Biomedical subjects

U Hirschfelder

Publications and source records attributed to U Hirschfelder.

At least 19 recordsLinked to original sources

PubMed2005

[Prognosis of the facial profile line using the finite element method].

AIM: The aim of the present study was to verify how realistic the prediction of the clinical appearance of the patient's profile is by using the finite element method to simulate orthodontic and surgical intervention. MATERIAL AND METHOD: This single-case study explains step by step interdisciplinary treatment planning in a case with angle class III. Orthodontic and surgical procedures can be simulated and visualized using the lateral cephalogram and the Onyx Ceph software. The facial profile line is calculated over the skeletal surface using the finite element method. The morphing feature of the Onyx Ceph software is used to create an image of the predicted appearance of the patient's profile using a preoperative lateral photograph. RESULTS: The comparison of the simulated profile and the clinical result after bimaxillary surgery showed high concordance. CONCLUSION: The finite element method represents a useful tool for the prediction of the postoperative appearance in patients undergoing fixed orthodontic appliance and orthognathic surgery.

Adult↗

PubMed2002

Long-term results of distraction osteogenesis of the maxilla and midface.

Since the beginning of 1998, eight patients have been treated by osteodistraction to correct hypoplasia of the maxilla and midface of various origins. Among them were five patients who were treated by high LeFort I osteotomies and insertion of subcutaneous intraoral distraction devices in the malar region. In the remaining three patients, extraoral distraction devices were applied after LeFort II and III osteotomies. Distraction osteogenesis was successful in all cases, resulting in a mean sagittal bone gain measured parallel to the skull base of 9.0 mm (range 4.5-12.0) in the group treated with intraoral distractors and a mean of 20.3 mm in the extraoral distraction group (range 15.0-25.0). All patients were kept under orthodontic supervision before, during, and after osteodistraction. Long-term cephalometric and clinical evaluation after a mean follow-up period of 24 months in the intraoral distraction group (range 22-26) and 12 months in the extraoral distraction group (range 10-14) show stable results concerning the skeletal and dental relations. Long-term follow-up is necessary.

Adolescent↗

PubMed2001

Distraction osteogenesis of the maxilla and midface using a subcutaneous device: report of four cases.

The use of distraction osteogenesis in the hypoplastic maxilla and midface is still controversial. Since the beginning of 1998, 25 patients have been treated with osteodistraction techniques for various reasons. Among them were four patients who were treated by high LeFort I osteotomies and insertion of a newly developed subcutaneous distraction device in the malar region. Distraction osteogenesis was successful in all four cases resulting in a mean sagittal bone gain of 12.0 mm (range 7-14) at the level of distractor fixation. All patients were kept under orthodontic supervision during osteodistraction. The final occlusal relation was satisfactory. Cephalometric measurements after distraction showed an anterior rotational movement of the midface region. As the question of relapse and further growth is still not clear, Delaire masks are used to stabilize the surgical result after removal of the distractor. The importance of long-term follow-up is stressed.

Adolescent↗

PubMed2000

Localization of lower right molars in a panoramic radiograph, lateral cephalogram and dental CT.

In this investigation, the radiological status of angular measurements in the wisdom tooth area was examined. The angles of the tooth center lines of the second and third lower molars (48, 47) to the occlusal plane and to one another in 25 orthodontically untreated patients (average age: 16.3 years) were measured and compared with angular values of the patients concerned measured in a dental CT. The assessment of these 3 radiological documents in an absolute comparison revealed closely corresponding angular values. However, the dental CT provided a considerably more accurate and, in addition, a three-dimensional topographical localization of lower wisdom teeth.

Cephalometry↗

PubMed1998

Treatment of Class II, Division 2 in the late growth period.

The "Deckbiss" with skeletal Class II jaw relationship sometimes presents a considerable therapeutic problem, particularly in the late growth period (DP3U), as regards the coordination of dental and skeletal treatment objectives. An effective treatment approach was demonstrated: a modified Herbst appliance used simultaneously with fixed appliances in the maxilla. The sample comprised 12 male (14.0 +/- 0.9 years old) and 10 female (12.3 +/- 0.4 years old) patients. Correction of the distal occlusion was achieved in all patients by means of the Herbst appliance, which was removed after an average time period of 6.4 +/- 0.2 months. In the mandible the multibracket appliances were then immediately inserted, and Class II elastics were used for retention. Maximum anchorage was required in the maxilla as well as in the mandible. Complete diagnostic records were made at the beginning of the treatment as well as 6 and 12 months later, in order to document skeletal and dental changes. A dental and skeletal Class I relationship was achieved in all cases. A significant improvement was recorded in the vertical jaw base relationship; this was still stable after a period of 12 months. In the dental area in particular, a so-called high-pull headgear effect (intrusion and distalization 16, 26) and intrusion of teeth 34, 44 were registered. Only a minor protrusion of the mandibular incisors was observed. Reinforcement of the bands reduced the failure rate significantly. The Herbst appliance does not represent a standard treatment for Class II. Its indication range is limited.

