Implant Overdenture Attachment Analysis

AIM
To compare the retention force value alterations of four different types of implant overdenture attachments over various time intervals.
MATERIALS AND METHODS
28 cuboidal blocks were fabricated using autopolymerising acrylic resin. Four of these were used as master blocks, one for each group. Master blocks for Group A and B contained an implant analog with ball abutment, for Group C contained a single piece implant with ball abutment and for Group D contained an implant analog with Locator abutment. Six blocks for each group were used as prosthetic blocks, which included the overdenture attachment to be studied. Prosthetic blocks for Group A contained nylon cap - clear attachments, Group B contained nylon cap - pink attachments, Group C

The nylon cap and Locator attachments are made of plastic/nylon and O-ring attachments are made of silicone rubber. The high retention capability of the Locator system can be attributed to the dual retention characteristic of the Locator attachment system, which comprises of inner and outer aspect of the patrix, and titanium matrix linked to the implant. The mode of retention for these attachments is "frictional" and the "dimensional misfit between the slightly oversized nylon male insert and smaller diameter inner ring of the abutment".[42] The greater cross section of the locator abutment increases surface area available for frictional contact between its components. Furthermore, the cylindrical profile of the component provides supplementary retention as the retentive areas are adjacent to parallel surfaces. The nylon cap attachment is an analog to the ball abutment and engages it from the undercut, while the O-ring is a doughnut shaped attachment. According to Petropolous et al,[43] "the strain energy absorbed during insertion may be divided into elastic (recoverable) and plastic (permanent) components. If the deformation is elastic, no loss of retention is expected. If permanent deformation occurs, incomplete recovery occurs leading to rapid loss of retention." According to Craig,44 "a material that is momentarily submitted to stress below its yield strength returns to its original form without any internal or structural change. However, if this stress is repetitive as in a fatigue process, the material can suffer definitive