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Biomedical subjects

A Klocke

Publications and source records attributed to A Klocke.

9 recordsLinked to original sources
PubMed2006

Orthodontic springs and auxiliary appliances: assessment of magnetic field interactions associated with 1.5 T and 3 T magnetic resonance systems.

The objective of this paper is to evaluate magnetic field interactions at 1.5 and 3 T for 20 orthodontic devices used for fixed orthodontic therapy. Twenty springs and auxiliary parts made from varying ferromagnetic alloys were tested for magnetic field interactions in the static magnetic field at 1.5 and 3 T. Magnetic translational force F(z) (in millinewtons) was evaluated by determining the deflection angle beta [American Society for Testing and Materials (ASTM standard test method)]. Magnetic-field-induced rotational force F(rot) was qualitatively determined using a five-point scale. beta was found to be >45 degrees in 13(15) devices at 1.5(3) T and translational force F(z) exceeded gravitational force F(g) on the particular object [F(z) 10.17-261.4 mN (10.72-566.4 mN) at 1.5(3) T]. F(z) was found to be up to 24.1(47.5)-fold higher than F(g) at 1.5(3) T. Corresponding to this, F(rot) on the objects was shown to be high at both field strengths (> or = +3). Three objects (at 1.5 T) and one object (at 3 T) showed deflection angles <45 degrees , but F(rot) was found to be > or = +3 at both field strengths. For the remaining objects, beta was below 45 degrees and torque measurements ranged from 0 to +2. Of 20 objects investigated for magnetic field interactions at 1.5(3) T, 13(15) were unsafe in magnetic resonance (MR), based on the ASTM criteria of F(z). The implications of these results for orthodontic patients undergoing MRI are discussed.

Electromagnetic Fields↗
PubMed2006

[Children and adolescents: unequal living conditions, unequal health opportunities].

Today, children and young people represent the age group that is most frequently threatened by poverty in Germany. Poverty during childhood means a bad start to life and often has long-term effects on an adolescent's social and health development. Health problems are more frequent among preschool-age children from socially disadvantaged families. They are also more often affected by accidents and dental problems. In adolescence, links can be established between the social situation and psychosocial well-being, pain incidence and health behaviour. However, poverty does not inevitably go hand-in-hand with health problems. A stable and supporting social environment -- particularly in families, peer groups and schools -- promotes the development of a positive self-image and social skills, thus empowering the child to deal with demanding living conditions. Measures of social and health policy aimed at lessening the effects of poverty on health must start here.

Adolescent↗
PubMed2005

[Orthodontic brackets in high field MR imaging: experimental evaluation of magnetic field interactions at 3.0 Tesla].

PURPOSE: To evaluate static magnetic field interactions for 32 commonly used orthodontic brackets in a 3.0 T magnetic resonance imaging (MRI) system. MATERIALS AND METHODS: 32 orthodontic brackets consisting of a steel alloy (n = 27), a cobalt-chromium alloy (n = 2), ceramic (n = 1), ceramic with a steel slot (n = 1), and titanium (n = 1) from 13 different manufacturers were tested for magnetic field interactions in a static magnetic field at 3.0 T (Gyroscan Intera 3.0 T, Philips Medical Systems, Best, Netherlands). The magnetic deflection force F (z) [mN] was evaluated by determining the deflection angle beta [ degrees ] using the established deflection angle test according to the ASTM guidelines. The magnetic-field-induced rotational force F (rot) or torque was qualitatively determined using a 5-point grading scale (0: no torque; + 4: very strong torque). RESULTS: In 18 of the 32 brackets, the deflection angle beta was found to be > 45 degrees and the translational force exceeded the gravitational force F (G) on the particular bracket (F (z): 1.2 - 45.7 mN). The translational force F (z) was found to be up to 68.5 times greater than the gravitational force F (G) (F (z)/F (G): 1.4 - 68.5). The rotational force F (rot) was correspondingly high (+ 3/+ 4) for those brackets. For the remaining 14 objects, the deflection angles were < 45 degrees and the torque measurements ranged from 0 to + 2. The static magnetic field did not affect the titanium bracket and the ceramic bracket. No measurable translational and rotational forces were found. CONCLUSION: Of the 32 brackets investigated for magnetic field interactions at 3.0 T, 18 (56.25 %) were unsafe in the MR environment according to the ASTM guidelines. However, the forces measured were minimal compared to the forces generally necessary for dislodging these bonded orthodontic brackets from tooth surfaces. The implications of these results for orthodontic patients undergoing MR examinations at 3 Tesla are discussed.

Humans↗
PubMed2003

An optimized synthetic substrate for orthodontic bond strength testing.