Adolescent↗

PubMed1998

Evaluation of the profile line in prognathic patients in the Saxony-Anhalt region of Germany.

The aim of the present study was to investigate the soft-tissue morphology and profile line of prognathic patients in the Saxony-Anhalt region of central Germany. To this effect, the profile photographs and lateral cephalograms taken at treatment start for 34 adults (17 female patients, mean age: 22.6 years; 17 male patients; mean age: 23.2 years), Class III subjects who had not undergone orthodontic treatment, were measured and, by means of statistical analysis, the findings were compared with those of an age-matched control group (17 female subjects, mean age: 21.4 years; 17 male subjects, mean age: 23.8 years). Patients with Class III anomalies had a significantly longer and thinner lower lip and a smaller lower subnasal angle than the control subjects. The lower face was markedly enlarged. Furthermore, the osseous profile line was significantly flatter and the soft-tissue convexity was considerably reduced compared with the control group. Hence the prognathic patients of central Germany manifested typical features of the prognathic profile line. To elucidate typical regional features, further comparative studies are required.

Adolescent↗

PubMed1997

Influence of facial growth pattern on outcome of extraction therapy.

The present clinical-radiological study analyzes orthodontic casts and lateral cephalometric X-rays (at start and finish of orthodontic treatment) of 56 extraction cases, most of them adolescent patients who had 4 teeth extracted. The test group was classified into 3 morphological categories according to growth patterns. For comparison purposes, cephalometric findings of morphologically matching non-extraction groups as well as corresponding data from the literature were used. There was no deepening of overbite in any of the extraction cases in the different test groups. However, an average bite opening of 1.2 mm was found in patients with a neutral or horizontal growth pattern. Irrespective of the growth pattern, a significant increase in anterior and posterior facial height as well as a mean reduction of the ANB angle between 0.9 degrees and 1.3 degrees was found in the different extraction groups. These results matched those of the corresponding nonextraction control groups. At the end of treatment, the longitudinal axis of the upper incisors appeared too steep (retruded). Overall, the individual growth pattern was found to be of very little relevance to treatment results, provided a well considered treatment plan had been drawn up.

Adolescent↗

PubMed1997

Evaluation of the bond strength of different bracket-bonding systems to bovine enamel.

In an experimental study the bond strength of stainless steel, ceramic and plastic brackets to bovine enamel was investigated by tensile testing. The brackets were cemented to the enamel using a conventional two-paste orthodontic bonding resin, a light-cured, fluoride-releasing adhesive, a no-mix-orthodontic bonding resin and a light-curing glass ionomer cement. For evaluation of the experimental data the Weibull analysis was applied. The highest values for the Weibull modulus (m) and the 10 per cent probability of failure (sigma.10) were found in the tested plastic brackets (Dentaurum Edgewise plastic bracket and Spirit bracket) using a no-mix orthodontic bonding resin (System 1). However, the tensile stresses for the 90 per cent probability of failure (sigma.90) were over 10 MPa and carried the danger of enamel fracture. Bracket bonding with glass ionomer cement cannot be recommended because of the low bond strength values for the 10 per cent probability of failure (sigma.10). The most favourable bracket-bonding system concerning the Weibull modulus (m), the 10 and 90 per cent probabilities of failure (sigma.10 and sigma.90) and aesthetics was the ceramic bracket with the silane-treated base (Allure III) using the light-cured, fluoride-releasing orthodontic bonding resin (Sequence). Bond fracture occurred predominantly between bracket and orthodontic bonding resin, with two exceptions. Concerning the ceramic bracket with the silane-treated base (Allure III) using the light-cured glass ionomer cement (Photac Fil), there was no preferential site of failure. Regarding the ceramic bracket with the silane-treated base (Allure III) using the light-cured, fluoride-releasing orthodontic bonding resin (Sequence), bracket fracture was seen more often than bond separation between bracket and enamel. When the bond failure was located at the enamel-orthodontic bonding resin interface enamel prisms could be identified on the adhesive site by scanning electron microscopy.

Adhesives↗

PubMed1997

Compomers--a new bracket bonding generation in orthodontics?

