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At least 1,243 records · Page 69Linked to original sources
PubMed1990

[Effects of fluoride releasing resin on the denture base on bovine enamel].

The first aim of this study was to investigate the amount of fluoride released from fluoride releasing resin for the denture base (F-resin). The second aim of this study was to determine the uptake of fluoride with bovine enamel, which was immersed in distilled water for 90 days in contact with F-resin. The results obtained were as follows: 1) The amount of fluoride released from F-resin decreased gradually. From the 10th day of immersion, the amount of fluoride released was almost constant. The fluoride could be detected on the 90th day. 2) The uptake of fluoride from F-resin was great both on the surface and the subsurface enamel. 3) The uptake of fluoride from F-resin was almost proportional to the immersing time.

Animals↗
PubMed1990

[Study on visible-light curing soft resins consisting of fluoropolymers. (3) Application of low molecular weight fluoropolymer].

New experimental visible-light cured soft resins were prepared by combining a low molecular weight vinylidene fluoride/hexafluoropropylene copolymer (2-6 FL), or vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymer (2-4-6 FL) with 2,2,3,3-tetrafluoropropyl alpha-fluoroacrylate (4 FFA), or 2,2,3,3,4,4,5,5-octafluoropentyl alpha-fluoroacrylate (8 FFA). Some properties of the resins prepared were measured to determine whether they would be candidate material for a soft denture liner. Water contact angle was 90-92 degrees with 4 FFA, and 90-94 degrees with 8 FFA. The resins combined with 2-4-6 FL were sufficiently soft: 42-46 (JIS A hardness) in 4 FFA, and 33-39 in 8 FFA. Generally the hardness decreased by 5-10 with the use of a low molecular weight of fluoropolymer. Water sorption after 10 weeks was 0.8-1.2% in 2-6 FL/4 FFA, 1.3-1.7% in 2-6 FL/8 FFA, about 1% in 2-4-6 FL/4 FFA, and about 2% in 2-4-6 FL and 8 FFA. Solubility was 0.4-0.5% in 2-6 FL/4 FFA, 0.3-0.4% in 2-4-6 FL/4 FFA, 1.5-1.9% in 2-6 FL/8 FFA, and 1.1-1.5% in 2-4-6 FL/8 FFA. Amount of residual monomer was very low, and the maximum was 0.1%. Tensile strength of the resins was reduced to 40-70% of that of the similar resins obtained in the previous study. Thus softer resins could be prepared by using lower molecular weight fluoropolymers.

Denture Liners↗
PubMed1990

Color stability of composite resins.

The color stability of seven visible light-cured and three chemically-cured composite resins was investigated while being subjected to UV light irradiation and storage in an aqueous environment at elevated temperatures. Color shift was evaluated visually and by colorimetric measurements. Significant correlation was found between visual scoring and colorimetric readings. When subjected to UV light, a wide deviation in color change existed from brand to brand in photocured composite resins. The color shift of chemically-cured composite resins was less than but fell within the range of photocured composite resins. When stored in water at elevated temperatures, photocured resins exhibited better color stability than the chemically-cured composite resins.

Chemical Phenomena↗
PubMedDate not supplied

A high density culture of hepatocytes using a reticulated polyvinyl formol resin.

To enable high density culture of hepatocytes to be used as a hybrid artificial liver support or bioreactor system, collagen coated reticulated polyvinyl formal (PVF) resin (a filter material with a porosity of more than 80%) was used for the primary culture of hepatocytes. Stationary and perfusion culture experiments using PVF resin and monolayer culture were performed as control experiments. Due to the porous structure of the substrate material, hepatocytes were able to penetrate the reticulated pores of the PVF resin, and adhere to and spread on its surface. The densities of hepatocytes attained with PVF were about 10 times as high as those in the monolayer culture using conventional collagen coated Petri dishes. Hepatocytes immobilized in the PVF resin showed viability, as assessed by glutamic pyruvic transaminase (GPT) activity in the medium. Perfusion culture with PVF resin showed stable, high level metabolism, ammonium removal, and urea secretion comparable to the monolayer culture. It is concluded that perfusion culture with PVF resin is useful in attaining a high density culture of hepatocytes.

