Attachment Systems for Implant Retained Overdentures: A Literature Review

Attachment systems for mandibular implant-supported overdentures: A systematic review and meta-analysis of randomized controlled trials

STATEMENT OF PROBLEM

Although mandibular implant-supported overdentures have been highly recommended as a treatment option, a consensus on the type of attachment systems that can be used to increase implant and prostheses survivability is lacking.

PURPOSE

The purpose of this systematic review and meta-analysis was to compare different types of attachments for retention by investigating outcome measures such as implant and prosthesis survival rates and biological and prosthesis complications in participants with a mandibular implant-supported overdenture.

MATERIAL AND METHODS

The search was performed in the PubMed, Cochrane, Embase, and Scopus databases by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria and registered with the International Prospective Register of Systematic Reviews (CRD42021253566). An analysis of association was conducted between different attachment systems and implant and overdenture survival rates in randomized controlled clinical trials.

RESULTS

The initial search indicated 477 studies, of which 25 randomized controlled trials (RCTs) were included for analysis. A total of 2154 implants and 737 overdentures were analyzed in the meta-analysis. The main results indicated the failure rate for dental implants to be 2.0% (95% confidence interval [CI], 1.3 to 3.2) and overdentures 4.2% (95% CI, 1.6 to 10.5), respectively. With regard to different attachment systems, a similar failure rate was identified with bar-type retention (7.7% to 95% CI, 3.0 to 18.1), magnetic retention systems (7.6% to 95% CI, 2.2 to 22.7), and ball-type retention (6.8% to 95% CI, 3.0 to 14.3). No significant difference was found in biological complications for splinted and unsplinted implant overdentures (P=.902). Regarding prosthetic complications, the most favorable groups were LOCATOR attachments followed by telescopic and Conus, bar, and ball attachments. Magnet attachments had higher prosthetic complications (7.4 times) than the other attachments.

CONCLUSIONS

Implants and implant-supported mandibular overdentures showed a high survival rate irrespective of the attachment system used. Splinting implants did not significantly affect the rate of biological complications. Prosthetic complications were most common for magnet and least common for LOCATOR attachments.

Assessment of Retention of Implant Bearing Mandibular Overdentures with Various Attachments: A Three-Year Follow-Up

Mandibular dentures are considered dubious in terms of retention in resorbed ridges. Implant bearing overdentures can be a solution to the abovesaid issue. Various attachments in use offer variations in retention and maintenance. The aim was to assess long term durability and retention of implant supported overdenture attachments. Two implant bearing overdentures were placed in 20 patients. Magnet and ball attachment were used and dentures were evaluated over a period of three years at different time intervals. Difference of attachments' performance between intervals was assessed with ANOVA test and Tukey HSD post hoc test and the level of significance was set at p<0.05. There was a decline in retention throughout research period in both categories; the ball and socket batch showed statistically significant (P<0.05) better retention force compared to that of magnet group. There was lesser decline in mean retention force of 10.97N±0.82 to 7.24N±0.903 from one month to three years in magnet attachment retained overdentures. Ball attachments offer better retentive forces than magnet category. Magnet bearing overdentures offer more durability in terms of retention.

Incorporating Stud Attachments in the Bar Design for an Implant-Supported Overdenture

Bone resorption following tooth loss might compromise retention, stability, and support of conventional removable prostheses, and for this reason, implant-supported overdentures are suggested as a viable alternative for completely edentulous patients. Bars, telescopic attachments, or stud attachments have been used to provide retention through a different mechanism of action based on specific design characteristics. The purpose of this report is to thoroughly describe the applied protocol for the fabrication of an implant overdenture supported by two bars incorporating stud attachments. A 67-year-old male patient presented to the Postgraduate Clinic of the National and Kapodistrian University in Athens seeking dental rehabilitation. The remaining teeth were characterized with poor prognosis, mainly due to their periodontal status. The proposed treatment plan included the placement of four implants in the maxilla and two implants in the mandible and the fabrication of implant-supported overdentures. The diagnostic stages revealed adequate prosthetic space that would enable the fabrication of a bar substructure for the maxillary overdenture. To combine the benefits of bars and stud attachments, two bars with four attachments were fabricated. Evaluation of the delivered prosthesis revealed adequate retention, support, and stability achieved with minimal palatal coverage. Patient's reported satisfaction and quality of life were increased. Recall appointments at one, six, and twelve months did not reveal any adverse effects or patient's complaints. According to the present case report, different types of attachments may be used after careful study of each case. More studies are needed to report on different aspects of the chosen treatment plan.

In vitro measurement of the retention force of two stud attachment systems during cyclic load

PURPOSE

To investigate the retentive behavior of the Locator legacy and Novaloc attachment systems with different retention inserts both within and across systems under cyclic load.

MATERIALS AND METHODS

Three retention inserts of each system (green, yellow, and white for Novaloc; green, orange, and red inserts for extended range for legacy Locator) were tested on abutments of both systems with a sample number of 10 per force and 10,000 cycles of insertion and removal. The loading was applied in the axial direction of the abutments, which were placed in artificial saliva. The retention force was measured in each cycle. The results were compared with the manufacturer's specifications and evaluated for a simulated period of use of 10 years. Characteristic time constants were determined, and subsequently, the two systems were compared regarding their wear behavior.

RESULTS

The manufacturer's specifications could only be confirmed for the green Novaloc retention insert on a Novaloc abutment (t-test: p = 0.50); for all other inserts, the baseline exceeded the manufacturer's specifications by 30%-75% (Novaloc; t-test: p < 0.001) and 75%-550% (Locator; t-test: p < 0.001). After 10,000 cycles performed, the manufacturer's specifications were confirmed on a Novaloc abutment for the white Novaloc retention insert (t-test: p = 0.86) and on a Locator abutment for the green Novaloc retention insert (t-test: p = 0.32). Both systems lost retention force during the experiment. Overall, Novaloc inserts on both abutments showed less wear (decrease to 56%-85% of initial force) and a slower decrease in retention force compared to Locator inserts (decrease to 6%-31% of initial force).

CONCLUSIONS

In both systems, wear leads to a varying loss of retention; therefore, regular checks with possible replacement of the inserts are necessary in clinical use. Novaloc attachments seem to be more resistant to the loss of retention than Locator attachments. A cross-combination may be clinically useful in some cases.

Effect of thermocycling on the retentive force of the retentive inserts in three denture attachments and their water absorption ability

This study aimed to evaluate the thermocycling effect on the retentive force of 3 different retentive inserts in 3 denture attachments (Blue, Pink, Clear retentive inserts in LOCATOR; Blue, Pink, Clear retentive inserts in LOCATOR R-Tx; and White, Yellow, Green retentive inserts in Novaloc) (n=10). Maximum retentive force of each retentive insert was evaluated at baseline, 7-day water storage, and after 5,000-, and 10,000- cycle thermocycling. The water absorption percentage of the retentive inserts was also determined. Comparing between baseline and 7-day water storage, the retentive forces of the LOCATOR and LOCATOR R-Tx groups were significantly reduced (p<0.05), while the retentive force of the Novaloc group was significantly increased (p<0.05). Comparing between 7-day water storage and 10,000-cycle thermocycling, the retentive force of most retentive inserts remained unchanged (p>0.05). The water absorption percentage of the LOCATOR and LOCATOR R-Tx groups was significantly greater than that of the Novaloc group (p<0.05).

Quantitative and qualitative assessment of the wear pattern of two attachment systems of dissimilar materials for mandibular implant-retained overdentures: an in-vitro study

BACKGROUND

Attachment material is one of the contributing factors to the degree of wear of the attachment components in mandibular implant-retained overdentures. The purpose of this in vitro study was to compare the wear behavior of 2 different attachment systems of dissimilar materials in mandibular implant-retained overdentures by qualitative and quantitative methods.