Compomers are a new class of materials. With the compomer Dyract Ortho., specifically for bracket bonding, and with Prime & Bond 2.0, a one-component primer for enamel and dentin, DeTrey/Dentsply has developed alternative new materials. The aim of this in vitro study was to test the tensile bonding strength of these materials with different kinds of brackets. Twelve test groups, each with 30 prepared bovine incisors, were formed. Two primers, Prime & Bond 2.0 and PSA, were used. 50% of all teeth were first etched will 36% phosphoric acid. Three types of brackets--metal, ceramic and silan ceramic--were bonded with the compomer Dyract Ortho. For 90 teeth forming a control group, the composite Concise was used. When conditioning the enamel with 36% phosphoric acid, the compomer Dyract Ortho showed a similar tensile bonding strength to the composite Concise. This was not the case if metal brackets were used. Metal brackets had significantly less tensile bonding strength (p < 0.001). The interface of the compomer with the bracket was the main failure site. There was insufficient retention between the compomer and the foil mesh of the bracket base because of the strong consistency of the compomer. Without enamel etching, Dyract Ortho produced an acceptable result only in combination with the primer Prime & Bond 2.0 and silan ceramic brackets. As insufficient data are available to date, the use of compomers in clinical practice cannot yet be recommended.

Animals↗

PubMed1995

[The importance of hand x-rays for the treatment of skeletal dysgnathias].

This study demonstrates the importance of X-rays of the hand in assessing skeletal changes in jaw relationships. The study is based on a follow-up examination of 53 patients with skeletal class II,1-, skeletal class II,2-, class III and skeletal open bite malocclusions who had been treated orthodontically. Statistical analysis of the growth parameters found a significant correlation between chronological age and skeletal age with considerable deviations depending on sex. At the end of the treatment period it was observed that 34% of all patients had not reached the end of puberty and had not achieved a mature level of growth. During the post-therapeutical period, growth was found on average to be 2.4% in the girls and up to 4.7% in the boys. When looking at the influence of growth and therapy, the patient group with skeletal class II,1 malocclusion exhibited at both therapeutical and post-therapeutical examinations a very positive development both in the horizontal and vertical basal relation of the jaw with a significant increase in mandibular length and in anterior lower facial height. On the other hand the class II,2 cases exhibited significantly reduced lower facial height, which can probably be considered to be a causal factor in the 70% relapse rate after completion of orthodontic treatment. In class III malocclusions the horizontal jaw relationship was stabilized throughout the orthodontic treatment period, however, following treatment a progressive alteration became apparent. The results achieved in this study add weight to the importance of taking skeletal maturation factors into consideration in patients with skeletal jaw discrepancies. These factors are useful in prognosticating the therapeutical goal to be achieved, the degree of stability during treatment, and the chances of relapse following treatment.

Adolescent↗

PubMed1994

[The diagnosis and treatment of congenital facial asymmetries in childhood. A clinical study].

Following a brief discussion of etiology, pathogenesis, and diagnosis of congenital facial asymmetries, a new interdisciplinary treatment concept encompassing the disciplines of orthodontics, maxillo-facial surgery, and pedaudiology is set forth. This concept calls for the surgical reconstruction of the mandibular ramus and of the temporo-mandibular joint already in childhood in those cases in which functional jaw orthopedics has already begun at an early age. Thereafter the occlusal plane can be corrected orthodontically. Six patients were treated according to this concept. Two years nine months after surgery favorable results were observed in relation to occlusion and mandibular growth. Because, however, long term results are still outstanding, the results obtained until now and the treatment concept remain the subject of ongoing critical study.

Child↗

PubMed1994

[Radiological survey imaging of the dentition: dental CT versus orthopantomography].

In this study 15 patients with abnormalities in dentition and jaws were analysed by computer tomography for the purpose of determining the diagnostic value of dental CT scanning in relation to orthodontic problems. The dental CTs were then compared with conventional panoramic x-rays. After describing principles and methodology, the study discusses the possibilities for clinical applications. The study demonstrated that dental CT scanning is definitely superior for diagnosing dentition disturbances, for metrical analysis of maxillary antrum relations, and for examining bony jaw structures. However, the routine use of dental CT scanning as a diagnostic method is at this time constrained due to the relatively high amount of time and labour the procedure requires with resulting implications for cost factors.

Child↗

PubMed1994

[An in-vitro study of the bonding and fracture pattern of light-hardening, fluoride-releasing bonding materials in metal brackets].

