The service life of implant-retained overdenture attachment systems

Retentive force and dislodgment time variations between three implant overdenture stud attachments in an acidic environment: An in-vitro pilot study

Introduction

This in-vitro study aimed to evaluate the retentive force and dislodgment time of three stud attachment systems used for mandibular two-implant overdentures by simulating insertion/removal cycles.

Materials and methods

From a simulation of a completely edentulous mandible with two parallel implants (Ø4.5 mm internal hex connection) (Zimmer Biomet, Warsaw, IN), 15 resin bases were fabricated and divided into three groups (n = 5 each): OT Equator (Rhein83, Bologna, IT), Locator (Zest Dental Solutions, Escondido, CA) and Locator R-Tx (Zest Dental Solutions, Escondido, CA). Pink inserts underwent 2000 cycles of thermocycling (SD MECHATRONIK GmbH, Feldkirchen-Westerham, Germany) and were soaked in citric acid for 24 days in an incubator. Each base underwent 2000 insertion/removal cycles on the Versa Test testing machine (Mecmesin Ltd., W. Sussex, UK) which was used to measure the retentive force and dislodgment time. The results were analyzed using ANOVA followed by the post-hoc Tukey test, Kruskal-Wallis test, and Pearson correlation coefficient test. A p-value of < 0.05 was considered statistically significant.

Results

The retentive force and dislodgment time of the three systems significantly decreased over the cycles (p < 0.05). The Locator R-Tx showed significantly greater retentive force ​​than did the other systems (p < 0.05), except for the last cycles wherein no significant difference was found with the OT Equator (p > 0.05). The OT Equator had the most stable retention over the cycles (p > 0.05; cycle 1500).

Conclusion

The three systems showed satisfactory retentive force ​​during the 2000 cycles. The Locator R-Tx demonstrated the best retention, while the OT Equator exhibited the most stable retention over time.

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.

Using an Attachment System with PEEK Matrices for Single-Implant Overdentures: In Vitro Retention Force

Single-implant overdentures (SIOs) represent a major biomechanical challenge in terms of prosthetic retention. The Novaloc attachment system has the potential to overcome those challenges when used for SIOs, due to the use of PEEK matrices. This study compared the retentive force of the Novaloc attachment to the traditional Locator system, before and after cyclic insertion–removal cycles. Three Novaloc matrices (white, yellow, and green, corresponding to low, medium, and high retention, respectively) and Locator (medium retention) were tested, totalling four groups. Retentive force was measured using an Imada force gauge before and after 1095 insertion–removal cycles, corresponding to a year of SIO wearing. Retention was tested with the implants angulated at 0, 10, and 20°. Data for the different groups, angles, and cycling periods were tested via linear regression analysis and two-way ANOVA (α = 0.05). Although the Locator system yielded higher retention forces in general, it lost a much higher percentage of retention with cycling. This trend was similar with the three angles, with forces being inversely proportional to the implant angulation. The authors conclude that Novaloc may provide more reliable retention for SIOs due to their higher resistance to insertion–removal cycling.

Retentive force of a conical crown with CAD/CAM-fabricated PEEK and zirconia secondary crowns on titanium implant abutments

This study aimed to evaluate the retentive force of polyetheretherketone (PEEK) and zirconia secondary crowns on ready-made titanium implant abutments (with height, diameter, and taper as 5.5 mm, 4.5 mm, and 6°, respectively) as the primary crown. PEEK, zirconia, and titanium secondary crowns were fabricated using a CAD/CAM system. Insertion and removal tests of secondary crowns on the primary crown were conducted for 2,000 cycles. The initial retentive forces recorded at the 100th cycle for PEEK, zirconia, and titanium were 13.0±7.9, 2.9±2.6, and 27.6±1.7 N, respectively. The retentive forces of PEEK and zirconia showed no significant difference among all cycles. However, the retentive force of the titanium used as a control decreased (20.3±2.8 N) significantly at the 2,000th cycle. Although the retentive force of PEEK was lower than that of titanium, it was within the range that can provide a suitable retentive force of 5 N for removable dental prostheses.

