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Biomedical subjects

K F Leinfelder

Publications and source records attributed to K F Leinfelder.

At least 19 recordsLinked to original sources
PubMed1992

Methodology for proximal wear evaluation in posterior resin composites.

The purpose of this study was to utilize a methodology to measure proximal wear of posterior resin composites with respect to time. A group of 10 teeth (5 premolars and 5 molars) were restored with P-30, a posterior resin composite restorative. At placement the proximal contacts were judged to be closed visually, and with unwaxed dental floss. The patients were then recalled at intervals of 6, 12, and 36 months for indirect wear evaluations. Resin composite transfer copings were made and indexed on baseline models. A zoom stereomicroscope, at 20 microns resolution, was used to determine proximal wear. For the posterior restorative material the premolar and molar teeth wore at the same rate. The amount of wear was statistically greater for premolar teeth at 6 and 12-month evaluation periods than molar teeth. At 36 months, there was no statistical difference in wear between premolar and molar teeth.

Bicuspid↗
PubMed1992

Clinical evaluation of a heat-treated resin composite inlay: 3-year results.

The purpose of this study was to evaluate a resin composite inlay system in clinical trials involving human subjects. A total of 60 restorations were inserted equally in Class I and II preparations and in premolars and molars. A glass ionomer liner was applied to the dentin. Light-cured direct inlays were fabricated in the oral environment. Thirty inlays were heat-treated for 7.5 minutes at 125 degrees C in a dry heat oven. Enamel margins of the preparations were etched with 37% phosphoric acid gel. All inlays were cemented with a light-cured enamel bonding resin. Restorations were evaluated using the USPHS system and M-L indirect scale. Six, 12, 24 and 36-month recalls were compared to baseline. Color, interfacial staining, secondary caries, and wear were unchanged from baseline for all restorations. Marginal integrity and surface texture show a differential change from baseline and with respect to restoration type. Indirect wear was not significantly different between restoration types (P < 0.05). Wear resistance was not significantly improved with heat treatment, but marginal integrity and surface characteristics showed marked improvement in the heat-treated group at 24 and 36-month recalls.

Analysis of Variance↗
PubMed1992

Clinical microleakage evaluation of a cavity varnish.

This clinical study evaluated the microleakage effectiveness of a cavity varnish when used in combination with two types of amalgam: a spherical particle and a dispersed phase alloy. Calcium hydroxide was utilized as the microleakage detection agent. Copalite showed a reduction in microleakage when it was employed with the spherical particle alloy used in this study. This study clinically demonstrated that Copalite is not totally effective in eliminating microleakage.

Bicuspid↗
PubMed1977

Hardening of gold-based alloys.

The relationships between composition, heat treatment, hardness, and microstructure have been investigated for a number of commercial dental casting alloys and for several series of experimental gold-silver-copper compositions. The hardnesses and typical microstructures found are reported. The results indicate that at least two distinct hardening mechanisms must occur in these alloys. The ternary alloys outside the two-phasr region of the gold-silver-copper system harden by ordering. The commercial alloys and those within the two-phase region may harden in part by ordering, but some other mechanism in required to explain the observed hardening. This mechanism is not due to the observed grain boundary precipitates. It may be associated with the intragranular needlelike structures seen, but reasons exist to question the sufficiency of that structure as an explantation of the hardening.

Copper↗
PubMed1977

In situ replication techniques: I. Preliminary screening and the negative replication technique.

Fourteen commercially available elastomeric materials were investigated for their suitability as in vivo replication media. After a preliminary screening on an annotated specimen, three materials were chosen for further study. Of all materials evaluated, Xantopren Blue and Silene silicone impression materials provided the best results in vivo. This study demonstrates that a high resolution (ca 1 micron) negative replication technique may prove useful for the clinical evaluation of single-surface phenomena.

Acetates↗
PubMed1976

The effect of cold temperature mixing on the properties of zinc phosphate cement.

A series of proprietary zinc phosphate cements were evaluated after mixing on glass slabs at three different temperatures, 23 degrees, 6 degrees and -10 degrees C. Working time, setting time, diametral tensile strength, compressive strength and solubility were investigated. From the results of the tests the following conclusions were made: 1) As the temperature of the mixing slab was decreased, the amount of powder required to maintain a constatnt viscosity increased. 2) Compressive, tensile, and solubility values remained constant as the temperature of the mixing slab was decreased provided a consistent viscosity was maintained. 3) Mixing zinc phosphate cement substantially below the dew point is an acceptable practice provided the powder/liquid ratio is modified accordingly. 4) Although the setting time of zinc phosphate cement generally remained constant at temperatures below 6 degrees C, the working time continued to increase at -10 degrees C. 5) Mixing zinc phosphate cemment on a cold mixing slab increases the working time on the glass slab and decreases the setting time in an oral environment. Both of these alterations are clinically beneficial to the orthodontist.

Cold Temperature↗
PubMed1975

Permeability and porosity of dental casting investments.

Permeability of various gypsum- and phosphate-bonded investments was measured during conventional burn-out procedures. Porosity determinations were made on specimens cooled to room temperature after burn-out. As a group, the gypsum-bonded investments were found to be more permeable than the phosphate-bonded investments. Two phosphate-bonded investments were determined to be relatively impermeable to gas flow, while another exhibited permeability comparable to that of the gypsum-bonded investments. In spite of differences in permeability, the porosity of each type of investment was nearly constant. The porosity of the phosphate-bonded investment was approximately three-fourths that of the gypsum investments. These investments were modified by the addition of varying amounts of acrylic polymer for the purpose of altering permeability. The addition of acrylic polymer increased porosity and permeability of all of the materials included in this investigation. The acrylic additives, however, had no effect on the permeability of relatively impermeable investments unless used in high concentration. The results of this investigation would tend to substantiate the need for special spruing and venting procedures.

Acrylic Resins↗
PubMedDate not supplied

Three-year clinical evaluation of CAD/CAM restorations.

This study dealt with the clinical evaluation of 121 inlays and onlays generated from both Dicor ceramics and Vita porcelains. These two different types of ceramic materials were cemented using three different duo-cured composite resin luting agents, which differed in particle size. At the end of 3 years, no difference could be detected between the clinical performance of the Dicor and Vita restorations. Both exhibited the same degree of color matching characteristics, marginal integrity, and general clinical performance; however, seven of the restorations exhibited fracture through the isthmus, which was shown to be due to insufficient cavity depth. The balance of the restorations exhibited excellent clinical performance when evaluated against the United States Public Health Service System.

Aluminum Oxide↗