The primary issue in managing edentulous patients is the severely resorbed mandibular ridge, particularly in older individuals with diminished adaptive capacities. This compromised situation leads to the fabrication of inadequate dentures that lack retention and stability, potentially causing psychosocial issues.

To determine the difference in retentive capacity between three attachment systems in implant-retained overdentures.

Three edentulous mandibular models were fabricated using heat-cured polymethacrylate resin, with two implant replicas placed in the intra-foraminal region of each model. 30 acrylic resin mandibular overdentures were fabricated with provisions for three different overdenture attachment systems: A prefabricated ball/O-ring attachment, a locator attachment system, and an equator attachment system. Each model was subjected to 15000 pulls using a universal testing machine to remove the overdenture from the acrylic model and the force data were recorded.

The ball/O-ring attachment system demonstrated superior retentive capacity for 15 years, while the locator and equator attachment systems maintained excellent retentive capacity for 5 years.

The ball/O-ring attachment system outperformed better than the other two attachment systems regarding retentive capacity. The locator and equator attachment systems presented sufficient retentive abilities until 15000 cycles. After 7500 cycles, significant differences in retentive force between the systems evolved.

• Dentures
• Overdenture attachment systems
• Equator
• Dislodging cycles
• Retentive capacity

• ball attachment system
• cylindrical attachment system
• implant‐retained mandibular overdenture
• initial retention force

• Denture, Overlay
• Denture Retention/instrumentation
• Dental Prosthesis, Implant-Supported
• Humans
• In Vitro Techniques
• Dental Stress Analysis
• Mandible
• Materials Testing
• Denture Design

• implant angulation
• overdenture attachment systems
• patrice retention

• Denture, Overlay
• Denture Retention/instrumentation
• Dental Prosthesis, Implant-Supported
• Humans
• Dental Abutments
• In Vitro Techniques
• Dental Stress Analysis
• Dental Implants
• Dental Implant-Abutment Design
• Materials Testing

• Attachment systems
• Cyclic dislodging
• Dislodgment time
• Implant overdentures
• In-vitro study
• Retention

• Ball and cylindrical attachment systems
• Implant-retained mandibular overdenture
• Retention force
• Wear

• Humans
• Denture, Overlay
• Denture Retention/methods
• X-Ray Microtomography
• Mandible
• Dental Stress Analysis
• Dental Implants

• Angle deviation
• CBCT
• Dental implants
• Implantology
• Parallel pin

• Humans
• Dental Implants
• Dental Implantation, Endosseous/methods
• Polyurethanes
• Surgery, Computer-Assisted/methods
• Jaw, Edentulous
• Imaging, Three-Dimensional
• Computer-Aided Design
• Cone-Beam Computed Tomography

• Attachment wear
• Implant-assisted overdenture
• Locator R-Tx attachment
• Titach attachment
• Titanium-to-nylon interface
• Titanium-to-titanium interface

• Humans
• Denture, Overlay
• Titanium
• Nylons
• Dental Prosthesis, Implant-Supported
• Denture Retention
• Dental Materials
• Mandible
• Dental Implants
• Dental Stress Analysis

• Alexandria University

• Dental Implants
• Denture Retention
• Mastication
• Polymethyl Methacrylate
• Dental Prosthesis, Implant-Supported
• Denture, Overlay
• Dental Stress Analysis
• Dental Abutments

• dental prosthesis retention
• masticatory force
• mini dental implants
• overdenture

Attachment systems (AS) enhance retention and stability by anchoring the overdentures to implants. Since 2002, the McGill consensus statement recommends the 2-implant-retained overdentures as the standard choice for edentulous mandible (2-IRMO). Considering the large number of AS available, it remains difficult for a practitioner to make a reasoned choice. A systematic review was conducted in PubMed/Medline and carried out independently by three authors, on retention, wear, and maintenance of AS used clinically or in vitro specifically for 1- or 2-IRMO. The 45 selected studies include 14 clinical and 31 in vitro studies. The risk of bias was evaluated according to the revised Cochrane risk of bias tool for randomized trials (RoB 2). The initial retention force of the cylindrical system is higher than the ball system. The retention loss, related to the wear of the retention device, is responsible for the most common need of maintenance, requiring activation or replacement. Plastic retention devices wear out faster and more significantly than metal ones, implying a worse time behavior of cylindrical systems, but their maintenance rate is similar. Neither system appears categorically superior. Cylindrical systems provide higher initial retention than ball ones; this advantage reduces over time with wear without affecting their need for maintenance.

