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Biomedical subjects

A A Caputo

Publications and source records attributed to A A Caputo.

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

Effect of opaque porcelain application on strength of bond to silver-palladium alloys.

The opaque porcelain layer for porcelain-fused-to-metal restorations is critical for success. This investigation examined opaque porcelain application using one- and two-layer techniques with respect to their effect on the strength of bond to three silver-palladium alloys. There were no significant differences in the flexural bond strengths of the three alloys for the one- and two-layer opaque application techniques. With respect to bond strength, these results afford flexibility in the choice of the one- or two-layer techniques.

Dental Alloys↗
PubMed1990

Altered corrosion resistance from casting to stainless steel posts.

Heat treatment during the burnout procedure may cause corrosion of the stainless steel post. This study was undertaken to determine whether alteration of the corrosion resistance of stainless steel posts occurs as a result of various simulated burnout procedures. Stainless steel posts were divided into five groups of five posts: group 1, control; 2, gypsum-bonded investment, bench cooled; 3, gypsum-bonded investment, quenched; 4, phosphate-bonded investment, bench cooled; and 5, phosphate-bonded investment, quenched. The posts were placed in individual containers of Ringer's solution and observed at 30, 180, and 600 days. Scanning electron microscopy, energy dispersive x-ray spectroscopy, optical emission spectroscopy, and optical microscopy were used to evaluate the posts qualitatively and quantitatively. Investment and heat treatment altered the metallic structure of stainless steel posts. Prefabricated posts submitted to simulated burnout procedures had a noticeable reduction in corrosion resistance. Direct casting to stainless steel posts is contraindicated.

Corrosion↗
PubMed1989

The strength of layering technique in visible light-cured composites.

Despite the extensive use of the layering technique in light-cured restorations there is limited information for the interfacial strength when curing is accomplished in air and an inhibited zone is formed on the first layer. This study analyzed the nature of the inhibited zone to determine the interfacial topography, evaluated the shear interlayer bond strength in the presence of the inhibited layer, and assessed the effect of various interfacial treatments on bonding. Two microfilled, one hybrid, and three small-particle composite resins were included in the study. According to the results, the inhibited zone is primarily composed of catalyst-free monomer. The presence of this zone reduces bond strength, creating interfacial discontinuities. Removal of the inhibited layer by an organic solvent of low boiling point results in the highest strength and better interfacial topography from the tested treatments.

Chemical Phenomena↗
PubMed1989

Photoelastic analysis and comparison of force-transmission characteristics of intracoronal attachments with clasp distal-extension removable partial dentures.

This investigation photoelastically compared the load-transfer characteristics of various bilateral distal-extension removable partial denture designs embodying intracoronal attachments and clasp assemblies. Six distal-extension designs that included the RPI clasp assembly, cast circumferential clasp, P.D. locking semiprecision, Thompson dowel nonlocking semiprecision, and McCollum and Stern G/L precision attachments were tested. Each prosthesis was subjected to various simulated occlusal loads. Evaluation of the load-transfer characteristics of the various designs was based on comparison of the recorded isochromatic fringe distributions. The RPI clasp assembly generated the most uniform stresses. In general, the four intracoronal retainer frameworks produced higher stresses than did the two clasp frameworks. The highest stresses were developed by the Stern G/L precision attachment.

Bicuspid↗
PubMed1989

Interaction between the dentinal smear layer and composite bond strength.

Freshly extracted human molars were used to study the interaction between dentinal smear layer removal with various agents, a dentinal adhesive, and the shear bond strength of a posterior composite resin to dentin. The use of Scotchbond dentinal adhesive in conjunction with the composite P-30, with the smear layer intact, produced the highest shear bond strengths. Removal of the smear layer produced bond strengths similar to those obtained with the smear layer intact. Application of ferric oxalate, and to a lesser degree 17% EDTA, resulted in diminished bond strengths. It was concluded that optimal bond strengths with the adhesive-composite resin systems tested may be obtained with an intact smear layer.

Adhesives↗
PubMed1989

A comparative in vitro study of visible light-cured sealants.

The introduction of visible light polymerization in dentistry led to the development of a new generation of pit and fissure sealants. The purpose of this study was an overall evaluation of some in vitro characteristics of four new sealants (Delton LC, Helioseal, Pentra-Seal and Visioseal) in comparison with a chemically cured control (Delton). The results indicate that the monomer systems utilized in the new materials have already been used in dental polymer technology. The relatively new monomers TCDDMA/TCDMA were identified in one product. Camphoroquinone is used as a photoinitiator in all the light-cured systems which, after 40 s exposure, present better conversion than the control. The extent of oxygen inhibition was considerably reduced in the new sealants and the surface hardness was enhanced. Great differences were obtained in the penetration coefficient values; these, however, did not affect the enamel retention capacity of the materials tested. Consequently, light-cured sealants should be considered to be strongly compatible with the conventional chemically cured sealants from a laboratory aspect until more clinical evidence is available for their effectiveness in the prevention of pit and fissure decay.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1988

Effects of cooling methods on silver-palladium castings.

Cast metal specimens for three ceramic metals were subjected to two different types of cooling procedures after casting. One method involved the rapid cooling of the casting as soon as the red glow of the button disappeared. The other method allowed the castings to bench cool to room temperature. Hardness, bond strength, and microstructural determinations lead to the following conclusions. 1. Vickers hardness values for W-1 and Rx-91 alloys for each cooling regimen were not significantly different. Statistically higher hardness values were obtained for the quenched specimens of JP-5 alloys compared with the bench-cooled specimens. 2. Cooling of W-1 and JP-5 alloy specimens by quenching resulted in higher bond strengths than for specimens that were bench-cooled to room temperature. However, bench-cooling Rx-91 alloy lead to higher bond strengths than did quenching. 3. For all of the alloys examined, quenching produced a smaller grain structure than did bench-cooling. 4. From the standpoint of the parameters tested and the saving of processing time, quenching of the silver-palladium ceramic alloys examined is the cooling procedure of choice for W-1 and JP-5 alloys.

Dental Alloys↗
PubMed1988

The interaction of a magnetically retained denture with osseointegrated implants.

A replica of an atrophied mandible was constructed in which two Brånemark implants were embedded to simulate osseointegration. Ferromagnetic keepers were then attached to the implants. A complete overdenture was constructed which had magnets positioned directly over the keepers. The denture was then subjected to different loads and the stresses were photographically recorded. The denture was also tested for its retention capabilities. Because of the equitable stress distribution with the absence of high foci of concentration, a magnetically-retained overdenture with osseointegrated supports lends itself well as a prosthetic replacement. In addition, the magnets exhibit sufficient retention without unduly loading the implants or residual ridge. It may be concluded that in a similar in vivo situation, magnets could be an alternative to other attachment systems; however, there are many variables to be considered on an individual patient basis.

Bone Resorption↗
PubMed1988

Light cured composites.

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Bisphenol A-Glycidyl Methacrylate↗
PubMed1986

Magnetizable abutment crowns for distal-extension removable partial dentures.

A study of the retention and load-distributing characteristics of bilateral distal-extension dentures with magnetizable abutment crowns revealed the following findings: Comparable retention was obtained with the horizontal and oblique pedestals. Decreased retention was noted when there was space between the magnet and pedestal. The retention values were substantially higher than reported values for the I-bar retainer. For the space and no-space situations, the horizontal pedestal design provided better stress results than the oblique design. Better stress-distributing properties for horizontal and oblique pedestals were obtained with the presence of a space between the magnets and pedestals. Of all the designs tested, the horizontal pedestal with a space demonstrated the best load-transmission characteristics.

Dental Abutments↗