Search PubMed⌕ Search

Biomedical subjects

A Jäger

Publications and source records attributed to A Jäger.

At least 19 recordsLinked to original sources
PubMed1992

[An in-vitro study of the use of palatal arches in controlling the position of the upper molars].

An in-vitro study was performed analysing the forces and moments produced by the transpalatal arches of the Goshgarian type (0.036" x 0.032" stainless steel and and of the "Precision Lingual Arch System" advocated by Burstone (0.032" x 0.032" stainless steel and 0.032" x 0.032" TMA) using an electronic force-moment gauge recently developed by Planert. The palatal bars were adapted passively, and in addition, molar expansion, symmetrical molar rotation, and buccal root torque were applied. It was found that under clinical conditions it was impossible to fabricate an absolutely passive arch wire with any of the arch types under investigation. The highest precision in applying forces and moments together with the least side-effects was possible using the low stiffness TMA version of the Burstone system.

Biomechanical Phenomena↗
PubMed1992

[Analysis of isokinetic and isometric muscle function after arthroscopic anterior cruciate ligament repair].

Following anterior cruciate ligament replacement plasty performed via arthroscopy, isokinetic and isometric power data were measured at the beginning and end of a sports therapy treatment course. Evaluation yielded surprising results that were partly contradictory to those communicated in current literature. Besides the dependence of force values on preset velocities of motion in dynamic measurements (isokinetics) or in static measurements (isometrics), markedly lower losses of power than expected were measured in the involved extremity on repeated power application. Possible reasons are discussed on the basis of specific innervation criteria and polymodal reflexes. We assume that muscle potential is not yet fully available after surgical intervention, due to reflexive modulations of power realisation, so that the joint and especially the anterior cruciate ligament are thus protected from damage.

Adult↗
PubMed1991

Digital image processing techniques for cephalometric analysis.

This paper describes the application of digital image processing methods for better landmark identification in cephalometric analysis. Conventionally taken radiographs are captured by a video camera and processed by the IPS system (KONTRON). After a detailed analysis of the transfer characteristics of the image acquisition system, the algorithms for enhancing digitized cephalograms are described. The improvement of image quality is demonstrated by several examples. The limitations of video acquisition systems are discussed and possibilities for further development are indicated.

Cephalometry↗
PubMed1991

Comparison of 'normal' TMJ-function in Class I, II, and III individuals.

Fifty-seven non-orthodontically treated young adults, judged as either clinically healthy or with only mild symptoms of TMJ-dysfunction, were divided into groups according to their sagittal molar relationship (Class I-, Class II-, and Class III-group). All underwent a standardized clinical and axiographic examination with an axiographic recording device (SAS-SYSTEM). The comparison of the lengths of the axiographical protrusive curves showed significantly higher values in the Class II group than in the Class I (P less than 0.01) and in the Class I group than in the Class III group (P less than 0.001). Analogous differences could be found in clinical protrusive measurements at the incisal point and in lateral excursions. It was concluded that the protrusive condylar movement capacity coincides with the dental sagittal relationship. In opening, significant differences were seen axiographically (Class I v. Class III: P less than 0.001; Class II v. Class III: P less than 0.01), but not clinically. Since axiographic measurements show only condyle translation, but not rotation in contrast to measurements at the incisal point, it can be concluded that the differences in opening are also translatory and not rotational. Measurements of the average change of curvature of axiographic tracings showed significantly less curved protrusive tracings in Class III than in Class I (P less than 0.001) and Class II individuals (P less than 0.01), supporting the concept that in the Class III group condyle movement is restricted to the straight posterior slope of the tubercle.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Histomorphometrical study of physiological tooth movements in humans].

Quantitative analysis of remodeling activity was done using microradiographs of horizontal ground sections of human alveolar bone obtained from autopsies. The results demonstrated no significant age- or sex-dependent variations. The local distribution of remodeling activity in younger individuals pointed to a tipping mesial movement of the teeth. In older individuals this distribution showed a more random pattern.

Adult↗
PubMed1991

[Situation and extension of epithelial excrescences alongside the lip furrow band and the dental lamina].

3-D-reconstructions of serial sections of human embryos show that the margin of the lip furrow band is irregular and consists of an abundance of individual epithelial excrescences. Additional foldings of the lip furrow band extending over a length of up to 160 microns were found. The hypothesis that epithelial foldings in this region may be early anlagen of a perlacteal dentition is discussed and rejected.

Gingiva↗
PubMed1991

[Alveolar bone remodelling following orthodontic tooth movement in aged rats. An animal experimental study].

