A systematic review and meta-analysis of the attachments used in implant-supported overdentures

Ball versus other attachments in mini implant retained overdenture: a systematic review and meta-analysis

OBJECTIVES

Mini implant retained overdentures have been treated in edentulous patients with promising long-term results. However, various attachment systems in this process remain insufficiently investigated. This systematic review and meta-analysis aimed to compare the effects of the ball and other attachments used in mini-implant overdentures. Marginal bone loss, bite force, implant survival rate, prosthetic maintenance, and complications were assessed.

MATERIALS AND METHODS

A systematic search was conducted across PubMed, Cochrane Library, and Scopus databases until 25th February 2025. This systematic review aimed to find studies that compare ball attachments with other attachment systems in mini dental implant (MDI) overdentures. The primary outcome was marginal bone loss, while the secondary outcomes were maximum bite force, implant survival rate, prosthetic maintenance, and complications. The risk of bias was assessed using the Cochrane risk-of-bias tool for RCTs, and a quantitative meta-analysis was performed.

RESULTS

Of the 561 publications, six randomized clinical trials (101 participants, 234 mini-implants) met the inclusion criteria. Risk of bias assessment revealed three studies with a low risk of bias and three studies with some concerns for risk of bias. There was no significant difference in the marginal bone loss between the ball attachments and others (WMD = 0.15, 95% CI -0.50 to 0.81, p = 0.65), though ball attachments performed better than telescopic ones (P < 0.05) in subgroup analysis. No significant difference in bite force was found (WMD = -5.29, 95% CI -33.46 to 22.87, p = 0.71). Two-year survival rates were 90.9% for ball and 97.8% for bar attachments. The ERA® (Extra-Coronal Resilient Attachment) group required five interventions (sore spot adjustments, relining, nylon replacements), while the ball attachment group required only two (denture repair, nylon cap replacement) over the one-year follow-up period.

CONCLUSIONS

Within the limitations of the study, it can be concluded that ball, bar, and ERA® attachments yield similar outcomes in marginal bone loss while telescopic attachments show more statistically significant marginal bone loss (p < 0.05). The type of attachment does not significantly affect maximum bite force.

PROSPERO REGISTRATION NUMBER

CRD42024610018.

Evaluation with finite element analysis of a ball attachment overdenture prosthesis of a patient

This study aimed to apply finite element analysis (FEA) to simulate the oral environment of a patient with an implant-supported overdenture prosthesis. A 3D mandibular model was created for a 45-year-old female patient from CT images, with mucosal thickness measured at 3 mm on average using ultrasonography. The overdenture prosthesis was scanned with an intraoral scanner and placed onto the 3D mandibular model. Displacement of the prosthesis and von Mises stress values of the implant, surrounding bone tissue, implant-prosthesis components, and mucosa were calculated under various masticatory loads. The study found that anterior mastication generated higher stress compared to unilateral and bilateral mastication. The addition of a third implant significantly reduced stress and improved prosthesis stability, particularly during bilateral mastication.

Finite Element Analysis (FEA) for Influence of Variation in Dental Implant Dimensions (Length and Diameter) on Peri-implant Bone Stress/Strain Distribution: A Systematic Review

Background & Objective

Currently, there are many implants in clinical use, making it hard to choose the right one for the patient. The success rate of an implant depends on its diameter, length, and direction of insertion in bone. In implant dentistry, Finite Element Analysis (FEA) simulates intraoral conditions in vitro and analyzes the effects of implant material, diameter, size, and other components related to oral structure on the implant and peri-implant tissues. The objective of the present systematic review was to evaluate the influence of variation in Dental Implant dimensions on Peri-implant Bone Stress/strain distribution, where Finite Element Analysis (FEA) is used as a method of analysis.

Method

Research papers published in PubMed, EBSCO, Web of Science, MEDLINE, CINAHL database from January 2012 until December 2022 using the keywords, (finite element analysis) AND (dental implant) AND (length) AND (diameter). The modified CONSORT checklist was used to assess the quality of the included research.

