Biomedical subjects

C Prati

Publications and source records attributed to C Prati.

At least 55 records · Page 3Linked to original sources

PubMed1993

Thermodynamical aspects of the polymerization reaction of PMMA cement mixed with phosphatic mineral phases.

The main problem related to the use of polymeric cement in orthopaedics is the high temperature reached during the polymerization, causing necrosis. This paper reports a thermodynamical study of the polymerization reaction of an acrylic cement mixed with powdered phosphatic phases. In particular, mixing of alpha-tricalciumphosphate, beta-tricalciumphosphate and hydroxyapatite was proposed. Important preliminary results indicated that amounts of about 66% by weight of alpha-tricalciumphosphate reduced the polymerization temperature to about 58 degrees C in respect to 100 degrees C of pure acrylic cement. In addition, a special chamber was designed and realized to monitor the temperature variations involved during the polymerization reaction of the different mixtures.

Bone Cements↗

PubMed1993

Chemistry and structure of a new canal sealer showing a dynamical behaviour.

The complete apical seal without percolation and transit of bacteria and their products along the wall of the endodontic canal is the fundamental condition to obtain a lasting result of a correct endodontic therapy. The aim of this study was to characterize a new formulation cement (PROENDO, VEBAS, Italy) with characteristics totally different from the conventional ones. Finally, we can assert that an alloplastic material like PROENDO, which is the subject of this study, bio-compatible, osteo-inductive, non-toxic, with adhesive capacities, is able to quicken the phenomena of restoration and recovery after an endodontic operation.

Calcium Phosphates↗

PubMed1992

Effects of dentin surface treatments on the shear bond strength of Vitrabond.

The influences of nine dentin surface treatments were evaluated on the shear bond strength of a new light-cured glass-ionomer cement (GIC) and on the SEM morphology of the treated dentin surfaces. The following treatments were performed: saline solution (control), NaOCl, acidic glycine, EDTA, malic acid, malic acid plus glycine, polyacrylic acid, tannic acid, and neutral+acidic oxalate solutions. Buccal dentin surfaces were polished with #320-grit abrasive paper, treated with one of the chemicals, washed, and air-dried. Cylindrical GIC samples were then applied to the dentin surface, stored in 100% humidity, and tested after 24 h. SEM observations demonstrated no effect of saline or NaOCl treatment on the smear layer but its complete removal with exposure of collagen fibrils after malic or malic acid plus glycine treatment. Partial removal of the smear layer occurred following glycine treatment and with tannic or polyacrylic acids. Complete removal of the smear layer was seen after EDTA or pyruvic acid treatment. Oxalate treatment produced a layer of crystals, which completely covered the dentin surface. Shear bond strength of GIC was significantly increased only by treatment with the oxalate solutions.

Dental Bonding↗

PubMed1992

Relationship between bond strength and microleakage measured in the same Class I restorations.

Microleakage measurements were made by use of a pressurized fluid method in Class I restorations prepared in extracted human teeth just prior to measuring the tensile bond strengths of the same restorations. The restorative materials included dentin bonding systems that are applied to smear layers as well as those which remove the smear layer. A light-cured glass-ionomer cement was also included. The results demonstrated that there was an inverse relationship between dentin bond strength and microleakage in some materials and that the bond strengths made to three-dimensional Class I cavities were much lower than those made to flat dentin surfaces. Measurement of microleakage by fluid filtration had no apparent effect on bond strength.

Adhesives↗

PubMed1992

Calcium oxalate smear layer: mineralogical and crystallographic study.

Different methods to reduce dentine hypersensitivity have been tested by means of oxalate treatments. Natural material (20 teeth) and commercial oxalates have been employed. As a result the dentinal tubules are filled by small crystals preventing dental disease. Permeability measurements have been performed in order to quantify results. The composition of the synthetic smear layer produced after oxalate treatment have been investigated by powder diffraction method suggesting calcium oxalate formation.

Calcium Oxalate↗

PubMed1992

Dentin wetness, permeability and thickness and bond strength of adhesive systems.

This study evaluated the shear bond strength of Scotchbond 2, Clearfil PhotoBond, Tenure, All-Bond and Vitrabond and their sensitivity to dentin permeability, wetness and thickness. Occlusal dentin was prepared from extracted human teeth that were connected to a hydraulic pressure apparatus. Dentin permeability was calculated as a fluid flow rate and dentin surface wetness was evaluated using the Periotron device. Dentin thickness was measured using a pincer caliper. Shear bond strength was tested after 24 hours storage under hydrostatic pulpal pressure. Several significant correlations were found between dentin wetness, dentin permeability and remaining dentin thickness and the shear bond strengths of Scotchbond 2, Tenure and All-Bond/no etch. No apparent correlations were observed for the other adhesive systems.

