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Biomedical subjects

J M Antonucci

Publications and source records attributed to J M Antonucci.

18 recordsLinked to original sources
PubMed1992

Adhesive properties of modified glass-ionomer cements.

The incorporation of water-soluble polymers and/or vinyl monomers into glass-ionomer cements can yield toughened "hybrid cement-composites". This study compared a commercial water-hardening glass-ionomer cement and seven experimental hybrids in their bonding to both dentin and Silar composite. The cements were sanded and phosphoric-acid-etched or left with an unaltered matrix-formed surface when adhesion to composite was tested. The seven hybrids included: 15% 2-hydroxyethyl methacrylate (HEMA) with appropriate initiators/activators, 29% HEMA, 27% HEMA + 0.5% polyacrylic acid (PAA), 0.5% PAA, 1.5% PAA, 2.5% polyvinyl alcohol, and 2.5% gelatin. Acceptable bond strengths to applied composite and to dentin were observed for most of the modified hybrid cements. There were higher bond strengths with composite when the hybrids were left unetched. Bonding of some unetched, HEMA-containing cements achieved bond strengths (29% HEMA, 10.09 MPa) significantly higher than those of the unmodified cement (4.92 MPa). Resin-modified cements may promote better bonding by improved interaction and compatibility with the resin component of the composite.

Acid Etching, Dental↗
PubMed1992

Evaluation of methylene lactone monomers in dental resins.

alpha-Methylene-gamma-butyrolactone (MBL), which can be described as the cyclic analog of methyl methacrylate, exhibits greater reactivity in free radical polymerizations than conventional methacrylate monomers. Unfilled resin formulations composed of Bis-GMA/MBL or Bis-GMA/TEGDMA/MBL were light-cured. The effect of the more reactive methylene lactone monomer on mechanical properties and the degree of conversion of the polymers was examined. The infrared absorption bands for the carbon-carbon double bonds of MBL and the methacrylate monomers are well resolved and allow the conversion of each component to be calculated individually. The incorporation of a small amount of MBL (5 w/o) to Bis-GMA significantly increased the conversion; however, additional MBL (10 to 30 w/o) did not further increase the Bis-GMA conversion level. This appears to indicate an incompatibility between MBL and the bulky Bis-GMA monomer. Addition of 10 w/o MBL to Bis-GMA/TEGDMA (7:3) resulted in a cured resin with 71% methacrylate and 75% overall conversion efficiencies compared with the 57% conversion of the control formulation. The diametral tensile and the transverse strengths were approximately 10% greater for the MBL resin compared with the Bis-GMA/TEGDMA control; however, these differences were not statistically significant. The synthesis and polymerization of several substituted methylene lactones was also studied.

4-Butyrolactone↗
PubMed1992

Effects of surface-active resins on dentin/composite bonds.

Effective dentin bonding systems based on para-PMDM diadduct of pyromellitic dianhydride and 2-hydroxyethyl methacrylate (HEMA) have been developed (Bowen et al., 1982). Para-PMDM, a solid of limited solubility, is usually applied from an acetone solution to dentin that has been preconditioned with acid and N-phenylglycine. The feasibility of using a liquid, surface-active bonding resin to substitute for or to supplement para-PMDM was explored. Mono(2-methacryloyloxy)ethyl phthalate (MMEP), a liquid, monofunctional homolog of para-PMDM (derived from the reaction of phthalic anhydride with HEMA) was used to formulate several bonding resin systems and solutions. Dentin surfaces were pretreated according to several variations of a three-step bonding protocol involving sequential application of 6.8 w/o ferric oxalate in 2.5 w/o HNO3, N-phenylglycine in acetone, and an experimental bonding resin before placement of a chemically cured composite restorative material. Tensile bond strengths were tested after 24 h storage in distilled water at 23 degrees C. The results suggest that solutions based on MMEP and/or para-PMDM in acetone or in other monomers, especially those containing HEMA, can effectively promote bonding to dentin. A new mechanism for the observed self-polymerization of MMEP or para-PMDM with N-phenylglycine is proposed.

Acetone↗
PubMed1991

Filler systems based on calcium metaphosphates.

