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a. Equipoise Clasp: Occlusal view of the clasps placed on the 13 and the 24 as part of a Kennedy class IV RPD.
Source publication
Removable partial dentures (RPD) are an effective and affordable treatment option for partial edentulism. If the main reason for seeking treatment is the need for improved aesthetics, treatment should be geared towards achieving this goal. This article is the result of a literature study on aesthetic clasp design for the conventional RPD. In this c...
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This article reports the case of a 55-year-old female patient who presented with unsatisfactory temporary crowns in the right mandibular premolars and molars, and a premolar-to-molar fixed partial denture in the left side. The clinical and radiographic examinations revealed a fracture of the left first premolar that was a retainer of the fixed part...
Citations
... An ideally retained RPD should hamper the gingival-occlusal movement without showing great resistance to its removal. 11,12 The calibrated gauges are usually manufactured in three different undercuts, i.e., 0.25 mm, 0.50 mm, and 0.75 mm, 13,14 and used according to the framework material. The 0.25 mm undercut is the gold standard for the cobalt-chromium (CoCr) alloy. ...
Aim:
The aim of this study was to evaluate the stress distribution of a planned removable partial denture (RPD) using new proposals for calibrated gauges of 0.3 mm and 0.35 mm undercuts through the three-dimensional (3D) finite element methodology, and compare them with 0.25 mm and 0.5 mm gauges that are already existing in clinical practice.
Materials and methods:
Kennedy class-I edentulous 3D models and their respective RPDs (InVesalius software; Rhinoceros and SolidWorks CAD) were created and exported to the finite element program HyperMesh 2019 for mesh configuration. In the following steps, axial loading (0º) of 40 N per point was performed, with 3 points on the molars and 2 points on the premolars, totaling 280 N unilaterally. The model was processed by the OptiStruct 2019 software and imported into the HyperView 2019 software to obtain the stress maps (MPa).
Results:
The use of 0.30 and 0.35 mm calibrated gauges presented tensions similar to those with the 0.25 mm gauge (gold standard) and caused no significant damage to biological structures. The use of a 0.5 mm undercut caused greater traction force in the periodontal ligament of the abutments.
Conclusions:
The 0.35 mm undercut seems promising as it presented more favorable results in this simulation, on the other hand, a 0.5 mm undercut is greater than that necessary for retainers made of CoCr.
Clinical significance:
This study aims to measure a new undercut gauge (0.35 mm) to increase the retention area in abutment teeth of removable partial dentures.
... With ever rising esthetic demands, research activities have focused on tackling the main drawback of alloy clasps: their metallic color. To eliminate the esthetically disadvantageous retentive arm, lingual retentions or rotational paths were investigated as alternatives to conventional clasp designs [14,15]. Others aimed to modify the alloy claps itself by etching and veneering said materials with tooth-colored resin composite [16]. ...
Objectives
To investigate the retention force of polyetheretherketone (PEEK) removable dental prosthesis clasps in comparison with a cobalt-chrome-molybdenum control group after storage in artificial saliva.
Materials and Methods
Clasps were milled (Dentokeep (PEEKmilled1), NT digital implant technology; breCAM BioHPP Blank (PEEKmilled2), bredent), pressed (BioHPP Granulat for 2 press (PEEKpressed), bredent), or cast (remanium GM 800+ (cobalt-chrome-molybdenum), Dentaurum); N = 60, n = 15/subgroup. Retention force was examined 50 times/specimen in a pull-off test using the universal testing machine (Zwick 1445), where pull-off force was applied with a crosshead speed of 5 mm/minute until the maximum force dropped by 10%, at different aging levels: (1) initial, after storage in artificial saliva for (2) 90 and (3) 180 days. Statistical analysis was performed using one-way ANOVA followed by post hoc Scheffé-test and mixed models (p < 0.05).
Results
Cobalt-chrome-molybdenum presented the highest retention force. No differences were observed between polyetheretherketone materials. Cobalt-chrome-molybdenum showed a significant decrease of its values after artificial aging, while polyetheretherketone materials presented similar results over the course of aging. Regarding a repetitive insertion and removal, even though PEEKmilled2 and cobalt-chrome-molybdenum showed an initial increase, ultimately, a decrease in retention force was observed for all tested groups.
