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Biomedical subjects

H G Sergl

Publications and source records attributed to H G Sergl.

At least 19 recordsLinked to original sources
PubMed1995

[A holographic study to demonstrate the initial displacements of a macerated human skull under the influence of the orthodontic force from headgear with traction in different directions].

The phenomena of maxillary displacement and the subsequent growth modifications which result from the application of orthopedic headgear traction are very complex and not yet completely understood. The aim of this study was to investigate with the help of holographic interferometry the influence of the headgear's differing traction directions on the initial bone displacement in the maxillary complex. 560 g high, straight, and low pull headgear traction exerted above, through, and below the center of resistance of the upper first permanent molars was simulated on a macerated human skull and skeletal changes were recorded by laser holography as they occurred. On the basis of the frontal and lateral holograms thus obtained, the initial displacement of the maxilla, zygoma, and zygomatic arch in both horizontal and vertical planes was evaluated. Substantial displacements in various parts of the studied structures, displacements such as bending, relative deformation, rotation, and translation, were detected, and, further, the direction of this complex displacement often deviated from the direction of the influencing force. The results obtained by this study indicate that the initial 3-dimensional skeletal displacements brought about by the headgear are very complex. The clinical implication is that they do not always correspond with the direction intended by the force applied.

Child↗
PubMed1994

[An in-vitro study of 2 resins used in orthodontics for their cell toxicity].

The aim of this study was to examine in vitro cell compatibility of the orthodontic base resins Orthocryl (Dentaurum) and Wil-o-dont (Wilde) using the method described by Heidemann and Lampert (1980). The acute local nonspecific cytotoxicity of these materials and that of their individual components were evaluated. Used were both a qualitative microscopic assessment of cytopathological changes occurring in human gingival fibroblasts cultured along side the specimens and a semiquantitative assessment of the zones of inhibited cell growth around the specimens. Whereas Orthocryl and its components exhibited no toxic influence on the growth of the cultured cells, substantial cytotoxicity was observed in the tests of Wil-o-dont. The monomer and the adhesive component of this resin were found to be particularly toxic under the conditions tested. On the basis of the results of the study Wil-o-dont can not be given a clean bill of health in relation to the cytotoxicity of the product.

Cells, Cultured↗
PubMed1994

[A dental arch index related to tooth size and facial breadth].

Taking as its starting point the often postulated criticism of Pont's Index, the intent of the study was to develop a diagnostic procedure which took into consideration the objection that the Pont Index doesn't take the shape of the patient's skull into consideration. On the basis of the data obtained from the models and anthropological measurements of 50 adult subjects with fairly eugnathic dentition, the first step was to follow Pont and study which skull size exhibited the highest correlation to the posterior dental arch. Of all the relevant sizes the zygomatic arch width exhibited the highest correlation. Reference values for the posterior dental arch width, which were obtained with the help of regression analysis, which took into consideration both the total upper incisor width and zygomatic arch width as variables, were then established. These reference values were conclusively shown to have the best prognostic value. From this it can be concluded that a comprehensive orthodontic diagnosis should include an improved assessment of dental arch width.

Adult↗
PubMed1992

[Elemental analytical and quantitative morphometric determination of the synthetic resin residues and enamel avulsion after the removal of metal brackets].

A number of clinical and experimental studies were performed to assess the quality of the enamel-adhesive-bracket bond. The aim was to present a combined method that enables the investigator both to examine the surface of metal brackets quantitative-morphometrically and to detect the presence of enamel particles. To this end, 38 metal brackets were examined in the scanning electron microscope. An EDAX-detecting unit was used to analyze morphologically conspicuous structures and identified them as enamel particles. The extent of adhesive remnants and enamel particles was quantified using the image analysis system IBAS. In 24 brackets (53%) bonding adhesive residue was found on the bracket base. In 18 brackets (47%) enamel particles were identified on the adhesive-bearing brackets. This method is easier to carry out and enables a more accurate quantification of enamel particles than the Adhesive Remnant Index. Since it can be applied universally to examine recommended improvements to adhesive technique, it facilitates their assessment.

Composite Resins↗
PubMed1992

[A comparative study of the possibility of reducing the dosage in lateral teleradiographs].

