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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

Rapid mixing of zinc phosphate cement for fixed prosthodontic procedures.

This study was done to determine the efficacy of rapidly mixing zinc phosphate cement in conjunction with fixed prosthodontic procedures. Properties measured included rate of pH change and temperature increase, film thickness, and setting time. The rapid mix technique in conjunction with the frozen glass slab resulted in a faster elevation of the pH but slightly greater temperature rise and film thickness. As was expected, the rapid mixing procedure resulted in an increased working time but decreased setting. On the basis of this study, it appears that the rapid mixing technique in conjunction with a frozen glass slab is an acceptable technique for preparing zinc phosphate cement for fixed prosthodontic procedures.

Cementation↗
PubMed1992

Degradation of microfilled posterior composite.

The substantial improvement in the chemical, physical and mechanical characteristics of posterior composites has contributed to their increased use in recent years. However, some troubling characteristics of these materials are their susceptibility to wear, marginal leakage, and recurrent caries. Numerous studies have dealt with the wear resistance of posterior composites. Only a few have investigated the mechanisms of failure, particularly those containing submicron-sized fillers. The purpose of this study, therefore, was to analyze the clinical characteristics of a posterior composite to determine the mechanisms responsible for marginal degradation. Using a series of optical standards, it was determined that the generalized wear-rate was linear, averaging 8 microns/year. Furthermore, it was shown that the marginal defect was cohesive in nature and that this type of defect, which is inherent in submicron-type posterior composites, was probably due to tensile fatigue failure.

Acrylic Resins↗
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↗
PubMed1992

Clinical evaluation of Clearfil photoposterior: 3-year results.

The purpose of this study was to evaluate a new resin composite/bonding restorative system in clinical trials involving human subjects. Sixty restorations were inserted in Class I and Class II preparations in premolars and molars. The enamel margins of the preparations were etched for 60 seconds with 37% phosphoric acid gel. The dentinal surfaces of cavity preparations were etched for 40 seconds with 37% phosphoric acid in glycerine (K-etchant gel) and bonding agent (Clearfil Photo Bond) applied. A resin composite (Clearfil Photoposterior) was placed in three increments with a 20 second light cure of each increment and a 60 second light cure of the final increment. All the restorations were evaluated using the USPHS system and M-L indirect scale. At 36 month recalls, compared to baseline, surface texture for essentially all the restorations was rated Bravo, while all other characteristics were rated Alpha. Secondary caries was reported for one restoration during the third year of clinical use. Wear showed an adjusted mean value of 14.6 microns at 36 months or 4.9 microns per year. No cases of clinical post-operative sensitivity to hot, cold, percussion and foods were reported during the length of the study. Clearfil Photoposterior resin composite system has exhibited remarkable wear resistance and no post-operative sensitivity throughout the length of the study.

Acid Etching, Dental↗
PubMed1991

Evaluation of various forms of calcium hydroxide in the monitoring of microleakage.

Calcium hydroxide has been shown to be an effective medium for the in vivo microleakage testing of amalgams. The purpose of this study was to determine the relative effectiveness of several forms of calcium hydroxide in the measurement of this clinical problem. It was also the purpose of this study to determine whether a relationship exists between the pH of the Ca(OH)2 liner and its ability to detect microleakage. Standardized Class V preparations were generated on the buccal surfaces of extracted molars. The axial walls of the preparations were based either with Dycal, Dycal VLC, Pulpdent Liquid, or pure Ca(OH)2. A series of teeth without a calcium hydroxide base served as the negative control. All teeth were restored with a spherical amalgam and kept in de-ionized water. The surfaces of the restorations were then subjected to 20 mL of 2 degrees C water for a period of one min. After three min, a color-indicating pH paper was positioned over the restored area for detection of the presence of hydroxyl ions at the amalgam/tooth interface. Regardless of the form of calcium hydroxide, all indicated extensive microleakage immediately after insertion of the restoration. In all cases, the number of samples generating positive results for leakage decreased over a period of time. The rate of decrease, however, was substantially dependent upon the form of calcium hydroxide used as well as its pH. The reagent grade of Ca(OH)2 generated the greatest percentage of positive results for the longest duration.

Calcium Hydroxide↗
PubMed1991

Five-year clinical study of u.v.-polymerized posterior composites.

Four u.v.-polymerized composites (Estilux, Nuva-Fil, Nuva-Fil P.A. and Uvio-Fil) were clinically evaluated in Class I and II cavity preparations in permanent teeth. The restorations were evaluated at baseline, 1, 2, 3, 4 and 5 years using USPHS criteria for direct evaluation and at 3, 4 and 5 years using the Leinfelder method for indirect evaluation of wear. The wear measured by the USPHS method showed increasing wear rates in earlier reports, apparently due to the limited sensitivity of the scale to early wear. The wear by the Leinfelder method showed gradually decreasing wear rates. There were no statistically significant differences among the wear values for the four u.v.-cured materials or between these materials and the self-cured and visible light-cured controls.

Analysis of Variance↗
PubMed1991

Using composite resin as a posterior restorative material.