Conclusions
Although the control group showed significantly higher results, the retention force of polyetheretherketone materials indicate a potential clinical application. Neither the manufacturing process nor artificial aging showed an impact on the retention force of polyetheretherketone clasps.
Clinical relevance
Mechanical properties of novel removable dental prosthesis clasp materials devised to meet the growing esthetic demands of patients need to be investigated to ensure a successful long-term clinical application.
... (126) Accordingly, retention can be improved by optimizing the shape, undercut depth, and fabrication process. (135,136) The most important features of partial denture framework design are the retaining elements. It was found that lack of stability of removable partial dentures in the maxilla is 7 times more common than lack of retention, while in the mandible the lack of stability is 1.8 times the lack of retention. ...
Purpose: The purpose of this study was the evaluation of retention and fitness of Mandibular Kennedy class I modified polyether-ether-ketone removable partial dentures frameworks fabricated with various techniques.
Materials and Methods: The study was conducted as a within-subject comparison. Six patients were selected to participate in this study. All the selected cases had maxillary completely edentulous arch opposed by mandibular distal extension ridges posterior to canine teeth. For each patient two modified polyether-ether-ketone removable partial dentures frameworks were fabricated with various techniques in a crossover design: Group I: CAD/CAM fabricated framework, Group II: injection molding fabricated frameworks. For each framework; ; fitness evaluation were done by measuring the gap between the framework and oral tissues by using auto mix light body poly vinyl- siloxane impression material. In addition, evaluation of Retention force of both removable partial dentures frameworks was measured by using a digital forcemeter.
Results: - There was a statistically significant difference in retention values between both groups, where injection molding fabricated frameworks verified higher mean retention values than those frameworks fabricated by CAD/CAM. Furthermore, the mean overall values of gap distance in frameworks fabricated by CAD/CAM were significantly higher than the mean values of Gap distance in frameworks fabricated by injection molding technique.
Conclusion: Within the limitations of this short-term clinical study it was concluded that: Retention and fitness of both fabrication techniques of the modified polyether-ether-ketone removable partial dentures frameworks were clinically accepted by the participants. Regarding Retention and
Abstract
viii
Fitness, modified polyether-ether-ketone removable partial dentures frameworks fabricated by injection molding technique recorded higher values compared to CAD/CAM frameworks
... The most frequently used mechanical retainer continues to be the extracoronally located clasp (141) . The flexible clasp tip engages the undercut of the abutment to provide retention (142) . The components of any clasp assembly must satisfy six biomechanical requirements: retention, stability, support, reciprocation, encirclement and passivity (143,144) . ...
... The components of any clasp assembly must satisfy six biomechanical requirements: retention, stability, support, reciprocation, encirclement and passivity (143,144) . In addition, the clasp assembly must ideally not affect aesthetics adversely (142) . ...
... Clasps can be classified into infrabulge and suprabulge clasps (4,142) . ...
Objective: to compare between retention of clasps made from PEEK and Co-Cr RPDs constructed by using CAD/CAM technology.
Materials and methods: Ten patients were selected for this study with mandibular class III Kennedy classification with modification-1. The patients were randomly divided into two equal groups according to the material used for constructing the RPDs: Group A delivered CAD/CAM polyetheretherketone (PEEK) RPDs and Group B delivered CAD/CAM designed and 3D printed resin pattern frameworks casted into Co-Cr RPDs. For each group, the force of retention was measured by digital forcemeter immediately, 3 months and six months after denture insertion. The retention loss was evaluated and compared between the two groups within all intervals of the study.
Results: -The retention forces in group B (Co-Cr RPDs) were higher than that of group A (PEEK RPDs) engaging the same undercuts. Although the insignificant difference at T0, it was significant at T3 and T6 where in group A: T0=12.96N, T3=10.86 and T6=8.94N and in group B: T0=13.20, T3=12.6N and T6=12.11N.
