Retention Of Removable Partial Dentures Research Articles

Finite Element Evaluation of the Effect of Adhesive Creams on the Stress State of Dentures and Oral Mucosa.

The base fit between a removable partial denture (RPD) and the underlying soft tissue plays a significant role in its performance. The application of a denture adhesive is hypothesized to result in better retention of RPDs and, as a result, contribute to lower stress on the oral mucosa. The objectives of this study were to observe and compare the distribution of simulated bite forces applied to the RPD through the abutments and soft tissue for models with and without the use of a denture adhesive. Furthermore, we evaluated the possible benefit of using a denture adhesive in lowering stresses on the oral mucosa. The RPD, mandible, oral mucosa, abutment teeth supporting the RPD, and the corresponding abutment periodontal ligaments (PDLs) were modelled as 3D volumes based on computer tomography (CT) datasets. A viscoelastic adhesive layer between the RPD and oral mucosa was incorporated into this base model using Prony series approximation. The layer was developed as a volume extract using the denture surface. Finite element (FE) simulations were performed for the bite force on one of the RPD segments, with the resulting force and moments experienced by the dental structures and oral mucosa compared between the model with the adhesive layer and the base model without. As a result, the contact pressure on the oral mucosa for the model with the denture adhesive decreased to 0.15 MPa as compared to 0.25 MPa for the model without the adhesive. The potential role of denture adhesives in leading to a better fit between the RPD and oral mucosa as well as lowering contact pressures could be used to improve comfort in patients wearing RPDs.

Retention of Removable Partial Denture Fabricated by Digital Designing and 3D Printing Technology - A Cross Over Study

Retention of Removable Partial Denture Fabricated by Digital Designing and 3D Printing Technology - A Cross Over Study

Determining the retention of removable partial dentures

Statement of problemRemovable partial dentures (RPDs) provide a cost-effective treatment for millions of partially edentulous patients worldwide. However, they often fail because of loss of retention. One reason for this problem is lack of precise guidelines for designing retentive RPDs. PurposeThe purpose of this in vitro study was to determine the forces produced by food and clasps during mastication to develop an algorithm for predicting RPD retention and to help determine the optimal number of clasps. Material and methodsThe forces that food exerts on acrylic resin teeth during simulated mastication and the retention forces provided by clasps (wrought wire, circumferential, and I-bar) engaging on teeth were measured using a universal testing machine. A statistical analysis was performed with a 1-way ANOVA and repeated-measures ANOVA while the developed algorithm was evaluated by using sensitivity and specificity analysis. ResultsThe force exerted by food mastication on each individual tooth ranged between 1.7 and 12.2 N, depending on the type of tooth, tooth anatomy, occlusion, and food. The retention force of the clasps after cyclic testing ranged between 2.9 and 14.5 N, depending on the type of tooth abutment and clasp. Using these measurements, an algorithm was developed to predict RPD retention. The algorithm was confirmed experimentally on 36 RPDs, showing a sensitivity of 96%, specificity of 100%, and an accuracy of 97%. ConclusionsThe forces generated by food mastication on teeth varied according to the type of tooth, occlusion, and food. The retention force of RPD clasps varied according to the type of tooth and clasp. An algorithm for predicting RPD retention and determining the optimal number of clasps was developed and validated experimentally.