• ball and cylindrical attachment systems
• implant-retained overdenture
• maintenance
• retention force
• wear

A new application of a polyetheretherketone (PEEK) post-core restoration combined with polyvinylsiloxane (PVS) attachments was proposed and substantiated. This study aimed to evaluate retentive characteristics of the PEEK post-core restoration with PVS attachment systems. Specimens with PVS attachments were fabricated to evaluate retention force during 10,000 cyclic dislodgements. Additionally, the retention forces of PVS attachments with three different values of Shore hardness were further measured before and after aging treatments. The results of cyclic dislodgement test indicated a strong negative linear relationship between the cyclic times and retention force (p < 0.0001, r = −0.957). Furthermore, the retention forces of the PVS were significantly improved with Shore hardness increased, which was also affected by the aging treatment (F (2, 138) = 10.95, p < 0.0001). Therefore, the PEEK post-core restoration with PVS attachments exhibited the favorable retention force, which could be a promising alternative for dental prostheses.

• attachment system
• dental materials
• overdenture
• polyetheretherketone
• polymer-based material
• polyvinylsiloxane
• post-core restoration
• prosthodontics

• Attachment system
• Implant
• Implant-overdenture
• PEEK
• PEKK
• Wear

• Locator
• Overdentures
• tap water

The purpose of this study was to evaluate the change in the retentive forces of four different titanium-based implant attachment systems during the simulation of insert–removal cycles in an artificial oral environment. Five types of titanium-based dental implant attachment systems (Locator, Kerator, O-ring, EZ-Lock, and Magnetic) were studied (n = 10). The specimens underwent insert–removal cycles in artificial saliva, and the retentive force was measured following 0, 750, 1500, and 2250 cycles. Significant retention loss was observed in all attachment systems, except the magnetic attachments, upon completion of 2250 insertion and removal cycles, compared to the initial retentive force (p < 0.05). A comparison of the initial retentive forces revealed the highest value for Locator, followed by the Kerator, O-ring, EZ-Lock, and Magnetic attachments. Furthermore, Kerator demonstrated the highest retentive loss, followed by Locator, O-ring, EZ-Lock, and Magnetic attachments after 2250 cycles (p < 0.05). In addition, the Locator and Kerator systems revealed significant decrease in retentive forces at all measurement points (p < 0.05). The retention force according to the insert–removal cycles were significantly different according to the types of dental implant attachment systems.

• dental implants
• denture precision attachment
• dentures
• prosthesis retention
• reference standard
• titanium

This retrospective cross‐sectional study aimed to evaluate quantitatively the oral microbiome in the tri‐lobe central cavity of Locator Legacy attachment and verify whether it harbors a different, potentially more pathogenic, bacterial spectrum than the adjacent edentulous ridge.

Edentulous patients rehabilitated with implant overdentures using Locator Legacy attachments were recruited for this study. The clinical examination comprised probing depths, mobility, peri‐implant, and periodontal health along with intraoral swabs for microbiological evaluation, polymerase chain reaction (PCR) testing, and candida culture. The swabs were collected from the trilobed cavity of the attachment and the adjacent edentulous ridge. PCR was performed to detect six specific bacteria, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia, Treponema denticola, Prevotella intermedia, and Parvimonas micra. Statistical analyses were performed using McNemar's test and Wilcoxon's rank sum test with the significance set to p < .05.

A total of 50 participants with a mean age of 71.5 ± 9.6 years participated in the study. No significant differences in the microbiome were found between samples from the ridge and the attachment. No significantly different numbers in the candida cultures were identified, and the presence of a removable prostheses did not demonstrate a significant association with the prevalence of candida.

Within the limits of this study and the investigated bacterial species, the trilobed cavity of the attachment does not seem to increase the bacterial load.

