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Biomedical subjects

S Dahm

Publications and source records attributed to S Dahm.

10 recordsLinked to original sources
PubMed1995

A method for testing denture adhesives.

An in vitro test is described that simulates the in vivo fate of a denture adhesive, namely destruction, dilution, and dissolution of the adhesive, by repeated measurement of tensile bond strength for the adhesive in isotonic saline over time. The bond strengths were measured under two different settings of the testing machine. The main compositions of three denture adhesive pastes, Fittydent, Fixodent, and Super Poli-Grip and one powder adhesive, Super Wernet's, were determined by infrared spectroscopy. The tensile bond strengths of these adhesives and those of pure tragacanth gum were subjected to a three-way analysis of variance. The Fittydent and Super Poli-Grip adhesives exhibited the best results over time. The most appropriate of the described methods for testing denture adhesives seem useful; however, when seen in relation to the results of a published clinical study where the patients were asked to evaluate the retention and the duration of some of these adhesives, there are indications that the clinical validity of the method might be improved if paste adhesives are tested at temperatures above 35 degrees C.

Adhesives↗
PubMed1995

The effect on the tensile bond strength of orthodontic brackets of titanium tetrafluoride (TiF4) application after acid etching.

Titanium tetrafluoride (TiF4) was applied to acid-etched enamel surfaces to study the effect on surface structure and tensile bond strength of orthodontic brackets. Three groups of 20 premolars each were compared in debonding tests. Group I received a 1% and Group II received a 4% topical TiF4 treatment after acid etching. Group III served as control, that is, no fluoride solution was applied to the enamel after acid etching. Each treatment lasted 60 seconds followed by a thorough rinsing with water for 30 seconds. Brackets were bonded on all teeth with the same procedure. All premolars were then placed in a water bath at 37 degrees C. Ten teeth from each group were debonded after 24 hours, and the remaining teeth were debonded after 6 months. Results indicated that the application of 1% and 4% TiF4 solutions on etched enamel surfaces did not alter the tensile bond strength significantly after 24 hours and 6 months. The scanning electron microscope (SEM) examination of the surface structure demonstrated the presence of extensive reaction products, which covered enamel surfaces and appeared to interfere with etch patterns. It was concluded that the application of TiF4 solutions to etched enamel surfaces before bonding will not have an adverse effect on the tensile strength of orthodontic attachments.

Acid Etching, Dental↗
PubMed1994

[The practical aspects of using "superelastic" arch wires in the edgewise technic].

Ever increasing refinements in orthodontic treatment and the corresponding increase in technical demands are challenges to both the dentist in his/her practice and to the manufacturers of orthodontic materials. One interesting development has been the introduction of "super-elastic" arch wires, which have now been on the market for some years. Such arch wires are characterized by an excellent "shape memory", various levels of super-elasticity, a remarkable hysteresis, and temperature sensitivity. On the basis of findings from temperature controlled tests of arch wires in a "Lloyd 1000 R" testing machine, the following conclusions can be drawn. Shape memory can, from a clinical point of view, be regarded as being a positive feature. "Super-elasticity" is of lesser value, because conventional activation of edgewise arches rarely reaches the level of deformation necessary for super-elasticity to be called into play. Hysteresis and temperature sensitivity make a biomechanical control of the arch wires difficult. Reducing active forces by chilling the archwire brings relief to sore teeth. Whether this possibly leads to an improvement in blood circulation in the periodontal tissue, which would be biologically advantageous, should be made the subject of further research.

Elasticity↗
PubMed1994

Clinical experience with minimal flow xenon anesthesia.

Xenon is a more potent anesthetic than nitrous oxide, and give more profound analgesia. This investigation was performed to assess the potential of xenon for becoming an anesthetic inspite of its high manufacturing cost. Seven ASA I-II patients undergoing cholecystectomy (n = 4), hernia repair (n = 2), or mammoplasty (n = 1) were studied. Denitrogenation by 15-20 min of oxygen breathing under propofol anesthesia was followed by fentanyl-supplemented xenon anesthesia administered via an automatic minimal flow system which held the oxygen concentration at 30%. Xenon anesthesia lasted 76-228 min and 8-14 l of xenon (ATPD) was used, of which 5.6-8.1 l was expended during the first 15 min. Anesthesia appeared to be satisfactory, and the patients woke up rapidly after xenon was discontinued. The automatic system made minimal flow xenon anesthesia easy to administer, but nitrogen accumulation is still a problem. Assuming a xenon price of 10 US$ per litre, the average cost for xenon was about 65 US$ for the first 15 min and then about 25 US$ for each subsequent hour of anesthesia.

Adult↗
PubMed1993

Tensile bond strength of orthodontic brackets bonded with a fluoride-releasing light-curing adhesive. An in vitro comparative study.

A light-curing, fluoride-releasing adhesive (VP 862, Vivadent, Liechtenstein) for bonding of brackets has been produced for inhibition of white spot lesions during orthodontic treatment. The tensile bond strength after 24 hours and 6 months was investigated and compared with two other light-curing adhesives (Transbond, 3M Corp., Monrovia, Calif., and Heliosit-Orthodontic, Vivadent, Liechtenstein) and two chemical-curing adhesives (Concise, 3M, Monrovia Calif., and Saga Bond, Saga Orthodontics, Kongsvinger, Norway). All adhesives produced adequate strength to be recommended for clinical use. The light-curing adhesives produced slightly lower bond strengths after 24 hours and 6 months, except Transbond, which showed an increase in bond strength in this period approaching the two chemical adhesives.

Adhesives↗
PubMed1976

The effect of grinding of human dentine examined by X-ray diffraction, infrared spectroscopy, and electron microscopy.

Analysis of human dentine by infrared spectrophotometry suggests that ball-grinding may result in damage of the apatite crystallites. The present study includes further assessments of this effect by X-ray diffraction, infrared spectroscopy, and electron microscopy. Each of three coarse-ground dentine samples (Group I) was divided into three portions of 30 mg. One of these portions was ball-ground for approximately 1 min (Group II), the second portion for 6 min (Group III), and the third portion for 23 min (Group IV). The 002 reflection showed line broadening, most marked from Group II to III. Electron microscopy showed a gradual change in crystallite appearance with increased grinding, most pronounced from Group II to III. These observations indicate that by prolonged grinding a limit is approached where no further changes in the crystallites occur. Electron microscopy also indicated that fracture of the crystallites might have occurred. This was probably accompanied by strains in the lattice. The infrared spectra indicated that no breakdown of the apatite structure had occurred during the entire grinding.

Apatites↗