Effects ofin vitrocyclic dislodging on retentive force and removal torque of three overdenture attachment systems

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.

A Clinical and Radiographic 3 Years Retrospective Study for Two Types of Locator Retained Mandibular Implant Overdenture

INTRODUCTION

This retrospective study aimed to evaluate peri-implant marginal bone loss (MBL) and prosthetic complications between two types of locator attachments in two implant-supported mandibular overdentures.

MATERIAL AND METHOD

From the archived records, information about patients who had two implants inserted utilizing two different types of locator attachments into the interforaminal region between November 2019 and December 2023 was obtained. Overall, 60 patients (Total = 120 implants) from the archive records of the Prosthodontics Department, Faculty of Dentistry, Mansoura University, with ages ranging from 40 to 60 (mean age 50), were included in the study. Group I (control): Overall, 30 patients who would be delivered mandibular implant overdenture using conventional locator attachments. Group II (study): Overall, 30 patients who would be delivered mandibular implant overdenture using RTx locator attachments. After the placement of the mandibular overdenture (T0), 6 months (T6), 12 months (T12), and 3 years (T3) later, the marginal bone loss (MBL) was assessed. Prosthetic complications were evaluated for both groups 3 years after prosthetic delivery.

RESULT

A statistically significant increase (p = 0.000) was found in MBL scores at all observation times between both groups. Group II showed a statistical increase in MBL than Group I. For prosthetic complications, no significant difference was found between both groups. Group II showed more matrix wear than Group I however, it was not statistically significant (p = 0.60).

CONCLUSION

Within the limitation of this study, we can conclude the following: Both types of locator attachment (conventional and RTx locator) can be used clinically with no preference concerning the frequency of prosthetic complications. From the MBL perspective, conventional locators are more favorable than RTx locators.

Single mandibular implant study - impact on dietary habits after 5 years of observation in patients with immediate and delayed loading protocols

OBJECTIVES

Single midline implants in the edentulous mandible can be used to support existing complete dentures to improve patients' satisfaction and masticatory efficiency. The impact on patients' dietary habits and the influence of the loading protocol of the implants was the subject of this study.

MATERIALS AND METHODS

In this prospective randomized clinical trial, edentulous patients with existing complete dentures in both jaws were treated with a single midline implant in the mandible. In group A, the implants were loaded immediately, in group B the loading was delayed after three months. Patients were asked to report on their nutritional intake before implant placement and 12, 24 and 60 months after loading using a standardized two-part questionnaire.

RESULTS

Nutritional intake regarding the frequency of consumption of the requested food items did not change significantly during the 60-months study period, regardless of the loading protocol. In contrast, the second part of the questionnaire revealed that after 60 months, there was a significant decrease in avoidance of food, that had a coarse and hard texture in both groups. This significant decrease was observable in the group A in the first 12 and 24 months and in the group B after 60 months.

CONCLUSION

A change in the patients' dietary habits due to the insertion of a single midline implant in the mandible to support the existing complete denture cannot be observed, independently to the loading protocol.

CLINICAL RELEVANCE

Improving the chewing efficiency by single midline implants in the edentulous mandible does not lead to a change in dietary habits.

Retention of implant retained obturator using two implant placement configurations for maxillectomy cases: in-vitro study

BACKGROUND

Implant-retained obturators for maxillectomy cases have several advantages over traditional obturators but prosthetic design for specific conditions after maxillary resection has several challenges and the appropriate implant placement configuration is essential for improving retention and the stability of the implant-retained obturator.

OBJECTIVES

The present study aimed to assess the retention force of using linear and nonlinear implant placement configurations using ball and socket attachment in implant-retained obturators at the initial retention and after simulation of six months of use.

MATERIALS AND METHODS

Two identical epoxy resin maxillary models of a completely edentulous unilateral maxillary defect (Brown's class IIb) were used for implant placement, in the first model three implants were arranged with linear placement configuration, and in the second model three implants were arranged in nonlinear placement configuration. For proper sample sizing, 26 models and obturator were used. Two equal groups of obturators (13 for each group) were constructed, each with a different implant placement configuration. Both groups used the same attachment design (a non-splinted ball attachment). Using a cyclic loading machine that served as a dental insertion and removal simulator, each study group was subjected to 500 tension-compression cycles simulating 6 months of use. Using the universal testing machine, each obturator was removed at a speed of 50 mm/min for the crosshead. peak load to dislodgement was measured at the initial retention and after the simulations of six months of use. Data were analyzed using independent and paired t-tests while percent change was analyzed using the Mann Whitney U test.

