Comparison of changes in retentive force of three stud attachments for implant overdentures.
OBJECTIVE
The aim of this study was to compare the changes in retentive force of stud attachments for implant overdentures by in vitro 2-year-wear simulation.


METHODS
Three commercially available attachment systems were investigated: Kerator blue, O-ring red, and EZ lock. Two implant fixtures were embedded in parallel in each custom base mounting. Five pairs of each attachment system were tested. A universal testing machine was used to measure the retentive force during 2500 insertion and removal cycles. Surface changes on the components were evaluated by scanning electron microscopy (SEM). A Kruskal-Wallis test, followed by Pairwise comparison, was used to compare the retentive force between the groups, and to determine groups that were significantly different (α<.05).


RESULTS
A comparison of the initial retentive force revealed the highest value for Kerator, followed by the O-ring and EZ lock attachments. However, no significant difference was detected between Kerator and O-ring (P>.05). After 2500 insertion and removal cycles, the highest retention loss was recorded for O-ring, and no significant difference between Kerator and EZ lock (P>.05). Also, Kerator showed the highest retentive force, followed by EZ lock and O-ring, after 2500 cycles (P<.05). Based on SEM analysis, the polymeric components in O-ring and Kerator were observed to exhibit surface wear and deformation.


CONCLUSIONS
After 2500 insertion and removal cycles, all attachments exhibited significant loss in retention. Mechanism of retention loss can only be partially explained by surface changes.
Department of Prosthodontics, School of Dentistry, Pusan National University, Yangsan, Republic of Korea.
Su-Min
SM
Kim
Department of Prosthodontics, School of Dentistry, Pusan National University, Yangsan, Republic of Korea.
Jae-Won
JW
Choi
Department of Prosthodontics, School of Dentistry, Pusan National University, Yangsan, Republic of Korea.
Young-Chan
YC
Jeon
Department of Prosthodontics, School of Dentistry, Pusan National University, Yangsan, Republic of Korea.
Chang-Mo
CM
Jeong
Department of Prosthodontics, School of Dentistry, Pusan National University, Yangsan, Republic of Korea.
Mi-Jung
MJ
Yun
Department of Prosthodontics, School of Dentistry, Pusan National University, Yangsan, Republic of Korea.
So-Hyoun
SH
Lee
Department of Prosthodontics, School of Dentistry, Pusan National University, Yangsan, Republic of Korea.
Jung-Bo
JB
Huh
Overdenture attachment; Resilient attachment; Retention; Surface wear