Calcium metaphosphates (CMP's)--a unique class of phosphate minerals possessing polymeric structures, [Ca(PO3)2]n, and having refractive indices of approximately 1.54-1.59-- are optically compatible with resins such as BIS-GMA. In this study, several types of CMP's were prepared and evaluated for their potential as fillers for visible-light-activated (VLA) dental composites. The vitreous (V) and beta-crystalline forms of CMP were prepared by controlled thermolysis of monocalcium phosphate monohydrate, Ca(H2PO4)2.H2O. Hybrid fillers were also prepared by thermal methods. Fillers, characterized by IR spectroscopy and optical microscopy, were prepared in several size ranges (e.g., 1-100 microns). VLA composites were formulated by use of both untreated and surface modified CMP's. V-CMP and its hybrids yielded composites which expanded when stored in water but were of low strength, e.g., diametral tensile strength, (DTS) = 8 MPa. beta-CMP composites were more moisture-resistant, had higher DTS's (from 12 to 33 MPa), and showed a tendency to arrest brittle fracture. These novel fillers have potential uses in resin-based materials such as dental composites, cements, and adhesives.

Calcium Phosphates↗
PubMed1991

Discoloration of dental cements and composites in a sulfide solution.

In an early study the discoloration of certain hardened silicate cements, after exposure to an atmosphere of hydrogen sulfide (H2S) for 24 h at room temperature, was ascribed to the formation of dark-colored sulfides of base metal impurities (Paffenbarger et al. JADA 25,32,1938). A recent study noted that, in general, silicate and glass ionomer cements were more prone to color shifts than composites after exposure to H2S for 9 weeks (Sugawara, Ph. D. Thesis, Nihon Univ.). The aim of the present study was to devise a simple, aqueous sulfide exposure test for esthetic restorative materials. The general procedure was to expose specimen disks to a 0.1% (w/v) sodium sulfide solution, adjusted to pH 9, for 1-7 days at 37 degrees or 55 degrees C. The 55 degrees C-Na2S exposure was designed as an accelerated test. Materials studied included: 1 silicate and 2 silicophosphate cements of known lead content, a glass ionomer cement (FIIF), several commercial composites and an experimental, hydrophilic composite. Known amounts of base metal contaminants in the form of appropriate salt solutions were added to the liquid components of FIIF and the composites. Specimens exposed to distilled water under the same conditions served as controls. Exposure to the aqueous sulfide medium resulted in the following ranking in order of decreasing discoloration: Glass ionomer cement greater than silicophosphate cement greater than silicate cement greater than hydrophilic composite greater than hydrophobic composite. Generally, the results of the aq. Na2S test paralleled those obtained with H2S. The degree of discoloration is dependent on a number of factors: the nature, concentration and leachability of the metal impurities, and the hydrophilicity and permeability to sulfide of the esthetic restoratives.

Chlorides↗
PubMed1989

Formation of hydroxyapatite in hydrogels from tetracalcium phosphate/dicalcium phosphate mixtures.

Apatitic calcium phosphate cements, formed by the ambient reaction of tetracalcium phosphate (TTCP) with dicalcium phosphates (DCP), have been recently reported. H2O or dilute aq. H3PO4 (0.2%) is used as the liquid vehicle for this reaction. The aim of this study was to ascertain if hydroxyapatite (HAp) can form in self-cured hydrogel composites containing TTCP/DCP mixes. The setting times (ST) and diametral tensile strengths (DTS) of these hydrogel composites were also determined. The hydrogels were of two types: (1) vinyl thermosets derived from the copolymerization of HEMA (2-hydroxyethyl methacrylate) and cross-linking monomers, and (2) polyelectrolyte-based hydrogels formed from aq. poly(alkenoic acids), e.g., poly(acrylic acid). Cylindrical specimens 6 mm D x 3 mm H were prepared and stored in H2O for up to 30 days. The HEMA composites were hardened in 7-15 min by free radical initiation (benzoyl peroxide/tertiary aromatic amine). The polyelectrolyte cements were hardened in 6-8 min. After various periods of storage in H2O at 37 degrees C, some of the specimens were examined by X-ray spectroscopy for HAp. HAp formation was not observed in the HEMA composites even after 30 days of H2O storage but was detected in the polyacid cements. The 24-h DTS values of the HEMA composites (14-26 MPa) were higher than those of the polyacid cements (7-12 MPa). Both the H2O content and pH may thus be factors controlling the rate and extent of HAp formation in hydrogel composites containing TTCP/DCP mixtures.