RESULTS

There were a statistically significant differences in retention between the nonlinear implant placement configuration for Brown's class IIb maxillectomy and the linear implant placement configuration at initial retention evaluation with p-value of < 0.0001 and after simulation of six months of usage with p-value of < 0.0001 Also, after simulation of 6 months of use group I lose - 24.87 (10.16) % of its retention while group II lose - 17.49 (7.78) %.

CONCLUSIONS

Non-linear implant placement is more retentive at the initial retention and after simulation of six months of use than linear and loses less retention after usage.

Initial retention force of three attachment systems for implant retained-mandibular overdentures: An in vitro study

PURPOSE

To evaluate and compare the initial retention force of three resilient unsplinted attachment systems for implant-retained mandibular overdentures: two cylindrical attachment systems (Locator R-Tx® and Novaloc®), and one ball attachment system (Ball System).

MATERIALS AND METHODS

For each attachment system, initial retention is measured as the average of the maximal dislodging forces during 10 insertion-removal cycles. For the Ball System, three activation degrees of the matrix are included versus four and six color-coded retention devices for the Locator R-Tx® and the Novaloc®, respectively, to represent the complete regular retention devices panel. For each retention device or activation degree, eight samples are tested.

RESULTS

The initial retention range is similar between the Ball System (7.7 ± 3.4 N - 19.9 ± 4.6 N) and the Novaloc® (2.0 ± 0.5 N - 18.9 ± 1.4 N) and broader for the Locator R-Tx® (3.3 ± 5.0 N - 60.2 ± 6.0 N). In each attachment system, the initial retention of each retention device is significantly different from the others, except for the two most retentive Novaloc® ones. Retention devices were also classified according to their initial retention (low, medium, and maximum). In each retention group, the Novaloc® and the Ball System provided similar retention values lower than the Locator R-Tx®.

CONCLUSION

Most of the retention devices tested provided an initial retention force of over 5 N for all three attachment systems. The Locator R-Tx® had the most comprehensive range, and the Novaloc® seemed to provide the most reproducible values, unlike the Ball System due to the activation required by the operator.

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.

Retention loss and wear assessment of three attachment systems for implant retained-mandibular overdentures: An in vitro study

BACKGROUND

The stud-shaped attachment systems (AS) with different shape designs (ball, cylindrical, conical) and materials (metallic, plastic, or a combination of both) are commonly used to provide better retention and stability in implant-retained mandibular overdentures (IRMO).

PURPOSE

The purpose of the present study was to evaluate and compare the retention loss and the wear (patterns, location, material loss) of three resilient unsplinted AS: a well-established ball attachment system (BAS) and two more recent cylindrical attachment systems (CAS), Locator R-Tx® and Novaloc®.

MATERIALS AND METHODS

The implants, their corresponding abutments, the color-coded or position-coded retention devices (RD), the matrix metal housing were incorporated within CAD/CAM resin blocks and cyclically loaded with 19.6 N along the implant axis in a chewing machine to simulate 10,000 insertion-removal cycles (IRC). At cycle 10, 100, 1,000, 5,000, and 10,000, the retention force was measured using a universal testing machine. The wear was qualitatively examined using a binocular magnifier for both systems, and quantitatively assessed from micro-computed tomography acquisitions for CAS. Material loss exceeding 50 μm was considered significant.

RESULTS

The three AS showed different retentive behavior along time. All the Locator R-Tx® RD lost more than 50 % of their retention after 10,000 IRC. The retention of the Ball System slightly varied over time, the final retention loss in Bmed and Bmax groups being lower than 25 % of the initial retention. Wear was located at the tip of their gold RD and at the equator area of their ball abutment. For Locator R-Tx®, the more retentive the plastic RD, the greater its wear and retention loss. Only Novaloc® maintained a stable retention with even a slight tendency to increase and showed a negligible wear. Implant abutments of the CAS showed no significant wear.

CONCLUSION

After 10,000 IRC, corresponding to approximately 5-years clinical use, almost all RD provided retention force over 5 N, which could be sufficient to maintain satisfaction in most of the patients. The retention loss observed most prominently for the Locator R-Tx®, then for the Ball System, seemed to correlate with the wear observed on their RD. The practitioner may expect less RD maintenance with the Novaloc® stable retention overtime.

