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Biomedical subjects

O Barwart

Publications and source records attributed to O Barwart.

6 recordsLinked to original sources
PubMed1999

An evaluation of the transition temperature range of super-elastic orthodontic NiTi springs using differential scanning calorimetry.

Differential scanning calorimetry (DSC) was used to determine the transition temperature ranges (TTR) of four types of super-elastic orthodontic nickel-titanium coil springs (Sentalloy). A knowledge of the TTR provides information on the temperature at which a NiTi wire or spring can assume superelastic properties and when this quality disappears. The spring types in this study can be distinguished from each other by their characteristic TTR during cooling and heating. For each tested spring type a characteristic TTR during heating (austenite transformation) and cooling (martensite transformation) was evaluated. The hysteresis of the transition temperature, found between cooling and heating, was 3.4-5.2 K. Depending on the spring type the austenite transformation started (As) at 9.7-17.1 degrees C and finished (Af) at 29.2-37 degrees C. The martensite transformation starting temperature (Ms) was evaluated at 32.6-25.4 degrees C, while Mf (martensite transformation finishing temperature) was 12.7-6.5 degrees C. The results show that the springs become super-elastic when the temperature increases and As is reached. They undergo a loss of super-elastic properties and a rapid decrease in force delivery when they are cooled to Mf. For the tested springs, Mf and As were found to be below room temperature. Thus, at room temperature and some degrees lower, all the tested springs exert super-elastic properties. For orthodontic treatment this means the maintenance of super-elastic behaviour, even when mouth temperature decreases to about room temperature as can occur, for example, during meals.

Body Temperature↗
PubMed1996

The effect of temperature change on the load value of Japanese NiTi coil springs in the superelastic range.

Japanese nickel-titanium (NiTi) coil springs exhibit superelastic properties similar to the properties of Japanese NiTi wires. The springs exert a constant light, continuous force over a long range of increasing or decreasing activation. This property enables the springs to be used for physiologic orthodontic movement of teeth. A constant load value can be maintained only at constant temperatures. However, external influences affecting the mouth, for example when eating or drinking, cause fluctuations in temperature, which can be considerable. In this study, the effect of temperature change on the force delivery of NiTi springs in their superelastic range was investigated. Japanese NiTi closed coil springs were heated and cooled between 20 degrees C and 50 degrees C, while held in constant extension. During this procedure, the force was continually recorded. Commercially available stainless steel closed coil springs were tested in the same way. For all the springs examined, load values were found to increase with rising temperatures and to decrease with a drop in temperature. This relationship between temperature change and load was more pronounced in the case of NiTi than in the steel springs. The force measured at 37 degrees C was about twice as high as at 20 degrees C for one type of NiTi spring. On cooling, the superelastic springs showed unusual behavior. Immediately after the temperature started to drop, a rapid decrease in force occurred to levels below those found at rising temperatures. Such a nonlinear decrease in load was not observed in the stainless steel springs tested. The findings demonstrate that only minimal changes in temperature can cause significant changes in the force delivery of superelastic NiTi springs.

Analysis of Variance↗
PubMed1995

[The oral health status of emergency dental patients in Austria].

It is often suggested that people who require emergency dental treatment are mainly those who do not care about their teeth and do not have regular visits to their dentist. Little is known about their dental health. Therefore a study was initiated to get more information on the oral health state of these people. The dental care for these patients could be improved selectively in future. 1214 patients using the emergency dental service at the University Clinic for Dentistry in Innsbruck/Austria where examined. More than 40% of these patients had untreated dental caries. Remnants of teeth, as the result of carious destruction, were found in 13.3% of these people. The (dt+DT) value was 2.4 at the age 3-12 years. 6.5 teeth on average were missing at the age 35-44 and about 40% of these patients did not wear a dental appliance for replacement of missing teeth. The emergency dental service was used most frequently by people aged 25 to 35 years. It can be assumed that especially this age-group does not care enough about their teeth. Therefore an effective dental health service including these people as well as some certain profession-groups which were found in this study to stand out by reduced oral health could improve the oral health by economically justifiable costs.

Adolescent↗
PubMed1994

[The functional evaluation of orthodontically aligned impacted canines].

The purpose of this study was to examine functional occlusion of impacted maxillary canines which had been moved orthodontically into the line of occlusion. Examinations were performed on both patients and on an articulator, which was adapted to correspond to the axiographical findings. Functional contacts on the working side during lateral movement of the mandible were found in all orthodontically aligned impacted canines. Half the aligned teeth were involved in canine guidance, half in group function. Balancing side interferences were detected in 22% of the cases. The result of this study revealed a nearly identical function in the aligned canines when compared with the spontaneously erupted canines on the other side of the same maxilla. This became apparent during lateral excursion of the mandible. The angle of mesiodistal inclination of the tooth central axis with an occlusal plane was 84 degrees for aligned and 82 degrees on average for the spontaneously erupted canines.

Adolescent↗
PubMed1991

In-vitro study to compare the efficacy of N-monochloro-D,L-2-aminobutyrate (NMAB, GK-101E) and water in caries removal.

The present in-vitro study was designed to investigate the chemical efficacy of N-monochloro-D,L,-2-aminobutyrate (NMAB, GK 101E) in removing carious material under clinically relevant conditions, using objective methods of measurement. Assuming that the chemical effectiveness of water in caries removal is minimal, a comparison of the efficacy of GK-101E with that of water was made. The force required to achieve complete caries removal from symmetrically separated carious lesions was determined with the Caridex system, modified by a force gauge. One lesion half was treated with GK-101E, while the corresponding half was treated with water. Thus a difference in the chemical potential of the fluids in softening carious material should lead to a difference in the force required to remove equal quantities of caries. Statistical analysis of the findings of the present study revealed no significant difference between GK-101E and water, with regard to both the force and the number of excavation strokes and the time needed for caries removal. It is concluded that, under the given test conditions, the removal of carious dentine is not significantly enhanced by the chemical action of GK-101E.

Aminobutyrates↗