Animals↗
PubMed1989

[Study on retention of veneering materials to the facing crown made of hard-type resin. Application etching to Ni-Cr alloys].

In order to enhance adhesiveness between the resin and the metal in the facing crown made of hard-type resin, the bead application method has been widely utilized. A short-coming of this method is that the metal part of the facing must be made thicker for bead application. If, however, a retention is made beneath the surface of the metal part, the facing metal can be made thinner. The author studied the adhesiveness of metal to resin by producing pitting corrosion on the surface of four different kinds of Ni-Cr alloys, etching the surface with strong acid under various conditions, and compared the adhesiveness and failure conditions with those of the beaded specimens. The results were as follows: 1) The degree of corrosion of the surface of specimens was positively correlated with the duration of etching. However, the degree of corrosion differed depending on the kinds of etching solutions and specimen alloys. 2) In terms of adhesiveness, some of the etching groups were stronger than the beaded groups and some were weaker, depending on the kinds of alloys and etching conditions. 3) Condition of failure at the joint surface: in the beaded groups cohesive failure was the most prevalent type. In the etching groups, compound failure was the most prevalent. There was a positive correlation between adhesive strength and the amount of residual resin: the more residual resin, the greater the adhesive strength. 1) Electron microscopic observations: on the surface of specimens of the etching groups pitted roughness was observed, and the resin material was tightly attached to the metal surface. However, reciprocal diffusion of the elements from both materials was not indicated, nor was there any evidence of chemical bonding.

Acid Etching, Dental↗
PubMed1989

[Epoxy resin as a cause of contact allergic eczema].

Epoxy resin-containing products of the plastic industry are increasingly employed. We retrospectively studied the incidence and course of epoxy resin contact dermatitis in 2265 patients in whom contact dermatitis was confirmed by patch testing. A positive patch test for epoxy resin was present in 31 patients (1.4%). Exposure to epoxy resin as the cause of contact dermatitis was 'certain' in 10, 'very likely' in 9, 'possible' in 4 and 'unclear' in 8 patients. Exposure to epoxy resin was related to occupational (55%) and leisure time activities (13%). In 48% patch tests were positive for multiple test allergens. Hands (56%), arms (38%) and face (38%) were mainly affected. Re-examination of 26 of 31 patients showed that a favourable course depended on identification of the cause of the exposure to epoxy resin, avoidance of further contact and absence of sensitization to multiple allergens.

Cross Reactions↗
PubMed1989

[Basic studies on hard direct reline resins. Part 1. Adhesive strength].

Direct relining methods has come to occupy an important position in removable denture prosthodontics. The purpose of this study was to investigate the effect of various experimental conditions on the adhesive strength of hard direct reline resins to denture base resin. The experimental conditions were as follows: 1) immersion time of denture base resin before relining, 2) amount of load at relining, 3) roughness of adhesive surface, 4) immersion time of relined resin. The following results were obtained: 1. The adhesive strength of Rebaron was the highest, followed by that of TRIAD and KOOLiner. 2. The immersion times of denture base resin did not appreciably affect the adhesive strength. 3. With the rougher adhesive surface, Rebaron and KOOLiner showed a tendency to increase adhesive strength. 4. The adhesive strength was not appreciably affected by load. 5. We did not find a definitive correlation between adhesive strength and immersion times of relined resin.

Adhesiveness↗
PubMed1988

Bonding of restorative resins to enamel.