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.

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.

Novel CAD-CAM fabrication of a custom-made ball attachment retentive housing: an in-vitro study

PURPOSE

This study aims to evaluate the digitally designed ball attachment housing in its initial retentive force and after 2 years of simulated clinical use and to compare it with the regular nylon ball attachment housing.

MATERIALS AND METHODS

Twenty implants with their corresponding ball abutments (diameter 4.5 × 4.0 mm) were inserted in resin blocks. They were divided into two groups. In Group I, ten ball abutments each received their corresponding conventional attachment with nylon rings. In Group II, ten ball abutments received the novel CAD-CAM polyetheretherketone ball attachment housing. A universal testing machine was used to measure the retention force. The achieved maximum values of retention force were recorded at the beginning of the study (initial retention) and after 2 years of artificial ageing (2000 cycles of insertion and removal). Results were statistically analyzed using an independent sample T test.

RESULTS

The PEEK attachment housing showed high retention forces (25.12 ± 0.99 N) compared to the conventional attachment with a nylon ring (15.76 ± 0.93 N) in the initial dislodgement test. There was a statistically significant difference in mean retention at the initial retention test and after 2 years of stimulated usage between the two studied groups, p = 0.000.

CONCLUSIONS

Within the limitations of this study, the novel CAD-CAM-PEEK attachment showed high retention characteristics compared to the conventional attachment with nylon rings, initially and after simulated long-term use.

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.

Effect of Implant Positions and Angulations on Retentive Strength of 2-Implant Mandibular Overdentures: An In Vitro Study with the New 3D-Printed Simulation Method

Objectives. To evaluate the retentive strength of overdenture attachments in 2-implant mandibular overdenture (2IMO) with implants placed at different positions and angulations. Materials and Methods. Edentulous mandibular models were 3D-printed using CBCT images and Materialise Mimics software and the denture models using the intraoral scanner. Two standard implants were placed parallel at different positions from midline (5, 10, 15, and 20 mm) with 0-0 degree angulations and with different distal angulations (0–5, 0–10, 0–15, 5-5, 10-10, and 15-15 degrees) at 10±mm from midline representing 10 study groups. Low-profile male attachments were attached to the implants and the female pink attachments were picked up in the denture. A total of 4 simulated overdenture model sets for each of the 10 study groups were subjected to the universal testing machine thrice to measure a peak load (N) to disengage the attachments vertically. Data were analyzed using one-way ANOVA and Tukey’s post hoc test at 0.05 significance level. Results. Varying implant positions had a statistically significant effect on the retentive strengths of the attachments (F = 5.61, $P=0.002$ ). Peak load-to-dislodgement values (in increasing order) were 49.64 ± 8.27 N for 5 mm, 53.26 ± 11.48 N for 10 mm, 60.24 ± 12.31 N for 15 mm, and 64.80 ± 6.78 N for 20 mm groups. The retentive strength of the 20 mm group was significantly higher than 5 mm ( $P=0.003$ ) and 10 mm ( $P=0.03$ ) groups. Varying implant angulations had a significant effect on the retentive strengths of the attachments (F = 7.412, $P=0.000$ ). The peak load-to-dislodgement values (in increasing order) were 48.20 ± 15.59 N for 5-5 degrees, 53.26 ± 11.48 N for 0-0 degrees, 54.96 ± 8.25 N for 0–5 degrees, 57.71 ± 7.62 N for 10-10 degrees, 66.00 ± 17.54 N for 15-15 degrees, 66.18 ± 14.09 N for 0–10 degrees, and 77.38 ± 10.33 N for 0–15 degrees. Retentive strength of 0–15 degrees was significantly ( $P<0.05$ ) higher than those of 0-0, 0–5, 5-5, and 10-10 degrees and that of 5-5 degrees was significantly ( $P<0.05$ ) lower than those of 0–10, 0–15, and 15-15 groups. Conclusions. Retentive strength of the 2IMO increased with increase in distance of implants from midline and increased with increase in distal angulations.

Evaluation of Retention, Wear, and Maintenance of Attachment Systems for Single- or Two-Implant-Retained Mandibular Overdentures: A Systematic Review

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

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.

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.