METHODS

Two attachment systems of different materials were utilized (n = 16); Titach (Dental Evolutions Inc, Beverly Hills, CA, USA) with a titanium-to-titanium interface and Locator R-Tx (Zest Anchors Inc, Escondido, CA, USA) with a titanium-to-nylon interface. One thousand cycles of overdenture insertion and removal simulating 1-year clinical use were performed. All matrices were removed from the overdentures and all patrices were unscrewed from the implants for wear assessment quantitively using a stereomicroscope and qualitatively using a scanning electron microscope. Data were analyzed by using an independent sample t test.

RESULTS

After cyclic loading, stereomicroscopic findings showed that the Titach group had statistically significant higher wear value than the Locator R-Tx group (p < 0.001). Moreover, scanning electron microscopy images showed noticeable abrasion in Titach patrix at the area of highest convexity. However, the Locator R-Tx matrix displayed an apparent tear of rubber inserts.

CONCLUSIONS

Titach attachment with the titanium-to-titanium interface revealed more wear than Locator R-Tx attachment with the titanium-to-nylon interface. Thus, the type of attachment material influences the degree of wear of the attachment components.

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.

Fabrication of CAD-CAM custom-made bar clip for implant-supported overdentures using an intraoral scanner: A dental technique

This article describes a digital technique for fabricating individually designed overdenture bar clips. The patient was scanned intraorally using a Medit i700 scanner; the custom clip was designed using the Blender software program and milled from polyoxymethylene blocks. This low-cost technique offers more available options compared with traditional clips, improving the management of retention loss.

Retentive force variations in three polyamide and a polyetheretherketone denture attachments for implant-supported overdentures: An in vitro study

STATEMENT OF PROBLEM

The loss in the retentive capability of implant-supported overdenture attachments has been related to the wear of the retentive inserts. Wear of the abutment coating material when following the replacement period for the retentive inserts requires investigation.

PURPOSE

The purpose of this in vitro study was to compare the changes in retentive force of 3 polyamide and a polyetheretherketone denture attachments under repeated insertion and removal cycles in wet conditions while following their manufacturers' replacement time recommendations.

MATERIAL AND METHODS

Four different denture attachments (LOCKiT, OT-Equator, Ball attachment, and Novaloc) with their retentive inserts were tested. Four implants were embedded into individual acrylic resin blocks, and 10 abutments for each attachment were used. Forty metal housings with their retentive inserts were attached to polyamide screws with autopolymerizing acrylic resin. A customized universal testing machine was used to simulate insertion and removal cycles. The specimens were mounted on a second universal testing machine at 0, 540, 2700, and 5400 cycles, and the maximum retentive force was recorded. The retentive inserts for LOCKiT (light retention), OT-Equator (soft retention), and Ball attachment (soft retention) were replaced every 540 cycles, while the Novaloc (medium retention) attachments were never replaced. All the abutments were weighed with a precision scale at 0, 2700, and 5400 cycles. The surface of every abutment was examined under a stereomicroscope at ×10 magnification. Data were analyzed with descriptive statistics. Two-way repeated measures ANOVA was used to compare the mean retentive force and mean abutment mass of all groups and time evaluation points. Bonferroni corrections were made to adjust for multiple tests (α=.05).

RESULTS

The mean retention loss for LOCKiT was 12.6% after 6 months and 45.0% after 5 years of simulated use. The mean retention loss for OT-Equator was 16.0% after 6 months and 50.1% after 5 years of simulated use. The mean retention loss for Ball attachment was 15.3% after 6 months and 39.1% after 5 years of simulated use. The mean retention loss for Novaloc was 31.0% after 6 months and 59.1% after 5 years of simulated use. The mean abutment mass difference was statistically significant (P<.05) for LOCKiT and Ball attachment but not statistically significant (P>.05) for OT-Equator and Novaloc at baseline, 2.5 years, and 5 years.

CONCLUSIONS

All tested attachments recorded retention loss under the experimental conditions, even when their manufacturers' recommendations for replacement time for the retentive inserts were followed. Patients should be aware that implant abutments should be replaced after a recommended period since their surfaces also change over time.

Double-Crown Prosthesis Retention Using Polyetherketoneketone (PEKK): An In Vitro Study

PURPOSE

To assess the retentive force of telescopic crowns using polyetherketoneketone (PEKK) high-performance polymer in relation to conventional materials over a long period of time in an in vitro setting.

MATERIALS AND METHODS

Thirty-six sets of primary and secondary crowns were fabricated as per the double crown-retained prostheses approach. Six samples were included in each of the five test groups (1: zirconia/PEKK [Zr/PEKK]; 2: titanium/PEKK [Ti/PEKK]; 3: cobalt-chrome/PEKK [CoCr/PEKK]; 4: PEKK/PEKK; and 5: gold/PEKK [Au/PEKK]) and the single control group (gold/galvano-gold [Au/GA]). The insertion-removal test was performed for 20,000 cycles, and the surface condition was observed. Retentive forces were analyzed using two-way ANOVA (α<0.05).

RESULTS

The retention forces in groups Zr/PEKK and Ti/PEKK significantly decreased over time (group 1: p = 0.035 and group 2: p = 0.001), whereas retentive force increased significantly in groups PEKK/PEKK, Au/PEKK, and control (group 4: p = 0.001, group 5: p = 0.008, and control: p = 0.042). Similar wear was observed on the primary crown in groups PEKK/PEKK, gold/PEKK, and control.

CONCLUSIONS

Groups PEKK/PEKK and Au/PEKK showed a transition of retentive force similar to the control group. Groups PEKK/PEKK and Au/PEKK had similar wear on the surface compared to control. Therefore, PEKK has a promising clinical potential.

Thermal Cycling Effect on Locator System Retention and Metal Surface Roughness

PURPOSE

To estimate the effects of the thermal cycling (TC) process on the metal surfaces of Locators, as well as retention loss, and the correlation between them.

MATERIALS AND METHODS

Twenty-five new Locator R-Tx were included in the study. Four areas were marked on each Locators' patrix metal surface and scanned using a confocal scanner (μsurf explorer; NanoFocus). Three surface roughness parameters were measured in the scans: Sa (average distance of peaks from the central plain of the area), Vmp (volume of the peaks in the area), and Spc (mean curvature of the peaks describing the degree of their sharpness). Retention test was performed using Instron® 4500 compression tension tensile tester at a speed of 10 mm/min. The retention tests were done using a working model made of two acrylic blocks in which the Locator system parts were inserted. The surface parameters measurements and the retention tests were performed 2 times, once before and once after TC. The Locators were subjected to 15,000 TC cycles by investing them into 2 tubs with different water temperatures, 55°C and 5°C. During each 60-second cycle, the Locators were submerged in each tub for 20 seconds, with a 10 second transition time between the tubs. The post-TC retention and surface parameters measurements were compared with those prior to TC and the prior to TC measurements served as controls. Changes in parameters before and after TC were analyzed by a two-way ANOVA nested model with random intercept and slope by restricted maximum likelihood method. Correlation between retention and surface parameters was quantified and examined using Kendall's correlation test. The findings were considered statistically significant if p < 0.05.

RESULTS

There was a significant decrease in retention of 16.6N at the second retention test (p < 0.001). A significant statistical decrease in surface parameters were measured after TC process, Sa and Vmp (18 ×10^-3 μm, p = 0.041 and 0.94 ×10^-3 1/μm, p = 0.001, respectively). A significant statistical increase in Spc of 6.4 ×10^-3 μm³ /μm² (p = 0.023) was noticed. The correlation between retention decreases and surface changes was not statistically significant.

CONCLUSION

The TC process causes a substantial reduction in retention to the Locator system over time. In addition, TC causes significant but minor changes to the Locator surface area. Most of the changes are in the horizontal dimension.

In vitro study of the effect of implant position and attachment type on stress distribution of implant-assisted removable partial dentures

Background/purpose

Implant assisted removable partial dentures (IARPDs) improved biomechanical behavior of removable partial dentures (RPDs), but information of the effect of attachment type and implant position is limited. This study aimed to investigate the effect of implant position and attachment type on the stress distribution of IARPDs.

