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At least 163 records · Page 9Linked to original sources
PubMed2005

Light shielding effect of overlaying resin composite on the photopolymerization cure kinetics of a resin composite and a dentin adhesive.

OBJECTIVES: The purpose of this study was to simultaneously determine the impact of exposure times and incremental resin composite overlaying thickness on the cure kinetics of a light activated composite and a dentin adhesive at selected depths of a simulated restoration. METHODS: Levels and kinetics of polymerization of a light activated resin composite (Z250, 3M-ESPE) and dentin adhesive (Excite, Ivoclar) cured with a halogen light unit (Demetron, Kerr, USA) operating at low/medium intensity (500 mW/cm2) for different exposure durations (20 and 60 s) were measured at selected depths (0.3, 0.6 and 1mm) using a modified calorimetric analyzer (DSC 25, METLLER-TOLEDO). RESULTS: Final polymerization levels of materials up to 1mm through the composite are not significantly different while the light shielding effect of incremental resin composite overlaying progressively reduces their reaction rates. SIGNIFICANCE: Prolonged irradiation time at low/medium energies is effective for proper conversion of a resin composite and dentin adhesive; 60 s irradiation time provides the maximum obtainable conversion through the dental resin composite for thicknesses up to 1mm.

Calorimetry, Differential Scanning↗
PubMed2003

Comparison between mass transfer properties of weak-anion-exchange resins with graft-functionalized polymer layers and traditional ungrafted resins.

Glycidylmethacrylate was grafted to Toyopearl HW-65M and subsequently modified with diethylamine to obtain a weak anion exchanger. The degree of grafting was varied from 11 to 50%. The binding capacity for bovine serum albumin was 11 mg/ml for the lowest degree of grafting and 97 mg/ml for the highest degree of grafting. The maximum binding capacity was observed at 27% degree of grafting. The mass transfer properties of the grafted resins and an ungrafted resin(Toyopearl DEAE 650M) were investigated assuming rectangular isotherms. Simple models for reaction kinetics, pore- and surface diffusion and film diffusion were used to describe the concentration-time data in batch mode. The data were best fitted by a pore diffusion model. The estimated pore diffusion coefficients (D(P)) for bovine serum albumin were fitted by a polynome to the degree of grafting with an maximum value at 27% of D(P) = 1.95-10(-11) m2/s. Compared to published data of other ungrafted resins and to the molecular diffusion coefficient of bovine serum albumin in free solution of D(P) = 5.6 10(-11) m2/s, the diffusion in grafted layers seems to be accelerated. The breakthrough curves for columns packed with various resins showed a decrease in sharpness with increasing degree of grafting which could not be described by a simple pore diffusion model using the calculated transport coefficients from batch mode. The shape of the breakthrough curves could be well described by a combined film and pore diffusion model. For the ungrafted Toyopearl DEAE 650M resin the breakthrough curve is more favorable and the influence of film diffusion to the mass transfer is reduced. It can be concluded that grafting will increase the capacity and the pore diffusion in batch mode but in column operation the grafting layer has a film resistance which plays an important role in the overall mass transfer.

Anion Exchange Resins↗
PubMedDate not supplied

Physical properties of poly(ethylene glycol) (PEG)-based resins for combinatorial solid phase organic chemistry: a comparison of PEG-cross-linked and PEG-grafted resins.

Three series of poly(ethylene glycol) (PEG)-based polymers were synthesized and characterized with respect to their physical properties. Polyoxyethylene-polyoxypropylene (POEPOP), polyoxyethylene-polyoxetane (SPOCC), and polyoxyethylene-polystyrene (POEPS-3) were synthesized respectively by anion polymerization, cation polymerization, and radical polymerization. Both bulk and suspension modes were used to synthesize the polymers from derivatized PEG monomers (PEG 400, PEG 900, and PEG 1500). The three supports were compared with two commercially available PEG-grafted supports (TentaGel S OH, ArgoGel-OH) and two polystyrene supports (aminomethylated polystyrene [PS-NH2] and macroporous aminomethylated polystyrene [PLAMS]) with respect to their swelling properties, loading, NMR spectral quality, as well as solvent and reagent accessibility. Loadings of 0.3-0.7 mmol/g were obtained for the PEG-based resins. Swelling of the PEG-based resins was determined to be higher than that of the PEG-grafted resins and polystyrene supports. The PEG-based resins gave better resolved high-resolution NMR spectra than the PEG-grafted resins when examined by magic angle spinning nanoprobe (MAS) NMR spectroscopy. Moreover, fluorescence quenching of polymer bound 2-amino-benzoate by protonation with p-toluenesulfonic acid showed moderate to fast diffusion through the polymer depending on the solvent and the polymer matrix.