The bond between restorative resin and enamel may be likened to a chain with a series of links. The potentially weakest link is the interface between the resin and the tissue. This link is established by the clinician and is considered to be technique sensitive. An understanding of the steps in clinical method provide a rationale and an aim for each step. A thorough dental prophylaxis to remove deposits, including calculus from enamel, is important in allowing the acidic conditioning agent, namely phosphoric acid, to exert its optimal effect. Conditioning of the enamel raises its surface energy, creates increased surface area and enhances tissue porosity in the outermost enamel. These conditions are achieved through careful isolation of the teeth and thorough washing to remove the acid and reaction products. A dry field is also of paramount importance in obtaining the micromechanical retention of the resin within the enhanced tissue micropores. The polymerized resin within the tissue serves to retain the bulk of resin located upon the enamel surface. The method is a clinically conservative, non-traumatic, biocompatible means by which resins, polymerizable under oral conditions, can be bonded durably to enamel.

Dental Bonding↗
PubMed1979

The bending strength of acrylic resin samples repaired under pressure.

The bending strength of heat-cured resin samples was found to be 49% higher than that of autopolymerizing resin samples cured under room conditions. Curing the latter resin in a pressure vessel at 32psi and 30 degrees C increased its strength by 4.5%. For this reason and because a less porous material is obtained, pressure-curing may be employed with advantage for the preparation of various appliances from S.C. resin. The effect of pressure-curing in increasing the strength of the repaired samples was not significant. It would also appear that pressure affects the porosity of small quantities of repair material less than when appliances are made from S.C. resins only. The increase in strength achieved by pressure-curing repairs, in which only small quantities of S.C. resin are used, is therefore questionable.

Acrylic Resins↗
PubMed1985

[New apparatus for artificial liver support: PAT resin--removal of protein-bound substances and its effect on hepatic failure in animals].

Hemoperfusion using several materials such as activated charcoal is often performed to treat the patients with hepatic failure. Polyamine triglycidylisocyanulate (PAT) resin is a newly developed artificial liver support material to adsorb protein-bound substances. In this study, the effect of PAT resin on the removal of these toxic protein-bound substances was examined and following results were obtained. PAT resin adsorbed protein-bound substances selectively in vitro. Its adsorbability was superior to those of the other conventional adsorbents such as cellulose-coated charcoal, XAD-4 and XAD-7. Serum bilirubin levels were decreased by 44% in jaundiced dogs and 45% in jaundiced rabbits after 120 minutes hemoperfusion with PAT resin. Leucocyte and thrombocyte count also fell during hemoperfusion. The fall of these blood cell counts, however, was recovered by prostaglandin D2. The survival time of dogs with ischemic hepatic failure was prolonged by hemoperfusion using PAT resin. The mean survival times were 17.6 hrs in the PAT perfusion group and 10.9 hrs in the control group. The difference of survival time between these two groups was statistically significant. (p less than 0.05). These results in animals suggest that PAT resin will be clinically useful in the therapy of hepatic failure or hyperbilirubinemia.

Animals↗
PubMed1983

[In vitro studies on the adsorption of various resins of the Wofatit type for drugs].

The capacities of the resins Wofatit Y 29, Y 55 and Y 56 (VEB Chemiekombinat Bitterfeld) to adsorb various medicaments were compared with that of the resin XAD-4. Methaquelone, diazepam, krotylbarbital, promazine phosphate and ethyloxamine were used as test substances. The resin Y 56 proved to have an adsorption capacity similar to that of XAD-4 (e.g. maximum saturation for methaquelone 98%, half-maximum saturation at 7 minutes). In further tests on various batches of this resin the best results were given by the resin Y 56/7. Adsorption was quite clearly shown to be dependent on concentration. At a blood-flow of 100 ml/min clearance values of 34.5 ml/min for krotylbarbitol and 22.1 ml/min for methaquelone were calculated. According to these findings the resin Y 56/7 is suitable for further testing in a haemoperfusion system with a view to clinical use.

Barbiturates↗
PubMed1978

The use of an in vitro haemoperfusion circuit to evaluate the blood compatibility of albumin-coated Amberlite XAD-7 resin.