Material and methods

Four implants, 10 mm in length and 4.1 mm in diameter, were bilaterally placed close to first premolar and second molar regions of a mandibular Kennedy class I model having artificial dentition from canine to canine, vertical to the occlusal plane. Five IARPDs were fabricated to accommodate locator and magnetic attachments. Strain gauges were placed on the model surface to measure the strain around implants during loading. Unilateral vertical loading was applied to the right first molar area with magnitude of 120 N and crosshead speed of 10 mm/min. Measurements were recorded under following conditions: premolar IARPDs with locator or magnetic attachments, molar IARPDs with locator or magnetic attachments. Two-way multiple analysis of variance was performed to compare the maximum principal strain (MPS) around the implants with a significance level of 0.05.

Results

Implant position had significant effect on the MPS of IARPD on loading and nonloading sides while attachment type only significant on nonloading side. Molar implants showed larger MPS than premolar implants with both locator and magnetic attachments during unilateral loading.

Conclusion

The stress distribution of the IARPD is significantly affected by implant position wherein anteriorly placed implants exhibit lower MPS than relatively posteriorly placed implants.

Mastication Wear of Two Low Profile Attachment Systems for Overdenture: An In Vitro Study

Background

Edentulism is still a major problem in the world's population today. Implant-retained overdenture has proven to be a valid therapeutic solution in the mandible. This type of rehabilitation requires replacement of the matrices when those reach inadequate retention due to wearing processes. This study is aimed at evaluating the drop in retention of low-profile precision attachments following the application of vertical chewing forces. Two different attachment designs were compared.

Methods

This in vitro study simulated an implant-retained overdenture on an edentulous mandible. Two low-profile attachments were compared. Loaded and unloaded sides were considered. Tests were performed by exerting a vertical cyclic force on the prosthesis at the level of the first molar of a hemiarch. Retention tests were performed before and after 400.000 chewing cycles, comparable to one year of use.

Results

The presence of vertical load wear was identified and characterized. Retention never fell below the values indicated by the manufacturer. Furthermore, significant differences were identified between the two retention systems.

Conclusions

Loss of occlusal load retention is a component that must be evaluated by the clinician during the design of implant-prosthetic rehabilitation, particularly in those cases where elevated occlusal forces or parafunctions are present.

Prosthetic complications and quality of life among wearers of mandibular overdenture with the Facility-Equator system

This longitudinal study aimed to assess the performance of the Facility-Equator system as mandibular overdenture (MO) retainers from a prosthetic perspective during 2 years of loading and to investigate the oral health-related quality of life (OHRQoL) and whether prosthetic events can affect the OHRQoL. Twenty-four patients (68.1 ± 7.51 years) reported their OHRQoL through the Geriatric Oral Health Assessment Index (GOHAI) and Oral Health Impact Profile (OHIP-EDENT) questionnaires before MO loading and after 1 and 2 years of usage. Prosthetic occurrences were recorded during this period. Data were analyzed using the Wilcoxon test, Mann-Whitney test, and Spearman correlation coefficients. Of the 127 prosthetic events that occurred in the first year, the most frequent events were prosthesis adjustments (16.5%), dislodgement of the Equator attachment (14.17%), and O-ring replacement (11.8%). Eighty-seven prosthetic events were recorded in the second year, the most frequent events being prosthesis adjustments (27.6%), O-ring replacement (20.7%), and recapturing the female matrix (11.5%). All domains of the GOHAI and OHIP-EDENT questionnaires exhibited a significant difference (p < 0.05) between the baseline and 1- and 2-year evaluations, except in the Social Disability and Psychological Discomfort domains (p > 0.05) of OHIP-EDENT after 1 year. Complications related to prosthetic maintenance, such as fracturing of the prosthesis, Equator dislodgement, prosthesis rebasing, and new overdenture confection, affect the OHRQoL (p < 0.05), primarily the Physical Pain and Discomfort domains, especially in the first year of MO loading.

Evaluation of retention and wear of a titanium-formed stud overdenture attachment with different interimplant angulations after simulated clinical use: An in vitro study

STATEMENT OF PROBLEM

How implant alignment impacts stud attachment retention and wear-induced alterations, notably when the attachment exhibits metal-to-metal frictional interlocking, is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of the interimplant angulation on retention forces and wear changes before and after 2 years of simulated clinical use of implant overdentures retained by titanium stud overdenture attachments.

MATERIAL AND METHODS

The canine regions of 3 identical edentulous mandibular models were used to receive 2 dental implants analogs with TiTach attachments (Dental Evolutions, Inc) at interimplant angulations of 0, 30, and 60 degrees. Six identical overdentures were constructed over each model (n=6). A universal testing machine was used to determine overdenture retention forces at 0, after 1440, and after 2880 insertion and removal cycles to simulate the average insertion and removal cycles in 12 and 24 months. A stereomicroscope, a laser microscope, and a scanning electron microscope were used to evaluate the wear in the attachments. A linear regression model, ANOVA, and the Kruskal-Wallis tests were used to analyze the data (α=.05).

RESULTS

All groups demonstrated reduced retention over the study duration (P<.001). The retention forces of the 0- and 30-degree groups were not significantly different after 2880 insertion and removal cycles, but both were significantly higher than those of the 60-degree group (P=.002). Within each group, the wear pattern of the matrix cap was more noticeable than that of the patrix abutment, with increased wear changes as interimplant angulation increased (P<.001).

CONCLUSIONS

TiTach attachments could retain overdentures on parallel and divergent implants with a 30-degree angle of interimplant angulation. However, at a 60-degree angle of interimplant angulation, considerable reduction in retention forces and increased wear changes were observed after 2 years of simulated clinical use.

Effect of Various Retentive Element Materials on Retention of Mandibular Implant-Retained Overdentures

This study aimed to examine the retentive characteristics of each retentive element material and the effects from thermocycling using the two implant-retained mandibular overdenture model. Two stud abutments and three retentive element materials; nylon, polyetheretherketone (PEEK) and polyvinylsiloxane (PVS) were used in this study. Four tested groups, with a total of 40 overdentures, were fabricated, including a Locator® abutment with nylon retention insert (NY), Novaloc® abutment with PEEK retention insert (PK), Locator® abutment with PVS retention insert (RL), and Novaloc® abutment with PVS retention insert (RN). The retentive force (N) was measured before thermocycling, and at 2500, 5000, and 10,000 cycles after thermocycling. Significant changes in the percentage of retention loss were found in the NY and PK groups (p < 0.05) at 6 and 12 months for the RL group (p < 0.05) after artificial aging. The RN group exhibited a constant retentive force (p > 0.05). The tendency of the percentage of retention loss significantly increased for PEEK, nylon, and PVS silicone over time. The results of the present study implied that retentive element materials tend to lose their retentive capability as a result of thermal undulation and water dispersion. Nylon and PEEK, comprising strong polar groups in polymer chains, showed a higher rate of retention loss than polyvinylsiloxane.

Maintenance requirements and marginal bone loss associated with implant-retained overdentures: a retrospective cohort study

OBJECTIVES

To evaluate the maintenance requirements and the presence of prosthetic complications associated with marginal bone loss in the implant-retained bar and locator prostheses.

MATERIALS AND METHODS

The study was executed between the years 2013 and 2018 on 114 patients who had undergone 283 dental implants. Patients were examined at follow-up recall sessions at 12 and 24 months after the placement of the dentures. The clinical examination also included intraoral and extraoral examinations of the patients; compatibility of the prostheses placed to about occlusion; an adaptation of the prosthesis to the tissues, health, and continuity of the soft tissues; complaints of the patients; implant success rates; and marginal bone loss, and prosthetic complications were evaluated at follow-up sessions, and statistical analysis was performed.

RESULTS

Locator attachment was placed in 94 patients with separated mandibles and maxillae, and a removable prosthesis with a bar attachment was placed in 20 patients. When evaluating the level of marginal bone loss regardless of the presence of complications, the area where the implant was set, the number of days after loading, and the type of retainer, it was found to be significant at the end of the 12th the 24th months. The results showed a significant relationship between the prosthesis type and the presence of complications at month 24 (p < 0.05). There was no significant relationship between the position of the denture and the presence of complications at month 12 (p > 0.05). There was no significant relationship between the location of the denture and the presence of complications at month 24 (p > 0.05).