Three hundred bovine incisors, which were divided into 6 groups of 50 teeth each, were used in this study. Two types of metal brackets, 1 with a conventional foil mesh base and the other with a photo-etched Micro-Loc base, were adhered to the teeth with 3 different bonding agents, namely, Sequence, a fluoride-releasing, light-activated composite, Photac-Fil, a light-hardened glass ionomer cement, and, in the control group, Concise, a 2-component composite which hardens chemically. A universal testing machine was employed to test tensile bonding strength and the site of failure was visually determined and analyzed. The study showed that Sequence can be considered as a qualitatively equal alternative to Concise. Both composites demonstrate equal tensile bonding strength. The use of Photac-Fil, the light-hardened glass ionomer bonding agent, cannot be recommended. It possesses significantly less tensile bonding strength than the other 2 bonding agents. Sequence and Concise, which showed better results with the brackets with conventional foil mesh base than with the brackets with photo-etched Micro-Loc base, had no significant differences in their failure sites. The interface of the composite with the bracket was the main failure site. Both composites demonstrated a significantly reduced rate of failure at the interface of the composite with the enamel, when they were used with the brackets with the Micro-Loc base. This differed from the failure site of Photac-Fil, when the photo-etched base was used. With Photac-Fil the main site of failure came at the interface of the enamel with this glass ionomer cement.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

[Reconstruction of the lateral face in children].

Unilateral hypoplasia in the middle and lower face has different etiological causes. A standardized interdisciplinary treatment of children is demonstrated with the help of ten operated cases and nine children in observation. Depending on the missing structure of the anatomical regions the areas are reconstructed. A pre- and postoperative orthodontic treatment is part of the concept. With an operative intervention in childhood, it is possible to gain in most cases a more normal appearance till adulthood.

Adolescent↗

PubMed1993

[A critical evaluation of Class-II anomalies treated with functional orthodontic appliances].

In the course of a clinical and radiological follow-up study of 55 patients with class II malocclusions, who had been treated with functional appliances, the dental and skeletal changes were critically studies and statistically analyzed in relation to long term aesthetic, dental, and skeletal changes. Differences between class II, division 1 cases and class II, division 2 cases were also compared. The study revealed that at the end of the treatment period 80% of the functionally treated patients displayed much better nose to upper lip relations than at treatment begin. Aesthetically the best treatment results were in the class II, first group patients with an average 4.2 degree reduction of the soft tissue H-angle in the course of functional therapy. It was shown that both dental and skeletal changes were responsible fo the in most cases good treatment results, whereas the changes in patients in the two subgroups with class II malocclusions showed significant differentiations. This paper describes these changes in detail. Viewed in its entirety this study clearly supports the efficacy of functional therapy in adolescents. In relation to long-term stability the results of functional balanced occlusion and the stability of the maxillo-mandibular relationship should be especially emphasized, whereas the therapeutically induced protrusion of the mandibular incisors and their relapse should be critically viewed.

Adolescent↗

PubMed1992

[The functional treatment of deep bite--the results of a long-term study].

The amount of overbite reduction and the stability of the results three to 14.5 years post-retention were analysed in a follow-up study of 60 patients who had been treated with functional appliances. To establish therapeutic and posttherapeutic changes in dento-facial relationships, plaster casts and lateral cephalograms were evaluated at the beginning, at the end of treatment and at the follow-up examination. Posttherapeutic deepening of the overbite (> 0.8 mm) was found in 54.2% of the cases, while overbite reduction remained stable in 39%. A number of skeletal and dental factors were found to be involved in overbite reduction and posttreatment deepening. In this connection, changes in the ML-NSL angle, the ML-NL angle and the gonion angle were found to be just as important as the therapeutic and posttherapeutic changes in anterior and posterior facial height and changes in the skeletal pattern. It is emphasized that strict application of retention is of the greatest importance to minimize vertical relapse.

Adolescent↗

PubMed1992

[The spiral CT imaging technic--the initial experience for orthodontic examinations].

Within the course of the rapid development of CT technology, a new imaging technique, spiral computed tomography, is presently undergoing clinical testing. This procedure is based on a complete investigation of large volumes. In order to determine the suitability of this technique for the diagnostic evaluation of orthodontic problems, 25 patients were investigated. The most important advantage of this volumetric CT technique proved to be the capability of permitting complete recording of the object with only one scan, the extremely short examination time, and the associated reduction in radiation exposure, coupled with mostly improved image quality. These advantages, together with a discussion of various recording parameters and possible applications, are illustrated on the basis of typical cases. For orthodontic problems, the recording of small volumes provides the best three-dimensional surface reconstruction available at present.

Adult↗

PubMed1991

[Head posture in lateral roentgen image].

A cervico-cephalometric examination of 61 yet untreated orthodontic patients was performed in order to analyze differences in head posture between standardized cephalograms and lateral cephalograms taken in natural head position. Additional x-rays were taken in extreme flexion and extention of the head in 48 patients examining the mobility of the upper cervical spine. Finding partly large differences in cranio-vertical and cranio-cervical parameters between the two methods of registration it could be shown, that head posture on the average was more proclined in natural than in fixed standardized position. Subjects with class III malocclusion tended to a more extended head posture relatively to those with class I or class II malocclusion. Judging the atlas position with regard to the functional mobility of the upper cervical spine, a superior and inferior atlas position was not thought to be a pathologic fixed malposition.

Adolescent↗