Calcium Phosphates↗
PubMed1989

Detection of lead in human teeth by exposure to aqueous sulfide solutions.

A recent study has shown that the presence of lead (Pb) as well as other base metals in esthetic restorative materials, especially dental cements, is detectable by color shifts induced by exposure of hardened specimens to a 0.1% (w/v) aqueous solution of sodium sulfide, Na2S. The present study was initiated to determine the applicability of this simple exposure test to the detection of Pb in human teeth. Extracted whole teeth as well as sectioned, thin specimens were exposed first to either a 0.01% or a 0.001% (w/v) aqueous solution of lead nitrate, Pb (NO3)2, at 37 degrees C for 24 h. After rinsing with distilled H2O and a subsequent 24 h exposure to the 0.1% Na2S solution at 37 degrees C, the tooth specimens were examined visually and by a dental color analyzer for color changes. The latter color measurements were evaluated by the Lab system of Hunter, and the color difference, delta E, was determined. Neither control specimens exposed to distilled H2O only or to 0.1% Na2S only exhibited any significant change in appearance after 24 h of storage at 37 degrees C. However, specimens exposed first to the Pb (NO3)2 solutions showed discernible delta E values after exposure to the Na2S solution. Delta E was greatest for specimens exposed to the more concentrated Pb (NO3)2 solution. Most of the discoloration in both thin and intact tooth specimens was confined to the outermost layers of the tooth structure. For the intact specimens, the greatest degree of discoloration occurred in the cementum, the most permeable part of the tooth structure.

Adult↗
PubMed1988

Adhesion to dentin by means of Gluma resin.

In its present version, the Gluma system for bonding restorative resin to dentin involves the application of an enamel bonding agent prior to the composite resin. Conceivably, pretreating the dentin with solutions of amino acids, and incorporating camphorquinone and selected methacrylic monomers into the Gluma adhesive would nullify the need for the enamel bonding agent. A bond strength to dentin of 13.4 MPa was obtained in the control experiment. Using a solution of pyruvic acid and glycine as pretreatment, and an optimized adhesive mixture containing glutaraldehyde, HEMA, BIS-GMA, camphorquinone, and water, bond strengths to dentin of 14.5 MPa and to enamel of 23.3 MPa were obtained. Thus, the new Gluma bonding system gave acceptable bond strengths without the prior application of enamel bonding agents.

Adhesiveness↗
PubMed1988

Wear and microhardness of a silver-sintered glass-ionomer cement.

Knoop Hardness and pin-and-disc-wear measurements were made on a commercial silver-sintered glass-ionomer cement. The objective was to determine whether the incorporation of a bonded-metal-to-glass filler would enhance durability as determined by the above measurements. As with the previous work on conventional (non-metalized) glass-ionomer cements, the specimens were preconditioned at 37 degrees C in air, water, 0.02 mol/L lactic acid (pH 2.67), and heptane. The influence of these media on the microhardness of the silver-sintered material was about the same as that on the conventional materials. Storing in air produced dehydration, which increased the hardness considerably. Heptane storage increased the hardness less, but this increase is attributed to continued curing during storage. After storage in water, the hardness was essentially unchanged; the influence of increased cure is believed to be offset by softening or plasticization from water uptake. Lactic acid produced a decrease in hardness from chemical dissolution as seen from the SEM observations. In most cases, in particular for the air-stored specimens, the wear resistance was enhanced markedly over that of the conventional materials evaluated previously. The exception was the lactic acid-stored specimens for which little, or no, improvement was observed during early periods of wear. The incorporation of silver appeared to provide lubrication, thus reducing wear. However, catastrophic failure from brittle fracture was still a problem, but its occurrence was less frequent.

Cermet Cements↗
PubMed1987

Wear and microhardness of glass-ionomer cements.

