Introduction to Removable Partial Dentures
Some basic theoretical and practical information is needed before a technician is able to construct a satisfactory removable partial denture. A knowledge of the terminology associated with removable partial dentures is essential.
The term partial denture is used to describe many situations and several types of appliances. By definition, a partial denture is “a prosthesis that replaces one or more, but less than all, of the natural teeth and associated structures.” (CCDT) The definition makes no mention of material, design, utilization of remaining teeth for retention and stability or whether the appliance is permanently cemented or can be removed by the patient. With the introduction of “acid-etch” tooth replacements, the term “partial denture” becomes even more vague. Therefore, more descriptive terminology is in order for better communication.
A fixed partial denture is “a tooth-bone partial denture that is intended to be permanently attached to the teeth or roots that furnish support to the restoration.” (CCDT) By common usage this is synonymous with the term fixed bridge wherein the teeth to which the restoration attaches are prepared for crowns. However, the term fixed partial denture or fixed bridge may also apply to other types of permanently attached tooth replacements such as “acid-etched” tooth replacements which require much less tooth reduction.
A removable partial denture is “a partial denture that can be readily placed in the mouth and removed by the wearer.” (CCDT) Here, also, there is no mention of material, design or how the appliance is retained. A person who indicates they have a “partial denture” they can remove may mean a simple all-resin appliance with no clasps, a similar appliance with simple wire clasps, a combination resin-cast metal appliance (described in the following sections), or a complicated appliance constructed in conjunction with fixed restorations known as a precision attachment removable partial denture. In this manual, the term removable partial denture will apply to appliances with cast metal retentive mechanisms and resin bases.
The term “bridge” is often used by patients. It may mean a “fixed” replacement, a removable partial denture or even a complete denture; (some people just do not like the term “denture”!). Avoid using the term “bridge” unless you modify the word to make it more descriptive.
OBJECTIVES OF REMOVABLE PARTIAL DENTURE TREATMENT
The objectives of removable partial denture treatment are:
1. To preserve and maintain the remaining oral structures.
2. To restore function.
3. To improve or restore appearance (esthetics).
The following terms are used in the following sections and apply to removable partial denture techniques:
Base: That portion of a removable partial denture that contacts the oral mucosa and serves as an attachment and support for the replaced teeth. Usually, the base provides support for the removable partial denture by being in close apposition to the oral mucosa covering the supporting bone (maxillae or mandible).
Direct Retainer: “A clasp, attachment, or assembly applied to an abutment tooth for the purpose of maintaining a removable restoration in its planned position in relation to oral structures.” (CCDT) The direct retainers with which we are concerned in this manual are clasps. A clasp usually consists of two arms joined by a body which may connect with an occlusal rest. A clasp is an extracoronal retainer, one that fits over the external surface of the tooth.
Major Connector: “A metal plate or bar (e.g., lingual bar, linguoplate, or palatal bar) used to join the units of one side of a removable partial denture to those located on the opposite side of the dental arch.” (CCDT)
Minor Connector: “The connecting link between the major connector or base of a removable partial denture and other units of the restoration, e.g., direct and indirect retainers or rests.” (CCDT)
Finish Line: The junction between metal and plastic portions of a removable partial denture. An internal finish line is on the internal or tissue surface and is formed while preparing a cast for duplication. An external finish line is on the polished surface of a denture and is formed in the wax pattern.
Plastic Retention: That portion of a partial denture framework which attaches the resin base to the framework.
CLASSIFICATION OF REMOVABLE PARTIAL DENTURES