The Effect of Mini Dental Implant Number on Mandibular Overdenture Retention and Attachment Wear

Purpose

Evaluate the effect of different mini-implant numbers on overdenture retention and evaluate attachment wear following one year of simulated placement/removal. Material and Methods. Nine models simulating atrophic mandibles held 27 mini dental implants in three groups of 2, 3, and 4 mini-implants. A total of 1080 simulated placement/removal cycles were carried out, and a digital force gauge was used to measure the overdenture dislodgment force. The means of the retention forces were analyzed using SPSS with one-way ANOVA and post hoc (p < 0.05). The inner diameter of attachment inserts was evaluated using a light microscope before and after testing. A paired t-test was used to compare the mean of inner ring diameters (p < 0.05).

Results

The retention was significantly reduced regardless of the mini dental implant number, but the number affected overdenture retention. The placement of 4 mini dental implants provided higher retention and less reduction in retentiveness. However, no significant difference was found when 3 mini dental implants were compared to 2 mini dental implants (p = 0.21). Microscopic examination showed abrasion wear in all inserts following testing. However, the inserts of the 4 mini dental implants showed less wear than those used for 2 or 3 mini dental implants with p ≤ 0.001 and p ≤ 0.001, respectively.

Conclusion

Mini dental implant overdenture retention force and attachment wear could improve by increasing the mini dental implants to 4. However, there was no difference in retention force or attachment wear when 2 or 3 mini dental implant overdentures were compared.

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.

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.

Parameters Affecting the Retention Force of CAD/CAM Telescopic Crowns: A Focused Review of In Vitro Studies

Telescopic systems constructed using computer aided design and computer aided manufacture (CAD/CAM) can overcome many drawbacks associated with conventionally constructed ones. Since retention is considered the most important function of these retainers, this scoping review aimed to discuss and summarize the parameters that affect this function in CAD/CAM-manufactured telescopic crowns and to compare their retention force values with the recommended retention force. An electronic search was done in Pubmed and Google Scholar databases using different keyword combinations to find the related articles. Seventeen articles that follow the eligibility criteria for this review were selected and analyzed for detection of each of the tested parameters and their effect on retention force. The parameters tested in these articles were divided into parameters related to design, manufacturing, material type, and test condition. Regardless of the effect of these parameters, the retention force values recorded in most of the selected studies laid within or were higher than the recommended retention force (2.5-10 N), which indicated the need to design and set the combination of materials of telescopic systems according to oral biomechanics.

Effects of denture cleaning solutions on the retention of Hader bar clips

STATEMENT OF PROBLEM

The clinical performance of implant-retained overdentures (IODs) with plastic bar clips made of different materials in the same design and dimensions may vary according to the patient's daily home care procedures. However, information about the effects of denture cleaning solutions on the retention of Hader bar clips is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the retention of Hader bar clips made of different polymers after being soaked in denture cleaning solutions.

MATERIAL AND METHODS

Ninety Hader bar clips made of polyamide (PA, n=30), polytetrafluoroethylene (PTFE, n=30), and polyetherketoneketone (PEKK, n=30) materials were tested. Two multiunit abutments were screwed onto the implant analogs and embedded into an acrylic resin block in a standardized position. The digital scanning of the abutments was acquired, and the bar patrix of each material system milled from a cobalt-chromium (Co-Cr) alloy disk by using computer-aided design and computer-aided manufacturing (CAD-CAM). After the milled bar patrices were screwed onto abutments and the metal housings of the bar clips were embedded into acrylic resin blocks, they were connected passively at the same angulation to a universal testing machine. The initial retention values of all Hader bar clips were measured, and each material system was divided into 3 subgroups (n=10) before soaking in the cleaning solutions: distilled water (DW), 5% sodium hypochlorite (NaOCl), or sodium bicarbonate-sodium perborate (SBSP). Each material was soaked for the equivalent of 3 months of clinical use. The final retention values of each Hader bar clip were measured. The data were statistically analyzed by using a 2-way analysis of variance (ANOVA), the Tukey honestly significant difference (HSD) test, and the paired sample t test (α=.05).

