Direct Retainers Research Articles

Removable Partial Denture with dual path of insertion: clinical case report

Removable Partial Dentures (RPD) with dual path of insertion are designed to overcome conventional RPD esthetic limitations, through the use of proximal undercuts for rigid direct retainers. Therefore, dual path RPD is considered a variation of conventional RPD. This paper reports a clinical case where proper function as well as excellent esthetics were obtained with this type of RPD.

Finite element analysis of implant-assisted removable partial dentures: Framework design considerations

Statement of problemConnecting an acrylic resin base to both a metal framework and a rigidly fixed implant may affect the rotational displacement of the prosthesis during loading. PurposeThe purpose of this finite element analysis study was to analyze the effect of connecting a denture base metal framework to an implant with the aim of decreasing the rotational movement of an implant-assisted removable partial denture. Material and methodsA mesial occlusal rest direct retainer and a distal occlusal rest direct retainer were modeled and adapted to incorporate a modified denture base metal framework in the connection area for each model. The stress and deformation patterns of the prosthesis structure were determined using finite element analysis and compared for both situations. ResultsA maximum von Mises stress of 923 MPa was observed on the metal framework of the prosthesis with a mesial occlusal rest, and the maximum value was 1478 MPa for the distal occlusal rest. A maximum von Mises stress of 17 MPa occurred on the acrylic resin denture base for the mesial occlusal rest, and a maximum von Mises stress of 29 MPa occurred for the distal occlusal rest. ConclusionsThe distal occlusal rest direct retainer is stiffer than the mesial design and undergoes approximately 66% less deformation. The modified denture base framework with an I-bar and distal occlusal rest design provides more effective support to the acrylic resin structure.

The effects of loading locations and direct retainers on the movements of the abutment tooth and denture base of removable partial dentures.

The purpose of this study was to evaluate the degree and amount of movement of the abutment tooth and denture base influenced by the direct retainer of distal extension removable partial denture and the location of functional loading, then to suggest direct retainer design with minimal adverse effect and with optimum functional loading location for residual tissue. The displacement of the abutment tooth and inclination of the denture base were determined, with 30 N as work load utilizing simulation model and strain gauge system, about two types of direct retainers with mesial or distal rest and nine loading points on denture base. Displacement and inclination was determined with the one-way analysis of variance and Scheffe's multiple test was performed. The results revealed that type of direct retainer influenced on the magnitude rather than direction of the abutment tooth displacement. The distal displacement of abutment tooth was significantly less in Type M clasp (with mesial rest and connection) than in Type D clasp (with distal rest and connection) (p<0.05). The location of loading points influenced both of the magnitude and direction of the abutment tooth and denture base movement. Posterior and lingual loading resulted in significantly distal displacement of abutment tooth (p < 0.05).

MARGINAL BONE LEVEL EVALUATION OF IMPLANT SUPPORTED KENNEDY CLASS I PARTIAL OVERDENTURE USING TELESCOPIC CROWNS VERSUS ACETAL RESIN CLASPS DIRECT RETAINERS

Objectives : This study was conducted to evaluate and compare marginal bone level for abutments of implant supported Kennedy class I partial overdenture using Telescopic Crowns versus acetal resin clasps direct retainers after 18 month of clinical use. Materials & methods : Ten male partially edentulous patients (Kennedy class I) with the premolars are the last standing abutments were selected and all patients were rehabilitated with metallic partial denture supported by two osseointegrated implants one on each side of the lower arch positioned in the area of second molar and were randomly divided into two equal groups according to type of abutments retainers ,Group I; Patients were rehabilitated with Tooth Implant Supported partial overdenture with two telescopic crowns ,Group II; Patients were rehabilitated with Tooth Implant Supported partial overdenture with two Acetal Resin clasps direct retainer on each side. Evaluation by measuring marginal bone level for main abutments was made at the time of insertion, after 6 month ,after 12 month and last after 18 month using radiographic evaluation. Results: partial overdentures retained by telescopic crowns showed significant increase in marginal bone loss as compared with Acetal resin clasps retainers. Conclusion: using tooth implant partial overdentures retained by Acetal resin clasps shows better effect on supporting structure as compared by partial dentures with telescopic crowns retainers.

Assessment of the structural components of removable partial dentures

AIM: The aim of this study was to assess the mechanical and planning failures of the structural components of tooth-supported and tooth-mucosa-supported removable partial dentures (RPDs). MATERIAL AND METHODS: We evaluated the following components of fifty removable partial dentures: direct retainers (niche, support, retention arm, opposition arm, position on the abutments, type of retainers selected), indirect retainers (position, necessity, and niche), acrylic saddle, major connector, insertion axis and interference of muscles and nerves, which were classified into adequate and inadequate. RESULTS: There was a statistically significant difference between tooth-supported and tooth-mucosa-supported dentures when the major connector was considered. CONCLUSION: The major component failures were the following, in descending order: maintenance of the prosthesis, niche, insertion axis, and acrylic base.