Thanks to their capability for post-processing of image data, the digital radiological techniques introduced from 1970 onwards permit dose reduction with no loss of clinical information. The aim of this study was to establish the extent of possible dose reduction in orthodontic lateral cephalography. For this purpose, lateral cephalograms of a head phantom taken with varying radiation doses (5 to 150 mAs, constant 70 kV) were evaluated. The evaluations of ten judges were compared statistically. Conventional lateral cephalograms showed a statistically proven superiority of a number of exposure parameters for the sagittal and vertical localisation of reference points. This correlated with the radiological density of the structures. In contrast to the conventional technique, the reference points in all images obtained by digital luminescence radiography showed no such tendency. Digital luminescence thus meets the clinical need to reduce radiation dose (to about 20% of the usual dose) while providing no less diagnostic information.

Cephalometry↗
PubMed1992

[The demonstration of cellular reactions in the temporomandibular condylar cartilage by NMR microscopy. The basic research for high-resolution NMR tomography of the temporomandibular joint].

The regional resolution of modern imaging methods is not good enough to clinically objectify changes to the cartilage of the temporomandibular joint, for example in functional orthodontic treatment. NMR microscopic studies of an intact temporomandibular joint preparation were done experimentally in the domestic pig on the basis of 1H-NMR relaxometric measurements in specimens of condylar cartilage. We succeeded in representing the cartilage of the temporomandibular joint down to the cellular level, and in demonstrating regeneration processes as a late sequela of surgery on the temporomandibular joint. The results are discussed with respect to their importance for future high-resolution magnetic resonance imaging of the temporomandibular joint.

Animals↗
PubMed1992

Relations between verbal behavior of the orthodontist and communicative cooperation of the patient in regular orthodontic visits.

A study of interrelationships between orthodontist and patient communication characteristics on the basis of audiotape recordings is reported. The subjects were 66 patients from an orthodontic outpatient clinic who were treated by seven orthodontists. Strong relationships (partial correlations) were found between clinicians encouraging behavior (listener signals and symmetrical answering) and patient communicative cooperation (speech volume, detailed answering, questions, initiatives); whereas orthodontists guiding behavior showed lower correlations, only the clinicians' direct questions were significantly related to patient participation. For communication content, relations to patient activity depended on how strongly orthodontists discussed social or therapy topics. Discussion characteristics of both parties were not related to the patient's age, sex, and duration of therapy. However, patient communication differed with the personality of the dentist. Results are discussed with reference to literature, orthodontic consulting practice, and future research.

Adolescent↗
PubMed1992

On the prediction of dentist-evaluated patient compliance in orthodontics.

The aim of the present study was to determine to what degree social and psychological patient variables can predict orthodontic co-operation evaluated by dentists 3 and 6 months after the beginning of treatment. The subjects were 94 patients from seven orthodontic practices. They received a questionnaire with four subscales: impulsiveness, dominance, anxiety, and orthodontic attitudes. Compliance was assessed by an 11-item instrument based on the studies of Slakter et al. (1980). None of the social indices could predict co-operation, but the psychological scales for orthodontic attitudes, impulsiveness and dominance showed a significant relationship to later co-operation. The combination of all psychological variables (regression equation) could explain co-operation 3 months later to 12.1 per cent and to 16.8 per cent 6 months later. The implications for psychological guidance in orthodontics and future research are discussed.

Adolescent↗
PubMed1992

Morphological cephalometric differences between two European populations.

Earlier research in craniofacial morphology of the inhabitants of Mainz (Germany) and Zagreb (Croatia), who represent the populations of wider areas, have shown some roentgen-cephalometric differences. The aim of this study is to determine the craniofacial morphologic differences of these populations in three dimensions. The sample consists of 200 adult examinees, male and female respectively, inhabiting the mentioned areas. The sample has been chosen so that the examinees with prominent craniofacial anomalies have been excluded. Twenty three craniofacial parameters with the usual anthropometric instruments have been measured. The data have been processed by using elementary descriptive statistics and discriminant analysis. The results have shown that in Mainz examinees longer and narrower heads and higher faces in comparison with Zagreb examinees, predominate. Significant differences in forehead widths and bipupilar distances have been found.

Adolescent↗
PubMed1992

Disfigurement and psychosocial handicap of adults with extreme mandibular prognathism.