Acid Etching, Dental↗

PubMed1991

Shear bond strength and microleakage of dentin bonding systems.

This study evaluated the shear bond strength and microleakage of class V non-retentive restorations with 10 different dentin bonding systems. Some were tested with different composite resins. For the shear bond test, eight specimens were prepared for each product and tested in a universal testing machine. For the microleakage test, 158 V-shaped class V cavities extending to the cementoenamel junction were prepared, coated with a dentin bonding system, and restored with a composite resin. After 250 thermocycles, the teeth were immersed in a dye solution for 48 hours, longitudinally sectioned, and evaluated for microleakage. Both test procedures resulted in significant differences between the various materials. The bond strength failed to completely prevent microleakage at the dentinal wall. The new generation of dentin bonding systems offer a significant improvement over previous materials.

Acrylates↗

PubMed1991

Hydrostatic intrapulpal pressure and bond strength of bonding systems.

The purpose of this study was to evaluate the effect of intra-pulpal pressure on shear bond strength of three light-cured glass-ionomer cements (GC lining cement, Vitrabond, and Zionomer) and four dentin bonding agents [Gluma/Scotchbond, Scotchbond 2, MBL, and Clearfil Photo Bond]. Buccal dentin surfaces were prepared just below the DEJ by means of a diamond bur. Dentin treatments were made for Zionomer (Zionomer conditioner), Scotchbond 2 (Scotchprep), MBL (10-3 solution), Clearfil PB (H3PO4), GC lining cement (Polyacrylic acid), and Gluma/Scotchbond (EDTA). Resin composites were inserted into tubes, positioned on dentin, cured, tested after five min or 24 h, and compared with samples bonded and stored under an intra-pulpal pressure of 36 cm of saline. After 24 h in superficial dentin, intrapulpal pressure reduced the bond strength only in MBL, Scotchbond 2, and Zionomer. Clearfil PB bond strength was increased, while Vitrabond, GC lining cement, and Gluma/Scotchbond were unaffected by the presence of pulpal pressure. However, in deep dentin, Scotchbond 2 and Clearfil PB shear bond strengths were significantly reduced by storage in the presence of 36-cm H2O pulpal pressure. Only Vitrabond remained unaffected by pulpal pressure in deep dentin.

Composite Resins↗

PubMed1991

Measurement of dentin permeability and wetness by use of the Periotron device.

The ability of the Periotron device to measure changes in dentin permeability and wetness was evaluated by use of extracted human teeth in vitro. Pulpal pressures were varied from zero to 40 cm H2O for simulation of different pulpal tissue pressures. Non-physiologic pulpal pressures of 703 cm H2O were used for comparison of dentin permeability measurements made with the Periotron device with those made using micropipettes. Measurements made with the Periotron device correlated well with methods used previously for measurement of dentin permeability. The shear bond strength of Scotchbond 2/Silux was measured 24 h after being bonded to dentin held at zero pulpal pressure. There was an inverse correlation between the shear bond strengths of Scotchbond 2/Silux and Periotron values, suggesting that increased wetness decreases the bond strength of that system. The Periotron device offers a new, simple, convenient measure of dentin surface wetness which may be useful in dentin bonding studies.

Adhesiveness↗

PubMed1991

Oxalate solution and collagen-oxalate solution as protective liners for dentine.

The aim of the present study was to evaluate under scanning electron microscopy the ability of different chemically reactive solutions to form a protective layer on dentine. The materials selected were an oxalate solution, a collagen-oxalate solution, a collagen-oxalate solution plus glutaraldehyde and a saline control solution. Small dentine fragments, obtained from extracted human teeth, were treated with the various chemical solution for 60 seconds. All samples were then examined in a Jeol scanning electron microscope. The preliminary observations suggest that dentine may be covered by a mixture of oxalate crystals and collagen producing a homogeneous layer of reactive agents.

Collagen↗

PubMed1991

Scanning electron microscopy and dentinal permeability analysis of smear layer.

The aim of the present study was to evaluate the surface morphology and the permeability of dentine after different acid treatments: polyacrylic acid, maleic acid, phosphoric acid and saline solution as control. Dentine permeability was expressed as hydraulic conductance. All the acid treatments removed the smear layer and increased the dentine permeability.