Orthodontic tooth movement of upper first molars was performed in twelve aged (500 days old) rats. It was demonstrated by histomorphologic findings as well as by vital polychrome staining that the remodelling process of the periodontal tissues in the aged animals was qualitatively similar to that in younger ones. The first molar in all animals was tipped mesially, while its mesial root was intruded. According to the vital polychrome staining the bone formation rate at the mesio-apical bone surface of the mesial root was determined as 7-8 microns per day. After 14 days comprehensive root resorption in the pressure zone distal of the bifurcation was found.

Aging↗
PubMed1991

Longitudinal study of combined orthodontic and surgical treatment of Class II malocclusion with deep overbite.

Twenty-one patients who had undergone orthodontic treatment in combination with mandibular advancement surgery to treat Class II malocclusion and deep overbite were followed up. Median vertical relapse at the bony chin (after a mean followup of 16 months) was found to be 2.9 mm (44%). Sagittal advancement was found to have good stability; most of the patients exhibited some additional anterior movement of the chin during the follow-up period. At the same time, the entire mandible rotated counterclockwise and the gonial angle increased. Individual response to treatment varied greatly; two patients exhibited major horizontal relapse. Controlling the position of the mandibular proximal segment seemed to be the most important factor in posttreatment stability of this sample.

Adolescent↗
PubMed1990

[Scanning electron microscopic research on the clinical use of interdental stripping].

The morphology of approximal enamel that has been stripped for therapeutic reasons was evaluated under the scanning electron microscope (SEM) twelve weeks and one year after treatment. In part one of the study the teeth were extracted before evaluation, in the second part replica were taken. For comparative reasons the morphology of the natural approximal enamel surface was evaluated under the SEM, too. After twelve weeks the edges of the furrows were seen to be smoother and plaque accumulations were found in the depths of the furrows. One year after there was found essentially no difference. In some of the specimens there was found a certain levelling of the edges in the approximal contact area, but not in the cervical region of the artificially abraded tooth surface. The natural enamel surface of the contact area showed excavations of similar size as the furrows that remain after stripping and finishing. But our study shows that the therapeutic approximal abrasion leaves furrows in the cervical region that even after one year had not undergone repair. The question is discussed, if thus predispositions for periodontal pathologies and caries could be created.

Bicuspid↗
PubMed1990

[Changes in the functional status of the stomatognathic system due to orthodontic multiband treatment in the adult].

Ten patients who undergo an orthodontic therapy with a full-band modified straight-wire-appliance were examined clinically and by means of an electronic axiographic device (SAS-system) at the beginning of treatment and after an average of 12.6 months, respectively. While the clinical functional status showed only minor changes, alterations of all examined axiographic parameters could be detected. This finding reemphasizes the necessity of modern axiographic means to get additional information about the functional status of the TMJ. The alterations point to a shift in the functional pattern of articular and muscular components during orthodontic treatment. In the majority of cases, axiographic parameters remained constant, however. In that respect, it might be of special interest that even uncoordinated tracings, mainly in the horizontal plane, kept up its characteristic appearance. These findings show clearly, that alterations of occlusal relationships must not influence articular functional patterns immediately.

Adult↗
PubMed1990

Semiautomatic method for histomorphometry.

A semiautomatic measurement system for histomorphometry is presented. The system is based on a steppermotor-driven scanning stage which the operator controls via a digitizer. Movement in the scanning stage is carried out with respect to stationary cross-wires in the ocular of the microscopy. The system is connected to a PC-AT computer which utilizes the x- and y-coordinates of these movements for the calculation of the morphometric measurements. In addition, the system is supplemented by software for storage and analysis of measurement data.

Diagnosis, Computer-Assisted↗
PubMed1990

[Growth of the facial skeleton and biomechanics of the stomatognathic system].

Biomechanical analysis of the stomatognathic system yields that the linkage between posterior and anterior guidance can be modelled by a link quadrangle (throttle crank) with closed linkage. Within this gear system the biochemical ideal position of the couple-line (functional length of the mandible) possesses a special meaning in centric occlusion: Along this line the gear system can be stretched without altering its essential mechanical properties. Interindividual comparison of the arrangement of mandibulary and maxillary structures related to the ideal initial position of the couple-line presents interindividual constants of arrangement and of growth. It is possible to define an individual, non-orthogonal system of coordinates. Its origin represents the individual center of growth. During growth special skeletally defined points run along radius vectors of this center. The rate of growth can depend on the angle between radius vector and couple-line.

Dental Stress Analysis↗
PubMed1990

[Effects of orthodontic expansion of the mandibular arch on the periodontal condition of the posterior teeth].

