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Purpose: The purpose of this study was to critically analyze important hygienic/secondary prophylactic and biomechanical aspects of removable partial denture (RPD) design., Materials and Methods: The literature related to traditional biomechanical design and open/hygienic design of RPDs was discussed by the authors at a 2.5-day workshop. The written report was circulated among the authors until a consensus was reached., Results: There is little scientific support for most of the traditional design principles of RPDs, nor has patient satisfaction shown any correlation with design factors. However, there is evidence that an open/hygienic design is more important than biomechanical aspects for long-term oral health. The biomechanical importance of some components is questioned, e.g., indirect retention and guiding planes. Alternative connector designs that reduce risks of tissue injury are described. Direct retainers and pontics are discussed in relation to the possibilities they offer for gingival relief., Conclusion: Greater attention should be paid to RPD design principles that minimize the risks of tissue injury and plaque accumulation in accordance with modern concepts of preventive dentistry.

This final article in the series describes the modification of teeth to improve their shape for the support and retention of RPDs.

This article describes measures designed to provide short-term solutions to existing RPD problems and to establish an optimum oral environment for the provision of definitive prostheses.

This article describes the types and functions of connectors for RPDS. It also considers the relative merits and limitations of these connectors.

This article describes the mechanisms for retaining RPDs and considers the different types of direct retainer. The factors influencing the effectiveness of retentive clasps and governing the choice of clasp are discussed.

This article describes a method of building RPD components into an effective design and indicates how the details of the design can be communicated clearly to the dental technician.

Factors contributing to good RPD design are described, including the respective inputs of the dentist and dental technician. Poor communication in current practice is reported and an appropriate format for a work authorization presented.

This article describes the benefits and risks of providing RPDs. It emphasises the importance of co-operation between the dental team and patient to ensure that the balance of this 'equation' is in the patient's favour.

This article considers first, factors influencing the need and demand for removable partial dentures (RPDs) and second, the particular requirements and problems of elderly patients related to such treatment.

Knowledge-based systems (KBS), otherwise and formerly known as 'expert systems', are computer programs that contain a representation of knowledge that can be used to solve problems normally requiring human intelligence. This article discusses the contributions such systems can make to medicine and dentistry, indicates the range of existing dental KBSs and gives reasons why removable partial denture (RPD) design has attracted so much attention in this respect. A description is also given of the 'RaPiD' system for designing RPDs at the chairside.

Details are presented of the reaction of multiple prosthetic experts in 17 dental schools in the U.K. to 125 design rules for removable partial dentures. Those rules receiving support from 50% of the schools are candidates for inclusion in RaPiD, a knowledge-based assistant for the design of removable partial dentures.

The authors report on the eliciting of the partial denture design expertise of teachers of prosthetic dentistry. Their approach was to identify 125 design rules and then to sample expert reaction by surveying 10 experts individually and by surveying the prosthetic departments in all 17 dental schools in the British Isles. The surveys achieved a return of 100% and revealed an unsuspected consensus concerning the rules. A majority of schools were in agreement on whether or not 111 (89%) of the rules could be supported. This design expertise will be disseminated through RaPiD, a knowledge-based assistant for the design of removable partial dentures. It is expected that by incorporating into this design assistant rules which have been shown to be widely supported, the acceptability and usefulness of RaPiD for clinical education and practice will be increased.

This evaluation was based on replies from a random sample of general dental practitioners who were asked to complete questionnaires before and after being sent a video and accompanying booklet on partial denture design. Forty per cent (257) of the original sample (636) completed and returned both questionnaires. A total of 212 respondents (82%) felt the video had been of value and 175 (68%) said they would be more likely to provide metal partial dentures after having watched it. The positive effects of the video were greatest amongst the most recently qualified. Despite some improvement after watching the video, there remained 105 (40%) who indicated that they would leave all partial denture design decisions to the technician on at least some occasions. Comparison of data from first and second questionnaires showed little evidence of substantial shifts in choice of denture design for a series of specific situations. It was concluded that whilst the programme had been well received and had produced changes in intention, there was less objective evidence of change.

Dentists frequently fail to provide dental technicians with the design information necessary for the construction of removable partial dentures. The computerization of dental practices and the development of appropriate knowledge-based systems could provide a powerful tool for improving this aspect of dental care. This article describes one such system currently under development which is an example of the kind of additional facility that will become available for those practices with the necessary hardware.

A knowledge-based system for designing removable partial dentures is described in which graphical representations of denture components are manipulated directly by the user to build the required denture design. The arch form of individual patients may be depicted by linear movement and rotation of the icons representing teeth. The size, shape and position of many denture components are determined dynamically to conform to the shape of abutment teeth and to the juxtaposition of other elements. Expert clinical knowledge is used to analyse the developing design and suggest alternate approaches.

An account is given of Sigmund Freud's illness and care following the diagnosis of oral cancer in 1923. The key figure in the clinical management was Professor Hans Pichler of Vienna, who undertook the maxillectomy and most of the subsequent prosthetic care. Other contributors included Doctors Schroeder and Weinmann and Professor Kazanjian. Two of Freud's obturators are in the collection of the Freud Museum, London. An examination of these, together with reference to a copy of Pichler's clinical notes, also in the Museum's collection, has allowed the position of these prostheses, within the overall scheme of Freud's care, to be identified.

An in vitro test for screening the abrasion resistance and abrasivity of composite resins when used to provide tooth undercuts for removable partial denture clasps is described. In the present study nine composite resins were tested against wrought stainless steel round clasps. The results indicated that the abrasion of any of the composites tested was unlikely to cause a noticeable loss of retention in the clinical situation. However, there was marked abrasion of the clasps by two of the composites which would be likely to be clinically relevant.

A bubble gauge was compared with the tripod method and the use of multiple lines for recording the path of placement of a removable partial denture on a cast. The bubble gauge proved to be more accurate and quicker than the other methods, and it was preferred by both technicians and clinicians.