We have developed an in vitro haemoperfusion circuit, which closely simulates the conditions encountered in a clinical haemoperfusion, for testing the blood compatibility of new adsorbent materials. Fresh heparinised human blood is perfused for 2 hours over two model columns arranged in parallel closed circuits. The present study was performed to investigate the blood compatibility of human serum albumin-coated Amberlite XAD-7 resin. Mean platelet losses over 2 hours were greater following perfusion of the uncoated resin (44 +/- SE 5.6%) than the albumin-coated resin (17 +/- SE 2.2%) (p less than 0.01). Mean white cell losses were similar (55%) for both resins. No rises in Swank screen filtration pressure, which detects the presence of cellular aggregates in blood, were observed. Coating of XAD-7 resin with HSA therefore improves its blood compatibility with respect to platelet losses and we thus intend to use this preparation in a clinical trial of resin haemoperfusion in fulminant hepatic failure.

Acrylic Resins↗
PubMed1980

[Studies on the dynamic durability of dental restorative materials. (Part 2) Properties for the repeated impact compressive load ot composite resins (author's transl)].

Based on the fracture energy form the compression test of composite resins under the repeated impact loads in compression after stored for a period in water at 37 degrees C, the dynamic durability of commercially used composite resins was evaluated. The results obtained were summarized as follows. (1) The fracture energy of composite resins under the repeated impact compressive loads after stored in water at 37 degrees C is clearly lower than the initial fracture energy. Particularly the decrement of the initial fracture energy for Concise, Epolite 100 and Superlux after stored for 30 days in water at 37 degrees C is influenced considerably both by the physicochemical degradation caused by water and the mechanical deterioration caused by the repeated impact compressive loads, but Clearfil is superior to the mechanical deterioration. (2) In each composite resins, there is a close correlation between fracture energy and compressive strain. In composite resins without Superlux, also a correlation is in fracture energy and compressive strength. (3) In clearfil, concise and Epolite 100, the morphology of fracture in compression test of composite resins which are subjected to and are subjected to the repeated impact loads in compression is classified in a mode of shear fracture, but in Superlux, a mode of crack fracture.

Composite Resins↗
PubMed1995

The limitations of resin-bonded restorations.

The ability to resin-bond rather than relying on mechanical retention and the use of cements indirect restorations has had a substantial impact on restorative dentistry. While resin-bonding offers many advantages, notably a reduction in the removal of sound tooth tissue during preparation, resin bonds suffer certain limitations. These limitations, including technique sensitivity, susceptibility to marginal deterioration and relatively limited life expectancy, are discussed in this paper together with considerations of the clinical performance and modes of failure of resin-bonded restorations in clinical service. It is concluded that resin-bonding will become recognised as a major development in dentistry but there remains considerable scope for further development of the materials and techniques for resin-bonded restorations.

Composite Resins↗
PubMed1994

Negatively charged resins stimulate bone formation in subperiosteal sites in rats. The effect of age.

The osteogenic response to subperiosteal injection of negatively charged ion exchange resins was compared in the tibiae of one-month and 16- to 22-month-old rats. The resins were administered either in the form of beads (CM Sephadex) or as particles (CM cellulose, carboxymethylcellulose), and the animals were killed at two weeks and at one month after injection. Histologically, the resins did not produce an inflammatory response. Periosteal bone formation was observed wherever resin was in contact with bone, and in the resin bed the connective tissues that invested the charged materials ossified within the first month. Marrow spaces commonly formed where periosteal growth was most rapid. The osteogenic effect was independent of resin conformation, and it was more pronounced in the younger rats.

Aging↗
PubMedDate not supplied

Effect of light-tip distance on polymerization of resin composite.

