Photoelastic Study of the Support Structures of Distal-Extension Removable Partial Dentures

Purpose: The double system of support, in which the distal-extension removable partial denture adapts, causes inadequate stress around abutment teeth, increasing the possibility of unequal bone resorption. Several ways to reduce or more adequately distribute the stress between abutment teeth and residual ridges have been reported; however, there are no definitive answers to the problem. The purpose of this study was to analyze, by means of photoelasticity, the most favorable stress distribution using three retainers: T bar, rest, proximal plate, I bar (RPI), and circumferential with mesialized rest. Materials and Methods: Three photoelastic models were made simulating a Kennedy Class II inferior arch. Fifteen dentures with long saddles, five of each design, were adjusted to the photoelastic patterns and submitted first to uniformly distributed load, and then to a load localized on the last artificial tooth. The saddles were then shortened and the tests repeated. The quantitative and qualitative analyses of stress intensity were done manually and by photography, respectively. For intragroup analyses the Wilcoxon test for paired samples was used, while for intergroup analyses Friedman and Wilcoxon tests were used to better identify the differences (p < 0.05). Results: The RPI retainer, followed by the T bar, demonstrated the best distribution of load between teeth and residual ridge. The circumferential retainer caused greater concentration of stress between dental apexes. Stress distribution was influenced by the type of retainer, the length of the saddle, and the manner of load application. Conclusions: The long saddles and the uniformly distributed loads demonstrated better distribution of stress on support structures.

Photoelastic Stress Analysis in Screwed and Cemented Implant-Supported Dentures With External Hexagon Implants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Removable Partial Denture in Combination with a Milled Fixed Partial Prosthesis as Interim Restorations in Long-Term Treatment

Interim restorations are frequently used in prosthodontic treatments. Many complex situations require the combination of fixed and removable partial prostheses. An appropriate interim restoration design that accurately implements the treatment plan is necessary to prepare the oral cavity for the prostheses, and to contribute to the preservation and health of remaining natural teeth, bone support, and gingival tissues. This report describes a modified technique for construction of interim restorations with a combination of fixed and removable partial prostheses. The technique consists of the construction of a milled fixed prosthesis and removable partial denture with metallic framework for use during extensive treatment, improving masticatory function and esthetics and preserving the periodontal health of supporting structures. This interim restoration can also serve as a template for the definitive restoration, allowing patient and dentist to evaluate appearance and function and helping to ensure the success of the definitive restoration.

Evaluation of Stress Patterns Produced by Implant-Retained Overdentures and Implant-Retained Fixed Partial Denture

The purposes of this study were to photoelastically measure the biomechanical behavior of 4 implants retaining different cantilevered bar mandibular overdenture designs and to compare a fixed partial denture (FPD). A photoelastic model of a human edentulous mandible was fabricated, which contained 4 screw-type implants (3.75 x 10 mm) embedded in the parasymphyseal area. An FPD and 3 overdenture designs with the following attachments were evaluated: 3 plastic Hader clips, 1 Hader clip with 2 posterior resilient cap attachments, and 3 ball/O-ring attachments. Vertical occlusal forces of 100 N were applied between the central incisor and unilaterally to the right and left second premolars and second molars. Stresses that developed in the supporting structure were monitored photoelastically and recorded photographically. The results showed that the anterior loading, the overdenture with 3 plastic Hader clips, displayed the largest stress concentration at the medium implant. With premolar loading, the FPD and overdenture with 3 plastic Hader clips displayed the highest stresses to the ipsilateral terminal implant. With molar loading, the overdenture with 3 ball/O-ring attachments displayed the most uniform stress distribution in the posterior edentulous ridge, with less overloading in the terminal implant. It was concluded that vertical forces applied to the bar-clip overdenture and FPD created immediate stress patterns of greater magnitude and concentration on the ipsilateral implants, whereas the ball/O-ring attachments transferred minimal stress to the implants. The increased cantilever in the FPD caused the highest stresses to the terminal implant.