Result

Total hits from the original search were 402 (PubMed:127, Web of Science: 135 and CINHAL:22, EBSCO: 96, ProQuest:22). After duplicates were removed and titles and abstracts were screened, 371 articles were (n =371) selected for review. Of these, 342 were excluded and removed after initial screening, and 33 entire texts met the initial eligibility as per inclusion criteria. Four articles were further excluded in the final eligibility process and a total of 31 in vitro study articles were included for qualitative synthesis.

Conclusion

The evidence from the most recent literature suggests that the use of FEA showed promising results in understanding the stress distribution surrounding the implant. It was discovered that the material of the dental implant and the prosthesis, the type of loading, the direction and magnitude of force (axial or non-axial), the quality and quantity of the bone that surrounds the implant, as well as other factors, all play a role in the maintenance of bone around dental implants.

Effect of different implant positions for two implant-retained mandibular overdenture: a retrospective 5-years radiographic evaluation of the circumferential peri-implant bone loss and posterior ridge resorptive changes

BACKGROUND

Studies did not recommend which position for implant overdenture poses the lowest biomechanical risk and the least chance of peri-implant bone loss and ridge resorption for those who might need a mandibular two-implant overdenture. The study objectives were to investigate the impact of implant position, in lateral incisors or canine positions, on peri-implant bone loss and posterior ridge resorption.

METHODS

Fifty patients with mandibular two-implants were recalled and divided according to the implant position into two groups (group L: implants in lateral incisor positions and group C: implants in canine positions). The circumferential peri-implant bone level and posterior ridge resorption were assessed at implant insertion (T0), one year later (T1), and five years later (T5) using the follow-up CBCT. Data were analyzed using the Statistical Package of Social Science (SPSS) program. A Mann-Whitney test was used to compare two different groups. Paired groups were compared using the Wilcoxon signed-rank test. The threshold of significance is fixed at a 5% level (p-value).

RESULTS

Significant differences in the vertical bone loss between groups appeared at (T5 - T1) (Mann Whitney test, (P = 0.01)) and at (T5 - T0) (Mann Whitney test, (P = 0.005)), and a significant difference in horizontal bone loss between groups was found at (T1 - T0) (Mann Whitney test, (P = 0.041)) and (T5 - T1) (Mann Whitney test, (P = 0.041)). Also, there were significant differences over the evaluation period between groups at certain points along the ridge at M1 (Mann Whitney test, (P = 0.021)), M3 (Mann Whitney test, (P = 0.008)), and M4 (Mann Whitney test, (P = 0.015)).

CONCLUSIONS

According to the findings of this clinical study, the placement of implants in the lateral incisor position for two implant-retained overdentures is a viable choice. In comparison to the canine position, the lateral incisor position demonstrated superior peri-implant responses, which could potentially enhance the longevity of the implants. Furthermore, the placement of implants in the lateral incisor position can promote a more even distribution of stress and help mitigate posterior ridge resorption. Conversely, implants in the canine position may cause a seesaw effect and result in greater posterior ridge resorption.

CLINICAL TRIAL REGISTRY NUMBER

(NCT06055842) (13/03/2024).

Comparison of Clinical and Radiographic Outcomes Between Single Symphyseal and Parasymphyseal Implants Versus Two Implant-Assisted Complete Mandibular Overdentures

PURPOSE

This study aimed to compare the efficacy of single implants in the symphyseal and parasymphyseal regions with that of two implants in complete mandibular overdentures.

PATIENTS AND METHODS

Fifteen completely edentulous male patients (50-65 years) were chosen and randomly grouped into three equal groups (five patients in each) according to the position and number of the received implants to assist mandibular complete overdentures: group I: single median implant; group II: single parasymphyseal implant; and group III: two implants were inserted in the canine area bilaterally. After three months of osseointegration, the lower denture was transformed into an implant-assisted complete mandibular overdenture. Clinical observations were documented on the day of loading, and three, six, and nine months later for each implant. Follow-up cone beam computed tomography scans were performed to assess marginal bone loss on the day of loading, and six and twelve months later. The masticatory efficiency evaluation was conducted one and three months after loading.

RESULTS

The obtained results demonstrated insignificant differences between the three groups concerning marginal bone loss, plaque index, pocket depth, and bleeding index. Regarding the masticatory efficiency, the results revealed a significantly higher masticatory efficiency in group III than in groups I and II.