Pin-and-disc wear and Knoop Hardness measurements were made on three commercial glass-ionomer cements having slightly different compositions. The specific objective was to determine whether these cements have potential for use in posterior teeth, and, if not, what modifications in composition and structure would be appropriate to enhance their performance. The specimens were pre-conditioned in air, water, or lactic acid at 37 degrees C for one week prior to being wear-tested. Although differences among the samples were noted, some common trends were observed. From changes in hardness, before and after storage, two opposing trends were observed. One trend involved continued cross-linking and possible dehydration, resulting in a substantial increase in hardness. The other trend involved softening from penetrant liquid absorption and a concomitant decrease in hardness. The wear resistances compared favorably with those for resin-based composites except for the lactic-acid-stored specimens, for which changes in microstructure were revealed by SEM. All specimens were very brittle, and catastrophic failure during wear was frequent. Although our conclusion is that glass-ionomer cements with composition similar to those evaluated here are not acceptable for posterior occlusal application, some compositional changes may enhance their performance in stress-bearing applications.

Air↗
PubMed1979

New initiator systems for dental resins based on ascorbic acid.

Several promising initiator systems for the ambient polymerization of dental monomers were developed utilizing the oxidation-reduction reactions of certain organic peroxides and certain transition metal compounds with L(+) ascorbic acid and its derivatives.

Amines↗
PubMed1979

New amine accelerators for composite restorative resins.

The overall characteristics of the composites cured with a number of newly synthesized, tertiary aromatic amines compare favorably to those of resins polymerized with commonly used accelerators. Maximum compressive and tensile strength for the composites are obtained only over a narrow concentration range of accelerator used.

Amines↗
PubMed1978

Aldehyde methacrylates derived from hydroxybenzaldehydes.

Three crystalline aldehyde methacrylates with low melting points were synthesized from the readily available, isomeric hydroxybenzaldehydes and 2-bromoethyl methacrylate. These monomers can be purified by recrystallization and liquified by admixture in various proportions to obtain polymerizable liquids having workable viscosities at room temperature. These monomers may be used alone or as blends with other methacrylates since they are miscible and copolymerizable with the usual dental monomers. Also, they should be studied with other functional methacrylates designed to promote adhesion via the mineral phase to determine if this synergistic approach can improve the adhesion of dental resins to dentin. These aldehyde methacrylates, their mixtures, polymers and copolymers merit evaluation as adhesion-promoting agents for proteinaceous substrates such as bone and dentin.

Acrylates↗
PubMed1977

Adhesive bonding of various materials to hard tooth tissues: XIII Synthesis of a polyfunctional surface-active amine accelerator.

Surface-active amine polymerization accelerators can be prepared by the reaction of polyepoxy resins with the sodium salt of N-phenylglycine and N-methyl-p-toluidine. These materials are expected to promote adhesion through complexation with surface calcium (or other metal ions), utilizing several chelating groups per molecule, and by functioning as polymerization accelerators for dental resins; they can also function as catalysts for the anionic polymerization of cyanoarylate monomers.

Amines↗
PubMedDate not supplied

Dimethacrylates derived from hydroxybenzoic acids.

Since the color stabilities and durabilities of current composite and pit and fissure sealant resins need improvement, it is worthwhile to evaluate innovations that might accomplish this goal. Accordingly, three crystalline dimethacrylate monomers with low melting points were prepared from the isomeric hydroxybenzoic acids and 2-bromo-ethyl methacrylate. These monomers can be purified by crystallization and liquified by admixture in various proportions to obtain a polymerizable liquid of suitable viscosity at room temperature. In contrast to the analogous dimethacrylate monomers that were derived from the phthalic acid isomers, these aromatic ether-ester dimethacrylates do not form colored charge-transfer complexes with tertiary aromatic amine accelerators. These monomers and their polymers should be elevated for use in composites and pit and fissure sealant formulations.

Acrylates↗
PubMedDate not supplied

Reinforced polycarboxylate cements.

Mechanical properties of polycarboxylate cements are greatly improved by incorporation of high modulus fibers such as potassium titanate into acrylic-itaconic acid and acrylic-itaconic-acronitic acid copolymers. Other desirable properties of the cements are not changed by the addition of fibers.

Aconitic Acid↗