• cross‐sectional study
• implant overdentures
• locator legacy attachments
• microbiological evaluation
• removable prosthodontics

The objective of this investigation was to analyze the mechanical features of two different prosthetic retention devices. By applying engineering tools like the finite element method (FEM) and Von Mises analyses, we investigated how dental implant devices hold out against masticatory strength during chewing cycles. Two common dental implant overdenture retention systems were analyzed and then compared with a universal—common dental abutment. The Equator^® attachment system and the Locator^® arrangement were processed using the FEM Ansys^® Workbench. The elastic features of the materials used in the study were taken from recent literature. Results revealed different responses for both the devices, and both systems guaranteed a perfect fit over the axial load. However, the different design and shape involves the customized use of each device for a typical clinical condition of applying overdenture systems over dental implants. The data from this virtual model showed different features and mechanical behaviors of the overdenture prosthodontics attachments. A three-dimensional system involved the fixture, abutment, and passant screws of three different dental implants that were created and analyzed. Clinicians should find the best prosthetic balance to better distribute the stress over the component, and to guarantee the patients clinical long-term results.

• FEM
• implant abutment connections
• overdenture attachments
• stress distribution

• LOCATOR® attachments
• attachment wear
• implant overdentures
• mechanical complications
• overdenture
• removable dental prostheses

It is necessary to know the in vitro behavior of different attachment systems to be used clinically. The evolution of retention capacity over 10 years (14,600 insertion/de-insertion cycles) was determined in vitro, evaluating two overdenture attachment systems (Locator® and OT Equator®).

The study used an implant replica compatible with the abutments of both systems. 10 Locator® and 10 OT Equator® attachments were screwed to the abutments. Nylon inserts were attached and tested, subjecting them to 14,600 insertion and de-insertion cycles (representing 10 years functional life) in axial direction. The universal test machine crosshead speed was 50 mm/min with a de-insertion range of 2 mm.

The initial retention of Locator® was 17.02 N and of Equator® 16.36 N. After 14,600 cycles, Locator® suffered a mean loss of retention of 50.89%, while Equator® lost 69.28%. Both systems showed retention increases up to the first 1,000 cycles, which decreased thereafter up to 14.600 cycles. Statistically significant differences between the systems were found after 7,500 cycles.

Both systems presented acceptable retention capacities after 14,600 cycles. Significant differences in retention force between the systems evolved after 7,500 cycles (5 years in vitro use). These results should be treated with caution and should be verified clinically.

Key words:Denture, mandibular prosthesis implantation, attachment, dental implant-abutment connection, denture retention.

The two implant-supported overdentures have overcome the retention and stability-related problems of conventional mandibular denture. Stud attachments are widely available, less expensive, and easy to use.

To determine fatigue resistance of two different stud attachments with two denture base materials – autopolymerizing and heat cure acrylic resin till 4320 cycles simulating 03 years of service.

Stud implant overdenture attachments, i.e., ball and socket and Dalla Bona attachments were tightened over the implants in two different mandibular edentulous base models. The housings were incorporated with both direct (chairside) and indirect (laboratory) technique into conventional mandibular dentures. These overdentures were subjected to continuous removal and insertion on Universal Testing Machine till 4320 cycles simulating 3 years of service assuming that patient takes out denture, 4 times in a day. The fatigue resistance was calculated for 0, 1440 (1 year), 2800 (2 years), and 4320 (3 years) cycles. Unpaired and paired t-tests were applied to find the level of significance.

Ball and socket attachments housed with heat cure acrylic resin (indirect technique) had the highest values of fatigue resistance at all cycles. Following were Dalla Bona attachments with autopolymerizing acrylic resin (direct technique), ball and socket attachments with autopolymerizing acrylic resin (direct technique), and Dalla Bona attachments with heat cure acrylic resin (indirect technique) as per statistical analysis.

Two implant-supported mandibular overdenture with ball and socket attachments incorporated by indirect technique showed higher values in terms of retention and absence of disengagement/fracture of components.

• Ball and socket attachments
• Dalla Bona attachments
• fatigue resistance
• implant-supported overdenture
• overdenture stud attachments

• Dental implants
• Dental prosthesis retention Denture overlay.

The aim of this study is to evaluate and compare the stress distribution in Locator attachments in mandibular two-implant overdentures according to implant locations and different loading conditions.

