O. Etxaniz

Direct transfer of the position of digitized casts to a virtual articulator

This article describes a digital technique to transfer the location of digitized casts obtained directly from the patient to a virtual articulator (digital/virtual facebow transfer). The primary advantage of this technique is that it allows the dentist and the dental laboratory technician to work in a fully digital environment without having to mount stone casts on a physical articulator. This results in a significant time reduction and a higher degree of accuracy in the cast location.

Improved digital transfer of the maxillary cast to a virtual articulator

The clinical procedure described provides a quantifiable, repeatable, and reliable method of transferring the location of the maxillary dental arch from the patient directly to a virtual articulator (virtual facebow transfer) by means of reverse engineering devices to design a customized dental restoration. This procedure allows the dentist and the dental laboratory technician to work in a fully digital environment without having to mount stone casts on a mechanical articulator. In addition, specific suggestions are provided for designing the transfer device to enhance patient comfort during the data transfer process and reduce deviation.

Computer-aided dental prostheses construction using reverse engineering.

The implementation of computer-aided design/computer-aided manufacturing (CAD/CAM) systems with virtual articulators, which take into account the kinematics, constitutes a breakthrough in the construction of customised dental prostheses. This paper presents a multidisciplinary protocol involving CAM techniques to produce dental prostheses. This protocol includes a step-by-step procedure using innovative reverse engineering technologies to transform completely virtual design processes into customised prostheses. A special emphasis is placed on a novel method that permits a virtual location of the models. The complete workflow includes the optical scanning of the patient, the use of reverse engineering software and, if necessary, the use of rapid prototyping to produce CAD temporary prostheses.

Customized procedure to display T-Scan occlusal contacts

The virtual technique described in this article integrates reverse engineering and mandibular dynamics into dental computer-aided design and computer-aided manufacturing (CAD-CAM) systems. This technique aims to provide more objective information to the dental technician for the diagnosis, planning, and treatment phases. In order to carry out this protocol, the following devices, currently available in many practices, are necessary: an intraoral scanner, a T-Scan system, and some specific open reverse engineering software. By means of a virtual procedure, the T-Scan system detects the occlusal contacts, and the occlusal surfaces are obtained using an intraoral scanner. Once the alignment between the 3-dimensional occlusal surface and the T-Scan registration is carried out, the resulting contacts are projected onto the patients occlusal surfaces; in this way, occlusal forces are obtained over time. The results obtained with this procedure demonstrate the feasibility of integrating different tools and software and the full integration of this procedure into a dental digital workflow.

Retrieval of unfiltered digitized cylindrical surfaces based on spin-images

In current design and manufacturing processes, the verification of tolerances is mainly focused on dimensional tolerances. As a general rule, manufacturing instructions specify dimensional tolerances and surface qualities. However, geometric tolerances are hardly ever specified, and this often leads to a lack of adequacy of the design. A better adequacy of this design would certainly produce a significant reduction in manufacturing costs. The lack of trained engineers, as well as the non-availability of the appropriate software, has relegated geometric tolerances, at the very best, to a second place. One of the greatest difficulties when using the current software solutions is the partition and identification of the meshes obtained from a scanning process on specific features. These processes can hardly be carried out via automation because they are subject to the accuracy of the tool and the skill of the technician in charge of processing the meshes. This paper presents a semi-automatic process to detect non-ideal, cylindrical features in point clouds. Its aim is to identify and extract the points from these features in order to implement them into the verification algorithms of possible associated geometric tolerances. In this process, spin-images, usually developed in the detection of shapes, are used as a graphic tool.

Semiautomatic Surface Reconstruction in Forging Dies

The reuse of damaged stamps or forgingc dies is a key aspect of the forging process. Whenever a forging die must be repaired the damaged zones are filled with welding material to be later machined. In this process, some phases can be optimized as the amount of welding material and moreover the machining tool paths and parameters. With the introduction of new digitization technologies new possibilities in the automatization of the machining are arisen. Thanks to the application of reverse engineering techniques, good and smoothed contours are extracted from the digitized geometry. The machining phase based on the obtained contours is considerably reduced in time and it does not involve any significant problem. The obtaining of these contours is the most complicated step of the proposed methodology. Some tests with diverse forging dies and mixed contours have been performed. The operations defined in this paper perform in an optimal way in all the cases. The repairs are analyzed and the required times in the actual and the proposed processes are compared.

Collision Free Design of Dental Prosthesis

This research project presents the construction of a Dental Virtual Articulator that permits the design of collision-free geometry on dental prostheses. Thanks to this articulator kinematic analysis can be taken into account in the design of dental prostheses. This is an improvement of the utmost importance in this field. Several steps have been followed in the development of this virtual articulator. First, in order to obtain a digitalized data of each individual patient, plaster models of his/her upper and lower parts of the jaw were scanned. Afterwards, depending on the required accuracy or on the patient’s setting data available in each case, the type of articulator was selected. Then, using a CAD system, the missing teeth were statically modelled. Also, the opening/closing movements and the lateral occlusion were simulated with the CAD system in order to analyze possible occlusal collisions and modify the design accordingly. Finally, this paper discusses the still existing shortcomings of virtual articulator simulation and provides a detailed research prospect as well. The main practical implications of this paper are, on the one hand, the improvement in dental CAD/CAM systems by adding the kinematic analysis, and on the other, since each of them has an individual pattern of movement, the analysis of the simulations of different articulators.

Construction of a Digital Facebow

This paper presents a research project aiming at building a digital facebow in order to locate the upper model on the dental virtual articulator. Its main goal is to improve the design process of dental prostheses, adding this virtual step to the methodology. The main practical implication of this digital facebow is this improvement of the dental CAD/CAM system by adding the relative position of the upper model without having to use a physical facebow and physical articulator. This makes virtually produced prostheses even more accurate than the ones produced with mechanical articulators.