Comparison of Two Low-Profile Prosthetic Retention System Interfaces: Preliminary Data of an In Vitro Study

In recent years, a major research goal of companies has been to create mechanical components suitable for rehabilitation that are safer and more reliable. Evaluating their biomechanical features could be a way to improve them. The purpose of this study was to evaluate the different biomechanical features of low-profile retentive systems (Rhein®). Two different attachment systems were tested: OT Equator® Smart Box and Locator® R-TX. Once a machine was created for the simulation of the connection and disconnection of the attacks in a combined manner, it was possible to evaluate these parameters over time. Attachments were mounted in two different configurations of the divergence angle: 10° and 50°. The drop retention force proved to be stable over time. The Locator® R-TX attachment experienced a more rapid decrement of the retention force than the OT Equator® Smart Box. Both tested systems experienced a high drop in retention; this drop tended to stabilize after 1.5 years of use, and it was correlated with the divergence angle. The OT Equator® Smart Box system underwent this loss of retention more gradually than the Locator® R-TX. This study demonstrates preliminary results from a bioengineering and biomechanical point of view, providing useful information for the continuous improvement of these devices and, therefore, for the quality of patients' oral health.

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.

Microbiological evaluation of LOCATOR® Legacy attachments: A cross-sectional clinical study

Objective

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

Materials and Methods

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

Results

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

Conclusions

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

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.

Clinical evaluation of inter-implant distance influence on the wear characteristics of low-profile stud attachments used in mandibular implant‑retained overdentures

Background

This study was aimed to evaluate the influence of inter-implant distance on the wear characteristics of low-profile stud attachments used in mandibular implant retained overdentures.

Material and Methods

Forty Completely edentulous participants aged between 50 - 70 years were enrolled in this study. Each patient received 2-implants by 2-stage submerged surgical protocol. Participants categorized into 4-groups. Group I: 19 mm inter-implant distance with Locator retained overdentures; Group II: 19 mm inter-implant distance with OT Equator retained overdentures; Group III: 25 mm inter-implant distance with Locator retained overdentures; Group IV: 25 mm inter-implant distance with OT Equator retained overdentures. The female housings of each attachment were picked up to the mandibular overdenture. 12 month later the male inserts were replaced by new one. The used retentive male inserts were examined by Stereomicroscopic.

Results

Stereomicroscopic examination revealed wear were detected on both inner surface and, the core of male inserts. Comparison between the unused and the used Locator and OT equator retentive male inserts at various inter-implant distance revealed highly significant wear changes between them at either 19 mm, or 25 mm inter-implant distance P1= .000, P2=.000 respectively.

Conclusions

After one year of implant overdenture clinical use; both locator and OT equator retentive male inserts revealed significant surface deformities and wear. Wear were more notable on both locator and OT equator retentive male inserts with 25 mm interimplant distance than with 19 mm interimplant distance. Key words:Inter-implant distance, attachments wear, locator retentive male inserts, OT equator retentive male inserts.

Prefabricated taper crowns for the retention of implant superstructures: Three-year results of a prospective clinical trial

STATEMENT OF PROBLEM

Nonrigid retainer systems for removable implant superstructures are associated with negative effects such as rocking and increased load on the denture base. Rigid retainer systems such as telescopic crowns reduce these negative effects, but their fabrication demands highly skilled dental technicians and is therefore expensive. Whether a protocol with prefabricated retainers will reduce production time is unclear.

PURPOSE

The purpose of this prospective clinical trial was to evaluate a prefabricated telescopic retainer and a treatment protocol including the intraoral luting of a framework.

MATERIAL AND METHODS

A total of 23 participants (15 women and 8 men with a mean age of 61.6 ±2.9 years) were included. After 3 dropouts, 21 removable dentures (9 mandibular and 12 maxillary) retained by 91 delayed loaded Ankylos implants were investigated. All implants were restored with prefabricated conically shaped abutments (SynCone-abutment). The prefabricated corresponding cone matrix was assembled intraorally into a metal frame with autopolymerizing resin. After a loading period of 3 years, a follow-up examination investigated the fit of the framework, the prosthetic aftercare, the technical failures, and the retention force. A questionnaire was used to evaluate participant satisfaction. In addition, laboratory fabrication time and costs were compared with those of individually fabricated restorations.

RESULTS

One mandibular implant was lost after 25 months (survival rate, 98.9%). The removable dentures showed no apparent rocking and minimal prosthetic maintenance during the 36-month trial. No dentures required relining. The retention force was scored as good in 17 participants and high (with 6 implants in the maxilla) and low (with 2 implants in the mandible) in 2 participants each. No technical failures occurred. An assessment of laboratory fabrication time and costs revealed reduced time and costs. Patient satisfaction was significantly increased (P<.001) over the entire observation time.

