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 Table of Contents  
Year : 2020  |  Volume : 12  |  Issue : 5  |  Page : 420-426

A comparison of the retentive force of ball and socket attachment versus magnet attachment in mandibular overdentures: A randomized control trial

1 Department of Prosthodontics, Faculty of Dentistry, University of Beni-Suef, Beni-Suef, Egypt
2 Department of Prosthodontics, Faculty of Dentistry, University of Ahram Candian, Cairo, Egypt
3 Department of Prosthodontics, Faculty of Dentistry, University of Cairo, Cairo, Egypt; Department of Prosthodontics, Faculty of Dentistry, Future University, Cairo, Egypt

Date of Submission20-Jan-2020
Date of Decision12-Apr-2020
Date of Acceptance13-Apr-2020
Date of Web Publication21-Oct-2020

Correspondence Address:
Dr. Mohamed Y Sharaf
Department of Prosthodontics, Faculty of Dentistry, University of Beni-Suef, Beni-Suef
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jioh.jioh_20_20

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Aim: To compare the retention and patient satisfaction of implant-supported mandibular overdentures with ball and socket attachment versus magnet attachment. Materials and Methods: Twenty-four participants (10 males and 14 females) were divided into two equal groups (n = 12). Both groups received implant-supported mandibular overdentures retained by ball and magnet attachment. Two implants were installed in the canine region bilaterally. Evaluation of retention was made at overdenture insertion, 3, 6, and 12 months. Patient satisfaction evaluation with Oral Health Impact Profile Questionnaire-14 (OHIP-14) was made at overdenture insertion 3, and 12 months subsequently. Results: The ball group showed a statistically significantly higher retention force (P < 0.05) than the magnet group at insertion, 3 and 6 months. The ball group had a statistically significantly lower mean of physical disability and physical pain (P < 0.05) than the magnet group through all follow-up. One-way analysis of variance (ANOVA) test was used to compare between groups as well as to study the changes by time within each group. Conclusion: Both implant-supported mandibular overdenture retained with magnet or ball and socket attachments consider a successful treatment option with superior improvement in the ball and socket group.

Keywords: Attachment, Overdenture, Patient Satisfaction, Quality of Life, Retention

How to cite this article:
Sharaf MY, Bakry E, Abdall MF. A comparison of the retentive force of ball and socket attachment versus magnet attachment in mandibular overdentures: A randomized control trial. J Int Oral Health 2020;12:420-6

How to cite this URL:
Sharaf MY, Bakry E, Abdall MF. A comparison of the retentive force of ball and socket attachment versus magnet attachment in mandibular overdentures: A randomized control trial. J Int Oral Health [serial online] 2020 [cited 2022 Jan 26];12:420-6. Available from:

  Introduction Top

Dental implants have completely changed the world of edentulism; despite the enormous efforts exerted, there are still many controversies regarding the retention of implant attachments, which will affect patient satisfaction and preference. There is insufficient evidence to determine the relative effectiveness of different attachment systems on prosthodontic success, maintenance, patient satisfaction, or patient preference.[1],[2],[3],[4],[5] Implant-retained overdentures offer a line of treatment that improve denture retention, patient’s satisfaction, and patient quality of life.[6],[7],[8] Implant-retained overdentures with different types of attachments represent approximately 60% of installed implants.[9],[10] Mandibular overdentures supported by two implants is a cost-effective, predictable line of treatment that improve retention, stability, and patient satisfaction, so it is considered as the standard treatment for the edentulous mandible.[11] Several types of attachments have been developed that are mainly classified into splinted anchorage systems, such as the bar type and unsplinted anchorage systems, as the unsplinted anchorage attachments have been used in many overdentures cases such as the ball and socket. The ball attachment requires less space within the prostheses, is easier to clean and more economical, as well as less technique sensitive. The ball attachment distributes and reduces the transmitted load to the implant by allowing slight multidirectional movement.[12],[13],[14],[15] However, magnets showed many advantages as low profile, minimal lateral stress transmission to the implants, minimal stress generated in the periimplant bone, and also not interfere with surrounding gingival tissues during overdenture dislodgement; magnets are less prominent, smoother, and comfortable to the patients when the prostheses are absent from the mouth.[16],[17],[18],[19],[20] The attachments used with implants mainly require frequent adjustment and repairs, as well as the attachment components liable to fracture, distortion, and disengagement with gradual loss of retention and stability. These problems are a common cause of patient dissatisfaction.[21],[22],[23] Thus, there are still many controversies regarding the retention of implant attachments that are used in implant-supported overdentures, where the success of an implant-retained overdentures primarily depends on the retentive capacity of attachment as well as better esthetics, which will be reflected toward the patient satisfaction and quality of life for long-term functionality.[3],[4],[5]

The purpose of this clinical trial was to compare the retention and patient satisfaction of implant-supported mandibular overdentures with ball and socket versus with magnet attachment. The research hypothesis was that the ball and socket would provide better retentive force as well as better patient satisfaction.