Four three-dimensional finite element models were created, simulating two osseointegrated implants in the mandible to support two Locator attachments and an overdenture. The models simulated an overdenture with implants located in the position of the level of lateral incisors, canines, second premolars, and crossed implant. A 150 N vertical unilateral and bilateral load was applied at different locations and 40 N was also applied when combined with anterior load at the midline. Data for von Mises stresses in the abutment (matrix) of the attachment and the plastic insert (patrix) of the attachment were produced numerically, color-coded, and compared between the models for attachments and loading conditions.

Regardless of the load, the greatest stress values were recorded in the overdenture attachments with implants at lateral incisor locations. In all models and load conditions, the attachment abutment (matrix) withstood a much greater stress than the insert plastic (patrix). Regardless of the model, when a unilateral load was applied, the load side Locator attachments recorded a much higher stress compared to the contralateral side. However, with load bilateral posterior alone or combined at midline load, the stress distribution was more symmetrical. The stress is distributed primarily in the occlusal and lateral surface of the insert plastic patrix and threadless area of the abutment (matrix).

The overdenture model with lateral incisor level implants is the worst design in terms of biomechanical environment for the attachment components. The bilateral load in general favors a more uniform stress distribution in both attachments compared to a much greater stress registered with unilateral load in the load side attachments. Regardless of the implant positions and the occlusal load application site, the stress transferred to the insert plastic is much lower than that registered in the abutment.

• Finite element analysis
• Locator attachment
• Occlusal load
• Overdenture
• Stress

• Cyclic load
• Locator attachment
• in vitro study
• overdenture
• retention
• simulated mastication

Implant-supported removable dental prostheses may be supported by a variety of splinted (bar and clip) attachment systems or nonsplinted abutment-based attachments (ball, magnets, and resilient stud attachments such as locators [Zest Anchors], ERA [Sterngold], and nonresilient-stud attachments such as ANKYLOS SynCone [Dentsply Implants]). Nonsplinted attachments are preferred as they are more economical, less technique sensitive, easier to clean, repair, and maintain than splinted (bar and clip) attachment systems, but they work favorably only when implants in the arch are placed parallel to each other. Often implants in the anterior maxilla have to be placed with a labial inclination (due to the proclination of the premaxilla), resulting in lack of parallelism between the anterior and posterior implants, making it challenging to fabricate a removable dental prostheses supported by nonsplinted attachments, and necessitating the use of angled abutments. Recently, a novel implant design with a 12° restorative platform angulation has been introduced by Southern Implants (Co-axis, Keystone Dental, Inc., Burlington, MA, USA). These new angulated implants aid in minimizing the divergence between the anterior and posterior maxillary implants without using angled abutments. The purpose of this article was to report a case utilizing the novel angulated implants (Co-axis, Keystone Dental, Inc., Burlington, MA, USA) in the premaxilla for fabrication of maxillary removable dental prostheses supported and retained by nonsplinted attachments.

• Angle correction
• Co-axis
• angled abutment
• divergent
• implants
• novel design

• Aged
• Dental Implants/psychology
• Dental Prosthesis, Implant-Supported/psychology
• Denture Design
• Denture Rebasing
• Denture Retention/psychology
• Denture, Complete, Lower/psychology
• Denture, Overlay/psychology
• Female
• Follow-Up Studies
• Humans
• Jaw, Edentulous/psychology
• Male
• Mandible
• Oral Health
• Patient Satisfaction
• Prospective Studies
• Quality of Life
• Spain
• Surveys and Questionnaires
• Survival Analysis
• Treatment Outcome

• Cyclic loading
• Research apparatus
• Retention
• Telescopic crown

• Crowns
• Dental Prosthesis Design/instrumentation
• Dental Prosthesis Design/methods
• Humans

• Computer-Aided Design
• Dental Impression Materials/therapeutic use
• Dental Prosthesis, Implant-Supported/methods
• Denture Design/methods
• Denture, Partial, Removable
• Gutta-Percha/therapeutic use
• Humans
• Surgery, Computer-Assisted/methods

The aim of the present study was to evaluate, by means of strain gauge analysis, the effect of different implant angulations on strains around two implants retaining mandibular overdenture with Locator attachments.