Chemistry, Organic↗
PubMed2000

Elution of TEGDMA and BisGMA from a resin and a resin composite cured with halogen or plasma light.

Plasma arc light units for curing resin composites have been introduced with the claim of relatively short curing times. The purpose of the present study was to measure and compare elution of monomers from an experimental BisGMA-TEGDMA resin and a commercial resin composite when cured with a halogen unit and when cured with a plasma arc unit. Specimens of the materials were immersed in methanol, and the amounts of monomers released with time were analyzed by HPLC. By use of Fick's laws of diffusion, the amount of eluted monomers from the specimen at infinity was estimated. The elution from resin specimens and from resin composite specimens cured with the plasma arc light unit was 7 and 4 times higher, respectively, compared to the elution from specimens cured with the halogen unit. It was concluded that the plasma arc light curing unit did not provide optimal cure when used as recommended by the manufacturer.

Analysis of Variance↗
PubMed2004

Development of a solid-phase 'asymmetric resin-capture-release' process: application of an ephedrine chiral resin in an approach to gamma-butyrolactones.

The potential of a solid-phase asymmetric resin-capture-release strategy for high-throughput synthesis has been evaluated. Fukuzawa's Sm(ii)-mediated, asymmetric approach to gamma-butyrolactones was selected to illustrate the feasibility of such a process. Alpha,beta-unsaturated esters immobilised on an ephedrine chiral resin have been applied in an asymmetric approach to gamma-butyrolactones. Lactone products are obtained in moderate isolated yields with selectivities up to 96% ee. In addition, we have shown that the ephedrine resin can be conveniently recovered and recycled although in some cases lower yields were obtained on reuse of the chiral resin. A short synthesis of a moderate DNA-binding microbial metabolite using asymmetric resin-capture-release is also described.

4-Butyrolactone↗
PubMed2000

Shear bond strength of resin teeth to heat-cured and light-cured denture base resin.

The failure of the bond between acrylic resin teeth and denture base material remains a considerable problem. Previous research has indicated that the introduction of a bonding agent to the tooth-resin interface significantly increased the tensile bond strength. To further investigate this finding, and to complement the earlier study, a shear strength assessment was carried out. Both a commercial and an experimental bonding agent were evaluated for tooth retention when applied to heat-cured and visible light-cured (VLC) resin. A significant increase in shear bond strength was obtained when bonding agents were applied. The experimental cement gave the greatest increase in strength, although the VLC resin failed to achieve the same degree of tooth attachment as the heat-cured resin.

Acrylic Resins↗
PubMed1993

The use of intermediary resins when bonding glass polyalkenoate (ionomer) cement to composite resin.

This study was designed to examine the effects of three different types of glass polyalkenoate lining cement combined with three different types of bonding resin and varying surface treatments on the seal between the lining cement and the composite resin as used in the so called 'laminate' technique. The seal was assessed using a radioisotope and autoradiographic technique. Results showed that all the cements behaved in a manner specific to them. The seal of all systems examined could be improved, or at least, not compromised, by modification of the surface of the cement prior to attachment of the resin. Only one type of intermediate resin gave a reliable seal when applied to an unmodified surface of any of the cements under investigation. It is concluded that all the glass polyalkenoate cements tested behave differently when used beneath composite resin. Recommendations about the laminate restoration technique must be related to the specific combinations of materials used.

Composite Resins↗
PubMed1982

Effects of a nonabsorbable chelating resin on lead absorption, elimination, and accumulation in the rat. Resin effects on lead disposition.

In rats, oral administration of lead-chelating resin (Chelex-100) reduced the absorption of an oral lead dose (10 mg/kg) when both doses were given at approximately the same time. The same oral resin did not reduce blood lead concentrations when administered after the lead dose had been absorbed or after systemic lead administration (1 mg/kg, intracardiac), indicating that the resin did not influence lead elimination. As a dietary supplement the resin was also ineffective in reducing blood and kidney lead concentrations in rats exposed to lead in drinking water. Thus, the possible therapeutic uses of this lead-chelating resin may be limited.

Animals↗
PubMed2006

Effect of adhesive primer developed exclusively for heat-curing resin on adhesive strength between plastic artificial tooth and acrylic denture base resin.