RESULTS

The 2-way ANOVA showed that the denture cleaning solution, the clip material, and their interactions led to significantly different retention values (P<.001). A decrease was observed for the retention values of all test groups after soaking in the cleaning solutions (P<.05). No retention was observed for the PTFE clips after soaking in the 5% NaOCI solution.

CONCLUSIONS

The denture cleaning solutions negatively affected the retention of Hader bar clips, regardless of the type of solution and clip material. The 5% NaOCI solution not only decreased the retention of PTFE clips but also completely degraded it. It is recommended that 5% NaOCI solution be avoided for the daily care of IODs with PTFE clips.

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.

In Vitro Effects of Cyclic Dislodgement on Retentive Properties of Various Titanium-Based Dental Implant Overdentures Attachment System

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

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.

Retention Force and Wear Characteristics of three Attachment Systems after Dislodging Cycles

Abstract Several attachment systems for mandibular implant-supported overdentures are currently available and studies are required to understand their mechanical properties. The objective of this study was to evaluate the retention force and wear characteristics of three attachment systems in a simulation of the cyclic dislodging of implant-supported overdentures. Thirty samples were fabricated and divided into 3 groups: 1-O-ring; 2-Mini Ball; and 3-Equator. A mechanical fatigue test was applied to the specimens using a servo-hydraulic universal testing machine performing 5500 insertion/removal cycles (f=0.8 Hz), immersed in artificial saliva. Retention force values were obtained before and after 1500, 3000, and 5500 cycles using a speed of 1 mm/min and a load cell of 1 kN. One specimen from each group was randomly selected and analyzed by scanning electron microscopy. Two-way repeated measures ANOVA and the Bonferroni post hoc test were used for statistical analyses (α=0.05). The O-ring system remained stable during all periods tested and exhibited significantly lower retention force values than the Mini Ball and Equator systems. The Mini Ball system exhibited a significant increase in retention force after the mechanical test (baseline=21.04±3.29N; 5500 cycles=24.01±3.30N).The Equator system exhibited a significant decrease in retention force after each period tested, but the values were higher than the other systems. The type of attachment was found to influence retention force in different ways after mechanical tests. The Equator system exhibited the highest retention force values. The Mini Ball and Equator matrices produced deformation and wear on the surfaces without breakage of the polyamide rings.

In vitro retention capacity of two overdenture attachment systems: Locator® and Equator®

Background

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

Material and Methods

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

Results

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

Conclusions

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

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

Retentive characteristics of individual and prefabricated polyvinylsiloxane overdenture attachments: alternative treatment options for geriatric patients

OBJECTIVES

Stud attachments are often too adhesive and too susceptible to damage for use in geriatric patients, especially when implants are angulated. This study aimed to evaluate alternative anchoring systems comprising individual and prefabricated polyvinylsiloxane (PVS) attachments.

MATERIALS AND METHODS

A total of 182 specimens with individual PVS (IPVS) attachments (Shore hardness [SH] 25, SH50, SH65], prefabricated PVS (PPVS) attachments (SM green, yellow, and red), and Locator attachments (LR blue) were fabricated (n = 7 per group). Retention force was measured using the following parameters: insertion/removal (100, 200, 500, 1000, and 5000 cycles), thermal undulation (10,000 cycles at 5-55 °C; one implant per specimen), implant angulation (0°, 5°, and 10° convergence and divergence; two implants per specimen), and artificial saliva.

RESULTS

Insertion/removal and thermal undulation caused no changes in retention force in SM green and IPVS subgroups; conversely, LR blue, SM red, and SM yellow attachments exhibited significant decreases in retention force of up to 66% (all P ≤ 0.001). Implant angulation produced relevant changes in retention force only in LR blue attachments. Artificial saliva caused a general decrease in retention force.