Retention of removable partial dentures

Retention of removable partial dentures

EVALUATION OF RETENTION OF TOOTH-COLORED VERSUS CAST METAL DENTAL CLASPS FOR A MANDIBULAR DISTAL EXTENSION PROSTHESIS

The aim of this study was to compare the retention of two different forms of clasps in mandibular distal extension prosthesis, which were; the Conventional casted metal clasps & the Tooth-colored acrylic resin clasps “Acetal resin”.Materials & Methods: For the rationale of this clinical investigation, fifteen patients were selected from the Outpatient Clinic of the Prosthodontic Department, Faculty of Oral and Dental medicine, Cairo University in accordance with certain criteria. Every patient got a skeleton parial denture that was constructed in a conventional manner. A hole was made in the middle of the lingual plate during fabrication of the framework; A Retention Measuring-Aided Device was made to allow attachment of the digital Forcemeter to this hole for measuring retention. Then, the metal clasp was removed and replaced by acetal resin clasp and the same procedures of measuring retention were performed in the same manner. Retention of the two clasp types was measured four times (at time of insertion, one month, two months and three months, respectively), by the aid of a prefabricated device (The Retention Measuring-Aided Device) for precise reproducible measurement.Results: There was a statistically significant difference (P ≤ 0.05) in the mean Forcemeter measurements from base line to one month. Later, from one month to 2 months and from 2 months to 3 months; there was a statistically insignificant difference (P ≥ 0.05) in the mean Forcemeter measurements. Conclusions and recommendations: Using Tooth-colored dental clasps would not compromise the retention of removable partial denture and can help to enhance the esthetics of removable partial dentures.

Rehabilitation of a crossed-occlusion patient using implant-assisted removable partial denture with Locator® attachment: A case report

In crossed occlusion, displacement of removable partial denture is likely to occur during function due to different characteristics of abutment and supporting tissue. It increases discomfort to the patient. In addition, adverse effect on the residual ridge and abutment can induce an unfavorable prognosis of the denture. In this case, a small number of implants can be placed in strategic locations. Attachment can be added for additional support and retention of removable partial denture assisted by implants. This article describes the rehabilitation of a crossed occlusion patient using implant-assisted removable partial denture with Locator(R) attachment. After 24 months, the patient was satisfied with the aesthetic and function of the prosthesis that is maintained stable.

In Vitro Comparative Study of Retention of Maxillary Kennedy Class I Removable Partial Denture Retained with Four Different Designs of Esthetic Clasps

To study the effect of clasp, design, material, and amount of retentive undercut of esthetic clasp on retention of removable partial dentures restoring maxillary Kennedy class I removable partial denture.

The path of placement of a removable partial denture: a microscope based approach to survey and design.

This article reviews the topic of how to identify and develop a removable partial denture (RPD) path of placement, and provides a literature review of the concept of the RPD path of placement, also known as the path of insertion. An optimal RPD path of placement, guided by mutually parallel guide planes, ensures that the RPD flanges fit intimately over edentulous ridge structures and that the framework fits intimately with guide plane surfaces, which prevents food collecting empty spaces between the intaglio surface of the framework and intraoral surfaces, and ensures that RPD clasps engage adequate numbers of tooth undercuts to ensure RPD retention. The article covers topics such as the causes of obstructions to RPD intra-oral seating, the causes of food collecting empty spaces that may exist around an RPD, and how to identify if a guide plane is parallel with the projected RPD path of placement. The article presents a method of using a surgical operating microscope, or high magnification (6-8x or greater) binocular surgical loupes telescopes, combined with co-axial illumination, to identify a preliminary path of placement for an arch. This preliminary path of placement concept may help to guide a dentist or a dental laboratory technician when surveying a master cast of the arch to develop an RPD path of placement, or in verifying that intra-oral contouring has aligned teeth surfaces optimally with the RPD path of placement. In dentistry, a well-fitting RPD reduces long-term periodontal or structural damage to abutment teeth.

A retrospective clinical study of implant-retained prosthetic partial dentures: A follow up investigation

Aim: To evaluate the 5-year follow up of implants placed in partially edentulous patients restored with removable partial dentures. Materials and Methods: In this retrospective study, survival rates and clinical outcomes of implants placed for retention of removable partial dentures in 36 partially edentulous patients were observed. Results: The survival rate of the implants after a 5-year follow up was 98%. The clinical mean scores for plaque, calculus, gingivitis and bleeding were very low at all evaluation periods. Significant differences between results at successive time periods can be observed only between the plaque index at 1 year and the plaque index at 5 years. Peri-implant probing demonstrated a deepening of pockets over time. However, the changes were not statistically significant between the two evaluation periods. During the first year of function an average attachment loss of 0.4 mm was observed. During the next 4 years the average progression of PPD was about 0.1 mm per year. Conclusion: After 5 years, implants retaining removable partial dentures showed good survival rates and clinical stability. Using implants is a good solution to improve the satisfaction of patients with removable partial dentures; nonetheless this prosthetic solution demands strict surveillance of the patient and is time consuming for the clinician.