CONCLUSION

Using two implants to retain mandibular overdentures is the first choice due to their higher masticatory efficiency than a single implant. However, a single implant may be a viable treatment alternative, especially in cases where there are any limitations that restrict the use of additional implants.

An implant-supported overdenture for a mandibular defect after tumor resection guided by 3-dimensional finite element analysis: A clinical report

This clinical report describes the rehabilitation of a mandibular defect after tumor resection with an implant-supported overdenture and the attachment selection as guided by 3-dimensional finite element analysis. Autologous bone grafting was declined by the patient who demanded the restoration of lateral appearance and mastication function. Three implants were placed based on the condition of the bone, and a satisfactory definitive prosthesis was provided that corresponded with the results of the finite element analysis.

Evaluation of Peri-Implant Parameters and Functional Outcome of Immediately Placed and Loaded Mandibular Overdentures: A 5-year Follow-up Study

PURPOSE

To evaluate the peri-implant parameters of immediately placed and loaded mandibular overdentures over a 5-year follow-up period.

MATERIALS AND METHODS

All subjects who had been advised and planned for two-implant mandibular overdenture treatment were included in this study. The peri-implant parameters -including plaque index (PI), bleeding index (BI) and peri-implant pocket depth (PIPD) as well as marginal bone loss (MBL) - were assessed. In addition, prosthodontic parameters including abutment-, implant- and denture-related complications were assessed. Patients were evaluated at follow-up visits, scheduled at 1, 12, 24, 36, 48, and 60 months. The data distribution was analysed with the Shapiro-Wilk test. Data within follow-up categories were compared using ANOVA and the Tukey-Kramer test. A p-value < 0.05 was considered statistically significant.

RESULTS

Among the 32 participants, 19 were males and 13 were females, with a mean age of 60.5 ± 7.33. The mean plaque index (PI), bleeding index (BI) and peri-implant pocket depth (PIPD) varied over time. However, no statistically significant difference was observed in the plaque index, bleeding index and peri-implant pocket depth over time (p > 0.05). The mean value at baseline was found to be -0.9 ± 0.3. The values increased over time, with the highest value observed at 60 months 2.6 ± 0.7, which was statistically significant (p < 0.001).

CONCLUSION

Immediately placed and loaded mandibular implant overdentures using two un-splinted implants with locator attachments showed acceptable PI, BI and PIPD at the 5-year follow-up. Statistically significantly greater marginal bone loss was observed from baseline to follow-up, but it was within acceptable limits. A moderate number of restorative and abutment complications were observed during the follow-up of IODs.

Biomechanical Analysis of Palateless Splinted and Unsplinted Maxillary Implant-Supported Overdentures: A Three-Dimensional Finite Element Analysis

The objective of this study was to compare the distribution of stress in the maxillary bone, dental implants, and prosthetic components supporting implant-supported maxillary overdentures with partial palatal coverage, in both splinted and unsplinted designs. Two models of maxillary overdentures were designed using the Exocad Dental CAD program, which included cancellous and cortical bone. The complete denture design and abutments (locator abutments in the unsplinted and Hader bar with Vertix attachments placed distally in the splinted variant) were also designed. The denture material was PEEK (Polyetheretherketone), and the method used to analyze patient-specific 3D X-ray scans was 3D QCT/FEA (three-dimensional quantitative computed tomography-based finite element analysis). Loading was divided into three load cases, in the frontal region (both incisors of the denture) and distal region (both molars and first premolar of the denture). The forces applied were 150 N with an oblique component with a buccal inclination of 35° in the frontal region, and 600 N with a buccal inclination of 5° (molars) or solely vertical (premolar) in the distal region. The model with locator abutments showed higher stresses in all load cases in both analyzed implant variants and in the maxilla. The differences in stress distribution between the splinted and unsplinted variants were more significant in the distal region. According to the results of the present study, the amount of stress in bone tissue and dental implant parts was smaller in the splinted, bar-retained variant. The findings of this study can be useful in selecting the appropriate prosthetic design for implant-supported maxillary overdentures with partial palatal coverage.

The effect of ball versus locator attachment system on the performance of implant supported overdenture: A systematic review

Objective

This systematic review was aimed to compare ball and locator attachment system on the basis of clinical and biomechanical performance of implant supported overdenture as well as biological and patient related outcomes.

