Although computer-aided design and manufacture techniques have shown some promising applications in the fabrication of crowns, inlays, and maxillofacial and oral surgery, the field of removable prosthodontics has not embraced these technologies so far. This study developed and investigated computer-aided techniques that may eventually enable prosthodontic procedures such as surveying and the production of sacrificial patterns to be performed digitally.A 3-dimensional computer model of a conventional cast from a patient was obtained using an optical surface capture device (a scanner). The shape of a number of components of a removable partial denture framework was modelled on the 3-dimensional scan electronically using computer aided design software. A physical plastic shape of the components was produced using a Rapid Prototyping machine and used as a sacrificial pattern. Techniques to allow digital cast surveying before the production of sacrificial patterns were also developed. The results show that digital dental surveying and machine-produced sacrificial patterns can be accomplished. The study forms a basis for further developments leading to a fully integrated approach to the computer-aided design and fabrication of removable partial denture frameworks.

A technique is described and demonstrated for generating high-resolution 3-D images of the objects on the seabed, combining synthetic aperture sonar with bathymetric (interferometric) processing. This has applications in surveying of oil wells, pipelines and shipwrecks, and in defence in mine hunting. It is shown that the technique is very sensitive to platform motion errors, and ways are discussed by which the errors may be estimated and compensated. Practical results obtained with an experimental system in a test tank are presented and discussed, and a number of areas for further work are identified. 1 Introduction Sidescan sonars are now a widely accepted and important tool of ocean technology. Broadly, they fall into one of two classes: the short-range high-resolution systems working at a relatively high frequency (e.g. about 100kHz), and the long-range low-resolution systems working at 10kHz or less. The former have a wide range of applications in surveying of oil wells, pipelines and shipwrecks, and in defence in mine-hunting. The longer range systems such as GLORIA have contributed significantly to the study of the deep ocean floor. The original method of determining seabed topography is by means of an ship-mounted echo sounder, covering a given area in a raster fashion. This is slow

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It is well established that the Removable Partial Denture (RPD) is an effective treatment prosthesis. The objectives of a successful RPD are: to preserve the health of remaining oral structure, restore function and restore esthetics. To achieve these objectives, an RPD framework must fit accurately to the supporting structures. This paper presents a method for measuring the gaps or spaces present between the RPD framework and supporting structures which will enable the dentist and the dental technician to evaluate the accuracy of fitting of the prosthesis before it is delivered to the patient. The method used in this research is based on the principle of electric capacitance and uses a specially designed prototype measurement system.

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