Lingual Retention and the Elimination of the Visible Clasp Arm

The modern removable partial denture (RPD), in response to the increased esthetic demands of our patients, is no longer acceptable if it requires visible buccal and facial clasp arms for retention. By eliminating the bracing arm and having its functions taken by paralleled guide planes and precise, positive rests, the retentive element, a lingual circumferential wire clasp arm, will provide the same amount of retentive force as if it were placed on the buccal surface and will not be visible. Designs for the major connector either plate the lingual surface of the abutment or, as in a lingual bar, leave that surface open. Both of these situations are adaptable to the lingual retentive clasp and are illustrated in this article. Design features such as metal clasps needed for the retention of RPDs can be very unsightly, creating an esthetic problem. This article reviews the concepts for creating lingual clasp arms that enhance the esthetic quality of prostheses.

Retention of removable partial denture with double crowns

The aim of this paper is to explain the mechanisms of retention with double crowns, examine the possibility of improving the process of measuring the forces of separating double crowns and suggest the measures for optimizing the retention forces with telescopic partial dentures. After the manufacturing of a partial denture with double crowns, it can only be established whether if the retention force is strong enough or not, but its nominal value remains unknown. Optimally it should be between 5 and 10N per anchor. Too strong retention force of partial denture causes traumatic damages of periodontal tissues, when taking the denture off, while not enough strong retention force doesn't connect the partial denture to the supporting tissues tightly enough. The paper describes the mechanism of retention with telescope and conus crowns and the way of measuring the force of their separation. For the purpose of optimizing the retention force, the ways of reducing exceedingly strong and increasing insufficient force were described. The necessity of being acquainted with the nominal value of the retention force of telescopic denture and its bringing to within the borders of optimal force is stressed in the conclusion.

Retention of removable partial denture with double crowns

The aim of this paper is to explain the mechanisms of retention with double crowns, examine the possibility of improving the process of measuring the forces of separating double crowns and suggest the measures for optimizing the retention forces with telescopic partial dentures. After the manufacturing of a partial denture with double crowns, it can only be established whether if the retention force is strong enough or not, but its nominal value remains unknown. Optimally it should be between 5 and 10N per anchor. Too strong retention force of partial denture causes traumatic damages of periodontal tissues, when taking the denture off, while not enough strong retention force doesn't connect the partial denture to the supporting tissues tightly enough. The paper describes the mechanism of retention with telescope and conus crowns and the way of measuring the force of their separation. For the purpose of optimizing the retention force, the ways of reducing exceedingly strong and increasing insufficient force were described. The necessity of being acquainted with the nominal value of the retention force of telescopic denture and its bringing to within the borders of optimal force is stressed in the conclusion.

An impression technique for optimal positioning of precision attachments for removable partial dentures

Precision attachments such as the Dalbo attachment (Cendres & Métaux SA, Biel-Bienne, Switzerland) soldered to a post and core, significantly enhance the retention of removable partial dentures.1 Their use eliminates the need for visible retentive and support components, especially in esthetic areas.2 Optimal positioning of the attachment should be in harmony with the path of insertion of the planned prosthesis.2 An impression technique that facilitates optimal location of the attachment is described.

Emergency repair of a fractured dowel-retained precision attachment for a removable partial denture

J Prosthet Dent 2001;86:320-1.