Prevalence of removable partial dentures users treated at the Aracatuba Dental School - UNESP

Objectives: The aim of this study was to evaluate the frequency of removable partial dentures (RPD) at the Aracatuba Dental School.Methods: The study was conducted by analysing 412 clinical history of patients attended at the RPD clinics in the period from 2000 to 2007.Results: 412 charts were analysed: 148 (35.9%) men and 264 (64.1%) women. The mean age was 53.8 years (men) and 52.4 years (women). A total of 556 dentures were made; of these, 233 (41.90%) were maxillary and 323 (58.09%) were mandibular dentures. The most frequent Kennedy classification found was Class III (maxilla) and Class I (mandible). In the maxilla, 55% (126) of the major connectors were of the anterior-posterior palatal bar, while in the mandible, 64% (202) were the lingual bar. As regards the claps, 401 were circumferential and 318 were bar claps.Conclusion: The mean age of the patients was 52.9 years with higher prevalence of female patients; the most frequent Kennedy's classification was Class I in mandible and Class III in maxilla; the most common major connector was anterior-posterior palatal bar for maxilla and lingual bar for mandible; the circumferential clasps were the most common retainer used in both jaws.

Evaluation of the influence of location of osseointegrated implants associated with mandibular removable partial dentures

Purpose: The aim of this research was to assess, by means of, the bi-dimensional finite element method, the best implant location in the alveolar edge, through stress distribution and support structure displacement of a distal extension removable partial denture associated with an osseointegrated implant of 10.0 x .75 mm, acting as abutment for the denture base.Methods and Materials: Five models in sagittal cut were used to represent: model A-hemi arch containing natural tooth 33 and the distal alveolar edge; model B-similar to model A, but with a conventional removable partial denture to replace the absent teeth; model C (MC)-similar to the previous one, with an implant in the distal region of the edge under the denture base; model D-similar to MC, with the implant in the central region of the edge; model E-similar to MC, with an implant in the mesial region of the edge. With the aid of the finite element program ANSYS 8.0, the models were loaded with strictly vertical forces of 50 N on each cusp tip. Displacement and von Mises Maps were plotted for visualization of results.Results: The introduction of implant diminished the tendency of intrusion of the removable partial denture in all situations. The maximum stress was observed on implant in all situations. Approximating implant in direction of support teeth was benefit for stress distribution.Conclusion: Model D presented the lowest value for maximum tendency to displacement when compared with those found in the other models; model E demonstrated better relief with regard to demand from the abutment tooth; locating the implant near of the abutment tooth influenced positively the distribution of stresses on the analyzed structures.

Photoelastic Analysis of Biomechanical Behavior of Single and Multiple Fixed Partial Prostheses With Different Prosthetic Connections

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Correlation between factors associated with the removable partial dentures use and Candida spp. in saliva

Objectives: To correlate the presence and number of Candida spp. in the saliva of wearers of removable partial dentures retained with precision attachments with the proportion of metal/acrylic resin present in the dentures. Methods: Saliva samples from 40 removable partial denture wearers (test) and one paired sample of individuals, non- wearers of any type of removable denture (control) were collected, seeded, and the colony forming units of Candida counted and identified. The metal/acrylic resin proportion of each denture was quantified, using silicone plates pressed over each denture. Results: Candida spp. was found in the saliva of 80% of the individuals in the test group and 65% of the control, with C. albicans being themost prevalent species. The test group presented with the highest number of colony forming units of Candida per ml of saliva, and there wasweak correlation between this number and the metal and resin area of the denture (Pearson's coefficient of correlation). Greater prevalence and a higher number of colony forming units of Candida per ml of saliva occurred in removable partial denture wearers ( p = 0.04) with a weak positive correlation between the metal and resin area and the number of colony forming units of Candida per ml of saliva. However, this correlation was more significant for the area of resin. Correlation between factors associated with the removable partial dentures use and Candida spp. in saliva

Influence of length and diameter of implants associated with distal extension removable partial dentures

