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Clin Oral Implants Res. 2009 Dec;20(12):1314-9. doi: 10.1111/j.1600-0501.2009.01742.x. Epub 2009 Aug 4.

An in vitro study of non-axial forces upon the retention of an O-ring attachment.

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1
Department of Dental Materials and Prosthodontics, Dental School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil. renata@forp.usp.br

Abstract

OBJECTIVE:

The purpose of this study was to evaluate the retention force of an O-ring attachment system in different inclinations to the ideal path of insertion, using devices to compensate angulations.

MATERIAL AND METHODS:

Two implants were inserted into an aluminum base, and ball attachments were screwed to implants. Cylinders with O-rings were placed on ball attachments and connected to the test device using positioners to compensate implant angulations (0 degrees , 7 degrees , and 14 degrees ). Plexiglass bases were used to simulate implant angulations. The base and the test device were positioned in a testing apparatus, which simulated insertion/removal of an overdenture. A total of 2900 cycles, simulating 2 years of overdenture use, were performed and 36 O-rings were tested. The force required for each cycle was recorded with computer software. Longitudinal sections of ball attachment-positioner-cylinder with O-rings of each angulation were obtained to analyze the relationship among them, and O-ring sections tested in each angulation were compared with an unused counterpart. A mixed linear model was used to analyze the data, and the comparison was performed by orthogonal contrasts (alpha=0.05).

RESULTS:

At 0 degrees , the retention force decreased significantly over time, and the retention force was significantly different in all comparisons, except from 12 to 18 months. When the implants were positioned at 7 degrees , the retention force was statistically different at 0 and 24 months. At 14 degrees , significant differences were found from 6 and 12 to 24 months.

CONCLUSIONS:

Within the limitations of this study, it was concluded that O-rings for implant/attachments perpendicular to the occlusal plane were adequately retentive over the first year and that the retentive capacity of O-ring was affected by implant inclinations despite the proposed positioners.

[Indexed for MEDLINE]

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