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Biomedical subjects

D Nathanson

Publications and source records attributed to D Nathanson.

At least 55 records · Page 3Linked to original sources
PubMed1987

Shear strength of the composite bond to etched porcelain.

The shear bond strength of composite resin to porcelain was investigated to optimize variables for bonding porcelain laminate veneers. Scanning electron microscopy was initially used to examine the surface configuration of porcelain prepared under various conditions. A factorial experiment was undertaken to determine the effects of three different bonding methods on both etched and non-etched porcelain. Composite resin was bonded to the porcelain groups using (a) unfilled resin, (b) silane, and (c) silane with dentin adhesive. The results indicated a significant difference in shear bond strength for the three bonding groups, depending on the porcelain surface condition. For the unetched samples, significant differences in bond strength were obtained for all three bonding conditions. However, for the etched group, there were no differences between the silane and silane-with-dentin-adhesive groups. Porcelain etching significantly increased bond strength across all three bonding methods and was the main contributor to the obtained values.

Acid Etching, Dental↗
PubMed1984

An SEM study of posts cemented with an unfilled resin.

Post preparations in two groups of endodontically treated anterior teeth were completed. In Group I, the preparation was rinsed with 2 ml of 5.25% NaOCL. In Group II, the preparation was rinsed with 1 ml of 17% EDTA, followed by 1 ml of 5.25% NaOCl. A plastic post was fitted and cemented with an unfilled resin. After polymerization, the teeth were decalcified in 5% nitric acid. The decalcified structured was dissolved away with 5.25% NaOCl, leaving a model of the cemented post. This was examined by SEM to determine the extent of resin penetration into the dentinal tubules. In Group I, most of the post was smooth, and there was penetration only in small, random areas. In Group II, there was penetration into the tubules the full length and circumference of the post. Such penetration provides a very strong mechanical lock that enhances the tensile strength of the cemented post. Removing the smeared layer and then cementing a post with a Bis-GMA resin results in greatly increased tensile strength, even with shorter posts.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1983

Excessive wear of natural tooth structure by opposing composite restorations.

Extreme care must be taken to evaluate the probable effect of using certain restorative materials to oppose existing tooth structure, particularly when dentin is exposed. In addition, frequent recall examination, every one or two months, is necessary to catch any problems in their beginning stages and to solve them before greater damage can be caused. It is also suggested that evaluation of any occlusal habits be made before deciding on a plan to alter vertical dimension and to carefully consider the effects of the materials used in a restoration on the opposing arch.

Aged↗
PubMed1982

A new model of partial status epilepticus based on kindling.

In this experiment, a new model of partial status epilepticus (SE) is described which is based on the antecedent development of a kindled focus. Following kindling, the amygdala was stimulated continuously for 60 min with the previous kindling stimulus (60 Hz sine wave, 50 microA peak-to-peak). This treatment provoked SE in 22 of 35 rats. Without drug intervention, rats spontaneously recovered (SR group) from the seizure between 10 and 24 h. After recovery from SE, after discharge (AD) thresholds were elevated and remained so for the 2 weeks before sacrifice. The histologies of these SR rats indicated massive gliosis and degeneration of the ipsilateral hemisphere, extending from the medial olfactory bulb, through the amygdala-pyriform cortex to the ventral hippocampus. Damage was observed frequently in the midline thalamic nuclei and hippocampal CA1 fields. Interruption of the SE with Nembutal 30 min after the stimulation offset (30 Min group) was occasionally associated with slight gliosis at the kindled electrode, whereas interruption after 4 h of SE (4 Hr group) resulted in more extensive cell loss. The AD thresholds of the 30 Min group, like those of the rats which did not develop SE (NSE group), returned to near-normal values by 2 weeks after SE; only the NSE rats exhibited generalized seizures to their AD threshold stimulus. This model of SE results in brain pathology similar to that found in other models, but has the advantage of being uncontaminated by exogenous chemicals and toxins.

Amygdala↗
PubMed1980

Measurement of in vivo corrosion rates in baboons, and correlation with in vitro tests.

The Lineal Polarization Technique was used to determine the polarization resistances and corrosion currents of various dental restorative and implant alloys and amalgams placed in the teeth of animals, and as laboratory samples in artificial saliva. Gold- and chromium-containing alloys corroded the least, and amalgams generated the highest corrosion currents. There was good agreement between measurements made in vivo and in vitro. This is the first time that corrosion current have been measured in the mouth repeatedly over a long time span. These methods may be developed into useful predictive tests of in vivo corrosion.

Animals↗
PubMed1980

Periodontal splinting with wire and composite resin. A revised approach.

A method for periodontal splinting of anterior teeth with wire and composite resins is described. The method combines the use of a double wire reinforcement shallow tooth preparation, and acid etching to obtain good strength and sealing properties. The sequence of steps are exclusively designed to suit the properties of composite resins. The technique has the advantages of conservatism and simplicity, good esthetics and strength that surpasses that of conventional wire and acrylic or composite splints.

Acid Etching, Dental↗