CONCLUSIONS

The SynCone retainer presented a time- and cost-efficient treatment option with sufficient long-term retention for removable dentures and high patient satisfaction. Mandibular prostheses restored with 2 implants had limited success.

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.

Effect of Implant Location on Palateless Complete Overdenture Retention: an In Vitro Study

Objectives

The purpose of this in vitro study was to evaluate effect of implant location on initial retention values of palateless complete overdentures retained by four o-rings at different inter-implant distances.

Material and Methods

Two standard acrylic models representing completely edentulous maxillary arches were used. Four single piece ball type implants were placed in each model. Models were divided into two groups according to the distance between anterior and posterior implants. Two canine implants with 32 mm inter-implant distance were placed in both models. In one model (G1), two posterior implants were placed in second premolar region away from canine implants by 14 mm on both sides, while in the other model (G2), the two posterior implants were placed in first molar region away from canine implants by 22 mm on both sides. Eighteen palateless complete overdentures were constructed for each model. Overdentures were retained by four o-rings. Initial axial (central), and para-axial (anterior, posterior, and lateral) retention values of overdentures were estimated and compared using a universal testing machine.

Results

Independent t-test revealed that implant location has a significant role in palateless complete overdenture retention with a level of significance set at P < 0.05.

Conclusions

For in vitro simulated palateless implant overdentures retained by four o-rings, increasing the inter-implant distance between anterior and posterior implants is favourable for a more retentive prosthesis.

Clinical performance of LOCATOR® attachments: A retrospective study with 1-8 years of follow-up

The use of LOCATOR® attachments in implant-supported removable dental prostheses (ISRDPs) has been evidenced with conflicting clinical behavior in literature. This retrospective study aimed to investigate the long-term clinical performance of LOCATOR® attachments by evaluating the frequency of the encountered mechanical complication events (MCEs) and the factors that play a role in attachment wear (AW). The study recruited participants with ISRDPs on LOCATOR® attachments. Clinical parameters, number of MCEs (attachment replacements, attachment loosenings, denture cap-related events, loss of retention and/or insert, and implant fractures), and AW were recorded. Nonparametric tests were applied for statistical analyses (𝛼=0.05). Baseline demographics for the recruited 47 participants (mean age: 72.0 ± 9.0 years) revealed an implant survival rate of 94.9% (mean observation period: 54.8 months), average peri-implant probing depths, bleeding on probing scores, and plaque scores of 1.80 ± 1.50 mm, 0.70 ± 0.90, and 0.81 ± 0.90, respectively. MCEs were directly influenced by the time in use (p < 0.001). The most frequently encountered MCEs were loss of retention (p < 0.001) and denture cap-related complications (p = 0.004). AW was found to be significantly higher in the maxilla than in the mandible (p = 0.028); in the maxilla, the vestibular (p = 0.005) and mesial (p = 0.01) aspects were the most common wear sites. Maxillary implant overdentures revealed more vestibular AW (p = 0.013). In prostheses supported by >3 implants, vestibular (p = 0.046) and mesial (p = 0.032) AW were common. Lingual AW (p = 0.021) was observed more frequently when the support was <3 implants. Loss of retention and AW are the most common complications encountered with LOCATOR® attachments. Therefore, a modification in the attachment design along with an amelioration of the attachment surface may help decrease the maintenance needs and further enhance its clinical performance.

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.

A comparative evaluation of fatigue resistance of two different implant overdenture stud attachments with two different denture base materials: An in vitro study

Introduction:

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

Aims and Objectives:

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

Materials and Methods:

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

Results:

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

Conclusion:

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

Effect of Interimplant Distance and Cyclic Loading on the Retention of Overdenture Attachments

AIM

The purpose of this in vitro study was to investigate the effect of interimplant distance and cyclic loading on the retention of two locator attachment systems.

MATERIALS AND METHODS

A total of 72 acrylic resin blocks were fabricated and divided into six groups of six pairs each. Locators of DIO and 3i implant systems were positioned on analogs in three different interimplant distances (19, 23, and 29 mm). The blocks were attached to a universal testing machine, and 1,440 dislodging cycles by the force of 136 N were applied. After 0, 120, 360, 720, and 1,440 cycles, the retention was recorded. Three-way analysis of variance (ANOVA) was used to test for differences in retention between the various combinations of the locator, interimplant distance, and cyclic loadings.

