Removable Partial Denture Construction Research Articles

Communication between dentists and dental technicians in Lisbon for the construction of removable partial dentures’ metal frameworks

Objectives: To evaluate the communication between dentists and dental technicians in Lisbon for the construction of metal frameworks for removable partial dentures (RPDs). Methods: This observational study’s target population was laboratories in Lisbon. Data were collected through a questionnaire including six categories: medical prescription, conventional definitive impression and its disinfection, digital impression, analysis of study and working casts, and design and construction of the metallic structure. Dental technicians completed the questionnaire after consulting the medical instructions and observing the stone casts. The variables were subjected to descriptive statistics. Results: Three laboratories agreed to participate in this study, and the final sample included 53 entirely completed questionnaires. All definitive casts were obtained by conventional impression, with a universal tray (67.9%) and alginate (84.9%). The laboratories disinfected all impressions, mostly with sodium hypochlorite (98.1%), and the dental technician analyzed 84.9% of the casts in the parallelometer. There were no pre-prosthetic preparations in 66% of the working casts. The dentists provided design instructions in five cases, and only one delivered a drawing on paper. All metal frameworks were made in cobalt-chromium, mainly by electronic induction casting (96.6%). Conclusions: The dentist did not provide the dental technician with most of the design and planning instructions required for constructing removable partial dentures. This finding confirms the lack of communication between clinics and laboratories in Lisbon.

LASERS IN PROSTHODONTICS

Laser treatment in periodontal and oral surgery and in other disciplines in dentistry has replaced many traditional electrosurgical and scalpel procedures and is beginning to replace the dental handpiece. The successful construction of removable full and partial dentures mainly depends on the preoperative evaluation of the supporting hard and soft tissue structures and their proper preparation. Lasers may now be used to perform most preprosthetic surgeries. These procedures include hard and soft tissue tuberosity reduction, torus removal, treatment of unsuitable residual ridges including undercut and irregularly resorbed ridges, treatment of unsupported soft tissues, and other hard and soft tissue abnormalities. Stability, retention, function, and esthetics of removable prostheses may be enhanced by proper laser manipulation of the soft tissues and underlying osseous structure.

Comparison in Bone Density Changes for Two Different Designs in Treatment of Mandibular Bilateral Free End Saddle with Osseointegrated Implants

AIM: The aim of this study is to evaluate two different designs in mandibular bilateral free end saddle cases with the use of osseointegrated implants. The designs evaluated were OT-strategy extracoronal attachment and bar attachment. Radiographic evaluation was carried out for implants and natural abutment in terms of bone density.
 MATERIALS AND METHODS: This study was conducted on 10 patients with bilateral distal extension area with missing molars bilaterally; the patients were divided into two groups after implant insertion on the second molar area. Group I: Patients received extracoronal attachment distal to the last natural abutment teeth with the construction of metallic removable partial denture (RPD). Group II: Patients received bar attachment with the construction of metallic RPD. Both groups have the maxillary arch edentulous with the construction of complete maxillary dentures within our study. Radiographic evaluation for bone density was done for both groups at the time of prosthesis insertion, 3, 6, and 9 months later. A comparison between the two groups regarding each follow-up period was performed by an independent t-test.
 RESULTS: Although there were some differences between both designs in the 1st-time intervals, generally, there were no significant differences between the two designs all over the 3-time intervals.
 CONCLUSION: From the results of this study, it was concluded that: Although there were no significant differences between both designs, bar-attachment showed better results which should be confirmed with more future researches.

Quality of communicating design features for cobalt chromium removable partial dentures in Riyadh, Saudi Arabia

This survey aimed to investigate quality of communicating design features for the construction of cobalt chromium removable partial dentures (RPDs) among dentists in Riyadh, Saudi Arabia. A survey of nine commercial dental laboratories located in Riyadh was carried out. In each visit, master casts for cobalt chromium RPDs and dentists' prescriptions were examined. A quality score for the provided instructions was developed and ranged from 0 to 4. A zero score means that no instructions were sent from the dentist for the design of the RPD. A score of 4 means that instructions were provided for the design of four main elements of the RPD, i.e., shape of major connector, type of direct retainers, position of direct retainers, position of dental rests. 162 dentists' prescriptions for RPDs and related casts were assessed. The majority of RPD cases were designed by the dental technician alone (64.2%). Shape of the major connector was the most frequent element in dentists' prescriptions (35.8%). The mean quality score of dentists' instructions was 0.96 (sd=1.54). 18% of the provided instructions achieved quality score equal to 4. Prescriptions for Kennedy Class III cases achieved significantly higher mean quality score compared to Kennedy Class II cases (p<0.05). 16.7% of the evaluated casts had clearly defined rest seat preparation. The results of this survey indicate inadequate quality of communicating the design features of cobalt chromium RPDs among practicing dentists in Riyadh, Saudi Arabia. The reliance on the dental technician to design the cast RPDs seems to be high.

