33 research outputs found
Computer aided modelling to simulate the biomechanical behaviour of customised orthodontic removable appliances
In the field of orthodontics, the use of Removable
Thermoplastic Appliances (RTAs) to treat moderate malocclusion
problems is progressively replacing traditional fixed
brackets. Generally, these orthodontic devices are designed
on the basis of individual anatomies and customised requirements.
However, many elements may affect the effectiveness
of a RTA-based therapy: accuracies of anatomical reference
models, clinical treatment strategies, shape features
and mechanical properties of the appliances. In this paper, a
numerical model for customised orthodontic treatments planning
is proposed by means of the finite element method.
The model integrates individual patient’s teeth, periodontal
ligaments, bone tissue with structural and geometrical
attributes of the appliances. The anatomical tissues are reconstructed
by a multi-modality imaging technique, which combines
3D data obtained by an optical scanner (visible tissues)
and a computerised tomography system (internal tissues).
The mechanical interactions between anatomical shapes and
appliance models are simulated through finite element analyses.
The numerical approach allows a dental technician to
predict how the RTA attributes affect tooth movements. In
this work, treatments considering rotation movements for a
maxillary incisor and a maxillary canine have been analysed
by using multi-tooth models
A Coded Structured Light System Based on Primary Color Stripe Projection and Monochrome Imaging
Coded Structured Light techniques represent one of the most attractive research areas within the field of optical metrology. The coding procedures are typically based on projecting either a single pattern or a temporal sequence of patterns to provide 3D surface data. In this context, multi-slit or stripe colored patterns may be used with the aim of reducing the number of projected images. However, color imaging sensors require the use of calibration procedures to address crosstalk effects between different channels and to reduce the chromatic aberrations. In this paper, a Coded Structured Light system has been developed by integrating a color stripe projector and a monochrome camera. A discrete coding method, which combines spatial and temporal information, is generated by sequentially projecting and acquiring a small set of fringe patterns. The method allows the concurrent measurement of geometrical and chromatic data by exploiting the benefits of using a monochrome camera. The proposed methodology has been validated by measuring nominal primitive geometries and free-form shapes. The experimental results have been compared with those obtained by using a time-multiplexing gray code strategy