Four duplicate mandibular acrylic models were constructed. Two implants were inserted in the canine regions using the following degrees of distal inclinations: group I (control); 0°, group II; 10°, group III; 20°, and group IV; 30°. Locator pink attachments were used to connect the overdenture to the implants and Locator red (designed for severely angled implants) was used for group IV (group IV_red). For each group, two linear strain gauges were attached at the mesial and distal surfaces of the acrylic resin around each implant. Peri-implant strain was measured on loading and non-loading sides during bilateral and unilateral loading.

For all groups, the mesial surfaces of the implants at loading and non-loading sides experienced compressive (negative) strains, while the distal implant surfaces showed tensile (positive) strains. Group IV showed the highest strain, followed by group III, group II. Both group I and group IV_red showed the lowest strain. The strain gauges at the mesial surface of the loading side recorded the highest strain, and the distal surface at non-loading side showed the lowest strain. Unilateral loading recorded significantly higher strain than bilateral loading.

Peri-implant strains around two implants used to retain mandibular overdentures with Locator attachments increase as distal implant inclination increases, except when red nylon inserts were used.

• Inclined implants
• Locator
• Overdentures
• Strain

This in vitro study investigated and compared the durability and retention of three types of attachments.

Three commercially available attachments were investigated: Clix®, Dalbo-Plus® and Locator®. In total, 72 samples of these attachments were placed in the acrylic resin forms and subjected to mechanical testing (5400 cycles of insertion and removal) over the respective ball or Locator abutments immersed in artificial saliva at pH 7 and 37℃. The abutments were placed at angulations of 0°, 10° and 20°. The retention force was recorded at the beginning and after 540, 1080, 2160, 3240, 4320 and 5400 insertion-removal cycles.

The results revealed that there were significant differences in the average values of the insertion/removal force due to angulation (F _(2.48) = 343619, P<.05) and the type of attachment (F _(7.48) = 23.220, P<.05).

Greater angulation of the abutments was found to influence the retention capacity of the attachments, and the fatigue test simulating 5 years of denture insertion and removal did not produce wear in the metal abutments.

• Attachments
• Dental implants
• Edentulous patients
• Overdentures

• Balanced occlusion
• Canine guidance
• Electromyography
• Implant-retained overdentures
• Muscle activity

• LOCATOR® attachments
• artificial saliva
• dislodging cycles
• in vitro testing
• overdentures
• retentive force

New attachment systems are released for mandibular two-implant overdentures often without evidence-based support. Biomaterial aspects are now the parameters considered when choosing the appropriate attachment. Studies regarding their properties remain scarce.

The purpose of this review was to help the clinician in selrcting the most adapted stud attachments according evidence-based dentistry.

An electronic search was conducted using specific databases (PubMed, Medline, and Elsevier libraries). Peer-reviewed articles published in English up to July 2014 were identified. Emphasis was given on the biomaterial aspects and technical complications. No hand search was added.

The electronic search generated 115 full-text papers, of which 84 papers were included in the review. The majority were clinical and in vitro studies. Some review articles were also considered. Papers reported survival and failures of overdenture connection systems. Emphasis was laid on attachment deformation.

Implant overdentures long-term follow-up studies may provide useful guidelines for the clinician in selecting the type of attachment system and overdenture design. Locator attachments are more and more used, with lesser complications reported.

• Biomaterial
• overdenture
• stud attachments

• Implant angulations
• Implant-retained overdentures
• Retentive attachments

Objectives: The main aim of this review article is to discuss implant-supported overdentures (ISOs) as treatment in edentulous patients. Besides, we will try to discuss among the different treatment options in such patients and to analyze their validity when ISOs are compared with other clinical modalities. At the same time, we will try to suggest clinical guidelines supported by current clinical studies. Material and methods: We performed a Medline search and review of pertinent articles on the mentioned subject from 1986 to 2011. As a searching strategy, we used the following words: implant-supported overdentures, attachment systems, Locator attachment, cantilever, fixed prosthesis. Results and conclusions: Implant-supported overdentures constitute an accurate and predictable treatment option and achieve a higher patients’ satisfaction. This type of treatment constitutes a cheaper treatment than fixed prostheses and in some patients, with loss of lip support or with an interoclusal space larger than 15 mm, the choice of implant-supported overdentures seems to prevent future aesthetic or phonetic problems.

Key words:Overdentures, implant occlusion, implant rehabilitation, total edentulous rehabilitation, fixed prosthesis.