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 assessment of polyetheretherketone for an attachment component for an implant-retained overdenture.

STATEMENT OF PROBLEM: Frequent maintenance because of the limited lifetime of overdenture attachments with O-rings has led to the development of materials that might improve their functionality and longevity. However, testing of newly developed attachment materials is lacking. PURPOSE: The purpose of this in vitro study was to evaluate a newly developed attachment made of polyetheretherketone (PEEK) for an implant-retained overdenture. MATERIAL AND METHODS: Specimens of PEEK, polyacetal, and Teflon O-ring materials were prepared for analysis of roughness, surface hardness, and compressive strength. For the fatigue resistance test, new specimens based on acrylic resin were subjected to 2880 insertion and removal cycles. Compression and roughness data were compared with the Kruskal-Wallis and Dunn post hoc test; hardness data with ANOVA and t test; and fatigue and stereomicroscopy with ANOVA with repeated measures, t test, and Bonferroni adjustment (α=.05). RESULTS: Polyacetal had the lowest surface roughness (P=.038). There was a significant difference in hardness among the materials (P<.05). PEEK presented the highest compressive strength among the materials (P<.001). For the fatigue resistance, only polyacetal showed a difference between the initial time-point (P<.05) and subsequent time-points. Polyacetal had a higher fatigue resistance than Teflon (P<.001) and PEEK (P<.05). Regarding the internal deformation of the attachments, a significant difference was observed among the materials (P<.05). CONCLUSIONS: PEEK showed promising results regarding the physicomechanical properties necessary for use as an overdenture attachment when compared with other evaluated materials. In addition, the PEEK attachment showed results comparable to those in the control group (O-rings) in terms of retention.

Immediate Vacuum Formed Overdenture for a Pediatric Patient with Ectodermal Dysplasia.

Restoring the dental and facial esthetics in a growing patient with ectodermal dysplasia (ED) is fundamental to improve psychosocial issues, esthetics, and function. The purpose of this clinical report was to present a simple, fast, and cost-effective technique to re-establish a pleasant smile of an eight-year-old male patient with hypohydrotic ED. A vacuum-formed overdenture prosthesis is described, which is recommended as an immediate interim restorative treatment in the maxillary arch with excellent stability and retention.

Five-year clinical trial using three attachment systems for implant overdentures.

OBJECTIVE: The objective is to compare, in a prospective randomized clinical trial, three types of attachment systems for mandibular implant overdenture, focusing on costs, maintenance requirements and complications from baseline to the end of 5-year follow-up period. MATERIALS AND METHODS: Sixty-nine fully mandibular and fully/partially maxillary edentulous patients received two screw-type Straumann implants, in the mandibular canine region. New overdentures with three types of attachment systems were inserted according to an early-loading protocol: Group B (balls, divided into Subgroup B.1 - retentive anchor with gold matrix and Subgroup B.2 - retentive anchor with titanium matrix) (n = 23), Group M (magnets) (n = 23) and Group L (locator) (n = 23). RESULTS: The highest maintenance event number (195) was observed in Group B vs. 31 in Group L and 15 in Group M. Significantly more complications were recorded in Subgroup B.1 than in Subgroup B.2, Group M and Group L (P < 0.05). Group M registered the highest prosthetic success (82.6%) in the 5 years, followed by Group L (78.2%). Subgroup B.1 had the lowest success rate (50%). The magnet group recorded statistically significant higher costs, comparing with the other two groups (P < 0.05). CONCLUSIONS: The three attachment systems functioned well after 5 years. The magnets had a low maintenance requirement and high success rate, despite the relatively increased initial costs. Retentive anchor with titanium matrix and locator may be a better choice from a financial point of view, taking into consideration the initial low cost of the components and also the reduced number of complications.

Fixation of 5-unit implant-supported fixed partial dentures and resulting bone loading: a finite element assessment based on in vivo strain measurements.

PURPOSE: It is believed that implant-supported fixed partial dentures (FPDs) should display passive fit. The objective of this in vivo-based finite element analysis (FEA) was to quantify the magnitude of bone loading occurring on account of the fixation of cemented or screw-retained 5-unit superstructures. MATERIALS AND METHODS: Based on a patient situation with 3 implants, 4 different groups of restorations with 10 samples each were fabricated. Strain gauges on the pontics of the restorations were used for in vivo measurements. Using the values obtained, bone loading in 3-dimensional FE models was simulated as von Mises equivalent stress. RESULTS: The in vivo measured mean strain values ranged from 32 microm/m to 458 microm/m at the different sites. FEA revealed stresses between 5 and 30 MPa in the cortical area, while in trabecular bone values ranging from 2 MPa to 5 MPa were observed. Stress of a similar magnitude was found for axial implant loading with 200 N. DISCUSSION: Assuming that the axial loading of a single implant with 200 N is within the realm of the bone's adaptation ability, it would appear that the amount of stress resulting from the fixation of superstructures alone does not constitute a risk. CONCLUSIONS: The level of precision of fit which can be obtained in superstructure fabrication would appear to suffice to produce restorations that do not cause bone damage.

[The well-established Dalbo-Rotex-retainer and the newly developed Ticap-system. Low-cost anchorage possibilities in the removable prosthesis]. / Der altbewährte Dalbo-Rotex-Wurzelanker und das neu entwickelte Ticap-System. Kostengünstige Verankerungsmöglichkeiten in der abnembaren Prothetik.

Conventional retainers for removable prostheses are frequently used in the daily practice. Financial limits, physical and mental restrictions especially among elderly or disabled patients, and/or limited prognosis of abutment teeth may require simple and less expensive alternatives. For these indications the well-established Dalbo-Rotex-retainer and the newly developed Ticap-system are available. Both systems are options for the anchorage of removable prostheses. Their clinical use is presented; furthermore their advantages and restrictions are discussed.

Use of mandibular implant overdentures: treatment policy in prosthodontic specialist clinics in Sweden.

The aim was to examine the use of mandibular implant overdentures in Swedish prosthodontic specialist clinics. Questionnaires related to treatment with mandibular implant overdentures during 2001 were sent to the heads of the 30 prosthodontic specialist clinics of the Public Dental Health Service in Sweden. Completed questionnaires were received from 28 (93%). The number of treatments with mandibular implant overdentures varied much among the clinics (0 to 22). Seven clinics had not performed any such treatment, and the median number was 2. The number of fixed implant-supported prostheses was much higher (median value 17, range 4 to 100). The correlation between the number of implant overdentures and fixed implant-supported prostheses in edentulous mandibles was weak (r = 0.33; P = 0.10). The most common anchorage system was ball attachments on two unsplinted implants. The most common reason for the choice of the overdenture treatment was the reduced cost, whereas the patient's main wish to improve denture retention came next. The question whether the demand for implant overdentures had increased during the last few years, was answered with "no" by 19, with "yes" by 5 and with "don't know" by 4 clinics. All but one responded that their attitude to implant overdentures had not changed after the introduction of free pricing in Swedish dentistry. It can be concluded that compared to the rapidly increasing international use of mandibular implant overdentures, this treatment of edentulous patients is rare in Sweden, where fixed implant-supported prostheses still are predominant.