Composite resins have been improved dramatically over the last few years. Some of the newest formulations are nearly as wear resistant as amalgam. Under the appropriate conditions, they may be used to restore Class I and Class II cavity preparations. Their use, however, must be in accordance with the conditions described in this paper. The following conditions should be followed: The selection of a posterior composite resin should be based on well-documented clinical data, not physical and mechanical properties. Complete moisture control is essential for the successful restoration of posterior teeth with composite resin. Always use a glass ionomer as a liner. The material should cover all the dentin. Cavity preparations should be minimal in dimension. Avoid unnecessary removal of tooth structure. Do not bevel the occlusal cavosurface margin. Insert the composite in increments. Minimize introduction of trauma during the finishing procedure. Use a surface penetrating sealant to reduce wear rate and to enhance margin integrity. Evaluate carefully the clinical performance of the restored tooth at least once a year. Discuss possible limitations of posterior composite resins as compared with amalgam restorations.

Bicuspid↗
PubMed1991

Dental amalgam alloys.

Dental amalgam, which constitutes nearly 75% of all restorative materials used in dental practice, has been used successfully for almost 150 years. Dental amalgam is low in cost, easy to use, consistent, and durable. Although amalgams have been challenged by more esthetic restorative materials and by fears of mercury toxicity, amalgams continue to be the materials of choice by most practitioners. This review discusses the advantages and disadvantages of amalgam alloys and predicts that one day, amalgam probably will be replaced by more esthetic materials that truly bond to all hard tooth surfaces.

Composite Resins↗
PubMed1991

Metallurgical evaluation of a copper-based alloy for dental castings.

The present study was designed to evaluate the metallurgical properties of an experimental, low-cost copper-zinc-aluminum-nickel alloy for dental castings. Some specimens were subjected to heat treatment after induction casting. The extent of corrosion was determined by measuring weight loss of specimens stored in a sodium sulfite solution. In the as-cast specimens, tests demonstrated the presence of three phases: the first consisted of copper-zinc-aluminum, the second was similar but lower in copper and aluminum, and the third consisted of an intermetallic compound of manganese-nickel-phosphorus. After heat treatment, the first phase remained relatively constant, the second was converted to Cu3Al, and the third increased in volume. The weight loss from the as-cast specimens was eight times that of the heat-treated specimens. It was concluded that the heat treatment substantially changed the microstructure and improved the corrosion resistance of the experimental alloy.

Copper↗
PubMed1990

Effectiveness of a method used in bonding resins to metal.

Currently, several methods are available for bonding resin veneers to dental casting alloys. Recently a new system (Silicoater) has been developed that involves the chemical bonding of polymers to dental substrates. This study determined bond strengths of several proprietary composite resin luting agents to three different types of casting alloys. The results were compared with those obtained using electrolytic etching techniques. The pyrogenically silica-treated specimens generated the highest bond strengths.

Acid Etching, Dental↗
PubMed1990

The effect of two smear layer cleansers on shear bond strength to dentin.

Prevention of microleakage and post-operative sensitivity depends upon maintenance of the integrity of the bond between the resin composite and the tooth. Removal of the dentinal smear layer allows for better bond strengths for the newer dentinal bonding agents. The purpose of this study was to evaluate the shear bond strengths of a light-cured composite to dentin treated with one proprietary and one experimental cleansing agent. Bond strengths for the teeth cleansed with the experimental cleansing agent were significantly (p less than 0.05) greater than bond strengths of teeth cleansed with EDTA.

Acrylic Resins↗
PubMed1990

The clinical evaluation of heat-treated composite resin inlays.

Laboratory research indicates the physical properties of composite resin used for posterior restorations can be significantly increased if a secondary dry heat treatment of the material was accomplished. This study investigated the clinical performance of a heat-treated composite resin inlay, using both the direct and indirect methods of clinical evaluation. Contrary to laboratory results, no significant differences in wear could be measured between conventional light-cured inlays and those with secondary dry heat treatment. Other clinical advantages of the heat-treated inlays were observed.

Analysis of Variance↗
PubMed1990

Effect of surface penetrating sealant on wear rate of posterior composite resins.

Although posterior composite resins have been improved considerably, secondary caries and wear continue to be a major concern. Recent studies suggested that microstructural defects such as voids and microcracks contribute to a weakened surface. The purpose of this study was to evaluate the effect of an experimental surface-penetrating sealant on the wear resistance of a posterior composite resin. At the end of 1 year, the rate of wear of the treated restorations was one-half of those not receiving the surface penetrating sealant.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1990

Comparison of dye and ion microleakage tests.

Basic fuchsin has been established as an effective testing agent in determining the extent of microleakage present under restorations. Recently, the presence of microleakage in vivo has been studied through the use of hydroxyl ions as is present in proprietary cavity liners such as Dycal. The purpose of this study was to determine a correlation between the use of these two systems in measuring microleakage. A series of restored human teeth containing a calcium hydroxide liner were thermocycled and then tested with pH indicating paper. The same samples were then given additional thermocycles in 0.5% basic fuchsin dye. The teeth were sectioned in two planes and ranked as to the amount of dye penetration. Over an 18-week period the number of positive pH tests began to diminish while the dye penetration values remained relatively constant. The dye penetration method continued to record microleakage after the pH paper had ceased to detect hydroxyl ions. The dye penetration method appeared to be more dependable as the age of the restoration increased.

Calcium Hydroxide↗