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Biomedical subjects

J L Ferracane

Publications and source records attributed to J L Ferracane.

At least 73 records · Page 4Linked to original sources
PubMed1990

Comparative study of hydroxyapatite and titanium dental implants in dogs.

This study compares the clinical performances and histologic response in dogs to a cylindrical implant with a surface consisting of dense hydroxyapatite (HA) and a threaded titanium implant in functionally loaded and unloaded conditions. Implantation was performed in five dogs, which were killed at 2 or 4 months postfunctional condition (4 or 6 months after implantation). Clinical evaluation showed that neither implant demonstrated significant movement, and assessment of gingival inflammation and sulcus depth showed no significant differences between them. After axial sectioning, the titanium implants were easily removed from the bone, whereas the HA-coated implants were adherent to the bone. Histologically, both implants showed osteogenic ingrowth to the surface in functional and nonfunctional conditions. High-magnification scanning electron micrographs of plastic sections showed that a portion of the interface between the HA-coated implant and the bone showed no gap, whereas gaps were observed at all interfaces with the titanium implant. Histomorphometric analysis by light microscopy indicated that there was no significant difference in the percent bone contact length. Clinically, the two implants behaved similarly.

Alveolar Process↗
PubMed1990

Rate of elution of leachable components from composite.

The uptake of solvent and the elution of molecules from a dental composite and an unfilled resin were monitored with time during soaking in either water or an ethanol/water mixture. The results showed that approximately 50% of the leachable species were eluted from the composite within three hours of soaking in water, while 75% of the leachable molecules were eluted into the ethanol/water mixture. Elution of nearly all of the leachable components was complete within a 24-hour period in either solvent. The study lends support to the view that dental composites do not provide a chronic source of unreacted monomer to the pulp or other oral tissues, due to a rapid and complete elution of the molecules.

Analysis of Variance↗
PubMed1990

Evaluation of glass-cermet cores under cast crowns.

The goal of this study was to compare two core materials--glass-cermet and amalgam--in terms of crown retention when significant tooth structure is missing. The glass-cermet's ability to bond to teeth with and without the aid of retentive pins and/or grooves was examined. The effects of two storage solutions, formalin and sodium azide, on the bond of the glass-cermet were also evaluated. Sixty human molars were obtained and stored in either formalin or sodium azide. Thirty molars were prepared with one wall of tooth structure remaining, and the other 30 were prepared with two walls. Before being restored with glass-cermet, the preparations received either no retention, retentive grooves and pins, or retentive grooves only. Each preparation restored with amalgam received pins and grooves. Type III gold crowns were cemented in vitro with glass-ionomer luting agent, thermocycled 2500 times (5-50 degrees C), and then removed under a tensile force. The to amalgam and has adequate adhesion to the tooth, without additional retention, when at least two walls of the tooth remain. However, when only one wall of the tooth remains, the amalgam core is superior under tensile forces. There was a significant difference between the sodium azide and formalin storage solutions with regard to bond strength in one group (two walls, no pins, no grooves). In general, the cores placed on teeth stored in sodium azide exhibited tensile bond strengths lower than those stored in formalin.

Adhesiveness↗
PubMed1989

Comparative study of luting agents with composite resin cores.

This study compared bond strengths of zinc phosphate and polycarboxylate cements in cementing cast gold crowns to composite resin cores. The study also compared the effect of thermocycling on the bond strengths in tension of the two cements under varied storage and thermocycling conditions. Sixty standard cores were made from composite resin material. Gold alloy crowns were cast for each core and cemented with zinc phosphate or polycarboxylate cement. The samples were stored for 1 day or 1 month and then cycled with 60-second dwell times between 5 degrees C and 55 degrees C distilled water baths for 5, 100, or 1000 cycles. The controls were stored for the same periods and were not cycled. Overall comparison of both storage periods and all cycled and noncycled groups revealed that zinc phosphate cement had significantly higher bond strengths than polycarboxylate cement. Increasing the storage time before cycling significantly increased the bond strengths for both cements. There was no difference between any of the cycle periods or the noncycled controls for either cement.

Composite Resins↗
PubMed1989

Properties of a glass-ionomer/resin-composite hybrid material.

A small percentage of the liquid resin used in commercial dental composites was added to the liquid used in a commercial glass-ionomer restorative in order to produce a fluoride-containing hybrid restorative-type material that would adhere to dentin while being stronger, less brittle, and less sensitive to desiccation in the oral cavity than glass ionomer. Compressive strength, yield strength, elastic modulus, fracture toughness, and tensile strength were analyzed for this hybrid, light-cured material. In addition, the solubility in water, adhesion to dentin, and surface roughness were also examined in vitro. The results suggest that the early (one-hour) mechanical properties of the hybrid material exceed those of glass ionomer. In addition, the brittleness and solubility of the material are less than those of commercial glass ionomer, while adhesion to dentin is unaffected. Most importantly, surface crazing, a documented problem with some glass ionomers when they become desiccated, is alleviated with this hybrid formulation.

Composite Resins↗
PubMed1989

A comparative study of the bond strengths of amalgam and alloy-glass ionomer cores.

