Kim et al [209] ,used universal testing machine to compared the changes in retentive force of three commercially available attachment systems (Kerator blue, O-ring red, and EZ lock). The crosshead speed for the simulation was set at 60 mm/min. The lower mounting was seated on the fixed part of this machine, while the upper mounting was attached to the operation part. The specimen was placed in a position such that the force could be applied in a perpendicular direction, verifying the accurate placing of the upper mounting onto the lower mounting. The mountings were subjected to 2500 cycles of insertion and removal .The retentive force of each attachment system was measured 3 times ,at baseline and the end …show more content…
For linear (axial) dislodgements, implant part of attachment was secured to abutment model embedded in acrylic resin block that was glued to the table of the universal testing machine by epoxy resin while denture component of attachment was embedded in acrylic resin in a metal ring that was secured to the load cell of the testing machine by means of auto-polymerizing resin. For rotational dislodgements (anterior, lateral, posterior), overdentures were fabricated with four hooks attached to canines and second molars. Hooks were used to dislodge the overdenture away from its model. Maximum retentive force was recorded in …show more content…
A specific machine was designed to measure the retentive force of the attachments over the cycles applied, which was constructed at the Laboratory of Optics and Experimental Mechanics at the Faculty of Engineering, University of Porto. The main constituents of the device constructed were a motor with electronic speed control, a load cell (Futek® LSB 300, with S configuration - Advanced Sensor Technology, Inc. Irvine, California, USA) and a USB Futek® system connected to a computer . The two acrylic blocks, one with implants (jaw simulator) and the other one with the respective connection system (denture simulator) were coupled to this measurement system. The speed of insertion/disinsertion was 0.5