الفهرس 
ACKNOWLEDGMENTOnly 14 pages are availabe for public view
 |  | from | 154 |  |  |
| | | from | 154 | | |
Abstract
This in-vitro study was conducted to evaluate retentive force and surface wear of OTEquator
with smart box and Angled Positioner Attachment systems with different retentive
caps. It was done by measuring the retentive force using the universal testing machine and
measuring the surface wear by using stereo microscope.
Two identical replica of an average sized edentulous mandible were made using silicone
based model former in epoxy resin and a layer of 2.5-3 mm thickness was replaced by
mandibular mucosal tissue mimicking material.
Using 3D Printed surgical guide and surgical drill tools, two implants 4mm in width and
10mm in length were placed parallel to each other at the symphyseal area and the other two
implants were 4 mm in width and 14 mm in length placed at canine-1st premolar area distally
inclined with 25 degrees angulation in that replica following the all-on-four concept.
Sixteen heat cured acrylic resin overdenture bases were fabricated fitting the two
identical mandibular replica, 8 overdentures for each model; the occlusal rims surfaces were
parallel to the base of the replica. Denture bases attached to the implants in the mandibular
replica by two types of attachment systems (OT-Equator with smart box and Angled
Positioner).
Universal testing machine was used to measure the retentive force of both types of
attachment systems. To withdraw the overdenture, the crosshead speed of the universal testing
machine was set at 50 mm/min to mimic the dislodging speed of a prosthesis from the
residual alveolar ridge during mastication and up to an extension of 4 mm. Peak load to
dislodgement was recorded to determine the initial retentive force of each attachment system
with different retentive cap resiliency for each specimen, and their average recorded.
A cyclic tension-compression test in a vertical direction was performed by using a
custom-made cyclic loading machine that acted as a dental mastication simulator to simulate
the insertion and removal of the 16 overdentures. Each overdenture was subjected to 1000
cycles resembling the average number of insertion and removal cycles in 1 year based on an
average of 3 removal-insertion cycles/day.
Then wear patterns were observed under a stereo microscope and compared to a new
similar attachment to observe changes on the attachment surfaces after tests with different
retentive caps.