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.
Highlights
Treatment with conventional complete dentures has long been the treatment of choice in the oral rehabilitation of edentulous patients, these individuals have reported several complaints involving difficulties of adaptation, most of which have been associated with mandibular complete dentures and which include lack of retention and stability, chewing difficulties, low selfesteem, and reduced quality of life and satisfaction [1,2].Today, implant-supported mandibular overdentures retained by two implants associated with a maxillary complete denture have been proposed as the first choice of treatment for edentulous patients [3]
There was a significant difference (p
The effect of the number of cycles on retention force depended of the type of attachment system used (O-ring, Mini Ball, or Equator), As shown in Table 1, the three attachment systems differed during all of the cycle periods tested
Summary
Implant-supported mandibular overdentures retained by two implants associated with a maxillary complete denture have been proposed as the first choice of treatment for edentulous patients [3] This treatment seeks to provide better stability and retention of the mandibular complete denture, improving masticatory function of the patient and providing greater satisfaction, better oral health-related quality of life, and comfort [46]. The selection of the attachment system has typically been empirical and based largely on the clinician’s experience and preference [8,9] This choice may depend on the subjective retention characteristics of the attachment, not on scientific evidence [10,11]. Knowledge on the different attachment systems and an understanding of their mechanical properties (retention) and load distribution could help clinicians to select the proper attachment for each case [12]
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