PURPOSE

Association of fixed partial denture and gingival prosthesis as alternative approach to recover esthetics and function in anterior maxillary region

Tooth replacement in the maxillary anterior region is especially difficult when the loss includes significant amounts of the residual ridge and the soft tissue. Several techniques are available, such as dental implants or fixed partial denture, and bone and gingival grafts or gingival prostheses, respectively. This article showed a clinical case of an elderly who was treated with a collarless metal-ceramic fixed partial denture and acrylic removable gingival prosthesis to recover the esthetics in the maxillary anterior region. The association of a metal-ceramic fixed denture and gingival prosthesis was an excellent alternative in cases when surgical procedures are contraindicated. © 2012 Japan Prosthodontic Society.

Failures in the rehabilitation treatment with removable partial dentures

Background. Despite being functional and having aesthetic benefits, the acceptance of patients regarding the use of removable partial dentures (RPDs) has been low. In part, this is due to the deleterious effects that causes discomfort to the patient. Success depends not only on the care expended by the patient, including daily care and oral hygiene, but also on common goals set by their professional and clinical staff, aiming beyond aesthetics, to incorporate issues of functionality and the well-being of patients. Methods and results. For rehabilitation treatment with RPDs to reach the desired level of success without damaging the support structure, all the steps (diagnose, cavity preparation, adaptation of the metal structures, functional of distal extension and posterior follow-up) in the rehabilitative treatment should be carefully developed. A literature review was carried out, searching through MEDLINE (PubMed) articles published between 1965 and December 2012 including clinical trials and reviews about the use of RPDs. Conclusions. This study describes factors that lead to failures and complications in oral rehabilitation through the use of RPDs and suggests possible solutions.

Microstrain Around Dental Implants Supporting Fixed Partial Prostheses Under Axial and Non-Axial Loading Conditions, In Vitro Strain Gauge Analysis

The current study used strain gauge analysis to perform an in vitro evaluation of the effect of axial and non-axial loading on implant-supported fixed partial prostheses, varying the implant placement configurations and the loading points. Three internal hexagon implants were embedded in the center of each polyurethane block with in-line and offset placements. Microunit abutments were connected to the implants using a torque of 20 N.cm, and plastic prosthetic cylinders were screwed onto the abutments, which received standard patterns cast in Co-Cr alloy (n = 10). Four strain gauges (SGs) were bonded onto the surfaces of the blocks, tangentially to the implants: SG 01 mesially to implant 1, SG 02 and SG 03 mesially and distally to implant 2, respectively, and SG 04 distally to implant 3. Each metallic structure was screwed onto the abutments using a 10-N.cm torque, and axial and non-axial loads of 30 kg were applied at 5 predetermined points. The data obtained from the strain gauge analyses were analyzed statistically through the repeated measures analysis of variance and the Tukey test, with a conventional level of significance of P < 0.05. The results showed a statistically significant difference for the loading point (P = 0.0001), with point E (nonaxial) generating the highest microstrain (327.67 mu epsilon) and point A (axial) generating the smallest microstrain (208.93 mu epsilon). No statistically significant difference was found for implant placement configuration (P = 0.856). It was concluded that the offset implant placement did not reduce the magnitude of microstrain around the implants under axial and non-axial loading conditions, although loading location did influence this magnitude.

Impact of Replacing Conventional Complete Dentures with Implant-Supported Fixed Complete Dentures

The aim of this study was to assess the impact of replacing conventional mandibular complete dentures with implant-supported fixed complete dentures (ISFDs) on the oral health related quality of life (OHOOL) of edentulous patients and on the associated kinesiographic parameters. The patients had their complete dentures replaced by ISFDs and were assessed after 1, 2, 3, 6, and 12 months. An improvement of general OHQOL was observed 2 months after treatment with ISFDs. Kinesiographic recordings revealed significant mandibular vertical and horizontal opening increases and a greater vertical intrusion of the maxillary complete dentures during clenching after the treatment with ISFD.