The Detection of BANA Hydrolysis Activity in Abutment Teeth in Patients with Removable Partial Denture

ABSTRACT Purpose The aim of this study was to detect the presence of N-benzyl-Dl-arginase-2-naphthalamide (BANA) micro- organisms in chronic periodontitis of abutment teeth in subjects wearing removable partial dentures (RPDs) by measuring the red complex using BANA-ZymeTM test. Materials and methods Twenty-five subjects (mean age: 59.3 years) with Kennedy class II partially edentulous arch participated in this study. The microbiological record of red complex was done by BANA-Zyme kit and clinical parameters, such as plaque index (PI), gingival index (GI) and probing depth were recorded at abutment teeth in contact with the direct retainer of unilaterally designed RPDs and the corresponding nonabutment teeth on the opposite side. Results Mean scores of BANA for the red complex, PI and GI of the abutment teeth were significantly greater than those of the nonabutment teeth (p &lt; 0.01). No significant mean difference in pocket depth (PD) was found between the abutment and nonabutment teeth. Logistic regression analysis revealed that abutment teeth, high scores of PI and a maintenance interval longer than 6 months were significant predictors for positive red complex scores (p &lt; 0.05). Conclusion These results suggest that the microbiological risk for periodontitis of abutment teeth is greater than that for nonabutment teeth in RPD wearers. How to cite this article Kalaria JP, Patel BG, Patel V, Agrawal C. The Detection of BANA Hydrolysis Activity in Abutment Teeth in Patients with Removable Partial Denture. Int J Prosthodont Restor Dent 2015;5(2):31-37

Esthetic Cast Direct Retainers for Distal Extension Removable Partial Dentures

Extra coronal cast direct retainers are an essential component of cast removable partial denture prosthesis. The conventional cast circumferential clasp or the bar clasp appear unaesthetic due to visible metal display when used in the smile zone. This article describes two hidden clasp designs as an alternative to the conventional extra coronal cast direct retainer assembly for the distal extension partially edentulous situation. The same is highlighted via two case reports.

A simplified classification system for partially edentulous spaces

Background: There is no single universally employed classification system that will specify the exact edentulous situation. Several classific ation systems exist to group the situation and avoid confusion. Classifications based on edentulous areas, finished restored prostheses, type of direct retainers or fulcrum lines are there. Some are based depending on the placement of the implants. Widely accepted Kennedy Applegate classification does not give any idea about length, span or number of teeth missing. Rule 6 governing the application of Kennedy method states that additional edentulous areas are referred as modification number 1,2 etc. Rule 7 states that extent of the modification is not considered; only the number of edentulous areas is considered. Hence there is a need to modify the Kennedy -Applegate System. Aims: This new classification system is an attempt to modif y Kennedy -Applegate System so as to give the exact idea about missing teeth, space, span, side and areas of partially edentulous arches. Methods and Material: This system will provide the information regarding Maxillary or Mandibular partially edentulous arches, Left or Right side, length of the edentulous space, number of teeth missing and whether there will be tooth borne or tooth - tissue borne prosthesis. Conclusions: This classification is easy for application, communication and will also help to desi gn the removable cast partial denture in a better logical and systematic way. Also, this system will give the idea of the edentulous status and the number of missing teeth in fixed, hybrid or implant prosthesis.

Connectors and attachments in oral rehabilitation

Connectors, the term itself indicates connection or something that connects one thing to the other. In fixed Prosthodontics, connector refers to the portion of a fixed partial denture that unites the retainer and pontic. For two things to be joined together there should be a medium for it. In other words, something that will connect them together to make them look as one. In removable Prosthodontics, connectors are the one which unite the components: Major connector - that connects the components from one side of the arch to the other side of the arch. Minor connectors - the connecting link between the major connector or base of removable partial denture and other units of the prosthesis such as clasps, indirect retainer and occlusal rest. Precision attachments are special type of direct retainers used in partial denture construction. By definition, the term precision denotes 'the quality or state of being precise'. They are sometimes said to be a connecting link between the fixed and removable type of partial dentures as it incorporates features common to both types of construction. This article brings a case report of using the connectors and attachment for oral rehabilitation.

