Assessing the role of Attachment implants on the retention and resistance of over-denture - in vitro

Aim: The aim of this investigation was to compare the retention and resistance of the
Nobel Biocare ball (NBS), Nobel Biocare Bar (NBB) and Strengold ERA red (SER)
attachments on an implant-tissue supported over denture model.
Materials and Methods: All different attachments were tested using two
permanently placed Nobel Biocare System implants on a test model that was attached
to a Zwick machine (Cross head speed 55mm/min). Each attachment had one part
embedded in a denture like housing the other part screwed into the implant.
Dislodging tensile forces were applied to the over denture in three dimentions
simulating the natural functions: vertical, oblique and anterior-posterior. Six separate
tests were conducted in three directions and two conditions at the beginning and after
100 times insertion attempts of the over denture with 5 samples of each attachment.
Dislodging force was measured at generation of the peak load (Maximum dislodging
force). A One way ANOVA test was employed followed by the Tukey’s test at 0.05
level of significance.
Results: Evaluating the collected data revealed that, SER attachment as being the
most retentive and resistance among the test groups, both at initial stage and after the
100 times of insertion and removal. This was while the NBS had the least retention
and resistance particularly in oblique situation. NBS and NBB showed the same
anterior-posterior resistance in initial stage of the test. All test groups represented a
large amount of retention loss after the insertion attempts. NBS showed a higher
anterior –posterior resistance than that of NBB after the process of several insertion/
removal.
Conclusion: A higher level of retention and resistance was seen in SER attachments
than that of others. This retention and resistance was however diminished by the time
and act of several insertion/ removal indicating the attrition effect.
Key Words: attachment, Implant, retention, resistance