RESULTS

Interimplant distance was significantly associated with retention, independent of the locator system used, and dislodge-ment force cycles. Mean retention was significantly higher under the 3i system relative to the DIO system (p < 0.0001). This association varied with both interimplant distance (p > 0.0001) and dislodgement force (p < 0.0001) as well as across the various combinations of distance and cycle (p < 0.0001).

CONCLUSION

Interimplant distances could affect the initial retention of locator attachments. There was little difference in retention between distances of 23 and 29 mm across all cycles when both locator systems were combined. Distance of 23 mm was associated with superior retention in the DIO system. With regard to the speed of retention decrease, the 23 mm distance was associated with better performance.

CLINICAL SIGNIFICANCE

Interimplant distance could play a significant role in overdenture retention with locator attachments.

Effect of Simulated Mastication on the Retention of Locator Attachments for Implant-Supported Overdentures: An In Vitro Pilot Study

PURPOSE

Limited information is currently available relative to the effect of masticatory loads on the retentive properties of Locator attachments. The aims of this in vitro study were to assess and compare the effect of simulated mastication on the retention of white, pink, and blue Locator inserts for overdentures retained by 2 implants.

MATERIALS AND METHODS

Thirty specimens simulating a nonanatomic edentulous flat ridge with two implants and an overdenture were divided into 3 groups according to the color of the fitted insert: transparent clear group (n = 10), pink group (n = 10), and blue group (n = 10). Retention forces were measured in an axial direction initially and after 100,000 cycles of simulated masticatory loads. One-way ANOVA followed by Tukey's post hoc tests were used to compare retention values and percentage retention loss between the 3 groups with significance set at p = 0.05.

RESULTS

The 3 groups presented significant differences in retention at baseline (9.95 ± 1.91 N, 15.43 ± 4.08 N, and 41.73 ± 9.29 N for the blue, pink, and clear groups, respectively) and after simulated mastication (6.37 ± 2.64 N, 14.00 ± 3.89 N, 38.20 ± 5.11 N for the blue, pink, and clear groups, respectively). Within the same group, cyclic loading did not significantly affect retention in the clear and pink groups, while the blue inserts showed a significant retention loss (-37%) after loading.

CONCLUSIONS

The results suggest that short-term simulated mastication affects the extra-light blue inserts but not the more-retentive inserts.

Custom Cast Ball Attachments Used on Outdated Implants to Restore a Maxillary Implant-Supported Overdenture

The lack of compatible prosthetic components can be a complication during oral rehabilitation using outdated implants. The aim of the present clinical report was to describe an alternative technique for the fabrication of a maxillary implant-supported overdenture in a patient with 20-year-old dental implants using castable spherical patterns and ball attachments. The patient had been wearing a relined bar/clip overdenture in the mandible on 4 external-hexagon dental implants and a relined complete denture in the maxilla on 4 internal-hexagon implants due to abutment screw fracture inside of the implants, losing the attachment system. The remaining maxillary dental implants did not possess attachments compatible with current systems due to configuration changes by the manufacturer in the dental implant's platform and the components over time. Therefore, castable spherical patterns and cast ball attachments were used to fabricate a maxillary implant-supported overdenture. The mandible rehabilitation was performed using 4 osseointegrated dental implants with a fixed implant-supported prosthesis. The use of cast ball attachments on the maxillary dental implants avoided invasive procedures on the remaining implants. Considering the lack of available compatible prosthetic components for the osseointegrated implants, this technique was considered a viable and satisfactory treatment option.

Locator Versus Bar Attachment Effect on the Retention and Stability of Implant-Retained Maxillary Overdenture: An In Vitro Study

PURPOSE

To compare retention and stability of Locator and bar attachments for implant-retained maxillary overdentures.

MATERIALS AND METHODS

Four implants were inserted into a maxillary acrylic resin model in canines and second premolar areas. Experimental overdentures were connected to the implants with bar (group I) or Locator (group II) attachments. Locators were divided into 3 subgroups according the degree of retention of the patrix nylon insert: Locator blue (group IIa), Locator pink (group IIb), and Locator transparent (group IIc). Retention (vertical dislodging) and stability (lateral, anterior, posterior dislodging) forces (N) were measured at the start of the experiment (initial retention) and after 540 cycles of denture insertion and removal (final retention).