English

A unique concern of a removable denture when compared to others is retention. Retention is the ability of the prosthesis to resist the movement of denture away from the supporting tissues/teeth. The component of removable denture which provides retention is called as direct retainer. 1,3,4 A direct retainer can be either an extracoronal or intracoronal retainer. Extracoronal direct retainer uses mechanical resistance to displacement through components placed on external surface of abutment teeth. Intracoronal retainer is either cast or attached totally within the restored natural contours of an abutment tooth.1 One of the main drawbacks of extracoronal retainers used in partial dentures is visibility. Many patients find themselves in an aesthetically compromised state when these retainers are placed on teeth in visible area. Precision attachments provide solution for this problem. Also, precision attachments provide better vertical support and better stimulation to the underlying tissue through intermittent vertical massage. 1,9 Although the history of intracoronal retainers goes back to 5 th and 4 th centuries BC, technically more sound developments began in early 20 th century AD, with Dr. Herman E. S. Chayes formulating the principle of internal attachment in 1906. Since then precision attachments are playing an important role in removable and fixed partial denture, conventional and implant supported overdenture. 9

Repair of Extracoronal Direct Retainers

ABSTRACT Fractures of the clasp components of removable partial dentures are commonly encountered problems in the dental office. Repair or replacement procedures are therefore, often required and may be preferred over refabrication of the entire prosthesis when it is possible to maintain the denture to serve its purpose of function, esthetics and comfort after repair. This paper reviews various procedures that can be used to repair or replace clasp components in order to produce a clinically acceptable result. How to cite this article Amin BM, Aras MA. Repair of Extracoronal Direct Retainers. Int J Prosthodont Restor Dent 2012;2(1):42-46.

Oral health status of patients after replacement of removable partial dentures after three years

Objective(s): To assess the effect of removable partial dentures on the abutment teeth in comparison with that of theremaining dentition, and to investigate the effect of regular check up on periodontal health for patients using thistype of prosthesis.Methodology: One hundred patients wearing removable partial dentures for at least three years included in thestudy. Teeth used as direct or in direct retainers for the removable partial denture were considered as the studygroup, while the remaining dentition in the same jaw was considered as the control group. The following periodontalparameters were registered for each tooth, plaque and gingival indices, clinical attachment level and tooth mobility.Patients were divided into two groups as regular and irregular attendants.Results: Among the 100 patient, 30 were regular attendants. A significant difference in clinical attachment level andplaque accumulation was detected between study and control group of teeth. In addition there was a statisticallysignificant difference in all periodontal parameters between regular and irregular attendantsResults: Among the 100 patient, 30 were regular attendants. A significant difference in clinical attachment level andplaque accumulation was detected between study and control group of teeth. In addition there was a statisticallysignificant difference in all periodontal parameters between regular and irregular attendants.Recommendations: The Patient palaces for removable partial denture must maintain visits so we can check theremovable partial denture and supporting teeth for any problem. Also, call for an appointment as soon as you developany problem with your denture.

Influence of removable partial dentures on the formation of dental plaque on abutment teeth

This study aimed to clarify the relation between the shape of the retainers and the plaque formation on abutment teeth to improve the denture design. This study observed the buccal surface for the clasps and distoproximal surface for a guide plate of the mandibular first premolar which was the abutment tooth with a direct retainer of a distal extension RPD. The buccal surface was observed in 10 subjects and the distoproximal surface in 14 subjects. The latter cohort was divided into two groups (the group with an open type guide plane and a close type guide plane). All subjects provided their informed consent. The state of plaque accumulation was inspected by standardized photography and bacterial quantification and compared among the cast circumferential (CC), Ibar, wire circumferential (WC) and control (no clasps) in individuals regarding the buccal surface and between the groups with the open type and close type guide plane of the distoproximal surface. No significant differences were observed among the CC, Ibar, WC and control (P>0.05) regarding the buccal surface, while in regard to the distoproximal surface, the group with the open type guide plane had significantly more plaque than the group with the close type guide plane (P<0.05). The plaque formation on the buccal surface is not dependent on the types of clasps. It is effective to prepare a guide plane as close to the gingival margin as possible to reduce the plaque accumulation on the distoproximal surface.

Microbiological risk for periodontitis of abutment teeth in patients with removable partial dentures

Tannerella forsythia, Porphyromonas gingivalis and Treponema denticola are identified as the red complex which exists in high proportions in periodontally diseased patients. The aim of this study was to assess the microbiological risk for periodontitis of abutment teeth in subjects wearing removable partial dentures (RPDs) by measuring the red complex using BANA-ZymeTM test. Thirty-eight subjects (mean age: 62.2 years) with Kennedy Class II partially edentulous arch participated in this study. The red complex and clinical parameters, such as plaque index, gingival index, probing depth and tooth mobility were recorded at abutment teeth in contact with the direct retainer of unilaterally designed RPDs and the corresponding non-abutment teeth on the opposite side. Mean scores for the red complex, plaque index, gingival index and tooth mobility of the abutment teeth were significantly greater than those of the non-abutment teeth (P < 0.01). No significant mean difference in pocket depth was found between the abutment and non-abutment teeth. Logistic regression analysis revealed that abutment teeth, high scores of plaque index and a maintenance interval longer than 6 months were significant predictors for positive red complex scores (P < 0.05). These results suggest that the microbiological risk for periodontitis of abutment teeth is greater than that for non-abutment teeth in RPD wearers.