The purpose of this study was to compare the bond strengths of dental amalgam cores and dental alloy-glass ionomer cores that were luted to cast gold crowns with glass ionomer cement. Seventy-two human extracted molars were sectioned horizontally and four regular thread mate system pins were inserted into a flat pulpal floor. The teeth were restored with amalgam or alloy-glass ionomer admixture and prepared for crown preparations. Castings were produced with type III gold and cemented to the cores with Fuji type I glass ionomer cement. Thirty-six of the specimens were subjected to thermal fatigue by cycling between 4 and 50 degrees C for periods of 1, 5 and 10 weeks. The remainder of the specimens were retained in deionized water at 37 degrees C. Bond strengths of the cores, in tension, were measured with a universal testing machine. The alloy-glass ionomer cores exhibited higher bond strengths than the amalgam cores for virtually all time periods, particularly the thermocycled samples. The alloy-glass ionomer cores exclusively displayed core fractures and pin/tooth insufficiencies while the amalgam cores failed because of a deterioration of the glass ionomer luting cement.

Crowns↗
PubMed1988

Cytotoxicity of amalgams.

The purpose of this study was to compare the relative cytotoxicity of amalgams and to determine whether their toxicity depends upon composition and aging time, by means of a rapid and sensitive in vitro cell culture test. Zinc-containing amalgams showed higher cytotoxicity than did any other amalgams. High-copper amalgams had the same cytotoxicity as did the low-copper amalgam. The addition of selenium did not reduce the cytotoxicity of amalgam. Moreover, excessive additions of selenium increased the cytotoxicity of amalgam compared with that of a similar selenium-free material. The cytotoxicity of amalgam was decreased with aging time, possibly due to the combined effects of surface oxidation and further amalgamation.

Cells, Cultured↗
PubMed1987

A comparison of four modes of evaluating depth of cure of light-activated composites.

Four commonly used methods for evaluating depth of cure in light-activated composites were compared. Optical and scraping methods correlate well, but severely overestimate depth of cure as compared with hardness testing or degree of conversion analysis. Degree of conversion appears to be the most sensitive test of depth of cure.

Chemical Phenomena↗
PubMed1987

Variables affecting the fracture toughness of dental composites.

The fracture toughness of a variety of dental composites was evaluated using notched bending specimens, with and without pre-cracks. The pre-crack simulates more accurately a sharp, natural flaw in a material than does a notch, and is standard procedure in fracture-toughness evaluation. The fracture toughness was related to the filler composition and degree of conversion in the composite resins. In general, fracture toughness was highest in the more heavily filled resins, independent of degree of conversion in the matrix. The results also show that producing a pre-crack in certain composites reduced the value of their fracture toughness compared with notched-only specimens.

Chemical Phenomena↗
PubMed1987

Time-dependent dissolution of amalgams into saline solution.

The dissolution of mercury, silver, and copper from polished and unpolished surfaces of low- and high-copper amalgams into saline was investigated with respect to time via atomic absorption spectrophotometry. Greater amounts of mercury and silver were released from unpolished than from polished surfaces. Ion release was greatest during the first three hours after trituration of all amalgams. The rate of dissolution of ions from amalgams into saline is considered to be very low once the amalgam has set, and is probably inhibited by the formation of a surface film formed during immersion.

Copper↗
PubMed1987

Surface characterization of amalgams using X-ray photoelectron spectroscopy.

This study is the first to report on the use of x-ray photoelectron spectroscopy (XPS or ESCA) for studying the surface films (less than 10 nm thick) of aged amalgams. The concentrations and electron binding energies of the elements on the surfaces of four different amalgams aged for 20 min, one day, seven days, and 30 days were determined quantitatively. For comparison, the bulk compositions of the amalgams aged for seven days were also determined after removal of approximately 5 nm of material from the surface by argon-ion-sputtering. The XPS data revealed that the surface films of aged zinc-containing amalgams were not a simple oxide but were primarily composed of a (hydrated) tin and zinc oxy-hydroxide, whereas, in the zinc-free amalgams, the surface films were primarily a tin oxide. The concentration of mercury in this thin surface film after aging was depleted. This suggests that tin and/or zinc preferentially diffused to the surface and combined with oxygen, forming a surface film and diluting the mercury concentration in the surface. Another probable explanation for the depleted mercury is that a minimal amount of mercury in the surface film evaporated during the aging.

Copper↗
PubMed1986

The effect of resin formulation on the degree of conversion and mechanical properties of dental restorative resins.

The goal of this study was to determine the effects of resin formulation variables, such as diluent concentration, catalyst type and concentration and cure mode, on the degree of conversion of carbon double bonds and mechanical properties of dental restorative resins. Diametral tensile strength, compressive strength, hardness, flexural modulus and strength, and dynamic mechanical properties were tested, and the results were correlated to the degree of conversion results obtained by infrared analysis. The results showed a significant correlation between increased mechanical properties and higher degrees of conversion. Enhanced conversions were achieved by incorporating higher diluent and lower inhibitor concentrations into the resins. Ambient temperature properties were similarly enhanced by lower inhibitor concentrations, but were not enhanced by higher diluent concentration. Dynamic mechanical properties testing at oral and elevated temperatures elucidated possible differences in resin microstructure and network quality. The storage moduli decreased over the dental temperature range and was lower at all temperatures for resins with lower conversions. The glass transition temperature was also lower in resins with poorer conversions, suggesting that these resins may be more unstable at oral temperatures than more highly converted resins. Dynamic mechanical properties were most closely correlated to degree of conversion in these polymeric systems.

Acrylic Resins↗