- Both groups showing statically significant decrease in the retention force with time except between T3 and T6 in group B which was insignificant decrease.
-The comparison between the loss of retention in the two groups, showed that group A was associated with significant higher retention loss than group B of along the study where in group A: T0-T6=4.02N and in group B: T0-T6=1.09N .
Conclusions: Within the limitation of this study, it can be concluded that:(1) Although the difference in the retention force between PEEK and Co-Cr clasps, this retention force is within the adequate required limits for retaining RPDs. (2) Co-Cr claps can be considered better than PEEK clasps engaging the same undercuts in regard to the maintaining of the retention force as long as possible.
Keywords: PEEK, CAD/CAM RPD, Retention force of RPD, loss of retention of RPD.
... [2] The clinician are responsible for RPD design and the aesthetic condition have great importance to the patient, besides that visible retentive structures causes RPD rejection. [3,4] Ideally, RPD should have adequate biomechanical properties, satisfactory retention, stability and stress absorption that depends on professional training with skills and the experience of the laboratory technician. [5] Besides that, one of the most critical requirements is the balance between forces distribution, flexibility, retention and reciprocity. ...
Objective: This study aimed to evaluate and compare the retention force of individual clasps made from polyamide, acetate resin and cobalt-chrome for removable partial dentures. Material and methods: Three groups of clasps were fabricated: Cr-Co - 10 conventional chrome-cobalt metal clasps; Ac - 10 clasps with reciprocal arms and occlusal rests in chrome-cobalt and retentive arms in acetate resin; and Poly - 10 clasps with reciprocal arms and occlusal rests in chrome-cobalt and retentive arms in polyamide resin. Through the tensile test, in a universal testing machine, the initial retention force of the specimens was obtained and then clasps were cycled 7200 times, immersed in artificial saliva (60 months of simulated clinical use). After cycling, tensile test was performed. Results: All groups presented a retention decrease after the cycling. Ac presented a large reduction in retentive force (61.43%), followed by Cr-Co (26.5%) and Poly (12.09%). Conclusions: Aesthetic clasps of polyamide can be used in clinical cases where the anterior supporting teeth will not be essential for good retention of the removable partial denture because this clasp showed to be more resistant than the acetate resin.
... These days, there is an expanding of the accentuation on aesthetic, dental specialist have been worried about giving aesthetics and functional RPDs to their patients and this made the mission more troublesome in view of the objective. Now is accomplishing ideal aesthetic of the denture, while looking after retentive, stable, and well-being of supporting tooth and supporting tissue.(37) ...
Abstract
Purpose: CAD / CAM performed this in vitro scanning electron microscope study to evaluate the influence of various polishing protocols on polyether-ether ketone (PEEK) removable partial frameworks surface topography that fabricated.
Materials and Methods: 3 modified PEEK removable partial denture frameworks fabricated by CAD/CAM techniques were examined by scanning electron micro-scope (SEM), after polishing by different polishing protocols. These modified PEEK frameworks were fitted over an epoxy resin model of maxillary class I Kennedy with remaining natural teeth extended from first premolar on one side to first premolar on the other side. According to polishing protocols the modified PEEK frameworks were divided into three groups: Group I: modified PEEK frameworks without polishing, Group II: modified PEEK frameworks polished with Abraso-Starglanz polishing system and, Group III: modified PEEK frameworks polished with Acrypol polishing system. Surface topography was examined before and, after different polishing protocols and after 1440 insertion/ removing cycles. Statistical comparison between the different groups was tested.
Results: It was noted that (group I) showed the highest surface roughness while the lowest surface roughness and highly smooth surface was showed in (group II). By using Student’s t-test for comparing between groups, group II showed significance decrease in surface roughness compared to that in (group I) and group III where (p<0.001).
