Richard P. Frank

A study of the flexibility of wrought wire clasps

T he 18-gauge platinum-gold-palladium (PGP) wrought wire clasp arm is often used as a direct retainer for distal-extension removable partial dentures instead of a cast chromium-cobalt clasp arm, when the retentive undercut is on the mesial-buccal part of the abutment tooth. The wrought wire clasp arm can flex in any direction so that stresses caused by movement of the removable partial denture are dissipated. This helps to protect the abutment tooth from harmful forces. The 18-gauge PGP clasp wire has a fusing temperature sufficiently high that it can be safely cast against by gold and some chromium-cobalt alloys and soldered without changing its physical properties. An 18-gauge clasp wire is thick enough to resist breakage and allow tapering for additional flexibility.’ However, clinical observations of some wrought wire clasps on removable partial dentures constructed at the School of Dentistry, University of Washington, have indicated that these clasps may be less flexible than expected. Several reports in the dental literature have documented similar findings.

TREATMENT OUTCOMES WITH MANDIBULAR REMOVABLE PARTIAL DENTURES : A POPULATION-BASED STUDY OF PATIENT SATISFACTION

STATEMENT OF PROBLEM Little is known about the outcomes of treatment with mandibular removable partial dentures provided by dentists in private dental practice. PURPOSE This study examined 15 aspects of patient satisfaction and explored the factors found to be associated with dissatisfaction. MATERIAL AND METHODS A questionnaire was mailed to people whose dental insurance claims included CPT Code 5214 within the last 5 years. A composite measure of treatment outcome was created by combining the responses to the 15 satisfaction items, and 10 factors were then tested statistically to determine their relationship to dissatisfaction. RESULTS A majority of the respondents were satisfied with the prosthesis, but a substantial amount of dissatisfaction existed. Dissatisfaction was greater when there was no previous wearing experience or when there was an opposing maxillary removable partial denture. Respondents under the age of 60 expressed more dissatisfaction than did those over the age of 60, and subjects with lower levels of general health also reported less satisfaction. One third of the respondents believed their prosthesis required adjustment or replacement, and one fourth said the removable partial denture had caused a problem with the natural teeth. CONCLUSION A majority of survey respondents treated with a mandibular removable partial denture in private dental practice were satisfied with the prosthesis, but a substantial amount of dissatisfaction existed. Dissatisfaction was related to age, health, prior experience with a prosthesis, and the type of opposing dentition.

Relationship between the standards of removable partial denture construction, clinical acceptability, and patient satisfaction

STATEMENT OF PROBLEM Little is known about the importance of published fabrication standards in determining the outcome of treatment with mandibular distal extension removable partial dentures in patients of community practices. PURPOSE This study describes mandibular partial dentures worn by patients from King County, Wash., and examines the validity of standards of design and fabrication by relating the standards to measures of clinical acceptability and patient satisfaction. MATERIAL AND METHODS Eighty-two people treated in private dental practices who responded to a mail survey about satisfaction with a partial denture were examined. Eight standards of fabrication, overall clinical acceptability of the prosthesis, and tissue health were evaluated clinically. Patient satisfaction was assessed by questionnaire. Associations between variables were assessed by contingency tables and odds ratios. RESULTS Half the prostheses met 4 or fewer of the 8 standards, and these were responsible for nearly all the displacement of tissue by the framework. Forty-three percent of the dentures (35/82) were rated clinically acceptable. Of the remaining dentures, 38 could be made acceptable by modifications. The remaining 9 dentures needed replacement. Sixty-three percent of the patients examined were satisfied with the dentures. There was a relationship between tissue health and the fabrication standards related to rest form, base extension, stress distribution, and framework fit. This study found no relation between tissue health and other design or fabrication features. None of the standards were found to be related to patient satisfaction. CONCLUSION This study found partial support for the validity of design/fabrication standards for removable partial dentures. The most important standards are rest form, base extension, and stress distribution. The standards appear to be unrelated to patient satisfaction.

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.

A comparison of the flexibility of wrought wire and cast circumferential clasps

M any dentists use wrought wire clasps instead of cast circumferential clasps on abutment teeth for distalextension removable partial dentures. The flexibility of the wrought wire clasp is believed to reduce transmission of excessive force to the abutment tooth.’ Recent investigations have compared the flexibility of various wrought wires and nickel-chrome-cobalt alloys commonly used for clasp construction. Morris et al.’ developed a stiffness index by testing clasps with a stress-relaxation cycling instrument. The index allows the stiffness of clasps to be compared regardless of dimension, form, or material. Brudvik and Morris3 tested six wrought wires including two different alloys and several gauges. Stress-relaxation cycling was used to determine the stiffness of the specimens. In a later study, Morris et aL4 found that the stiffness of cast circumferential clasps was greatly influenced by the width/thickness ratio of the clasp. A study by Frank and Nicholls5 ranked 16 precious and nonprecious wrought wires according to their flexibility. Each clasp sample was displaced one time until the proportional limit was exceeded. Twentygauge wires were found to be twice as flexible as l&gauge wires. Flexibility values also diKered due to the various alloys used in manufacturing the wires. Several wrought wires were tested independently by both the stress-relaxation cycling and the singledisplacement methods. Although the values for stiffness and flexibility cannot be compared directly, each method resulted in the same ranking of the clasp samples. The purpose of this study was to compare the flexibility of several forms of cast nickel-chrome and cobalt-chrome clasps with that of wrought wire clasps. Round and half-round forms were selected. The single-

An investigation of the effectiveness of indirect retainers

A mandibular bilateral distal-extension base removable partial denture was lifted from a model under standardized conditions. The amount of denture base displacement under various loads and the forces of removal were measured electronically. The framework was constructed to allow repeated changes in the type of clasp, location of indirect retainer, and position of the rest seat on the terminal abutment tooth. The usefulness of an indirect retainer in preventing occlusal displacement of the denture base appears to be limited. The type of clasp had the greatest influence on the amount of denture base movement. Proximal surface guiding planes were also found to be important in preventing lifting of the denture base. Use of mesial instead of distal rests on the terminal abutment teeth did not decrease indirect retention.

Evaluating refractory cast wax-ups for removable partial dentures

A review of the waxed refractory cast and blocked-out master cast by the dentist is an effective method for controlling the quality of framework castings. Major errors in wax-ups have been shown to occur frequently, but they are corrected easily if detected prior to casting. This critique can be incorporated readily into the private practice of dentistry.

Direct retainers for distal-extension removable partial dentures

Clinical observations at the University of Washington indicated that the wrought wire clasp assembly, the I-bar clasp assembly, and the L-bar clasp assembly yield similar results. A periodic recall system for patients with removable partial dentures has been in effect since 1976. Several thousand observations have been made by the faculty, and no special trend of problems has been noted that would cause one clasp assembly to be favored over another. These three types of clasp assemblies work satisfactorily when properly chosen and carefully applied.

Fabrication of temporary and treatment partial dentures

Abstract The method of pouring cold-curing acrylic resin into an alginate mold for making temporary and treatment partial dentures requires no special equipment or materials and has been found to be fast, accurate, practical, and economical. Denture adjustments to permit insertion are seldom necessary.

Accurate master casts obtained rapidly.

Abstract Because of the time involved, the procedure of ☐ing an impression often is eliminated by dentists or dental laboratory technicians. The procedure described in this article has the advantage of conserving on time and expensive materials. The technique can be easily taught and delegated to auxiliary personnel. It insures that the desired qualities of a master cast are obtained from the impression.