ROTATION JOINTS FRICTION IN A TRANSVERSAL MOBILE COUPLING

The transversal mobile couplings are used in movement and torque transmission between two main shafts having parallel axis, with the possibility to undertake misalignments in the transversal plane. These shaft misalignments are usually named transversal movements. The paper presents, starting from some kinematic aspects regarding relative movements between the coupling parts, the kinematic equations useful in determining position of the intermediary elements, depending by the transversal misalignments. Following this, using the inside relative movement in rotation joints between parts and corresponding adequate materials, the friction coefficient is studied. The friction which appears in coupling’s rotation joints between the involved parts has an important influence on their dynamic behaviour, wear and lifetime. The most significant friction and also wear is given by the alternant rotation movements in joints between parts, at the ends of their angular stroke. Due to this, the study of the friction between some materials to be used in coupling manufacturing is required, but also difficult because of some particularities, as reduced rotation in joints, for reduced transversal misalignments between the main shafts. There are presented, in the paper final part, the results and conclusions.

Retention period in children with crossbite

Relevance. Crossbite is a deformation of the dentoskeletal system in the horizontal (transversal) plane, and it results from a discrepancy between the width of the upper and lower dental arches in the anterior or posterior dentition.Crossbite can arise as an isolated condition, and then it is an independent de-formation of the dentoskeletal system. In some cases, a crossbite is combined with a wrong arch-to-arch relationship in the sagittal and vertical planes.The aim was to analyze the duration of the retention period in children with crossbite after the orthodontic treatment.Materials and methods. We orthodontically treated 18 children with crossbite aged 7 to 18 years. All patients were divided into 2 groups. Group 1 included 14 children from 7 to 14 years old with unilateral crossbite (right-sided – 6, left-sided – 8). Group 2 included 4 children from 9 to 18 years old with bilateral crossbite. All 18 children had a buccal crossbite. All patients underwent orthodontic treatment with removable and fixed orthodontic appliances.Results. The retention period after the orthodontic treatment of crossbite lasted 6-9 months.Conclusions. The analysis demonstrated that the retention period after the orthodontic treatment in children with crossbite averaged 6-9 months. The design characteristics of the or-thodontic appliances did not affect the duration of the retention period in children with crossbite.

Approximation of the Ribs-Bounded Contour in a Tomography Scan Slice

In this paper, a method for analyzing transversal plane images obtained by computer tomography (CT) scans is presented. A mathematical model that describes the ribs-bounded contour was created and the problem of approximation is solved by finding out the optimal parameters of the model in the least-squares sense. The paper discloses the problems that appear in building the proper model. Such a model would be useful in the registration of images independently on the patient position on the bed and of the radiocontrast agent injection. We consider the slices where ribs are visible because many important internal organs are located here: liver, heart, stomach, pancreas, lungs, etc. The model is flexible and describes the ribs-bounded contour independently on the patient age, sex and disease. The only exception is patients with the bone fracture. This makes the basis for the proper registration of slices.