Material and methods

Open and free electronic and manual searches were performed in digital databases including MEDLINE via PubMed, the Cochrane Database of Clinical Trials, and Scopus along with some other reliable sources. From the 667 retrieved records, 11 full-text controlled trials were included in this study. Risk of bias was assessed according to RoB 2.0 except for one RCT (economic evaluation), only assessed by CASP checklist.

Results

From the 11 retrieved studies, total 183 locator and 219 ball attachments were identified in 452 subjects of 30 yrs-95 yrs of age. Studies provided data about prosthodontic complications or maintenance (replacement or the activation of matrix and patrix part, loss of retention, fracture and relining of the prosthesis, fracture of the attachment and the survival probability), oral health impact profile, soft tissue parameters and periodontal complications, marginal bone loss, patient related outcome and cost of the attachment systems. Only 5 studies were assessed at low risk bias, while other 6 at moderate to high risk of bias.

Conclusion

Locator attachment system show lesser complications including loss of retention and lower maintenance appointments, lesser soft tissue, and periodontal complications than the ball attachment. Ball is better in terms of cost effectiveness. In other related outcomes, no significant differences were noted between ball and locator attachment.

Factors influencing retention and durability of attachments for overdentures - adverse effects of cleansings, pH, and temperature: A systematic review

Aim

The objective of this systematic review is to show the current state of the art on which type of attachment loses retention the most and has reduced durability and which factor causes these problems the most.

Material and methods

This review followed the Preferred Reporting Items for Systematic Review and MetaAnalysis (PRISMA) guidelines and it was registered with the Open Science Framework (OSF) (osf.io/2e3q5). The databases used for the electronic search of articles were Pubmed, Science Direct, Embase, and Scopus. Articles were selected by 2 independent reviewers according to the inclusion criteria. The risk of bias was analyzed by using the Joanna Briggs Institute (JBI) adapted quasi-experimental study evaluation tool.

Results

The studies included in this review indicate that the use of cleansing solutions, high temperatures, and a more acidic pH decrease the durability of the attachments, mainly due to the loss of retention that occurs in different models and materials of the attachments, which requires their replacement in a shorter period.

Conclusion

Of all the factors studied, the cleansing solutions proved to be the factor that most altered attachment retention. Different saliva compositions did not influence retention values. Aging changes retention values for attachments, mostly with loss of values.

Peri-implant stress distribution assessment of various attachment systems for implant supported overdenture prosthesis by finite element analysis - A systematic review

Background

Various attachments like ball, bar-clip, magnetic attachments are used in implant supported overdentures. Finite Element Analysis (FEA) a newly innovated technology has been used in dental implantology to evaluate stress distribution patterns. There is little evidence available regarding the stress distribution in peri-implant region for implant supported overdentures. The purpose of the review was to generate scientific evidence on peri-implant stress distribution in FEA model with different types of attachments employed in implant supported overdentures.

Materials and methods

Systematic review was conducted as per the Preferred Reporting Items for Systematic Reviews Guidelines and Meta-Analyses statement (PRISMA). A comprehensive search was undertaken by two reviewers from January 2020 to June 2020 with no year limits to published articles. Only in-vitro FEA studies were included. Following electronic databases were searched for published studies- PubMed, Web of Science. Characteristics of the studies tabulated and analysis of articles was done to compare different attachment systems.

Results

Locator attachments showed better stress distribution than ball attachment system in all the studies but one. Two studies showed results in favour of ball attachment compared to bar-clip attachment system when stress was evaluated distal to the implants. No significant difference in terms of stress concentration could be generated between ball versus magnetic/equator versus locator attachment system due to less number of studies and conflicting results.

Conclusion

Various studies showed different results due to heterogenicity in selected attachment systems and study designs. Locator attachments showed favourable stress distribution around peri-implant bone than other attachments.

Mandibular implant-supported overdenture: A systematic review and meta-analysis for optimum selection of attachment system

Aim

This systematic review aimed to compare different attachment systems used in mandibular implant supported overdentures by assessing outcomes such as prosthodontic maintenance and complication, peri implant tissue changes, retention, and patient satisfaction for optimum selection of attachment system.