The influence of undercut depths on the accuracy of casts poured from irreversible hydrocolloid impression materials

ObjectivesTo evaluate the elastic recovery of a typical irreversible hydrocolloid impression material in terms of the amount of undercut identified and additional thickness of spacer provided before custom tray fabrication. MethodsThis study surveyed the undercut depths of the teeth surfaces and lingual sulci of one hundred partially dentate mandibular dental casts which were subsequently scanned and the data exported as STL files. A typical cast from each undercut category (0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 4mm, 5mm) was 3D printed. Three custom trays were constructed with spacer thicknesses representing 20%, 30% and 50% compression against the wall of the custom trays on removal, impressions recorded, and casts fabricated in dental stone. Measurements for elastic recovery of irreversible hydrocolloid were done using an internal caliper and a digital caliper. All measurements were done by the principal investigator. Non-parametric analyses were used for comparisons of the undercut values between the 3D printed and poured casts to determine the amount of elastic recovery of the irreversible hydrocolloid impression material. ResultsThere was no statistically significant difference in measurements between the original 3D printed casts and the poured casts, irrespective of percentage compression (p > 0.05). ConclusionsIn removable partial denture construction, casts should be blocked out parallel to the path of insertion and then an additional 3mm of spacer applied as a standard technique before custom tray fabrication to ensure elastic recovery of the irreversible hydrocolloid impression. Clinical implicationsIn severe undercut situations, accurate impressions can be taken using irreversible hydrocolloid by blocking out all undercut surfaces on the teeth and lingual sulci before adapting additional three-millimetre wax spacer on casts when constructing custom trays thereby ensuring accurate and reliable impressions for removable prosthesis construction.

Communication Between Dentists and Dental Technicians During the Fabrication of Removable Partial Dentures in Khartoum State, Sudan.

ObjectivesTo investigate the quality of communication between dentists and dental laboratory technicians in private dental laboratories in Khartoum State related to fabrication of removable partial dentures.MethodsThis was a descriptive cross-sectional study, in which dental technicians were interviewed regarding the quality of instructions they received from dentists concerning the construction of removable partial dentures (RPD). Eighty cases were investigated, 69 acrylic (A-RPD) and 11 cobalt chromium (CC-RPD) dentures.ResultsAlthough dentists provided no instructions in 21.7% of A-RPD cases, they gave instructions in all CC-RPD cases. Instructions were primarily given verbally (55.1% in A-RPD, 54.5% in CC-RPD cases), as opposed to written (23.3% in A-RPD, 45.5% in CC-RPD cases). Most design components for A-RPD and CC-RPD cases were not clearly prescribed, and instructions were clear in only 8.7% of A-RPD and 36.4% of CC-RPD cases. Notably, surveying of casts by dentists was only done in 18.2% of CC-RPD cases. Most technicians (84.2%) believed that prosthesis design was the dentists' responsibility. Technicians needed to contact dentists for clarification of design significantly more frequently for CC-RPD (p=0.004) cases.ConclusionQuality of communication between dentists and private laboratory technicians in Khartoum State with regard to removable partial denture construction was largely inadequate.

Impression techniques for removable partial dentures: A review

The use of the removable partial denture to restore the posterior edentulous space continues to be a viable treatment option for patients who are not candidates for cantilever fixed prosthesis or dental implants because of the nature of the remaining teeth and bony support, the anatomy of the residual ridges, or financial constraints. The construction of removable partial denture is a delicate procedure since the prosthesis is supported by two different tissues namely teeth and mucosa. The different resiliency of these supporting tissues may lead to instability of the prosthesis. This article reviews various impression techniques that aim to equalize the masticatory load between teeth and edentulous areas thus enhancing the stability of partial denture during function and preserving the residual oral structures. Keywords: Removable partial denture, Dual impression technique, Functional impression, Distal extension

Preventive and conservative prosthodontic treatment using overdenture and Richmond crown

Prosthodontic treatment aims to restore the chewing function (rehabilitation) and to prevent tooth decay and bone resorption (preventive and conservative). As an example, treatment by overdenture and Richmond crown. Overdenture is a partial or complete removable denture covered and supported by one or more teeth, the tooth roots and/or dental implants. Richmond crown is fixed denture by post and crown system, in which the post part goes into the root canal and its crown covers the entire of original tooth crown surface. By retaining the original teeth and/or roots, it could improve the stability and retention of the denture, and defend proprioseptic of teeth and vertical dimensions. To provide information about preventive prosthodontic treatment and prevention by using overdenture and Richmond crown. Case Report: A 50 year old woman only has 44 teeth on the mandible which is indicated for the overdenture construction and loss teeth 13, 14, 17 and 27 on the maxilla with deep caries in teeth 22 which is indicated for a removable partial denture (RPDs) construction by Richmond crown gear 22. On an early stage study, printing models is done. Then treatment of the root canal on teeth 22 and 44, followed by root canal preparation, core construction (cast post) and Richmond crown on tooth 22 and bareroot preparation on tooth 44 for overdenture construction. The procedure followed by printing, recording bite to insertion. Choosing treatment either overdenture or Richmond crown is very important because it could mantain remain original teeth, thus it can help to improve the retention and stabilization.