Questionnaires and psychological tests were used to assess the psychosocial impact of mandibular prognathism. Patients with mandibular prognathism were asked to assess the impediments caused by their dentofacial deformity. In addition, they were asked to rate their appearance and to report the effect that it had on their social contacts. The self-assessment revealed that patients felt esthetically impaired, but that they had a fairly positive autostereotype, as revealed by their self-descriptive choices on a personality scale. These results were compared with the assessments made by two different control groups composed of persons with no esthetic impairment. The attitudes of the control groups toward the patients were more negative than perceived by the patients, indicating that mandibular prognathism does result in a social handicap.

Adolescent↗
PubMed1991

[The morphological results of the use of a pulsed krypton fluoride excimer laser for enamel conditioning].

Although there have been many advances in the field of acid etching, major problems still present. For the most part, these are the unpredictability of the effects of etching, the lack of control of the depth of etching over the long term, and the development of enamel fractures occurring on debonding. The aim of this study was to investigate the morphological effects of enamel conditioning using a pulsed krypton fluoride excimer laser (wavelength 248 nm). Scanning electron microscopic examination revealed a surface similar to that produced by peripheral etching; no signs of thermal damage were to be seen. The requirements that have to be met by a modern laser considered as a possible alternative to conventional acid etching, are discussed.

Acid Etching, Dental↗
PubMed1991

[Comparative study of the accuracy of localizing cephalometric reference points in using digital and conventional imaging technique].

The purpose of this study was to present possible advantages of digital luminescence radiography for cephalometry. Conventional and digitalized lateral headfilms were compared and evaluated. The first impression of an improved simultaneous presentation of bony structures and soft tissue profile in digital x-rays was statistically verified. A significant difference in identification of several reference points was proven by means of the F-test. The superior results of the digital luminescence radiography were evaluated in comparison with xeroradiography and experimental postdigitalization of conventional x-rays.

Cephalometry↗
PubMed1991

[Perceptibility of details in conventional and digital teleradiography--a comparative study].

By introduction of rare earth film-screen combinations instead of classical screens dose reduction has already been possible. By this study the extent of dose reduction without loss of clinical information was to be examined by comparing conventional radiographic rare earth film-screen combinations to digital radiography. Statistical analysis proves for conventional lateral cephalograms that soft tissue reference points can better be localized if small radiation doses are used. The localization of reference points in areas of less radiographic transparency is better when applying higher doses. These results were not found in images by digital radiographic technique. Reference points both of soft tissue and of more dense areas of the skull were equally to be localized independent from radiation dose by the linear sensibility characteristics of digital radiography. This enables reduction of radiation doses and therefore a contribution to radioprotection.

Cephalometry↗
PubMed1990

[The relationship between different indicators of growth types].

In this study eleven variables were measured. These could be considered as indicators of the growth type or related to growth type. Together with a calculated combination measurement these variables have been correlated with one another. The correlations were interpreted and related to the type of growth.

Adult↗
PubMed1990

[How well can the growth type be evaluated?].

The purpose of this study was to determine to what extent growth type can be predicted using different information. Correlations between estimated values and those measuring cephalometric growth indicators revealed that the growth type can be evaluated reasonably well by merely viewing the cephalogram. The viewer is guided by form which is represented by the Go2 angle according to Jarabak. Growth type can also be evaluated from a profile photography. The assessment can be improved if one uses a wooden spatula to determine the mandibular and occlusal planes.

Adolescent↗
PubMed1990

[A comparative study of the craniofacial morphology of 2 ethnic groups].

The samples consisting of 200 latero-lateral cephalometric X-rays of examinees with nearly normal occlusion from Mainz are compared with homologous one from Zagreb. The purpose of the investigation was to point out the morphological differences in cranio-facial system. 19 variables were analysed by using essential statistic parameters and discriminative analysis. The results show the differences in the anterior face height, the lower border mandible inclination, the interincisal angle as well as the degree of face convexity. The average examinee from Zagreb, in comparison with the same one from Mainz, shows smaller anterior face height, the marked mandibular basal line inclination in the sense of the anterior rotation, the higher interincisal angle as well as smaller facial convexity.

Adolescent↗