CONCLUSIONS

Retention force of low-retentive PVS attachments proved to be comparatively immune to dislocation and thermal undulation, as well as to implant angulation up to 10°.

CLINICAL RELEVANCE

Low-retentive PVS attachments could be a treatment option if reduced denture retention is required and/or if angulated implants are in place. Clinical studies are necessary to evaluate the materials' durability under oral conditions.

Retention and wear behaviors of two implant overdenture stud-type attachments at different implant angulations

STATEMENT OF PROBLEM

Implant angulation should be considered when selecting an attachment. Some in vitro studies have investigated the relationship between implant angulation and changes in the retention force of the stud attachment, but few studies have evaluated the effect of cyclic loading and repeated cycles of insertion and removal on the stud attachment.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of implant angulation on the retentive characteristics of overdentures with 2 different stud attachments, an experimental system and O-rings in red and orange, after cyclic loading and repeated insertion and removal cycles.

MATERIAL AND METHODS

The canine region of a mandibular experimental model was fitted with 2 implant fixtures with 2 different stud attachment systems at implant angulations of 0, 15, or 30 degrees. A mastication simulator was used to simulate cyclic loading, and a universal testing machine was used to evaluate retentive force changes after repeated insertion and removal cycles. To simulate the numbers of mastication and insertion and removal cycles per annum, 400000 cyclic loadings and 1080 insertion and removal cycles were performed. Wear patterns and attachment surface deformations were evaluated by scanning electron microscopy. Data were analyzed using the Kruskal-Wallis test, Mann-Whitney U test with Bonferroni correction (α=.05/3=.017), and the paired-sample Student t test (α=.05).

RESULTS

When retentive forces before and after testing were compared, O-ring showed significant retention loss at all implant angulations (P<.001). In contrast, the experimental system showed little retention loss in the 0- and 15-degree models (P>.05), whereas the 30-degree model showed a significant increase in retentive force (P=.001). At all implant angulations, retention loss increased significantly for the orange O-ring, followed by the red O-ring, and the experimental system (P<.001). Scanning electron microscopy analysis showed more intense wear in the matrix than the patrix (abutment that matches to matrix) and more severe wear and deformation of the O-ring rubber matrix than of the experimental zirconia ball.

CONCLUSIONS

Upon completion of the experiment, wear and deformation were found for all attachment systems. Even when implants are not installed in parallel, the experimental system can be used without involving great loss of retention.

In vitro retention force measurement for three different attachment systems for implant-retained overdenture

AIM

The aim of this study is to compare the retention force of three different types of overdenture attachment systems used in implant-retained mandibular complete overdentures.

MATERIALS AND METHODS

Twenty-one similar acrylic resin blocks were prepared and divided into three study groups: Group A (snap attachment) - 10 specimens, Group B (locator attachment) - 1 specimen, and Group C (syncone attachment) - 10 specimens. A single rectangular heat cure acrylic resin block with two implant analogs 22 mm apart was used with all specimens. Each specimen was subjected to 5500 cycles of insertion and removal in the presence of artificial saliva, representing 5 years of usage. Retention was measured three times for each specimen using universal testing machine. Data were analyzed using one-way and two-way analysis of variance at 95% level of confidence.

RESULTS

Locator attachment group (Group B) showed the greatest retention level throughout the study, followed by snap attachment (Group A), and syncone attachment (Group C) showed the lowest retention level.

CONCLUSION

Regardless of the initial retention level of overdenture attachment, gradual loss of retention values is inevitable. However, the rate of retention loss in overdenture attachments is higher in types which comprised plastic parts within their components, rather than those totally made up of noble metals.

Comparison of changes in retentive force of three stud attachments for implant overdentures

PURPOSE

The aim of this study was to compare the changes in retentive force of stud attachments for implant overdentures by in vitro 2-year-wear simulation.