RESULTS

The highest initial and final stability was recorded with group IIc, followed by group IIb and group IIa, and the lowest retention and stability was noted with group I. For all groups, the highest final retention and stability forces were noted with vertical dislodging, followed by posterior dislodging, anterior dislodging, and lateral dislodging. The highest loss of retention and stability was recorded with group I, followed by group IIc, group IIb, and group IIa.

CONCLUSION

Locator attachments are recommended to retain maxillary overdentures over Dolder bar attachments, as Locator attachments were associated with high retention and stability after wear simulation with minimal retention loss.

Long-term clinical and prosthetic outcomes of soft liner and clip attachments for bar/implant overdentures: a randomised controlled clinical trial

Long-term clinical and prosthetic outcomes of soft liner attachments for bar/implant overdentures were not sufficiently investigated. The aim of this trial was to evaluate clinical and prosthetic outcomes of resilient liner and clip attachments for bar/implant-retained mandibular overdenture after 7 years. Thirty edentulous male participants received two implants in the canine areas of the mandible. Three months later, implants were splinted with a resilient bar. Mandibular overdentures were connected to the bars with either clip (CR group, n = 15) or resilient liner (RR group, n = 15) attachments. Plaque index (PI), gingival index (GI), probing depth (PD), vertical bone loss (VBL), horizontal bone loss (HBLO) and prosthetic complications (PCs) were evaluated at denture delivery (T0), 6 (T_6m ), 12 (T1), 24 (T2), 36 (T3), 48 (T4), 60 (T5), 72 (T6) and 84 (T7) months after insertion. PI and GI increased significantly with time for CR and decreased significantly for RR (P < 0·001). PD increased at T1 (CR) and T6 m (RR) and then decreased thereafter (P < 0·05). VBL increased significantly with time in both groups (P < 0·005). HBLO increased at T2 (CR) and T1 (RR) and then decreased thereafter. CR recorded significant higher PI, GI, PD, VBLO and HBLO compared to RR at all observation times (P < 0·042). The survival rates were 96·6% and 100% for CR and RR after 7 years. The most common PCs for CR and RR were clip wears and separation of the resilient liner from the denture base, respectively. Within the limitations of this study, resilient liner attachments are recommended for bar/implant-retained mandibular overdentures than clip attachments in terms of peri-implant tissue health and prosthetic complications after 7 years.

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.

An in vitro comparative study to evaluate the retention of different attachment systems used in implant-retained overdentures

Aim:

The aim of this in vitro study was to compare the change in the retentive force and removal torque of three attachment systems during simulation of insertion-removal cycles.

Methodology:

Edentulous mandibular models were made with heat-cured polymethyl methacrylate resin. Two implant replicas (CMI), of 3.75 mm diameter and 10 mm length, were placed in the intraforaminal region. Acrylic resin mandibular overdentures were fabricated and provision was made to receive three different overdenture attachment systems, prefabricated ball/o-ring attachment (Lifecare Biosystems, Thane, India), Hader bar and clip attachment (Sterngold, Attleboro, MA), and Locator^® implant overdenture attachment stud type (Zest Anchors LLC, USA). Using a universal testing machine, each of the models were subjected to 100 pulls each to dislodge the overdenture from the acrylic model, and the force values as indicated on the digital indicator were tabulated both before and after thermocycling (AT).

Statistical Analysis Used:

Statistical analysis comprised Kolmogorov–Smirnov test, Friedman test, and Wilcoxon signed ranks test.

Results:

The statistical model revealed a significantly different behavior of the attachment systems both before and AT. The ball/o-ring and bar attachments developed higher retentive force as compared to the locator attachment. The bar and clip attachment exhibited the highest peak as well as the highest mean retention force at the end of the study. The Locator^® attachment showed a decrease in retentive potential after an early peak.

Conclusions and Clinical Implications:

The ball/o-ring and bar and clip attachments exhibit higher retentive capacities than the Locator^® attachment over time.

Effect of abutment angulation in the retention and durability of three overdenture attachment systems: An in vitro study

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Long-term retention behaviour of resin matrix attachment systems for overdentures

OBJECTIVES

The purpose of this laboratory study was to evaluate the long-term retention behaviour of two resin matrix attachment systems for overdentures and the influence of the implant angulation.