CONCLUSION

Complications do not affect marginal bone loss, but the resulting marginal bone loss is the result of the patient not paying enough attention to oral hygiene. Routine inspections of the prosthesis after the completion of treatment seem to be important. If the requirements resulting from these checks are met, complications that may occur in the future will be prevented.

CLINICAL RELEVANCE

The maintenance requirements and the presence of prosthetic complications associated with marginal bone loss in the implant-retained bar and locator prostheses were evaluated. Complications occurred more frequently with the bar-supported removable implant prostheses.

Prosthetic failures in dental implant therapy

Both fixed and removable implant-supported prostheses are well-established methods for replacing missing teeth in partially or fully edentulous patients. Numerous systematic reviews have been performed in recent years to evaluate the survival and complication rates of implant-retained fixed dental prostheses and implant-retained overdentures, displaying high 5-year survival rates ranging from 97.1% for fixed dental prostheses to 95%-100% for implant-retained overdentures. However, the survival rates only represent the prostheses remaining in use for a defined follow-up time, and do not account for the potential prosthetic complications that may have arisen and influence the general success of the implant treatment. The most common technical complications of fixed implant-retained single crowns are crown fracture, fractures of ceramic implant abutments, and esthetic problems. The predominant technical complication at multiple-unit, implant-retained fixed dental prostheses is fracture/chipping of the veneering ceramic. Reported technical complications for implant-retained overdentures are overdenture fracture or chipping of the veneer materials, whereas mechanical complications include implant fracture, attachment failure, and attachment housing or insert complications. To reduce the risk of such failures, a comprehensive pretreatment diagnostic work-up is essential, including defining the prosthetic goal with the aid of a wax-up or set-up and the associated ideal, prosthetically oriented three-dimensional implant position. Furthermore, selection of the ideal type of prosthesis, including the respective implant components and materials, is important for clinical long-term treatment success.

Comparison of retentive force and wear pattern of Locator® and ADD-TOC attachments combined with CAD-CAM milled bar

PURPOSE

The purpose of this study was to investigate changes in retention and wear pattern of Locator® and ADD-TOC attachments on a digital milled bar by performing chewing simulation and repeated insertion/removal of prostheses in fully edentulous models.

MATERIALS AND METHODS

Locator (Locator®; Zest Anchors Inc., Escondido, CA, USA) was selected as the control group and ADD-TOC (ADD-TOC; PNUAdd Co., Ltd., Busan, Republic of Korea) as the experimental group. A CAD-CAM milled bar was mounted on a master model and 3 threaded holes for connecting a bar attachment was formed using a tap. Locator and ADD-TOC attachments were then attached to the milled bar. Simulated mastication and repeated insertion/removal were performed over 400,000 cyclic loadings and 1,080 insertions/removals, respectively. Wear patterns on deformed attachment were investigated by field emission scanning electron microscopy.

RESULTS

For the ADD-TOC attachments, chewing simulation and repeated insertion/removal resulted in a mean initial retentive force of 24.43 ± 4.89 N, which were significantly lower than that of the Locator attachment, 34.33 ± 8.25 N (P < .05). Amounts of retention loss relative to baseline for the Locator and ADD-TOC attachments were 21.74 ± 7.07 and 8.98 ± 5.76 N (P < .05).

CONCLUSION

CAD-CAM milled bar with the ADD-TOC attachment had a lower initial retentive force than the Locator attachment. However, the ADD-TOC attachment might be suitable for long-term use as it showed less deformation and had a higher retentive force after simulated mastication and insertion/removal repetitions.

Soft Tissue Dehiscence Associated with a Titanium Patient-Specific Implant: A Prosthetic Solution as an Alternative to Soft Tissue Grafting

Patients. This clinical report describes the detailed prosthodontic management of a 23-year-old male patient suffering from soft tissue complication following the placement of a 3d-printed titanium patient-specific implant. This implant was implemented simultaneously with the resection of a calcifying cystic odontogenic tumor related to the maxillary arch. Later, soft tissue dehiscence and implant exposure were encountered with subsequent food impaction, infection, and pus discharge. The treatment plan was to fabricate removable partial denture. The prosthesis was planned to be retained by bar and clip attachment on the patient-specific implant side, while on the other side, the removable prosthesis was allowed to engage two abutments with an embrasure clasp assembly in addition to covering the palatal tissues to offer protection for the soft tissue dehiscence against food impaction. Discussion. Soft tissue dehiscence and implant exposure are among the frequently reported complications associated with the patient-specific implant. The resulting infection complicates the prognosis of the implemented implant and necessitates, in some occasions, its removal. The selection of the removable prosthesis to cover soft tissue dehiscence was a conservative alternative to the implant removal as it protects the exposed titanium surface from food impaction while maintaining the implant functionality. Conclusion. Three-year follow-up showed complete resolution of the patient's complaints while fulfilling the patient's aesthetic and functional demands and indicates that the use of detachable overlay prosthesis could be one of the proposed treatment options.

Comparison of retention of two different attachment systems used in implant-supported overdentures

Aim:

This study aims to compare the retentive capacity of two attachment systems after manual thermocycling.

Settings and Design:

In vitro study and Comparative trail.

Materials and Methods:

An edentulous mandibular Polymethyl Methacrylate model was fabricated to receive the overdentures with the two attachment systems to be compared. Two dental implants were placed in the predetermined right and left mandibular canine regions of the model. A total number of eight overdentures, four per group, were fabricated over the two implants with two attachment systems to be compared; Bar and clip attachment system (Group-1) and Locator attachment system (Group-2). All the overdentures were subjected to 5000 alternating thermal cycles using manual thermocycling. Then the samples were subjected to 100 vertical pulls each in the anterior and posterior regions using a universal testing machine and the mean retentive forces were calculated for each sample in the anterior and posterior regions, respectively.

Results:

The mean retentive forces after 100 vertical pulls, were calculated and tabulated for each sample in the anterior and posterior regions separately. Then, the cumulative mean of the anterior and the posterior regions were calculated for each group. The cumulative mean retentive forces of both the attachment groups were-Group-1 (Bar and clip attachment system) = 27.87 N ± 4.01 and Group-2 (locator attachment system) = 18.85 N ± 2.50 with a P value of 0.021. This difference was found to be statistically significant.

Conclusion:

Within the limitations of the present in vitro study, the bar and clip attachment system offered better retention than the locator attachment system.

Implant-supported overdentures: part 1

The ability to provide high-quality complete dentures is a key skill for the GDP. The increasing prevalence and utilisation of implant-supported overdentures has opened the possibility of a wide variety of treatment options to support patient care, while also creating the need for primary care practitioners to have a greater awareness of commonly used prosthetic attachments.A thorough understanding of the advantages and disadvantages of implant-supported overdentures is essential to ensuring appropriate treatment planning, consent and maintenance. This two-part series explores various aspects of implant-supported overdentures including assessment of the patient, treatment planning, different attachment systems and maintenance requirements.Part one will explore availability of implants in the NHS, the commonly available implant attachment systems, including their relative advantages and disadvantages.

Experimental and numerical investigations of fracture and fatigue behaviour of implant-supported bars with distal extension made of three different materials

The aim of this study was to investigate experimentally the fatigue and stability of three bar materials with distal extension at the molar region and to numerically analyse the biomechanical properties of the bar materials connected to overdentures in a patient individual model. A milled bar was designed for the mandible on four implants in the canine and second premolar region. Three bar materials were investigated: titanium (Ti), cobalt chromium (CoCr), and polyetherketonketon (PEKK). Firstly, static and fatigue tests were performed based on EN ISO 14801 in a commercial permanent loading set-up. Unilateral axial force was applied on the distal extension of the bars. Secondly, numerical models were created. Different bar materials and loading scenarios were analysed. The static fracture limit of the three materials was 1,750 N, 780 N, 310 N for Ti, CoCr, and PEKK, respectively. The Wöhler curves showed comparable fatigue limits of 200 N, 160 N, and 150 N for titanium, CoCr, and PEKK, respectively. The stress at the distal extension was 2,600 MPa (Ti), 1,000 MPa (CoCr), and 270 MPa (PEKK). All loading simulations with the PEKK bar showed higher stresses in the implants and in the bone bed as well as higher displacements of the over denture in comparison to metal bars. PEKK showed different mechanical behaviour compared to Ti and CoCr. The distribution of stresses within the PEKK bar was wider than the area of loading which probably leads to fatigue of the whole bar and not only the part under load.