  Materials and Methods Top

Setting and design

Participants were enrolled from the outpatient clinic, Cairo University, Faculty of dentistry from March 2018 till May 2018 in a parallel randomized control trial for 1 year. The Faculty of Oral and Dental Medicine Research Ethics Committee approved the protocol.

Sampling criteria

Based upon the results of Cune et al.,[24] the study will include a minimum of 12 subjects per group for a total of 24 subjects. Sample size calculation was performed using IBM Statistical Package for the Social Sciences (SPSS) Sample Power Release.

The participants were enrolled according to the following criteria: completely edentulous, Angle’s class I maxillomandibular relationship, and all participants were free from neuromuscular disorders, temporomandibular joint disorders, and systemic diseases that could interfere with implant placement or implant osseointegration with age range from 50 to 70 years. Twenty-four selected participants were randomly divided by the team leader with a sealed envelope technique into two equal groups (n = 12) (seven females and five males in each group). The allocation concealment key was retained by the chairman of the department. The ball group received an implant-supported mandibular overdenture retained by ball attachment. The magnet group received an implant-supported mandibular overdenture retained by magnet attachment where all patients were blind regarding the type of final prosthesis. Fabrication of maxillary and mandibular complete denture as conventional manner with teeth arranged according to the lingualized occlusal concept,[5] then the dentures were evaluated intraorally for extension, retention, stability, esthetics, phonetics, occlusal plane orientation, centric occluding relation, and vertical dimension. Then the participants were instructed for denture and oral hygiene measures. The mandibular denture was duplicated into a radiographic stent using a mixture of acrylic resin and barium sulfate with a ratio of 4:1. The stent was then evaluated intraorally.[25] Cone beam computed tomography (CBCT) images were made with the radiographic stent in place to determine the optimal place for implant placement, then the radiographic stent was converted into a surgical guide by making holes in the proposed implant site.

Surgical procedures

The surgical guide was disinfected by immersing it in a 2% glutaraldehyde solution for 15min. Infiltration anesthesia was given in the proposed implant site. The surgical guide was placed, and an explorer was used to mark the proposed sites for implant placement. A crestal incision was made using a Bard Parker blade no. 15, extending 5-mm mesial and distal to the marked implant site. A full-thickness mucoperiosteal flap was reflected using a sharp mucoperiosteal elevator. In some situations, with a sharp knife-edge ridge or irregular ridge, a low-speed fissure bur and bone file was used for smoothing the ridge and creating a bony plateau. Then, the surgical guide was again placed into the patient’s mouth, and a large round bur was used to mark the implant placement site under copious saline irrigation. The implant osteotomy (diameter 3.6 mm and length 12 mm) was made by sequential drilling. The same procedures were repeated for the other implant, and then parallelism was evaluated between both implants using a paralleling tool. The implant was installed in the osteotomy site and rotated gradually till flushing with the bone then the cover screw was placed. The flap was repositioned and sutured. After 3 months, digital periapical radiographs were carried out to ensure implant osseointegration. Infiltration anesthesia was given around the implant site. The surgical-guide was reinserted to determine the implant position, then the implant cover screw was exposed and replaced with suitable healing abutment according to mucoperiosteum thickness covering the implant [Figure 1]. The denture was modified to allow the patients to wear the denture, then the healing abutment was replaced by final abutment after the formation of a gingival collar [Figure 2] and [Figure 3]. Pickup of the metal housings and magnet assay was carried out using self-cure acrylic resin.
Figure 1: Placing healing abutment of suitable size

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Figure 2: Ball abutment intraoral

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Figure 3: Magnet abutment intraoral

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Retention measurement (primary outcome)

There is no dropout; all patients completed the follow-up period. The retention was measured at the time of insertion 3, 6, and 12 months after prosthesis insertion for all participants. The procedure was started by identification of the geometric center of the mandibular arch to allow placement of the metallic loop. The digital force-meter machine was attached to the metallic loop to measure the retentive force of mandibular overdentures by applying a gradual pulling up force of the denture until it disengaged. The record appeared at the screen of the force meter (Extech 475040 digital force gauge), which is a single-blind measurement as the examiner knows the two different designs.