Despite progress in the development of denture base resin and artificial tooth materials, dental clinics are still plagued with artificial teeth falling off the denture base--due to poor bond strength--after denture delivery. Against this background, this study sought to examine the effect and durability of an adhesive primer developed exclusively for heat-curing resin on the adhesive strength of heat-curing denture base acrylic resin to plastic artificial tooth. Test specimens were divided into four groups according to the treatment method of the artificial tooth's test bonding surface: air abrasion, adhesive primer application, adhesive primer application after air abrasion, and pretreatment only (control). After heat curing of acrylic resin onto the bonding surface, shear test was performed for two storage periods: 24-hour versus 100-day water storage. From the results obtained, it was revealed that the evaluated adhesive primer was significantly effective in increasing adhesive strength between artificial tooth and acrylic resin, although specimens were stored in water for 100 days.

Acrylic Resins↗
PubMed1975

[Studies on the dental methacrylic resins (part 4). Flow properties and curing times of the pour methacrylic resins (author's transl)].

Flow properties and curing times of the pour resins consisted of polymethyl methacrylate and methyl methacrylate were investigated by the viscosity and the temperature measurements. The polymers with various article sizes and molecular weights and the monomer with 0.005 per cent hydroquinone were used the pour resins respectively. The initiator system of benzoyl peroxide--N, N-dimethyl-p-toluidine was used for the polymerization. The results were as follows: 1) The viscosities of the pour resins were increased with the time elapsed. That was for reasons of physical phenomenon, that is, dissolution of polymer into monomer. The logarithmic viscosities increased linearly in proportion to the time elapsed. 2) The viscosities of the pour resins were increased by the reduction of the particle size of the polymer and by the increase of the molecular weight of the polymer. 3) The curing times of the pour resins were reduced by the increase of the concentrations of benzoyl peroxide and N, N-dimethyl-p-toluidine, and by the reduction of the particle size and the molecular weight of the polymer respectively.

Acrylic Resins↗
PubMed1989

[Effect of filler system on the mechanical properties of light-cured composite resins. I. Effect of various types of silica fillers on the mechanical properties of the composite resins].

To investigate the effect of silica fillers on the mechanical properties of visible light-cured composite resins, Bis-GMA-based composites with four types of silica fillers were prepared. The mechanical properties of the composites with splinter-shaped silica fillers increased with increasing the filler fraction. Although the spherical silica filler could be filled more with resin monomer than the splinter-shaped silica filler, the mechanical properties of spherical silica-filled composite were relatively lower than those of the composite with splinter-shaped silica fillers. The micro particle silica-filled composite showed no obvious increase in the mechanical properties in either the dry or wet conditions. SEM observations of the fractured resin surface revealed that fracture occurred through the resin matrix as well as the resin/filler interface and the mechanical properties of each composite resin were correlated with the nature of crack propagation.

Composite Resins↗
PubMed1989

[Relation of surface texture of fine finishing diamond point for composite resin and polished surface of composite resin].

Distribution of diamond grain size of seven fine finishing diamond points was measured by a digital image analyzer. Also influence of diamond grain size of fine finishing diamond points on finished surface of two types of visible light cured composite resins (semihybrid type and submicron filler type) were investigated. Diamond grain size was almost from 10 to 100 microns 2 in area. Diamond grain size was closely related to the surface roughness of semihybrid type composite resin, although it was not related to that of submicron filler type composite resin. Surface roughness of a submicron filler type composite resin finished at a low speed was less than that at a high speed. Grain size of diamond point and revolution speed may play an important role in surface texture of composite resin.

Composite Resins↗
PubMed1995

Reinforcement of denture acrylic resin: the effect of metal inserts and denture resin type on fracture resistance.

This study investigated the fracture load and deflection of acrylic resin specimens with different types of metal inserts. A metal adhesive denture resin (Meta Dent) and a conventional denture resin (Meliodent) were used with round metal, braided wires and mesh as inserts. There were eight groups and each group contained ten specimens. Each specimen was broken on a Monsanto testing machine using a three point load after storage in water at 37 degrees C for 48 hours. The results indicated that metal inserts enhanced the fracture resistance of both denture resins. No significant differences were found between the metal adhesive and conventional denture resin.

Acrylic Resins↗
PubMedDate not supplied

Sealing capacity of a resin-modified glass-ionomer and resin composite placed in vivo in Class 5 restorations.