Effect of specific retention biomaterials for ball attachment on the biomechanical response of single implant-supported overdenture: A finite element analysis

PURPOSE

The purpose of this finite element analysis (FEA) was to evaluate the effect of specific retention biomaterials with different elastic modulus on the biomechanical response to the axial and off-axial biting loads of a mandibular midline single implant-supported overdenture (SIO) model.

METHODS

Five 3-dimensional (3D) finite element models of an edentulous mandible with SIO were designed as follows: model M with a titanium retentive element for ball attachment, model P with a PEEK retentive element, model S with a silicone resilient liner retentive element, model T with a thermoplastic acrylic resin retentive element made from a CAD-CAM material, and model A with a polyacetal resin retentive element. Posterior bilateral vertical load (PV) at the 1st molar areas and anterior oblique load (AO) at the incisal edge of the mandibular central incisors at a 30-degree angle of 100 N were applied. Stress values were recorded.

RESULTS

Stress values were higher for all models under (AO) loading than under (PV) loading. Model M recorded the highest stress values on the implant, its components, cortical, and cancellous bone under both loading conditions. Under (AO) loading condition, the ball abutment von Mises stress value in model S was almost 7 times lower than that of model M (19 and 130 MPa respectively) and the other 3 models (P, T, and A) (119, 121, and 120 MPa respectively). However, model S recorded the highest value of denture base stress at the attachment area.

CONCLUSIONS

The elastic modulus of retention materials can affect stresses generated on the implant overdenture components and supporting structures.

Clinical Performance of Implant Crown Retained Removable Partial Dentures for Mandibular Edentulism-A Retrospective Study

The studies on implant-crown-retained removable partial dentures (IC-RPDs) for edentulism are scarce. The purpose of this study was to evaluate survival rates and marginal bone loss (MBL) of IC-RPDs compared to implant overdentures (IODs) in mandibular edentulism. Variables that influenced survival and marginal bone loss (MBL) of implants in both treatment modalities were analyzed and the functional/esthetic satisfaction of patients as well as prosthetic complications were also observed. Eighteen IC-RPDs with a total of 60 implant-supported survey crowns and 24 IODs with a total 94 implants retained with magnet attachments were observed. After a median observation period of 46.6 months (up to 149 months), we observed 98.3% implant survival rates for IC-RPDs and 92.5% for IODs. Kaplan–Meier survival curves based on the treatment modality showed that, at 96 months, cumulative survival rates were 98.3% in IC-RPD and 83.1% in IOD. For implant survival rates, no statistical differences were observed according to age, sex, opposing dentition, or implant positions (p = 0.515, 0.666, 0.201, 0.749, respectively). The implant MBL measurements for IC-RPD and IOD groups at the final recall check were 0.93 ± 1.22 mm and 2.12 ± 2.09 mm, respectively. Additionally, there were no significant differences between groups (p = 0.554). The implants with peri-implantitis at year 1 showed significantly higher MBL at final check-up (p < 0.001). The MBL of implants showed significant differences based on age (p = 0.008) and opposing dentition (p = 0.003). No significant differences of implant MBL were observed for the position of placed implants (p = 0.621) or sex (p = 0.666). Patient-reported outcome measures (PROMs) on functional and esthetic satisfaction were significantly improved after IC-RPD or IOD treatment (p < 0.001). The most frequent prosthetic complication of IC-RPD was clasp loosening, while for IOD group, it was attachment dislodgement. Within the limitations of this retrospective study, we concluded that IC-RPDs could be considered as a viable treatment option for edentulous patients who need few fixed abutments for satisfaction.

Patient satisfaction and survival of maxillary overdentures supported by four or six splinted implants: a systematic review with meta-analysis

Background

Implant-supported overdentures offer enhanced mechanical properties, which lead to better patient satisfaction and survival rates than conventional dentures. However, it is unclear whether these satisfaction levels and survival rates depend on the number of implants supporting the overdenture. Therefore, this systematic review aimed to compare maxillary overdentures supported by four or six splinted implants in terms of patient satisfaction, implant survival, overdenture survival, and prosthodontic complications.

Methods

Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (PubMed), and EMBASE databases were systematically searched and complemented by hand searching from 2000 to 2019, employing a combination of specific keywords. Studies comparing the use of four versus six implants for supporting overdentures with at least one-year of follow-up after prosthesis installation and including ten fully edentulous patients were included. The risk of bias (RoB) was analyzed with Cochrane’s RoB 2 and Newcastle–Ottawa tools. Implants and prosthesis survival rates were analyzed by random-effects meta-analysis and expressed as risk ratios or risk differences, respectively, and by the non-parametric unpaired Fisher’s test.

Results

A total of 15 from 1865 articles were included, and reported follow-up times after implant placement ranged from 1 to 10 years. Irrespective of the number of implants used, high scores were reported by all studies investigating patient satisfaction. Meta-analysis and non-parametric Fisher’s test showed no statistical differences regarding the survival rate of implants (P = 0.34, P = 0.3) or overdentures (P = 0.74, P = 0.9) when using 4 versus 6 splinted implants to support overdentures, and no significant differences regarding prosthodontic complications were found between groups. Randomized studies presented high RoB and non-randomized studies presented acceptable quality.

Conclusions

Within the limits of this systematic review, we can conclude that the bar-supported overdenture on four implants is not inferior to the overdenture supported by six implants for rehabilitating the edentulous maxilla, in terms of patient satisfaction, survival rates of implants and overdentures, and prosthodontic complications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01572-6.

Influence of different materials on retention behavior of CAD-CAM fabricated bar attachments

STATEMENT OF PROBLEM

Loss of retention with implant overdentures is a problem that might be addressed with materials such as a recently introduced biocompatible high-performance polymer (BioHPP). However, in vitro studies investigating this product are lacking.

PURPOSE

The purpose of this in vitro study was to assess the retentive behavior of implant overdentures and the loss of retention from clip wear when used with computer-aided design and computer-aided manufacturing (CAD-CAM) fabricated bar attachments from cobalt-chromium (Co-Cr), zirconia (ZrO₂), and BioHPP to identify the optimal material in terms of minimal loss of retention and minimal wear.

MATERIAL AND METHODS

Three CAD-CAM bar attachments were fabricated from the different materials and cemented to a completely edentulous mandibular model for testing. Twelve plastic clips were allocated to each material and subjected to 1095 dislodgement cycles to simulate a year of clinical use. A universal testing machine was used to measure the retentive force of dislodgement of each clip for each material before and after cycling. An inverted optical measuring microscope was used to quantify the amount of wear on each clip. One-way repeated-measures ANOVA was used to analyze the results among the materials and the decrease in retention force. The paired t test was used to compare clip measurements before and after testing (α=.05).

RESULTS

BioHPP bars retained retention significantly better than Co-Cr or ZrO₂, with a lower percentage decrease in mean retentive force. Clips used with BioHPP bars also exhibited the least wear. However, Co-Cr and ZrO₂ displayed similarly higher initial retentive values in comparison with BioHPP, with Co-Cr displaying the highest final retention.

CONCLUSIONS

BioHPP appears to be a strong candidate to replace Co-Cr or ZrO₂ for fabricating bar attachments as it displayed minimal loss of retention and led to the least wear of the clip, thereby reducing replacement frequency.