Conclusions: Considering this study limitations, it was concluded that: Polishing PEEK framework with Abraso-starglaz paste was most effective and promising in producing highly smooth surface than Acrypol polishing paste. For the laboratory-based protocols, both Abraso-starglaz and, Acrypol polishing pastes produce a significantly smoothness peek surface more than non-polished peek
... Additionally, they flex in all directions and, as a result, they can engage larger undercuts and may, therefore, be less visible. 8,9 Moreover, guide planes were used to ensure precise placement of the prosthesis, more predictable retention, and greater degree of stability. They also aid in the retention by resisting vertical displacement of the obturator and disengaging the retentive clasp arms. ...
... Removable partial dentures (RPDs) are an effective and affordable treatment modality to restore function and aesthetics. Several types of polymers and metal alloys could be used in the construction of RPDs (1). The most commonly used alloys for RPDs are cobalt-chromium (Co-Cr), gold and titanium alloys, although they are not aesthetically pleasing. ...
... The components of any clasp assembly must fulfil at least six biomechanical requirements, namely retention, stability, support, reciprocation, encirclement and passivity. In addition, the clasp assembly must ideally not affect aesthetics adversely (1). For this purpose, researchers have been investigating alternative materials in order to overcome the unaesthetic appearance of alloy clasps especially when they are placed on the anterior teeth. ...
Objective: The use of metal clasps especially in anterior region may cause aesthetic problems. Polyamide resin has been suggested as an alternative aesthetic denture clasp material. This study compared the retentive force and deformation of cobalt-chromium and polyamide clasps after 36 months of simulated clinical use.
Materials and Methods: The retentive force for clasp removal was measured in distilled water using a custom-made apparatus with intervals corresponding to 0, 6, 12, 18, 24, 30 and 36 months of simulated clinical use. The distance (mm) between the retentive and reciprocal clasp tips was measured using a microscope before and after the insertion-removal procedures.
Results: Significant difference was observed in distance between clasp tips for metal clasps between baseline and 36 months for molars and premolars (p
... The clasps are also classified according to material used to cast chromium clasps, wrought wire clasps, gold-alloy clasps, platinum-gold-palladium clasps and technopolymer clasps (thermoplastic). The infrabulge clasp has been thought to be more retentive than the suprabulge clasp (12) . ...
... Aunque el factor estético no sea un imperativo o constituya un estándar en prótesis parcial removible (11) , para muchos pacientes la exposición de algún componente del complejo retentivo, en general brazos retentivos vestibulares, no resulta tolerable (11) . Más aún, para Mc Garry (5) , si existe una preocupación o desafío de orden estético de parte del paciente, entonces el grado de complejidad en el IDP se incrementa a un nivel inmediatamente superior, cuando se trata de Clases I y II de ese Índice. ...
... Aunque el factor estético no sea un imperativo o constituya un estándar en prótesis parcial removible (11) , para muchos pacientes la exposición de algún componente del complejo retentivo, en general brazos retentivos vestibulares, no resulta tolerable (11) . Más aún, para Mc Garry (5) , si existe una preocupación o desafío de orden estético de parte del paciente, entonces el grado de complejidad en el IDP se incrementa a un nivel inmediatamente superior, cuando se trata de Clases I y II de ese Índice. ...
... Es así como con cierta frecuencia vemos en la literatura pertinente, incluso antes de la propuesta del MGR de Mc Cartney de 1981 (6) , la presentación de complejos retentivos que pretenden superar esta falencia, incluso con diseños para incisivos laterales que deban "soportar" el emplazamiento de ese componente de la prótesis removible (11,12) . ...
The emergence of osseointegrated implants and their further validation, at the beginning of the 80’s, contributed undoubtedly to oral rehabilitation as a very useful resource. Unfortunately, mainly because of the economic costs involved and despite an encouraging initial augury, they have not become in a specific therapeutic alternative for the vast majority of edentulous patients. Partial edentulism of maxillae, Kennedy’s class I, & II, with all or a few teeth remaining at the sextant 2, mostly class III PDI, substantially compromised denture-supporting anatomy, generate a prosthetic challenge to overcome regarding retention and aesthetic satisfaction of these patients. In this report, we display two of them, which we believe have been successfully managed in order to fulfill both variables, by means of “conventional” removable metallic prostheses combining MGR’s clasps and frictional retentive facets.