Failure of extracoronal direct retainers: Causes and preventions

Failure of removable partial denture may be attributed to several factors, one of which is failure of extra coronal direct retainer. Direct retainers can serve for a long time if designed and fabricated properly by the dentist and maintained well by the patient. This article is the review of causes of failure of extra coronal direct retainers and prevention of the same.

Reconsideration of the Fertility of the Hatamoto,Direct Retainers of the Shogun

Reconsideration of the Fertility of the Hatamoto,Direct Retainers of the Shogun

Effect of direct retainer and major connector designs on RPD and abutment tooth movement dynamics

Designs of removable partial dentures are suggested to affect the mobility of abutment teeth and removable partial denture (RPD) during oral functions. This study aimed to examine the effect of direct retainer and major connector designs on RPD dynamics under simulated loading. Six different Kennedy class II maxillary RPDs were fabricated on a maxillary model. These dentures involved 3 different direct retainers (wrought-wire clasp, RPA clasp, and conical crown telescopic retainer) and 2 different major connectors (Co-Cr major connector and heat-cured acrylic resin with a metal strengthener). Using an experimental model with simulated periodontal ligaments and mucosa that were fabricated using silicone impression material, three-dimensional displacements of the RPDs were measured under a simulated 30-N loading with a displacement transducer type M-3. Significant effects of "direct retainer design" on bucco-palatal displacements and "major connector" on mesio-distal displacements were revealed by 2 x 3 two-way analysis of variance of abutment teeth movements (P < 0.001 and P = 0.002, respectively). Additionally, analysis of variance of RPD displacements revealed significant effects of "direct retainer design" on corono-apical displacements and "major connector" on mesio-distal displacements (P = 0.001 and P = 0.028, respectively). Rigid direct retainers and rigid major connectors decrease the movements of both abutment tooth and RPD.

A systematic method for designing removable partial denture framework

Designing a removable partial denture framework can be complicated for students and dentists. This article suggests a simple and systematic method for the process. In this method, the designing sequence outlines (1) rests, (2) minor connectors and proximal plates, (3) retentive meshwork, (4) major connector, (5) direct retainers, and (6) indirect retainers, respectively.

A laser pointer surveyor to detect an undercut in fixed partial denture preparation

1. Rudd RW, Bange AA, Rudd KD, Montalvo R. Preparing teeth to receive a removable partial denture. J Prosthet Dent 1999;82:536-49. 2. Alfonso C, Toothaker RW, Wright RF, White GS. A technique to create appropriate abutment tooth contours for removable partial dentures. J Prosthodont 1999;8:273-5. 3. Kawano F, Ohguri T, Ichikawa T, Matsumoto N. Influence of thermal cycles in water on flexural strength of laboratoryprocessed composite resin. J Oral Rehabil 2001;28:703-7. 4. Takahashi Y, Hisama K, Sato H, Chai J, Shimizu H, Kido H, et al. Probability of failure of highly filled indirect resin-veneered implant-supported restorations: an in vitro study. Int J Prosthodont 2002;15:179-82. 5. Davenport JC, Hawamdeh K, Harrington E, Wilson HJ. Clasp retention and composites: an abrasion study. J Dent 1990;18:198202. 6. Tietge JD, Dixon DL, Breeding LC, Leary JM, Aquilino SA. In vitro investigation of the wear of resin composite materials and cast direct retainers during removable partial denture placement and removal. Int J Prosthodont 1992;5:145-53. 7. Chow TW, Chung RW, Chu FC, Newsome PR. Tooth preparations designed for posterior resin-bonded fixed partial B 1 A, Definitive cast of preparations. B, Intaglio surface of highly filled composite resin partial coverage restoration. A

Systematic Clinical Evaluation and Correction Procedures for Support of Removable Partial Dentures

Support, retention, and bracing are the three main functions of a direct retainer in removable partial dentures (RPDs). RPDs must have sufficient supporting ability for proper occlusal rehabilitation. Support ability depends on the fit, size, shape, and location of the occlusal rest. Support cannot be adjusted chairside in most cases. The purpose of this article is to present systematic evaluation criteria for support in an RPD and to describe methods for adjusting cast clasps with improper support. Appropriate design of RPDs and preparation of abutments are also described.