Evaluation of changes in mechanical properties of O-ring in one-piece and two-piece ball retained implant-supported overdentures: A three-year retrospective study

The o-rings in ball retained overdentures deteriorate with time and need replacement to restore the retentive quality. We evaluated retrospectively the mechanical properties of o-rings after 3 years in function in one and two-piece implant-supported overdentures. The o-rings were retrieved from one-piece (Myriad snap, Equinox-Straumann, 3.3 x 13mm) and two-piece (Neo Biotech, 3.3 x 13mm) implant-supported overdenture patients. A total of 16 pairs of matrices were tested for wear, type of damage and elasticity using Pin on Disc method, USB Digital Camera in 30x zoom and Universal Tensile Machine respectively. The statistical analysis for independent groups were done with the Mann-Whitney U test. Assessment of used O-rings showed 84% more wear in the two-piece system with an abrasive type of damage while 46% wear in the one-piece system with a compressive type of damage. The o-rings in one-piece system showed increase in elongation and maximum displacement to 2% and 7% respectively, while two-piece system showed decrease in elongation and maximum displacement by 13% and 6% respectively. In one-piece system, the loss of retention was more with slow wear rate and in two-piece system, the wear resistance of O-rings decreased due to increased stiffness. Further studies to evaluate the changes in O-ring with increased sample size and at interval 1 year will pave way for insight into the progressive changes in the mechanical properties of an O-ring.

Maintenance and risk factors for fractures of overdentures using immediately loaded conventional diameter or mini implants with Locator abutments: A cohort study

BACKGROUND

Fractures in mandibular implant-retained overdentures are a common complication. However, little is known on the related risk factors and outcome differences when using two conventional diameter or two mini implants.

PURPOSE

The purpose of this study was first, to evaluate the required maintenance and complications with the overdentures and second, to analyze risk factors for overdenture fractures.

MATERIALS AND METHODS

This cohort study was conducted in edentulous patients with complete dentures. Patients received either two conventional (4.1 mm in diameter) and two mini (2.9 mm or less in diameter) implants, based on available buccal-lingual ridge width. All implants were immediately loaded with mandibular overdentures retained by Locator abutments. The number of prosthodontic after care visits (scheduled and unscheduled) were recorded and compared between the two implant diameter groups. Fracture occurrence was the primary outcome variable. Risk estimates were presented as odds ratios (ORs) with 95% confidence intervals (CIs). The ORs were adjusted for potential clinical confounders (ie, necessity of relining, matrix recapture, abutment loosening, implant diameter, height of the Locator, and retention force).

RESULTS

A total of 50 edentulous patients were analyzed. One conventional diameter and three mini implants failed within a 1-year follow-up period. Prosthetic maintenance requirements for overdentures on both implant diameter groups were comparable. A total of 12 overdenture fractures (four in the mini implant group and eight in the conventional diameter group) occurred. Adjusted OR (AOR) analysis showed a significant association between abutment loosening and overdenture fracture (AOR = 12.00, 95% CI = 1.11-129.45; P = .041).

CONCLUSION

Within the limitations of this study, the present findings suggest that implant diameter does not affect number of prosthetic maintenance and complications, and that abutment loosening is a risk factor for overdenture fractures, regardless of the implant diameter used.

Masticatory function and oral health-related quality of life of patients with atrophic and non-atrophic mandibles using implant-retained mandibular overdentures: 3-year results of a prospective clinical study

BACKGROUND

Long-term changes in masticatory function, oral health-related quality of life (OHRQoL) and prosthetic complications in implant-retained mandibular overdenture (IMO) wearers as a function of bone atrophy require detailed investigations.

OBJECTIVE

Investigating the evolution of masticatory function, OHRQoL and prosthetic occurrences of IMO wearers according to mandibular bone atrophy over 3 years of usage.

METHODS

This study evaluated 26 IMO wearers after 2 and 3 years of IMO loading categorised according to mandibular resorption degree into atrophic mandible (AM) and a non-atrophic mandible (NAM) group. Masticatory function was assessed by the Masticatory Performance (MP) and Swallowing Threshold (ST) tests; OHRQoL and satisfaction via the Dental Impact on Daily Living (DIDL) questionnaire; and the prosthetic maintenance requirements and complications were monitored.

RESULTS

After the second year, the AM Group performed 32% more cycles (P = .047) than the NAM Group during the ST test. The DIDL questionnaire showed no significant difference for all domains, except for a moderate effect size in the General Performance domain after the third year. AM Group had more prosthetic occurrences (n = 109) than NAM Group (n = 60) in the first year, mainly due to Equator attachment dislodgment. During the third year, NAM Group presented a greater number of events (n = 45) than AM Group (n = 21) due to the greater number of O-ring exchanges.

CONCLUSION

Masticatory function and OHRQoL are not related to mandibular bone atrophy until 3 years after IMO rehabilitation. The prosthetic complications profile differs between groups, mainly in the first year.

Retentive Characteristics of a New Attachment System for Hybrid Dentures

Removable implant-anchored dentures have become an established treatment concept especially for older, multimorbid patients. This study investigates the retention force (RF) of two different attachment systems. A total of 96 specimens (n = 8 for each condition) were fabricated and RF was measured under different conditions: fatigue (10,000 cycles dislodging), thermal undulation (5/55 °C, 5000 cycles) and implant-angulation (0°, 5°, 10°, 15°, 20°). The Novaloc system ((N), 0° and 15° abutments, yellow matrix (Y)) was compared to the Locator system ((L), pink (P) and orange (O)). Initial RFs (8.57 ± 0.99 N (NY), 19.39 ± 8.10 N (LP), 8.8 ± 5.28 N (LO)) were reduced by ageing simulation (26% (NY), 66% (LP), 89% (LO); p < 0.001). After thermocycling, Novaloc’s RFs decreased by 33% (p < 0.001) while the Locators’ RFs increased by 34% (LP: p = 0.002, LO: p = 0.148). In contrast to LP, the RFs of Novaloc abutments and LOs predominantly showed no clinically relevant dependence on implant angulation. Ageing processes tended to result in lower RFs at higher implant angulation. Thus, the Novaloc attachment system offers an alternative to Locator attachments. It is characterized by a comparatively continuous RF-curve over the entire wearing period. Future clinical studies have to be conducted to verify the in vitro demonstrated advantages of the Novaloc system.

Immediately loaded mini-implants supporting mandibular overdentures: A one-year comparative prospective cohort study

BACKGROUND

Little is known about differences between mini-implants and conventional immediately loaded implants for overdentures.

OBJECTIVES

To compare clinical outcomes using two immediately loaded conventional or mini-implants for mandibular overdentures.

MATERIALS AND METHODS

Edentulous patients receiving either conventional (4.1 mm) or mini-implants (2.9 mm or less), based on available bone width were analyzed. All implants were immediately loaded with mandibular overdentures installed using locator attachments. Digital periapical radiographs for measuring marginal bone loss and clinical outcomes (ie, periodontal probing, plaque, and bleeding indices) were assessed at 1, 3, 6, and 12-month follow-up periods.

RESULTS

Fifty patients (25 receiving conventional implants-12 females, mean age of 65.3 ± 7.3 years; and 25 receiving mini-implants-11 females, mean age of 66.8 ± 8.1 years) was analyzed. Peak insertion torque (P = .001) and bone loss (P = .02), as well as change in plaque (P = .02) and bleeding (P = .04) indices at 12 months differed significantly between groups. Furthermore, linear regression revealed the height of the locator as a risk factor for bone loss (P = .038).

CONCLUSIONS

The present findings suggest that two mini-implants are significantly more susceptible to bone loss after immediate loading, for which the height of locator might be considered a risk factor.

Rehabilitation of a Unilateral Cleft Palate with Endosseous Implants in an Edentulous Elderly Patient

The objective was to describe the use of a maxillary obturator supported by dental implants and ball abutments in an adult edentulous unilateral cleft patient. Adult edentulous cleft patients who have had no corrective surgeries or failed attempts at cleft repair in childhood suffer from oronasal communication resulting in hypernasal speech, dysphagia, and compromised masticatory ability. Tissue-supported obturator prostheses in such patients provide for compromised function due to instability and lack of retention. The treatment using fibromucosal-supported obturators is well established in the literature; few articles have also described osseointegrated implants supporting the prosthesis in adult cleft patients supported by bar attachments and magnets; however, reports of implant-supported maxillary obturators retained by ball/stud attachments are scarce. The implants provided retention and stability to the prosthesis, simplifying the laboratory procedure using ball abutments, improving swallowing, speech, and the patient's general quality of life. This article reports the rehabilitation of an adult cleft palate patient with a totally edentulous maxilla using an implant-retained prosthesis.