FLEXIBILITY OF THE RETENTIVE ARM OF ACETAL RESIN CLASP VERSUS CAST CLASPS- AN IN VITRO STUDY

Restoration of esthetics is an important factor to consider in the fabrication of a removable partial denture (RPD) . 1 Several types of polymers and metal alloys have been used in RPD construction. Frequently, RPD clasps made from the same alloy as the metal framework. The most common alloys used for clasps are cobalt-chromium (Co-Cr) alloy and gold and titanium alloys, although these may be unesthetic. 2 Some strategies can be used to optimize aesthetic results in RPDs, such as attachment systems 3 RPD with a rotational path of insertion, 4 aesthetic clasp designs 5

Ethics in the provision of removable partial dentures

Aim: To investigate the construction of cobalt-chromium removable partial dentures by commercial private dental laboratories. Methods: Ninety master casts for fabrication of cobalt-chromium removable partial dentures were obtained from three commercial laboratories randomly selected. Casts were assessed for dental arch treated, Kennedy classification, cast surveying, denture design information provided by the dentist, and mouth preparation (rest seat, guiding plane and retentive area). Dental technicians answered a questionnaire regarding qualification of assisted dentists, monthly number of framework castings, and use of dental surveyor. Mouth preparation was compared among laboratories using Kruskal-Wallis test (α=0.05). Results: The percentage of Kennedy class I was 16%, class II 19%, class III 56%, and class IV 9%. The majority of master cats (51%) examined was sent to dental laboratories without any design information and did not comply with ethical guidelines in the provision of RPD. Approximately half of the casts were considered “inappropriate” for guiding planes and retentive areas. One of the laboratories presented all casts “inappropriate” for rest seat distribution (p<0.001). Conclusions: Mouth preparation frequently failed for guiding planes, retentive areas and distribution of rest seats. It is necessary to provide students with adequate clinical experience at the dental school environment, which will actually be carried into the practice of dentistry

Current trends in removable partial denture teaching in British dental schools

To investigate current teaching of removable partial denture construction in British dental schools. A questionnaire was sent by email to each of the 15 UK dental schools. Replies were received from the 12 long established schools, although one declined to participate. The more recently established schools did not respond. All schools have a pre-clinical/technical course, which either precedes or runs in parallel with the early part of the students' partial denture experience, but students complete very little, if any technical work for their clinical cases. The majority of teaching takes place in multidisciplinary teaching clinics in years 2-5 although the majority of schools concentrate teaching of the basics early in the programme. Fewer cases appear to be treated than previously reported, especially cases requiring removable partial dentures with cobalt chromium frameworks. Students may only treat one such case, the remainder of dentures being constructed of acrylic resin. Lack of experience treating cases requiring a combination of complete and removable partial dentures was a concern. Participating schools appear to meet the General Dental Council's requirements. The amount of clinical work undertaken by students may have decreased slightly. There has been a greater decrease in the technical component.

Prosthetic Rehabilitation of a Bone Defect with a Teeth-Implant Supported, Removable Partial Denture

The use of teeth-implant, mucosa-supported removable dentures for rehabilitation of partially edentulous patients involves highly complex biomechanical aspects. This type of prosthesis associates 3 kinds of support that react differently to the functional and parafunctional forces developed in the oral cavity. Although the construction of removable partial dentures may seem paradoxical when osseointegrated implants are placed, in some cases, this option is an excellent alternative to solve difficulties related to the anatomic, biologic, psychomotor, and financial conditions of the patient. This article reports on a case in which a teeth-implant, mucosa-supported removable partial denture was the option of choice for a patient with financial and anatomic limitations, having a large structural loss of the residual alveolar ridge caused by trauma by a gunshot injury at the mandible. The 5-year follow-up did not reveal any type of biomechanical or functional problem.