A 2% methylene blue dye was used to assess the leakage resistance of class 5 resin-modified glass-ionomer and resin composite restorations placed in 17 adults. The teeth were extracted 75 to 90 days after placement of the restorations and immersed for 24 hours in the dye solution. Within 7 days after extraction the teeth were sectioned inciso-apically through the center of the restoration and inspected under a stereomicroscope at X20 to determine the depth of dye penetration. No significant differences between the resin-modified glass-ionomer and resin composite restorations at the incisal or cervical margins were found. Although no more than 30% of the restorations of either group exhibited microleakage, neither of the restorative systems was able to completely prevent leakage at either incisal or cervical margins.

Adult↗
PubMed1996

The effect of etchant and cement age on the adhesion of resin composite to conventional and resin-modified glass-ionomer cements.

The effects of etching with maleic or phosphoric acid on the adhesion of resin composite to resin-modified glass-ionomer cement restorative materials were evaluated through a shear bond test. These effects were determined with both recently set and aged cement. For the three resin-modified materials tested, compared to no etching, the two etchants improved or did not affect the adhesion of resin composite, regardless of the age of the cement. For a chemically cured material, included in the study as a control, the same effects were observed, except that etching of the recently set cement with maleic acid was detrimental to adhesion.

Acid Etching, Dental↗
PubMed1996

Fissure sealing with a light-cured resin-reinforced glass-ionomer cement (Vitrebond) compared with a resin sealant.

The aims of the present study were to evaluate the retention and caries-preventive effect of a single application of a light-cured resin-reinforced glass-ionomer cement (Vitrebond) in pits and fissures of newly erupted permanent first and second molars, when compared with a single application of a resin-based sealant (Concise White Sealant) during a 3-year period. The study group comprised 73 pairs of contralateral newly erupted permanent first and second molars (136 fissure sites) in 53 children (29 girls, 24 boys). A split-mouth experimental design was used in which the two sealants were randomly allocated to one of the teeth within each pair. Acid etching was not used before application of the glass-ionomer cement. The sealed teeth were checked for retention and caries after 1, 6, 12, 24 and 36 months. The resin-based sealant was almost totally retained after 3 years (97%) and there was no caries in these teeth. The glass-ionomer cement was increasingly lost and could be observed in only 9% of the sealed sites after 3 years. Carious lesions developed in 10 (7.4%) sites (nine teeth, seven children). It was concluded that the resin-based sealant is superior to the glass-ionomer cement in preventing caries, and that the superior retention of the resin probably is an important factor for this.

Adolescent↗
PubMed2004

An enrichment method of molybdenum on a cellulose nitrate resin for the determination by electrothermal atomic absorption spectrometry coupled with the resin suspension injection.

Cellulose derivative resin (CDR) suspensions containing resin particles of cellulose nitrate (CDR(CN)), cellulose acetate (CDR(CA)), or cellulose triacetate (CDR(CTA)) were prepared as the sorbent for resin suspension injection (RSI) electrothermal atomic absorption spectrometry (ETAAS), in which fine resin particles holding a desired trace element were directly injected into the graphite tube as the suspension. To compare the sorption ability, the distribution ratios of the Mo(VI)-phenylfluorone complex were measured between the aqueous phase and the sorbents, including the CDRs mentioned above and the finely divided anion exchange resin (AR). The results showed that the sorption ability decreases in the following order: CDR(CN) > or = AR > CDR(CA) > or = CDR(CTA). It was concluded that CDR(CN) was able to extract more than 98% of Mo(VI), and was suitable for RSI-ETAAS as well as AR. CDR(CN) was used for the determination of Mo in NIES certified reference materials, No. 10 Rice flour-unpolished; the results showed fairly good agreements between the analytical values and the certified values.

Journal Article↗
PubMed1979

[Physical properties of resins for veneer crown. (Part 1) Bending strength of thermosetting methacrylic resins (author's transl)].

The physical properties of thermosetting methacrylic resins contain a kind or more than two kinds of cross linking agents were investigated. Knoop hardness and bending strength after drying, water sorption and thermal cycling were listed in table 4 and 5. Hydrophilic resins absorbed water about 3 times as much as hydrophobic resins. The materials contain a small amount of hydrophobic cross linking agents in MMA indicate comparatively excellent properties after drying, water sorption and thermal cycling. Knoop hardness of resins generally reduced by water sorption, especially in the case of the resin contains a large amount of triethylene glycol dimethacrylate.

Absorption↗