Retention and wear of resin matrix attachments for implant overdentures

OBJECTIVES

The aim of the present laboratory study was to investigate the retentive properties and the wear of three different resin matrix attachments for implant overdentures as well as to assess the effects of implant angulation.

METHODS AND MATERIALS

Three attachment systems with either polyetheretherketone inserts (PEEK; Novaloc, Straumann, Basel, Switzerland), polyetherketoneketone inserts (PEKK; CM Loc, Cendres + Métaux, Biel, Switzerland) or nylon inserts (Locator R-Tx, Zest Dental Solutions, Escondido, California, USA) were evaluated. The patrices were connected to their implant analogues and fixed in a resin cast at implant angulations of 0° and 15°. The corresponding matrices with inserts were fixed in a stylized unilaterally removable dental prothesis. To simulate masticatory forces 30,000 insertion and removal cycles with an eccentric load of 100 N at a distance of 12 mm were performed in a chewing simulator. The retention forces were measured. The wear patterns were examined using a scanning electron microscope (SEM). The statistical analysis was performed using a one-way ANOVA followed by a Games-Howell test and a Friedman test.

RESULTS

All attachment systems revealed a significant decrease in retention after testing, except PEEK 0°/0° and PEEK 15°/15°. PEEK and PEKK attachment systems showed significantly higher retentive forces than the nylon attachment system between 5000 and 30,000 cycles. The implant angulation did not significantly influence the retention behavior for any of the three attachment systems. Patrices showed no signs of wear, whereas the matrix inserts displayed signs of deformation.

CONCLUSION

Within the limitations of the present study, attachments with PEEK and PEKK inserts combined with titanium patrices are favorable for long-term use, both for orthogonal and tilted implants. All three attachment systems showed a high variability of the retentive forces at baseline and for subsequent cycles. This should be taken into consideration for clinical use.

Comparison of stress induced in mandible around an implant-supported overdenture with locator attachment and telescopic crowns - a finite element analysis

Introduction

One of the principle factors for the success of implant supported/retained overdentures (IOs) is the manner in which the stresses are transferred to the surrounding bone. Hence, the aim of the present study is to compare the stress induced in the mandible around IOs, using two different attachment systems, locator and telescopic.

Methods

3D finite element models were prepared using Pro/ENGINEER or PTC Creo to simulate 4 clinical situations: IOs using two different attachment systems, locator and telescopic, with and without splinting. A vertical compressive load of 35N was directed toward the central fossa in the molar region of each overdenture. Non-linear static contact analysis was carried out to determine the stress distribution in various components of IOs. Then, the models were analyzed by a finite element program ABAQUS, and displayed using Von Mises stress patterns.

Results

The contact stress values developed on the implant and attachment components were lower with locator attachment, in both splinted and non-splinted models. On the other hand, the stress distribution to the cortical bone was more with non-splinted/splinted locator attachments (3.73/4.12 Mega Pascals) when compared to the non-splinted/splinted telescopic attachments (2.66/3.7 Mega Pascals). The stresses in all the components of overdenture were greater with the splinted model compared to non-splinted, in both the attachment systems.

Conclusion

The locator attachment might demonstrate superior clinical performance, as the stresses on implant and attachment components were less compared to telescopic. Non-splinted model showed better results in both the attachment types.

Retention of mandibular implant-retained overdentures with two different attachment designs: An in vitro study

STATEMENT OF PROBLEM

Retentive force and loss of retention should be considered when selecting an attachment. Studies that evaluate the retentive force and the effect of repeated cycles of insertion and removal on the TITACH attachment with a metal-to-metal interface are needed.

PURPOSE

The purpose of this in vitro study was to measure the retention of mandibular implant-retained overdentures with 2 different attachment designs before and after 1000 insertion and removal cycles.

MATERIAL AND METHODS

Two dental implants were inserted at the mandibular canine region bilaterally in a completely edentulous model. Sixteen mandibular implant-assisted overdentures were fabricated to form 2 groups, each with a different attachment design. One group received 8 pairs of TITACH attachments, while the other group received 8 pairs of LOCATOR attachments. A cyclic loading machine was used to perform 1000 insertion and removal cycles. A universal testing machine was used to evaluate retentive force before and after insertion and removal cycles. Data were analyzed by using the Mann-Whitney U test and Wilcoxson signed-rank test.

RESULTS

When retentive forces before and after 1000 insertion and removal cycles were compared, the TITACH attachment showed significantly higher retentive force than the LOCATOR (P<.05). However, the LOCATOR attachment showed a significantly lower percentage change in retentive force (P<.05).

CONCLUSIONS

The TITACH attachment group showed favorable initial and final retentive force compared with the Zest Anchor LOCATOR attachment group. However, the LOCATOR attachment group showed favorable lower percentage change in retentive force.

Mechanical behavior of implant assisted removable partial denture for Kennedy class II

Background

This study evaluated the mechanical response of a removable partial denture (RPD) in Kennedy Class II according to being associated or not with implants.

Material and Methods

Four RPDs were manufactured for a Kennedy Class II: CRPD - Conventional RPD, RPD+1M, RPD+2M and RPD+12M, respectively, signifying implant assisted RPDs with the implant installed in the first molar, second molar, and in the first and second molars. The finite element method was used to determine the most damaged support tooth under compressive load (300N, 10s) and strain gauge analysis was used to evaluate the microstrain. All groups were submitted to a retentive force analysis (0.5 mm/mm, 100kgf). Microstrain and retentive force data were submitted to One-way ANOVA and the Tukey test, all with α=5%.

Results

High microstrain was observed in the second premolar adjacent to the edentulous space under compression load (p< 0.01). RPD+12M presented lower microstrain, however being similar to RPD+2M. RPD+1M presented a higher mean value of retentive force, but similar to RPD+12M. FEM showed RPD assisted by implants concentrates less stress in the periodontal ligament. The association of two implants was sufficient to decrease the stress generated in the implants. The most stressed region for the o-ring abutment was the threads, and the group with two implants showed the lowest stress concentration.

Conclusions

In cases of Kennedy Class II, the association of RPD with implants in the molar region is a favorable option for patient rehabilitation, reducing the movement of the direct retainer adjacent to the edentulous space, increasing the removal force and decreasing the stress magnitude in the periodontal ligament. Key words:Removable partial denture, Finite element analysis, Prosthetic dentistry, Implant-assisted RPD, Distal extension RPD considerations.

Hard and soft-tissue evaluation of bar-clip, ball-socket, and kerator attachments in mandibular implant overdenture treatment: An in vivo study

Aim:

The aim of this in vivo study was to evaluate and compare the soft and hard tissue changes in implant supported mandibular overdenture with three different attachment system.

Settings and Design:

In vivo – observation study.

Materials and Methods:

After evaluation of prosthetic space, fifteen edentulous subjects received two implants in the inter-foramina region of the mandible and were divided into 3 groups with 5 subjects each, delayed loading protocol was followed in all the patients. The crestal bone loss, modified sulcular bleeding index, plaque index values were evaluate with the attachments at baseline and after 6 months was measured in a standardised way.

Statistical Analysis Used:

Oneway ANOVA test and post hoc Bonferroni multiple test.

Results:

At the end of six months modified sulcular bleeding index and plaque index values was higher in Group 2 (bar and clip attachment) as compared to Group 1 (ball and socket attachment) and Group 3 (Kerator attachment) and crestal bone loss was equal in groups 1, 2 and 3. Analysis of variance with repeated measures showed significant differences in modified sulcular bleeding index and plaque index among the three attachment types.