METHODS

Sixteen titanium patrices of each attachment system were connected to their corresponding implant analogues and fixed in an auto curing resin either orthogonally (n=8) or 20° tilted (n=8). The corresponding matrices, one made from polyetherketoneketone (PEKK; CM LOC, Cendres+Métaux, Biel, Switzerland), one made from polyethylene (PE; Locator, Zest Anchors, Escondido, California, USA), were fixed in a stylised unilaterally removable dental prosthesis resulting in 4 groups with 8 specimens in each group. Overall, 30,000 joining and separating cycles of the matrix were performed in a chewing simulator. After each joining movement, the unilaterally removable dental prosthesis was loaded eccentrically with 100N at a distance of 12mm from the attachment to simulate clinical loading conditions. Retentive forces were measured during the test using force transducers. The statistical analysis was performed using Tukey-HSD.

RESULTS

Both attachment systems showed a significant decrease in retention over time, which occurred earlier in the tilted groups than in the orthogonal groups. After 5000-30,000 joining and separating cycles the PE matrix attachment provided significantly lower retention than the PEKK matrix attachment system.

CONCLUSION

Within the limitations of this investigation, the combination of a titanium patrix and a matrix made from polyetherketoneketone seems to be a promising material combination for long-term retention, also on tilted implants.

Influence of different lubricants on the retentive force of LOCATOR(®) attachments - an in vitro pilot study

OBJECTIVE

The aim of this in vitro pilot study was to evaluate the influence of an artificial saliva (AS) lubricant on the retentive force of a stud-type attachment (LOCATOR(®) ) for implant overdentures (IODs).

METHODS

Twenty custom-made models simulating a two-IOD with parallel implant situation were fabricated using LOCATOR(®) attachments. The in vitro testing was carried out with an Instron(®) universal testing machine for a total of 10,000 insertion-removal cycles, for each model, in two different aqueous test mediums (Group 1: 0.9% sodium chloride solution (NaCl), n = 10; Group 2: AS, n = 10). Changes in the mean retentive force (F) were plotted against the cycle numbers #10, #100, #1000, #5000, and #10,000. Mixed regression models were applied for statistical analyses.

RESULTS

A mixed regression (not considering interactions) predicted, compared to cycle #10, higher retentive forces at cycles #100 (P < 0.0001), #1000 (P = 0.017), similar forces at #5000 (P = 0.277), and lower forces at #10,000 (P = 0.012); there was no overall effect of the medium (P = 0.159). A second statistical model, employing the interaction term "cycle##medium", confirmed similarly the effect. Although the interaction term was significant at cycle #100 (p = 0.045), there was no significant difference between the two groups (P = 0.140).

CONCLUSION

In this in vitro pilot experiment, there was no difference in mean retentive forces of the LOCATOR(®) attachments when tested with either 0.9% NaCl or a Glandosane(®) -like artificial saliva lubricant. A larger scale study may still confirm the superiority of either lubricant for quasiclinical bench experiments.

Wear, microleakage and plastic deformation of an implant-supported chair-side bar system

PURPOSE

This in-vitro study was designed to evaluate retention forces, microleakage and plastic deformation of a prefabricated 2-implant bar attachment system (SFI-Bar, Cendres+Métaux, Switzerland).

MATERIALS AND METHODS

Two SFI implant-adapters were torqued with 35 Ncm into two implant analogues. Before the tube bars were finally sealed, the inner cavity of the tube bar was filled with liquid red dye to evaluate microleakage. As tube bar sealing agents three different materials were used (AGC Cem (AGC, resin based), Cervitec Plus (CP; varnish) and Gapseal (GS; silicone based). Four groups with eight specimens each were tested (GS, GS+AGC, AGC, CP). For cyclic loading, the attachment system was assembled parallel to the female counterparts in a chewing simulator. The mean retention forces of the initial and final ten cycles were statistically evaluated (ANOVA, α≤.05).

RESULTS

All groups showed a significant loss of retention forces. Their means differed between 30-39 N initially and 22-28 N after 50,000 loading cycles. No significant statistical differences could be found between the groups at the beginning (P=.224), at the end (P=.257) or between the loss of retention forces (P=.288). Microleakage occurred initially only in some groups but after 10,000 loading cycles all groups exhibited microleakage.

CONCLUSION

Long-term retention forces of the SFI-Bar remained above 20 N which can be considered clinically sufficient. The sealing agents in this study are not suitable to prevent microleakage.

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.