MATERIALS AND METHODS

Three commercially available attachment systems were investigated: Kerator blue, O-ring red, and EZ lock. Two implant fixtures were embedded in parallel in each custom base mounting. Five pairs of each attachment system were tested. A universal testing machine was used to measure the retentive force during 2500 insertion and removal cycles. Surface changes on the components were evaluated by scanning electron microscopy (SEM). A Kruskal-Wallis test, followed by Pairwise comparison, was used to compare the retentive force between the groups, and to determine groups that were significantly different (α<.05).

RESULTS

A comparison of the initial retentive force revealed the highest value for Kerator, followed by the O-ring and EZ lock attachments. However, no significant difference was detected between Kerator and O-ring (P>.05). After 2500 insertion and removal cycles, the highest retention loss was recorded for O-ring, and no significant difference between Kerator and EZ lock (P>.05). Also, Kerator showed the highest retentive force, followed by EZ lock and O-ring, after 2500 cycles (P<.05). Based on SEM analysis, the polymeric components in O-ring and Kerator were observed to exhibit surface wear and deformation.

CONCLUSION

After 2500 insertion and removal cycles, all attachments exhibited significant loss in retention. Mechanism of retention loss can only be partially explained by surface changes.

Biomaterial aspects: A key factor in the longevity of implant overdenture attachment systems

Background:

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

Purpose:

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

Materials and Methods:

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

Results:

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

Conclusion:

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

The influence of saliva pH value on the retention and durability of bar-clip attachments

PURPOSE

The aim of this study was to compare the durability and retention of 4 types of attachments placed over computer aided design/computer aided manufacturing (CAD/CAM) titanium bars when subjected to different pH conditions.

MATERIALS AND METHODS

Four commercially available attachments were investigated: Hader Yellow, Hader Red, Ackerman Gold and Ackerman Stainless Steel. These attachments and Ackerman CAD/CAM titanium bars were placed in 2 vessels containing different artificial saliva solutions (pH 7/pH 4) at 37℃ for one month to simulate corrosion conditions, and they were then subjected to mechanical testing (5400 cycles of insertion and removal).

RESULTS

The results revealed that there were significant differences in the average values of insertion/removal force due to the pH (F (1, 24)=9.207, P<.05) and the type of attachment (F (3, 24)=11.742, P<.05).

CONCLUSION

More acidic pH values were found to have a negative influence on the retention capacity of the attachments.

Experimental and computational investigation of Morse taper conometric system reliability for the definition of fixed connections between dental implants and prostheses

Nowadays, dental implantology is a reliable technique for treatment of partially and completely edentulous patients. The achievement of stable dentition is ensured by implant-supported fixed dental prostheses. Morse taper conometric system may provide fixed retention between implants and dental prostheses. The aim of this study was to investigate retentive performance and mechanical strength of a Morse taper conometric system used as implant-supported fixed dental prostheses retention. Experimental and finite element investigations were performed. Experimental tests were achieved on a specific abutment-coping system, accounting for both cemented and non-cemented situations. The results from the experimental activities were processed to identify the mechanical behavior of the coping-abutment interface. Finally, the achieved information was applied to develop reliable finite element models of different abutment-coping systems. The analyses were developed accounting for different geometrical conformations of the abutment-coping system, such as different taper angle. The results showed that activation process, occurred through a suitable insertion force, could provide retentive performances equal to a cemented system without compromising the mechanical functionality of the system. These findings suggest that Morse taper conometrical system can provide a fixed connection between implants and dental prostheses if proper insertion force is applied. Activation process does not compromise the mechanical functionality of the system.

Evaluation of retention forces and resistance to fatigue of attachment systems for overdentures: plastic and metal components

PURPOSE

To compare retention forces of 3 overdenture attachment systems with metal and plastic components.

MATERIALS AND METHODS

Four samples of each system evaluated (Ball-Attachment [metal]; O-Ring, and ERA [plastic]) were prepared and underwent fatigue and retention force in a universal testing machine. Maximum retention force (N) was measured at 6 time points (from 0 to 36 months-0.5 mm/min). Two-way analysis of variance and the Tukey test were used (α = 0.05).