Conclusion:

(1) Group 2 (bar-and-clip attachment) exhibited higher Modified Sulcular Bleeding Index and Plaque Index values than Group 1 (ball-and-socket attachment) and Group 3 (kerator attachment). (2) Crestal bone loss was equal in Group 1 (ball-and-socket attachment), Group 2 (bar-and-clip attachment), and Group 3 (kerator attachment).

Effect of mucosa thicknesses on stress distribution of implant-supported overdentures under unilateral loading: Photoelastic analysis

INTRODUCTION

The aim of this study was to evaluate the effect of different heights of attachment and mucosa thicknesses on the stress distribution of two implant-retained mandibular overdenture designs under loading using the photoelastic stress analysis method.

MATERIALS AND METHODS

Six photoelastic models of an edentulous mandibula were fabricated with two solitary implants that were placed in the canine regions. The attachment systems studied were ball and locator stud attachments. Both the ball and locator groups included three models that had different residual ridge heights so as to provide different mucosa thicknesses (1 mm-1 mm, 1 mm-2 mm, 1 mm-4 mm). A static vertical force of 135 N was applied unilaterally (each on the right then the left side) to the central fossa of the first molars. Models were positioned in the field of a circular polariscope to observe the distribution of isochromatic fringes around the implants and the interimplant areas under loading. The photoelastic stress fringes were monitored and recorded photographically.

RESULTS

The ball attachment groups showed higher stress values than did the locator groups under loading. Both attachment systems produced the lowest stress values in stimulated 1 mm-1 mm mucosa thickness models. The models with 1 mm-2 mm mucosa thicknesses showed higher stress values than did other models for both attachment systems. The highest stress value observed around both attachment systems was the moderate level in all test models.

CONCLUSION

In different height mucosa thicknesses, locator attachment models distributed the load to the other side of the implant and its surrounding tissue, whereas the ball attachment did not. Regardless of mucosal thickness and attachment type, the implant on the loading side was subjected to the highest stress concentration.

Evaluation of two interforaminal implants and implant-assisted removable dentures on stress distribution: an in vitro study

Objectives

In mandibular edentulism, the treatment option with a two-interforaminal implant-retained bridge and a removable partial denture is rarely evaluated in literature. The aim of this in vitro study was to evaluate the stress distribution of this treatment option by comparing it with traditional treatment options with interforaminal implants in the edentulous mandible.

Materials and Methods

Two interforaminal implants were placed in a formalin-fixed cadaver mandible, and overdentures with three different types of attachments were fabricated: (1) two ball attachments and an overdenture, (2) a Dolder bar and an overdenture, and (3) screw-retained two-implant inter-canine porcelain fused to a metal bridge and an implant-assisted removable denture (IARD) with precision attachments. Three biting conditions were generated for each denture type, and the strains were documented under vertical loading of 100 N.

Results

The calculated strain values from measured strains in all measurement sites and loading conditions for the screw-retained two-implant inter-canine porcelain fused to a metal bridge and a cast framework partial denture with precision attachments situation were lower than in the other scenarios (P<0.05).

Conclusion

Within the limitations of the present study, it can be concluded that an IARD may be a reasonable and valuable alternative to ball attachments or a bar in two interforaminal implants, especially when the patients prefer to be able to show their teeth even when they take out their removable dentures.

Effect of implant abutment connection designs, and implant diameters on screw loosening before and after cyclic loading: In-vitro study

AIMS

The purpose of this in-vitro study was to evaluate the screw loosening of two different forms of implant abutment connection designs, and two implant diameters by measuring removal torque value (RTV) before and after cyclic loading.

MATERIALS AND METHODS

Twenty implant fixtures were divided equally into 2 groups (N=10): group I fixture with conical hybrid connection (CH), and group II fixture with internal hex connection (IH). Each group was divided equally into two subgroups according to implant diameters: subgroup A (3.3mm), and subgroup B (4.2mm). Each fixture was vertically placed in the center of an acrylic resin block. The samples were fixed to the jig, and an implant abutment connected it with a 20 Ncm tightening torque. The samples were subjected to eccentric cyclic loading (at a distance of 5mm) away from center of abutment at 100,000 cycles. A digital torque gauge was used to evaluate screw loosening by measuring RTVs in (Ncm) before and after cyclic loading. The removal torque loss ratio before and after cyclic loading and the removal torque loss ratio between before and after cyclic loading were calculated and analyzed using the SPSS statistical analysis.

RESULTS

For GI the initial removal torque loss ratio measurement was (14.45±3.18) and decreased significantly after loading, it was (11.47±3.64). For GII the initial removal torque loss ratio measurement was (20.47±4.99) and increased significantly after loading, being (35.35±4.26). There is no significant effect upon screw loosening for two implant diameters.

CONCLUSION

Within the limitations of this study, the results suggested that conical hybrid connections showed a better screw stability than an internal hex connection. Therefore, the use of conical implants can be promoted as they have better screw stability compared to other systems.

Immediate Loading of Unsplinted Implant Retained Mandibular Overdenture: A Randomized Controlled Clinical Study

This clinical study aimed to clinically and radiographically compare the implant survival rate and peri-implant tissue response between immediate and delayed loading protocols for unsplinted implant retained mandibular overdentures. Twenty patients were enrolled to participate in this study. Each subject was randomly assigned to 1 of 2 treatment groups: test group patients' implants (n = 10), which were immediately loaded, and control group patients' implants (n = 10), which were conventionally loaded. Locator abutments were torqued to 15 Ncm at delivery. Attachments were picked up intraorally immediately after implant placement for the test group and at 3 months for the control group, and 3-lb retention inserts were placed. Marginal bone levels based on cone beam computed tomography fixed reference points were recorded at baseline and 12 months. Modified plaque index, gingival index, and implant stability quotients were recorded at baseline, 3 months, and 12 months. After 12 months, implant survival rate was 100% in both groups. Marginal bone levels, keratinized mucosa, modified plaque index, and gingival index were significantly different among the groups at 3- and 12-month intervals, whereas no significant differences were found in implant stability quotients between the groups. The fact that implant survival rate was 100% in both treatment groups suggests that, within the limitations of this study, immediate loading protocol for unsplinted implant retained mandibular complete overdenture is as predictable, safe, and successful as the delayed loading protocol. Implementing the immediate loading protocol for mandibular implant retained overdentures could shorten treatment time, which could lead to better patient's satisfaction.

Effects of interimplant distance and cyclic dislodgement on retention of LOCATOR and ball attachments: An in vitro study

STATEMENT OF PROBLEM

Evaluation of the long-term retentive behavior of overdenture attachments is necessary for successful treatment. Interimplant distance (IID) could affect the retention of these attachments.

PURPOSE

The purpose of this in vitro study was to assess the effects of IID and cyclic dislodgement on the retention of LOCATOR and ball attachments.

MATERIAL AND METHODS

Ball and LOCATOR attachments were connected to corresponding implant analogs. Metal housings were connected to each attachment. Thirty-six pairs of acrylic resin blocks were fabricated for 3 IIDs (19, 23, and 29 mm) and 2 attachments (n=6). Each pair consisted of 2 attachment assemblies parallel to each other with a specified IID. Overall, 1440 dislodgement cycles were applied by using a universal testing machine, and the maximum dislodging force was recorded after 0, 120, 360, 720, and 1440 cycles. Dislodging force data were analyzed by using repeated-measures 3-way analysis of variance, with the number of cycles as the within-subject factor for each specimen. Bonferroni-corrected Student t tests were used to resolve effects that were statistically significant. Moreover, dislodging force data were fit into an exponential decay model to determine the extent and rate of force decay for each attachment and IID studied.

RESULTS

The initial retention of LOCATOR attachments was significantly higher than that of ball attachments with IIDs of 23 and 29 mm, but no significant difference was noted with the 19-mm IID. After 1440 cycles, the retention was statistically similar with that of the 23-mm IID but was significantly higher for ball attachments with IIDs of 19 and 29 mm.

CONCLUSIONS

The IID is one of the factors that affect the retention of ball and LOCATOR attachments. The mean retention of both attachments was sufficient for all 3 IIDs at insertion and after 1440 cycles.