OBJECTIVE: The purpose of this study was to investigate the suitability of different synthetic calcium phosphate based substrates as a biomimetic enamel surface model for orthodontic bond strength testing. METHODS: Carbonated apatite, amorphous calcium phosphate and commercial hydroxyapatite specimens were prepared as substrates for orthodontic bond strength testing. Carbonated apatite specimens were prepared by pressing, sintering and treatment with NaF. The shear bond strength was measured with a universal testing machine. RESULTS: Hydroxyapatite, amorphous and cold pressed carbonated hydroxyapatite exhibited fractures within the substrate after debonding. Mean bond strength values for carbonated hydroxyapatite were 7.38 (1.75) MPa for specimens pressed at 300 degrees C and 9.55 (2.23) MPa for specimens pressed at 300 degrees C and then sintered at 600 degrees C. An additional NaF treatment after sintering resulted in lower bond strength measurements of on average 6.52 (1.03) MPa. SIGNIFICANCE: Hot pressed and sintered carbonated hydroxyapatite showed acceptable shear bond strength values and may represent a suitable biomimetic model for orthodontic bond strength testing.

Apatites↗
PubMed2003

Synthesis, physical properties and preliminary investigation of hemocompatibility of polyurethanes from aliphatic resources with castor oil participation.

The synthesis of polyurethanes (PURs) from oligoetherdiol, two low molecular diols, castor oil and 4,4'-Methylenebis(cyclohexylisocyanate) is described. These polymers are characterized by measurements of the mechanical bulk and surface properties, preliminary investigation of compatibility with human blood and calcification in static conditions. The critical surface energy of synthesized PURs is similar to the critical surface energy of natural surfaces. Material-induced hemolysis and the changes of platelet counts in blood samples after contact with PURs are very low. Static seven-weeks-calcification testing in a synthetic calcification fluid did not indicate calcification by optical density measurements and by visual inspection and computer image processing of the X-ray films for PURs with and without castor oil.

Biocompatible Materials↗
PubMed2000

Influence of orthodontic appliances on myofunctional therapy.

Various removable and fixed orthodontic appliances were rated by interview and questionnaire by 42 myofunctional therapists in the Hamburg area with respect to their influence during myofunctional therapy. The Nance holding arch was given the most negative rating of all appliances covering the palate area. For the active plate, marking the rest position of the tongue by roughening the acrylic surface or by reproducing the palatal relief was considered beneficial. The quadhelix expansion device and Hyrax palatal expander were rated as unfavorable because of their positioning in the palatal area. Among the functional appliances, Fränkel's function regulator was given the best rating. Regular fixed appliances (brackets, bands) were not considered a disturbance. Habit reminders (plates and spurs) were given a very negative rating by ca. 80% of the therapists because they disturbed the myofunctional exercises and led to adaptive dysfunctions. Since many patients with dysfunction of the orofacial musculature undergo simultaneous myofunctional and orthodontic therapy, treatment planning and choice of orthodontic appliances should be carefully coordinated.

Attitude of Health Personnel↗
PubMed2000

Muscle activity with the mandibular lip bumper.

This prospective study was designed to measure muscle activity with lip bumper treatment. Surface electromyography was used to measure upper and lower lip activity with and without the appliance in place. Measurements were taken on a sample of 25 adolescent patients (age range, 10 to 17 years) before and after 12 months of lip bumper treatment. Recordings included a closed lip rest position, swallowing of water, and speech of the words "church," "phone," and "pop." Insertion of the lip bumper at the pretreatment recording resulted in significantly increased activity of the upper and lower lips at rest (P <.001) and while swallowing (P <.05), whereas the response for speech was variable. Pretreatment and posttreatment muscle activity measurements of the lower lip were compared to determine whether 12 months of treatment with the appliance resulted in muscle adaptation. The initial increase of muscle activity with insertion of the appliance for the closed lip rest position and for swallowing was not followed by a decrease during the treatment period. There were significant differences in muscle activity when comparing the "new" equilibrium introduced by the lip bumper to the "old" pretreatment equilibrium without the appliance. Although it was shown that the insertion of the appliance had a significant influence on muscle activity of the lips, the results of this study did not indicate adaptation of the lower lip to the appliance over the treatment period.

Adaptation, Physiological↗
PubMedDate not supplied

Cephalometric evaluation of children with Down syndrome after early intervention with the stimulating plate.

The aim of stimulating plate therapy in patients with trisomy 21 is to correct orofacial dysfunctions and prevent the establishment of subsequent morphological characteristics such as protrusion of the incisors and pseudoprognathia. This study investigated the effectiveness of this type of therapy in improving skeletal traits of patients with Down syndrome. The lateral cephalograms of 22 consecutive juveniles with Down syndrome, whose orofacial dysfunctions had been successfully treated with a stimulating plate according to Castillo Morales in infancy (17 months +/- 24 months), were examined 136 months on average (minimum of 78 months, maximum of 231 months) after initiation of treatment. In 16 of the 22 patients, the anomaly-typical bialveolar protrusion of the anterior teeth was diagnosed. The cephalometric results indicated larger values of cephalometric parameters concerning cranial base and maxilla, and markedly larger mandibular cephalometric values when compared to untreated children with Down syndrome. These results show that a stimulating plate may not always be indicated in patients with Down syndrome with a skeletal Class III pattern and minor orofacial findings.

Adolescent↗