RESULTS

The Ball-Attachment group showed the highest retention values, statistically greater than the other systems, without differences during the trial (42.75-44.75). The ERA group had intermediate values and a statistically significant decrease during the trial (20.75-14). The lowest retention forces were found for the O-Ring group (13.75-11.75), with no statistical differences during the trial.

CONCLUSION

Retention forces are significantly affected by abutment type because the metal retainer was more retentive than plastics, possibly providing better fixation of the prosthesis in position, and more difficult to remove. After 6 months of simulation, retentiveness of both plastic components was similar. There was no fracture of any component.

Long and short term management of implant-supported mandibular overdentures

Common problems with the long term clinical use of implant-supported mandibular overdentures (ISMDs) include fractures of dentures, bars and clips, and reactivation of clips. Many general dental practitioners (GDPs) are reticent to be involved in the maintenance of ISMDs, especially if they have not had any further training or are unfamiliar with implant components and systems. This article highlights the need for the training of GDPs in maintenance and management of ISMDs as an increasing number of edentulous patients are being provided with ISMDs, resulting in an increasing need for the maintenance of the prosthesis in the primary care setting at a possible cost to the patient.

CLINICAL RELEVANCE

Implant-supported overdentures are becoming a common treatment option for edentulous patients, however, they are not without their clinical challenges, many of which can be easily rectified in a primary care environment, such as general practice.

Hader bar and clip attachment retained mandibular complete denture

Bar and clip attachments significantly improve the level of satisfaction of denture-wearing patients by enhancing the retention and stability of the prosthesis. These attachments have been most commonly used for connecting the prosthesis to implants, but they can be effectively used to retain tooth-supported prosthesis as well. The primary functions of bar attachments are splinting the abutments together, even distribution of forces to the abutments and supporting areas, guiding the prosthesis into place, improving the retention, stability, support and comfort of the patient. The primary requirement for the use of bar attachments is the availability of sufficient vertical and buccolingual space for the proper placement of the bar, sleeves, teeth arrangement and sufficient thickness of acrylic denture base to minimise incidence of denture fracture in the area of bar assembly.

Stud attachments for the mandibular implant-retained overdentures: Prosthetic complications. A literature review

A plethora of attachment systems for mandibular two-implant overdentures is currently available often without evidence-based support. Technical aspects are now parameters considered when choosing the appropriate attachment. Despite the increasing use of the Locator attachments, studies regarding their properties remain scarce. Peer reviewed articles published in English up to 2011, were identified through a MEDLINE search (Pubmed and Elsevier) and a hand search of relevant textbooks and annual publications. Emphasis was made on the technical complications as well as the loss of retention related to the attachments in implant-retained overdentures, primarily the Locator attachment. The evaluation of the long-term outcome of implant overdentures and complications associated with different attachment systems may provide useful guidelines for the clinician in selecting the type of attachment system and overdenture design.

Wear of matrix overdenture attachments after one to eight years of clinical use

STATEMENT OF PROBLEM

Matrices of unsplinted attachment systems are generally reported to be the weak component of implant overdentures, often requiring frequent maintenance. Clinical wear results in reduced retention of the prosthesis, requiring activation or renewal of the matrix to restore the initial level of retention.

PURPOSE

The purpose of this retrospective study was to measure the wear of the matrix of a ball attachment after various periods of clinical wear.

MATERIAL AND METHODS

Seventy specimens of 3 groups of matrices of ball attachments that had been in use for mean periods of 12.3 months (1Y group, n=26), 39.0 months (3Y group, n=28) and 95.6 months (8Y group, n=16) were retrieved from 35 patients (2 specimens per patient) and measured on a coordinate measuring machine equipped with a touch trigger probe. Ten unused matrices were used as controls (CTRL group). The external and internal matrix diameters and deviations from circularity were measured. For the various time periods, the decreases in matrix thickness were calculated and compared with controls. Kruskal-Wallis 1-way ANOVA by ranks, followed by the Mann-Whitney post hoc tests, were conducted to test for differences in median values among groups (α =.05).

