Types Of Removable Partial Dentures Research Articles

水平荷重時においてクラスプ形態が支台歯の負担圧分散と義歯床の変位に与える影響

The purpose of this study was to investigate the effect of the modification of clasp assemblies under horizontal load. The simulated mandibular model with unilateral free end was fabricated for this study. The eleven types of removable partial dentures (RPDs) using different retainers respectively were constructed. These retainers were a cone-telescopic crown, Akers clasp, double Akers clasp, RPI clasp (Kratochvil type) and seven modified clasps made from the first three clasps to which an enlarged bracing arm, a positive rest with hook and a distal rest with a guide plate were added. Horizontal loads were applied, and the stress on abutment teeth and the displacement of denture base were measured.The results were as follows:1. Under horizontal loads, the partial denture retained by cone-telescopic crowns had the least displacement of denture base.2. The RPDs with Akers clasps, double Akers clasps and RPI clasps generated large displacement of the denture base.3. The stress characteristics on abutment teeth and displacement of denture base of the RPDs with modified clasps were similar to those of cone-telescopic crowns with enlarged lingual bracing arms, especially.

Incidence of various classes of removable partial dentures

The purpose of a classification for removable partial dentures (RPDs) is to simplify identification and enhance its teaching. A classification also allows a longitudinal comparison of various classes of RPDs to determine whether the teaching of RPD design is consistent with the relative frequencies of RPD use. This study surveyed the types of removable partial dentures being fabricated in a regional dental laboratory and compared these findings with data from previous studies. Results indicate that mandibular RPDs are more common than maxillary RPDs and the class I mandibular RPD is the most common type of RPD for either dental arch. A palatal strap was the most frequently used maxillary major connector and a lingual bar was used three times more often than a lingual plate in the mandibular arch. Cast circumferential clasps were used twice as often as RPI clasp designs. The percentage of Kennedy class I RPDs was 40%, class II 33%, class III 18%, and class IV 9%. Comparisons with a previous study indicate the percentage of Kennedy class II has increased, whereas class I, class III and class IV RPDs have not changed significantly. Findings of the study indicate that the frequency of use of the various types of RPDs has changed in the past 30 years.

Clinical evaluation of removable partial denture rest seat adaptation

The clinical relationship between the removable partial denture cast occlusal rest and the corresponding rest seat was examined. Under the conditions of the study, it was found that rests of mandibular Class I and II removable partial dentures fit significantly better than those of mandibular Class III and IV prostheses. No significant difference was noted between similar types of maxillary removable partial dentures in this regard. In evaluating the fit of specific portions of the occlusal rest, it was found that the marginal ridge zone was more closely adapted to the rest seat than other zones for all types of removable partial dentures. However, contact, as defined in this analysis, was found to exist on a random basis in all four quadrants of the occlusal rests evaluated. In spite of this fact, one fifth of the occlusal rests did not contact the opposing rest seat at any point. Improved fit with length of service was not substantiated by a cross-sectional analysis. Suggestions were made to assist the clinician in achieving a better fit between the framework and dentition in removable partial dentures.

Plaque accumulation following the wearing of different types of removable partial dentures

SummaryA group of forty‐five patients took part in a study to assess the effects of wearing partial dentures upon the accumulation of plaque in the mouth in the absence of oral hygiene. The wearing of a partial denture resulted in a significant increase in plaque accumulation and this increase was the result of a significant increase in both buccal and lingual plaque. Furthermore in a group of ten patients a small, but significant, increase in plaque occurred in the opposing arch during the wearing of the dentures. The accumulation of plaque on the buccal aspect of the teeth appeared unrelated to the type of denture worn. However, significantly more plaque accumulated on the lingual aspect of all the teeth in those patients wearing lower plate dentures as opposed to lower bar dentures. In the 3 day study periods only a small increase in plaque occurred on the palatal aspect of the upper anterior teeth not covered by any part of the partial denture and no significant increase occurred on the lingual aspect of the lower anterior teeth not covered by the partial denture. A highly significant increase occurred on the lingual aspect of lower anterior teeth covered by the lingual plate of the partial denture. Overall the wearing of a denture day and night resulted in more plaque accumulation compared with day only wearing of dentures. However considering the denture types this significant increase was not apparent in the lower plate dentures. The results provide further evidence of the potentially adverse effect partial dentures may have upon the supporting structures of the teeth when oral hygiene procedures carried out by the patient are inadequate.

Management of the marginal dentition

The patient with a marginal dentition because of dental disease or previous tooth loss may be treated with conventional fixed or removable partial dentures, modified removable partial dentures, tooth-supported overdentures, or complete dentures. For the patient with a marginal dentition—that is, a dentition of a borderline prognosis because of dental disease or previous tooth loss—a decision must be made as to which treatment method to use. Among the wide spectrum of treatment methods available are conventional fixed and removable partial dentures, modified types of removable partial dentures, tooth-supported overdentures, and complete dentures. The unique requirements of the patient must be considered carefully when a treatment plan is formulated. Whatever treatment procedures are selected, an essential portion of therapy is that performed after insertion of the restoration. Continuing professional care is a lifetime necessity.

Gingival Response to Various Types of Removable Partial Dentures

Gingival Response to Various Types of Removable Partial Dentures

A new approach to partial denture design for unilaterally remaining lower teeth

The usual types of removable partial dentures do not function adequately in mouths where one or a few lower teeth remain on only one side and where there are edentulous regions anterior and posterior to the teeth. The amount of rotation around framework fulcrums of sections of the denture base varies greatly. This uneven movement may cause excessive resorption of the ridge on the side opposite the remaining teeth. Fulcrum points or areas of the framework on a horizontal plane must be eliminated to permit a uniform vertical movement of the base. This objective can be accomplished by eliminating occlusal rests and the engaging points of stress-breaking devices. The natural tooth contours are modified by crowns to allow continuing contact of the framework and abutment teeth during function and following ridge resorption. Crowns placed on abutment teeth are contoured to have surfaces 4 to 5 mm. long that are parallel to each other in a vertical direction. These surfaces are contacted by metal bands that encircle the crowns. The contacts are 0.5 mm. in diameter, and they are made at the center of the 2.5 mm. wide metal bands. Space is established 1 mm. occlusal to and gingival to the area of contact. This space permits rotation without causing excessive torque on the abutment teeth. Contact is established after the initial rotation. The amount of space is determined by such clinical factors as the condition of ridges, crown heights, root lengths, and periodontal evaluation of the remaining teeth. The crowns may be constructed of gold or porcelain on metal. No attempt is made to attain primary retention. Occlusal displacement is counteracted by the stabilizing effect of the framework and patient training in proper tongue position. Since this type of prosthesis functions similar to a complete denture, it should be constructed only in conjunction with a complete upper denture. Acrylic resin teeth are used on the upper denture and porcelain teeth on the lower one. The teeth of the upper denture that oppose the crowns are set out of contact. Dentures of this type were constructed for 19 patients over a 2 year period. Observations on the patients were made at 6 month intervals. The observations were on patient reaction, tissue condition, stability, periodontal condition and mobility of abutment teeth, retention, maintenance of occlusion, and ridge resorption. The results were generally favorable with good patient acceptance and satisfaction. The long-term potential of the procedure requires further clinical study and observation. Information on length of time that abutment teeth can be retained, the magnitude of ridge resorption, and the relationship of ridge resorption to tooth extrusion must be secured before a final evaluation of the procedure can be made.