Search results for " cement"
showing 10 items of 245 documents
Applications of conduction calorimetry to the setting reaction of zinc phosphate dental cement
1999
The kinetics of the exothermic setting reaction of zinc phosphate dental cement can be successfully investigated by conduction calorimetry. The primary objective of this study is to examine the effects arising from the addition of various additives to the liquid and calcination of cement powder. The rate of heat evolution versus time shows the occurrence of merely one maximum. In the case of unmodified orthophosphoric acid a sharp peak occurs early after onset of mixing due to the formation of crystalline α-hopeite. Commercial cement liquids contain aluminum and zinc. From the calorimetric curves it has been found that these cations act as a setting retarders, and ensure sufficient working …
Concrete columns confined with fibre reinforced cementitious mortars: Experimentation and modelling
2014
Abstract The structural behaviour of concrete columns strengthened with a system made up of fibre nets embedded in an inorganic stabilized cementitious matrix under an uniaxial load was investigated. Medium size specimens with circular and square cross-section were cast and subjected to monotonic uniaxial compression, to investigate the efficiency of a p-Phenylene BenzobisOxazole (PBO) Fibre Reinforced Cementitious Mortar (FRCM) system in increasing both strength and ductility. The experimental results show that the confinement system adopted produced a noticeable increment in strength and ductility, though the low mechanical ratios of fibre considered were not always able to ensure hardeni…
R.C. columns strengthened by PBO-FRCM under axial force and bending moment
2017
Fabric-Reinforced Cementitious Matrix (FRCM) systems, also known as Textile Reinforced Concrete (TRC) are nowadays widely used as confining material to enhance both strength and deformation capacity of columns of seismic resistant r.c. frames. In the past, when carbon fiber was used in the textile, experimental results showed that the efficiency of the wrapping is limited by the connection between substrate and fiber, which is not as effective as when epoxy resins are used. To improve the strength of the connection between fibres and mortar binder in FRCM system, the use of p-Phenylene BenzobisOxazole (PBO), having a molecular structure capable of establishing chemical bonds with hydrated c…
Fluoride release and uptake abilities of different fissure sealants
2016
Background: The long-term capability of resin sealants and glass ionomer cements to release fluoride is associated to a reduction in pit and fissure caries. The regular use of fluoride varnishes/toothpastes can result in the absorption of fluoride into the sealant. The objective of the present study was to assess the fluoride release/uptake capacities of different fissure sealants. Material and Methods: Three different fissure sealants (Fuji Triage/GC, Fissurit FX/Voco and Grandio Seal/Voco) were examined. Ten discs of each material were prepared. Each disc was incubated with distilled water and then the solution analyzed for diluted for fluoride concentration, using a combination of fluori…
Restore the natural: a review and case series report on reattachment
2014
Reattachment of the original tooth fragment to the fractured tooth helps in maintaining the tooth’s color, wear resistance, morphology and translucency in the restoration. This article describes the reattachment of fractured fragment using a fiber post and dual cure resin cement with a self-etching adhesive. Two young male patients reported with a complicated crown fracture of the right maxillary central incisor due a road traffic accident. The fractured fragments were loosely attached to the palatal gingival tissue, which was then surgically removed and preserved for the reattachment procedure. The fractured tooth segments were successfully reattached following fiber post cementation. Toot…
An in vitro comparison of different adhesive strategies on the micro push-out bond strength of a glass fiber post
2010
Objectives: To evaluate in vitro the push-out bond strengths of a glass fiber post adhesively luted with self-etching resin based and self-adhesive luting cements, as well as modified application procedure of self-adhesive luting cements in combination with single step self-etch adhesives. Materials and methods: Fifty single-rooted human maxillary central incisor teeth were endodontically treated and divided into five groups (n=10). Glass fiber posts (RelyX Fiber Post) were cemented with the following materials: group 1: ED Primer II/Panavia F 2.0 (PAN); group 2: RelyX Unicem (RU); group 3: Maxcem (MC); group 4: Adper Prompt L-Pop (PLP)/RelyX Unicem; group 5: Optibond all-in-one (OB)/Maxcem…
Stable, hydroxyl functional polycarbonates with glycerol side chains synthesized from CO(2) and isopropylidene(glyceryl glycidyl ether).
2012
A series of functional polycarbonates, poly((isopropylidene glyceryl glycidyl ether)-co-(glycidyl methyl ether) carbonate) (P((IGG-co-GME) C)) random copolymers with different fractions of 1,2-isopropylidene glyceryl glycidyl ether (IGG) units, is synthesized. After acidic hydrolysis of the acetal protecting groups, a new type of functional polycarbonate prepared directly from CO(2) and glycerol is obtained, namely poly((glyceryl glycerol)-co-(glycidyl methyl ether) carbonate) (P((GG-co-GME) C)). All hydroxyl functional samples exhibit monomodal molecular weight distributions with PDIs between 2.5 and 3.3 and M(n) between 12 000 and 25 000 g mol(-1) . Thermal properties reflect the amorphou…
The effect of glass ionomer and adhesive cements on substance P expression in human dental pul
2013
Objectives: The purpose of this study was to quantify the effect of glass ionomer and adhesive cements on SP expression in healthy human dental pulp. Study Design: Forty pulp samples were obtained from healthy premolars where extraction was indicated for orthodontic reasons. In thirty of these premolars a Class V cavity preparation was performed and teeth were equally divided in three groups: Experimental Group I: Glass Ionomer cement was placed in the cavity. Experimental Group II: Adhesive Cement was placed in the cavity. Positive control group: Class V cavities only. The remaining ten healthy premolars where extracted without treatment and served as a negative control group. All pulp sam…
Controlling the cohesion of cement paste
2005
The main source of cohesion in cement paste is the nanoparticles of calcium silicate hydrate (C-S-H), which are formed upon the dissolution of the original tricalcium silicate (C(3)S). The interaction between highly charged C-S-H particles in the presence of divalent calcium counterions is strongly attractive because of ion-ion correlations and a negligible entropic repulsion. Traditional double-layer theory based on the Poisson-Boltzmann equation becomes qualitatively incorrect in these systems. Monte Carlo (MC) simulations in the framework of the primitive model of electrolyte solution is then an alternative, where ion-ion correlations are properly included. In addition to divalent calciu…
The influence of an ion-exchange resin on the kinetics of hydration of tricalcium silicate
2010
The addition of a finely-ground ion-exchange resin makes it possible to modify the hydration kinetics of C3S pastes. Analyses of the liquid phase in pastes and more dilute suspensions show that the resin exchanges calcium ions for sodium ions very rapidly during the early stage of hydration and therefore the concentration of silica in solution increases. The resin impacts the hydration of C3S by other mechanisms which depends on the resin quantity added. For a high resin quantity, the induction period is very short, but the longer-term hydration is enhanced compared to a reference sample without resin. We hypothesize that the surface of the resin can provide sites for the nucleation and gro…