RESULTS

For the internal upper diameter of the matrices tested, the Kruskal-Wallis and Mann-Whitney tests revealed significant differences for the 3 groups compared to the controls. For group 1Y, a significant difference (P<.001) of the internal upper diameter was found compared to the CTRL group. Compared to the controls, the nonparametric analyses for groups 3Y and 8Y showed significant differences for the internal upper diameter (P<.001) and deviations from circularity (P<.001). For groups 1Y, 3Y and 8Y, matrix thickness losses were 07, 47 and 70 μm, respectively.

CONCLUSIONS

Within the limitations of this study, it was observed that one year of clinical wear had limited effect on the ball attachment matrices. Three to 8 years of clinical use resulted in a significant decrease of matrix thickness, especially at the tip of the retentive lamellae.

Retention force of plastic clips on implant bars: a randomized controlled trial

OBJECTIVES

Retention of overdentures is important for patients' satisfaction. The study tested whether the clinical performance of retentive clips made of poly-ether-ether-ketone (PEEK) is superior to those made of poly-oxy-methylene (POM).

METHODS

A total of 30 patients received complete dentures with round bars (SFI-Bar) on two implants in a chairside technique. Two types of clip matrices (PEEK/POM) were used in a split-mouth technique. Retention forces were measured separately for both materials at baseline when the dentures were inserted and after 1, 3 and 6 months. The measurement was performed extraorally and intraorally by using a measuring stylus equipped, respectively, with an opposing matrix or bar part. Simultaneously, at each point in time the patient and the dentist judged the retention either to be good, or to be too high or too low. Statistical analysis involved performance of global non-parametric testing of dependence of retention force on time and material was performed with Brunner-Langer model; non-parametric 95% confidence intervals (CIs) were calculated.

RESULTS

At baseline the median force for POM matrices was 6.89N (95% CI: 6.50-8.21) and for PEEK matrices 7.17N (95% CI: 6.97-7.93). After 6 months, the retention of POM decreased to 5.53N (95% CI: 4.81-7.00) and of PEEK to 6.42N (95% CI: 5.15-7.51). The retention force changed significantly over time (P = 0.004) without differences between POM and PEEK (P = 0.135). No significant alteration of the retention force over time was measured at the bar (P = 0.289). Retention was estimated to be good with 90% at baseline and with 80% after 6 months, equally by patients and dentist.

CONCLUSIONS

POM as well as PEEK material fulfills the requirements of retentive clips on round bars.

Influence of the lubricant and the alloy on the wear behaviour of attachments

OBJECTIVES

Wear of attachments leads to a loss of retention and reduces the function of overdentures. This study evaluated the retention force changes of an attachment system for overdentures. The influence of the lubricant and the alloy on wear constancy was examined.

METHODS

Cylindrical anchors of the Dalbo(®) -Z system were tested (Cendres+Métaux SA). Three groups of alloy-lubricant combinations were generated 1.Elitor(®) /NaCl-solution (EN) 2.Elitor(®) /Glandosane(®) aquadest. (EG) and 3.Valor(®) /Glandosane(®) /aquadest. (VG). Ten samples of each group were subjected to 10 000 insertion-separation cycles.

RESULTS

For the EN-group, this led to a large increase in retention force. The EG- and VG-group showed a constant decrease after an initial increase in retention force at the beginning of the wear simulation. The change of the alloy caused no statistically significant differences. The use of a more viscous lubricant reduced the retention force increase significantly.

CONCLUSIONS

The use of a lubricant which simulates clinical conditions is an absolute need for wear simulation because the retention force changes are influenced enormously. The change of the alloy at the Dalbo(®) -Z system did not influence the wear behaviour. As a slight decrease in retention force was recorded, it is useful for an attachment system to allow compensation with an adjustable matrix.