Surveying removable partial dentures: the importance of guiding planes and path of insertion for stability O. L. Bezzon, DDS, PhD, a M. G. C. Mattos, DDS, a and R. F. Ribero, DDS b Department of Dental Materials and Prosthodontics, School of Dentistry of Ribeir~o Preto, University of S~o Paulo, Silo Paulo, Brazil Statement of problem. Although removable partial dentures are a favored option for the restoration of many situations that involve partial tooth loss, some patients are not satisfied with a removable partial denture, especially when it is not stable during mastication. A dental surveyor can be used to prevent countless problems related to the production of removable partial dentures. Many professionals working with oral rehabilitation fail to take advantage of the many uses of a surveyor in planning and designing chromium alloy and other metal removable partial denture frameworks. Purpose. This article uses an academic approach to describe the criteria used to determine the path and removal of a removable partial denture. A fundamental requirement for understanding the correct use of the dental surveyor is to prevent indiscriminate use of a path of insertion perpendicular to the occlusal plane, and extreme inclinations of the cast in the attempt to create undercuts on some teeth. (J Prosthet Dent 1997;78:412-18.) When performing oral rehabilitation with rc- movable partial dentures (RPDs), the objective of the dentist should be to make a prosthesis that the patient can easily seat and remove from the mouth and yet, when seated, the prosthesis will resist the dislodgment poten- tial caused by masticatory function, especially mastica- tion of sticky foods. The problem involves an interac- tion of engineering and biologic elements, so a biome- chanical approach should be used for its solution. On this basis, it is imperative that diagnostic casts for all RPDs be analyzed with a dental parallelometer (sur- veyor), the instrument that permits accurate planning of each structural detail of the prosthesis.1 A diagnostic cast should be surveyed for three major reasons: (1) determination of the path of insertion to obtain efficient and esthetically pleasing retentive clasps; (2) tracing the survey line to enable positioning of the rigid parts of the prosthesis, so they will seat without interference; this procedure provides information about the need to recontour the abutments and other teeth and to improve the functioning of rigid parts and the esthetic aspects related to it; and (3) analysis of the con- ~Associate Professor. bAssistant Professor. tour of soft tissues to prevent the occurrence of lesions that result from seating the prosthesis. 2 The use of a dental surveyor permits the dentist to plan, study, and design an RPD that will provide adequate retention, sup- port, stability, and esthetic appearance. 3,4 In 1954, Applegatc s commented that the intelligent use of the dental surveyor is the best way to prevent the occurrence of countless problems frequently related to oral rehabilitation with RPDs. However, daily contact with professionals in our vicinity shows that there are many dentists who have no dental surveyor and are un- aware of the importance of its use when they are mak- ing RPDs, because they believe the technician may be more experienced and they choose to delegate the re- sponsibility to the technician. 6 The objective of this study was to use an academic approach to remind dental practitioners of the under- standing of the dynamics involved in determining the path of insertion, a fundamental condition for the in- clusion of the dental surveyor as a tool of routine use in planning and designing RPDs. PATH OF INSERTION AND REMOVAL The RPD path of insertion and withdrawal is the di- rection in which the prosthesis moves in relation to the 412 THE JOURNAL OF PROSTHETIC DENTISTRY VOLUME 78 NUMBER 4