Evaluation of gloss changes of two denture acrylic resin materials in four different beverages

Objectives. The primary disadvantages of the materials which are used in construction of complete and removable partial dentures is that their esthetic, physical and mechanical properties change rapidly with time in the oral environment. For esthetics, color stability is one of the criteria that needs careful attention. Color may provide important information on the serviceability of these materials. Color change affects the gloss of these materials. The objective of the present study was to determine the gloss changes resulting from the testing process in four different beverages in one heat-polymerized denture base resin and one cold-polymerized denture base repair resin. Methods. Thirty-six samples were fabricated for each material. Each sample had a smooth polished and a rough unpolished surface. The gloss measurements were made with a glossmeter before testing. Four different beverages (tea, coffee, cola and cherry juice) were used for testing. Two angles of illumination (20 and 60°) were used for the gloss measurements. The samples were immersed in water, tea, coffee, cola and cherry juice solutions. The gloss of the samples was measured again with the glossmeter at the end of the 45th day and 135th day of testing. The arithmetic mean and standard deviation of each of the samples were calculated and compared with each other statistically by using the Wilcoxon test (within times)( p≤0.05 significant), the Kruskal–Wallis analysis of variance ( p≤0.05 significant) and the Mann–Whitney U-test with Bonforoni correction (when the difference between the samples was significant) ( p≤0.05 significant). Results. The results of this study revealed that gloss changes occurred after testing in heat-polymerized denture base resin and cold-polymerized denture base repair resin. The significance of the gloss changes exhibited by each sample, kept for different lengths of time in the same solution, were compared using the Wilcoxon test. The results were statistically significant ( p≤0.05). According to the Kruskal–Wallis analysis of variance, the difference between measurements for angles of illumination was statistically significant ( p≤0.05). Also according to the Mann–Whitney U-test, the difference between two polished surfaces or two unpolished surfaces was statistically insignificant ( p>0.05), but the difference between smooth polished and rough unpolished surfaces was statistically significant ( p≤0.05). Significance. It was found that either the gloss of heat-polymerized denture base resin or the gloss of cold-polymerized denture base repair resin was affected by tested agents, and the four beverages demonstrated noticeable gloss changes. Cherry juice demonstrated the least change, while tea exhibited the greatest change.

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. (J Prosthet Dent 2000;83:521-7.)

磁性アタッチメントのパーシャルデンチャーへの臨床応用 : ノンクラスプパーシャルデンチャーの製作

磁性アタッチメントのパーシャルデンチャーへの臨床応用 : ノンクラスプパーシャルデンチャーの製作

Gold alloy cast to base metal removable partial denture frameworks

For many years, gold and base metal alloys have been used in the construction of cast removable partial dentures. Each alloy has desirable properties, yet neither is ideally suited for all portions of a framework. A method has been developed to fabricate prostheses by casting gold alloy against a base metal alloy. This procedure allows the practitioner to combine the favorable characteristics of both alloys within a single framework. Consequently, the practitioner may create frameworks that more effectively meet the biomechanical demands of the oral environment.

The tooth-removable partial denture interface

During the metal finishing phase of removable partial denture construction, metal is removed from all aspects of the casting. The amount removed from areas designed to contact prepared surfaces of abutments is critical to the resulting fit of the partial. Castings were evaluated before and during finishing procedures to measure metal loss at the tooth-removable partial denture interface. Finishing and fitting techniques for controlling the loss of metal are presented.

Longitudinal study on torque transmitted from a denture base to abutment tooth of a distal extension removable partial denture with circumferential clasps.

Not only forces but also torque exerted on abutment teeth are important factors for planning the construction of distal extension removable partial dentures. The purpose of this study was to make longitudinal analysis of torque transmitted from denture base to a direct abutment tooth of these dentures with circumferential clasps. The results are summarized as follows: (i) Vertical Max. MT (maximal mean value of torque) was decreased and became constant after one or one and half months of the insertion of new dentures. (ii) Lateral Max. MT in one subject was changed from the lingual direction to the buccal direction while in another subject it was constant. (iii) In the vertical direction, there were no remarkable differences of Max. MT and Ave. T (average value of torque) between subjects. Max. MT was 5-10 x 10(-3) kgm-1 in the downward. Ave. T was 2-3 x 10(-3) kgm ss-1 in the downward and 0.3 x 10(-3) kgm ss-1 in the upward. (iv) In the lateral direction, there were considerable differences of Max. MT and Ave. T between subjects. Max. MT was less than 20 x 10(-3) kgm. Ave. MT was 2-8 x 10(-3) kgm ss-1.

An impression technique following hard palate repair using tongue grafts

Tongue-based flaps have proved to be satisfactory for closing palatal defects. The bulk of grafted tissue, however, may present problems for the prosthodontist in construction of removable partial dentures. These problems include lack of space and denture support and physical properties of the graft. Careful design of the denture is needed to optimize available space and support. An impression technique that allows differential loading of parts of the oral mucosa is described.

Porcelain-fused-to-metal crowns as replacements for denture teeth in removable partial denture construction

A procedure has been described for using porcelain-fused-to-metal crowns in place of denture teeth on a removable partial denture. Improved esthetic results are achieved when replacement denture teeth are made simultaneously with, and visually match, adjacent tooth crowns. This procedure provides a superior treatment result, particularly where multiple unilateral anterior teeth are lost and a removable partial denture is indicated.