Questionnaire method (secondary outcome)

Patient satisfaction measured by Oral Health Impact Profile-14 (OHIP-14) was used where the five responses for each item are as follows: never, hardly never, occasionally, fairly often, and very often. Items were scored on a 5-point scale ranging from 0 (never) to 4 (very often) [Table 1]. Lower scores represent a higher patient satisfaction and better quality of life. The questionnaires were recorded at baseline (2 weeks), 3 months, and 12 months after prosthesis insertion for patients of all groups. All questionnaires were taken by the same research interviewer (assisted interviewer) as he was blind about the type of prosthesis as he is from another department. All questionnaires were in English form and translated during the interview.
Table 1: Comparison between retention forces (G) in the two groups

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Statistical analysis

Numerical data were explored for normality by checking the distribution of data and using tests of normality (Kolmogorov–Smirnov and Shapiro–Wilk tests). All data showed normal (parametric) distribution. Data were presented as mean, standard deviation (SD), and 95% confidence interval for the mean (95% CI) values. Repeated measures one-way analysis of variance (ANOVA) test was used to compare between the groups as well as to study the changes by time within each group. Bonferroni’s post hoc test was used for pairwise comparisons. The significance level was set at P < 0.05. Statistical analysis was performed with IBM SPSS Statistics for Windows, version 23.0 (IBM Corp, Armonk, NY, USA).

  Results Top

The data were collected for all patients without dropout. There was a decrease of retention throughout the follow-up period in both groups; the ball and socket group showed statistically significantly (P < 0.05) better retention force compared to that of magnet group at 0, 3, 6 and 12 months [Table 1]. Within all groups, there was a decrease in mean retentive force, but within the ball and socket group, there was a statistically significant decrease in mean retentive force from baseline to 12 months [Table 1]. There was an increase of patient satisfaction throughout the follow-up period in both groups; the ball and socket group showed statistically significantly (P < 0.05) higher mean of overall satisfaction compared to that of magnet group along all follow-up period [Table 2].
Table 2: Oral Health Impact Profile-14 (OHIP-14) scores within each group

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Ball and socket group showed a statistically significantly lower median score than the magnet group along all follow-up periods regarding both physical disability and physical pain, whereas for other five aspects “Handicap, Social disability, Psychological disability, Psychological discomfort, and Functional limitation” no significant difference was found between both groups [Table 2].

  Discussion Top

The use of ball and socket is clinically promising, which supports the study hypothesis. The superior retention of ball attachment is matching with the research hypothesis. Some studies showed that there is no significant difference between the magnet and ball attachment,[26],[27] whereas others showed better results regarding the ball attachment.[24] However, the latest systematic reviews do not provide a definitive conclusion as there is insufficient evidence to determine the relative effectiveness of different attachment systems on patient satisfaction as well as patient satisfaction may be independent of the attachment system. It was not possible to determine any preferred attachment system for mandibular overdentures.[2],[28] Using implants in completely edentulous patients has proven for many times their success in providing the denture wearer satisfaction and confidence regarding implant-supported over-denture.[29],[30] As the study denotes a decrease of retention along with the follow-up period that coincides with many investigations, explaining loss of retentive force over time is inevitable. This loss of retention has been attributed to wear of attachment components, which may be related to deformation that occurs during insertion and removal of the prosthesis.[4],[17] With advancement and modification of magnet such as the development of encapsulated and rare earth magnets that allow its use with implant systems. These magnets showed greater retentive forces and reduced susceptibility to wear and corrosion, as well as a low maintenance requirement and high success rate.[31],[32] Retention of overdenture is crucial for clinical success as the attachments that provide more retention against displacement will give more acceptable results of better oral function and patient satisfaction.[33] The ball and socket group showed superior retentive force through all follow-up period,[34] which may be attributed to the nature of mechanical interlocking between male and female parts, whereas the magnets are deprived of mechanical retention as well as no lateral stability. The magnets group showed a minimal reduction in retentive force, which might be due to microscopic corrosion that might occur within the stainless steel but of low value due to recent technology of magnet production, and the ball showed more wear during insertion and removal.[7] The satisfaction score for ball and socket is superior regarding physical pain and physical disability, which may be attributed to the mild difficulty in eating or uncomfortable eating of some kind of sticky food as the magnet does not provide resistance to lateral forces. Several studies concluded that the ball yields stable implant outcome and improved Oral Health-Related Quality of Life (OHRQoL).[35] Data need to be confirmed by further randomized trials with a larger sample size as well as studying magnet attachment regarding other parameters.


Within the limitation of this comparative study, the following conclusions were made:

Both implant-supported mandibular overdentures retained with magnet or ball and socket attachments consider a successful treatment option. The ball attachment provided more retention than the magnet attachment and led to improved patient satisfaction. This trial may form a base regarding the selection of best attachment regarding improving quality of life as well as the patients’ satisfaction.

Data availability statement

The data set used in this study is available on request.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2]


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