The inability to place a light tip in close approximation to a resin restoration may affect the resultant polymerization and clinical durability of the restoration. This research measured light intensity at the surface of a resin composite, as well as 2 mm within its bulk, as the tip-to-resin distance is moved from 0 to 10 mm. The polymerization of the resin composite at both locations was measured for the various tip distances using exposure durations of 10, 20, 40, and 60 seconds. Light intensity did not decrease with the inverse square of the tip distance. The polymerization on the surface was greatly dependent upon the duration of exposure. The extent of polymerization 2 mm below the surface was still dependent primarily upon exposure duration, but intensity had a significant affect. For exposure durations of 10, 20, and 40 seconds, a tip distance greater than 4 mm demonstrated a significant decrease in resin polymerization 2 mm below the resin composite surface.

Composite Resins↗
PubMedDate not supplied

11-year follow-up study of resin-bonded fixed partial dentures.

The clinical performance of 325 resin-bonded fixed partial dentures (RBFPD) placed between 1984 and 1995 was reviewed. The primary indications of the 264 patients treated were trauma and aplasia. Two hundred eighty-three of the resin-bonded fixed partial dentures were primary restorations, and 42 of the restorations were secondary and tertiary after the loss of the primary resin-bonded fixed partial denture. Including the rebonded restorations, the survival rate calculated using the Kaplan-Meier method was 76% after 5 years and 60% after 10 years. Analysis of the data showed that casting alloy, pretreatment of the bonding surfaces, luting agent, and mobility of the abutment teeth were decisive prognostic factors for success. Base metal alloys, silicoating, mesh retention, and immobile abutments were positive factors. In contrast to other reports in the literature, retentive abutment preparation did not result in a higher survival rate than unprepared abutments. Small restorations in the bonding area did not affect the survival. No differences in survival rate were found for resin-bonded fixed partial dentures in the maxillae or mandible, or in the anterior and posterior regions. Multiunit resin-bonded fixed partial dentures had a smaller probability of survival than three-unit resin-bonded fixed partial dentures. Carious lesions were found on 4% of the abutment teeth.

Adult↗
PubMed1997

Bond strengths of the adhesive resin-amalgam interface.

PURPOSE: To evaluate the tensile and shear bond strengths of eight adhesives and two amalgams (spherical and lathe cut). MATERIALS AND METHODS: Two high-copper amalgams (Tytin, spherical; and ANA-2000, dispersed phase) and seven adhesives (Panavia EX, C&B Metabond, Chameleon Metal Resin Cement, All-Bond 2, All-Bond C&B, Photo-Bond and Imperva Dual) were evaluated. An epoxy resin (Stycast 1266) was included as a control for comparison because it was an adhesive material of similar viscosity but different chemistry from the dental adhesives. The aluminum surfaces were sandblasted with 50 microns aluminum oxide just prior to coating with adhesive resins. The testing area was defined with a 4 mm circular adhesive Mylar mask. All adhesives were mixed and handled according to manufacturers' instructions. Freshly mixed amalgam was condensed into the test cavity and onto the surface immediately after coating with adhesive. After 24 hours storage, the bond strengths were determined in an Instron testing machine at a crosshead speed of 2 mm/minute. The debonded surfaces were examined in an optical microscope for site of failure. The few samples which showed failure at the aluminum-resin interface were not included in the study. Selected debonded surfaces were examined by SEM. A 2-way ANOVA (General Levin Models-GLM) was used to analyze the data from both the tensile and shear bond strength tests. GLM was used instead of standard ANOVA because of the unbalanced design. The lack of balance occurred because some of the bonding resin/amalgam groups had different sample numbers. RESULTS: A wide variation in bond strengths was obtained with adhesive resin cements and not all appeared suitable for adhesive amalgam restorations. Panavia EX, C&B Metabond, Chameleon Metal Resin Cement and All-Bond C&B showed the best potential for amalgam bonding, with shear and tensile bond strengths greater than 8 MPa. Viscous, filled versions of adhesives appeared to be more effective. Choice of amalgam appeared to be less important than choice of adhesive.

Analysis of Variance↗