In the present study we examined the long term influence of orthodontic mandibular arch expansion therapy on the periodontal condition of the posterior teeth. 11 years after the end of treatment 31 former patients of our clinic were compared with a control group of matched age and sex distribution. Although we found some additional loss of periodontal attachment for the treated group this differences were not considered to be of clinical significance. Within the treated group the stability of the orthodontic treatment result seemed to be correlated with more favourable periodontal conditions.

Adult↗
PubMed1990

Quantitative determination of alveolar bone density using digital image analysis of microradiographs.

Horizontal 100 microns ground sections of 20 alveolar bone specimens from adult human mandibles obtained from autopsies were prepared for microradiography. Quantitative analysis of bone density of the alveolar cortex was performed using a semiautomatic digital image analysis system (KONTRON). The results demonstrated that bone density was higher in the lingual than in the labial alveolar cortex (p less than 0.05). In addition, the coronal portion of alveolar cortical bone was significantly more porous than the medical and apical ones (p less than 0.05). These variances were primarily due to increased canal size rather than to an increased number of canals. No significant age dependent changes in bone density could be determined.

Adolescent↗
PubMed1990

[The orientation of prisms in the dental enamel of human permanent teeth].

Enamel of human permanent teeth was sectioned and ground with 2 planes perpendicular to each other extending centrifugally from the dentino-enamel-junction to the crown surface. Prisms were made visible by acid etching before evaluation under the SEM. In the vicinity of the dentino-enamel-junction more prisms were found to be cut longitudinally, while close to the crown surface more prisms were cut transversely. In the perpendicularly ground plane the corresponding prisms were seen to deviate the more from the centrifugal orientation the more close they came to the crown surface. In a geometric model the angle under which the prisms deviate from the centrifugal orientation was calculated in dependence from the distance to the dentino-enamel-junction. The results correspond with the SEM-findings. We conclude that--since the prism diameter is today known to be constant--the form of the enamel mantle is created by a specific orientation of the prisms: They stand perpendicular at the dentino-enamel-junction, and the farther away they run towards the periphery the more they deviate from the perpendicular path. By this increasingly oblique orientation of the prisms the volume increment of the enamel mantle is created. The maximal angle of deviation is found morphologically and mathematically between 60 degrees-70 degrees at the crown surface. This arrangement of the prisms demonstrated by us is now seen to be the reason for erroneous assumptions about an increase of the prism diameter when ground sections were used. Because the prisms are oriented more and more oblique towards the periphery, correspondingly larger effective diameters must be produced while making ground sections tangential to the crown surface.

Dental Enamel↗
PubMed1989

[Bactericidal activity of enoxacin and ciprofloxacin in body fluids].

Until present studies are lacking which investigate the bactericidal activity of new quinolones in body fluids. Therefore, we determined bactericidal titers of enoxacin (en) and ciprofloxacin (cip) against a typical pathogen in urinary tract infections (Escherichia coli) in urine and against a typical pathogen in respiratory tract infections (Streptococcus pyogenes) in sputum, in each case at the time of peak and trough levels (In vitro data of the test strains: E. coli - MICen = 0.06 mg/l, MICcip = 0.06 mg/l, MBCen = 0.5 mg/l, MBCcip = 0.25 mg/l; Streptococcus pyogenes - MICen = 32 mg/l, MICcip = 1 mg/l, MBCen greater than 64 mg/l, MBCcip greater than 64 mg/l). Following a randomization list, ten healthy volunteers took either 400 mg enoxacin b.i.d. for three days, then (after a break of at least three days) 500 mg ciprofloxacin b.i.d. for three days, or vice versa. Two and 12 hours after the final dose, samples of sputum were taken, urine was collected 2-4 h and 10-12 h after the final dose. The bactericidal titers against E. coli in urine were greater than 1:512 (2-4 h after the final dose) and greater than 1:64 (10-12 h after the final dose) for both quinolones in all cases. On the other hand, as to S. pyogenes were found growth in every dilution of sputum. These results confirm the scepticism against quinolone therapy of respiratory tract infections caused by streptococci.

Ciprofloxacin↗
PubMed1989

[The results of scanning electron microscopy research on interdental stripping in vitro].

In an in-vitro study the abrasive qualities of different orthodontic finishing strips were evaluated on the enamel surfaces of human teeth by means of a scanning electron microscope. As a result we can state that even the use of the finest finishing strip cannot eliminate the deep furrows that resulted from prior abrasion with a strip that is more coarse. The remaining furrows caused by the abrasive procedure are so deep and wide, that plaque accumulation may well be expected therein, and thus be predisposing for caries and periodontal pathology.

Dental Enamel↗