials in comparison with each other is limited. The aim of this study was to evaluate and compare the pulp response of nine restorative materials when placed in non-exposed monkey cavities. METHODS: 279 standardized non-exposed Class V cavities, were prepared into buccal dentin. Cavities were restored with a number of materials in the following categories: Zinc oxide eugenol (ZnOE), Calcium hydroxide [Ca(OH)(2)], zinc phosphate (ZP), Resin-modified glass ionomer (RMGI), Composite resin (CR), Bonded amalgam (BA), Gutta-percha (GP), Compomer and Silicate. Pulp tissues were collected and evaluated at short, intermediate and long-term intervals according to ISO guidelines; employing histomorphometric analysis, Spearman's rho and ANOVA statistics. Pulp responses were categorized according to FDI, ISO and ADA standards. Bacteria were detected using McKay stains. RESULTS: Pulp inflammation was found to be correlated to bacterial microleakage around the restoration (p < or =0.0001). The frequency of bacterial microleakage was found to vary between restorative materials (p < or =0.0001). In rank order of preventing bacterial microleakage from best to the worst; RMGI (100%), BA (88%), ZnOE (86%), CR (80%), GP (64%), Ca(OH)(2) (58%), compomer (42%), silicate (36%) and ZP (0%). SIGNIFICANCE: The most effective restorative materials to prevent bacterial microleakage and pulp injury from inflammatory activity were RMGI, BA, ZnOE and CR restorations.

Analysis of Variance↗