Settings and Design

This systematic review conducted following Preferred Reporting Items for the Systematic Review and Meta Analysis (PRISMA) guidelines.

Materials and Methods

A systematic electronic literature search was conducted through PubMed, The Cochrane Central Register of Controlled Trials (Central), and Science direct. A hand search was also performed for individual journals and reference lists of selected studies. Randomized controlled clinical trials and crossover clinical trials from 2010 to 2020 with follow up of more than 1 year were included. The Cochrane Collaboration's tool was used for assessing the risk of bias of included studies.

Statistical Analysis Used

The statistical meta analysis was performed using Review Manager (RevMan) [computer program]. Version 5.4. Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboation, 2020.

Results

Six studies that met the inclusion criteria possess the low risk of bias with follow up of more than 1 year were included in this systematic review. Out of four outcomes, meta analysis was performed for prosthodontic maintenance and peri implant tissue changes. Due to the limited availability of data, retention and patient satisfaction were reviewed systematically without meta analysis. The result of meta analysis for ball versus magnet attachment showed statistically significant differences in prosthodontic complications and maintenance, and ball attachment reported fewer complications than the locator attachment (risk ratio [RR] =0.55, confidence interval [CI] =95%, P = 0.03). Peri implant tissue changes were analyzed in the included studies as probing depth and marginal bone loss. The result of meta analysis for probing depth showed no statistically significant difference between bar versus telescopic type of attachment (RR = 0.20, CI = 95%, P = 0.74). The meta analysis results for marginal bone loss showed no statistically significant difference between bar versus telescopic type of attachment (mean difference = 0.35, CI = 95%, P = 0.10).

Conclusion

It can be concluded from the current review that bar attachment provided the most superior retention. The telescopic attachment system not only showed the most favorable patient's satisfaction but also reported the least peri implant mucosal changes. The ball attachment system is a favorable choice for limited inter arch space and parallel implant placement.

Biomechanical Aspects of Various Attachments for Implant Overdentures: A Review

There have been considerable recent technological developments for implant overdenture attachments. This study presents an overview of the biomechanical and biomolecular aspects of various attachments for implant overdenture. Available articles on attachments for implant overdenture were reviewed from January 1980 to August 2021 in the ScienceDirect, MEDLINE/PubMed, and Web of Science resources, and relevant studies were included in this study. We focused on the following topics: attachment systems, retention of various attachments, stress distribution with different attachments, the design and fabrication of attachments, digital techniques in overdenture attachments, and the effects of attachments in peri-implant health. We found that plastic resin is commonly used for ball and bar attachments, whereas nylon resin is commonly used in locator attachments. The locator system offers a valuable attachment option for implant-retained overdenture. Attachment retention reduces while lateral force increases with implant inclination in overdenture. The higher the retention of an overdenture attachment, the higher the transferred stresses. Additionally, clip loading produces more stress in implants and precision elements than bar-retained dentures. As such, we conclude that the ball and locator systems the best overdenture systems due to their superior tissue response, survival rate, and patient satisfaction.

Biomechanical Aspects of Various Attachments for Implant Overdentures: A Review

There have been considerable recent technological developments for implant overdenture attachments. This study presents an overview of the biomechanical and biomolecular aspects of various attachments for implant overdenture. Available articles on attachments for implant overdenture were reviewed from January 1980 to August 2021 in the ScienceDirect, MEDLINE/PubMed, and Web of Science resources, and relevant studies were included in this study. We focused on the following topics: attachment systems, retention of various attachments, stress distribution with different attachments, the design and fabrication of attachments, digital techniques in overdenture attachments, and the effects of attachments in peri-implant health. We found that plastic resin is commonly used for ball and bar attachments, whereas nylon resin is commonly used in locator attachments. The locator system offers a valuable attachment option for implant-retained overdenture. Attachment retention reduces while lateral force increases with implant inclination in overdenture. The higher the retention of an overdenture attachment, the higher the transferred stresses. Additionally, clip loading produces more stress in implants and precision elements than bar-retained dentures. As such, we conclude that the ball and locator systems the best overdenture systems due to their superior tissue response, survival rate, and patient satisfaction.