CLASSIFICATION OF RPDs AND PARTIALLY EDENTULOUS ARCHES

Transcription

1 د.حكمت جميل Lec: 2 Prosthodontic CLASSIFICATION OF RPDs AND PARTIALLY EDENTULOUS ARCHES The classification of RPDs and partially edentulous arches simplifies communication and discussions. Requirements of an Acceptable Method of Classification The classification of a partially edentulous arch should satisfy the following requirements: 1. It should permit immediate visualization of the type of partially edentulous arch that is being considered. 2. It should permit immediate differentiation between the tooth-supported and the tooth- and tissue-supported removable partial denture. 3. It should be universally acceptable. Many systems of classification have been suggested. 1. CLASSIFICATION BASED ON SUPPORT There are three types of RPDs or partially edentulous arches based on the tissue(s) which provide support. Support is the resistance to movement of the denture toward the edentulous ridge. RPDs may be tooth supported; tissue supported, and tooth tissue supported. This is a simple classification system and very meaningful because the principles of RPD design depends, to a great extent, on its supporting tissue(s). A. The Tooth Supported RPD Tooth supported RPDs receive all their support from the abutment teeth. Retention is derived from direct retainers on the abutment teeth, Tooth supported RPDs do not move appreciably in function. B. The Tooth-Tissue Supported RPD The tooth-tissue supported RPD is supported at one end by natural teeth, which essentially do not move, and at the other end by the denture bearing tissues (mucosa overlying bone) which moves because of the resiliency of the mucosa

2 The design of the tooth-tissue supported RPD is one of the most controversial topics in prosthodontic. Several philosophies with specific RPD designs or construction techniques have been suggested to compensate for the difference in support provided by the natural teeth and denture foundation tissues. C. The Tissue Supported RPD Tissue supported RPDs are primarily supported by the tissues (mucosa overlying bone) of the denture foundation area. Tissue supported RPDs usually have plastic major connectors and are, therefore, usually interim RPDs. Tissue supported RPDs will move in function because of the resiliency of the mucosa. Retention for tissue supported RPDs is customarily provided by wrought wire retentive clasp arms on selected natural teeth. Tissue supported RPDs have the potential to cause soft tissue damage and periodontal attachment loss and accordingly should be used for only a short period of time. 2. CLASSIFICATION BASED ON type of treatment A. The Definitive RPD Definitive RPDs are constructed after extensive diagnosis, treatment planning, and thorough preparation of the teeth and tissues for the prosthesis. The length of service of definitive RPDs is intended to be many years this meaning the cobalt chromium alloy removable partial dentures. B. The Interim RPD Interim RPDs are usually constructed as part of the preparation of the mouth for definitive RPD, FPD or implant treatment. The length of service of interim RPDs is generally planned to be a year or less, they are frequently referred to as TEMPORARY RPDs example of that type is the acrylic removable partial dentures.

3 3. CLASSIFICATION BASED ON ARCH CONFIGURATION The most widely accepted system of classification of RPDs and partially edentulous arches was proposed by Dr. Edward Kennedy in It is based on the configuration of the remaining natural teeth and edentulous spaces. This system was further defined and expanded upon by Dr. O.C. Applegate and Dr. Jacques Fiset. The value of the Kennedy- Applegate-Fiset classification system is that it is relatively simple, easy to remember, extremely comprehensive and very practical. It permits visualization of the partially edentulous arch or RPD designed for that arch. It indicates the type of support for the RPD, which suggest certain physiologic and mechanical principles of treatment and RPD design. There is a correlation between the basic classes and the incidence of the partially edentulous arch configurations. Today, the Kennedy method is probably the most widely accepted classification of partially edentulous arches. In an attempt to simplify the problem and encourage more universal use of a classification, and in the interest of adequate communication, Although classifications are actually descriptive of the partially edentulous arches, the removable partial denture that restores a particular class of arch is described as a denture of that class. For example, we speak of a Class III or Class I removable partial denture. It is simpler to say a Class II partial denture than it is to say a partial denture restoring a Class II partially edentulous arch. THE KENNEDY-APPLEGATE-FISET CLASSIFICATION SYSTEM The Basic Classes Class I - bilateral edentulous areas located posterior to all remaining teeth.

4 Class II - unilateral edentulous area located posterior to all remaining teeth. Class III - unilateral edentulous area bounded by anterior and posterior natural teeth. Class IV - a single, but bilateral (crossing the midline) edentulous area located anterior to remaining teeth. Applegate's Rules for Applying the Kennedy Classification Rule 1: Classification should follow rather than precede extraction. Rule 2: If the 3rd molar is missing and not to be replaced, it is not considered in the classification. Rule 3: If the 3rd molar is present and to be used as an abutment, it is considered in the classification.

5 Rule 4: If the second molar is missing and not be replaced, it is not considered in the classification. Rule 5: The most posterior edentulous area determines the classification. Rule 6: Edentulous areas other than those determining classification are called modification spaces. Rule 7: The extent of the modification is not considered, only the number. Rule 8: There is no modification space in Class IV. The modification area: any additional edentulous area being located in partially edentulous arch other than that main edentulous space that determine the main case classification, these spaces is enumerated and it will determine the final case classification. Class II, modification 1 Class II, modification 2

6 Class III, modification 2 Kennedy placed the Class II unilateral distal extension type between the Class I bilateral distal extension type and the Class III tooth-supported classification because the Class II partial denture must embody features of both, especially when tooth-supported modifications are present. Because it has a tissue-supported extension base, the denture must be designed similarly to a Class I partial denture. Often, however, a tooth-supported, or Class III, component is present elsewhere in the arch. Thus the Class II partial denture rightly falls between the Class I and the Class III, because it embodies design features common to both. In keeping with the principle that design is based on classification, the application of such principles of design is simplified by retaining the original classification of Kennedy. Examples of different partially edentulous cases: CL IV CL II Mod2 CL I Mod1

7 CL IIIMod3 CL IMod2 CL III Mod1 CL IV CL II CL III Mod5