Acid Etching, Dental↗

PubMed1991

Microleakage in composite resin restorations.

The aim of the present study was to evaluate the marginal microleakage of the newest generation of composite resin restorative materials. Class V restorations were prepared in human extracted teeth. Different combinations of restorative materials were used. All the materials tested showed marginal microleakage along the dentinal walls, suggesting that the adhesion value is not sufficient to counteract the composite shrinkage and to reduce the marginal space.

Adult↗

PubMed1991

Oxalate desensitising treatment of dentinal surface.

It is well known that a typical painful feeling is caused by impact of different agents and by thermodynamic conditions upon the dentine layer of the tooth. Therefore the action by artificial solutions should be tested to study how the induced modifications might inhibit the pain. The aim of the present study is to evaluate by scanning electron microscopy (SEM) the morphology of dentine surface after different chemical treatments. Oxalate solutions are able to produce a layer of large crystals, while acid solutions remove the smear layer and open the dentinal tubules.

Dentin↗

PubMed1991

Dental composite resin porosity and effect on water absorption.

The aims of this study were: 1) to characterize the solubility and water absorption of different composite resins used as dental restorative materials; 2) to analyse their surface morphology using S.E.M. The resins tested were a mixture of glycidyl methacrylate (Bis-GMA) and TEGMA filled with silane-coated particles of inorganic fillers, and Bis-GMA and urethane resin. Cylindrical samples of composite resin were polymerized and stored in distilled water and weighed after different times. SEM analysis demonstrated voids and porous in several samples. The present study shows that dental restorative composite loose a small percentage of their components during storage time and that the type of resin, the nature of fillers and the methods of polymerization greatly influence water uptake and solubility of dental composite resin materials. These findings could explain the loss of anatomic form and the occlusal degradation of dental composites in "in vivo" conditions.

Absorption↗

PubMed1991

[Dentinal bonding systems and the tensile bond strength test].

The aim of the present study was to evaluate the tensile bond strength of four dentinal bonding agents (DBAs) to the dentin surface. Tensile bond test procedure was made using a universal testing machine. Human extracted third molars were mounted with self-curing acrylic resin in cylindrical molds. The dentin occlusal surface was ground with 320-grit silicon carbide abrasive paper. The DBAs were prepared according to manufacturers' directions and applied on the dentin surface. Cylindrical teflon tubes were placed on the dentin surface and filled with a microfilled resin. The samples were then stored in a humidifier at 37 degrees C for 24 h. Six specimens were prepared for each group. A statistically significant difference was observed among the four groups. It has been observed that certain materials showed a dentin bond value superior to cohesive value of composite resin.

Dental Cements↗

PubMed1990

[Biocompatibility of dentinal adhesive systems in conservative dentistry].

Several studies have been published on "in vitro" and "in vivo" evaluations on pulpal and dentin effects of new dentinal bonding agents. The present study analyses the current status of biocompatibility of these materials. It has been suggested that a good biocompatibility it is only possible if no bacteria penetration and microleakage are present along dentinal walls and around restoration cavity. Finally it is not well defined the importance of smear layer removal from cut dentin surface.

Dental Cements↗

PubMed1990

Early marginal leakage and shear bond strength of adhesive restorative systems.

The aims of this study were to assess in vitro the early marginal seal effectiveness in Class V restorations at the cemento-enamel junction, and the early shear bond strength of several composite and dentin bonding system combinations. The seal effectiveness was studied by evaluating the dye penetrations: (a) along the superficial margin of restorations (width of surface microleakage); (b) along the dentin cavity walls (length of microleakage); and (c) toward the pulp (depth of microleakage). Good correlations were demonstrated among the seal evaluations, but no relationships were apparent between these and shear bond strength. Our study suggests that the marginal seal is influenced by composite properties more than by bonding agents. The shear bond analysis indicates only the adhesive potential of the materials without considering the composite shrinkage effects on marginal gap after the photocuring setting reactions.

Composite Resins↗

PubMed1990

[Glass-ionomer cements in Class V restorations].

The aim of the present study was to evaluate the effect of two different techniques of glass-ionomer application on the marginal microleakage in Class V restorations. Two types of composite resins were also used. Nonretentive Class V cavities were prepared at the cementum enamel junction of human extracted third molars. Glass-ionomer cements were applied with a chamfer technique or as base in the floor of the cavity. After restoration, the samples were stored in dye solution, sectioned and observed under optical stereomicroscope. The base technique for glass-ionomer cements showed less microleakage than the other restorative methods.

Composite Resins↗