Accuracy of fit of 3-to-3 retainers after adhesive fixation using a neodymium-iron-boron magnet chain.

Background And Objective: Six-base retainers are often used to prevent tertiary crowding. To minimize shear stress on the retainer, these should be fitted as precisely as possible. The aim of this study was to compare the accuracy of fit of 6-base retainers after adhesive fixation using a neodymium-iron-boron (NdFeB) magnet chain or a resin positioning aid.

Variations in cyclic mandibular movements during treatment of Class II malocclusions with removable functional appliances.

The aim of the study was to establish whether juveniles with a Class II malocclusion change the neuromuscular control of mandibular movements during the course of orthodontic treatment with removable functional appliances (RFAs). Neuromuscular control can be indirectly evaluated by recording cyclic planar mandibular movements which were freely carried out by the patients (28 girls, 14 boys, aged 11.1 ± 1.

Biomechanical aspects of mandibular growth.

The subject of this study was to analyse how functional parameters of stomatognathic systems are influenced by growth. For this purpose, two cephalometric radiographs of 65 patients with class-II-relation treated with functional appliances were superimposed on the occlusal plane. The two patient groups consisted of 32 open bite and 33 deep bite cases.

Functional state of the mandible and rolling-gliding characteristics in the TMJ.

For the physiological intact stomatognathic system, the three main functional states (occlusat articular functions, free mandibular movements, and ideal bolus function) were biomechanically discussed concerning the structure of movement, rolling-gliding characteristics, and force transfer in the temporomandibular joint (TMJ). In all three cases, rolling is not possible in the TMJ since the instantaneous rotational axis is positioned outside of the joint-rolling is not necessary because the TMJ is not loaded by appreciable forces. In the aged stomatognathic system with a lost discus and considerable Loads in the TMJ, however, the attrition of the joint is eased by rolling movement at the articulating surfaces.

The movement structure of the mandible and alignment of the neck.

The motion patterns of mandibular points were recorded in vivo in closed free movements of the mandible in the sagittal-vertical plane. The points ran along closed loops, which were evaluated by their area and length. All points whose loops showed areas of the same size regarding the sense of circulation formed straight lines.

The mandibularly fixed hinge axis--investigation of patients with sound and pathological jaws.

In former works, we had proved that test persons with sound temporomandibular joints (TMJs) used a mandibularly fixed hinge axis (MFHA) and were able to pilot the mandible by solely two kinematical degrees of freedom. We wondered if we could evaluate the MFHA the same way for patients who had problems with their TMJs. Actually, the MFHA could be determined likewise.

Aspects of morphology and guidance of the human temporomandibular joint.

Examinations of the curvature morphology of the temporomandibular joints (TMJs) in macerated human skulls yielded that in initial protrusive cranial border motion, parts of the condylar articulating surfaces are only functional under force transmission. These areas were found on the lateral-central side of the condyle. In contrast to the Cercopithecus mona, a monkey species, the human TMJ apparently possesses a distinctly higher spatial performance range.

Morphological structures and protrusive cranial border guidance of the temporomandibular joint of Cercopithecus mona.

Morphological parameters of the temporomandibular joint (TMJ) of Cercopithecus mona were analyzed by sagittal medial/lateral slicing of the entire joint. The slice contours of the osseous structures of the joint surfaces were approximated by circles. In this manner, the main parameter of the protrusive cranial border guidance, the protrusive dimeric Link chain (DLC), could be measured.

The influence of functional orthodontics and mandibular sagittal split advancement osteotomy on dental and skeletal variables--a comparative cephalometric study.

Lateral head films of 200 Class II patients (106 females, 94 males) with a mean pre-treatment age range of 9.9-10.25 years successfully treated with functional orthodontics were analysed before (T1) and after (T2) treatment.

The problems of borderline cases: an aid for the analysis of orthodontic therapies.

Our aim in this analysis was to create a conceptual aid for clinicians for use in dealing with and understanding the problems of borderline cases in general, and in making it easier to make medical and orthodontic treatment decisions. The doctor and patient now have a range of measures available for making a decision.

Biomechanical features of the periodontium: an experimental pilot study in vivo.

Introduction: The orthodontic application of a force or moment leads to a strain distribution in the periodontal ligament. The corresponding local deformation at the interface periodontal ligament-alveolar bone causes a distribution of normal and shearing tension that is thought to be the local stimulus for bone remodeling leading to orthodontic tooth movement. Although researchers have examined initial tooth movement and the biomechanical properties of the periodontal ligament, few have reported human, in-vivo studies.

The retention catalogue: an instrument for quality management.

Unlabelled: GOAL AND MATERIAL: We evaluated the clinical use of the "retention catalogue" employing a standardized questionnaire.

Results: Statistical evaluation of the standardized questionnaire demonstrated that the retention catalogue (RC) is an effective method in daily practice for orthodontists to convey patient information on the causes and prevention of relapses in crowding.

Conclusions: Routine utilization of the retention catalogue is recommended.

Biomechanics of the dental arch and incisal crowding.

During horizontal contact, the dental arch represents a link chain in which two convex articular surfaces are in contact and are tensioned by the dentogingival and dentoalveolar fibrous tissue. Joints composed of convex-convex surfaces are equivalent to stretched dimeric link chains whose links are in a mechanically unstable position under compression. Experiments on plaster models show that the dimensional stability of an articulated (dental) arch is considerably increased when a concave and a convex articular surface are in contact, as these joints are equivalent to an overlapping dimeric link chain whose links are in a mechanically stable position when under compression.

An experimental method for in vivo analysis of biomechanical asymmetries of the periodontium.

For analysis of the initial tooth movement in vivo, an optical measuring apparatus with a resolution of 0.001 degree for rotation or 0.5 micron for translation respectively has been developed.

Curvature morphology of the mandibular dentition and the development of concave-convex vertical stripping instruments.

Radii for concave-convex vertical stripping instruments can be derived from measurements of the natural curvature morphology in the horizontal contact area of the mandibular dentition. The concave-convex adjustment of contacts in the anterior dental arch with a newly developed set of concave-convex stripping instruments should enable orthodontic crowding problems to be alleviated biomechanically.