Effect of water and artificial saliva on the low cycle fatigue resistance of cobalt-chromium dental alloy

Statement of problem. Fatigue of denture clasp alloys causes clasp failures and decreases the retention of removable partial dentures. Little information is available on how the environment (dry, water, artificial saliva) effects the fatigue behavior of cast cobalt-chromium alloy clasps. Purpose. This study determined the effect of water and the artificial saliva on the resistance of cast cobalt-chromium alloy to the deflection fatigue. Material and methods. Test bars (n = 10) were tested either dry, in water, or in artificial saliva (Fusayama type) with a constant deflection fatigue test. The number of loading cycles before fracture was registered as resistance to fatigue. To establish whether there were indications of alloy corrosion occurring during the fatigue test, the testing liquid was analyzed retrospectively with an atomic absorbance spectroscopy. To determine elemental composition of the fracture surface, fracture surfaces of the test bars were analyzed with a scanning electron microscope and energy dispersive spectroscopy. Results. The bars that were tested dry had a mean fatigue resistance of 78,000 loading cycles, whereas test specimens tested in artificial saliva had a resistance of 59,000 loading cycles and 36,000 for those tested in water. Atomic absorbance spectroscopy revealed small amounts of cobalt (Co) in testing water and in artificial saliva. Energy dispersive spectroscopy analysis revealed differences in elemental composition of a fatigue fracture surface compared with that of a 1-bend fracture. Conclusions. The results suggest that both water and artificial saliva reduce the fatigue strength of cobalt-chromium alloy, explained by corrosion of the alloy in the wet environment. (J Prosthet Dent 1998;80:708-13.)

The physical properties of a polyacetal denture resin

A polyacetal injection-moulded resin is being marketed for the construction of retentive and supportive components of removable partial dentures (RPDs). Specimens of poly(oxymethylene) cast by commercial laboratories were tested to examine the following physical characteristics: the modulus of elasticity in compression, extension and flexure, stress relaxation, the force displacement behaviour of clasp forms, impact strength and glass transition temperature. Results showed that the material has a flexural modulus lower than that of poly(methylmethacrylate) and is insufficiently rigid to be used as a supporting element for partial dentures. Resin clasps may be resilient enough to engage undercuts for the retention of RPDs but the low flexural modulus requires that the resin be used in greater cross-sectional area than metal alloys in order to gain useful retention. This greater bulk has implications for plaque accumulation and maintenance of periodontal health.

The effect of reducing the number of clasps on removable partial denture retention

Retention to a master model of 10 nominally identical chrome-cobalt removable partial denture castings with standardized bilateral molar and premolar clasps engaging 0.25 mm (0.01 inch) undercuts and 10 castings with clasps engaging 0.5 mm (0.02 inch) undercuts was measured on an Instron testing machine. The retention of each framework was remeasured as the clasps were removed in one of two sequences. Differences between frameworks, number of clasps, and depth of undercuts were all significant. The order of removal of the clasps was not statistically significant. In a separate experiment the position of the dislodging force was found to be significant. It was concluded that the dislodging force was dependent on (1) the fit of the framework, (2) the depth of the undercut, (3) the number of clasps, and (4) its point of application.

Finite Element Analysis of the Relationship between Clasp Dimensions and Flexibility

A parameter study with use of the finite element method was conducted for examination of the relationships between the shape parameters of a clasp (width and thickness at the base and tip of the clasp) and its displacement or stress. By synthesis of these relationships, a simple formula defining the clasp tip displacement in terms of clasp dimensions ("displacement formula") was obtained. A stiffness parameter "Fd" (the load producing a 1-mm displacement of the clasp tip) was proposed, and a formula defining Fd in terms of shape parameters was derived from the displacement formula. Fd would be a practical parameter for the definition of clasp retention, and the present formulae appear to be useful tools for investigation of the retention of removable partial dentures.

Significance of abutment tooth angle of gingival convergence on removable partial denture retention

The angle of gingival convergence is one of the many factors that influence the retention capability of removable partial denture clasps. A geometric evaluation of the retention properties of this angle has been presented.

Use of spring-loaded attachments for retention of removable partial dentures

Where conventional clasping will result in poor esthetics, a simple alternative means of retention is available in the form of an attachment with a spring-loaded plunger. Careful placement of the attachment is important to provide effective retention and to prevent tooth movement.